Abstracts of the 2013 AAPM Spring Clinical Meeting

s of the 2013 AAPM sPring clinicAl Meeting


Purpose
To identify whether geometrical similarity between a preplan and postimplant plan is necessary and/or sufficient for a good quality implant?

Methods
A unique cohort of 94 prostate seed implant patients was analyzed. For each patient, an ultrasound (US) preimplant and two CT postimplant (day 0 and day 30) studies were available. Measures for similarity were created and computed using feature vectors based on two classes of moments: first, invariant to rotation and translation, the second polar-radius moments invariant to rotation, translation, and scaling. Both similarity measures were calibrated using controlled perturbations (random and systematic) of seed positions and contours in different size implants, thus producing meaningful numerical threshold values used in the clinical analysis.

Results
When similarity is based on moments invariant to translation and rotation only, both seeds and contours exhibit a remarkable lack of similarity when pre-and postimplant plans are compared, with contours faring slightly better than seeds. When scaling invariance is added, resemblance between both implants and contours improved dramatically. When comparing postimplant plans at day 0 and day 30, apart from minor seed migration, the only change in the geometry of the implant should be due to resolution of prostate swelling and should be well describe by scaling, and this is clearly shown by the 83% (78 patients out of 94) similarity. Interestingly, there is no correlation between seed similarity and contours similarity, nor does D90 or D90 ratios correlate with seed or contours similarity in any of the comparisons.

Conclusion
In the setting of preplanned prostate seed implants using preloaded needles as delivery method, based on our data we conclude that similarity between pre-and postimplant plan does not correlate with either D90 or analogous similarity metrics for prostate contours, thus questioning the utility of creating 'optimal' preplans.

Purpose
To evaluate radiofrequency (RF) shield (Accusorb, Axonics, Inc. USA) for prospective use during 1.5T and 3.0T MRI examinations of patients with implanted metallic devices.

Methods
To assess attenuation of RF field, a standard 60 × 132 cm blanket (Accusorb, Axonics, Inc., USA) was wrapped around an acrylic tube and positioned at the center of a clinical 1.5T and 3.0 T MRI scanners (GE, Signa Excite). Single RF pulses were executed in 1 sec intervals at a constant power output and an RF probe, consisting of two orthogonal single-loop coils and a shorted coaxial cable (to account for offset voltage), was moved along the z-axis at 2 cm increments. Induced voltages were measured using an oscilloscope. Measurements were repeated without the RF shield for comparison. RF shield effects on RF-induced heating was evaluated using fluoroptic thermometers attached to ends of three parallel 40 cm straight copper wires submerged 20 cm apart inside the ASTM head-and-torso phantom ( Fig. 1(b)). Temperature history during execution of high SAR RF pulse sequence was recorded with and without RF shield around the phantom. The heating of the RF shield itself was measured by 5 fluoroptic thermometers placed at various positions on the surface of the shield.

Results
At 1.5T, the RF attenuation inside the RF shield increased from 5 dB near the edges to more than 10 dB at 9 cm from the edges, exceeding 30 dB at the center of the shield. At 3.0T, the RF attenuation reached 30 dB at the center of the shield. This attenuation was sufficient to reduce wire heating below levels detectable by fluoroptic thermometry. A measurable amount of heating of the shield was observed, which varied depending on position, but was less than 1.3°C.

Conclusion
The RF attenuation from the shield and the resulting reduced RF heating of metallic wires are significant and merit further evaluation.

PO-BPC-Exhibit Hall-08
investigation of a Technique for eliminating of Chemical Shift Artifacts with T1-Weighted FlAiR images at 3.0T in Thoracic Spine imaging examination Purpose The goal of this study is to assess the effect of chemical shift artifacts and fat suppression between contrast-enhanced T1-weighted fast spin-echo (FSE) sequence with fat suppression and contrast-enhanced T1-weighted fluid attenuated inversion recovery (FLAIR) sequence with fat suppression in magnetic resonance imaging (MRI) of the thoracic spine at 3.0T.

Purpose
To evaluate the accuracy of six-dimensional (6D) patient position detection using an in-house developed software based on a pair of orthogonal kV images taken using the on-board-imager (OBI) of a Varian Truebeam linear accelerator.

Methods
An in-house software was developed to detect the 6D position (lateral, longitudinal, vertical, pitch, row, yaw) of a patient on the treatment couch by performing 2D-3D image registration between a pair of orthogonal OBI kV images and the planning CT of the patient. A 6D simulation phantom designed by Ngar et.al. (2012) was used for the evaluation of the accuracy of 6D position detection of the software developed. The phantom was scanned using a CT simulator with its 6D shift set to zero. The phantom was then placed on the couch of a Truebeam linac. 20 sets of randomly generated known nonzero 6D shift with magnitudes within 20 mm and 4° were applied to the phantom. A pair of orthogonal OBI kV images was taken at OBI angles 45° and 315°, respectively, for each set of 6D shifts. The CT and the OBI images were imported into the in-house developed software for 6D position detection. The detection error was obtained by subtracting the actual shift from the software detected shift.

Results
The detection error of the 6D positions of the 20 sets of nonzero 6D shifts of the phantom detected were found to be all within 1 mm and 1°. The mean translation detection error and mean rotation detection error were 0.68 mm and 0.56°, respectively.

Conclusion
With the help of a proper image registration software, a Truebeam linear accelerator was able to perform 6D patient position detection with an accuracy of < 1 mm and < 1° using an orthogonal OBI kV image pair.

Purpose
To quantify the impact on dose to patients and personnel in the cardiac cath lab as a result of increasing the dose per frame for cine acquisition from 0.17 to 0.24 microGy/frame at the request of a physician.

Methods
Reports containing the dose area product (DAP) and reference air kerma (Ka,r) for patients who underwent left heart catheterization (LHC, n = 184) and right and left heart catheterization (RLHC, n = 100) procedures on a biplane Siemens Artis Zee were collected. Dose metrics from procedures performed before and after the protocol change were compared. Occupational dose reports were also analyzed.

Results
After the protocol change, the DAP and Ka,r increased by 3% and 4%, respectively, for LHC. These changes were not significant (p = 0.881, 0.851). The DAP and Ka,r for RLHC increased significantly by 59% and 64% (p < 0.001 for both). These increases were greater than expected based on the change made to the protocol. A review of fluoroscopy time (FT) data revealed that FT for LHC was the same before and after the change, while FT for RLHC increased significantly (35%, p = 0.008). Occupational dose data were of limited utility because of inconsistent use of radiation badges.

Conclusions
Patient dose metrics increased for RLHC procedures but did not increase for LHC procedures after increasing the dose per frame for cine. The constancy of LHC dose metrics may have resulted from a reduction in the number of cine runs acquired owing to improved image quality after the change. The increase in FT for RLHC indicated that another factor was affecting dose metrics, perhaps related to the skill of physicians or the complexity of cases; this is under investigation. It was not possible to assess the impact on occupational dose owing to inconsistent use of radiation badges.

Purpose
To outline a commissioning procedure for a HDR brachytherapy intracavitary applicator.

Method and Materials
The described procedure is applied to Nucletrons multicatheter cylinder set with an intravaginal tube and three different intrauterine tandems. The applicators were taken apart and their dimensions were compared to the manufacturer specifications. The index length was measured for all the catheters. All applicators where CT scanned with IU3 markers placed in the central and two outer catheters on opposite sides of the applicator. Applicator sizes on the CT scans were verified. Measurements between the first dummy source and the outer edge of the applicator were performed. Treatment plans for all cylinder and tube/tandem combinations were performed. The plans consisted of a single (first) dwell position in one peripheral catheter and in the tube/tandem. The plans were delivered and autoradiographs taken with a XV film. Prior to delivery, films were marked such that the cylinder and tube/tandem positions and dimensions can be visualized after film processing.

Results
The index length was measured for all the catheters -the central catheter measured 150 cm, while the outer catheters measured 129.3 cm (per vendor specifications). Cylinder integrity was visually verified in the TPS. The measured autoradiograph distances between the source positions and the cylinder/tube/tandem walls matched the measured distances between the dummy sources and the cylinder/tube/tandem walls in the TPS.

Conclusion
A simple procedure for HDR brachytherapy applicator commissioning was presented. Verification of the applicators integrity was verified. Coincidence between geometric and dosimetric properties was validated.

Methods
The CTDI body phantom is suspended on the CT gantry shroud with its bottom slightly above the table so that the phantom remains stationary as the table moves during an image acquisition. The phantom is suspended by two Lucite bars with adjustable brackets attached to the bottom of the phantom. On a given wall or barrier a fast response hand held scintillation meter is utilized to scan the barrier and determine the area where the highest radiation level occurs. The location is marked with tape. The long CT scan time permitted by suspending the phantom allows one to survey a large barrier area during one scan. Subsequently an exposure rate reading is made at the location with a sensitive ionization survey meter. The readings are normalized to estimate weekly radiation levels. Shielding design Workload was 6,400 mA-min/wk at 140 kVp. Survey technique was 140 kVp, 100 mA, and 20 sec.

Results
The readings one foot from the walls, doors, and control window ranged from 0.5 to 5.5 mR/ hr. The associated normalized readings for uncontrolled areas ranged from 0.07 to 1.2 mR/wk. The controlled area normalized readings ranged from 1.5 to 4.5 mR/wk.

Conclusions
The CT environmental radiation survey was done in a relatively short time (less than two hrs) and was done for a worst case scenario (i.e., body CTDI phantom, and a busy workload at 140 kVp); and for this worst case scenario, the normalized readings are well below regulatory limits for both controlled and uncontrolled areas.
Equipment discussed in this presentation is commercially available from CIRS or at one time was available from Victoreen.

Purpose
To evaluate IMRT QA plans using three different measurement methods.

Methods
Three IMRT QA techniques were compared: 1) 2D dose distributions acquired by 2D diode array (MapCHECK2, Sun Nuclear) processed with MapCHECK software; 2) EPID acquired fluences processed in Dosimetry Check (Standard Imaging); and 3) film dose measurements processed by RIT (Radiological Imaging Technology). The IMRT/VMAT plans used in this study included head and neck, prostate, chest, pelvis. The acceptance criteria for the gamma analysis used to evaluate the QA results are 3% dose difference and 3 mm distance to agreement for 90% for all points in the plane or volume being compared. The cases that were chosen for the analysis initially provided less than the desired gamma analysis results using Dosimetry Check (DC). Additionally, each software analysis tool was used to evaluate the three different detectors, 2D diode array, EPID, and film for the same plan.

Results
For the cases studied, MapCHECK QA analyses passed with at least 95% of points analyzed having gamma less than 1. In all but one case, RIT QA analyses passed with 90% of points analyzed having gamma less than 1.

Conclusion
IMRT QA analysis based on the planar dose comparison (i.e., MAPCHECK and RIT) provide higher passing rates than DC, which uses volumetric dose comparison (e.g., in the PTV) computed from fluence reconstructed from an EPID projected onto the patient 3D dataset. Results to date demonstrate the following: 1. Of the 3 detector types there was a higher passing rate for film for small field plans. For lower gradient plans, EPID ranked second and 2D Diode array ranked last. 2. For routine plans, MapCHECK is the tool of choice. 3. For complex plans, Dosimetry Check with EPID or film is the desired IMRT QA tool.

A Hsu, * E Mok
Stanford Cancer Center, Stanford, CA

Purpose
During acceptance testing of the high definition MLC (HDMLC) on a Varian TrueBeam STx machine, unusual characteristics were noted in its mechanical capability. We present some of those findings and discuss their clinical impact.

Methods
Picket Fence tests were run on both a Varian TrueBeam STx linac with an HD MLC and a Varian Clinac 21EX with a Millennium 120 MLC (Varian Medical Systems, Palo Alto, CA). Images were acquired with both EDR2 film and portal imaging (EPID).

Results
The Picket Fence result on a Millennium MLC shows the typical repeating pattern of gaps (dark due to exposure) and pickets (lighter due to the MLC blocking). For the HDMLC, the some of the gaps are much lighter than the pickets. This was observed in both EDR2 film and EPID imaging. There also appears to be nonuniformity in the gaps over the width of the carriage and depending on which MLCs, the small 0.25 cm leaves versus the larger 0.5 cm leaves were being moved. The vendor was contacted and additional testing was done. One hypothesis is that this behavior may be due to the intrinsic backlash of the MLC and is magnified by leaf curvature and the fact that the leaf gap for the TrueBeam is smaller than that for the Millennium MLC. It is also thought that leaf over travel plays an effect. Discussions with the vendor yielded the additional information regarding software controls of the offset of the HDMLC.

Conclusion
The HDMLC on a TrueBeam is characteristically different than a Millennium MLC on a Clinac 21Ex. Reasons for this include hardware differences of the MLCs and software corrections that are handled by the TrueBeam. However, of primary clinical interest will be how these differences across the field profiles affect dosimetry and the modeling of the leaf gap in the planning system.

Purpose
Optimization of dose distribution for different vaginal cylinders of HDR brachytherapy using different optimization methods, namely iterative, geometric and equal time.

Methods
Four different vaginal cylinders with diameters ranging from 2.6 to 4 cm is selected and dose reference points on the surface of the cylinders have been defined to optimize a dose of 6 Gy for a treatment length of 6 cm. Three optimization methods available in the TPS have been used to calculate the dose distribution. Apex points at the tip of the dome of the applicator and along the curvature of the dome was defined as dose reference points (DRP), and optimization was repeated with these points included. Comparison has been made between the dose distribution obtained with and without these apex points.

Results
Whenever we specify apex points as dose reference points, the minimum and maximum variation of dose with respect to the mean dose is higher than the variations compared to calculations made when apex points are not specified. When apex points are defined, the treatment volume increased by 8% and area only by 2% in case of 3 cm diameter cylinder. Treatment volume increases by 14% and area increases by 2% as observed in case of 3.5 cm diameter cylinder, when apex points are included in optimization. But with 4 cm diameter cylinder both the treatment volume and area increases by 9%.

Conclusion
The dose reference points to be defined at the apex of the cylinder to deliver adequate dose at the dome of the cylinder. Even through the variation in doses between apex points and points along the cylinder is maximum, adequate dose is delivered at the vault thereby reducing the frequency of recurrences in these types of treatments.

SA-A-Salon EF-01
Are There Roadblocks in the Way to Regulatory or legislative Progress? Small fields on the order of few millimeters are now being used in specialized radiation treatments such as intensity-modulated radiation therapy (IMRT), VAT, stereotactic radiosurgery (SRS), CyberKnife, and Gamma Knife. Small-field dosimetry is challenging due to finite source size, lack of electronic equilibrium, size of detectors, changes in energy spectrum with associated dosimetric parameters, and stopping power ratio. Poor understanding of dosimetry has lead to many errors and wrong patient treatments. Source size is dependent on the design of the accelerator and could be obstructed by the collimating system with decreasing field sizes. Electronic equilibrium is a phenomenon associated with the range of secondary particles and hence dependent on the beam energy, spectrum, and the composition of the medium (homogeneous vs. inhomogeneous). This talk will elaborate on safety concerns in advanced treatment techniques. It will also provide current understanding of the small-field dosimetry and give insight of the new IAEA/AAPM noncomplainant dosimetry (1) IPEM Report 103 (2) and AAPM Task Group Report 155. (3) Dosimetric criteria as stated in TG-120 (4) will be explored. Explanation of the difficulties and possible solutions to accurately measure dose in small fields with various techniques (ion chamber, diode, diamond, TLD, films (radiographic and GAFCHROMIC), MOSFET, bang gel, and Monte Carlo) will be elaborated. Correction factors that have been published will be presented and the consequences in accuracy for patient care will be discussed. The American College of Radiology Computed Tomography Quality Control Manual was published on 12/1/2012. This manual, which must be followed by facilities accredited by the ACR, describes the roles of radiologists, technologists, and medical physicists. It specifies quality control tests to be performed by technologists and medical physicists. This presentation will describe the QC manual, highlighting responsibilities of the team members. The required technologist and medical physicist tests will be described. Further developments around the QC Manual and the CT Accreditation Program will also be discussed. Historically, two CT dose indexes, CTDIvol and Dose Length Product (DLP), have been used to quantify the delivery of radiation dose to standardized phantoms by the CT scanner during a clinical examination. Too many radiologists, technologists, and even some medical physicists do not realize that neither dose index is a reasonable estimation of the patient's radiation dose during the examination. The Size-Specific Dose Index (SSDE) was recently developed by AAPM Task Group 204 to address this need for all size patients, from the smallest child to the largest adult. This lecture will begin by defining CTDIvol, DLP, and Effective Dose (E Dose), and then explore why none of these dose estimates are reasonable estimates of patient dose. SSDE will be defined and explained based on the task group's published report. Sample calculations of estimated patient doses based on SSDE will be provided. Useful clinical applications of SSDE will be explored, such as dose reporting in the patient's medical record, eliminating confusion about CT doses from dissimilar CT scanners, and first estimates of organ doses from SSDE calculations. A method using SSDE will be explained that allows the consulting medical physicist to develop appropriate CT radiographic techniques for any CT scanner in any department, from the smallest pediatric patients to the largest bariatric adults. The presentation will conclude with a description of challenges and solutions associated with effectively using the scanner's Automatic Exposure Control feature during pediatric imaging. AAPM Task Group 71 has defined the nomenclature and methodology for performing monitor unit (MU) calculations for photon and electron beams. Calculations within this protocol are made using the dose per MU under normalization conditions that is determined for each user's beams. For both photon and electron beams, this normalized dose per MU and associated dosimetric functions are determined using flat, water phantom data. The requirement of an independent verification of the monitor units calculated to deliver the prescribed dose to a patient has been a mainstay of radiation oncology quality assurance. However, in a modern clinic using CT/MR/PET simulation, computerized 3D treatment planning, heterogeneity corrections, and complex calculation algorithms such as convolution/superposition and Monte Carlo, the purpose of and methodology for the MU verification have come into question. In addition, since the verification is often performed using a simpler geometrical model and calculation algorithm than the primary calculation, guidelines are needed to help the physicist set clinically reasonable action levels for agreement. The AAPM Task Group 114 report reevaluates the purpose and methods of the "independent second check" for monitor unit calculations for non-IMRT radiation treatment in light of the complexities of modern day treatment planning.
The report provides recommendations on how to perform verification of MU calculations in a modern clinic, and on the establishment and implementation of action levels for agreement between primary calculations and verification.
learning objectives 1. Understand the current-recommended nomenclature, methodology, and measurements required to perform MU calculations within the TG71 protocol. 2. Know the components of a good monitor unit verification program. 3. Be able to apply the action level guidelines for agreement between primary and verification monitor unit calculations presented in the TG114 report.

M Martin
Therapy Physics, Inc., Gardena, CA The performance of the 11 required physics tests on a Stereotactic Breast Biopsy (SBB) System as required for accreditation by the American College of Radiology (ACR) will be covered in this presentation covering systems both with and without Automatic Exposure Control Systems for both prone biopsy tables and add-on SBB units for digital FFDM units. Image quality, expected values for half-value-layer (HVL), and patient doses for each matrix size available on SBB systems will be discussed. Clinical advantages/disadvantages of both types of systems will be covered relative to approach methods and areas available for sampling. The importance of testing the location of the biopsy needle or tissue sampling device for reproducibility and accuracy will be discussed relative to various phantoms that may be used to verify this location accuracy. Quality control (QC) tests to be performed by the mammography technologist will be covered in addition to the physics required tests. Requirements for training and education of the staff (physician, physicist, and technologist) so as to achieve accreditation by the ACR will be reviewed now that there is a requirement for SBB units to be accredited for breast imaging centers in order to obtain the ACR designation of a Breast Imaging Center of Excellence.
learning objectives 1. Attendees will be aware of the required physics tests to be performed annually and for acceptance of Stereotactic Breast Biopsy (SBB) System. 2. Attendees will be aware of the expected values of half-value layer and patient doses for SBB systems for common matrix sizes available on these units. 3. Attendees will be aware of the requirements for personnel performing SBB exams or physics evaluations in both Continuing Education and Continuing Experience for accreditation by the American College of Radiology. 4. Attendees will be aware of the required quality control tests to be performed by both the technologist and physicist on SBB units.

SU-A-Salon BCD-02
Establishing a New Breast-Specific Gamma Imaging (BSGi) Program: Roles of the Medical Physicist

Texas Health Presbyterian Hospital Dallas, Dallas, TX
Breast-Specific Gamma Imaging (BSGI) is a molecular breast imaging (MBI) procedure using a high-resolution and small field-of-view gamma camera. In addition to breast-specific imaging, the camera may be used for general nuclear medicine procedures. This presentation will update medical physicists of their responsibilities for supporting this system, including a review of the technology and clinical advantages, regulatory aspects for radioactive materials use, acceptance and quality control testing procedures, and how to obtain accreditation.
learning objectives 1. Review Breast-Specific Gamma Imaging (BSGI) technology and clinical advantages. 2. Understand radioactive materials licensing issues and training for staff and physicians.
3. Learn about medical physicist acceptance testing and quality control procedures. 4. Understand the process to receive accreditation. This session will cover three aspects of external beam therapy, focusing on quality assurance.

Foundations of Radiation Physics: external Beam Radiation Therapy Quality Assurance
1. TG-142: Quality assurance of medical accelerators.
The first section will review the principles of conducting QA for linear accelerators and discuss topics related to the execution of QA tasks, such as measurement parameters, measurement method, frequencies, tolerances, actions, documentation, measurement tools, staff, and effort. Examples of TG-142 QA implementation in a specific institution will be illustrated. Limitations of TG-142 and challenges will be discussed, as well. The second section will provide a technological review of flattening filter-free beams. It will also cover acceptance testing, commissioning, and periodic quality assurance for these beams. Finally, clinical applications and limitations of flattening filter-free beams will be highlighted. The third section will discuss acceptance testing and commissioning for VMAT. It will also address routine quality assurance procedures for VMAT, including machine-specific and patient-specific QA. Finally, it will discuss issues relating to VMAT implementation in a clinical environment, including identifying when VMAT may improve efficiency, as well as limitations and cautions in treatment planning and the delivery process when VMAT technology is utilized.

learning objectives
Understand the principle and content of TG-142, as well as a strategy and methodology of 1.
implementing the recommendations in this report.
Understand the limitations of TG 142.

2.
Understand the techniques and challenges of commissioning and maintaining flattening 3.
filter-free beams. Understand the process of implementing a VMAT program.

4.
Understand the clinical strengths and weaknesses of FFF and VMAT techniques.

Phoenix, AZ
This lecture is for the purpose of introducing the audience to digital breast tomosynthesis: the advantages of this technology, how images are obtained and reconstructed, how it has changed daily mammography practice, and radiation dose issues. We will also be introducing C View, which is currently under FDA review. Examples will be shown of 2D vs. 3D mammograms, demonstrating marked improvement in cancer detection. I do lecture on behalf of Hologic, but stipends for these lectures are paid to JC Lincoln Health Foundation, and I personally receive no money for these services. There are no known conflicts of interest.

University Michigan, Ann Arbor, MI
Tomosynthesis is a quasi 3D tomographic X-ray imaging method whereby a set of slices are reconstructed from a series of projection images acquired over a limited angle. Techniques using film as the detector were invented in the 1930s and application to the breast using digital detectors (digital breast tomosynthesis (DBT)) began in the 1990s. A wide variety of DBT systems presently exist, but only one system has been approved by the FDA for clinical use, to date. The current DBT systems will be reviewed, emphasizing the major design and operational differences. Image quality in DBT depends upon many factors including the acquisition geometry (total tomographic angle and angle increments), the accuracy of the geometric parameters used in reconstruction, X-ray tube motion during the exposures, and the reconstruction method. These and other factors will be discussed. Several types of artifacts in reconstructed DBT images will also be described. Finally, new applications such as contrast-enhanced DBT and dual-modality DBT will be examined.

learning objectives
Understand the basic theory of tomosynthesis image generation (the shift and add principle).

1.
Understand the effects of different imaging geometries (e.g., narrow tomographic angle vs.

2.
wide tomographic angle) on the perception of masses, microcalcifications, and contrast-detail test objects in DBT images. Understand the origins of common tomosynthesis artifacts.

R Morin
Mayo Clinic, Jacksonville, FL This presentation will discuss the aspects of the American Board of Radiology, Maintenance of Certification (MOC) process. In addition, the new process of continuous certification will be explained and clarified, including the ramifications of proper and timely completion of each part of MOC.

learning objectives
Review the American Board of Medical Specialties MOC process.

1.
Review the ABR MOC process.

2.
Review the specifics for Medical Physics MOC.

UAB Medical Center, Birmingham, AL
Currently, a common initiative in many fields is quality improvement. This endeavor is especially prominent in the medical community with concerns of patient safety and reduction of medical errors. As part of its certification oversight, the American Board of Medical Specialties (ABMS) has made QI one of the four sections of its Maintenance of Certification (MOC) process. This is particularly relevant to those medical physicists with time limited ABR certificates or for other ABR Diplomates voluntarily enrolled in the MOC program. One of the key aspects of The ABR expectation for Practice Quality Improvement (PQI), Part IV of the ABR MOC program, is that Diplomates provide evidence of an ongoing program of improvement of practice, either as an individual or within the system the individual is employed. For physicists, this may seem somewhat nebulous due to the many duties and responsibilities for quality in the clinical realm. For diagnostic physicists, this may seem even more undefined, especially for consultants. As a beginning dialogue related to PQI, suggestions for projects appropriate for medical physicists are presented. Another method for fulfillment of the PQI section is participation in society based PQI programs. Such programs are under development within AAPM and formulations of a program for physicists is presented.

learning objectives
At the conclusion of the presentation, an individual will: Gain knowledge of the basic aspects of PQI as regards to project types, basic ingredients 1.
of projects.
Learn about examples of projects for demonstration of PQI for medical physicists.

2.
Learn about the developments of society-based program for PQI for Physicists within the 3. AAPM.

Anatomy of a Professional liability Case
J Masten

Purpose
To introduce the meeting participants to the basic terminology and structure of medical negligence litigation. This talk will deal in depth with the tools which lawyers use to shape the case, the stage at which a particular tool is available, and the reasons behind a particular approach.

Methods
Actual case law will be used to illustrate the various legal concepts. Secondary legal sources will be introduced, as well as an extensive handout to point the way for further study.

Conclusions
Session participants should come away with not only an understanding of the language of litigation, but also a basic appreciation of the strategy in civil litigation procedure and its significance to the outcome of a trial.

D Jordan
University Hospitals Case Medical Center, Cleveland, OH The risks of financial harm to medical physicists due to professional liability are complex and often difficult to determine clearly. This presentation introduces the terminology and concepts of professional liability as it relates to the practice of clinical medical physics. Physicists will learn about situations that would lead to claims for financial damages under professional liability. The terminology of professional liability insurance will be introduced, enabling physicists to understand how insurance works and to determine the adequacy of a particular product for their individual needs. An approach to determining the need for coverage, as well as the amount of coverage, will be discussed.

learning objectives
Identify risks and liabilities arising from the practice of medical physics. 1.
Explain the role of professional liability insurance in a medical physicist's risk management.

2.
Understand terms and conditions typically encountered in liability insurance policies.

3.
Determine the amount and type of coverage needed to protect personal assets from uncovered 4.
or inadequately covered risks. Image-guidance radiation therapy (IGRT) systems are now widely available and implemented for routine clinical use in many clinics, in large part due to their tight integration with medical linear accelerators and treatment planning systems (TPS). Increased geometric precision and accuracy are now widely achievable in radiotherapy delivery because users can correct patient translations and rotations immediately prior to administration of radiotherapy by registering IGRT 'images of the day' to those initially used for treatment planning. Furthermore, comparison of successive daily IGRT images can help to quantify changes of internal anatomy throughout the course of therapy. However, introducing image guidance within busy radiation therapy clinics requires thoughtful commissioning and quality control (QC) protocols, and judicious modification of existing radiation therapy processes and protocols. While the uses of such novel systems will continue to evolve, their performance must be diligently maintained at the highest level, as they will be relied upon to insure accuracy in the treatment delivery process.

QA of Treatment Guidance Systems
In fact, such systems may be used to justify PTV margin reduction, thus further emphasizing the need for accuracy and precision through careful QC. There are two key features of IGRT systems that require particular attention: geometric accuracy and image quality. First, as a separate modality, the chosen IGRT system possesses its own reference origin and coordinate system, which in some cases may not be physically coincident with that of the megavoltage treatment beam or the medical linear accelerator isocenter. Therefore, the geometric relationship between the IGRT dataset and the megavoltage treatment beam must be established and monitored to ensure adequate localization, coincidence, orientation, and scaling. Second, image quality ultimately determines the ability of the IGRT system to consistently produce images capable of localizing the structures of interest, through either manual or automatic registration. Careful and continual monitoring of image quality must be performed to ensure consistent and accurate image guidance results. Details of a QC program for various IGRT solutions will be highlighted based on the following reports: TG147: Non-Radiographic Systems for Localization, TG154: Ultrasound Guidance Systems for External Beam Radiotherapy for Prostate Cancer, TG179: External Beam Image Guidance using CT-based Technologies.

learning objectives
To present IGRT technologies covered by the referenced Task Groups and major consider-1.
ations for their uses.
To describe principles for quality control of IGRT systems.

2.
To characterize and discuss the impact of IGRT on quality and safety of radiation therapy.

3.
Jean-Pierre Bissonnette has a commercial interest with Modus Medical.

P Platt
American College of Radiology, Reston, VA learning objectives The presentation will enable participants the opportunity to acquaint themselves with the rules under the Mammography Quality Standards Act (MQSA) governing mammography facilities and accrediting bodies (AB) as it applies to digital breast tomosynthesis (DBT). Additionally, an update will be provided on the ACR's Breast Imaging Center of Excellence Designation. The participants will be provided an overview of the ACR accreditation / MQSA certification process to: Understand the difference between accreditation and certification under the Mammography 1.
Quality Standards Act (MQSA); to include the role of the accrediting body, MQSA, the facility, and the annual MQSA inspection. Understand the accreditation process for a facility to start performing mammography as a 2.
new facility, or accredited facility adding a new DBT unit(s). Provide an overview of the MQSA Certificate Extension Program for DBT.

3.
Understand the medical physicist role as a member of the mammography team in providing 4.
guidance to the facility both during and after the annual survey. Provide guidance on where to go for assistance.

5.
Provide an overview of the ACR Breast Imaging Centers of Excellence.

Conclusion
Course participants should demonstrate an understanding of the basic principles of accreditation and certification under MQSA, to include the units that have an accrediting body and those units that fall under the MQSA Certificate Extension Program; to include common pitfalls during the application process and where to go for assistance. Additionally, participants will be able to demonstrate an understanding of the ACR's Breast Imaging Centers of Excellence designation.

UT MD Anderson Cancer Center, Houston, TX
Breast tomosynthesis was approved for use in screening for breast cancer in February 2011. Many tomosynthesis ready systems were installed across the country in preparation for this approval and those systems are being upgraded to perform Digital Breast Tomosynthesis (DBT). There is evidence that DBT is helping reduce recall rates while increasing cancer detection rates. (1,2,3) Due to this evidence, many new systems are also being installed. Facilities that are implementing a breast tomosynthesis program need to be aware that there are many hurdles that need to be overcome before tomosynthesis studies can be performed. The purpose of this lecture is to give the medical physicist the knowledge needed to help those facilities that are going to perform DBT deal with facility design issues, image storage requirements, choice of PACs, and review of the studies. This will include a review of DICOM for DBT, shielding requirements for DBT suites, and choice of review stations to help facilities transition smoothly form reading of 2D studies to reading of combined 2D and 3D studies.

learning objectives
Understand shielding requirements for a breast tomosynthesis suite.

1.
Be able to make recommendations to facility managers on PACs and review station require-2.
ments for breast tomosynthesis.
Be able to help facility managers with implementation of breast tomosynthesis at their 3. facility.

MonDAY, MARCH 18
THeRAPY SYMPoSiUM -SAM SAlon eF advanCes in BRaChytheRaPy dose CalCulations Recent advances in dose calculation algorithms for brachytherapy will have profound impact on how the end users will be required to integrate the necessary new information into the treatment planning system (TPS), commission a TPS that integrate model-based dose calculation algorithms (MBDCA) and dose reporting requirements. Until recently, all clinical TPS followed the well-known TG-43 dose calculation protocol. It is now possible for medical physics to take into account the complete geometry of a treatment (i.e., finite patient boundary (breast, superficial application)) and the heterogeneous tissue composition and any nonwater applicators, shields or other devices. The recently-published AAPM TG-186 report discusses important issues for clinical implementation of these algorithms. We will review the motivation leading to TG-186 work, and present in a clinically oriented fashion the key point of TG-186 recommendations. In particular, specific examples on how to perform the commissioning process will be presented. A proposed commissioning flowchart will be discussed, guiding the audience through the clinical process, with pitfalls identified to minimize likelihood for errors.

learning objectives
Identify key clinical applications needing advanced dose calculation in brachytherapy.

1.
Provide an overview of the alternatives to TG43.

2.
Explain in practical terms the recommendations of TG186.

3.
Identify relevant commissioning processes for safe clinical integration.

4.
Provide practical clinical examples using a commercially available system.

5.
Luc Beaulieu holds a research agreement with Elekta/Nucletron regarding advances dose calculation algorithms.
Luc Beaulieu and Firas Mourtada are members of an AAPM sponsor Working Group (WG) on model-based brachytherapy dose calculation. This WG is working closely with all brachytherapy treatment planning system vendors.

Riverview, FL
Given the multitude of manufacturers that produce magnetic resonance scanners, it is challenging for the MRI physicist/MRI scientist to maintain a working knowledge of every system and its idiosyncrasies. Each vendor, magnet, and software package has its own limitations. Knowing which is a true limitation of the system and what constitutes a genuine artifact or problem can save time in the troubleshooting process. Additionally, understanding the ACR MRI Accreditation phantom, its tests and failures, can provide insight into the overall performance of an MRI scanner. Data collected on more than one thousand scanners established certain general trends. This presentation is a compilation of the experience gained from the testing and problem-solving of virtually every make and manufacturer in MRI today. The intent of this lecture is to better equip the MRI Physicist/ MRI Scientist to efficiently troubleshoot issues with each type of MR imaging system. In 2008, the Medicare Improvement for Patients and Providers Act (MIPPA) was signed into US public law. Amongst its many provisions, the new law required that all providers of CT, MRI, breast MRI, nuclear medicine and PET examinations that bill under part B of the Medicare Physician Fee Schedule be accredited by January 1, 2012 with noncompliance resulting in the loss of Medicare reimbursement for these services. Since that time, this requirement has been adopted by at least one major private insurance provider. The insistence of accreditation in return for payment by both government and private payers has resulted in the widespread adoption of accreditation of advanced imaging facilities within the US. By far the largest accreditation program is that run by the American College of Radiology (ACR) and includes two components: 1) an initial application that involves the submission of both clinical diagnostic and phantom image data, and 2) following successful accreditation, the establishment of a routine quality control program involving calculation, on a weekly basis, of a variety of metrics from MR images of an ACR-designed image quality phantom. While the ACR provides detailed methods for manually calculating these metrics, they are time-consuming, and prone to human bias and error. In addition these measurements can take tens of minutes. For centers with more than one MR scanner, performing these quality control checks can be a significant time constraint for technologists and other support staff. To address this, we have developed an automated, webbased quality control program. The program involves daily acquisition of ACR MR phantom data, transfer of the data to a remote workstation, processing of these images to extract ACR recommended quality control metrics, and storage of these data in an institutional relational database. Data are then reviewed remotely through an in-house quality control web application. The web application indicates whether or not each test is within user-defined limits, thereby determining the pass/fail status of the test. Manual data entry is allowed in accord with ACR requirements. The system was first introduced into our clinical practice in 2006, starting with eight MR scanners and since that time has been expanded to include 38 MR scanners located at the three campuses of the Mayo Clinic (Rochester, MN, Scottsdale, AZ, and Jacksonville, FL). To date, a total of 59,775 phantom studies at field strengths of 1.5T and 3.0T from two MR scanner manufacturers have been processed by this tool. In addition, the application has been successfully commercialized and is offered on a fee-for-service basis by an independent startup company.

learning objectives
Describe the process of developing this system. 1.
Describe the pitfalls and challenges encountered.

2.
Identify the value of such an approach given the increasing financial constraints experienced 3. by many radiology departments. Provide examples of system detected failures and their root cause.
Recommendations will be provided for those wishing to develop similar systems for compliance with ACR accreditation recommendations.

Purpose
To develop a rapid, accurate in Vivo dose measurement technique for use in volumetric-modulated arc therapy (VMAT) treatments using single arc-integrated electronic portal images.

Methods
The dose measured along axis of gantry rotation can be directly related to the signal along the y-axis of EPIs in integrated mode. A simple back-projection algorithm was developed using a composite transmission factor averaged over the gantry angles subtended by the treatment arc. Corrections were applied in order to account for beam hardening, scattered radiation within the EPID, phantom-to-EPID scatter, and phantom scatter. Four clinical prostate VMAT treatment plans were exported for delivery to an anthropomorphic phantom, and integrated EPIs were recorded.

Results
Portal image reconstructed doses at isocenter agreed with treatment planning system calculations (mean difference of 4.4% and standard deviation 2.7%). 1D dose profiles along the axis of gantry rotation showed good agreement with planned doses (percentage of gamma-index values less than unity of 88.3% and standard deviation 9.5%). Upon the introduction of an empirical global small-field correction factor, the agreement improved greatly (percentage of gamma-index values less than unity of 94.4% and standard deviation 5.2%) Verification time per plan is approximately 1 minute for the first fraction and approximately 5 seconds for each fraction thereafter.

Conclusion
Single integrated EPI <i> in vivo </i> dosimetry has been successfully extended to VMAT treatments, albeit with the absence of true dosimetric information in the cross-plane direction. We conclude that 1D dosimetric verification using single EPIs can supplement, but not replace, pretreatment patient specific dosimetric QA.

Purpose
To develop a tool for predicting treatment couch coordinates based on CT simulation data and demonstrate its effectiveness at reducing first fraction couch coordinate overrides.

Methods
A spreadsheet was developed to calculate treatment couch coordinates based on measurements of two diverging wires embedded in the couch top of the CT simulator. One wire is parallel to the longitudinal axis of the couch, whereas the second wire remains parallel to the couch surface but is angled approximately 5° to the longitudinal axis. Lateral and vertical coordinates are determined from the differences in X and Y coordinates between isocenter and the first wire. The lateral distance between the two wires measured in the axial plane containing isocenter is used to determine the longitudinal coordinate. The calculations assume standardized indexing of immobilization at simulation and treatment. Calculated couch coordinates were compared to actual treatment coordinates recorded for 140 patients. The number of first fraction couch overrides was counted and compared to the number that would have occurred if default couch coordinate values had been used.

Results
For the 153 unique isocenters that were treated, only 12 (8%) required a couch override for the first fraction. In comparison, if default couch coordinates were used, then 150 (98%) would have a couch override for the first fraction. Of the 12 overrides, seven were expected due to an intentional change in indexing.

Conclusion
The described technique for calculating treatment couch coordinates has been implemented for nearly all patients at multiple radiotherapy centers. A significant reduction in first fraction couch coordinate overrides has been demonstrated. In addition to adding a quality control check at the first treatment, the elimination of the routine first fraction couch override is expected to increase patient safety by combating override desensitization.

Purpose
To develop software that performs quantitative analysis from portal image data of the radiation isocenter shape and position in space, relative to the linac in-room laser, for SRS treatments.

Methods
A suitable phantom BB (i.e., Winston-Lutz (W-L) phantom) was aligned to laser isocenter while a radiosurgery cone is centered on the gantry crosshairs. The largest cone available (15 mm) was used to produce a suitable outline around the phantom. Portal images were created in cine mode during a 360° arc. The developed software analyzes each phantom image displacement, then creates a 3D back-projected volume representing the average isofluence from a complete arc. The surface demarcated by 80% fluence intensity is used to represent mechanical/radiation isocenter. The program output includes shifts required to bring the mechanical and laser isocenters into coincidence. Tests were conducted to assess sensitivity, accuracy, and reproducibility of the method.

Results
The projected portal image pixel size at isocenter for 140 cm SID is 0.5 mm. The algorithm uses 50% intensity averages to find the cone and phantom centers to a measured precision of 43 microns for a static setup. This far exceeds measured radial magnitude of cone-mount setup error which was found to be 0.37 mm ± 0.14 mm. The software, from reconstruction of isocenter, was able to detect intentional phantom displacements (3.0 mm, 2.0 mm, and 1.0 mm in the coronal, transverse, and sagittal dimensions, respectively) to within a 0.3 mm range of visual detectability.

Conclusion
The software analysis provides both more accurate quantitative data than the traditional W-L test as well as a 3D rendering of average radiation isocenter over an entire arc. As a result, it can quantitatively assess the degree of gantry mechanical displacement using the fluence back-projection, and generate laser shifts which allow for easy and accurate readjustment of linac room lasers.

MO-B-Salon EF-04 investigation of x-Ray Attenuation Properties of organs Within the Body and Head of Cadaveric Subjects Vs. living Patients for the Validation of CT organ Dose Measurements
A Mench, 1* L Sinclair, 1 T Griglock, 2 B Cormack, 1 J Sirera, 1 M Arreola 1 University of Florida, 1 Gainesville, FL, Oregon Health and Science University, 2 Portland, OR

Purpose
To investigate how postmortem changes observed in human tissue affect X-ray attenuation characteristics and confirm the validity of using cadaveric subjects for direct organ dose studies in computed tomography (CT).

Methods
In order to assess the effects of postmortem changes on the X-ray attenuation properties of human tissue, and consequently on absorbed dose, seven cadaveric subjects and five living patients spanning a range of body mass indices (BMIs) from 17 to 49 were analyzed in this study. Head-and-body CT scans were used to delineate regions of interest (ROIs) encompassing various organs and to obtain average Hounsfield units (HUs) for each region. The calculated effective X-ray energy was used to determine attenuation coefficients based on these HUs and to draw comparisons between those from organs of cadavers and living patients.

Results
Most organs showed attenuation coefficients differing by less than 1% between cadaveric subjects and living patients. Breast tissue differed by 2.02% and lungs without the presence of fluid differed from living patients by 2.77%. More significant differences in attenuation were found where fluid had infiltrated the cadaveric lungs and caused a discrepancy of 10.54%. The use of cadavers with minimally fluid-filled lungs is still clinically relevant as they represent patients with pleural effusions or pneumonia. The results remained consistent with those found in other literature.

Conclusion
The findings show excellent agreement in attenuation properties between the organs of cadaveric subjects and those of live patients, with the exception of lungs with high levels of fluid retention. This confirms the accuracy of using cadavers for measurement of average organ doses delivered to patients during routing CT examinations.

Purpose
The PTW OCTAVIUS 1000 SRS is a novel planar array of 977 liquid ionization chambers on fine grid spacing. In this study, we examine the dose response of the 1000 SRS and demonstrate its use for 2D IMRS QA.

Methods
The 1000 SRS (PTW, Germany) was exposed by a Novalis 6 MV beam (BrainLAB AG, Feldkirchen, Germany) for dosimetric tests. Response was characterized by: reproducibility, linearity, nominal dose rate, field size and depth, angular dependence, and TMR measurements. Finally, a 15 beam IMRS plan was computed and delivered on a 1000 SRS phantom.

Results
A reproducible and linear dose response over 5 cGy to 6 Gy was observed. Response per cGy was within 0.2%. A dose-rate dependence of nearly 3.5% from 160 MU/min to 800 MU/min was seen, whether the device was cross-calibrated at 160 or 480 MU/min. Response dependence on field size and depth was observed and smallest at shallow depths. The angular dependence was about 2% when the beam entered from the back of the detector. and was asymmetric between left and right side irradiations. Gamma analysis on measured and planned IMRS dose distributions yielded 95.6% passing rate at 2%/2 mm and 99% at 3%/3 mm, which compared favorably with standard film and ionization chamber measurements.

Conclusion
A linear, reproducible dose response over a wide dose range indicates that the detector would be suitable for varying dose/segment and dose levels often seen in IMRS patient specific QA. Dense detector packing contributed to acceptable QA results on a small IMRS field. A nearly 3.5% difference over a range of nominal dose rates, as well as field size and depth dependence, indicates that the choice of cross-calibration field size and dose rate should be driven by clinical practice. Angular dependence may be mitigated by orienting the detector perpendicular to the beam central axis.

Purpose
To investigate the variation of imaging dose and image quality with tube potential in body perfusion protocols using the task group 111 dosimetric formalism.

Methods
TG111 recommendations were followed in choosing the phantom, dosimetric equipment, and methodology. Specifically, equilibrium doses were measured centrally and peripherally, and an average planar equilibrium dose was determined for each tube potential, for a reference set of exposure parameters (collimation, pitch, filtration) on a Siemens Somatom Definition AS+ scanner (Siemens Medical Solutions, Malvern, PA). This was compared to an equivalent dosimetric index, the weighted CT dose index. To analyze the image quality variation with tube voltage, inserts with different concentrations of iodinated contrast agent were placed in the phantom. The imaging was done using a 144 mm, 1.5 sec body perfusion protocol in shuttle mode, while the imaging doses were kept constant.

Results
Equilibrium dose increases with tube potential following an approximate kVp cube function. Furthermore, there is a significant underestimation of the imaging dose as reported based on CTDI measurements, ranging from 51% at 70 kVp to 58% at 140 kVp. CNR values generally decrease with increasing tube potential. Acceptable contrast-to-noise ratios values (70 kVp: 1.7; 80 kVp: 1.3) for the lowest concentrations of agent used, indicating that lower patient doses could be utilized for imaging.

Conclusion
Significant dose underestimation by the console report was noted. When imaging different concentrations of imaging agents, it was observed that for the same imaging dose lower kVp values, and inherently lower imaging doses can produce acceptable CNR images for all investigated concentrations. Future work will include further investigations in the TG111 parameterized dose metrics and assumptions. A full dosimetric evaluation of current body perfusion protocols will determine the exposure parameters associated with their clinical implementation. Furthermore, the scanning speed, sampling frequency and tube current limits will also be investigated.

Volume-based evaluation of Geometric Distortion in Magnetic Resonance imaging Using 3D Template Matching
K Huang, 1* Y Cao, 1 U Baharom, 2 J Balter 1

Purpose
Treatment planning with solely MR images is drawing increased interest in radiation therapy. One of the major issues potentially limiting such use is the possibility of geometric distortion inherent in MR images. Previously the evaluation of MR distortion has been either done in 2D or in 3D using 2D images in AP, SI, and LR planes. We proposed a method to determine the distortion of MR image volume in a real 3D approach.

Methods
A large phantom with 3D array of spheres filled with contrast was scanned with a 3T MRI simulator (Siemens Skyra, Siemens Medical Solutions, Malvern, PA) using T1 3D-Vibe protocol (TR 4.39 ms and TE 2.03 ms). 3D template matching using templates of sphere and half spheres with different orientations were used to locate the sphere centers. The normalized cross-correlation (NCC) value measures how well the image pattern is matched with templates. The half-sphere templates are used when the NCC value is below threshold. To remove the shift of the sphere centers induced by the physical rotation and translation of the phantom, the Procrustes method was applied. Then the distortion at each sphere center is calculated and the distortion map of the whole image space was generated by interpolation.

Results
Among the half-sphere templates used in matching, down half-sphere was most frequently used (83%), followed by left/right half-sphere (8% each). Among all the sphere centers, 80% have distortion less than 1 mm, 14% have 1 to approx. 1.5 mm distortion, 4.4% have 1.5 to approx. 2 mm distortion, and 1.6% have distortion more than 2 mm. The coordinates of the location closest to center with > 2 mm distortion is at (11.0, -17.8, -4.7).

Conclusions
This work successfully demonstrated 3D template matching is effective to locate the coordinates of a sphere center in 3D simultaneously. With this method, a high-fidelity MR distortion map was able to be generated in less than 1 minute.

Purpose
While CT has allowed for great advances in the field of diagnostic imaging, this progression has not ensued without careful attention to the radiation dose associated with its use. There remains a critical need to accurately assess organ doses resulting from these procedures. This research aims to directly measure organ doses by utilizing cadaveric subjects.

Methods
Techniques in a CT exam are tailored according to patient size and scanner-specific parameters. To account for this, four cadaveric subjects of body mass indices (BMI) ranging from 17 to 49 (BMI) were utilized for direct organ dose measurement on a 320 slice CT scanner. A dosimeter placement system was previously developed which utilizes optically stimulated luminescent dosimeters (OSLDs). The OSLDs were placed on the skin and within the following organs: thyroid, lungs, breasts, liver, stomach, small intestine, large intestine, uterus, and ovaries. The location and number of dosimeters were based on the size and distribution of each organ, with a maximum of 48 dosimeters used for each scan. A variety of clinically accepted CT protocols was examined, including chest (C), abdomen (A), pelvis (P), CAP, 3-phase liver, pulmonary embolism, and trauma protocols.

Results
Average and maximum organ doses were recorded for each exam. For a CAP exam, average organ doses for all subjects ranged from 8-26 mGy for organs in the primary beam. The highest organ doses were observed in the two subjects that classified as obese, with BMIs over 30.

Conclusion
Direct organ dose measurement resulting from CT exams is possible and has been completed for a range of representative adult patient sizes and clinical protocols with this research. This methodology can be extended to any CT scanner, protocol, or patient size, resulting in more accurate dose data. Additionally, these directly measured organ doses can be compared to estimated values obtained from other methodologies.

Purpose
To evaluate the dependence of an automatic match process on the size of the user-defined region of interest (ROI), the structure volume of interest (VOI), and changes in tumor volume when using CBCT for lung tumor localization, and to compare these results to a gold standard defined by a physician's manual match.

Methods
Daily CBCT images for 11 lung cancer patients (109 fractions) treated with conventionally fractionated radiotherapy were retrospectively matched to a reference CT using Varian's OBI software (Varian Medical Systems, Palo Alto, CA) and a three-step automatic matching protocol. Matches were performed with three ROI sizes (small, medium, large), both with and without a structure VOI (ITV or PTV) used in the last step. Additionally, matches using an intensity range isolating the bony anatomy of the spine were performed. All automatic matches were compared with a physician's manual match.

Results
Automatic match results depend on ROI size and the structure VOI. Compared to the physician's manual match, automatic matches using the PTV as the structure VOI and a small ROI resulted in differences greater than or equal to 5 mm in only 1.8% of comparisons. Automatic matches with a large ROI and no VOI resulted in differences of at least 5 mm in 30.3% of comparisons. Automatic matches to the spine resulted in differences of at least 5 mm in 21.1% of comparisons. Differences between manual and automatic matches using the ITV as the structure VOI increased as tumor size decreased.

Conclusions
This study illustrates the effectiveness of an automatic matching protocol for lung cancer patients even when large changes in tumor volume occur. Optimal matching parameters included using a small ROI and the PTV as the structure VOI on the last step of the automatic match process. Users of automatic matching techniques should carefully consider how user-defined parameters affect patient localization.

effect of Human Perception on Winston-lutz QA Process
A Moghadam, * R Hamilton, C Watchman

Purpose
This study demonstrates the effect of human bias in performing the QA tests and specifically quantifies the amount of uncertainty due to observer bias for the case of Winston-Lutz (WL) test for stereotactic radiosurgery (SRS).

Methods
24 WL tests for previously treated patients were used in this analysis. Each test was analyzed using a MATLAB program (The MathWorks, Natick, MA) which required the user to place a series of circles around the BB and cone regions. The positional differences were then determined by the program. A second program was developed to analyze the displacement of the circle centers automatically. The automated program uses center of mass calculation along with an optimization algorithm to find the outer irradiation circle and BB shadow circle. The optimization process involves finding the circle which maximizes the summation of pixel values enclosed by the circle for the outer irradiation circle. The BB circle is found by a minimum summation of pixel values. The difference in the measured deviation between the two methods of measurement was then evaluated.

Results
The average displacement measured by the manual process was found to be always smaller than the amount measured by the automated program. Our analysis also showed that 17% of the cases examined would have failed the WL criterion had the automated method been used.

Conclusion
Observer bias in WL analysis is a significant factor in the QA process. This analysis indicated that nearly 1/6 of observer determined cases would fail as compared to the objective method.
Also, it appears that the observer will innately conclude the deviation to be smaller than the automated method describe.

evaluation of GAFCHRoMiC xRQA2 Film for Varian oBi KV Scanner Dose Measurements
A Turner, * J Little

Purpose
To assess the magnitude of energy dependence of GAFCHROMIC XRQA2 for dose measurements performed using the Varian On-Board Imager (OBI) kV imaging system.

Methods
All measurements were obtained with the OBI (Varian Medical Systems, Palo Alto, CA) kV source at 120 kVp with a source to isocenter distance of 100 cm, 50 cm squared field, and the full bowtie filter. Reference measurements were obtained in air with an approximately energy-independent CC13 ionization chamber. Exposure profiles were measured across the bowtie filter over the entire isocenter plane, with increments of 2.5 to 5 cm, for longitudinal positions ranging from negative 20 cm to positive 20 cm. Film was exposed with a source to film distance of 40.6 cm, digitized, and projected to the isocenter plane. Film measurements were corrected for background and noise and the red channel was extracted. Both film and ionization chamber measurements were normalized to the respective isocenter value. The normalized film and exposure profiles were compared for each longitudinal position measured with the ionization chamber.

Results
Examination of the normalized profiles indicates that there are considerable differences between the film and ionization chamber measurements across the bowtie filter plane regardless of longitudinal position. The average normalized difference across all measurements was 33.4% ± 13.6%. In general, differences increased with radial distance from the isocenter until approximately 7.5 to 10 cm and then gradually decreased.

Conclusion
Since ionization chambers are approximately energy independent, the differences illustrate that GAFCHROMIC XRQA2 film may exhibit substantial energy dependence for the range of beam qualities across the isocenter plane for Varian OBI kV scanners. The variation in beam qualities is due primarily to the varying thickness of the bowtie filter, resulting in varying levels of beam hardening. It may be possible to correct film measurements for controlled measurement setups. Future work will be done to evaluate different tube voltage levels, bowtie filter settings, and film processing protocols.

Purpose
To evaluate the optimization strategies for midline and peripheral tumors for IMRT and RapidArc treatments.

Methods
Homogeneous phantom was CT scanned and PTV was delineated for two different positions (midline and periphery). Two organs at risk with different shapes (organ at risk 1, organ at risk 2) were created. Different plannings were done with organ at risk 1, placed at distance of 0.5 cm and 2 cm. Also organ at risk 2, placed at a distance of 1 cm and 2.5 cm from the border of PTV along the central axis. Planning has been done for IMRT using nine fields and RapidArc (Varian Medical Systems, Palo Alto, CA) with double arc. Beam has been equally placed for IMRT plans and RapidArc plans utilize full 360° gantry rotation.

Results
Dose homogeneity was almost similar for tumors in the midline where organs at risk are far. But RapidArc plans show superior dose homogeneity in PTV, when the target is situated at the periphery and organs at risk are very near (HI -2.67 for Rapid Arc and HI 4.03 for IMRT). Target coverage was better for all RapidArc plans with maximum CI 1.01. The sparing of organ at risk in terms of the maximum dose was better in RapidArc. A considerable reduction in organ at risk mean dose (12.37% for organ at risk 1 and 10.23% for organ at risk 2) was observed with RapidArc technique for peripheral tumors. For healthy tissue, no significant changes were observed in terms of the mean dose and integral dose. But RapidArc plans show a reduction in the volume of the healthy tissue irradiation above V10 Gy for targets at the periphery and OAR near.

Conclusion
Either IMRT or RapidArc can be chosen for tumors in the midline. In particular, RapidArc treatment can be recommended for tumors which are situated at the periphery.

MO-B-Salon BCD-01
x-Ray Fluoroscopy imaging in the invasive Cardiac laboratory: Medical Physics Support of a Contemporary Practice

K Fetterly
Mayo Clinic, Rochester, MN While there are several imaging technologies that are used to diagnose and treat cardiovascular disease, X-ray fluoroscopy remains the primary modality used for guidance during invasive cardiovascular procedures. From the clinical perspective, fluoroscopy system quality is a combination of image quality and patient radiation dose. Image resolution, contrast, and noise are highly variable between systems and operational modes. Patient radiation skin dose is a principle safety concern and is highly dependent on the patient, clinical procedure, and imaging system design and operation. The purpose of this presentation is to provide information relevant to testing and optimizing interventional X-ray fluoroscopy systems to support a wide range of clinical imaging tasks. The various imaging technologies routinely used in a contemporary invasive cardiology laboratory will be introduced. Comprehensive methods to assess quality and clinically relevant skin entrance air kerma from interventional fluoroscopy systems will be presented. The relevance of image quality metrics will be presented in the context of the various clinical imaging tasks performed. System optimization with respect to patient dose requires a desire to reduce dose while not affecting the clinical utility of the images. This strategy provides the potential for substantial patient dose reduction. Modern X-ray system design and control offer many possibilities for radiation dose reduction. Specific methods to minimize patient radiation dose while not adversely affecting patient care will be presented.

learning objectives
Understand the need for and methods used to fully characterize interventional fluoroscopy 1.
system performance as it relates to the clinical imaging task.
Recognize system technical parameters that can be adjusted to reduce patient radiation 2.
dose. Appreciate the potential for active management to reduce patient radiation dose without 3.
adversely affecting the clinical utility of the images.

Mayo Clinic Arizona, Scottsdale, AZ
New commercial software products can capture patient exposure information, store these data and web-enabled reports to provide users with radiation prescriptions from diagnostic X-ray exams, including CT and Fluoroscopy. These tools provide highly relevant patient-specific and summary information that is enormously useful and actionable for ensuring that the intended exam exposure took place, in fact. Radiation dose to organs can be computed for CT exams and skin dose can be computed for fluoroscopy use. Excursions from intended prescriptions can be easily identified for a facility, device, protocol or patient. Six Sigma (SS) is well suited as the contextual approach of using these software tools as the improvements in accuracy and optimal prescription of X-rays for diagnosis deal with the unwanted variability that a 'process'-driven service inherently generates. Basic SS concepts introduced in this talk derive from DMAIC (Define, Measure, Analyze, Improve, and Control), the organized approach for systems engineered changes having improvements in quality as the goal. Data show that prescriptions of X-ray as currently configured with these devices allow for wide ranges of patient exposures (machine outputs). At its basis, the range of patient size, geometry of patient positioning, and the image quality needs of clinically needed but widely ranging types of diagnostic exams or therapeutic interventions with fluoroscopic and CT. Included in the measures of observed variability is the complexity of operator selectable device controls. This increases the opportunity for nonuniform training of staff leading to further variations from the ideal. Six Sigma recognizes that the primary need is to reduce variability from the intended dose prescription goal. It embraces team involvement, continuous improvement, standardization, and education as basic to improving outcomes. DMAIC notes that it is not the individual but the process which is faulty. Specific examples of data gathered by these software tools will be used to show how one can monitor, understand, and facilitate improvements for CT and fluoroscopy. minimum level of medical physics support that the AAPM would consider to be prudent in all clinical practice settings. As accreditation of clinical practices becomes more common, MPPGs will be crucial to ensuring a consistent benchmark for accreditation programs. MPPG reports will be freely available to the general public. Accrediting organizations, regulatory agencies, and legislators will be encouraged to reference these MPPGs when defining their respective requirements. Support includes, but is not limited to, staffing, equipment, machine access, and training. This session will describe the purpose and scope of MPPGs, the procedure for the development of a MPPG, and reports from TG-226 MPPG Therapy #1 and TG-225 MPPG Diagnostic #1. TG-226 MPPG Therapy #1 has completed their report, entitled ''Evaluation and quality assurance of x-ray based image guided radiotherapy system''. Sections of the TG-226 report include a review of image-guidance technologies, a description of the treatment team and their responsibilities in IGRT system use and management, and recommendations for minimum commissioning and quality assurance practices. Sample process descriptions, including equipment and methods, for recommended quality assurance practices are provided. Finally, staffing estimates and resource requirements needed for IGRT system management are provided. TG-225 MPPG Diagnostic #1 has completed their report, entitled ''CT Protocol management and review''. Sections of the TG-225 MPPG Diagnostic #1 report include a description of the CT protocol management and review process, team members and their responsibilities, and a general description of the overall CT protocol management and review process. Issues such as recommended review frequency, acquisition parameters to review, documentation of the review process, and refresher education for the CT protocol management and review team are addressed. This MPPG acknowledges that CT protocol management and review are essential to providing images with sufficient quality and ensuring patient safety. It also acknowledges that this process is very challenging and identifies areas for development, including improved tools from the CT manufacturers that are sorely needed in order to make this process more efficient.

learning objectives
Understand the concept, scope, and process of MPPG from the AAPM.

Speakers
Jonas Fontenot, Chair of TG-226 MPPG Therapy #1 Dianna Cody, Chair of TG-225 MPPG Diagnostic #1 This is a two-hour panel discussion of controversial and professional topics in medical physics. Specific topics have been identified for debate and audience participation. When applicable, controversial scenarios will be addressed with AAPM publications including task group reports, position statements, and editorials from medical physics journals.

learning objectives
Discuss the meaning of ethics and professionalism.

1.
Review relevant AAPM publications relating to identified controversial topics.

2.
Discuss controversial topics and discover audience opinion from audience interaction. 3.

MO-D-Salon EF-01
Data integrity and electronic Charting (eBRT and Brachytherapy) The Electronic Medical Record (EMR) in Radiation Oncology presents the additional challenge of controlling medical equipment, setting it apart from the rest of the Hospital Information Systems Databases. Errors in these records can have potentially fatal consequences, underscoring the need for careful implementation, testing, and maintenance. An understanding of the information technology infrastructure, data storage, and data flow in radiation oncology is crucial for the design of quality assurance policies and procedures that must be performed to maintain data integrity. Such procedures address the data transfer among various subsystems encountered as the patient moves from the initial consult to treatment. These tests should check that treatment information, not just data, is preserved during a transfer between pairs of subsystems. The relevant principles outlined in the rapid communication and the draft TG201 full report will be reviewed, followed by a discussion of the logistics involved in a successful implementation of the EMR. This success depends on the support of not only radiation oncology personnel but also hospital IT staff. Personnel involved in the information exchanges with the EMR will need to evaluate all current processes and modify them to be compatible with the EMR. The modifications should facilitate a safer and more accurate delivery of radiation, not only for external-beam radiation therapy (EBRT) but also for brachytherapy. They should also exploit the advantages of an EMR to make processes more efficient and maintain the culture of safety. Implementation of the EMR in brachytherapy requires the collaboration of the Radiation Oncology Department and the hospital Radiation Safety Department to ensure compliance with the NRC or State requirements. An overview of the clinical implementation process of electronic charting for both external beam and brachytherapy will be presented.

learning objectives
Review basic IT infrastructure concepts that are used in the deployment of Electronic Medi-1.
cal Records in Radiation Oncology.
Understand the principles of QA and QC data transfer test design.

2.
Discuss department staffing and process evaluation for successful EMR implementation.

3.
Understand the workflow for implementation of the EMR for EBRT and Brachytherapy.

K Nelson
Mayo Clinic, Jacksonville, FL In a complex medical environment, ensuring compliance with ionizing radiation regulations and interpretations can be challenging, especially if an individual also has additional responsibilities beyond radiation safety. Participants will be expected to have a working knowledge of the applicable ionizing radiation regulations as they will not be reviewed in great detail during this session. Instead, issues identified during agreement state or NRC inspections will be reviewed. Particular focus will be paid to issues involving radioactive materials: RSO training requirements, use of unsealed byproduct material, required records, general technical requirements, security, and a review of NRC enforcement actions.

learning objectives
Review training and education requirements for a Radiation Safety Officer.

1.
Obtain a better understanding of typical regulatory issues encountered in the medical use 2.
of byproduct material. Review recent NRC enforcement actions against medical use licensees. 3.

M Martin
Therapy Physics, Inc., Gardena, CA Combined imaging modalities of PET/CT and PET/MRI are currently available in the United States. Designing the shielding required for these dual modality units is complex and requires knowledge of both modalities for these pieces of equipment. Design considerations for PET/CT scanners include delivery and storage of the radioisotope, dose preparation and administration, uptake rooms and restroom facilities, scanning room, control room, postscan requirements, and accompanying persons. The primary radioisotope used for whole-body PET scans is Fluorine-18 FDG while Rb-128 is used for cardiac studies. Ideally, the department is laid out with the highest level of activity toward an exterior wall and away from the reception and public areas of the department. Individual calculations for each of these areas must be made in accordance with the recommendations of AAPM Task Group 108 Report. Occupancy factors for each area vary and must be taken into consideration. Additional separate calculations must be performed for the expected exposures from CT scanner, particularly if the CT scanner is used independently from PET acquisitions. The same type of considerations must be made for the MRI/PET scanners in that the shielding needed for MRI will not provide protection from the radiation exposure from the CT scanner, while the usual lead shielding used to provide radiation protection for the CT scanner will not prevent artifacts in the MRI suite or excess magnetic fields in the control room area. Radio frequency (RF) shielding works to prevent exterior RFI (Radio Frequency Interference) from negatively affecting the operation of the MRI and the digital image being

learning objectives
To report on the additional requirements for multidisciplinary clinical trials. 1.
To describe examples demonstrating how audits, credentialing, and benchmarks can support 2.
quality in clinical trials.
To describe the benefits and requirements of close coordination of RT and imaging QA.

3.
To describe current and future needs for an efficient informatics infrastructure for clinical 4. trials.

R Pizzutiello
Upstate Medical Physics, Victor, NY Recent improvements in digital dental imaging have created new opportunities for medical physicists to contribute to its safety and quality. Cone-beam computed tomography (CBCT) has dramatically grown in to many dental specialty practices, and even into the offices of general dentists. In 2009, NCRP Report #160 estimated the order of magnitude of dental X-ray images to 100 million dental X-ray images are acquired annually in the USA. As digital dental imaging technology has advanced, increasingly "user friendly" systems have created the opportunity for suboptimally trained personnel to deliver more radiation than is needed for digital dental exams (think "Dose Creep", and more). Recent reports on dental imaging, including CBCT, from the American Dental Association, FDA, and IAEA will be summarized. This presentation will begin with common problems encountered in film-based dental imaging, but will primarily be focused on the digital dental imaging environment. Methods for evaluating the performance of dental radiography, cephalometric, panoramic, and CBCT will be presented. The medical physics requirements for the Intersocietal Accreditation Commission CT Accreditation Program for dental CBCT systems will be reviewed.

learning objectives
Understand the impact of digital imaging on the dental radiation safety.

1.
Understand the methodology for performance evaluations of dental imaging systems.

2.
Understand the medical physics requirements for IAC CT accreditation of dental CBCT 3. systems.

TU-A-Salon BCD-02
The American College of Radiology Random on Site Survey

UT MD Anderson Cancer Center, Houston, TX
As part of its accreditation programs, the American College of Radiology (ACR) reserves the right to perform on-site surveys of any facility at any time during the accreditation process. For mammography, the ACR is actually directed by MQSA to perform on-site surveys of at least 5% of the facilities it accredits each year. The ACR calls these surveys a Random On-Site Survey study examining conflict within a medical unit to determine whether internal conflict has an impact on the patients and their perceptions of care. Lastly, there are important issues facing the medical profession due to the generation gap between older and younger members of a healthcare team. While not unique to the health-care field, intergenerational communication issues may impact patient care and doctor-patient communication, as the different age groups have very different expectations regarding effective and efficient communication. Additionally, the impact of the new 80-hour work week on the training of residents and interns is causing an usversus-them mentality among members of the health-care team. This presentation will discuss these intergenerational issues by concentrating on the communication-related issues resulting from the new limits on medical training. The presentation will conclude with suggestions for training techniques, and for future research into effective and efficient communication among medical personnel and between medical staff and patients.

N Anderson
Robert Boissoneault Oncology Institute, Ocala, FL As a physician for over 32 years, I have grown both in knowledge of medicine and understanding of human nature. The training of a physician can create a gamut from compassionate healers to self-proclaimed god-like figures whose "fame" is elucidated for your benefit at the drop of a hat. The latter group of medical doctors have unlimited ability. If in doubt, ask them, and they will provide you detailed justification for their arrogance. The mental framework of a physician -Control vs. Communication, Dictate vs. Discuss, Ego vs. Equal, Superiority vs. Sensitivity, Tyrant vs. Team, Fiefdom vs. Fraternity, Part vs. Patient, Number vs. Name. On the other side of the coin is the patient. In most cases, individuals feel in control when their environment allows the use of familiar skills. Due to a medical situation, control is now lost. One becomes overwhelmed with the totality of their illness or that of a close friend/relative. The "unknown" that the future holds causes one to focus on every word, comment, and statement that is uttered by a professional, or nonprofessional. After all, cancer is the big unknown, and we use an invisible unknown to cure. Such a combination does not comfort one's soul. Remember, even a physician becomes totally dependent on those providing care. All face the same feeling of hopelessness, as the initials behind a name fail to calm emotion. The mental framework of a patient -Secure vs. Scared, Calm vs. Confused, Knowledge vs. None, Reaching for Hope vs. Reaching for Hope while Waiting for the Touch of Compassion/Listening for the Voice of Comfort/Searching for the Answers Between. There are a myriad of staff whose experience with such diverse personalities varies dramatically. Some have the ability to quell the fire of anxiety. Others seem to incite, as gasoline is thrown on the flames. And there you are. You are a medically trained professional attempting to bridge the gap, demonstrating your ability to a physician who may view you as equal colleague or custodian; or to the patient who misspells your professional title, much less understands the vital knowledge you provide for their health. In reality, the goal of medical treatment is not accomplished by one individual. And verbal communication, as you will see, is only one of the tools. This presentation will facilitate your efforts to reach that goal. Over time, the physicians will appreciate your participation in the healing process, as the team provides the patient with an answer to the mystery of medicine. I guarantee the satisfaction you experience will rival your professional achievements. I know this to be the case because I know how the arrogant doctor's brain works. You see ... I once was one.