Volume 33, Issue 1 p. 216-224
Radiation imaging physics

Monte Carlo simulations of dose from microCT imaging procedures in a realistic mouse phantom

Richard Taschereau

Richard Taschereau

The Crump Institute for Molecular Imaging, Department of Molecular and Medical Pharmacology, University of California School of Medicine, 700 Westwood Boulevard, Los Angeles, California 90095

Electronic mail: [email protected]

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Patrick L. Chow

Patrick L. Chow

The Crump Institute for Molecular Imaging, Department of Molecular and Medical Pharmacology, University of California School of Medicine, 700 Westwood Boulevard, Los Angeles, California 90095

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Arion F. Chatziioannou

Arion F. Chatziioannou

The Crump Institute for Molecular Imaging, Department of Molecular and Medical Pharmacology, University of California School of Medicine, 700 Westwood Boulevard, Los Angeles, California 90095

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First published: 28 December 2005
Citations: 86

Abstract

The purpose of this work was to calculate radiation dose and its organ distribution in a realistic mouse phantom from micro-computed tomography (microCT) imaging protocols. CT dose was calculated using GATE and a voxelized, realistic phantom. The x-ray photon energy spectra used in simulations were precalculated with GATE and validated against previously published data. The number of photons required per simulated experiments was determined by direct exposure measurements. Simulated experiments were performed for three types of beams and two types of mouse beds. Dose-volume histograms and dose percentiles were calculated for each organ. For a typical microCT screening examination with a reconstruction voxel size of urn:x-wiley:0094-2405:media:mp8333:mp8333-math-0001, the average whole body dose varied from urn:x-wiley:0094-2405:media:mp8333:mp8333-math-0002 (at urn:x-wiley:0094-2405:media:mp8333:mp8333-math-0003) to urn:x-wiley:0094-2405:media:mp8333:mp8333-math-0004 (at urn:x-wiley:0094-2405:media:mp8333:mp8333-math-0005), showing a strong dependence on beam hardness. The average dose to the bone marrow is close to the soft tissue average. However, due to dose nonuniformity and higher radiation sensitivity, 5% of the marrow would receive an effective dose about four times higher than the average. If CT is performed longitudinally, a significant radiation dose can be given. The total absorbed radiation dose is a function of milliamperes-second, beam hardness, and desired image quality (resolution, noise and contrast). To reduce dose, it would be advisable to use the hardest beam possible while maintaining an acceptable contrast in the image.