Volume 47, Issue 2 p. 488-497
Technical Note

Technical Note: Performance comparison of ultra-high-resolution scan modes of two clinical computed tomography systems

Hiroki Kawashima

Corresponding Author

Hiroki Kawashima

Faculty of Health Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, 920-0942 Japan

Author to whom correspondence should be addressed. Electronic mail: [email protected]; Telephone: +81-76-265-2531.

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Katsuhiro Ichikawa

Katsuhiro Ichikawa

Faculty of Health Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, 920-0942 Japan

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Tadanori Takata

Tadanori Takata

Radiology Division, Kanazawa University Hospital, 13-1 Takara-machi, Kanazawa, 920-8641 Japan

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Hiroji Nagata

Hiroji Nagata

Section of Radiological Technology, Department of Medical Technology, Kanazawa Medical University Hospital, Daigaku 1-1, Uchinada, Kahoku, 920-0293 Japan

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Minori Hoshika

Minori Hoshika

Departments of Radiology, Okayama University Hospital, 2-5-1 Shikatacho, Kitaku, Okayama, 700-8558 Japan

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Noriaki Akagi

Noriaki Akagi

Departments of Radiology, Okayama University Hospital, 2-5-1 Shikatacho, Kitaku, Okayama, 700-8558 Japan

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First published: 06 December 2019
Citations: 16

Abstract

Purpose

Two ultra-high-resolution (UHR) computed tomography (CT) scanners are clinically available. One is achieved by a CT system with a 0.25 mm × 160 row detector (Detector-UHR), whereas the other is with a 0.6 mm × 32 row detector with in-plane comb filtering in a dual source CT (Comb-UHR). We compared radiation dose efficiencies of the two UHR modes to that of a routine scan mode (RS), using physical image quality measures for an assumed condition of abdominal CT angiography (CTA).

Methods

A wire phantom, a 300-mm cylindrical water bath phantom, and a microdisk phantom were used for measuring the modulation transfer function (MTF), noise power spectrum (NPS), and slice sensitivity profiles (SSP), respectively, at CTDIvol of 20 mGy. Images with minimal slice thicknesses were reconstructed by filtered back projection methods. System performance functions (SPF2) based on the prewhitening theorem were calculated by dividing MTF2 by NPS measurements. The ideal observer's detectability index (d'2) was also estimated for a task corresponding to a 1-mm diameter vessel. Furthermore, a bar-pattern phantom placed in a water phantom resembling an adult abdomen was scanned, and the visibility of the bars was observed.

Results

System performance function (SPF2) results showed that Comb-UHR has a 70% dose efficiency compared to RS and provides better than twofold SPF2 compared to Detector-UHR. The d'2 values of Detector-UHR, Comb-UHR, and RS were 6.5, 14.7, and 16.0, respectively. Although the bar-pattern phantom images were consistent with the SPF results, bar widths < 1.0 mm for Detector-UHR and < 0.75 mm for Comb-UHR and RS were not resolved.

Conclusions

Though both the UHR modes exhibited system performances extending to 2.6 cycles/mm, they appeared not to be advantageous compared to RS in the conditions applicable to abdominal CTA, because of their insufficient dose efficiencies.

Conflict of Interest

The authors have no relevant conflict of interest to disclose.