Affiliations: Department of Diagnostic Imaging, Peking Union Medical
College and Cancer Institute and Hospital, Chinese Academy of Medical Sciences, Beijing, China | Department of Radiology, Peking University of First
Hospital, Beijing, China | Department of Radiology, Peking University of People's
Hospital, Beijing, China
Note: [] Corresponding author: Xinming Zhao, Department of Diagnostic
Imaging, Peking Union Medical College and Cancer Institute and Hospital,
Chinese Academy of Medical Sciences, Beijing 100021, China. E-mail: xinmingzh@sina.com
Abstract: Multi-phase spiral Computed tomography (CT) of abdomen has been
widely used as an effective imaging modality to diagnose variety of diseases.
As a result, the accumulated radiation exposure on the abdomen is substantially
higher than other human organ regions. According to ALARA (as low as reasonably
achievable) principle, how to control radiation dose without compromising
imaging quality becomes a research topic of high interest. However, how to
achieve dose optimization of the abdomen CT examinations in Chinese patients
have not been fully investigated in previous studies. In this study, we develop
an abdomen-equivalent tissue model made by well-known CTP579 auxiliary testing
model and the real CT data acquired from 68 Chinese male subjects. Combining
with catphan600, we simulated the visibility of low and high contrast objects
at adult abdomen under variety of x-ray dose levels. Using the automatic tube
current modulation (ATCM) technique, we reduced the total radiation dose and
identified a proper noise index (NI) for Chinese patients to maintain low or
high contrast detectability of abdominal CT image. Our numerical experiments
showed that in the phantom study for Chinese patients, when a NI was set at 10,
the radiation dose reduced by 34.3% with low contrast objects detectable,
while setting NI at 14 the dose level decreased by 65.1% without change the
detectability of high contrast targets. The subjective ratings from three
radiologists also yielded high consistence with Kappa >
0.75. This study demonstrated the feasibility of performing the CT dose
optimization studies through a unique phantom with the ATCM method.
