Organ dose conversion coefficients for tube current modulated CT protocols for an adult population

Wanyi Fu; Xiaoyu Tian; Pooyan Sahbaee; Yakun Zhang; William Paul Segars; Ehsan Samei

doi:10.1117/12.2217271

31 March 2016 Organ dose conversion coefficients for tube current modulated CT protocols for an adult population

Wanyi Fu, Xiaoyu Tian, Pooyan Sahbaee, Yakun Zhang, William Paul Segars, Ehsan Samei

Proceedings Volume 9783, Medical Imaging 2016: Physics of Medical Imaging; 97833E (2016) https://doi.org/10.1117/12.2217271
Event: SPIE Medical Imaging, 2016, San Diego, California, United States

Abstract

In computed tomography (CT), patient-specific organ dose can be estimated using pre-calculated organ dose conversion coefficients (organ dose normalized by CTDI_vol, h factor) database, taking into account patient size and scan coverage. The conversion coefficients have been previously estimated for routine body protocol classes, grouped by scan coverage, across an adult population for fixed tube current modulated CT. The coefficients, however, do not include the widely utilized tube current (mA) modulation scheme, which significantly impacts organ dose. This study aims to extend the h factors and the corresponding dose length product (DLP) to create effective dose conversion coefficients (k factor) database incorporating various tube current modulation strengths. Fifty-eight extended cardiac-torso (XCAT) phantoms were included in this study representing population anatomy variation in clinical practice. Four mA profiles, representing weak to strong mA dependency on body attenuation, were generated for each phantom and protocol class. A validated Monte Carlo program was used to simulate the organ dose. The organ dose and effective dose was further normalized by CTDI_vol and DLP to derive the h factors and k factors, respectively. The h factors and k factors were summarized in an exponential regression model as a function of body size. Such a population-based mathematical model can provide a comprehensive organ dose estimation given body size and CTDI_vol. The model was integrated into an iPhone app XCATdose version 2, enhancing the 1st version based upon fixed tube current modulation. With the organ dose calculator, physicists, physicians, and patients can conveniently estimate organ dose.

Citation Download Citation

Wanyi Fu, Xiaoyu Tian, Pooyan Sahbaee, Yakun Zhang, William Paul Segars, and Ehsan Samei "Organ dose conversion coefficients for tube current modulated CT protocols for an adult population", Proc. SPIE 9783, Medical Imaging 2016: Physics of Medical Imaging, 97833E (31 March 2016); https://doi.org/10.1117/12.2217271

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