With the growing use of computed tomography (CT) and the increasing awareness of radiation risk, important areas of research concern (1) optimizing CT clinical applications to minimize radiation dose and (2) developing methods to accurately assess radiation risk from examinations. Due to radiation concerns in patients and the limited number of physical phantoms that do not reflect the variability of patient anatomy, such research can only be performed using a population of realistic computational phantoms, which currently does not exist. Current phantoms used in CT are limited to only a handful of models, most being adults. In the previous project, we developed the new 4D XCAT computational phantom for use in 3D and 4D CT research. Based on high-resolution imaging data, we created detailed whole-body models for the male and female XCAT adult, including the cardiac and respiratory motions, containing over 9000 anatomical structures. In part one of this renewal, we will extend the XCAT beyond these adult models by utilizing innovative methods in computational anatomy, that have long been used to characterize anatomical variations in populations, to efficiently create an unprecedented library of hundreds of highly detailed 4D XCAT phantoms. The models will realistically represent the full spectrum of the public at large including both genders, and varying ages, heights, and weights from infancy to adulthood. The ability to model anatomical variations is essential to CT imaging optimization. A population of phantoms that includes a range of anatomical variations representative of the public at large is needed to more closely mimic a clinical study or trial. Such a library of anatomically diverse phantoms also offers the only practical technique with which to estimate patient-specific CT dose and associated radiation risk. In the second part of this project, the library will be combined with an accurate Monte Carlo dose estimation program, developed and validated in this work, to investigate patient-based and population-based dose correlations in CT. The findings will be used to establish a patient-specific retrospective and prospective CT dose reporting system. Such a system will be instrumental in proper documentation of radiation risk, justifiable use of CT examination, and optimization of clinical CT applications in terms of image quality and radiation dose, particularly in vulnerable populations. It further supports the current mandate to account for cumulative radiation dose exposure from medical imaging. Distributed to the research community, the dosimetry methods and the phantom library will provide vital tools to quantitatively evaluate and improve 3D and 4D CT imaging devices and techniques.

Public Health Relevance

In this renewal, we will create an unprecedented library of hundreds of detailed 4D computational models realistically representing a wide population of subjects including both genders, and varying ages, heights and weights (10th to 90th percentile) encompassing the full range from pediatric to adult patients. The phantom series developed in this work will provide a vital tool with which to optimize clinical CT applications in terms of image quality and radiation dose and to accurately estimate patient-specific CT dose (both effective dose and organ dose) and associated radiation risk.

National Institute of Health (NIH)
National Institute of Biomedical Imaging and Bioengineering (NIBIB)
Research Project (R01)
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Biomedical Imaging Technology Study Section (BMIT)
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Pai, Vinay Manjunath
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Duke University
Schools of Medicine
United States
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Li, Xiang; Segars, W Paul; Samei, Ehsan (2014) The impact on CT dose of the variability in tube current modulation technology: a theoretical investigation. Phys Med Biol 59:4525-48
Samei, Ehsan; Richard, Samuel; Lurwitz, Lynne (2014) Model-based CT performance assessment and optimization for iodinated and noniodinated imaging tasks as a function of kVp and body size. Med Phys 41:081910
Belley, Matthew D; Segars, William Paul; Kapadia, Anuj J (2014) Assessment of individual organ doses in a realistic human phantom from neutron and gamma stimulated spectroscopy of the breast and liver. Med Phys 41:063902
Sahbaee, Pooyan; Segars, W Paul; Samei, Ehsan (2014) Patient-based estimation of organ dose for a population of 58 adult patients across 13 protocol categories. Med Phys 41:072104
Tian, Xiaoyu; Li, Xiang; Segars, W Paul et al. (2014) Pediatric chest and abdominopelvic CT: organ dose estimation based on 42 patient models. Radiology 270:535-47
Norris, Hannah; Zhang, Yakun; Bond, Jason et al. (2014) A set of 4D pediatric XCAT reference phantoms for multimodality research. Med Phys 41:033701
Segars, W P; Bond, Jason; Frush, Jack et al. (2013) Population of anatomically variable 4D XCAT adult phantoms for imaging research and optimization. Med Phys 40:043701
Hsu, Christina M L; Palmeri, Mark L; Segars, W Paul et al. (2013) Generation of a suite of 3D computer-generated breast phantoms from a limited set of human subject data. Med Phys 40:043703
Li, Xiang; Samei, Ehsan; Segars, W Paul et al. (2011) Patient-specific radiation dose and cancer risk for pediatric chest CT. Radiology 259:862-74
Li, Xiang; Samei, Ehsan; Segars, W Paul et al. (2011) Patient-specific radiation dose and cancer risk estimation in CT: part II. Application to patients. Med Phys 38:408-19

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