Application of the 4-D XCAT Phantoms in Biomedical Imaging and Beyond

Abstract

The four dimensional (4D) eXtended CArdiac-Torso (XCAT) series of phantoms was developed to provide accurate computerized models of the human anatomy and physiology. The XCAT series encompasses a vast population of phantoms of varying ages from newborn to adult, each including parameterized models for the cardiac and respiratory motions. With great flexibility in the XCAT’s design, any number of body sizes, different anatomies, cardiac or respiratory motions or patterns, patient positions and orientations, and spatial resolutions can be simulated. As such, the XCAT phantoms are gaining a wide use in biomedical imaging research. There they can provide a virtual patient base from which to quantitatively evaluate and improve imaging instrumentation, data acquisition, techniques and image reconstruction and processing methods which can lead to improved image quality and more accurate clinical diagnoses. The phantoms have also found great use in radiation dosimetry, radiation therapy, medical device design, and even the security and defense industry. This review paper highlights some specific areas in which the XCAT phantoms have found use within biomedical imaging and other fields. From these examples, we illustrate the increasingly important role that computerized phantoms and computer simulation are playing in the research community.

Development of a 4D Digital Phantom for Cone-Beam CT (CBCT) Imaging on the Varian On-Board Imager (OBI)

“…Furthermore, currently there is not a physical phantom that is able to accurately model the variability of the human respiratory motion. The advantage of using this developed 4D CBCT digital phantom over existing phantoms such as the 4D XCAT [2] phantom is that this phantom provides actual motion of each tissue and organ independently. Unlike XCAT , although it provides detailed human anatomical features and includes an internal motion model derived from 4D CT data [14], the motion model heavily depends on a user-defined motion curve that does not simulate the motion of each organ uniquely , thus hindering its ability to simulate complex deformations due to respiration [15].…”

“…The emergence of various digital phantoms , such as the widely used 4D XCAT phantom [2] in medical imaging have greatly aided the development of new algorithms to ensure the accuracy during IGRT , thus allowing them to be simulated prior to clinical validation. However, a main challenge still remains which is to generate a digital phantom that is able to accurately emulate the internal anatomical changes of various organs due to either respiratory and/or cardiac motion.…”

Toward automated and personalized organ dose determination in CT examinations — A comparison of two tissue characterization models for Monte Carlo organ dose calculation with a Therapy Planning System

“…In practice, the calculated average organ doses from these studies are often adapted to the patient by simple scaling methods based on for example, actual body size . The procedure is practical, but comparisons between different phantom models show large differences in organ doses despite closely matched organ and patient characteristics, which could be indicative for the uncertainties in the estimates vis‐a‐vis the actual average organ dose in the patient . Application of individualized organ dose estimates together with clinical information should be able to provide risk estimates better adapted to medical exposures through epidemiological studies in patient cohorts, conforming to or improving on the current estimates, primarily based on the atomic bomb survivors…”

“…18 The procedure is practical, but comparisons between different phantom models show large differences in organ doses despite closely matched organ and patient characteristics, which could be indicative for the uncertainties in the estimates vis-a-vis the actual average organ dose in the patient. 21,22 Application of individualized organ dose estimates together with clinical information should be able to provide risk estimates better adapted to medical exposures through epidemiological studies in patient cohorts, conforming to or improving on the current estimates, primarily based on the atomic bomb survivors. 1 A valid alternative to phantom models would be to directly perform MC dose calculations 23,24 for the actual exposure and patient specific anatomy.…”

Dynamic phantoms: Making the right tool for the job

“…When asking questions about the capability of the design of a system, computer simulations can be extremely valuable. Complex anthropomorphic computer phantoms (such as the XCAT phantom) 4 are available to simulate time-varying activity distributions in the patient, complete with respiratory motion, cardiac contraction and myocardial defects. Coupling these with an accurate model of the camera itself, Monte Carlo simulation (e.g.…”