The 4D extended cardiac-torso (XCAT) phantom is developed for multimodality imaging research. It provides highly detailed whole-body anatomies for adult males and females based on segmentation of the Visible Human anatomical datasets and patient data. The anatomies are transformed to match body measurements and organ volumes for a 50th percentile male and female using the PEOPLESIZE program and ICRP Publication 89. The XCAT includes parametrized models for cardiac and respiratory motions based on high-resolution imaging data. The phantom can simulate realistic imaging data for PET, SPECT, and CT using publicly available simulation packages. The 4D XCAT can produce realistic imaging data with accurate models of the imaging process, allowing for the simulation of various anatomies, cardiac or respiratory motions, and spatial resolutions. The XCAT serves as a standard template for modeling anatomical variations and provides realistic, predictive 3D and 4D imaging data for normal and abnormal patients. It is a valuable tool for evaluating and improving imaging devices and techniques. The XCAT is applicable to a wide range of medical imaging applications, including high-resolution imaging modalities such as x-ray CT and MRI. The phantom can be used for dual modality imaging systems such as SPECT-CT or PET-CT. The XCAT can simulate realistic 3D and 4D multimodality imaging data, demonstrating its potential in imaging research. The XCAT can also produce more realistic simulated 4D imaging data with improved anatomical detail. The phantom can be used to study the effects of motion on medical imaging and to develop compensation methods for these effects. The XCAT has the flexibility to simulate any number of anatomically diverse subjects through user-defined parameters. It can provide a vital tool to investigate the effect of anatomy in CT imaging. The XCAT can be used to study various scanning parameters and their effects on anatomically variable subjects. The XCAT can also be used to develop patient-specific imaging protocols to reduce radiation dose while maintaining diagnostic image quality. The XCAT can provide a foundation for optimizing clinical CT applications to achieve the highest possible image quality with the minimum possible radiation dose. The XCAT can be used to study the effects of acquisition parameters, physical processes, and patient anatomy and motion within simulated images. The XCAT can be used to assess the trade-off between image quality and radiation dose. The XCAT can be used to study anatomical variations in health and disease and to simulate different compression states of the breast for various imaging modalities. The XCAT provides an important tool in multimodality imaging research to evaluate and compare imaging devices and techniques. It can be used to determine the best methods or combination of methods for patient diagnosis and treatment. The XCAT can be used to develop finite-element-based techniques for simulating different compression states of the breast for various imaging modalities. The XCAT can be used to study anatomical variations beyond the Visible Human adults byThe 4D extended cardiac-torso (XCAT) phantom is developed for multimodality imaging research. It provides highly detailed whole-body anatomies for adult males and females based on segmentation of the Visible Human anatomical datasets and patient data. The anatomies are transformed to match body measurements and organ volumes for a 50th percentile male and female using the PEOPLESIZE program and ICRP Publication 89. The XCAT includes parametrized models for cardiac and respiratory motions based on high-resolution imaging data. The phantom can simulate realistic imaging data for PET, SPECT, and CT using publicly available simulation packages. The 4D XCAT can produce realistic imaging data with accurate models of the imaging process, allowing for the simulation of various anatomies, cardiac or respiratory motions, and spatial resolutions. The XCAT serves as a standard template for modeling anatomical variations and provides realistic, predictive 3D and 4D imaging data for normal and abnormal patients. It is a valuable tool for evaluating and improving imaging devices and techniques. The XCAT is applicable to a wide range of medical imaging applications, including high-resolution imaging modalities such as x-ray CT and MRI. The phantom can be used for dual modality imaging systems such as SPECT-CT or PET-CT. The XCAT can simulate realistic 3D and 4D multimodality imaging data, demonstrating its potential in imaging research. The XCAT can also produce more realistic simulated 4D imaging data with improved anatomical detail. The phantom can be used to study the effects of motion on medical imaging and to develop compensation methods for these effects. The XCAT has the flexibility to simulate any number of anatomically diverse subjects through user-defined parameters. It can provide a vital tool to investigate the effect of anatomy in CT imaging. The XCAT can be used to study various scanning parameters and their effects on anatomically variable subjects. The XCAT can also be used to develop patient-specific imaging protocols to reduce radiation dose while maintaining diagnostic image quality. The XCAT can provide a foundation for optimizing clinical CT applications to achieve the highest possible image quality with the minimum possible radiation dose. The XCAT can be used to study the effects of acquisition parameters, physical processes, and patient anatomy and motion within simulated images. The XCAT can be used to assess the trade-off between image quality and radiation dose. The XCAT can be used to study anatomical variations in health and disease and to simulate different compression states of the breast for various imaging modalities. The XCAT provides an important tool in multimodality imaging research to evaluate and compare imaging devices and techniques. It can be used to determine the best methods or combination of methods for patient diagnosis and treatment. The XCAT can be used to develop finite-element-based techniques for simulating different compression states of the breast for various imaging modalities. The XCAT can be used to study anatomical variations beyond the Visible Human adults by