Abstract: Reduced dose megavoltage CT images are obtained using low flux data resulting from leakage through modulating shutters and/or collected by other means and augmented by incomplete high flux data collected during radiation therapy. The ability to construct tomographic projection sets from significantly varying flux rate data is provided by the use of air scans windowed to account for variations in mechanical leaf movement. These methods are also provide a means of imaging the patient entirely during radiation therapy treatments without any additional scan time.

Abstract: A method of compensating for unexpected changes in the size, shape, and/or position of a patient in the delivery of radiation therapy. An image of a patient is used to prepare a treatment plan for the irradiation of a tumor or the like, shown in the image. A second image of a patient includes a visual representation of the tumor and sensitive structures wherein any combination of the size, shape, or position of the tumor or sensitive structures is different from any combination of the size, shape, or position of the visual representation of the tumor or sensitive structures in said first image. The radiation treatment is adjusted to more closely conform the treatment plan to the new size, shape, or position of the tumor as shown in said second image. This adjustment can occur before, during, or after the radiation delivery and can be used to define trade-offs that exist for the delivery.

Abstract: The present invention provides a system and method of using current but incomplete data to prepare an approximated complete image of a patient potentially undergoing radiation therapy. A limited patient image, such as that obtained from a CT scan is fused with a complete image of the same area using image registration techniques. The fused image is converted to sinogram data. This data is compared to sinogram data corresponding to the limited patient image to determine what data exists beyond the scope of the limited sinogram. Any additional data is added to the limited data sinogram to obtain a complete sinogram. This is reconstructed into an image that approximates the complete image that would have been taken at the time the limited image was obtained.