Proposed protocol for internal dosimetry using patient-specific attenuation-corrected spect scans

• Main Author: Hannis, Leah
• Format: Others
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/9395

The Medical Internal Radiation Dose (MIRD) protocol has provided a solid foundation over the years for calculating the internal absorbed dose but as for providing an assessment that is specific to the individual patient's organ/tumor anatomy, it falls short. Various methods have been proposed to overcome the shortcomings of the MIRD protocol, but each has its own limitations. Quantitative SPECT proves to be the most desirable option for determining dose estimates, yet the prolonged scan times prevent SPECT from becoming a clinical protocol in dosimetry. Given the time constraints of clinical SPECT, planar quantitative imaging has proved a popular choice for dosimetry studies, but the resulting dose overestimates may prevent maximum therapy from being achieved. Proposed here is a protocol that contends to be clinically feasible, patient-specific, and promising in its results. This protocol combines the benefits of both quantitative planar and SPECT imaging. By maintaining the majority of scans as planar yet incorporating the benefits of attenuation corrected SPECT scans, a more accurate, yet attainable clinical protocol can be achieved. The 2 or more SPECT scans suggested make use of a Gadolinium-153 transmission source so that a simultaneous emission/transmission scan provide a patient-specific, attenuation corrected SPECT image. The SPECT data is then used to constrain the planar data, resulting in a more accurate dose estimate than would arise from planar alone. Phantom experiments demonstrate that the errors in absorbed dose estimates have improved from an average of 159% for planar methods alone to 14% by the addition of a SPECT constraint. === Science, Faculty of === Physics and Astronomy, Department of === Graduate