Room: ePoster Forums
Purpose: Determination of the PSD is an essential task for proper management of patients who have been exposed to significant levels of radiation from FGIPs. With the advent of patient dose tracking and a standardized dose reporting structure the authors evaluate the effects of geometric acquisition parameters on calculating the PSD.
Methods: PSD estimations were performed on 15 patients who exceeded a substantial radiation dose level over 5Gy within a six-month period. The patients were all examined on equipment capable of producing a Radiation Dose Structure Report (RDSR). The RDSR data was reconstructed in a tabular format. PSD estimates were calculated and compared using the following methods labeled 1 through 4: 1. Cumulative Air Kerma Reading (CAKR) at the International Reference Point 2. CAKR but accounting for back scatter, vertical table position (VTP), table attenuation, and the tissue-air f-factor 3. Use of Method 2 and adjustments for range of primary and secondary acquisition angles 4. Use of Method 3 but inclusion of patient morphometry, 3D table position, and beam entry overlap. All patients in this study had undergone a CT study to the region that was being considered. Patient morphometry information was obtained from the CT image.
Results: All of the calculations and modeling were performed in Microsoft Excel to demonstrate the feasibility of use. The PSD is more frequently overestimated when using methods 1 and 2. Accounting for angulation, lateral and longitudinal position demonstrated a more accurate PSD estimate. A majority of the PSD estimates showed the effect VTP was minimal.
Conclusion: Including geometric RDSR parameters in the PSD calculation results in a more realistic dose estimate to the performing physician who manages patient care. These calculations also demonstrate to the performing physicians the importance of angulating the tube and moving the table.