Prediction of Volumetric Data Errors in Patients Treated with Gamma Knife Radiosurgery

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Abstract
Purpose: Volumetry is the most commonly used method to measure tumor response in patients who receive Gamma Knife radiosurgery. We calculated the data errors in measurement made by different methods based on the stereotactic fiducials (Gamma Knife workstation), surface area multiplied by thickness (PACS), and product of maximum diameter in x, y, and z dimensions (geometric method) to more precisely evaluate tumor response in patients treated with Gamma Knife radiosurgery. Materials and Methods: From 2003 to 2006, 210 tumors were enrolled in this study. MRIs obtained from these patients were transferred to Gamma Knife and PACS workstations. Data errors were defined as the difference between the volume calculated by various methods and the Gamma Knife workstation divided by the volume obtained from the Gamma Knife workstation. Linear regression was used for data analysis. Results: There were 27 lesions with volume 0.5 cm3) demonstrated strong linear correlation. In tumors with volume less than 0.5 cm3, the most reliable method was the geometric method. When using the PACS system in the evaluation of tumor response, a data error as high as 21% should be considered.