(Monday, 7/15/2019) 1:15 PM - 1:45 PM
Room: Exhibit Hall | Forum 4
Purpose: To evaluate a high spatial resolution 2D detector array for SRS patient specific QA in comparison with GafChromic film and a diamond detector.
Methods: Ten cases of single isocenter SRS plans involving 1 to 12 targets were evaluated with SRS MapCHECK (SRSMC) (Sun Nuclear Corporation, Melbourne, FL) for SRS patient specific QA in comparison with GafChromic film dosimetry and point dose measurement with a MicroDiamond Detector (PTW, Freiburg, Germany). SRSMC provides a 2D array of detectors with 2.47 mm spacing. Absolute dose (AD) at target center represented by the mean dose of a 5mm diameter circular ROI for film dosimetry and the average of the center detectors for SRSMC was compared to the measurement with a MicroDiamond Detector. 2D dose distributions were evaluated by gamma analysis with criteria of 1mm/3% AD and 1mm/2% relative dose (dose scaled for maximum gamma pass rate). The results were compared between the SRSMC and film dosimetry.
Results: The results of the three dosimeters agreed reasonably well. For absolute dose at target center, the mean difference between SRSMC and film was 0.79% (-0.82% to 1.91%) and between SRSMC and diamond detector was 1.02% (-0.38% to 2.50%). Dose distributions on the central coronal plane were compared between SRSMC and film. The mean gamma pass rates for SRSMC and films were 99.27% and 93.65% with a criterion of 1mm/3% AD, and 97.60% and 94.57% with a criterion of 1mm/2% relative dose, respectively. SRSMC is much more efficient, effective and stable for 2D dose measurement and analysis compared to film dosimetry.
Conclusion: Absolute dose and 2D dose distribution measured with SRSMC are consistent with those of film dosimetry and point dose measurement with a diamond detector. SRSMC provides an effective solution to high spatial resolution 2D dose evaluation for SRS patient specific QA.
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