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Enhancement of SRS Patient QA Via 3D Dose Reconstruction From Multiple 2D Planar Measurements

O Fasina*, J Duan, F Yin, G Cui, Duke University, Durham, NC


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library


To enhance SRS patient QA by 3D dose reconstruction from multiple 2D measurements using a high-resolution 2D detector array.


A 2D detector array, SRS MapCHECK (SRSMC) (Sun Nuclear Corporation, Melbourne, FL) was used to take the measurements. It has an array size of 7.7 x 7.7 cm2 including 1013 diode detectors, providing high resolution with 2.47 mm detector spacing. The SRSMC was inserted into a cylindrical phantom during the patient QA plan delivery. An SRS plan was delivered four times by rotating the detector array in 45° increments (0°, 45°, 90° and 135°) along the longitudinal axis of the cylindrical phantom.

A cylindrical geometry-based Beizer interpolation method was utilized to generate the measured 3D dose distribution from these four 2D planar measurements. Two-dimensional planar data at 30°, 60°, and 120° from the treatment planning system (TPS) were used to validate the interpolated measured data. The mean and max doses averaged over these angles for three regions, high, gradient and total dose regions were compared. Axial and sagittal slices at isocenter extracted from the 3D reconstructed dose were compared with axial and sagittal slices at isocenter from the TPS.


The mean percent difference for high, gradient, and total regions were 2.70%, 3.38%, and 2.83%, respectively. The max percent difference for high, gradient, and total regions were 8.46%, 6.90%, and 8.58%, respectively. The percent difference between the axial and sagittal slices from the 3D dose reconstruction and TPS at isocenter were 6.032% and 0.380%, respectively.


2D planar dose validation results demonstrated the potential in 3D dose comparison for the enhancement of SRS patient QA. The novelty of using 3D reconstructed Volumetric Dose to compare Axial and Sagittal slices is a precursor for expansion of SRS QA from planar dose to Volumetric Dose comparison metrics, thus enhancing SRS QA.


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