Program Information
A Novel Monolithic Silicon 2D Detector Array for Use in Stereotactic Applications
M Gargett1*, M Petasecca1 , B Oborn2,1 , S Alnaghy1 , A Rosenfeld1 , P Metcalfe1,3 , (1) Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia (2) Illawarra Cancer Care Centre, Wollongong, NSW, Australia (3) Liverpool Cancer Therapy Centre and Ingham Institute, NSW, Australia
Presentations
WE-AB-BRB-4 (Wednesday, July 15, 2015) 7:30 AM - 9:30 AM Room: Ballroom B
Purpose:To assess the capability of a novel 2D monolithic silicon detector array in measuring stereotactic photon fields.
Methods:The silicon array detector used in this work, named Magic Plate-512 (MP512), is a thin monolithic silicon wafer (52 x 52 x 0.47 mm³) with 512 ion-implanted diodes (0.5 x 0.5 mm²). Adjacent pixels are spaced evenly with 2 mm pitch, covering a maximum detection area 46 mm wide. Its fast, FPGA based read-out system is synchronised with the linac to allow readout of all pixels pulse-by-pulse. A clinical SABR lung plan (consisting of 9 single segment beams, 6MV) was measured with the array at 1.5 cm depth in a solid water phantom (100 cm SSD). The typical field size was in the range of 3 x 3 cm² to 4 x 4 cm². Each beam was delivered at perpendicular incidence to the detector plane so as to avoid the need for angular dependence corrections. The fields were measured under the same conditions using Gafchromic EBT3 film for comparison. The film was scanned at 72 dpi resolution, with the red channel data used for analysis.
Results:Average gamma passing rates of (92.3 ± 1.8) % for 2%/2mm criteria, and (86.6 ± 2.3) % for 1%/2mm criteria were achieved for MP512, using EBT3 film as the reference distribution. The detector array was able to accurately measure the full-width-at-half-maximum (FWHM), to within (0.77 ± 0.01) mm accuracy when compared to film. The penumbral widths (80%-20%) were measured to within (0.30 ± 0.01) mm accuracy to film.
Conclusion:The MP512 is a feasible option for measurement of stereotactic photon fields, with its high density of detection points making it useful for small field applications. The prototype array has demonstrated merit; in the future the development of a larger array detection area would be beneficial for clinical applications.
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