(Wednesday, 8/1/2018) 7:30 AM - 9:30 AM
Room: Karl Dean Ballroom B1
Purpose: Cherenkov signals were generated in patients treated with TSET, thus the reflected signal can be recorded in-real time to monitor the dose distribution on patient body surface during the treatment.
Methods: The TSE (full and partial body) patients were treated in Stanford technique at 500 cm source to patient midplane distance using dual-fields at gantry angles 16° above and below horizontal at 6 postures with 6 MeV HDTSE mode delivered by Varian Truebeam. A time-gated intensified camera was used to capture the reflected Cherenkov signal generated from patient’s skin surface. In vivo diodes (IVD) and optically stimulated luminescent dosimeters (OSLDs) were taped to patient’s chest and umbilicus to record and verify the dose delivered to those locations. Perspective (geometrical) calibration was performed in 2-dimensions to correct the camera vignetting effect, lens correction and different pixel response. The ratio between chest and umbilicus from Cherenkov signal intensity were compared to the IVD and OSLD dose measurements. Then dose was also reconstructed from the Cherenkov imaging by normalizing intensity to the OSLD measurements at the same location.
Results: Perspective calibration was studied in 2D for Cherenkov imaging and applied to acquired patient data. The patient studies showed that Cherenkov agreed to within 5% for most of the patients compared to the in vivo dose measurements, except for patient 5 whose chest point falled in the dose gradient region due to lead blocks. The Cherenkov intensity can also be converted to dose by normalizing to OSLD measurements at the same location.
Conclusion: Cherenkov imaging provides valuable information about the dose distribution for TSET. Geometrical correction was established in 2D for Cherenkov imaging and dose distribution can be reconstructed from the Cherenkov imaging.
Keywords
Not Applicable / None Entered.
Taxonomy
TH- External beam- electrons: dose measurement
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