Clinical application of MOSkin dosimeters to rectal wall in vivo dosimetry in gynecological HDR brachytherapy
RIS ID
114206
Abstract
Introduction
MOSkins are MOSFET dosimeters designed and developed at the Centre for Medical Radiation Physics (University of Wollongong, Australia), optimized to measure the dose in steep dose gradients. In this work, their clinical application to rectal wall in vivo dosimetry (IVD) during gynecological and prostate high dose rate brachytherapy (HDR-BT) was studied.
Purpose
To evaluate the discrepancies between planned and measured doses to the rectal wall and to investigate the impact of the duration of the treatment planning procedure on these discrepancies.
Materials and methods
In gynecological HDR-BT, three MOSkins were assembled over a semi-flexible rectal probe and 51 IVD measurements were performed. In prostate HDR-BT, two MOSkins were assembled on the trans-rectal ultrasound probe and 36 IVD measurements were performed.
The absolute differences ΔD between measured and calculated doses in the estimated dosimeters positions were quantified and a possible correlation with the treatment planning time was investigated.
Results
Grouping ΔD according to the time elapsed between imaging and treatment (i.e., group 1: ⩽90 min; group 2: >90 min), average ΔD for groups 1 and 2 were 5.1 ± 3.0% and 8.3 ± 6.2% for prostate and 3.8 ± 3.5% and 6.5 ± 4.3% for gynecology HDR-BT, respectively. Average ΔD were in both cases lower for group 1, demonstrating higher uncertainties of the calculated dose with higher treatment planning times (i.e., probability of morphological changes increases with time).
Conclusion
MOSkin dosimeters coupled to rectal probes may be used for rectal IVD during gynecological/prostate HDR-BT. Planning time should be kept as low as possible to reduce uncertainties in calculated doses.
Publication Details
Carrara, M., Romanyukha, A., Tenconi, C., Mazzeo, D., Cerrotta, A., Borroni, M., Cutajar, D., Petasecca, M., Lerch, M., Bucci, J., Richetti, A., Presilla, S., Fallai, C., Gambarini, G., Pignoli, E. & Rosenfeld, A. (2017). Clinical application of MOSkin dosimeters to rectal wall in vivo dosimetry in gynecological HDR brachytherapy. Physica Medica: an international journal devoted to the applications of physics to medicine and biology, 41 5-12.