Real-time verification of HDR brachytherapy source location: implementation of detector redundancy

Abstract

Independent treatment verification for high dose rate (HDR) brachytherapy is needed to ensure that the treatment proceeds as prescribed. In this paper, we investigate the feasibility of a proposed real-time source position verification process. This process provides immediate confirmation of the source position during the treatment, so that the treatment can be aborted and modified if necessary. We show that an array of dosimeters placed on the patient's skin can independently verify the position in three dimensions. This verification was demonstrated by using a diamond detector placed in several locations on the surface of an anthropomorphic phantom. A mathematical algorithm was constructed to estimate the location of the source given a measured data set in the presence of tissue heterogeneity. The accuracy of the source localization was found to increase with the number of detectors used to compute the estimation of the source position. The resolution to which the 12 detectors can identify the location of the source was within 3 mm.

Time‐resolved in vivo luminescence dosimetry for online error detection in pulsed dose‐rate brachytherapy

“…The ability of in vivo dosimetry to actually detect errors therefore greatly depends on where the detector probes can be placed and how well these positions are known. In line with this, Nakano et al 17 conducted a phantom study that addressed the feasibility of dose verification directly based on estimates of HDR brachytherapy source positions derived from measurements with an array of diamond detectors placed on the surface of the skin. Time-resolved dosimetry is needed for the assessment of the dose rate for individual dwell positions.…”

“…This would enable the possibility of an immediate termination of treatment in case of significant deviations. 17 The relevance of real-time dose verification seems particularly pronounced for HDR and PDR brachytherapies since the treatment is typically delivered in a few fractions with a high dose per fraction. Furthermore, PDR brachytherapy typically requires an overall treatment time of 10-50 h per fraction, and most of the treatment is therefore carried out automatically without direct presence of hospital personnel neither in the brachytherapy control room nor with the patient.…”

In vivodosimetry: trends and prospects for brachytherapy

“…20 fitted functions of the detector reading with respect to the source-to-detector distance, 86 fitting of Lorentz class functions to measured dose profiles 100 and specific image reconstruction techniques for pinhole cameras. 88 Nakano et al, 99 demonstrated that the redundancy of dosimetry points increases the source localization accuracy.…”

“…For instance, Nakano et al 86,99 have suggested methods for backscatter and tissue heterogeneity corrections using multiple dosemeter points, which could be relevant if the dosemeter probe had been calibrated under irradiation conditions significantly different from the in vivo scenario.…”

Verification of High Dose Rate $^{192}$Ir Source Position During Brachytherapy Treatment Using Silicon Pixel Detectors

“…Authors in [7] describe reconstruction of source location from comparison of dose rate measurements in a set of three diamond dosimeters placed at distance from the source. In [8] the authors propose improvement of the method by using 12 detectors to increase the accuracy of source localization. The reported accuracy, calculated from detectors response per minute, is around 2.5 mm.…”