In vivodosimetry in the urethra using alanine/ESR during¹⁹²Ir HDR brachytherapy of prostate cancer—a phantom study

Abstract

A phantom study for dosimetry in the urethra using alanine/ESR during (192)Ir HDR brachytherapy of prostate cancer is presented. The measurement method of the secondary standard of the Physikalisch-Technische Bundesanstalt had to be slightly modified in order to be able to measure inside a Foley catheter. The absorbed dose to water response of the alanine dosimetry system to (192)Ir was determined with a reproducibility of 1.8% relative to (60)Co. The resulting uncertainty for measurements inside the urethra was estimated to be 3.6%, excluding the uncertainty of the dose rate constant Lambda. The applied dose calculated by a treatment planning system is compared to the measured dose for a small series of (192)Ir HDR irradiations in a gel phantom. The differences between the measured and applied dose are well within the limits of uncertainty. Therefore, the method is considered to be suitable for measurements in vivo.

Physics-aspects of dose accuracy in high dose rate (HDR) brachytherapy: source dosimetry, treatment planning, equipment performance and in vivo verification techniques

“…Anton et al . (2009) [109] have conducted a prostate phantom study to demonstrate the potential of alanine/ESR as an in vivo dosimeter with an Ir-192 source. The uncertainty of measurement within a Foley catheter for dose measurements within the urethra was estimated to be 3.6%, concluding this to be suitable for clinical in vivo measurements.…”

Clinical Trials of a Urethral Dose Measurement System in Brachytherapy Using Scintillation Detectors

“…To calibrate each dosimeter, the scintillator was placed in a groove at the center of a 300 Â 300 Â 50 mm Solid Water slab, and the 192 Ir source was positioned 50 mm directly below the scintillator to provide full scatter conditions (10). This separation between the source and scintillator was chosen because a positional error of 0.5 mm would result in a change of only 2% in dose rate.…”

“…After correction, the mean dosimeter readings were within 10% of the Monte Carlo calculations AE8.6 % and AE10.8 % for R and K type MOSFETs, respectively. Recent work using in vivo alanine/electron spin resonance dosimetry for urethral dosimetry HDR brachytherapy has also been suggested, with promising phantom results (10).…”

In vivo real‐time dosimetric verification in high dose rate prostate brachytherapy

“…Dosimeters that have been used previously or have had their feasibility demonstrated include thermoluminescent dosimeters (TLDs), radiophotoluminescent glass dosimeters (RPLGDs), diamond detectors, semiconductors, scintillators, alanine dosimeters, and metal oxide semiconductor field effect transistors (MOSFETs). [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] A study incorporating TLD rods was performed by Das et al 4 where urethral and rectal dose measurements were performed for 50 patients undergoing a HDRB boost for treatment of prostate cancer. They found overall that the rectal readings have significantly more variability than the urethral measurements, which could be attributed to the possible movement of the catheter containing the detectors within the rectum between acquisition of planning images and treatment delivery.…”

“…A study incorporating the development of alanine detectors for dose verification in HDRB for prostate cancer was undertaken by Anton et al 11 where the measurement device was placed inside a Foley catheter inside the urethra of a prostate phantom. The agreement between the measured and planned dose points investigated was well within the relative standard measurement uncertainty of 3.6% with the method, therefore, deemed suitable for in vivo measurements.…”