Technical note: TROG 15.01 SPARK trial multi‐institutional imaging dose measurement

Abstract

PurposeThe Trans‐Tasman Radiation Oncology Group (TROG) 15.01 Stereotactic Prostate Adaptive Radiotherapy utilizing Kilovoltage intrafraction monitoring (SPARK) trial is a multicenter trial using Kilovoltage Intrafraction Monitoring (KIM) to monitor prostate position during the delivery of prostate radiation therapy. KIM increases the accuracy of prostate radiation therapy treatments and allows for hypofractionation. However, an additional imaging dose is delivered to the patient. A standardized procedure to determine the imaging dose per frame delivered using KIM was developed and applied at four radiation therapy centers on three different types of linear accelerator.MethodsDose per frame for kilovoltage imaging in fluoroscopy mode was measured in air at isocenter using an ion chamber. Beam quality and dose were determined for a Varian Clinac iX linear accelerator, a Varian Trilogy, four Varian Truebeams and one Elekta Synergy at four different radiation therapy centers. The imaging parameters used on the Varian machines were 125 kV, 80 mA, and 13 ms. The Elekta machine was measured at 120 kV, 80 mA, and 12 ms. Absorbed doses to the skin and the prostate for a typical SBRT prostate treatment length were estimated according to the IPEMB protocol.ResultsThe average dose per kV frame to the skin was 0.24 ± 0.03 mGy. The average estimated absorbed dose to the prostate for all five treatment fractions across all machines measured was 39.9 ± 2.6 mGy for 1 Hz imaging, 199.7 ± 13.2 mGy for 5 Hz imaging and 439.3 ± 29.0 mGy for 11 Hz imaging.ConclusionsAll machines measured agreed to within 20%. Additional dose to the prostate from using KIM is at most 1.3% of the prescribed dose of 36.25 Gy in five fractions delivered during the trial.

Estimation of patient-size dependent imaging dose for stereoscopic/monoscopic real-time kV image guidance in lung and prostate SBRT

“…Table 4 shows a comparison of results from previous studies on pelvis and thorax imaging dose using different real-time tumor monitoring technologies. The first two studies (Juneja et al 2016, Legge et al 2017 have reported the imaging dose for real-time tumor monitoring with Kilovoltage Intrafraction Monitoring (KIM) technology for lung IGRT and prostate IGRT respectively. They measured surface dose and absorbed dose to PTV following the Institution of Physics and Engineering in Medicine and Biology (IPEMB) protocol (IPEMB 1996).…”

Estimation of patient-specific imaging dose for real-time tumour monitoring in lung patients during respiratory-gated radiotherapy

“…The mean of estimated imaging doses for ipsilateral and contralateral lung, heart and spinal cord were 122 mGy, 56 mGy, 80 mGy and 65 mGy, respectively. Legge et al (2017) also measured the imaging dose in prostate patient using the same system. The estimated imaging doses to the prostate for all five treatment fractions were 39.9 ± 2.6 mGy for 1 Hz imaging, 199.7 ± 13.2 mGy for 5 Hz imaging and 439.3 ± 29 mGy for 11 Hz imaging.…”

Fully Textile X‐Ray Detectors Based on Fabric‐Embedded Perovskite Crystals

“…Flexible perovskite-based X-ray detectors have been less explored but, in the last years, the number of reports on their feasibility is rapidly growing. [35][36][37] The possibility of conforming ionizing radiation detectors and dosimeters onto a nonflat object is one of the primary desired features needed, for example, when detectors have to be integrated inside specific probes during radiation therapy, [38] or in easy-wearable objects (e.g., bracelets and belt) and for potential vignetting limitation. Recently, Zhao et al [39] proposed a highly sensitive and flexible direct X-ray detector based on a porous nylon membrane with metal halide perovskite loaded by the infiltration method.…”