Ir-192 Calibration in Air with Farmer Chamber for HDR Brachytherapy

Abstract

A comprehensive review for the in-air calibration of an Ir-192 high-dose-rate brachytherapy source in terms of air kerma strength (AKS) and reference air kerma rate (RAKR) using the Farmer chamber was conducted. The reviewed calibration methods include the National Physical Laboratory (NPL) calibration standard in the UK, the 7-distance technique with the standard calibration of the National Institute of Standards and Technology and Accredited Dosimetry Calibration Laboratory in the US, the calibration conducted in Australia following recommendations of the International Atomic Energy Agency with the chamber primarily calibrated by the Australian Radiation Protection and Nuclear Safety Agency, the calibration conducted in India following the Deutsche Gesellschaft fur Medizinische Physik recommendation, and the convenient empirical method used in Taiwan. The calibrated AKS (or RAKR) and uncertainty obtained using Farmer chambers are similar to those obtained using well chambers. All reported differences (between measurements obtained using Farmer and well chambers, respectively) and uncertainties (k = 2) were generally less than 1.5 and 2.5 %, respectively. The standard uncertainty of the NPL calibration is approximately half that of all the other proposed approaches, and may become the gold standard calibration procedure. Almost all techniques follow the 7-distance technique basis; however, the services at NPL can calibrate the source with lower uncertainty. Users can calibrate the Ir-192 source more conveniently using the empirical method with only one source-chamber distance.

Retrospective Analysis of Treatment Time Calculation Agreement Between TPS and Manual Method and Source Strength Verification for 13 HDR Ir-192 Sources In Flexitron Brachytherapy Unit: A Single Institute Experience

“…At our institute the HDR brachytherapy unit named Flexitron (Nucletron, Mallinckrodt Medical B.V., The Netherland originally from Isodose Control now known as Elekta Medical Systems) having a maximum source capacity of 12 Ci (442GBq) for Iridium-192 was installed/commissioned and was first used for patient treatment on 28.07.2011. Frequent source replacement after every 4-5 months requires for Ir-192 source due to its short half-life (73.84-74days) [16][17]. In brachytherapy the accurate execution of planned dose depends upon several factors such as properly calibrated dose measuring equipment, measurement set up, agreement between TPS and manual treatment time calculation, the methodology adopted to measure the RAKR and correct entry of source specific data into TPS.…”

3D printed brachytherapy jig for Reference Air Kerma Rate calibration

“…This test was performed by comparing scatter correction factors calculated with and without inclusion of jig scatter effects. A scatter correction without jig effects was calculated using Chang et al's empirical scatter estimate [15,16], which assumes that scatter comes from the surfaces bounding the room in which the measurement is made (walls, ceiling, floor) and therefore relies on the room dimensions to calculate the scatter correction. Scatter corrections that take jig scatter into account (along with wall, ceiling, floor and other sources of scatter in the room) were evaluated using physical measurements at several set distances from the source.…”

“…Having completed the in-house evaluation of jig scatter effects described in the previous section, scatter corrections were calculated for all data sets using Chang et al's empirical scatter estimate [15,16], using dimensions for each treatment room.…”

Study the Calibration of the High Dose Rate Brachytherapy Radioactive Source 60Co

“…In this calibration technique known as In-air measurement technique, we need a strategy for adjusting a 'high-vitality' photon source utilizing an in-air alignment system [15]. This technique is not very useful for 125 I or 103 Pd because of their being discharged a low vitality of the photons from these radioactive sources.…”