Source strength verification and quality assurance of preloaded brachytherapy needles using a CMOS flat panel detector. Issue 6 (30th November 2016)

• Record Type: Journal Article
• Authors: Golshan, Maryam; Spadinger, Ingrid; Chng, Nick
• Is Part Of: Medical physics. Volume 43:Issue 6(2016)
• Page Start: 3008
• Page End: 3018
• Publication Date: 2016-11-30
• Subjects: brachytherapy -- calibration -- CMOS integrated circuits -- diagnostic radiography -- dosimetry -- needles -- quality assurance; Quality assurance in radiotherapy -- Standards and calibration -- Dosimetry/exposure assessment -- Dose‐volume analysis -- Radiography; Radiation therapy -- Testing or calibrating of apparatus or arrangements provided for in groups G01D1/00 to G01D15/00 -- Biological material, e.g. blood, urine; Haemocytometers -- Calibrating of instruments or apparatus -- Scintigraphy; quality assurance -- brachytherapy -- flat panel detector -- preloaded needle; Image sensors -- Medical imaging -- Calibration -- Collimators -- Brachytherapy -- Image detection systems -- Dosimetry -- Image analysis -- Error analysis -- X‐ray detectors; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4950712
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: Current methods of low dose rate brachytherapy source strength verification for sources preloaded into needles consist of either assaying a small number of seeds from a separate sample belonging to the same lot used to load the needles or performing batch assays of a subset of the preloaded seed trains. Both of these methods are cumbersome and have the limitations inherent to sampling. The purpose of this work was to investigate an alternative approach that uses an image‐based, autoradiographic system capable of the rapid and complete assay of all sources without compromising sterility. Methods: The system consists of a flat panel image detector, an autoclavable needle holder, and software to analyze the detected signals. The needle holder was designed to maintain a fixed vertical spacing between the needles and the image detector, and to collimate the emissions from each seed. It also provides a sterile barrier between the needles and the imager. The image detector has a sufficiently large image capture area to allow several needles to be analyzed simultaneously.Several tests were performed to assess the accuracy and reproducibility of source strengths obtained using this system. Three different seed models (Oncura 6711 and 9011 125 I seeds, and IsoAid Advantage 103 Pd seeds) were used in the evaluations. Seeds were loaded into trains with at least 1 cm spacing. Results: Using our system, it was possible to obtain linear calibration curves with coverage factor k = 1 prediction intervals of less than ±2% near the centre of their range for the three source models. The uncertainty budget calculated from a combination of type A and type B estimates of potential sources of error was somewhat larger, yielding ( k = 1) combined uncertainties for individual seed readings of 6.2% for 125 I 6711 seeds, 4.7% for 125 I 9011 seeds, and 11.0% for Advantage 103 Pd seeds. Conclusions: This study showed that a flat panel detector dosimetry system is a viable option for source strength verification in preloaded needles, as it is capable of measuring all of the sources intended for implantation. Such a system has the potential to directly and efficiently estimate individual source strengths, the overall mean source strength, and the positions within the seed‐spacer train.