NCS Report 30: Code of Practice for Quality Assurance of Brachytherapy with Ir-192 Afterloaders

Steenhuizen, J.; Harbers, M.; Hoffmann, A.; Leeuw, Astrid de; Rijnders, A.; Unipan, Mirko

doi:10.25030/ncs-030

Cited by 7 publications

(8 citation statements)

References 27 publications

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“…Some articles suggested that applicator geometries may not always be consistent, 15 but the vendor's source paths are based on averaged coordinates over several samples, and in general the related uncertainty -including measurement uncertainty-is noted to be small (sub-millimeter). 56,58 Several studies and guidelines have advocated for individual applicator commissioning, 3,12,15,16 based on measurements with maximum deviations of several millimeters with manufacturer-measured source paths. For this purpose several types of applicator commissioning methodologies have been proposed in literature.…”

Section: Discussionmentioning

confidence: 99%

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Multibody dynamic modeling of the behavior of flexible instruments used in cervical cancer brachytherapy

Straathof,

Meijaard,

van Vliet‐Pérez

et al. 2024

Medical Physics

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BackgroundThe steep radiation dose gradients in cervical cancer brachytherapy (BT) necessitate a thorough understanding of the behavior of afterloader source cables or needles in the curved channels of (patient‐tailored) applicators.PurposeThe purpose of this study is to develop and validate computer models to simulate: (1) BT source positions, and (2) insertion forces of needles in curved applicator channels. The methodology presented can be used to improve the knowledge of instrument behavior in current applicators and aid the development of novel (3D‐printed) BT applicators.MethodsFor the computer models, BT instruments were discretized in finite elements. Simulations were performed in SPACAR by formulating nodal contact force and motion input models and specifying the instruments’ kinematic and dynamic properties. To evaluate the source cable model, simulated source paths in ring applicators were compared with manufacturer‐measured source paths. The impact of discrepancies on the dosimetry was estimated for standard plans. To validate needle models, simulated needle insertion forces in curved channels with varying curvature, torsion, and clearance, were compared with force measurements in dedicated 3D‐printed templates.ResultsComparison of simulated with manufacturer‐measured source positions showed 0.5–1.2 mm median and <2.0 mm maximum differences, in all but one applicator geometry. The resulting maximum relative dose differences at the lateral surface and at 5 mm depth were 5.5% and 4.7%, respectively. Simulated insertion forces for BT needles in curved channels accurately resembled the forces experimentally obtained by including experimental uncertainties in the simulation.ConclusionThe models developed can accurately predict source positions and insertion forces in BT applicators. Insights from these models can aid novel applicator design with improved motion and force transmission of BT instruments, and contribute to the estimation of overall treatment precision. The methodology presented can be extended to study other applicator geometries, flexible instruments, and afterloading systems.

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Section: Discussionmentioning

confidence: 99%

“…13 Furthermore, "snaking" occurs when the source cable curls in the lumen as the result of friction or obstruction along the channel (Figure 1b). 12 Snaking also results in axial source path deviations. In multiple studies, geometric variations associated with these effects have been quantified.…”

Section: Related Workmentioning

confidence: 99%

Multibody dynamic modeling of the behavior of flexible instruments used in cervical cancer brachytherapy

Straathof,

Meijaard,

van Vliet‐Pérez

et al. 2024

Medical Physics

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“…based on a set of dynamic tests that have been recommended by the NCS CoP Report 24. 8 The system characterized with high spatial and temporal resolution demonstrated the capability to provide independent verification of dose rate, gantry speed and MLC leaf speed with high precision in both flattened and unflattened beams and with good agreement to the machine log files.…”

mentioning

confidence: 92%

“…However, due to difficulties related to film dosimetry and portal images, the delivery aspects of VMAT could not be assessed separately and with sufficient gantry-angle resolution. The NCS Code of Practice (CoP) Report 24 8 published in 2015 outlines guidelines for the commissioning and QA of VMAT using multiple machine-independent dosimetry systems. The CoP suggests that understanding the dynamic behavior of VMAT is best achieved by assessing the linac's dynamic components both individually and collectively and as a function of gantry angle.…”

Section: Introductionmentioning

confidence: 99%

Quality assurance of VMAT on flattened and flattening filter‐free accelerators using a high spatial resolution detector

Matar

Wilkinson

Davis

et al. 2020

J Applied Clin Med Phys

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Purpose: This study investigated the use of high spatial resolution solid-state detectors (DUO and Octa) combined with an inclinometer for machine-based quality assurance (QA) of Volumetric Modulated Arc Therapy (VMAT) with flattened and flattening filter-free beams. Method: The proposed system was inserted in the accessory tray of the gantry head of a Varian 21iX Clinac and a Truebeam linear accelerator. Mutual dependence of the dose rate (DR) and gantry speed (GS) was assessed using the standard Varian customer acceptance plan (CAP). The multi-leaf collimator (MLC) leaf speed was evaluated under static gantry conditions in directions parallel and orthogonal to gravity as well as under dynamic gantry conditions. Measurements were compared to machine log files. Results: DR and GS as a function of gantry angle were reconstructed using the DUO/inclinometer and in agreement to within 1% with the machine log files in the sectors of constant DR and GS. The MLC leaf speeds agreed with the nominal speeds and those extracted from the machine log files to within 0.03 cm s −1. The effect of gravity on the leaf motion was only observed when the leaves traveled faster than the nominal maximum velocity stated by the vendor. Under dynamic gantry conditions, MLC leaf speeds ranging between 0.33 and 1.42 cm s −1 were evaluated. Comparing the average MLC leaf speeds with the machine log files found differences between 0.9% and 5.7%, with the largest discrepancy occurring under conditions of fastest leaf velocity, lowest DR and lowest detector signal. Conclusions: The investigation on the use of solid-state detectors in combination with an inclinometer has demonstrated the capability to provide efficient and independent verification of DR, GS, and MLC leaf speed during dynamic VMAT delivery. Good agreement with machine log files suggests the detector/inclinometer system is a useful tool for machine-specific VMAT QA.

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“…59 Report issued by the AAPM recommends which QA checks and how often they should be performed (Kubo et al 1998). Some countries have their national guidelines (Frenière 2018, Steenhujsen et al 2018 and there is also a practical guide issued by the European Society for Therapeutic Radiology and Oncology (Venselaar and Pérez-Calatayud 2004). The programs are similar and cover mechanical checks, software checks, radiation safety checks, but none of them encompass the entire treatment delivery chain to determine absorbed dose to water experimentally and independently from TPS calculations.…”

Section: In-phantom Quality Assurance Of 192 Ir Remote Afterloading Unitsmentioning

confidence: 99%

Development of Experimental Brachytherapy Dosimetry Using Monte Carlo Simulations for Detector Characterization

Kaveckyte

2021

Linköping University Medical Dissertations

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Brachytherapy (BT) is advantageous due to high absorbed dose conformity and possibility to deliver high dose in few fractions. It is often used for prostate and gynecological tumors as monotherapy or as a boost alongside external beam radiotherapy (EBRT). However, a number of things can compromise treatment delivery, starting from incorrect source data in a treatment planning system to malfunctioning of a treatment delivery unit. The established quality assurance (QA) covers individual aspects, such as software checks of absorbed dose calculations, mechanical checks, source dosimetry. None of them emulate treatment delivery where the planned dose could be compared with the experimentally determined values. While such practices are employed in EBRT, BT suffers from the lack of detectors that would be water-equivalent and convenient to use for regular measurements. First-choice thermoluminescence dosimeters are water-equivalent but have passive readout. Sporadic attempts to use other detectors have not led to any established practices at clinical sites. Stepping ahead, the safety of treatment delivery could be further evaluated using real-time in vivo dosimetry. If detectors were characterized with high accuracy, a reliable error detection level could be set to terminate treatments if needed. Contrary to the inphantom QA, there are detectors suitable for such applications, but their characterization is incomplete. In this thesis we address both problems.Focusing on high-dose-rate 192 Ir remote afterloading treatments, which are among the most common in BT, we investigate and propose a direct readout synthetic diamond detector for the in-phantom QA of treatment units. The detector was designed for small-field highenergy EBRT dosimetry, but our findings demonstrate its suitability for BT dosimetry. Additionally, due to the detector calibration with traceability to primary standards of absorbed dose to water of high-energy EBRT and a combination of experimental and Monte Carlo (MC) characterization, the uncertainties in the determined absorbed dose to water values were comparable to or lower than for other detectors used in BT. We complemented the investigation with a theoretical study on diamond material properties and which values (mass density, mean excitation energy, number of conduction electrons per atom) shall be used for the most faithful description of ionizing radiation interactions in diamond for MC simulations and calculations of mass electronic stopping power. The findings improve diamond dosimetry accuracy not only in BT but also in EBRT where the detectors are used.

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NCS Report 30: Code of Practice for Quality Assurance of Brachytherapy with Ir-192 Afterloaders

Cited by 7 publications

References 27 publications

Multibody dynamic modeling of the behavior of flexible instruments used in cervical cancer brachytherapy

Multibody dynamic modeling of the behavior of flexible instruments used in cervical cancer brachytherapy

Quality assurance of VMAT on flattened and flattening filter‐free accelerators using a high spatial resolution detector

Development of Experimental Brachytherapy Dosimetry Using Monte Carlo Simulations for Detector Characterization

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