Treatment verification in high dose rate brachytherapy using a realistic 3D printed head phantom and an imaging panel

Wagenberg, T. van; Fonseca, Gabriel Paiva; Voncken, Robert; Beveren, C. Van; Limbergen, Evert Van; Lutgens, Ludy; Vanneste, Ben; Berbée, Maaike; Reniers, Brigitte; Verhaegen, Frank

doi:10.1016/j.brachy.2022.11.012

Cited by 5 publications

(5 citation statements)

References 27 publications

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“…Several reports have noted the importance of error detection in brachytherapy. 22,23 While various technologies exist and have been proven to be effective, besides EMT also invivo dosimetry [34][35][36] and imaging panels, [37][38][39] very few of them are used in routine clinical workflows to date. For this reason, comprehensive knowledge about the prevalence of clinical treatment errors is still lacking.…”

Section: Discussionmentioning

confidence: 99%

Localization of reference points in electromagnetic tracking data and their application for treatment error detection in interstitial breast brachytherapy

et al. 2023

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BackgroundElectromagnetic tracking (EMT) is a promising technology that holds great potential to advance patient‐specific pre‐treatment verification in interstitial brachytherapy (iBT). It allows easy determination of the implant geometry without line‐of‐sight restrictions and without dose exposure to the patient. What it cannot provide, however, is a link to anatomical landmarks, such as the exit points of catheters or needles on the skin surface. These landmarks are required for the registration of EMT data with other imaging modalities and for the detection of treatment errors such as incorrect indexer lengths, and catheter or needle shifts.PurposeTo develop an easily applicable method to detect reference points in the positional data of the trajectory of an EMT sensor, specifically the exit points of catheters in breast iBT, and to apply the approach to pre‐treatment error detection.MethodsSmall metal objects were attached to catheter fixation buttons that rest against the breast surface to intentionally induce a local, spatially limited perturbation of the magnetic field on which the working principle of EMT relies. This perturbation can be sensed by the EMT sensor as it passes by, allowing it to localize the metal object and thus the catheter exit point. For the proof‐of‐concept, different small metal objects (magnets, washers, and bushes) and EMT sensor drive speeds were used to find the optimal parameters. The approach was then applied to treatment error detection and validated in‐vitro on a phantom. Lastly, the in‐vivo feasibility of the approach was tested on a patient cohort of four patients to assess the impact on the clinical workflow.ResultsAll investigated metal objects were able to measurably perturb the magnetic field, which resulted in missing sensor readings, that is two data gaps, one for the sensor moving towards the tip end and one when retracting from there. The size of the resulting data gaps varied depending on the choice of gap points used for calculation of the gap size; it was found that the start points of the gaps in both directions showed the smallest variability. The median size of data gaps was ⩽8 mm for all tested materials and sensor drive speeds. The variability of the determined object position was ⩽0.5 mm at a speed of 1.0 cm/s and ⩽0.7 mm at 2.5 cm/s, with an increase up to 2.3 mm at 5.0 cm/s. The in‐vitro validation of the error detection yielded a 100% detection rate for catheter shifts of ≥2.2 mm. All simulated wrong indexer lengths were correctly identified. The in‐vivo feasibility assessment showed that the metal objects did not interfere with the routine clinical workflow.ConclusionsThe developed approach was able to successfully detect reference points in EMT data, which can be used for registration to other imaging modalities, but also for treatment error detection. It can thus advance the automation of patient‐specific, pre‐treatment quality assurance in iBT.

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Section: Discussionmentioning

confidence: 99%

Localization of reference points in electromagnetic tracking data and their application for treatment error detection in interstitial breast brachytherapy

et al. 2023

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“…New software was developed in-house to calculate the dose delivered during an HDR brachytherapy treatment (section 2.1) from dwell times and source positions obtained using an IP (imaging panel)-based source tracking approach (Fonseca et al 2021, van Wagenberg et al 2023. The aim of this software is to calculate the dose that was delivered to the patient, and compare it against the planned dose to find treatment deviations.…”

Section: Methodsmentioning

confidence: 99%

“…To evaluate and showcase the tool developed in section 2.1, measurements in a phantom were performed in accordance to earlier work, see figure 1. (Fonseca et al 2021, van Wagenberg et al 2023 First, a realistic treatment plan was created for a prostate case (section 2.2). This treatment plan was delivered and measured in an anthropomorphic pelvic phantom (section 2.3) to verify the approach.…”

Section: Methodsmentioning

confidence: 99%

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Time-resolved clinical dose volume metrics, calculations and predictions based on source tracking measurements and uncertainties to aid treatment verification and error detection for HDR brachytherapy—a proof-of-principle study

van Wagenberg,

Voncken,

van Beveren

et al. 2024

Phys. Med. Biol.

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Objective. High-dose-rate (HDR) brachytherapy lacks routinely available treatment verification methods. Real-time tracking of the radiation source during HDR brachytherapy can enhance treatment verification capabilities. Recent developments in source tracking allow for measurement of dwell times and source positions with high accuracy. However, more clinically relevant information, such as dose discrepancies, is still needed. To address this, a real-time dose calculation implementation was developed to provide more relevant information from source tracking data. A proof-of-principle of the developed tool was shown using source tracking data obtained from a 3D-printed anthropomorphic phantom. Approach. Software was developed to calculate dose-volume-histograms (DVH) and clinical dose metrics from experimental HDR prostate treatment source tracking data, measured in a realistic pelvic phantom. Uncertainty estimation was performed using repeat measurements to assess the inherent dose measuring uncertainty of the in vivo dosimetry (IVD) system. Using a novel approach, the measurement uncertainty can be incorporated in the dose calculation, and used for evaluation of cumulative dose and clinical dose-volume metrics after every dwell position, enabling real-time treatment verification. Main results. The dose calculated from source tracking measurements aligned with the generated uncertainty bands, validating the approach. Simulated shifts of 3 mm in 5/17 needles in a single plan caused DVH deviations beyond the uncertainty bands, indicating errors occurred during treatment. Clinical dose-volume metrics could be monitored in a time-resolved approach, enabling early detection of treatment plan deviations and prediction of their impact on the final dose that will be delivered in real-time. Significance. Integrating dose calculation with source tracking enhances the clinical relevance of IVD methods. Phantom measurements show that the developed tool aids in tracking treatment progress, detecting errors in real-time and post-treatment evaluation. In addition, it could be used to define patient-specific action limits and error thresholds, while taking the uncertainty of the measurement system into consideration.

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“…Doyle et al [17] gather recommended phantom and tests by different entities for US systems used in prostate treatments, whereas recommendations for the commissioning, quality control and considerations for MRI acquisitions in HDR brachytherapy can be found in the American Association of Physicists in Medicine (AAPM) TG-303 [18]. On the other hand, recent publications also provide methodologies to verify the Treatment Planning System (TPS) or for treatment verification in HDR brachytherapy [19,20].…”

Section: Introductionmentioning

confidence: 99%

A User-Friendly System for Mailed Dosimetric Audits of 192Ir or 60Co HDR Brachytherapy Sources

Oliver-Cañamás

Vijande

Candela-Juan

et al. 2023

Cancers

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Objectives: The main goal of this work is to design and characterize a user-friendly methodology to perform mailed dosimetric audits in high dose rate (HDR) brachytherapy for systems using either Iridium-192 (192Ir) or Cobalt-60 (60Co) sources. Methods: A solid phantom was designed and manufactured with four catheters and a central slot to place one dosimeter. Irradiations with an Elekta MicroSelectron V2 for 192Ir, and with a BEBIG Multisource for 60Co were performed for its characterization. For the dose measurements, nanoDots, a type of optically stimulated luminescent dosimeters (OSLDs), were characterized. Monte Carlo (MC) simulations were performed to evaluate the scatter conditions of the irradiation set-up and to study differences in the photon spectra of different 192Ir sources (Microselectron V2, Flexisource, BEBIG Ir2.A85-2 and Varisource VS2000) reaching the dosimeter in the irradiation set-up. Results: MC simulations indicate that the surface material on which the phantom is supported during the irradiations does not affect the absorbed dose in the nanoDot. Generally, differences below 5% were found in the photon spectra reaching the detector when comparing the Microselectron V2, the Flexisource and the BEBIG models. However, differences up to 20% are observed between the V2 and the Varisource VS2000 models. The calibration coefficients and the uncertainty in the dose measurement were evaluated. Conclusions: The system described here is able to perform dosimetric audits in HDR brachytherapy for systems using either 192Ir or 60Co sources. No significant differences are observed between the photon spectra reaching the detector for the MicroSelectron V2, the Flexisource and the BEBIG 192Ir sources. For the Varisource VS2000, a higher uncertainty is considered in the dose measurement to allow for the nanoDot response.

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Treatment verification in high dose rate brachytherapy using a realistic 3D printed head phantom and an imaging panel

Cited by 5 publications

References 27 publications

Localization of reference points in electromagnetic tracking data and their application for treatment error detection in interstitial breast brachytherapy

Localization of reference points in electromagnetic tracking data and their application for treatment error detection in interstitial breast brachytherapy

Time-resolved clinical dose volume metrics, calculations and predictions based on source tracking measurements and uncertainties to aid treatment verification and error detection for HDR brachytherapy—a proof-of-principle study

A User-Friendly System for Mailed Dosimetric Audits of 192Ir or 60Co HDR Brachytherapy Sources

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