Quantifying clinical severity of physics errors in high-dose rate prostate brachytherapy using simulations

Nuñez, David; Träger, M.; Beaudry, Joel; Cohen, Gilad; Dauer, Lawrence T.; Gorovets, Daniel; Rezaeian, Nima Hassan; Leong, Brian; McCann, Paul; Williamson, Matthew J.; Zeléfsky, Michael J.; Damato, Antonio L.

doi:10.1016/j.brachy.2021.05.007

Cited by 5 publications

(4 citation statements)

References 28 publications

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“…This is despite the fact that a joint review on clinical brachytherapy uncertainties by the GEC-ESTRO and the AAPM reports that 'the largest uncertainties are at the patient level and related to anatomical differences between the real patient situation at the time of dose delivery and the planned patient geometry and organ definitions.' 22 In prostate iBT various studies could not identify a universally valid threshold value, but determined error thresholds in the range of 1-6 mm that were not only strongly dependent on the individual patient's anatomy and implant geometry, [44][45][46][47] but also varied across treatment plans from different departments. 48 Kallis et al analyzed the follow-up CTs of 55 patients after two days of accelerated partial breast irradiation, that is after four out of nine treatment fractions, regarding both geometric deviations of dwell positions and their impact on dosimetric quality indices.…”

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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“…Additionally, digitization errors of 1 and 3 mm directed along the needle (inferior-superior) were introduced in 5 random needles, by manually adjusting the coordinates of the source position. Digitization errors can occur during a HDR prostate treatment when a needle is incorrectly annotated in the planning software, and occur due to the difficulty in finding needle tips in the transrectal ultrasound imaging used for treatment planning (Rylander et al 2017, Nunez et al 2021. Additionally, shifts caused by a needle moving in superior or inferior direction and an incorrect value for indexer length would cause the same effect.…”

Section: Dvh Uncertainty Analysismentioning

confidence: 99%

“…The threshold for the magnitude of detectable errors depends on the uncertainty of the tracking method. Simulation studies have shown that, for HDR prostate brachytherapy treatments, single needle shifts starting from as low as 1 mm could be clinically relevant for the patient (Poder et al 2019, Nunez et al 2021. Besides needle motion, there are different possible errors, such as selecting the wrong indexer length or wrongly defined needles in the treatment planning system (Rylander et al 2017, Nunez et al 2021.…”

Section: Introductionmentioning

confidence: 99%

“…Simulation studies have shown that, for HDR prostate brachytherapy treatments, single needle shifts starting from as low as 1 mm could be clinically relevant for the patient (Poder et al 2019, Nunez et al 2021. Besides needle motion, there are different possible errors, such as selecting the wrong indexer length or wrongly defined needles in the treatment planning system (Rylander et al 2017, Nunez et al 2021. These treatment errors could be considered as systematic shifts, as all dwell positions of a single needle will drift towards the same direction or will be shifted when wrongly digitized or annotated.…”

Section: Introductionmentioning

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

et al. 2023

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Quantifying clinical severity of physics errors in high-dose rate prostate brachytherapy using simulations

Cited by 5 publications

References 28 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

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

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