HDR prostate brachytherapy plan robustness and its effect on in‐vivo source tracking error thresholds: A multi‐institutional study

Poder, Joel; Koprivec, Dylan; Dookie, Yashiv; Howie, Andrew; Cutajar, Dean L; Damato, Antonio L.; Côté, Nathalie; Petasecca, Marco; Bucci, Joseph; Rosenfeld, Anatoly

doi:10.1002/mp.15658

Cited by 15 publications

(26 citation statements)

References 23 publications

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“…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. They found mean geometric differences between corresponding dwell positions of 2.41 ± 1.73 mm.…”

Section: Discussionmentioning

confidence: 99%

“…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, 44–47 but also varied across treatment plans from different departments 48 . Kallis et al.…”

Section: Discussionmentioning

confidence: 99%

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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%

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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“…A displacement of a heavily weighted dwell position can cause a large change in the dose to critical volumes [ 21 ]. When planning, evaluation of the treatment plan robustness may be considered using the metric developed by Poder et al ., where dwell location and relative weighting is taken into account [ 22 ]. Further investigation is required to verify the robustness parameter's application for gynecological application.…”

Section: Discussionmentioning

confidence: 99%

Investigation of in vivo source tracking error thresholds for interstitial and intra-cavitary high-dose-rate cervical brachytherapy

Dookie¹,

Poder²,

Downes³

et al. 2022

jcb

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Purpose The purpose of this study was to determine a comprehensive in vivo source tracking error thresholds in high-dose-rate (HDR) brachytherapy for cervical cancer. Achieving this enables the definition of an action level for imminent in vivo source tracking technologies and treatment monitoring devices, preventing clinically relevant changes to the applied dose. Material and methods Retrospective HDR interstitial ( n = 10) and intra-cavitary ( n = 20) cervical brachytherapy patients were randomly selected to determine the feasibility of implementing in vivo source tracking error thresholds. A script was developed to displace all dwell positions in each treatment plan, along all major axes from their original position. Dose-volume histogram (DVH) indices were calculated without re-optimization of modified plans to determine the appropriate in vivo source tracking error thresholds in each direction. Results In vivo source tracking error thresholds were directionally dependent; the smallest were found to be 2 mm in the anterior and posterior directions for both interstitial and intra-cavitary treatments. High-risk clinical treatment volume (HR-CTV) coverage was significantly impacted by displacements of 4 to 5 mm along each axis. Critically, there was a large variation in DVH metrics with displacement due to change in dwell weightings and patient anatomy. Conclusions Determining the dosimetric impact of dwell position displacement provides a clinical benchmark for the development of pre-treatment verification devices and an action level for real-time treatment monitoring. It was established that an in vivo source tracking error threshold needs to be patient-specific. In vivo source tracking error thresholds should be determined for each patient, and can be conducted with extension of the method established in this work.

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“…High-dose-rate (HDR) brachytherapy is an effective treatment method for skin, vaginal, cervical, and prostate cancers, which together impact over 3 million individuals annually. [1][2][3][4][5][6] The efficacy of HDR brachytherapy is ascribed to its high dose rate and steep dose gradient, which delivers high dose to targets and spares surrounding organs at risk (OARs). A typical dose rate at treatment depth is about 0.5-1.0 Gy per minute for a new Ir-192 source with 370 GBq activity.…”

Section: Introductionmentioning

confidence: 99%

Feasibility of 4D HDR brachytherapy source tracking using x‐ray tomosynthesis: Monte Carlo investigation

Vasyltsiv

Qian

et al. 2023

Medical Physics

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PurposeHigh dose rate (HDR) brachytherapy rapidly delivers dose to targets with steep dose gradients. This treatment method must adhere to prescribed treatment plans with high spatiotemporal accuracy and precision, as failure to do so may degrade clinical outcomes. One approach to achieving this goal is to develop imaging techniques to track HDR sources in vivo in reference to surrounding anatomy. This work investigates the feasibility of using an isocentric C‐arm x‐ray imager and tomosynthesis methods to track Ir‐192 HDR brachytherapy sources in vivo over time (4D).MethodsA tomosynthesis imaging workflow was proposed and its achievable source detectability, localization accuracy, and spatiotemporal resolution were investigated in silico. An anthropomorphic female XCAT phantom was modified to include a vaginal cylinder applicator and Ir‐192 HDR source (0.5 × 0.5 × 5.0 mm3), and the workflow was carried out using the MC‐GPU Monte Carlo image simulation platform. Source detectability was characterized using the reconstructed source signal‐difference‐to‐noise‐ratio (SDNR), localization accuracy by the absolute 3D error in its measured centroid location, and spatiotemporal resolution by the full‐width‐at‐half‐maximum (FWHM) of line profiles through the source in each spatial dimension considering a maximum C‐arm angular velocity of 30° per second. The dependence of these parameters on acquisition angular range (θtot = 0°–90°), number of views, angular increment between views (Δθ = 0°–15°), and volumetric constraints imposed in reconstruction was evaluated. Organ voxel doses were tallied to derive the workflow's attributable effective dose.ResultsThe HDR source was readily detected and its centroid was accurately localized with the proposed workflow and method (SDNR: 10–40, 3D error: 0–0.144 mm). Tradeoffs were demonstrated for various combinations of image acquisition parameters; namely, increasing the tomosynthesis acquisition angular range improved resolution in the depth‐encoded direction, for example from 2.5 mm to 1.2 mm between θtot = 30o and θtot = 90o, at the cost of increasing acquisition time from 1 to 3 s. The best‐performing acquisition parameters (θtot = 90o, Δθ = 1°) yielded no centroid localization error, and achieved submillimeter source resolution (0.57 × 1.21 × 5.04 mm3 apparent source dimensions, FWHM). The total effective dose for the workflow was 263 µSv for its required pre‐treatment imaging component and 7.59 µSv per mid‐treatment acquisition thereafter, which is comparable to common diagnostic radiology exams.ConclusionsA system and method for tracking HDR brachytherapy sources in vivo using C‐arm tomosynthesis was proposed and its performance investigated in silico. Tradeoffs in source conspicuity, localization accuracy, spatiotemporal resolution, and dose were determined. The results suggest this approach is feasible for localizing an Ir‐192 HDR source in vivo with submillimeter spatial resolution, 1–3 second temporal resolution and minimal additional dose burden.

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HDR prostate brachytherapy plan robustness and its effect on in‐vivo source tracking error thresholds: A multi‐institutional study

Cited by 15 publications

References 23 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

Investigation of in vivo source tracking error thresholds for interstitial and intra-cavitary high-dose-rate cervical brachytherapy

Feasibility of 4D HDR brachytherapy source tracking using x‐ray tomosynthesis: Monte Carlo investigation

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