Introduction of a hybrid treatment delivery system used for quality assurance in multi-catheter interstitial brachytherapy

Kallis, Karoline; Kreppner, Stephan; Lotter, Michael; Fietkau, Rainer; Strnad, Vratislav; Bert, Christoph

doi:10.1088/1361-6560/aabb5a

Cited by 17 publications

(44 citation statements)

References 32 publications

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“…This level of accuracy allows for dose measurement uncertainty of 5% for a detector at 10 mm from the source and better at larger distances. Furthermore, knowing the detector position in real time enables its use as input when implementing the source tracking approach [76] , [77] .…”

Section: Discussionmentioning

confidence: 99%

In vivo dosimetry in brachytherapy: Requirements and future directions for research, development, and clinical practice

Fonseca

Johansen

Smith

et al. 2020

Physics and Imaging in Radiation Oncology

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Brachytherapy can deliver high doses to the target while sparing healthy tissues due to its steep dose gradient leading to excellent clinical outcome. Treatment accuracy depends on several manual steps making brachytherapy susceptible to operational mistakes. Currently, treatment delivery verification is not routinely available and has led, in some cases, to systematic errors going unnoticed for years. The brachytherapy community promoted developments in in vivo dosimetry (IVD) through research groups and small companies. Although very few of the systems have been used clinically, it was demonstrated that the likelihood of detecting deviations from the treatment plan increases significantly with time-resolved methods. Time-resolved methods could interrupt a treatment avoiding gross errors which is not possible with time-integrated dosimetry. In addition, lower experimental uncertainties can be achieved by using source-tracking instead of direct dose measurements. However, the detector position in relation to the patient anatomy remains a main source of uncertainty. The next steps towards clinical implementation will require clinical trials and systematic reporting of errors and nearmisses. It is of utmost importance for each IVD system that its sensitivity to different types of errors is well understood, so that end-users can select the most suitable method for their needs. This report aims to formulate requirements for the stakeholders (clinics, vendors, and researchers) to facilitate increased clinical use of IVD in brachytherapy. The report focuses on high dose-rate IVD in brachytherapy providing an overview and outlining the need for further development and research. ☆ During the 1st ESTRO Physics Workshop celebrated in November 2017 in Glasgow, Scotland, a task group was created to stimulate the wider adoption of in vivo dosimetry for radiotherapy. The members of this task group, authors of this report, were selected on the basis of their expertise to contribute relevant input to the area of study and their long-term experience in the clinical implementation of in vivo dosimetry systems.

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Section: Discussionmentioning

confidence: 99%

In vivo dosimetry in brachytherapy: Requirements and future directions for research, development, and clinical practice

Fonseca

Johansen

Smith

et al. 2020

Physics and Imaging in Radiation Oncology

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“…A prototype of a hybrid Flexitron afterloader with an embedded EM tracking system (Elekta Brachytherapy, Veenendaal, The Netherlands) was used for the EMT experiments at our facility. This HTDS has been described in detail by Kallis et al [12]. In short, the HTDS consists of a Flexitron afterloader in which an electromagnetic sensor with a length of 8 mm is embedded, combined with an electromagnetic field generator and a processing unit (Fig.…”

Section: Emt/bt Systemmentioning

confidence: 99%

“…Electromagnetic tracking has been proposed for pretreatment verification in BT [11][12][13][14]. EMT allows for 3D reconstruction of the applicator/catheter path by moving an EMT sensor through the implant without acquiring additional images.…”

mentioning

confidence: 99%

“…EMT allows for 3D reconstruction of the applicator/catheter path by moving an EMT sensor through the implant without acquiring additional images. Recently, a hybrid treatment delivery system (HTDS) was introduced, integrating the EMT sensor into an HDR BT afterloader (Elekta Brachytherapy, Veenendaal, The Netherlands) [12,15]. In the HTDS the EMT sensor is embedded in the afterloader and it can be guided automatically through the implant according to the planned dwell positions.…”

mentioning

confidence: 99%

“…The accuracy of EMT measurements with the HTDS was investigated for interstitial breast implants in dedicated breast phantoms and in breast cancer patients, finding sub-millimeter accuracy [12,15]. EMT with the HTDS could be used to monitor the implant configuration for pelvic (i.e.…”

mentioning

confidence: 99%

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Accuracy of dwell position detection with a combined electromagnetic tracking brachytherapy system for treatment verification in pelvic brachytherapy

Heerden

Schiphof-Godart

Christianen

et al. 2021

Radiotherapy and Oncology

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Background and purpose: To investigate the accuracy of dwell position detection with a combined electromagnetic tracking (EMT) brachytherapy (BT) system for treatment verification, by quantifying positional errors due to EM field interference in typical pelvic BT clinical settings. Materials and methods: Dedicated prostate and cervix BT phantoms were imaged with CT. For the cervix phantom, the Utrecht applicator + interstitial catheters were used. The implants were reconstructed and treatment plans were created with 270/65 dwell positions for the prostate/cervix phantom. Next, EMT experiments were performed in clinical BT settings using a prototype of a combined EMT/BT system. We quantified positional errors due to EM field interference from surrounding equipment by comparing planned and EMT-measured dwell positions. The mean residual error between planned and EMTmeasured dwell positions was calculated in the prostate interstitial catheters and in the whole cervix implant including the applicator. For the cervix phantom, the analysis was repeated for only the interstitial catheters. Results: Mean residual errors of less than 0.5/0.4 mm in the prostate/cervix catheters were found. For the whole cervix implant including the applicator, large deviations up to 2.4 mm were found. Compared to the interference free set-up, the CT and patient bed environments showed larger residual errors in the interstitial catheters, but residual errors remained <1 mm in all cases. Conclusion: Dwell position detection with the combined system in interstitial catheters is sufficiently accurate to perform EMT-based treatment verification. The effect of EM interference from the surrounding equipment was limited.

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Performance of an enhanced afterloader with electromagnetic tracking capabilities for channel reconstruction and error detection

2021

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Purpose To assess catheter reconstruction and error detection performance of an afterloader (Elekta Brachytherapy, Veenendaal, The Netherlands) equipped with electromagnetic (EM) tracking capabilities. Materials/Methods The Flexitron research unit used was equipped with a special check cable integrating an EM sensor (NDI Aurora V3) that enables tracking and reconstruction capability. The reconstructions of a 24‐cm long catheter were performed using two methods: continuous fixed‐speed check cable backward stepping (at 1, 2.5, 5, 10, 25 and 50 cm/s) and stepping through each dwell position every 1 mm. The ability of the system to differentiate between two closely located (parallel) catheters was investigated by connecting catheters to the afterloader and moving it from its axis with an increment of 1 mm. A robotic arm (Meca500, Mecademic, Montreal) with an accuracy of 0.01 mm was used to move the catheter between each reconstruction. Reconstructions were obtained with a locally weighted scatterplot smoothing algorithm. To quantify the reconstruction accuracy, distances between two catheters were computed along the reconstruction track with a 5 mm step. The reconstructions of curve catheter paths were assessed through parallel and perpendicular phantom configuration to the EM field generator. Indexer length and lateral errors were simulated and a ROC analysis was made. Results Using a 50 cm/s check cable speed does not allow for accurate reconstructions. A slower check cable speed results in better reconstruction performance and smaller standard deviations. At 1 cm/s, a catheter can be shifted laterally down to 1 mm and all paths can be uniquely identified. The optimum operating distance from the field generator (50 to 300 mm) resulted in a lower absolute mean deviation from the expected value (0.2 ± 0.1 mm) versus being positioned on the edge of the electromagnetic sensitive detection volume (0.6 ±0.3 mm). The reconstructions of curved catheters with a check cable speed under 5 cm/s gave a 0.8 mm ±0.3 mm error, or better. All indexer and lateral shifts of 1 mm were detected with a check cable speed of 2.5 cm/s or lower. Conclusions The EM‐equipped Flexitron afterloader is able to track and reconstruct catheters with high accuracy. A speed under 5 cm/s is recommended for straight and curved catheter reconstructions. It allows catheter identification down to 1 mm inter‐catheter distance shift. The check cable can also be used to detect common shift errors.

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Introduction of a hybrid treatment delivery system used for quality assurance in multi-catheter interstitial brachytherapy

Cited by 17 publications

References 32 publications

In vivo dosimetry in brachytherapy: Requirements and future directions for research, development, and clinical practice

In vivo dosimetry in brachytherapy: Requirements and future directions for research, development, and clinical practice

Accuracy of dwell position detection with a combined electromagnetic tracking brachytherapy system for treatment verification in pelvic brachytherapy

Performance of an enhanced afterloader with electromagnetic tracking capabilities for channel reconstruction and error detection

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