Impact of inter- and intra-observer variabilities of catheter reconstruction on multi-catheter interstitial brachytherapy of breast cancer patients

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

doi:10.1016/j.radonc.2019.02.017

Cited by 6 publications

(3 citation statements)

References 22 publications

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“…Hensley et al (2003) also reported catheter reconstruction uncertainties which range between 1.1 mm to 2.8 mm and can also affect the measurement data. Inter-and intra-observer variabilities also affect the catheter reconstruction uncertainties in the order of 0.6 mm Kallis et al (2019).…”

Section: Discussionmentioning

confidence: 99%

Error detection using an electromagnetic tracking system in multi-catheter breast interstitial brachytherapy

Masitho¹,

Kallis²,

Strnad³

et al. 2019

Phys. Med. Biol.

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The hybrid treatment delivery system (HTDS) has been proposed as a possible option for a quality assurance in the multi-catheter interstitial brachytherapy for breast cancer patients. The system, which consists out of a prototype afterloader with an integrated electromagnetic tracking (EMT) sensor and an EMT system, allows the automatic measurement of implanted catheters. To test the feasibility of the system for error detection, possible treatment planning errors and treatment delivery errors were simulated. Planning errors such as an incorrect offset value, an incorrect indexer length, tip/connector end swaps, and partial swaps, and; treatment delivery errors such as catheter shifts and catheter connection swaps were manually simulated using phantoms. An in-house Matlab routine was used to assess geometrical deviations between the dwell positions defined based on CT and EMT measurement. Additionally, the influence of implant motion on the detection ability of the system was assessed. An algorithm for the detection and specification of errors based on the error simulation results was developed. At the University Hospital Erlangen, a patient study is ongoing, where errors in patient data were analyzed using the proposed algorithm. All simulated planning errors were detected. Catheter connection swaps can be detected 100% of the time. A shift detection rate of >97% was observed for shifts larger than 1.1 mm, both in the static and the motion measurements. Catheter reconstruction uncertainties and catheter shifts <2 mm were found to be the most common treatment planning and delivery errors in patient data. HTDS proved to be a reliable method for error detection.

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Section: Discussionmentioning

confidence: 99%

Error detection using an electromagnetic tracking system in multi-catheter breast interstitial brachytherapy

Masitho¹,

Kallis²,

Strnad³

et al. 2019

Phys. Med. Biol.

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“…In individual cases, the coverage index varied up to 1.64%, even though the exact same target volume was considered. 42 In the present study, the deviations between V 100 of the FCT and the ECT were 0.8% and 1.5%, but these values encompass the additional uncertainties associated with a modified target volume introduced by the propagation of the structure from the PCT to the FCT and ECT. A detailed dosimetric analysis is subject of current research and will be presented in a second study.…”

Section: Estimated Ct Images Using Emt Datamentioning

confidence: 48%

“…A study that investigated the dosimetric changes of 13 patients as a result of only the inter‐observer variability of the reconstruction step found that the V 100 of the PTV, that is, the coverage index, deviated 0.27 ± 0.31% (mean ± standard deviation) from the clinically approved treatment plan. In individual cases, the coverage index varied up to 1.64%, even though the exact same target volume was considered 42 . In the present study, the deviations between V 100 of the FCT and the ECT were 0.8% and 1.5%, but these values encompass the additional uncertainties associated with a modified target volume introduced by the propagation of the structure from the PCT to the FCT and ECT.…”

Section: Discussionmentioning

confidence: 64%

Estimating follow‐up CTs from geometric deformations of catheter implants in interstitial breast brachytherapy: A feasibility study using electromagnetic tracking

et al. 2023

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BackgroundElectromagnetic tracking (EMT) systems have been shown to provide valuable information on the geometry of catheter implants in breast cancer patients undergoing interstitial brachytherapy (iBT). In the context of an extended patient‐specific, pre‐treatment verification, EMT can play a key role in determining the potential need and, if applicable, the appropriate time for treatment adaptation. To detect dosimetric shortcomings the relative position between catheters, and target volume and critical structures must be known. Since EMT cannot provide the anatomical context and standard imaging techniques such as cone‐beam CT are not yet available in most brachytherapy suites, it is not possible to detect anatomic changes on a daily or fraction basis, so the need for adaptive planning cannot be identified.PurposeThe aim of this feasibility study is to develop and evaluate a technique capable of estimating follow‐up CTs at any time based on the initial treatment planning CT (PCT) and surrogate information about changes of the implant geometry from an EMT system.MethodsA deformation vector field is calculated from two different implant reconstructions acquired in treatment position through EMT, the first immediately after the PCT and the second at another time point during the course of treatment. The calculation is based on discrete displacement vectors of pairs of control and target points. These are extrapolated by means of different radial basis functions in order to cover the entire CT volume. The adequate parameters for the calculation of the deformation field were identified. By warping the PCT according to the deformation field, one obtains an estimated CT (ECT) that reflects the geometric changes. For the proof of concept, ECTs were computed for the time point of the clinical follow‐up CT (FCT) that is embedded in the treatment workflow after the fourth fraction.ResultsECT and clinical FCTs of 20 patients were compared to each other quantitatively in terms of absolute Hounsfield unit differences in the planning target volume (PTV) and in a convex hull (CH) enclosing the catheters. The median differences were 31.2 and 29.5 HU for the CH and the PTV, respectively.ConclusionThe proposed ECT approach was able to approximate the “anatomy of the day” and therefore, in principle, allows a dosimetric appraisal of the treatment plan quality before each fraction. In this way, it can contribute to a more detailed patient‐specific quality assurance in iBT of the breast and help to identify the timing for a potential treatment adaptation.

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Initial needle tracking with the first standalone combined infrared camera – CT system for brachytherapy—analysis of tracking accuracy and uncertainties

Karius,

Leifeld,

Strnad

et al. 2024

Strahlenther Onkol

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Purpose A prototype infrared camera – cone-beam computed tomography (CBCT) system for tracking in brachytherapy has recently been developed. We evaluated for the first time the corresponding tracking accuracy and uncertainties, and implemented a tracking-based prediction of needles on CBCT scans. Methods A marker tool rigidly attached to needles was 3D printed. The precision and accuracy of tool tracking was then evaluated for both static and dynamic scenarios. Euclidean distances between the tracked and CBCT-derived markers were assessed as well. To implement needle tracking, ground truth models of the tool attached to 200 mm and 160 mm needles were matched to the tracked positions in order to project the needles into CBCT scans. Deviations between projected and actual needle tips were measured. Finally, we put our results into perspective with simulations of the system’s tracking uncertainties. Results For the stationary scenario and dynamic movements, we achieved tool-tracking precision and accuracy of 0.04 ± 0.06 mm and 0.16 ± 0.18 mm, respectively. The tracked marker positions differed by 0.52 ± 0.18 mm from the positions determined via CBCT. In addition, the predicted needle tips in air deviated from the actual tip positions by only 1.62 ± 0.68 mm (200 mm needle) and 1.49 ± 0.62 mm (160 mm needle). The simulated tracking uncertainties resulted in tip variations of 1.58 ± 0.91 mm and 1.31 ± 0.69 mm for the 200 mm and 160 mm needles, respectively. Conclusion With the innovative system it was possible to achieve a high tracking and prediction accuracy of marker tool and needles. The system shows high potential for applicator tracking in brachytherapy.

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Impact of inter- and intra-observer variabilities of catheter reconstruction on multi-catheter interstitial brachytherapy of breast cancer patients

Cited by 6 publications

References 22 publications

Error detection using an electromagnetic tracking system in multi-catheter breast interstitial brachytherapy

Error detection using an electromagnetic tracking system in multi-catheter breast interstitial brachytherapy

Estimating follow‐up CTs from geometric deformations of catheter implants in interstitial breast brachytherapy: A feasibility study using electromagnetic tracking

Initial needle tracking with the first standalone combined infrared camera – CT system for brachytherapy—analysis of tracking accuracy and uncertainties

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