OC-0075 Error detection using an electromagnetic tracking system in multicatheter interstitial brachytherapy

Masitho, Siti; Kallis, Karoline; Strnad, Vratislav; Fietkau, Rainer; Bert, Christoph

doi:10.1016/s0167-8140(19)30495-5

Cited by 2 publications

(3 citation statements)

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“…Lateral and indexer (longitudinal) shifts (0.3, 0.5, 1.0, 3.0 and 5.0 mm) were simulated with the robotic arm. Reconstruction of catheter at di erent speeds were used to define dwell positions and to detect the known introduced errors using two di erent methods: mean deviation and individual dwell comparison [13,15,16]. In the first method, the mean deviation of all dwell positions relative to their reference positions in a catheter is computed and compared to a threshold.…”

Section: Error Detectionmentioning

confidence: 99%

“…However, instead of computing a mean deviation, a majority rule approach is applied. This means that when a shifted channel path is detected, at least 50% of individual dwell are above the set threshold (±0.1 mm) [16]. Panel C shows reconstructions of straight catheter (laterally shifted) at a speed of 1 cm/s.…”

Section: Error Detectionmentioning

confidence: 99%

“…According to the ROC analysis, any deviation of 1 mm is only reliably detected with a check cable speed of 2.5 cm/s or less in these well controlled conditions. Masitho et al showed that 97 % of shifts over 1.1 mm were detected when reconstruction of catheter were performed with a step-and-record method [16].…”

Section: Flexitron With Reconstruction Capabilitymentioning

confidence: 99%

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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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Section: Error Detectionmentioning

confidence: 99%

Section: Error Detectionmentioning

confidence: 99%