Effect of Edema on Postimplant Dosimetry in Prostate Brachytherapy Using CT/MRI Fusion

Tanaka, Osamu; Hayashi, Shinya; Nakano, Masahiro; Uno, Hiromi; Ohtakara, Kazuhiro; Miyoshi, Toshiharu; Deguchi, Takashi; Hoshi, Hiroaki

doi:10.1016/j.ijrobp.2007.05.082

Cited by 39 publications

(22 citation statements)

References 17 publications

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“…Edema typically subsides after 2-4 weeks, however by then much of the dose is already delivered due to the short half-life of the isotopes (Pd 103 =17 days, I 125 =60 days). Although edema results in a ~30% increase in prostate size when evaluated at Day 1 post-implantation, the degree of edema varies substantially from patient to patient with no apparent predictive factors for its magnitude or effects on implant dosimetry (Tanaka et al, 2007). It is therefore absolutely imperative that the probability of edema be reduced, by reducing the number of needle passes and adjustments, and also by shortening the duration of the implant procedure.…”

Section: Discussionmentioning

confidence: 99%

Robotic assistance for ultrasound-guided prostate brachytherapy

Fichtinger

Fiene

Kennedy

et al. 2008

Medical Image Analysis

108

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We present a robotically assisted prostate brachytherapy system and test results in training phantoms and Phase-I clinical trials. The system consists of a transrectal ultrasound (TRUS) and a spatially co-registered robot, fully integrated with an FDA-approved commercial treatment planning system. The salient feature of the system is a small parallel robot affixed to the mounting posts of the template. The robot replaces the template interchangeably, using the same coordinate system. Established clinical hardware, workflow and calibration remain intact. In all phantom experiments, we recorded the first insertion attempt without adjustment. All clinically relevant locations in the prostate were reached. Non-parallel needle trajectories were achieved. The preinsertion transverse and rotational errors (measured with a Polaris optical tracker relative to the template's coordinate frame) were 0.25mm (STD=0.17mm) and 0.75° (STD=0.37°). In phantoms, needle tip placement errors measured in TRUS were 1.04mm (STD=0.50mm). A Phase-I clinical feasibility and safety trial has been successfully completed with the system. We encountered needle tip positioning errors of a magnitude greater than 4mm in only 2 out of 179 robotically guided needles, in contrast to manual template guidance where errors of this magnitude are much more common. Further clinical trials are necessary to determine whether the apparent benefits of the robotic assistant will lead to improvements in clinical efficacy and outcomes.

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Section: Discussionmentioning

confidence: 99%

Robotic assistance for ultrasound-guided prostate brachytherapy

Fichtinger

Fiene

Kennedy

et al. 2008

Medical Image Analysis

108

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“…As ITK offers the most stable and fully tested implementations, trying its BSDR seemed a logical choice. As the results show, BSDR was indeed eminently applicable to cope with isotropic tissue swelling, to very large degrees of volume growth, safely covering the extent of edematic swelling typically observed in actual implants [6]. BSDR is able to catch up with seed perturbation, though this is a clinically less important issue, because the dose field of an individual seed is relatively isotropic and symmetrical around the centroid [18].…”

Section: Resultsmentioning

confidence: 83%

“…Edema may onset immediately after needle placement begins and continues to evolve during the procedure [2]. In a recent study, Tanaka et al found that edema caused 30% average increase in prostate volume on the first day after implantation [6]. Edema typically subsides after 2-4 weeks with a half-life of 10 days [7]; however, by then much of the dose is already delivered due to the short half-life of the isotopes (Pd103=17 days, I125=60 days).…”

Section: Introductionmentioning

confidence: 99%

Quantification of Edematic Effects in Prostate Brachytherapy Interventions

Hefny

Abolmaesumi

Karimaghaloo

et al. 2008

Medical Image Computing and Computer-Assisted Intervention – MICCAI 2008

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Abstract.We present a quantitative model to analyze the detrimental effects of edema on the quality of prostate brachytherapy implants. We account for both tissue expansion and implant migration by mapping intra-operative ultrasound and post-implant CT. We pre-process the ultrasound with a phase congruency filter, and map it to the volume CT using a B-spline deformable mutual information similarity metric. To test the method, we implanted a standard training phantom with 48 seeds, imaged the phantom with ultrasound and CT and registered the two for ground truth. Edema was simulated by distorting the CT volume by known transformations. The objective was to match the distorted implant to the intra-operative ultrasound. Performance was measured relative to ground truth. We successfully mapped 100% of deformed seeds to ground truth under edematic expansion up to 40% of volume growth. Seed matching performance was 98% with random seed migration of 3mm superimposed on 10% edematic volume growth. This method promises to be clinically applicable as the first quantitative analysis tool to measure edematic implant deformations occurring between the operating room and post-operative CT imaging.

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“…Two uncertainties still remain in the prediction of the accumulated dose from the in vivo dose-rate values obtained during implantation: the occurrence of edema during and after the implantation and the migration of individual seeds. The influence of these phenomena on the total accumulated dose has been investigated by several other groups (11)(12)(13)(14).…”

Section: Discussionmentioning

confidence: 99%