A new two-step accurate CT-MRI fusion technique for post-implant prostate cancer

Kunogi, Hiroaki; Hojo, Hidehiro; Wakumoto, Yoshiaki; Saito, Anneyuko I.; Ishikura, Satoshi; Yamashiro, Y; Kuwatsuru, R; Sasai, Keisuke

doi:10.5114/jcb.2015.51290

Cited by 14 publications

(18 citation statements)

References 19 publications

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“…Four weeks after seed implantation, post-implant CT and MRI data were acquired for dosimetric analysis. We used advanced MRI-to-CT fusion techniques [ 11 ] to mitigate MRI-CT registration error via a two-step fusion of CT scans and T2WIs using fat-suppressed T1-weighted imaging in Variseed 8.0. CT scanning was performed with 1-mm spacing in the supine position, with urinary catheter (8 Fr) in place.…”

Section: Methodsmentioning

confidence: 99%

Focal low-dose-rate prostate brachytherapy for low- and intermediate-risk prostate cancer

Kunogi¹,

Wakumoto²,

Kawamoto³

et al. 2020

jcb

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Purpose: To prospectively investigate the efficacy and feasibility of focal low-dose-rate (LDR) prostate brachytherapy for low-and intermediate-risk prostate cancer.Material and methods: Between October 2014 and May 2019, nineteen low-and intermediate-risk prostate cancer patients who presented with abnormality on both diffusion-weighted and T2-weighted magnetic resonance imaging (MRI) underwent focal LDR brachytherapy at our institution. Focal gross tumor volume (F-GTV) was delineated on transrectal ultrasound, based on abnormality seen on fused T2-weighted MRI. F-GTV was expanded by 5 mm, as a safety margin, to create focal clinical target volume (F-CTV). Prescribed dose to F-CTV was 145 Gy. Biochemical recurrence (BCR) was determined using Phoenix criterion (prostate specific antigen nadir + 2 ng/ml). Pre-and post-implant dosimetry data were compared using non-parametric Wilcoxon's rank sum test. Treatment-related toxicities were evaluated using common terminology criteria for adverse events.Results: Mean F-CTV D 90% was significantly lower in the post-implant evaluation than in intraoperative planning (p = 0.004). On post-implant dosimetry, the mean D 90% for F-GTV and mean V 100% for the entire prostate were 222 Gy and 35%, respectively. Median follow-up time for all patients was 31 months. BCR occurred in one patient after 23 months. Kaplan-Meier 2-year BCR-free rate was 92.9% (95% confidence interval [CI]: 79.4-100%). No patients had grade 1 or greater gastrointestinal toxicity. Three patients who were taking α-blockers to treat benign prostatic hyperplasia (present before brachytherapy), experienced no treatment-related genitourinary toxicities. Two patients suffered from temporary grade 2 urinary frequency. None of the remaining patients experienced grade 2 or higher genitourinary toxicity.Conclusions: Focal LDR prostate brachytherapy appears acceptable for MRI-based index tumors, with a low cumulative incidence of BCR. Such brachytherapy might offer a feasible minimally invasive therapeutic option for localized prostate cancer.

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Section: Methodsmentioning

confidence: 99%

Focal low-dose-rate prostate brachytherapy for low- and intermediate-risk prostate cancer

Kunogi¹,

Wakumoto²,

Kawamoto³

et al. 2020

jcb

Self Cite

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“…MRI-CT fusion post-implant dosimetry allows for anatomical definition on MRI images and seed localization on CT images. Nonetheless, the MRI-CT fusion quality is affected by registration quality (registration landmarks, fusion technique, fusion algorithm parameters, personnel training and experience) and imaging quality (pulse sequence, contrast, pelvic tilt, coil, patient transit between scanners, duration between scans, bladder and rectal filling differences) [ 16 , 17 , 18 , 19 ].…”

Section: Purposementioning

confidence: 99%

Development of a magnetic resonance imaging protocol to visualize encapsulated contrast agent markers in prostate brachytherapy recipients: initial patient experience

Lim

Kudchadker

Wang

et al. 2016

jcb

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PurposeComputed tomography (CT)-based prostate post-implant dosimetry allows for definitive seed localization but is associated with high interobserver variation in prostate contouring. Currently, magnetic resonance imaging (MRI)-based post-implant dosimetry allows for accurate anatomical delineation but is limited due to inconsistent seed localization. Encapsulated contrast agent markers were previously proposed to overcome the seed localization limitation on MRI images by placing hyperintense markers adjacent to hypointense seeds. The aim of this study was to assess the appearance of these markers in prostatic tissue, and develop an MRI protocol to enable marker visualization.Material and methodsWe acquired MRI scans in prostate implant patients (n = 10) on day 0 (day of implant) and day 30 (month after implant). Before implantation of the markers, the routine post-implant MRI protocol included a 3D T2-weighted fast-spin-echo (FSE) sequence with which markers and seeds could not be clearly visualized. To visualize the MRI markers, a 3D fast radiofrequency-spoiled gradient-recalled echo (FSPGR) sequence was evaluated for marker and seed visibility, as well as prostate boundary definitions.ResultsThe 3D FSPGR sequence allowed for the visualization of markers in the prostate, enabling the distinction of signal voids as seeds versus needle tracks. The updated post-implant MRI protocol consists of this 3D FSPGR scan and an optional 3D T2-weighted FSE scan. The optional 3D T2-weighted FSE sequence may be employed to better visualize intraprostatic detail. We also described the observed image artifacts, including seed susceptibility, marker chemical shift, partial volume averaging, motion, and wraparound artifacts.ConclusionsWe have demonstrated an MRI protocol for use with hyperintense encapsulated contrast agent markers to assist in the identification of hypointense seeds.

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“…CT slice thickness on the order of 1–3 mm limits seed localization accuracy, and registration between CT and MRI may be subject to errors. Advanced MRI‐to‐CT registration techniques have been developed to mitigate error; however, workflows eliminating the need for both CT and MRI are desirable to reduce resource requirements, reduce imaging dose, limit motion, and improve accuracy further.…”

Section: Introductionmentioning

confidence: 99%

Deformable registration of x ray and MRI for postimplant dosimetry in low dose rate prostate brachytherapy

Hrinivich

Park

et al. 2019

Medical Physics

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Purpose Dosimetric assessment following permanent prostate brachytherapy (PPB) commonly involves seed localization using CT and prostate delineation using coregistered MRI. However, pelvic CT leads to additional imaging dose and requires significant resources to acquire and process both CT and MRI. In this study, we propose an automatic postimplant dosimetry approach that retains MRI for soft‐tissue contouring, but eliminates the need for CT and reduces imaging dose while overcoming the inconsistent appearance of seeds on MRI with three projection x rays acquired using a mobile C‐arm. Methods Implanted seeds are reconstructed using x rays by solving a combinatorial optimization problem and deformably registered to MRI. Candidate seeds are located in MR images using local hypointensity identification. X ray‐based seeds are registered to these candidate seeds in three steps: (a) rigid registration using a stochastic evolutionary optimizer, (b) affine registration using an iterative closest point optimizer, and (c) deformable registration using a local feature point search and nonrigid coherent point drift. The algorithm was evaluated using 20 PPB patients with x rays acquired immediately postimplant and T2‐weighted MR images acquired the next day at 1.5 T with mean 0.8 × 0.8 × 3.0 mm3 voxel dimensions. Target registration error (TRE) was computed based on the distance from algorithm results to manually identified seed locations using coregistered CT acquired the same day as the MRI. Dosimetric accuracy was determined by comparing prostate D90 determined using the algorithm and the ground truth CT‐based seed locations. Results The mean ± standard deviation TREs across 20 patients including 1774 seeds were 2.23 ± 0.52 mm (rigid), 1.99 ± 0.49 mm (rigid + affine), and 1.76 ± 0.43 mm (rigid + affine + deformable). The corresponding mean ± standard deviation D90 errors were 5.8 ± 4.8%, 3.4 ± 3.4%, and 2.3 ± 1.9%, respectively. The mean computation time of the registration algorithm was 6.1 s. Conclusion The registration algorithm accuracy and computation time are sufficient for clinical PPB postimplant dosimetry.

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A new two-step accurate CT-MRI fusion technique for post-implant prostate cancer

Cited by 14 publications

References 19 publications

Focal low-dose-rate prostate brachytherapy for low- and intermediate-risk prostate cancer

Focal low-dose-rate prostate brachytherapy for low- and intermediate-risk prostate cancer

Development of a magnetic resonance imaging protocol to visualize encapsulated contrast agent markers in prostate brachytherapy recipients: initial patient experience

Deformable registration of x ray and MRI for postimplant dosimetry in low dose rate prostate brachytherapy

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