Permanent Prostate Brachytherapy Research Articles

A unified strategy to focal brachytherapy incorporating transperineal biopsy, image fusion, and real-time implantation with and without rectal spacer simulated in prostate phantoms.

To develop an approach to the diagnosis and treatment of prostate cancer using one platform for fusion biopsy, followed by focal gland ablation utilizing permanent prostate brachytherapy with and without a rectal spacer. Prostate phantoms containing multiparametric magnetic resonance imaging (mpMRI) regions of interest (ROI) underwent fusion biopsy, followed by image co-registration of positive sites to a treatment planning brachytherapy program. A partial hemi-ablation and both posterior lobes using a Mick applicator and linked stranded seeds were simulated. Dummy sources were modeled as iodine-125 (125I) with a prescribed dose of at least 210 Gy to gross tumor (GTV) and clinical target volume (CTV), as defined by mpMRI visible ROI and surrounding negative biopsy sites. Computer tomograms (CT) were performed post-implant prior to and after rectal spacer insertion. Different prostate and rectal constraints were compared with and without the spacer. The intra-operative focal volumes of CTV ranged from 6.2 to 14.9 cc (mean, 11.3 cc), and the ratio of focal volume/whole prostate volume ranged between 0.19 and 0.42 (mean, 0.31). The intra- and post-operative mean focal D90 of GTV, CTV, and for the entire prostate gland was 265 Gy and 235 Gy, 214 Gy and 213 Gy, and 66.1 Gy and 57 Gy, respectively. On average, 13 mm separation was achieved between the prostate and the rectum (range, 12-14 mm) on post-operative CT. The mean doses in Gy to 2 cc of the rectum (D2cc) without spacer vs. with spacer were 39.8 Gy vs. 32.6 Gy, respectively. Doses above 200 Gy and the implantation of seeds in clinically significant region for focal therapy in phantoms are feasible. All rectal dosimetric parameters improved for the spacer implants, as compared with the non-spacer implants. Further validation of this concept is warranted in clinical trials.

PO53: Comparative Characterization of Seed-Displacements Until Day 1 and Day 30 of Permanent Prostate Brachytherapy: Necessity and Implications for Adaptive Implantation Workflows

PO53: Comparative Characterization of Seed-Displacements Until Day 1 and Day 30 of Permanent Prostate Brachytherapy: Necessity and Implications for Adaptive Implantation Workflows

PO94: Edema and Stranded Seed Dynamics in Permanent Prostate Brachytherapy Determined by Magnetic Resonance Imaging and Computed Tomography

PO94: Edema and Stranded Seed Dynamics in Permanent Prostate Brachytherapy Determined by Magnetic Resonance Imaging and Computed Tomography

Relationship between changes in quality of life and genitourinary toxicity grade after brachytherapy with I-125 alone for localised prostate cancer.

The relationship between the grading of toxicities based on toxicity criteria and longitudinal changes in quality of life (QOL) scores after permanent prostate brachytherapy (PPB) for localized prostate cancer remains unclear. This study aimed to evaluate these relationships. We assessed 107 patients treated with PPB using Iodine-125 alone from May 2007 to April 2010. Disease-specific QOL scores before PPB and at 1, 3, 6, 12, and 24 months after PPB were retrospectively evaluated with the Expanded Prostate Cancer Index Composite (EPIC), focusing on urinary domains. Toxicities were graded using the Radiation therapy oncology group and the European organization for research and treatment of cancer toxicity criteria. The median follow-up duration was 116 (range 18-148) months. Thirty-four patients (31.8%) developed grade ≥ 2 acute genitourinary (GU) toxicities; six (5.6%) developed grade ≥ 2 late GU toxicities. The general urinary domain score dropped significantly at 1 month (77.1 ± 14.1) post-PPB compared to the baseline score (92.2 ± 8.2), and then gradually returned to the baseline level by 12 months (93.7 ± 8.3) post-PPB. Reductions in the general urinary domain scores, including its subscale scores at 1, 3, and 6-months post-PPB were significantly greater among patients with grade ≥ 2 GU toxicity than among those with grade 0-1 GU toxicity. Changes in urinary domain scores demonstrated a close relationship with acute GU toxicity grades after PPB. Longitudinal assessments of the EPIC QOL scores provided additional information regarding time-course changes in GU toxicities after PPB.

Seed-displacements in the immediate post-implant phase in permanent prostate brachytherapy

PurposeTo investigate differences in seed-displacements between the immediate post-implant phase (day 0–1) and the time to post-plan computed tomography (CT) (day 1–30) in seed prostate brachytherapy. Materials and methodsSeed positions were identified on the intra-operatively created ultrasound-based treatment plan (day 0) and CT scans of day 1 and 30 for 33 patients. The day 1 (30) seed arrangement was registered onto the day 0 (1) arrangement using a seed-only approach. Based on a 1:1 assignment of seeds via the Kuhn-Munkres algorithm, seed-displacements were analyzed. Displacements were evaluated depending on strand-length and anatomical implant location. Resulting dosimetric effects were calculated. ResultsSeed-displacements in the immediate post-implant phase (median displacements: 3.8 ± 3.6 mm) were stronger than in the time to post-plan CT (2.1 ± 2.6 mm) and enhanced along the superior-inferior direction. From day 0 to 1, strands containing one (7.3 ± 5.4 mm) or two (8.1 ± 5.8 mm) seeds showed larger displacements than strands of higher lengths (up to 4.2 ± 7.0 mm), whereas no length-dependency was found to day 30. Seeds implanted in base and apex tended to move towards the prostate midzone during both time periods. D90 (dose that 90% of prostate receives) was with variations of 2 ± 15 Gy more stable from day 1 to 30 than in the immediate post-implant phase (−18 ± 11 Gy). ConclusionSeed-displacements in the immediate post-implant phase was enhanced compared to day 1–30. This may result from uncertainties in the gold-standard ultrasound-based treatment planning and implantation. Adaptive implantation workflows appear useful for ensuring high implant stability from the beginning.

Technical Report: Quality Assurance for 125I Seed Sources in Permanent Prostate Brachytherapy

This technical report provides useful information on the current status and issues of quality control in 125I seed source strength measurement for Permanent Prostate Brachytherapy in Japan.With the spread of 125I seed brachytherapy, the traceability of source strength measurements with the single-seed assay was established in Japan. This allows medical facilities to measure reference air kerma rate of 125I seeds with their own well-type of ionization chamber. However, it is difficult to maintain the traceability chain because the 125I reference air kerma rate standards have been hardly utilized by medical facilities so far. Meanwhile, some serious incidents of contamination of the different source strengths and dead seeds were reported in Japan.To address the specific issues in Japan, JASTRO Brachytherapy Subcommittee established a working group (WG) in 2021. The goal of this WG is to investigate the management methods of source strength measurement used in medical facilities, and to discuss the ideal and practicable methods of source management such as verifying the number of seeds and source strength. Initially, a questionnaire survey was conducted to facilities offering 125I seed brachytherapy in Japan. Sixty-seven out of 95 facilities responded (response rate 70.5%). This survey revealed that 41% of facilities did not perform either confirmation of the number of seeds or measurement of source strength. There are several reasons why the source strength was not measured in those facilities. For example, 125I seeds are provided under the sterilized conditions; quality assurance by source suppliers is reliable; and there is not sufficient staff.The single-seed assay is regarded as an internationally standardized and the most reliable measurement method. Therefore, it is an essential measurement technique to ensure traceability of source strength measurements. However, our survey found that most Japanese facilities do not perform single-seed assays. Meanwhile, some facilities have performed batch assay as an alternative method, in which all of the multiple sources in a batch are measured while loaded into sterilized cartridges. Although the measurement by the batch assay is less accurate than the one by the single-seeded assay, the batch assay does not require re-sterilization of the source and can be performed quickly. It might be useful to detect unexpected errors such as differences in the number of sources and abnormalities in source strength.In this report, we will introduce several methods of source strength measurement that have been implemented in medical facilities. The quality assurance of 125I seed sources in prostate interstitial brachytherapy should be provided not only by the source suppliers but also by the medical facilities that use sources to treat patients. We hope that medical facilities will refer to this technical report and use it as an aid to quality assurance in their own facilities.

PSOR12 Presentation Time: 12:25 PM: Technique and Preferences for Permanent LDR Prostate Brachytherapy Using Cesium-131

<h3>Purpose</h3> To identify individual technique preferences for Cesium-131 prostate implantation and determine if there is a uniform method among the brachytherapists. <h3>Methods</h3> Five experienced physicians, of the Cesium Advisory Group, using Cesium-131 monotherapy for permanent prostate brachytherapy were queried regarding their technique. A review of preferences examining variability and/or similarity for each brachytherapist was undertaken. <h3>Results</h3> Results below based on a prostate with a volume of 27cc. <h3>Conclusions</h3> Per experienced practitioners, Cesium-131 implants vary on several specifics in regards to technique. The brachytherapists are uniform in their practice to implant majority of the Cesium-131 isotope in the periphery.

PSOR10 Presentation Time: 12:15 PM: Permanent LDR Brachytherapy Using Cesium-131 Monotherapy: Updated Recommendations from the Cesium Advisory Group

<h3>Purpose</h3> Cesium-131 has a higher photon energy, as well as a shorter half-life in comparison to its counterparts Iodine-125 and Palladium-103. The optimal Cesium-131 implant will deliver a safe and effective dose with the least toxicity. Recommendations were formed based on examining data from hypothetical treatment plans performed by a group of experienced brachytherapists. <h3>Methods</h3> Six physicians with significant experience using Cesium-131 monotherapy for permanent prostate brachytherapy formed an advisory group. A review of implant techniques examining variability and/or similarity of different sized prostates for each brachytherapist was undertaken. The data acquired was compared to the past Cesium Advisory Group (2008) recommendations. <h3>Results</h3> Prescription dose for Cesium-131 was 100-115 Gy. Select data presented below.

Permanent LDR prostate brachytherapy: Comprehensive characterization of seed-dynamics within the prostate on a seed-only level

PURPOSESeed brachytherapy is a well-established treatment modality for prostate cancer. However, there is still a lack of profound characterizations of seed motions within the prostate. We assessed these dynamics between day 0 and day 30 of brachytherapy. METHODSWe considered 45 patients with 2408 implanted seeds, and performed a 1:1 assignment between their positions on post-plan CT (nominal day 30) and intraoperative ultrasound (day 0). Geometric seed arrangement changes were measured for each patient and the entire collective. The impact of seed strand-lengths and implant regions was investigated. Correlations with patient characteristics were evaluated. We determined corresponding dosimetric effects by calculating common dose metrics. RESULTSWe found a median seed displacement of 4.3 mm [interquartile range: 3.1–6.9 mm], occurring preferentially in superior-inferior direction. Single and double strands moved significantly stronger than strands of higher lengths. Seed dynamics was more pronounced in base (5.6 mm [3.7–10.7 mm]) and apex (6.5 mm [4.1–15.0 mm]) than in the mid-gland (3.8 mm [2.7–5.0 mm]), and less pronounced in peripheral (4.3 mm [3.0–6.7 mm]) than in urethra-near (5.5 mm [3.5–10.7 mm]) regions. Correlations of seed dynamics with prostate volume changes and the number of implanted seeds and needles were found. D90 (dose that 90% of the prostate receives) varied by a median of 3 Gy [-6 to 15 Gy] between treatment plan and post-plan, but >40 Gy for individual patients. CONCLUSIONSReducing seed dynamics is important to ensure a high treatment quality. For this, strands containing ≥3 seeds may be useful, implantations in base-, apex-, and urethra-near zone should be avoided, and the number of needles and seeds may be minimized where possible.

ACR-ABS-ASTRO Practice Parameter for Transperineal Permanent Brachytherapy of Prostate Cancer.

The American College of Radiology (ACR), American Brachytherapy Society (ABS), and American Society for Radiation Oncology (ASTRO) have jointly developed the following practice parameter for transperineal permanent brachytherapy of prostate cancer. Transperineal permanent brachytherapy of prostate cancer is the interstitial implantation of low-dose rate radioactive seeds into the prostate gland for the purpose of treating localized prostate cancer. This practice parameter was developed according to the process described under the heading The Process for Developing ACR Practice Parameters and Technical Standards on the ACR website (https://www.acr.org/Clinical-Resources/Practice-Parameters-and-Technical-Standards) by the Committee on Practice Parameters-Radiation Oncology of the Commission on Radiation Oncology, in collaboration with ABS and ASTRO. This practice parameter provides a framework for the appropriate use of low-dose rate brachytherapy in the treatment of prostate cancer either as monotherapy or as part of a treatment regimen combined with external-beam radiation therapy. The practice parameter defines the qualifications and responsibilities of all involved radiation oncology personnel, including the radiation oncologist, medical physicist, dosimetrist, radiation therapist, and nursing staff. Patient selection criteria and the utilization of supplemental therapies such as external-beam radiation therapy and androgen deprivation therapy are discussed. The logistics of the implant procedure, postimplant dosimetry assessment, and best practices with regard to safety and quality control are presented. Adherence to established standards can help to ensure that permanent prostate brachytherapy is delivered in a safe and efficacious manner.

Correlations between intraplan and postplan parameters in I-125 permanent prostate brachytherapy using loose seeds or linked seeds.

ABSTRACTThe purpose of this study was to determine the most appropriate seed arrangement by comparing two different methods (linked seeds and loose seeds). A total of sixty-one patients (28 linked seed brachytherapy cases and 33 loose seed brachytherapy cases) with clinically localized prostate cancer were treated with I-125 permanent prostate brachytherapy. Modified peripheral loading was the method used for seed placement. The parameters evaluated were as follows: prostate D90, V100, and V150; urethral D90, D10, and D5; and rectal V100 (RV100) and D2 (RD2). Coefficient parameters (r and r2) were assessed by regression analysis. Prostate V150, urethral D90, urethral D10, urethral D5, and RD2 showed significant correlations between both methods in all patients. Urethral D90, urethral D10, urethral D5, and RD2 showed significant correlations in patients who received linked seed brachytherapy. Prostate V150, urethral D90, urethral D10, urethral D5, RV100, and RD2 showed significant correlations in patients who received loose seed brachytherapy. Urethral D90, urethral D10, urethral D5, and RD2 showed significant correlations in the linked seed and loose seed brachytherapy analyses. In contrast, prostate D90 and prostate V100 showed no correlation. Parameters of normal organ damage showed good correlations between intraplan and postplan parameters. These parameters may be useful to determine normal organ damage during guided brachytherapy with two different methods (linked seeds and loose seeds).

Local seed displacement from Day 0 to Day 30 in I-125 permanent prostate brachytherapy: A detailed, computed tomography-based analysis

PURPOSETo accurately quantify local seed displacement from Day 0 to Day 30 for our brachytherapy procedure. To quantify seed loss/migration and to identify the locations from where seeds are missing. METHODS AND MATERIALSSeed displacements were analyzed in 62 consecutive patients, who received brachytherapy with stranded I-125 seeds. At the start of the procedure, four fiducial gold markers were implanted. At the end of the implantation procedure an in-room 3D CBCT scan (Day 0) was acquired for accurate seed localization. At Day 30 a regular CT scan was acquired. This CT scan was rigidly registered to the CBCT scan using the fiducials. Subsequently, the Hungarian method was used to find pairs of corresponding seeds. Displacements were calculated and missing seeds were identified. RESULTSLocal seed displacements are smaller than 5 mm for 76.3% of the seeds; 2.3% show displacements larger than 10 mm. The largest seed displacements are seen along the inferior-superior axis: on average 1.0 ± 3.2 mm in superior direction with respect to the intraprostatic fiducials. Largest displacements are seen at the inferior-lateral sides of the prostate. On average, the inferior seeds move 1.0 ± 2.8 mm in anterior and 1.8 ± 3.3 mm in superior direction. The percentage of missing seeds is 0.2% (8 out of 3893 seeds for 5 patients). Most of the missing seeds were also originally implanted at the inferior-lateral sides of the prostate. CONCLUSIONSLocal seed displacements and number of missing seeds are small, and predominantly occur around the apex.

The Investigation of Tissue Composition Effects on Dose Distributions Using Monte Carlo Method in Permanent Prostate Brachytherapy

Objective: Radiation dose calculations in the prostate brachytherapy practices have very high importance in terms of the success of treatment. The purpose of the present study is to determine whether there is a significant dose difference between the radiation dose calculations performed in water medium and prostate cancer-diagnosed patients by using the Monte Carlo method.&#x0D; Methods: The radiation dose calculations were performed on 20 prostate patients by using the BrachyDose Monte Carlo code. Phantom geometry derived from real patients computed tomography (CT) data was created to use in dose calculations. Water material was assigned to all voxels within the prostate volume for dose comparison with CT derived phantom. 125I (Amersham, OncoSeed, 6711), 103Pd (Theragenics Co., TheraSeed, 200) and 131Cs (IsoRay Medical) commercial brachytherapy seed models were used in dose calculations. &#x0D; Results: It was observed that there are significant dose differences between the water medium and the prostate tissue. The differences between D90 dose values in prostate tissue and water medium were calculated as 7.2-10.5%, 9.1-13.4% and 5.4-8.3% for 125I, 103Pd and 131Cs brachytherapy seed sources, respectively. &#x0D; Conclusions: It was concluded that material compositions of different organs and tissues in the human body should be considered for more accurate brachytherapy dose calculations.

Analysis of radioactive implant migration in patients treated with iodine-125 seeds for permanent prostate brachytherapy with MRI-classified median lobe hyperplasia.

PurposeProstate cancer with median lobe hyperplasia (MLH) is a relative contraindication for permanent prostate brachytherapy (PPB) because of an increased risk of post-implant dysuria and technical difficulties associated with achieving stability while implanting within the intravesical tissue. We examined treatment outcome, seed migration, and urination disorders after treatment in MLH patients in order to determine to what degree MLH implants could be stabilized.Material and methodsBetween March 2007 and December 2016, 32 patients had MLH identified radiologically on magnetic resonance imaging, and 193 patients did not have MLH (non-MLH). All patients were treated with loose seeds. In this study, seed migration was defined as a seed distant from the target (≥ 1.5 cm) and/or with no dosimetric contribution to the target. The MLH patients were divided into 2 MLH groups of mild (< 10 mm) and severe (≥ 10 mm) MLH by measuring the distance between the posterior transitional zone and the prostatic tissue protruding into the bladder. We retrospectively analyzed seed migration, dose-volume histograms (DVH), and genitourinary toxicity.ResultsMLH was classified as mild in 24 patients and severe in 8. Seed migration occurred in 61 (31.6%) of 193 non-MLH patients and 10 (31.5%) of 32 MLH patients. Implant seed migration and low-dose level of median lobe tended to be high in severe MLH cases. International Prostate Symptom Score (IPSS) peaked one month after implantation, but then resolved slowly and returned to around the pre-treatment level after one year. There were no severe complications.ConclusionsMLH does not appear to be a strong contraindication for low-dose-rate brachytherapy. However, we found that the seed migration and degree of cold spots tended to be higher in severe MLH cases than in others; therefore, close attention when treating severe MLH cases must be paid.

Editorial Comment to Relationship between radiation doses and erectile function deterioration in patients with localized prostate cancer treated with permanent prostate brachytherapy.

Editorial Comment to Relationship between radiation doses and erectile function deterioration in patients with localized prostate cancer treated with permanent prostate brachytherapy.

Long-term outcomes of a prospective randomized trial of 131Cs/125I permanent prostate brachytherapy

PurposeIodine-125 (125I) is the most commonly used isotope for prostate brachytherapy (BT). Cesium-131 (131Cs) has a higher dose rate and shorter dose delivery time resulting in decreased duration of acute urinary morbidity. Long-term data suggest excellent oncologic outcomes; it is not known how outcomes compare. A prospective randomized trial comparing the two isotopes was initiated. Materials and MethodsPatients with low- or intermediate-risk disease were treated with a BT in a single outpatient facility. Prescription dose was 144 Gy for 125I and 115 Gy for 131Cs. Androgen deprivation or supplemental EBRT was not allowed. The primary study objective was comparison of the mean EPIC Urinary Domain Score. Secondary objective was biochemical relapse-free survival (BRFS) comparison. Time-to-event for all outcomes of interest was measured from implant date. ResultsOne hundred forty men were enrolled; 81.4% were low-risk and 18.6% were intermediate-risk. The median followup was 97 months. Urinary and sexual health-related quality of life did not differ between isotopes at any recorded time point. At 2 months after implantation, bowel health-related quality of life was worse with 125I; however, this difference was lost at subsequent time points. The 9-year BRFS was 87.2% and 84.0% for the 125I and 131Cs group, respectively (p = 0.897). There was no statistically significant difference in BRFS based on initial T stage, PSA, or Gleason score. ConclusionsShort- and long-term urinary, sexual, and bowel quality of life, as well as long-term biochemical control were comparable between 125I and 131Cs. This report therefore supports the continued use of 131Cs as an effective and comparable alternative isotope.

Relationship between radiation doses and erectile function deterioration in patients with localized prostate cancer treated with permanent prostate brachytherapy.

To investigate the relationship between radiation doses in prostate brachytherapy and deterioration of erectile function in patients with localized prostate cancer. A longitudinal survey study was carried out among 261 prostate cancer patients who received prostate brachytherapy. A total of 48 patients were potent at baseline and they did not receive any supplemental therapy preoperatively. Dosimetry parameters of the whole prostate gland, prostate apex, urethra and rectum were collected using the VariSeed 8.0 treatment planning system (Varian Medical Systems, Palo Alto, CA, USA). We carried out a logistic regression analysis to clarify the relationship between radiation doses and erectile function deterioration, which was assessed using the International Index of Erectile Function-15 questionnaire. The median patient age was 66years (range 53-70years) with a median follow-up time of 44months (36-71months). The mean total International Index of Erectile Function-15 score decreased from 49.9 at baseline to 34.7 after 12months (P<0.001), but gradually plateaued within 36months. Erectile function deterioration was noted in 32 (66.7%) patients 36months after prostate brachytherapy. In an analysis of risk factors for erectile function deterioration after prostate brachytherapy, age ≥70years (P=0.029), prostate V100 ≥95% (P=0.024), apex V100 ≥95% (P=0.024), apex V150 ≥70% (P=0.009) and apex D90 ≥150Gy (P=0.011) correlated with erectile function deterioration. A multivariate analysis identified an age of ≥70years (odds ratio 7.91, P=0.024) and apex V150 ≥70% (odds ratio 7.75, P=0.007) as independent risk factors for erectile function deterioration after prostate brachytherapy. An excessive radiation dose, particularly to the prostate apex area, and an advanced age might have a negative impact on the preservation of potency after prostate brachytherapy.

Time to achieve a prostate-specific antigen nadir of ≤0.2 ng/mL and related factors after permanent prostate brachytherapy

PurposeThe purpose of this study was to identify the time to achieve a prostate-specific antigen (PSA) nadir of ≤0.2 ng/mL and the related factors to achieve this goal. Materials and MethodsWe retrospectively reviewed 2218 Japanese prostate cancer patients who received 125I brachytherapy with or without external beam radiotherapy between 2003 and 2013 at one institution. Among them, patients followed up for ≥72 months and without luteinizing hormone–releasing hormone (LH-RH) agonist/antagonist were included (total of 1089 patients). The time to a PSA nadir of ≤0.2 ng/mL (months) was defined as the time between the date of implantation and the first time the lowest PSA value reached ≤0.2 ng/mL. Biochemical recurrence (BCR) was determined using the Phoenix definition. Multivariate linear regression analysis was performed to detect the related factors to achieve this nadir. ResultsWe assigned 409, 592, and 88 patients to the low-, intermediate-risk, and high-risk groups, respectively. The median followup time was 9.5 years. The median time to achieve a PSA nadir of ≤0.2 ng/mL was 44.0 (95% confidence interval: 42.3–45.7) months. The percentage of patients that achieved the nadir was 89.1%. BCR was noted in 107 (9.8%) patients. In the multivariate analysis of patients without BCR, younger age, larger prostate volume at implantation, higher initial PSA level, and monotherapy were significantly associated with longer time to achieve the PSA nadir. ConclusionThe median time to achieve a PSA nadir of ≤0.2 ng/mL was 44.0 months. Some patients, however, may require a lengthy period of time to do so.

A deep learning method for real-time intraoperative US image segmentation in prostate brachytherapy.

This paper addresses the detection of the clinical target volume (CTV) in transrectal ultrasound (TRUS) image-guided intraoperative for permanent prostate brachytherapy. Developing a robust and automatic method to detect the CTV on intraoperative TRUS images is clinically important to have faster and reproducible interventions that can benefit both the clinical workflow and patient health. We present a multi-task deep learning method for an automatic prostate CTV boundary detection in intraoperative TRUS images by leveraging both the low-level and high-level (prior shape) information. Our method includes a channel-wise feature calibration strategy for low-level feature extraction and learning-based prior knowledge modeling for prostate CTV shape reconstruction. It employs CTV shape reconstruction from automatically sampled boundary surface coordinates (pseudo-landmarks) to detect the low-contrast and noisy regions across the prostate boundary, while being less biased from shadowing, inherent speckles, and artifact signals from the needle and implanted radioactive seeds. The proposed method was evaluated on a clinical database of 145 patients who underwent permanent prostate brachytherapy under TRUS guidance. Our method achieved a mean accuracy of [Formula: see text] and a mean surface distance error of [Formula: see text]. Extensive ablation and comparison studies show that our method outperformed previous deep learning-based methods by more than 7% for the Dice similarity coefficient and 6.9 mm reduced 3D Hausdorff distance error. Our study demonstrates the potential of shape model-based deep learning methods for an efficient and accurate CTV segmentation in an ultrasound-guided intervention. Moreover, learning both low-level features and prior shape knowledge with channel-wise feature calibration can significantly improve the performance of deep learning methods in medical image segmentation.

Prostate brachytherapy intraoperative dosimetry using a combination of radiographic seed localization with a C-arm and deformed ultrasound prostate contours

PurposeThe purpose of the study was to assess the feasibility of performing intraoperative dosimetry for permanent prostate brachytherapy by combining transrectal ultrasound (TRUS) and fluoroscopy/cone beam CT [CBCT] images and accounting for the effect of prostate deformation. Methods and Materials13 patients underwent TRUS and multiview two-dimensional fluoroscopic imaging partway through the implant, as well as repeat fluoroscopic imaging with the TRUS probe inserted and retracted, and finally three-dimensional CBCT imaging at the end of the implant. The locations of all the implanted seeds were obtained from the fluoroscopy/CBCT images and were registered to prostate contours delineated on the TRUS images based on a common subset of seeds identified on both image sets. Prostate contours were also deformed, using a finite-element model, to take into account the effect of the TRUS probe pressure. Prostate dosimetry parameters were obtained for fluoroscopic and CBCT-dosimetry approaches and compared with the standard-of-care Day-0 postimplant CT dosimetry. ResultsHigh linear correlation (R2 > 0.8) was observed in the measured values of prostate D90%, V100%, and V150%, between the two intraoperative dosimetry approaches. The prostate D90% and V100% obtained from intraoperative dosimetry methods were in agreement with the postimplant CT dosimetry. Only the prostate V150% was on average 4.1% (p-value <0.05) higher in the CBCT-dosimetry approach and 6.7% (p-value <0.05) higher in postimplant CT dosimetry compared with the fluoroscopic dosimetry approach. Deformation of the prostate by the ultrasound probe appeared to have a minimal effect on prostate dosimetry. ConclusionsThe results of this study have shown that both of the proposed dosimetric evaluation approaches have potential for real-time intraoperative dosimetry.