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Background and Purpose: Comparing deep learning (DL) algorithms to human interobserver variability, one of the largest sources of noise in human-performed annotations, is necessary to inform the clinical application, use, and quality assurance of DL for prostate radiotherapy., Materials and Methods: One hundred fourteen DL algorithms were developed on 295 prostate MRIs to segment the prostate, external urinary sphincter (EUS), seminal vesicles (SV), rectum, and bladder. Fifty prostate MRIs of 25 patients undergoing MRI-based low-dose-rate prostate brachytherapy were acquired as an independent test set. Groups of DL algorithms were created based on the loss functions used to train them, and the spatial entropy (SE) of their predictions on the 50 test MRIs was computed. Five human observers contoured the 50 test MRIs, and SE maps of their contours were compared with those of the groups of the DL algorithms. Additionally, similarity metrics were computed between DL algorithm predictions and consensus annotations of the 5 human observers' contours of the 50 test MRIs., Results: A DL algorithm yielded statistically significantly higher similarity metrics for the prostate than did the human observers (H) (prostate Matthew's correlation coefficient, DL vs. H: planning-0.931 vs. 0.903, p < 0.001; postimplant-0.925 vs. 0.892, p < 0.001); the same was true for the 4 organs at risk. The SE maps revealed that the DL algorithms and human annotators were most variable in similar anatomical regions: the prostate-EUS, prostate-SV, prostate-rectum, and prostate-bladder junctions., Conclusions: Annotation quality is an important consideration when developing, evaluating, and using DL algorithms clinically., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Purpose: To investigate the feasibility of using parallel imaging compressed sensing (PICS) to reduce scan time and improve signal-to-noise ratio (SNR) in MRI-based postimplant dosimetry of prostate brachytherapy., Methods and Materials: Ten patients underwent low-dose-rate prostate brachytherapy with radioactive seeds stranded with positive magnetic resonance-signal seed markers and were scanned on a Siemens 1.5T Aera. MRI comprised a fully balanced steady-state free precession sequence with two 18-channel external pelvic array coils with and without a rigid two-channel endorectal coil. The fully sampled data sets were retrospectively subsampled with increasing acceleration factors and reconstructed with parallel imaging and compressed sensing algorithms. The images were assessed in a blinded reader study by board-certified care providers. Rating scores were compared for statistically significant differences between reconstruction types., Results: Images reconstructed from subsampling up to an acceleration factor of 4 with PICS demonstrated consistently sufficient quality for dosimetry with no apparent loss of SNR, anatomy depiction, or seed/marker conspicuity when compared to the fully sampled images. Images obtained with acceleration factors of 5 or 6 revealed reduced spatial resolution and seed marker contrast. Nevertheless, the reader study revealed that images obtained with an acceleration factor of up to 5 and reconstructed with PICS were adequate-to-good for postimplant dosimetry., Conclusions: Combined parallel imaging and compressed sensing can substantially reduce scan time in fully balanced steady-state free precession imaging of the prostate while maintaining adequate-to-good image quality for postimplant dosimetry. The saved scan time can be used for multiple signal averages and improved SNR, potentially obviating the need for an endorectal coil in MRI-based postimplant dosimetry., (Copyright © 2018 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.)

Purpose: To study the deformation of the prostate by a rigid reusable endorectal coil and a balloon-type endorectal coil (BTC) during MRI of the prostate in brachytherapy imaging., Methods and Materials: The prostate gland was contoured on 157 MRI scans from 52 prostate cancer patients undergoing brachytherapy. The curvature of the posterior prostate surface deformation was computed as a measure of prostate distortion and compared between scans with a BTC, rigid endorectal coil (REC), or no endorectal coil. For the nine patients who had MRIs with all three endorectal scenarios, a mean prostate deformation vector was also calculated between scenarios using deformable image registration. These measures of prostate distortion were compared with the prostate anterior-to-posterior to left-to-right ratio (AP/LR) on the largest prostate axial slice., Results: Significant differences in prostate curvature were found between scans without an endorectal coil versus a REC versus a BTC (p < 0.001). The mean prostate deformation was 3.9 mm due to the BTC and 2.0 mm for the REC (p = 0.012). The mean AP/LR ratio was 0.62 with a BTC versus 0.76 without a coil or 0.73 with a REC (p < 0.001), but no difference existed between scans with a REC versus no coil (p = 0.7). The AP/LR ratio showed moderate correlation with prostate curvature (r = 0.48), and with mean prostate deformation (r = -0.64 to 0.68)., Conclusions: The REC caused minimal deformation of the prostate compared with a BTC with adequate MR image quality, and calculation of the cross-sectional AP/LR ratio on the largest axial prostate slice can serve as a simple measure of prostate distortion., (Published by Elsevier Inc.)

Purpose: Palladium-103 ((103)Pd) may be superior to other isotopes in brachytherapy for localized intermediate-risk prostate cancer because of its relatively short half-life, higher initial dose rate, and greater dose heterogeneity within the target volume; these properties also underscore the need for accurate target delineation and postimplant quality assurance. We assessed the use of prostate sector analysis based on MRI for quality assurance after (103)Pd monotherapy., Methods and Materials: Fifty men with intermediate-risk prostate cancer underwent (103)Pd monotherapy in a prospective phase II trial at MD Anderson Cancer Center. Dosimetric analyses on day 30 after the implant were done using both CT and fused CT/MRI scans. Dosimetric variables were assessed for the entire prostate and for each of three or six sectors. Volumes and dosimetric variables were compared with paired t tests., Results: Postimplant dosimetric variables for the entire prostate were significantly different on CT vs. CT/MRI (p = 0.019 for V100 and p < 0.01 for D90). Prostate volumes were smaller on the CT/MRI scans (p < 0.00001). The base sector contributed the greatest difference, with doses based on CT/MRI lower than those based on CT (p < 0.01 for V100 and D90). To date, these lower base doses have not affected biochemical outcomes for patients with disease in prostate base biopsy samples., Conclusions: CT/MRI is more precise than CT for prostate volume delineation and dosimetric quality assessment and thus provides superior heterogeneity control assessment after (103)Pd monotherapy implants., (Copyright © 2014 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.)

Purpose: Many clinicians use Prostogram data to advise patients selecting prostate cancer therapy. We examined whether the Prostogram accurately predicted recurrence at 5 years in patients treated with 125I brachytherapy at 1 tertiary cancer center. Materials and Methods: We retrospectively reviewed the records of 208 consecutive patients with prostate cancer treated with a permanent 125I implant without neoadjuvant androgen deprivation therapy at 1 tertiary cancer center during 1998 to 2006. In each patient the Prostogram brachytherapy formula was used to calculate 5-year biochemical recurrence-free survival probability based on clinical stage, Gleason sum score, prostate specific antigen and the receipt or not of external beam radiotherapy. Recurrence was defined as clinical relapse, death from disease, posttreatment androgen deprivation therapy, secondary treatments administered before prostate specific antigen failure or biochemical recurrence based on the Kattan modification of the American Society for Therapeutic Radiology and Oncology definition of biochemical recurrence after external beam radiation therapy. Patients were divided into quartiles based on Prostogram predicted 5-year recurrence-free survival probability and mean probability was compared to the actual 5-year recurrence-free survival rate in each quartile. Harrell''s concordance statistic was used to assess the predictive accuracy of the nomogram. Results: Actual 5-year biochemical recurrence-free survival rates were superior to Prostogram predicted probabilities, including 89% vs 80%, 87% vs 86%, 100% vs 89% and 100% vs 94% in quartiles 1 to 4, respectively. Harrell''s concordance value was 0.487 (95% CI 0.369–0.605), indicating that the predictive accuracy of the nomogram in our patients was less than 50%. Conclusions: The Prostogram did not predict recurrence after permanent prostate brachytherapy in this series. Institutional variability requires that clinicians be cautious when using the Prostogram to counsel patients about the probability of success after permanent prostate brachytherapy. [Copyright &y& Elsevier]

We sought to develop an activity nomogram for magnetic resonance (MR)–planned permanent seed prostate brachytherapy to improve quality assurance through a secondary dosimetric check. Patients undergoing MRI-assisted radiosurgery (MARS), whereby MRI is used for preoperative planning and postimplant dosimetry, were reviewed from May 2016 to September 2018. Planned activity (U) was fitted by MR-prostate volume (cc) via simple linear regression. Resulting monotherapy nomograms were compared with institutional nomograms from an ultrasound-planned cohort. Dosimetric coverage and external urinary sphincter (EUS) dose were also assessed for MR-planned patients. We identified 183 patients treated with MARS: 146 patients received palladium-103 (103Pd; 102 monotherapy and 44 boost), and 37 received iodine-125 (125I) monotherapy. Median prostate volume was 28 cc (interquartile range: 22–35). Lines of best fit for implant activity were U = 4.344 × (vol) + 54.13 (R2: 95%) for 103Pd monotherapy, U = 3.202 (vol) + 39.72 (R2: 96%) for 103Pd boost and U = 0.684 (vol) + 13.38 (R2: 96%) for 125I monotherapy. Compared with ultrasound, MR-planned nomograms had lower activity per volume (p < 0.05) for both 103Pd monotherapy (∼6%) and 125I monotherapy (∼11%), given a median size (30 cc) prostate. Across all MARS implants, postimplant dosimetry revealed a median V100% of 94% (interquartile range: 92–96%). Median EUS V125 was <1 cc for all patients, regardless of isotope. We developed a quality assurance nomogram for MR-planned prostate brachytherapy. When compared with ultrasound-planned, MR-planned monotherapy resulted in a lower activity-to-volume ratio while maintaining dosimetric coverage, likely secondary to EUS-sparing and reduced planning target margins. [ABSTRACT FROM AUTHOR]

Uncertainties in postimplant quality assessment (QA) for low-dose-rate prostate brachytherapy (LDRPBT) are introduced at two steps: seed localization and contouring. We quantified how interobserver variability (IoV) introduced in both steps impacts dose-volume-histogram (DVH) parameters for MRI-based LDRPBT, and compared it with automatically derived DVH parameters. Twenty-five patients received MRI-based LDRPBT. Seven clinical observers contoured the prostate and four organs at risk, and 4 dosimetrists performed seed localization, on each MRI. Twenty-eight unique manual postimplant QAs were created for each patient from unique observer pairs. Reference QA and automatic QA were also performed for each patient. IoV of prostate, rectum, and external urinary sphincter (EUS) DVH parameters owing to seed localization and contouring was quantified with coefficients of variation. Automatically derived DVH parameters were compared with those of the reference plans. Coefficients of variation (CoVs) owing to contouring variability (CoV contours) were significantly higher than those due to seed localization variability (CoV seeds) (median CoV contours vs. median CoV seeds : prostate D90–15.12% vs. 0.65%, p < 0.001; prostate V100–5.36% vs. 0.37%, p < 0.001; rectum V100–79.23% vs. 8.69%, p < 0.001; EUS V200–107.74% vs. 21.18%, p < 0.001). CoV contours were lower when the contouring observers were restricted to the 3 radiation oncologists, but were still markedly higher than CoV seeds. Median differences in prostate D90, prostate V100, rectum V100, and EUS V200 between automatically computed and reference dosimetry parameters were 3.16%, 1.63%, −0.00 mL, and −0.00 mL, respectively. Seed localization introduces substantially less variability in postimplant QA than does contouring for MRI-based LDRPBT. While automatic seed localization may potentially help improve workflow efficiency, it has limited potential for improving the consistency and quality of postimplant dosimetry. [ABSTRACT FROM AUTHOR]

• High interobserver variability (IoV) was observed at junctions between the prostate and one or more organs at risk. • Radiation oncologists were the most consistent group of observers, but high IoV was still observed in this group. • IoV demonstrated a dependence on organ size, and was highest for the external urinary sphincter. • High IoV was observed on both treatment planning MRIs and postimplant quality assessment MRIs. • Dose-volume-histogram parameters for MRI-based prostate radiotherapy are heavily influenced by IoV. Quantifying the interobserver variability (IoV) of prostate and periprostatic anatomy delineation on prostate MRI is necessary to inform its use for treatment planning, treatment delivery, and treatment quality assessment. Twenty five prostate cancer patients underwent MRI-based low-dose-rate prostate brachytherapy (LDRPBT). The patients were scanned with a 3D T2-weighted sequence for treatment planning and a 3D T2/T1-weighted sequence for quality assessment. Seven observers involved with the LDRPBT workflow delineated the prostate, external urinary sphincter (EUS), seminal vesicles, rectum, and bladder on all 50 MRIs. IoV was assessed by measuring contour similarity metrics, differences in organ volumes, and differences in dosimetry parameters between unique observer pairs. Measurements from a group of 3 radiation oncologists (G1) were compared against those from a group consisting of the other 4 clinical observers (G2). IoV of the prostate was lower for G1 than G2 (Matthew's correlation coefficient [MCC], G1 vs. G2: planning–0.906 vs. 0.870, p < 0.001; postimplant–0.899 vs. 0.861, p < 0.001). IoV of the EUS was highest of all the organs for both groups, but was lower for G1 (MCC, G1 vs. G2: planning–0.659 vs. 0.402, p < 0.001; postimplant–0.684 vs. 0.398, p < 0.001). Large differences in prostate dosimetry parameters were observed (G1 maximum absolute prostate ΔD90: planning–76.223 Gy, postimplant–36.545 Gy; G1 maximum absolute prostate ΔV100: planning–13.927%, postimplant–8.860%). While MRI is optimal in the management of prostate cancer with radiation therapy, significant interobserver variability of the prostate and external urinary sphincter still exist. [ABSTRACT FROM AUTHOR]

Purpose: To investigate machine segmentation of pelvic anatomy in magnetic resonance imaging (MRI)-assisted radiosurgery (MARS) for prostate cancer using prostate brachytherapy MRIs acquired with different pulse sequences and image contrasts.Methods and Materials: Two hundred 3-dimensional (3D) preimplant and postimplant prostate brachytherapy MRI scans were acquired with a T2-weighted sequence, a T2/T1-weighted sequence, or a T1-weighted sequence. One hundred twenty deep machine learning models were trained to segment the prostate, seminal vesicles, external urinary sphincter, rectum, and bladder using the MRI scans acquired with T2-weighted and T2/T1-weighted image contrast. The deep machine learning models consisted of 18 fully convolutional networks (FCNs) with different convolutional encoders. Both 2-dimensional and 3D U-Net FCNs were constructed for comparison. Six objective functions were investigated: cross-entropy, Jaccard distance, focal loss, and 3 variations of Tversky distance. The performance of the models was compared using similarity metrics, including pixel accuracy, Jaccard index, Dice similarity coefficient (DSC), 95% Hausdorff distance, relative volume difference, Matthews correlation coefficient, precision, recall, and average symmetrical surface distance. We selected the highest-performing architecture and investigated how the amount of training data, use of skip connections, and data augmentation affected segmentation performance. In addition, we investigated whether segmentation on T1-weighted MRI was possible with FCNs trained on only T2-weighted and T2/T1-weighted image contrast.Results: Overall, an FCN with a DenseNet201 encoder trained via cross-entropy minimization yielded the highest combined segmentation performance. For the 53 3D test MRI scans acquired with T2-weighted or T2/T1-weighted image contrast, the DSCs of the prostate, external urinary sphincter, seminal vesicles, rectum, and bladder were 0.90 ± 0.04, 0.70 ± 0.15, 0.80 ± 0.12, 0.91 ± 0.06, and 0.96 ± 0.04, respectively, after model fine-tuning. For the 5 T1-weighted images, the DSCs of these organs were 0.82 ± 0.07, 0.17 ± 0.15, 0.46 ± 0.21, 0.87 ± 0.06, and 0.88 ± 0.05, respectively.Conclusions: Machine segmentation of the prostate and surrounding anatomy on 3D MRIs acquired with different pulse sequences for MARS low-dose-rate prostate brachytherapy is possible with a single FCN. [ABSTRACT FROM AUTHOR]

Education and training on prostate brachytherapy for radiation oncology and medical physics residents in the United States is inadequate, resulting in fewer competent radiation oncology personnel to perform implants, and is a factor in the subsequent decline of an important, potentially curative cancer treatment modality for patients with cancer. The American Brachytherapy Society (ABS) leadership has recognized the need to establish a sustainable medical simulation low-dose-rate (LDR) and high-dose-rate (HDR) brachytherapy workshop program that includes physician–physicist teams to rapidly translate knowledge to establish high-quality brachytherapy programs. The ABS, in partnership with industry and academia, has held three radiation oncology team–based LDR/HDR workshops composed of physician–physicist teams in Chicago in 2017, in Houston in 2018, and in Denver in 2019. The predefined key metric of success is the number of attendees who returned to their respective institutions and were actively performing brachytherapy within 6 months of the prostate brachytherapy workshop. Of the 111 physician/physicist teams participating in the Chicago, Houston, and Denver prostate brachytherapy workshops, 87 (78%) were actively performing prostate brachytherapy (51 [59%] HDR and 65 [75%] LDR). The ABS prostate brachytherapy LDR/HDR simulation workshop has provided a successful education and training structure for medical simulation of the critical procedural steps in quality assurance to shorten the learning curve for delivering consistently high-quality brachytherapy implants for patients with prostate cancer. An ABS initiative, intended to bend the negative slope of the brachytherapy curve, is currently underway to train 300 new competent brachytherapy teams over the next 10 years. [ABSTRACT FROM AUTHOR]

Despite a preponderance of data demonstrating strong clinical outcomes and cost-effectiveness, prostate brachytherapy use and competency continue to decline. Enhanced resident education may help reverse this trend. We therefore developed and implemented a simulation-based medical education course for low-dose-rate prostate brachytherapy (LDR-PB). A 1-week LDR-PB course comprised four 1-h lectures on clinical outcomes, physics, radiobiology, and anatomy/contouring, followed by a 4.5-h simulation session on ultrasound-guided prostate phantom implantation, was developed for radiation oncology residents at an academic institution. A 10-statement Likert-scale survey and 20-question multiple-choice test were administered 1 week before and 4 weeks after the course. Precourse and postcourse instruments were completed by 24 and 20 residents, respectively. The median number of prior LDR-PB cases after at least one genitourinary rotation was 10.5 (range 5–20). Overall mean test scores were significantly improved (55% before the course vs 68% after the course; p = 0.010). Mean Likert scores significantly increased on nine of 10 survey statements and were significantly increased overall (2.4 before the course vs 3.3 after the course, p < 0.001). When asked about interest in performing brachytherapy after residency, 37.5% of residents "agreed" or "strongly agreed" before the course vs 50% after the course (p = 0.41). Those with higher postresidency brachytherapy interest (scores of 4–5 vs 1–3) had significantly more LDR-PB cases (11.2 vs 5.3 cases; p = 0.005). A 1-week simulation-based medical education course for LDR-PB can improve didactic performance and self-reported technical competence/confidence, and may increase overall enthusiasm for brachytherapy. Future studies at our institution will incorporate evaluation of implant quality and assessment of procedural competence into this framework. Residency programs should dedicate resources to this essential component of radiation oncology. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare an isotropic three-dimensional (3D) T2-weighted sequence sampling perfection with application-optimized contrasts by using flip angle evolution (SPACE) with an axial two-dimensional T2-weighted turbo spin echo (TSE) sequence with regard to overall image quality and the delineation of normal prostate and periprostatic anatomy for low-dose-rate prostate cancer brachytherapy planning evaluation. Patients (n = 69) with prostate cancer who had pelvic magnetic resonance imaging (MRI) for low-dose-rate brachytherapy treatment planning were included. Three radiologists independently assessed the visibility of nine anatomic structures on each sequence by using a 5-point scale and overall image quality by using a 4-point scale. The significance of the differences in diagnostic performance was tested with a Wilcoxon signed rank test. No significant intersequence differences were found for most (7/9) anatomical structures and overall image quality. The mean scores for visibility of anatomical structures on the 3D SPACE and 2D TSE sequences, respectively, were as follows: the zonal anatomy (3.7; 3.9, p = 0.05), prostate capsule (3.9; 4.0, p = 0.08), neurovascular bundle (2.9; 2.9, p = 0.9), rectoprostatic angle (3.8; 3.8, p = 0.35), rectum (4.2; 4.3, p = 0.26), urethra (3.8; 3.9, p = 0.12), urinary bladder (4.6; 4.6, p = 0.61), and overall image quality (2.9; 2.9, p = 0.33). 3D SPACE was superior for delineation of the genitourinary diaphragm (3.8; 3.6, p = 0.003), whereas 2D TSE was superior for delineation of the seminal vesicles (3.5; 4.0, p < 0.0001). Anatomic delineation of the prostatic and periprostatic anatomy provided by the 3D SPACE sequence is as robust in quality as that provided by a conventional 2D TSE sequence with superior delineation of the genitourinary diaphragm. For MRI-based brachytherapy treatment planning, the 3D SPACE sequence with subcentimeter isotropic resolution can replace the 2D TSE sequence and be incorporated into standard MRI protocols. [ABSTRACT FROM AUTHOR]

To quantify the 2 sources of human interobserver variability (IoV) introduced during prostate MRI-assisted radiosurgery postimplant dosimetry, and compare this human variability to automatically generated postimplant dosimetry. Twenty-five patients underwent LDR prostate brachytherapy (LDRPBT) and were imaged with fully balanced SSFP for postimplant dosimetry. Four certified medical dosimetrists (CMDs) identified the radioactive seeds in each of the 25 postimplant MRIs. Seven additional clinical observers, including 3 radiation oncologists (ROs), contoured the prostate and 4 organs at risk (OARs) on the MRIs. Consensus segmentation masks from the 3 ROs' contours were computed for each patient using the simultaneous truth and performance level estimation (STAPLE) algorithm. Thirty unique postimplant dosimetry plans were computed for each patient. Twenty-eight of the dosimetry plans were computed from each unique pair of the CMDs' seed plans and observer contours (4 CMDs × 7 contourers). One dosimetry plan was performed automatically for each patient using custom autosegmentation and automatic seed identification software developed previously. A reference dosimetry plan for each patient was computed using the consensus STAPLE segmentations and the seeds identified by the most experienced CMD. IoV of 5 dosimetry parameters was quantified separately for each IoV source: IoV introduced by seed localization, and IoV introduced by anatomy contouring. The coefficient of variation (CoV) of each dosimetry parameter was quantified for each patient across CMDs using the consensus STAPLE segmentations. Similarly, the CoV of each dosimetry parameter was quantified for each patient across contouring observers using the seed locations determined by the most experienced CMD. Additionally, the differences in dosimetry parameters between the reference and automatic dosimetry plans were quantified. CoVs due to variability of anatomy contouring (CoV contours) were significantly higher than those due to variability of seed localization (CoV seeds) for all dosimetry parameters (median CoV contours vs. median CoV seeds : prostate D90 - 15.116% vs. 0.651%, p<0.001; prostate V100 - 5.359% vs. 0.365%, p<0.001; prostate V150 - 7.017% vs. 1.252%, p<0.001; rectum V100 - 79.230% vs. 8.688%, p<0.001; EUS V200 - 107.740% vs. 21.176%, p<0.001). CoV contours were lower when the contouring observers were restricted to only the 3 ROs, but they were still significantly higher than CoV seeds for all dosimetry parameters. Median differences in prostate D90, prostate V100, prostate V150, rectum V100, and EUS V200 between automatically computed and reference dosimetry parameters were 3.156%, 1.630%, -1.071%, -0.001%, and -0.002%, respectively. Most automatically computed dosimetry parameters were within the expected variability of those produced by human observers (Figure 1). IoV of contouring constitutes the largest source of IoV in postimplant dosimetry plans performed by clinical observers. When using automatic contouring and seed localization tools, review and refinement of computer predictions will be necessary for some patients. However, automatic dosimetry tools can estimate postimplant dosimetry that is close to, or within, the expected variability of dosimetry plans produced by clinical observers. [ABSTRACT FROM AUTHOR]

Purpose Permanent prostate brachytherapy dosimetry using computed tomography-magnetic resonance imaging (CT-MRI) fusion combines the anatomic detail of MRI with seed localization on CT but requires multimodality imaging acquisition and fusion. The purpose of this study was to compare the utility of MRI only postimplant dosimetry to standard CT-MRI fusion-based dosimetry. Methods and Materials Twenty-three patients undergoing permanent prostate brachytherapy with use of positive contrast MRI markers were included in this study. Dose calculation to the whole prostate, apex, mid-gland, and base was performed via standard CT-MRI fusion and MRI only dosimetry with prostate delineated on the same T2 MRI sequence. The 3-dimensional (3D) distances between seed positions of these two methods were also evaluated. Wilcoxon-matched-pair signed-rank test compared the D90 and V100 of the prostate and its sectors between methods. Results The day 0 D90 and V100 for the prostate were 98% versus 94% and 88% versus 86% for CT-MRI fusion and MRI only dosimetry. There were no differences in the D90 or V100 of the whole prostate, mid-gland, or base between dosimetric methods ( p > 0.19), but prostate apex D90 was high by 13% with MRI dosimetry ( p = 0.034). The average distance between seeds on CT-MRI fusion and MRI alone was 5.5 mm. After additional automated rigid registration of 3D seed positions, the average distance between seeds was 0.3 mm, and the previously observed differences in apex dose between methods was eliminated ( p > 0.11). Conclusions Permanent prostate brachytherapy dosimetry based only on MRI using positive contrast MRI markers is feasible, accurate, and reduces the uncertainties arising from CT-MRI fusion abating the need for postimplant multimodality imaging. [ABSTRACT FROM AUTHOR]

Purpose Pubic arch interference (PAI), when it occurs, is often a limiting factor for patients pursuing brachytherapy treatment of prostate cancer. Pre-brachytherapy pubic arch evaluation is often performed by CT or transrectal ultrasound (TRUS), but MRI has increasingly replaced these modalities for prostate cancer evaluation. The purpose of this study was to determine if staging MRI could be used to evaluate PAI and compare it with these other imaging methods. Methods and Materials Forty-one consecutive patients undergoing brachytherapy evaluation had pelvic MRI-, CT-, and TRUS-based brachytherapy simulation. Pubic arch overlap on T2-weighted MRI and CT was determined by contouring the prostate gland on its largest axial slice and superimposing this contour onto the pubic arch bones. The largest degree of overlap of the prostate gland on MRI and CT was used to predict the existence of PAI as determined by TRUS-based simulation. The correlation between prostate contour overlap was also compared between MRI and CT. Results Nineteen patients (48%) exhibited PAI on TRUS brachytherapy simulation evaluation. The average (±standard error) amount of prostate contour overlap on the pubic arch on CT was 2.9 ± 0.6 mm and on MRI was 2.0 ± 0.6 mm (linear correlation, R , of 0.783, p < 0.001). CT and MRI were equally predictive of PAI on TRUS evaluation (area under the curve = 0.75). Conclusion Pre-brachytherapy pubic arch assessment with diagnostic MRI provides similar predictability of PAI compared with CT, potentially obviating the need for additional pre-brachytherapy CT in the setting of staging MRI. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: Transrectal ultrasound (TRUS) is the standard imaging modality for planning prostate brachytherapy. However, magnetic resonance imaging (MRI) provides greater anatomic detail than TRUS. We compared treatment plans generated using TRUS, endorectal coil MRI (erMRI), and standard body array coil MRI (sMRI). Methods and Materials: Treatment plans were used from patients treated with permanent, stranded-seed 125I brachytherapy in a prospective trial. All men underwent pretreatment planning based on TRUS, and all underwent erMRI before treatment and sMRI 30 days after the implant. Treatments for 20 consecutive patients were replanned on sMRI and erMRI images by investigators blinded to TRUS-based plans. Prostate volume/dimensions, radioactivity-to-prostate-volume ratio, and dosimetric parameters were compared. Results: Compared with TRUS, mean prostate volume measured by erMRI was smaller, medial-lateral diameter was larger, and anterior-posterior diameter was smaller, suggesting that the endorectal coil produced anatomic distortions. Craniocaudal prostate length was smaller on both types of MRI than on TRUS, suggesting that TRUS overestimates prostate length. Activity per volume was 7.5% lower for plans based on sMRI than on TRUS (0.901 vs. 0.974mCi/cm3, p <0.001). sMRI plans had similar coverage of the planning target volume (PTV) (dose to 90% of the prostate [D 90] 116.6% sMRI vs. 117.5% TRUS, p =0.526) and improved dose homogeneity (percentage of PTV receiving 150% of the prescription dose [V 150] 47.4% sMRI vs. 53.8% TRUS, p =0.001 and percentage of PTV receiving 200% of the prescription dose [V 200] 16.6% sMRI vs. 19.2% TRUS, p <0.001). Conclusions: Staging erMRI should not be routinely used for treatment planning because it produces anatomic distortion. sMRI may have treatment planning advantages over TRUS because of superior soft-tissue delineation of the prostate and adjacent normal tissue structures. [Copyright &y& Elsevier]

Objectives: To evaluate acute and long-term urinary morbidity after permanent prostate brachytherapy at a single tertiary care center. To minimize the risk of long-term urinary morbidity, it is important for clinicians to be able to distinguish acute urinary side effects after prostate brachytherapy from longer-term treatment-related urinary complications. Methods: The medical records of 351 consecutive patients who underwent prostate brachytherapy at the MD Anderson Cancer Center between 1998 and 2006 were analyzed. To evaluate the short-term urinary side effects, the Expanded Prostate Cancer Index Composite questionnaire was administered at baseline and at 1, 4, 8, and 12 months. Long-term urinary complications were scored using a modified Radiation Therapy Oncology Group scale. Results: All 4 urinary subdomain scores evaluating acute urinary side effects after treatment (bother, function, incontinence, and irritation or obstruction) had returned to baseline levels by 8 months after implantation. At 5 years, the cumulative risks of late urinary complications by grade were 8.6% for grade 1 complications, 6.5% for grade 2, 1.7% for grade 3%, and 0.5% for grade 4. The most common grade 2 late urinary complications were urethral stricture (4 patients), incontinence requiring daily pads (3 patients), and intermittent hematuria (3 patients). Grade 3 complications were urinary retention requiring self-catheterization (2 patients) and severe frequency with dysuria (2 patients). The only grade 4 event was severe hemorrhagic cystitis. Conclusions: Short-term urinary side effects after prostate brachytherapy are common, follow a predictable course, and typically resolve within 1 year. Conservative management of short-term urinary side effects is recommended to minimize the risk of long-term urinary complications. [Copyright &y& Elsevier]