Use of magnetic resonance imaging in low-dose-rate and high-dose-rate prostate brachytherapy from diagnosis to treatment assessment: Defining the knowledge gaps, technical challenges, and barriers to implementation

AAPM Task Group Report 303 endorsed by the ABS: MRI Implementation in HDR Brachytherapy-Considerations from Simulation to Treatment

The Task Group (TG) on Magnetic Resonance Imaging (MRI) Implementation in High Dose Rate (HDR) Brachytherapy - Considerations from Simulation to Treatment, TG 303, was constituted by the American Association of Physicists in Medicine's (AAPM's) Science Council under the direction of the Therapy Physics Committee, the Brachytherapy Subcommittee, and the Working Group on Brachytherapy Clinical Applications. The TG was charged with developing recommendations for commissioning, clinical implementation, and on-going quality assurance (QA). Additionally, the TG was charged with describing HDR brachytherapy (BT) workflows and evaluating practical consideration that arise when implementing MR imaging. For brevity, the report is focused on the treatment of gynecologic and prostate cancer. The TG report provides an introduction and rationale for MRI implementation in BT, a review of previous publications on topics including available applicators, clinical trials, previously published BT related TG reports, and new image guided recommendations beyond CT based practices. The report describes MRI protocols and methodologies, including recommendations for the clinical implementation and logical considerations for MR imaging for HDR BT. Given the evolution from prescriptive to risk-based QA,¹ an example of a risk-based analysis using MRI-based, prostate HDR BT is presented. In summary, the TG report is intended to provide clear and comprehensive guidelines and recommendations for commissioning, clinical implementation, and QA for MRI-based HDR BT that may be utilized by the medical physics community to streamline this process. This report is endorsed by the American Brachytherapy Society (ABS). This article is protected by copyright. All rights reserved.

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

AIM/OBJECTIVES/BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

Adherence to established standards can help to ensure that permanent prostate brachytherapy is delivered in a safe and efficacious manner.

Prospective Evaluation of Prostate and Organs at Risk Segmentation Software for MRI-based Prostate Radiation Therapy

The segmentation of the prostate and surrounding organs at risk (OARs) is a necessary workflow step for performing dose-volume histogram analyses of prostate radiation therapy procedures. Low-dose-rate prostate brachytherapy (LDRPBT) is a curative prostate radiation therapy treatment that delivers a single fraction of radiation over a period of days. Prior studies have demonstrated the feasibility of fully convolutional networks to segment the prostate and surrounding OARs for LDRPBT dose-volume histogram analyses. However, performance evaluations have been limited to measures of global similarity between algorithm predictions and a reference. To date, the clinical use of automatic segmentation algorithms for LDRPBT has not been evaluated, to the authors' knowledge. The purpose of this work was to assess the performance of fully convolutional networks for prostate and OAR delineation on a prospectively identified cohort of patients who underwent LDRPBT by using clinically relevant metrics. Thirty patients underwent LDRPBT and were imaged with fully balanced steady-state free precession MRI after implantation. Custom automatic segmentation software was used to segment the prostate and four OARs. Dose-volume histogram analyses were performed by using both the original automatically generated contours and the physician-refined contours. Dosimetry parameters of the prostate, external urinary sphincter, and rectum were compared without and with the physician refinements. This study observed that physician refinements to the automatic contours did not significantly affect dosimetry parameters. Keywords: MRI, Neural Networks, Radiation Therapy, Radiation Therapy/Oncology, Genital/Reproductive, Prostate, Segmentation, Dosimetry Supplemental material is available for this article. © RSNA, 2022.

American brachytherapy society radiation oncology alternative payment model task force: Quality measures and metrics for brachytherapy

PURPOSE

Brachytherapy is an essential technique to deliver radiation therapy and is involved in the treatment of multiple disease sites as monotherapy or as an adjunct to external beam radiation therapy. With a growing focus on the cost and value of cancer treatments as well new payment models, it is essential that standardized quality measures and metrics exist to allow for straightforward assessment of brachytherapy quality and for the development of clinically significant and relevant clinical data elements. We present the American Brachytherapy Society consensus statement on quality measures and metrics for brachytherapy as well as suggested clinical data elements.

METHODS AND MATERIALS

Members of the American Brachytherapy Society with expertise in disease site specific brachytherapy created a consensus statement based on a literature review and clinical experience.

RESULTS

Key quality measures (ex. workup, clinical indications), dosimetric metrics, and clinical data elements for brachytherapy were evaluated for each modality including breast cancer, cervical cancer, endometrial cancer, prostate cancer, keratinocyte carcinoma, soft tissue sarcoma, and uveal melanoma.

CONCLUSIONS

This consensus statement provides standardized quality measures and dosimetric quality metrics as well as clinical data elements for each disease site to allow for standardized assessments of brachytherapy quality. Moving forward, a similar paradigm can be considered for external beam radiation therapy as well, providing comprehensive radiation therapy quality measures, metrics, and clinical data elements that can be incorporated into new payment models.

Multi-Parameter Magnetic Resonance Imaging Fusion Technology Assists in Bone Diagnosis and Rehabilitation of Prostate Cancer

Multi-parameter magnetic resonance imaging has been widely used in the diagnosis and evaluation of prostate cancer, and has important guiding significance for clinical diagnosis of prostate cancer and their treatment. This article studies the value of transrectal multiparametric ultrasound (mpUSS) in the diagnosis of clinically meaningful prostate cancer. 102 patients with high risk factors for prostate cancer were examined by mpUSS and mpMRI. The transrectal biopsy (SB) results of the prostate system were regarded as the excellent standard, and the diagnostic value of mpUSS, mpMRl and mpUSS combined with mpMRl examination for clinically meaningful prostate cancer was analyzed. The results showed that 58 of the 102 patients with SB were diagnosed with prostate cancer. Among them, 43 cases were detected by mpUSS, 50 cases were detected by mpMRl, 42 cases were detected by mpUSS combined with mpMRI (series), and 56 cases were detected by mpUSS combined with mpMRl (parallel). Grouped by Gleason score, the detection rate of mpUSS for clinically significant prostate cancer was 83.74%, and the detection rate of mpMRl was 93.5%. The comparison between the two was not statistically significant (P > 0.05), but when the two inspection methods were combined. The detection rate was 97.8%, which was significantly higher than the two inspection methods alone. Therefore, we conclude that mpUSS can be used as an imaging test for the diagnosis of prostate cancer. In addition, mpUSS has a high application value in the diagnosis of prostate cancer. The detection rate of mpUSS combined with mpMRl examination for clinically meaningful prostate cancer is significantly higher than that of mpMRl examination alone, which can be used as a diagnostic technique for early diagnosis of meaningful prostate cancer and can be used as a guide clinicians’ early diagnosis and treatment of meaningful prostate cancer.

Interobserver variability of 3.0-tesla and 1.5-tesla magnetic resonance imaging/computed tomography fusion image-based post-implant dosimetry of prostate brachytherapy

This study aimed to compare the interobserver variabilities in magnetic resonance imaging (MRI)/computed tomography (CT) fusion image-based post-implant dosimetry of permanent prostate brachytherapy (PPB) between 1.5-T and 3.0-T MRI. The study included 60 patients. Of these patients, 30 underwent 1.5-T MRI and CT 30 days after seed implantation (1.5-T group), and 30 underwent 3.0-T MRI and CT 30 days after seed implantation (3.0-T group). All patients received PPB alone. Two radiation oncologists performed MRI/CT fusion image-based post-implant dosimetry, and the interobserver variabilities of dose-volume histogram (DVH) parameters [dose (Gy) received by 90% of the prostate volume (prostate D90)], percentage of the prostate volume receiving at least the full prescribed dose (prostate V100), percentage of the prostate volume receiving at least 150% of the prescribed dose (prostate V150), dose (Gy) received by 5% of the urethral volume (urethral D5) and the urethral volume receiving at least 150% of the prescribed dose (urethral V150)] were retrospectively estimated using the paired Student's t test and Pearson's correlation coefficient. The Pearson's correlation coefficients of all DVH parameters were higher in the 3.0-T group than in the 1.5-T group (1.5-T vs 3.0-T: prostate D90, 0.65 vs 0.93; prostate V100, 0.62 vs 0.82; prostate V150, 0.97 vs 0.98; urethral D5, 0.92 vs 0.93; and urethral V150, 0.88 vs 0.93). In the paired Student's t test, no significant differences were observed in any of the DVH parameters between the two radiation oncologists in the 3.0-T group (0.068 ≤ P ≤ 0.842); however, significant differences were observed in prostate D90 (P = 0.004), prostate V100 (P = 0.011) and prostate V150 (P = 0.002) between the oncologists in the 1.5-T group. The interobserver variability of DVH parameters in the MRI/CT fusion image-based post-implant dosimetry analysis of brachytherapy was lower with 3.0-T MRI than with 1.5-T MRI.

Diffusion weighted MRI as an early predictor of tumor response to hypofractionated stereotactic boost for prostate cancer

We evaluated the feasibility of using the kinetic of diffusion-weighted MRI (DWI) and the normalized apparent coefficient diffusion (ADC) map value as an early biomarker in patients treated by external beam radiotherapy (EBRT). Twelve patients were included within the frame of a multicenter phase II trial and treated for intermediate risk prostate cancer (PCa). Multiparametric MRI was performed before treatment (M0) and every 6 months until M24. Association between nADC and PSA or PSA kinetic was evaluated using the test of nullity of the Spearman correlation coefficient. The median rates of PSA at the time of diagnosis, two years and four years after EBRT were 9.29 ng/ml (range from 5.26 to 17.67), 0.68 ng/ml (0.07–2.7), 0.47 ng/ml (0.09–1.39), respectively. Median nADC increased from 1.14 × 10⁻³ mm²/s to 1.59 × 10⁻³ mm²/s between M0 and M24. Only one patient presented a decrease of nADC (1.35 × 10⁻³ mm²/s and 1.11 × 10⁻³ mm²/s at M0 and M12 respectively). The increase in nADC at M6 was correlated with PSA decrease at M18, M24 and M30 (p < 0.05). The increase in nADc at M12 was correlated with PSA decrease at M36 (p = 0.019). Early nADC variation were correlated with late PSA decrease for patients with PCa treated by EBRT.

Validation of MRI to TRUS registration for high-dose-rate prostate brachytherapy

PURPOSE

The objective of this study was to develop and validate an open-source module for MRI to transrectal ultrasound (TRUS) registration to support tumor-targeted prostate brachytherapy.

METHODS AND MATERIALS

In this study, 15 patients with prostate cancer lesions visible on multiparametric MRI were selected for the validation. T2-weighted images with 1-mm isotropic voxel size and diffusion weighted images were acquired on a 1.5T Siemens imager. Three-dimensional (3D) TRUS images with 0.5-mm slice thickness were acquired. The investigated registration module was incorporated in the open-source 3D Slicer platform, which can compute rigid and deformable transformations. An extension of 3D Slicer, SlicerRT, allows import of and export to DICOM-RT formats. For validation, similarity indices, prostate volumes, and centroid positions were determined in addition to registration errors for common 3D points identified by an experienced radiation oncologist.

RESULTS

The average time to compute the registration was 35 ± 3 s. For the rigid and deformable registration, respectively, Dice similarity coefficients were 0.87 ± 0.05 and 0.93 ± 0.01 while the 95% Hausdorff distances were 4.2 ± 1.0 and 2.2 ± 0.3 mm. MRI volumes obtained after the rigid and deformable registration were not statistically different (p > 0.05) from reference TRUS volumes. For the rigid and deformable registration, respectively, 3D distance errors between reference and registered centroid positions were 2.1 ± 1.0 and 0.4 ± 0.1 mm while registration errors between common points were 3.5 ± 3.2 and 2.3 ± 1.1 mm. Deformable registration was found significantly better (p < 0.05) than rigid registration for all parameters.

CONCLUSIONS

An open-source MRI to TRUS registration platform was validated for integration in the brachytherapy workflow.