Comparison of Elastic and Rigid Registration during Magnetic Resonance Imaging/Ultrasound Fusion-Guided Prostate Biopsy: A Multi-Operator Phantom Study

Targeted biopsy of the prostate

Diagnostic multiparametric MRI of the prostate has steadily evolved over the last three decades and can now reliably depict the dominant tumor in most men with prostate cancer. In response, several methods of targeted biopsy to direct tissue sampling of suspected tumor foci seen at multiparametric MRI have been developed and successfully tested in recent years, including software-assisted MRI-ultrasound (US) fusion biopsy and direct MRI-guided in-bore biopsy. These advances are leading to a sea change in the approach to prostate cancer diagnosis, with the traditional approach of blind systematic biopsy increasingly being replaced by MRI directed targeted biopsy. This review aims to describe the current status of targeted biopsy, with an emphasis on the relative accuracy of different techniques. The results of several critical large multicenter trials are presented, while unanswered questions that require more research are highlighted.

Early Detection of Prostate Cancer: AUA/SUO Guideline Part II: Considerations for a Prostate Biopsy

PURPOSE

The summary presented herein covers recommendations on the early detection of prostate cancer and provides a framework to facilitate clinical decision-making in the implementation of prostate cancer screening, biopsy, and follow-up. This is Part II of a two-part series focusing on initial and repeat biopsies, and biopsy technique. Please refer to Part I for discussion of initial prostate cancer screening recommendations.

MATERIALS AND METHODS

The systematic review utilized to inform this guideline was conducted by an independent methodological consultant. The systematic review was based on searches in Ovid MEDLINE and Embase and Cochrane Database of Systematic Reviews (January 1, 2000-November 21, 2022). Searches were supplemented by reviewing reference lists of relevant articles.

RESULTS

The Early Detection of Prostate Cancer Panel developed evidence- and consensus-based guideline statements to provide guidance in prostate cancer screening, initial and repeat biopsies, and biopsy technique.

CONCLUSIONS

The evaluation of prostate cancer risk should be focused on the detection of clinically significant prostate cancer (Grade Group 2 or higher [GG2+]). The use of laboratory biomarkers, prostate MRI, and biopsy techniques described herein may improve detection and safety when a prostate biopsy is deemed necessary following prostate cancer screening.

Feasibility and preliminary clinical tolerability of low-field MRI-guided prostate biopsy

OBJECTIVE

We evaluate the clinical feasibility of a portable, low-field magnetic resonance imaging (MRI) system for prostate cancer (PCa) biopsy.

METHODS

A retrospective analysis of men who underwent a 12-core systematic transrectal ultrasound-guided prostate biopsy (SB) and a low-field MRI guided transperineal targeted biopsy (MRI-TB). Comparison of the detection of clinically significant PCa (csPCa) (Gleason Grade [GG] ≥ 2) by SB and low field MRI-TB, stratified by Prostate Imaging Reporting & Data System (PI-RADS) score, prostate volume, and prostate serum antigen (PSA) was performed.

RESULTS

A total of 39 men underwent both the MRI-TB and SB biopsy. Median (interquartile range [IQR]) age was 69.0 (61.5-73) years, body mass index (BMI) was 28.9 kg/m² (25.3-34.3), prostate volume was 46.5 cc (32-72.7), and PSA was 9.5 ng/ml (5.5-13.2). The majority (64.4%) of patients had PI-RADS ≥ 4 lesions and 25% of lesions were anterior on pre-biopsy MRII. Cancer detection rate (CDR) was greatest when combining SB and MRI-TB (64.1%). MRI-TB detected 74.3% (29/39) cancers. Of which, 53.8% (21/39) were csPCa while SB detected 42.5% (17/39) csPCa (p = 0.21). In 32.5% (13/39) of cases, MRI-TB upstaged the final diagnosis, compared to 15% (6/39) of cases in which SB upstaged the final diagnosis (p = 0.11).

CONCLUSION

Low-field MRI-TB is clinically feasible. Although future studies on the accuracy of MRI-TB system are needed, the initial CDR is comparable to those seen with fusion-based prostate biopsies. A transperineal and targeted approach may be beneficial in patients with higher BMI and anterior lesions.

Quality checkpoints in the MRI-directed prostate cancer diagnostic pathway

Multiparametric MRI of the prostate is now recommended as the initial diagnostic test for men presenting with suspected prostate cancer, with a negative MRI enabling safe avoidance of biopsy and a positive result enabling MRI-directed sampling of lesions. The diagnostic pathway consists of several steps, from initial patient presentation and preparation to performing and interpreting MRI, communicating the imaging findings, outlining the prostate and intra-prostatic target lesions, performing the biopsy and assessing the cores. Each component of this pathway requires experienced clinicians, optimized equipment, good inter-disciplinary communication between specialists, and standardized workflows in order to achieve the expected outcomes. Assessment of quality and mitigation measures are essential for the success of the MRI-directed prostate cancer diagnostic pathway. Quality assurance processes including Prostate Imaging-Reporting and Data System, template biopsy, and pathology guidelines help to minimize variation and ensure optimization of the diagnostic pathway. Quality control systems including the Prostate Imaging Quality scoring system, patient-level outcomes (such as Prostate Imaging-Reporting and Data System MRI score assignment and cancer detection rates), multidisciplinary meeting review and audits might also be used to provide consistency of outcomes and ensure that all the benefits of the MRI-directed pathway are achieved.

Biomechanical modelling of the pelvic system: improving the accuracy of the location of neoplasms in MRI-TRUS fusion prostate biopsy

Background

An accurate knowledge of the relocation of prostate neoplasms during biopsy is of great importance to reduce the number of false negative results. Prostate neoplasms are visible in magnetic resonance images (MRI) but it is difficult for the practitioner to locate them at the time of performing a transrectal ultrasound (TRUS) guided biopsy. In this study, we present a new methodology, based on simulation, that predicts both prostate deformation and lesion migration during the biopsy.

Methods

A three-dimensional (3-D) anatomy model of the pelvic region, based on medical images, is constructed. A finite element (FE) numerical simulation of the organs motion and deformation as a result of the pressure exerted by the TRUS probe is carried out using the Code-Aster open-source computer software. Initial positions of potential prostate lesions prior to biopsy are taken into consideration and the final location of each lesion is targeted in the FE simulation output.

Results

Our 3-D FE simulations show that the effect of the pressure exerted by the TRUS probe is twofold as the prostate experiences both a motion and a deformation of its original shape. We targeted the relocation of five small prostate lesions when the TRUS probe exerts a force of 30 N on the rectum inner wall. The distance travelled by these lesions ranged between 5.6 and 13.9 mm.

Conclusions

Our new methodology can help to predict the location of neoplasms during a prostate biopsy but further studies are needed to validate our results. Moreover, the new methodology is completely developed on open-source software, which means that its implementation would be affordable to all healthcare providers.

Impact of Surgeon's Experience in Rigid versus Elastic MRI/TRUS-Fusion Biopsy to Detect Significant Prostate Cancer Using Targeted and Systematic Cores

Simple Summary

For the transfer of suspicious lesions in magnetic resonance imaging (MRI) to ultrasound in prostate fusion biopsy, biopsy platforms can be distinguished by rigid or elastic image registration. This study evaluates the detection rate of these different platforms for transperineal fusion-guided prostate biopsy to detect clinically significant prostate cancer under consideration of the surgeon’s learning curve. In our cohort, rigid and elastic registration systems showed a similar prostate cancer detection rate in experienced surgeons, whereas novices seem to benefit from rigid fusion. In the total cohort, targeted fusion biopsy with a rigid registration system outperformed elastic registration target biopsy with a superior significant prostate cancer detection rate, each compared to systematic saturation biopsy. Thus, rigid target biopsy aided in reducing targeting errors that result in missing MRI-visualized significant prostate cancer. These results can provide valuable decision support in selecting a biopsy fusion platform to increase the detection rate and risk stratification of prostate cancer, especially at the beginning of the surgeon’s learning curve.

Abstract

Multiparametric magnetic resonance imaging (mpMRI) and MRI/ultrasound fusion-targeted prostate biopsy (FB) have excellent sensitivity in detecting significant prostate cancer (sPC). FB platforms can be distinguished by rigid (RTB) or elastic image registration (ETB). We compared RTB and ETB by analyzing sPC detection rates of both RTB and ETB at different stages of the surgeons’ learning curve. Patients undergoing RTB between 2015–2017 (n = 502) were compared to patients undergoing ETB from 2017–2019 (n = 437). SPC detection rates were compared by Chi-square-test on patient-basis. Combination of transperineal systematic biopsy and each TB served as reference and sub-analyses were performed for different grades of surgeon’s experience. In the RTB subgroup, 233 men (46%) had sPC, compared to 201 (46%) in the ETB subgroup. RTB alone detected 94% of men with sPC and ETB 87% (p = 0.02). However, for at least intermediate-experienced surgeons (>100 FB), no differences occurred between RTB and ETB. In the total cohort, at least intermediate-experienced surgeons detected significantly more sPC (10%, p = 0.008) than novices. Thus, targeted transperineal MRI/TRUS-FB with a RTB registration system showed a similar sPC detection rate to ETB in experienced surgeons but a superior sPC detection rate to ETB in the total cohort. Low-experienced surgeons seem to benefit from RTB.

Multiparametric ultrasound of prostate: role in prostate cancer diagnosis

Recent advances in ultrasonography (US) technology established modalities, such as Doppler-US, HistoScanning, contrast-enhanced ultrasonography (CEUS), elastography, and micro-ultrasound. The early results of these US modalities have been promising, although there are limitations including the need for specialized equipment, inconsistent results, lack of standardizations, and external validation. In this review, we identified studies evaluating multiparametric ultrasonography (mpUS), the combination of multiple US modalities, for prostate cancer (PCa) diagnosis. In the past 5 years, a growing number of studies have shown that use of mpUS resulted in high PCa and clinically significant prostate cancer (CSPCa) detection performance using radical prostatectomy histology as the reference standard. Recent studies have demonstrated the role mpUS in improving detection of CSPCa and guidance for prostate biopsy and therapy. Furthermore, some aspects including lower costs, real-time imaging, applicability for some patients who have contraindication for magnetic resonance imaging (MRI) and availability in the office setting are clear advantages of mpUS. Interobserver agreement of mpUS was overall low; however, this limitation can be improved using standardized and objective evaluation systems such as the machine learning model. Whether mpUS outperforms MRI is unclear. Multicenter randomized controlled trials directly comparing mpUS and multiparametric MRI are warranted.

High-Intensity Focused Ultrasound (HIFU) Focal Therapy for Localized Prostate Cancer with MRI-US Fusion Platform

Objective

The study aimed at investigating the outcome of prostate HIFU focal therapy using the MRI-US fusion platform for treatment localization and delivery.

Methods

It is a prospectively designed case series of HIFU focal therapy for localized prostate cancer. The inclusion criteria include clinical tumor stage ≤T2, visible index lesion on multiparametric MRI less than 20 mm in diameter, absence of Gleason 5 pattern on prostate biopsy, and PSA ≤ 20 ng/ml. HIFU focal therapy was performed in the conventional manner in the beginning 50% of the series, whereas the subsequent cases were performed with MRI-US fusion platform. The primary outcome was treatment failure rate which is defined by the need of salvage therapy. Secondary outcomes included tumor recurrence in follow-up biopsy, PSA change, perioperative complications, and postoperative functional outcomes.

Results

Twenty patients underwent HIFU focal ablation. HIFU on an MRI-US fusion platform had a trend of a longer total operative time than the conventional counterpart (124.2 min vs. 107.1 min, p=0.066). There was no difference in the mean ablation volume to lesion volume ratio between the two. The mean PSA percentage change from baseline to 6-month is more significant in the conventional group (63.3% vs. 44.6%, p=0.035). No suspicious lesion was seen at 6-month mpMRI in all 20 patients. Two patients, one from each group, eventually underwent radical treatment because of the presence of clinically significant prostate cancer in the form of out-of-field recurrences during follow-up biopsy. No significant difference was observed before and after HIFU concerning uroflowmetry, SF-12 score, and EPIC-26 score. It was observed that energy used per volume was positively correlated with PSA density of the patient (r = 0.6364, p=0.014).

Conclusion

In conclusion, HIFU with conventional or MRI-US fusion platform provided similar oncological and functional outcomes.

In-Bore Versus Fusion MRI-Targeted Biopsy of PI-RADS Category 4 and 5 Lesions: A Retrospective Comparative Analysis Using Propensity Score Weighting

BACKGROUND. Few published studies have compared in-bore and fusion MRI-targeted prostate biopsy, and the available studies have had conflicting results. OBJECTIVE. The purpose of this study was to compare the target-specific cancer detection rate of in-bore prostate biopsy with that of fusion MRI-targeted biopsy. METHODS. The records of men who underwent in-bore or fusion MRI-targeted biopsy of PI-RADS category 4 or 5 lesions between August 2013 and September 2019 were retrospectively identified. PI-RADS version 2.1 assessment category, size, and location of each target were established by retrospective review by a single experienced radiologist. Patient history and target biopsy results were obtained by electronic medical record review. Only the first MRI-targeted biopsy of the dominant lesion was included for patients with repeated biopsies or multiple targets. In-bore and fusion biopsy were compared by propensity score weights and multivariable regression to adjust for imbalances in patient and target characteristics between biopsy techniques. The primary endpoint was target-specific prostate cancer detection rate. Secondary endpoints were detection rate after application of propensity score weighting for cancers in International Society of Urological Pathology (ISUP) grade group 2 (GG2) or higher and detection rate with the use of off-target systematic sampling results. RESULTS. The study sample included 286 men (in-bore biopsy, 191; fusion biopsy, 95). Compared with fusion biopsy, in-bore biopsy was associated with significantly greater likelihood of detection of any cancer (odds ratio, 2.28 [95% CI, 1.04-4.98]; p = .04) and nonsignificantly greater likelihood of detection of ISUP GG2 or higher cancer (odds ratio, 1.57 [95% CI, 0.88-2.79]; p = .12) in a target. When off-target sampling was included, in-bore biopsy and combined fusion and systematic biopsy were not different for detection of any cancer (odds ratio, 1.16 [95% CI, 0.54-2.45]; p = .71) or ISUP GG2 and higher cancer (odds ratio, 1.15 [95% CI, 0.66-2.01]; p = .62). CONCLUSION. In this retrospective study in which propensity score weighting was used, in-bore MRI-targeted prostate biopsy had a higher target-specific cancer detection rate than did fusion biopsy. CLINICAL IMPACT. Pending a larger prospective randomized multicenter comparison between in-bore and fusion biopsy, in-bore may be the preferred approach should performing only biopsy of a suspicious target, without concurrent systematic biopsy, be considered clinically appropriate.

Usability and diagnostic accuracy of different MRI/ultrasound-guided fusion biopsy systems for the detection of clinically significant and insignificant prostate cancer: a prospective cohort study

PURPOSE

To explore the usability and diagnostic accuracy for prostate cancer of three multiparametric magnetic resonance imaging (mpMRI)/transrectal ultrasound (TRUS)-guided fusion biopsy systems operated by the same urologists.

METHODS

We performed a prospective, observational study including patients that underwent prostate biopsy due to a visible lesion in mpMRI (PI-RADS ≥ 3). We consecutively assessed two platforms with a rigid image registration (BioJet, D&K Technologies and UroNav, Invivo Corporation) and one with an elastic registration (Trinity, KOELIS). Four urologists evaluated each fusion system in terms of usability based on the System Usability Scale and diagnostic accuracy based on the detection of prostate cancer.

RESULTS

We enrolled 60 consecutive patients that received mpMRI/TRUS-guided prostate biopsy with the BioJet (n = 20), UroNav (n = 20) or Trinity (n = 20) fusion system. Comparing the rigid with the elastic registration systems, the rigid registration systems were more user-friendly compared to the elastic registration systems (p = 0.012). Similarly, the prostate biopsy with the rigid registration systems had a shorter duration compared to the elastic registration system (p < 0.001). Overall, 40 cases of prostate cancer were detected. Of them, both the BioJet and UroNav fusion systems detected 13 prostate cancer cases, while the Trinity detected 14. No significant differences were demonstrated among the three fusion biopsy systems in terms of highest ISUP Grade Group (p > 0.99).

CONCLUSIONS

Rigid fusion biopsy systems are easier to use and provide shorter operative time compared to elastic systems, while both types of platforms display similar detection rates for prostate cancer. Still, further high-quality, long-term results are mandatory.

Techniques and Outcomes of MRI-TRUS Fusion Prostate Biopsy

PURPOSE OF REVIEW

The goal of this study is to review recent findings and evaluate the utility of MRI transrectal ultrasound fusion biopsy (FBx) techniques and discuss future directions.

RECENT FINDINGS

FBx detects significantly higher rates of clinically significant prostate cancer (csPCa) than ultrasound-guided systematic prostate biopsy (SBx), particularly in repeat biopsy settings. FBx has also been shown to detect significantly lower rates of clinically insignificant prostate cancer. In addition, a dedicated prostate MRI can assist in more accurately predicting the Gleason score and provide further information regarding the index cancer location, prostate volume, and clinical stage. The ability to accurately evaluate specific lesions is vital to both focal therapy and active surveillance, for treatment selection, planning, and adequate follow-up. FBx has been demonstrated in multiple high-quality studies to have improved performance in diagnosis of csPCa compared to SBx. The combination of FBx with novel technologies including radiomics, prostate-specific membrane antigen positron emission tomography (PSMA PET), and high-resolution micro-ultrasound may have the potential to further enhance this performance.

Magnetic resonance imaging/transrectal ultrasonography fusion targeted prostate biopsy finds more significant prostate cancer in biopsy-naïve Japanese men compared with the standard biopsy

OBJECTIVE

To assess the clinical benefits of magnetic resonance imaging/transrectal ultrasound fusion-targeted biopsy for biopsy-naïve Japanese men.

METHODS

Between February 2017 and August 2018, 131 biopsy-naïve men who underwent targeted biopsy together with 10-core systematic biopsy at Hiroshima University Hospital were retrospectively investigated. Multiparametric magnetic resonance imaging findings were reported based on Prostate Imaging Reporting and Data System version 2.

RESULTS

The overall cancer detection rates per patient were 69.5% in systematic biopsy + targeted biopsy cores, 61.1% in systematic biopsy cores and 61.1% in targeted biopsy cores. The detection rates for clinically significant prostate cancer were 43.5% in targeted biopsy cores and 35.9% in systematic biopsy cores (P = 0.04), whereas the detection rates for clinically insignificant prostate cancer were 17.6% and 25.2% respectively (P = 0.04). Lesions in the peripheral zone were diagnosed more with clinically significant prostate cancer (54.8% vs 20.7%, P < 0.001) and International Society of Urological Pathology grade (3.2 vs 2.7, P = 0.02) than that in the inner gland. Just 4.2% (3/71) of Prostate Imaging Reporting and Data System category 2 and 3 lesions in the middle or base of the inner gland were found to have clinically significant prostate cancer. The cancer detection rate per core was 42.3% in targeted biopsy cores, whereas it was 17.9% in systematic biopsy cores (P < 0.001).

CONCLUSIONS

Targeted biopsy is able to improve the diagnostic accuracy of biopsy in detection of clinically significant prostate cancer by reducing the number of clinically insignificant prostate cancer detections compared with 10-core systematic biopsy in biopsy-naïve Japanese men. In addition, the present findings suggest that patients with Prostate Imaging Reporting and Data System category 2 or 3 lesions at the middle or base of the inner gland might avoid biopsies.

The use of prostate MR for targeting prostate biopsies

Management of prostate cancer relies heavily on accurate risk stratification obtained through biopsies, which are conventionally performed under transrectal ultrasound (TRUS) guidance. Yet, multiparametric MRI has grown to become an integral part of the care of males with known or suspected prostate cancer. This article will discuss in detail the different MRI-targeted biopsy techniques, their advantages and disadvantages, and the impact they have on patient management.

Magnetic resonance imaging-transrectal ultrasound image fusion guidance of prostate biopsies: current status, challenges and future perspectives

The use of multiparametric magnetic resonance imaging (mpMRI) in prostate cancer (PCa) diagnosis is rapidly evolving to try to overcome the limitations of the current diagnostic pathway using systematic transrectal ultrasound-guided biopsies (TRUS_bx) for all men with clinical suspicion of PCa. Prostate mpMRI allows for high quality lesion detection and characterization and has been shown to improve detection of significant PCa with a more accurate Gleason score grading. Suspicious lesions can be stratified by suspicion and sampled by selective MRI-guided targeted biopsies (TBx) for improved diagnostic accuracy. Several TBx methods have been established and include MRI/TRUS image fusion biopsies (cognitive or software-assisted) and in-bore biopsies, but none have yet proven superior in clinical practice. However, while MRI in-bore biopsy is not routinely used due to its costs and limited availability, MRI/TRUS image fusion is rapidly embraced as it allows skilled urologists to perform TBx in an outpatient clinic. Furthermore, it gives the operator the advantage of adding TBx to the systematic standard biopsy scheme, which is the currently recommended approach. With the anticipated increased future use of prebiopsy mpMRI, a more widespread implementation of MRI/TRUS image fusion platforms is concurrently expected in clinical practice. Therefore, the objective of this review is to assess the current status, challenges and future perspectives of prostate MRI/TRUS image fusion biopsies.

[Fusion biopsies for primary diagnosis of prostate cancer : Implementation, benefits, and clinical aspects]

Prostate carcinoma is one of the most common tumors worldwide. Histological confirmation by biopsy is an obligatory part of the diagnostic approach. The main problem of the 10-12-fold transrectal ultrasound-guided (TRUS) biopsy, which has so far been regarded as the gold standard, is the underdiagnosis of clinically significant cancer. MRI-based procedures, so-called fusion biopsies, have shown superior results when compared to conventional biopsies. There are three different approaches (cognitive and software-based MRI/TRUS fusion and in-bore biopsy) with comparable detection rates but differences in the technical aspects and time involvement. In order to reduce fusion errors, targeted biopsies should consist of multiple cores. There is currently no clear preference for the access pathway (transrectal or transperineal), but clinical parameters such as infection risk or location of the tumor can influence the decision. While the German S3 guideline considers MRI prior to primary biopsy to be optional, the 2019 European Association of Urology guidelines already recommend MRI prior to biopsy for all patients. The combination of MRI-targeted and systematic biopsy offers the highest detection rates with the disadvantage that more low-risk tumors are diagnosed. Both the patient and the urologist benefit from an improved informative value of the biopsy when deciding on active surveillance as well as when planning invasive therapies.