3-Dimensional Elastic Registration System of Prostate Biopsy Location by Real-Time 3-Dimensional Transrectal Ultrasound Guidance With Magnetic Resonance/Transrectal Ultrasound Image Fusion

Does bladder outflow obstruction obfuscate the traditional clinical factors that are used to assess the risk of prostate cancer at rapid-access diagnostic clinics?

Objectives

To understand whether bladder outflow obstruction influences the association between traditional clinical predictive factors, particularly prostate-specific antigen (PSA) density and clinically significant prostate cancer (csPCa). This will help facilitate effective and evidence-based triaging of patients in rapid-access clinics.

Materials and Methods

We retrospectively analysed prospectively collected data from 307 suspected prostate cancer patients who underwent diagnostic biopsy from 2019 to 2023 at a single, high-volume, specialist cancer centre. Uroflowmetry testing generated two cohorts: patients with bladder outflow obstruction and non-obstructed patients. The cohort characteristics between the groups were compared and logistic regression analyses were performed to assess associations between clinical predictive factors (age, PSA density, ethnicity, family history, digital rectal examination, urinary symptom severity and magnetic resonance imaging using the PI-RADS scoring system) and clinically significant prostate cancer (csPCa) on biopsy (defined as International Society of Urological Pathology grade of greater than or equal to two).

Results

The obstructed group (n = 80) had significantly larger prostates and worse symptom severity (p < 0.05). There was no significant difference between the other predictive factors or csPCa compared to the non-obstructed (n = 227) cohort. Multivariable logistic regression analysis showed age, PSA density, an abnormal digital rectal examination and scoring PI-RADS 4-5 on magnetic resonance imaging were all significantly associated with csPCa in the non-obstructed cohort (p < 0.05). Contrastingly, only symptom severity and scoring PI-RADS 5 were significantly associated with csPCa for the obstructed patients (p < 0.05).

Conclusion

In the presence of bladder outflow obstruction, traditional predictive variables such as age, PSA density, digital rectal examination and scoring PI-RADS 4 are not associated with csPCa. This study suggests that using these predictive variables to triage patients in rapid-access clinics with a patient who has bladder outflow obstruction could lead to the overuse of invasive biopsy.

Role of Systematic Biopsy in the Era of Targeted Biopsy: A Review

Prostate cancer (PCa) is a major public health issue, as the second most common cancer and the fifth leading cause of cancer-related deaths among men. Many PCa cases are indolent and pose minimal risk, making active surveillance a suitable management approach. However, clinically significant prostate carcinoma (csPCa) can lead to serious health issues, including progression, metastasis, and death. Differentiating between insignificant prostate cancer (inPCa) and csPCa is crucial for determining appropriate treatment. Diagnosis of PCa primarily involves trans-perineal and transrectal systematic biopsies. Systematic transrectal prostate biopsy, which typically collects 10-12 tissue samples, is a standard method, but it can miss csPCa and is associated with some complications. Recent advancements, such as magnetic resonance imaging (MRI)-targeted biopsies, have been suggested to improve risk stratification and reduce overtreatment of inPCa and undertreatment of csPCa, thereby enhancing patient quality of life and treatment outcomes. Guided biopsies are increasingly recommended for their ability to better detect high-risk cancers while reducing identification of low-risk cases. MRI-targeted biopsies, especially when used as an initial biopsy in biopsy-naïve patients and those under active surveillance, have become more common. Utilization of MRI-TB alone can decrease septic complications; however, the combining of targeted biopsies with perilesional sampling is recommended for optimal detection of csPCa. Future advancements in imaging and biopsy techniques, including AI-augmented lesion detection and robotic-assisted sampling, promise to further improve the accuracy and effectiveness of PCa detection.

Transperineal Targeted Microwave Ablation (TMA) of localized prostate cancer guided by MRI-Ultrasound fusion and organ-based tracking: a pilot study

BACKGROUND

To investigate the efficacy of transperineal targeted microwave ablation (TMA) in treating localized prostate cancer (PCa).

METHODS

This is a single-centre prospective phase 2 trial recruiting men with low to intermediate-risk localized PCa to undergo transperineal TMA. TMA was performed with MRI-Ultrasound fusion guidance and organ-based tracking. A per-protocol 6-month MRI and biopsy were performed for all patients. The primary outcome was any cancer detected on biopsy of each ablated area. Secondary outcomes included per-patient analysis of positive biopsy, complications, urinary symptom score, erectile function and quality of life (QOL) scores.

RESULTS

In the first 15 men, 23 areas were being treated. The median age was 70 years, number of TMA ablations were 5 (range 2-8), and the total ablation time and operating time was 22 (IQR 14-28) and 75 (IQR 65-85) minutes, respectively. PSA level dropped from a median of 7.7 to 2.4 ng/mL. For the primary outcome, 91.3% (21/23) ablated area had no cancer in 6-month biopsy. In per-patient analysis, 33.3% (5/15) had in or out-of-field positive biopsy at 6 months. Among these five cases, four of them were amenable to active surveillance and 1 (6.7%) case with out-of-field ISUP grade group 2 cancer received radiotherapy. The urinary symptoms, uroflowmetry, erectile function, and QOL scores had no significant difference at 6 months. One patient (out of five patients with normal erection) in the cohort complained of significant worsening of erectile function after TMA. Grade 1 complications including hematuria (33.3%), dysuria (6.7%), and perineal discomfort (13.4%) were observed.

CONCLUSIONS

In this first pilot study, transperineal TMA guided by MRI-Ultrasound fusion guidance and organ-based tracking was shown to be effective, safe, and easily applicable in men with localized PCa.

Transperineal US-MRI Fusion-Guided Biopsy for the Detection of Clinical Significant Prostate Cancer: A Systematic Review and Meta-Analysis Comparing Cognitive and Software-Assisted Technique

INTRODUCTION

We aimed to find potential differences in clinically significant prostate cancer (csPCa) detection rates between transperineal software-assisted fusion biopsy (saFB) and cognitive fusion biopsies (cFB).

METHODS

A systematic review of the literature was performed to identify comparative studies using PubMed, EMBASE, and Scopus according to the PICOS criteria. Cancer detection and complication rates were pooled using the Cochran-Mantel-Haenszel method with the random effect model and reported as odds ratios (ORs), 95% confidence intervals (CI), and p-values. A meta-analysis was performed using Review Manager (RevMan) 5.4 software by Cochrane Collaboration. The quality assessment of the included studies was performed using the Cochrane Risk of Bias tool, using RoB 2 for randomized studies and ROBINS-I for retrospective and nonrandomized ones.

RESULTS

Eight studies were included for the meta-analysis, including 1149 cases in software-based and 963 cases in cognitive fusion biopsy. The detection rates of csPCa were similar between the two groups (OR 1.01, 95% CI 0.74-1.37, p = 0.95). Study heterogeneity was low (I2 55%).

CONCLUSION

There is no actual evidence of the superiority of saFB over cFB in terms of the csPCa detection rate. Operator experience and software availability can drive the choice of one fusion technique over the other.

MRI-informed prostate biopsy: What the radiologist should know on quality in biopsy planning and biopsy acquisition

Quality is currently recognized as the pre-requisite for delivering the clinical benefits expected by magnetic resonance imaging (MRI)-informed prostate biopsy (MRI-i-PB) in patients with a suspicion for clinically significant prostate cancer (csPCa). The "quality chain" underlying MRI-i-PB is multidisciplinary in nature, and depends on several factors related to the patient, imaging technique, image interpretation and biopsy procedure. This review aims at making the radiologist aware of biopsy-related factors impacting on MRI-i-PB quality, both in terms of biopsy planning (threshold for biopsy decisions, association with systematic biopsy and number of targeted cores) and biopsy acquisition (biopsy route, targeting technique, and operator's experience). While there is still space for improvement and better standardization of several biopsy-related procedures, current evidence suggests that high-quality MRI-i-PB can be delivered by acquiring and increased the number of biopsy cores targeted to suspicious imaging findings and perilesional area ("focal saturation biopsy"). On the other hand, uncertainty still exists as to whether software-assisted fusion of MRI and transrectal ultrasound images can outperform cognitive fusion strategy. The role for operator's experience and quality assurance/quality control procedures are also discussed.

Meta-Learning Initializations for Interactive Medical Image Registration

We present a meta-learning framework for interactive medical image registration. Our proposed framework comprises three components: a learning-based medical image registration algorithm, a form of user interaction that refines registration at inference, and a meta-learning protocol that learns a rapidly adaptable network initialization. This paper describes a specific algorithm that implements the registration, interaction and meta-learning protocol for our exemplar clinical application: registration of magnetic resonance (MR) imaging to interactively acquired, sparsely-sampled transrectal ultrasound (TRUS) images. Our approach obtains comparable registration error (4.26 mm) to the best-performing non-interactive learning-based 3D-to-3D method (3.97 mm) while requiring only a fraction of the data, and occurring in real-time during acquisition. Applying sparsely sampled data to non-interactive methods yields higher registration errors (6.26 mm), demonstrating the effectiveness of interactive MR-TRUS registration, which may be applied intraoperatively given the real-time nature of the adaptation process.

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.

Evaluation of systematic prostate biopsies when performing transperineal MRI/TRUS fusion biopsy with needle tracking-what is the additional value?

PURPOSE

To evaluate the additional value of systematic biopsies (SB) when performing transperineal MRI/TRUS fusion biopsies (MRI/TRUS TPBx) with needle tracking.

METHODS

From January 2019 to March 2021 969 Patients after a MRI/TRUS TPBx were evaluated separately for target biopsies (TB) and systematic biopsies regarding PCa detection and PCa risk evaluation. Needle tracking in the axial sequences of multiparametric MRI was used to assess the localisation of the detected PCa in the biopsy cores related to the reported PI-RADS lesions.

RESULTS

The overall cancer detection rate (CDR) for PCa and clinically significant (cs) PCa (ISUP ≥2) with the combination of TB and SB were 66 and 49%. TB detected 46% csPCa and SB 22% csPCa. SB identified 1.5% additional csPCa outside of the reported PI-RADS lesions. 16 patients (1.7%) showed a relevant upgrading from clinically insignificant PCa in TB to csPCa. In 736 patients with unilateral suspicious lesions on MRI, 145 patients (20%) were detected with contralateral PCa-positive SB. 238 patients (25%) showed PCa positive systematic biopsy cores outside of the described PI-RADS lesions.

CONCLUSIONS

Needle tracking optimizes the 3D-localisation of cancer in the prostate. Our results show that the added value of SB with a reduced systematic biopsy scheme is low with regard to prostate cancer (PCa) detection and PCa risk evaluation. However, there is a relevant added value for localizing multifocal PCa in the primary diagnostic by a MRI/TRUS fusion biopsy of the prostate.

Artificial intelligence trained with integration of multiparametric MR-US imaging data and fusion biopsy trajectory-proven pathology data for 3D prediction of prostate cancer: A proof-of-concept study

BACKGROUND

We aimed to develop an artificial intelligence (AI) algorithm that predicts the volume and location of clinically significant cancer (CSCa) using convolutional neural network (CNN) trained with integration of multiparametric MR-US image data and MRI-US fusion prostate biopsy (MRI-US PBx) trajectory-proven pathology data.

METHODS

Twenty consecutive patients prospectively underwent MRI-US PBx, followed by robot-assisted radical prostatectomy (RARP). The AI algorithm was trained with the integration of MR-US image data with a MRI-US PBx trajectory-proven pathology. The relationship with the 3D-cancer-mapping of RARP specimens was compared between AI system-suggested 3D-CSCa mapping and an experienced radiologist's suggested 3D-CSCa mapping on MRI alone according to the Prostate Imaging Reporting and Data System (PI-RADS) version 2. The characteristics of detected and undetected tumors at AI were compared in 22,968 image data. The relationships between CSCa volumes and volumes predicted by AI as well as the radiologist's reading based on PI-RADS were analyzed.

RESULTS

The concordance of the CSCa center with that in RARP specimens was significantly higher in the AI prediction than the radiologist' reading (83% vs. 54%, p = 0.036). CSCa volumes predicted with AI were more accurate (r = 0.90, p < 0.001) than the radiologist's reading. The limitations include that the elastic fusion technology has its own registration error.

CONCLUSIONS

We presented a novel pilot AI algorithm for 3D prediction of PCa. AI was trained by integration of multiparametric MR-US image data and fusion biopsy trajectory-proven pathology data. This deep learning AI model may more precisely predict the 3D mapping of CSCa in its volume and center location than a radiologist's reading based on PI-RADS version 2, and has potential in the planning of focal therapy.

Bi-parametric MRI/TRUS fusion targeted repeat biopsy after systematic 10-12 core TRUS-guided biopsy reveals more significant prostate cancer especially in anteriorly located tumors

Background

MRI and fusion guided biopsy have an increased role in the diagnosis of prostate cancer.

Purpose

To demonstrate the possible advantages with Bi-parametric MRI fusion-guided repeat biopsy over systematic 10-12-core biopsy for the diagnosis of prostate cancer.

Material and Methods

Four hundred and twenty-three consecutive men, with previous systematic 10-12-core TRUS-guided biopsy, and with suspicion of, or diagnosis of, low-risk prostate cancer underwent fusion-guided prostate biopsy between February 2015 and February 2017. The material was retrospectively assessed. In 220 cases no previous cancer was diagnosed, and in 203 cases confirmatory fusion guided biopsy was performed prior to active monitoring. MRI was classified according to PI-RADS. Systematic biopsy was compared to fusion guided biopsy for the detection of cancer, and PI-RADS was compared to the Gleason score.

Results

Fusion guided biopsy detected significantly more cancers than systematic (p < .001). Gleason scores were higher in the fusion biopsy group (p < .001). Anterior tumors were present in 54% of patients. Fusion biopsy from these lesions showed cancer in 53% with previously negative biopsy in systematic biopsies and 66% of them were upgraded from low risk to intermediate or high-risk cancers.

Conclusion

These results show superior detection rate and grading of bi-parametric MRI/TRUS fusion targeted repeat biopsy over systematic 10-12 core biopsies. Fusion guided biopsy detects more significant cancers despite using fewer cores. The risk group was changed for many patients initially selected for active surveillance due to upgrading of tumors. Bi-parametric MRI shows promising results in detecting anterior tumors in patients with suspected prostate cancer.

Optimal biopsy approach for detection of clinically significant prostate cancer

Prostate cancer (PCa) diagnostic and therapeutic work-up has evolved significantly in the last decade, with pre-biopsy multiparametric MRI now widely endorsed within international guidelines. There is potential to move away from the widespread use of systematic biopsy cores and towards an individualised risk-stratified approach. However, the evidence on the optimal biopsy approach remains heterogeneous, and the aim of this review is to highlight the most relevant features following a critical assessment of the literature. The commonest biopsy approaches are via the transperineal (TP) or transrectal (TR) routes. The former is considered more advantageous due to its negligible risk of post-procedural sepsis and reduced need for antimicrobial prophylaxis; the more recent development of local anaesthetic (LA) methods now makes this approach feasible in the clinic. Beyond this, several techniques are available, including cognitive registration, MRI-Ultrasound fusion imaging and direct MRI in-bore guided biopsy. Evidence shows that performing targeted biopsies reduces the number of cores required and can achieve acceptable rates of detection whilst helping to minimise complications and reducing pathologist workloads and costs to health-care facilities. Pre-biopsy MRI has revolutionised the diagnostic pathway for PCa, and optimising the biopsy process is now a focus. Combining MR imaging, TP biopsy and a more widespread use of LA in an outpatient setting seems a reasonable solution to balance health-care costs and benefits, however, local choices are likely to depend on the expertise and experience of clinicians and on the technology available.

Diagnostic performance of fusion (US/MRI guided) prostate biopsy: propensity score matched comparison of elastic versus rigid fusion system

PURPOSE

Many software for US/MRI guided fusion prostate biopsy (FPB), have been developed in the last years. However, there are few data comparing diagnostic accuracy of different fusion systems. We assessed diagnostic performance of elastic (EF) versus rigid fusion (RF) PB in a propensity score matched (PSM) analysis.

METHODS

A total of 314 FPB were prospectively collected from two different centers. All patients were biopsy naïve and all mpMRI reported a single suspicious area. Overall, 211 PB were performed using a RF system and 103 using an EF software. The two groups were compared for the main clinical features. A 1:1 PSM analysis was employed to reduce covariate imbalance to < 10%. Detection rate (DR) for any prostate cancer (PCa) and clinically significant (cs) PCa were compared and stratified for PI-RADS Score. A per target univariable and multivariable regression analyses were applied to identity predictors of anyPCa and csPCa.

RESULTS

After applying the PSM, two cohorts of 83 cases were selected. DR of any PCa cancer and csPCa were comparable between the two cohorts (all p > 0.077) as well as DR of csPCa for every PIRADS score. At univariable regression analysis lesion size, PI-RADS Score, PSA Density and EF system were predictors of any PCa (all p < 0.001); however, at multivariable analysis only PI-RADS Score was independent predictor of any PCa (p = 0.027). At multivariable analysis only PI-RADS score was independent predictor of csPCa.

CONCLUSIONS

Fusion PB guarantees high diagnostic accuracy for csPCa, regardless of the fusion technology. Prospective randomized study is needed to confirm these data.

Virtual reality of three-dimensional surgical field for surgical planning and intraoperative management

PURPOSE

To investigate the impact of virtual reality (VR) technologies on urological surgeries, specifically in the management of prostate cancer and renal cancer.

METHODS

A non-systematic review of the literature was performed. Medline, Pubmed, and the Cochrane Database were screened for studies regarding the use of VR technologies in the management of prostate and renal cancer.

RESULTS

In the management of prostate cancer, VR technologies have been increasingly applied for diagnosis with magnetic resonance imaging/ultrasound fusion biopsy, surgical training using a simulator, surgical navigation in robot-assisted radical prostatectomy, and targeted focal therapy. In partial nephrectomy, surgical simulation and intra-surgical guidance with three-dimensional VR have been used for better understanding of the hilar vascular information, tumor location, and positional relationships of the tumor-feeding vessel and pyelocaliceal system.

CONCLUSIONS

VR contributes to the education, training, and simulation of surgical procedures as well as helping the surgeons to tailor surgical planning on each patient. Further prospective studies are needed to assess the beneficial impacts of this technology for both the physician and patient by objective parameters.

MRI-Targeted Prostate Biopsy Techniques: AJR Expert Panel Narrative Review

Prostate cancer is the second most common malignancy in men worldwide. Systematic transrectal prostate biopsy is commonly used to obtain tissue to establish the diagnosis. However, in recent years, MRI-targeted biopsy (based on an MRI examination performed prior to consideration of biopsy) has been shown to detect more clinically significant cancer and less clinically insignificant cancer compared to systematic biopsy. This approach of performing MRI prior to biopsy has become, or is becoming, a standard of practice in centers throughout the world. This growing use of an MRI-directed pathway is leading to performance of a larger volume of MRI-targeted prostate biopsies. The three common MRI-targeted biopsy techniques are cognitive biopsy, MRI-ultrasound software fusion biopsy, and MRI in-bore guided biopsy. These techniques for using MRI information at the time of biopsy can be performed via a transrectal or transperineal approach. This narrative review presents the three MRI-targeted biopsy techniques along with their advantages and shortcomings. Comparisons among the techniques are summarized based on the available evidence. Studies to date have provided heterogeneous results, and the preferred technique remains debated.

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.

Development of a transperineal prostate biopsy robot guided by MRI-TRUS image

BACKGROUND

In the transrectal ultrasound (TRUS)-guided transperineal prostate biopsy, doctors determine the biopsy target by observing the prostate region in TRUS images. However, ultrasound images with low imaging quality make doctors easy to be interfered when determining the biopsy route, which reduces the biopsy success rate.

METHODS

This paper introduces the guidance method of magnetic resonance image (MRI) registration to ultrasound image and develops a 5-degrees of freedom robot for prostate biopsy guided by MRI-TRUS image. The robot uses a structure attached to the ultrasound probe to reduce the space occupied. By registering the posture relationship between MRI, TRUS image, ultrasonic probe and the robot base, the accurate localization of the suspected lesion area can be achieved with the preoperative MRIs.

RESULTS

The prostate phantom biopsy based on the robotic biopsy system in this paper, the average biopsy error is 1.44 mm, and the maximum biopsy error is 2.23 mm.

CONCLUSIONS

We build a robotic biopsy platform with prostate phantom, and evaluate the biopsy accuracy of MRI-TRUS guided prostate biopsy robot, the results meet clinical prostate biopsy requirements.

Initial phantom studies for an office-based low-field MR system for prostate biopsy

Purpose

Prostate cancer is the second most prevalent cancer in US men, with about 192,000 new cases and 33,000 deaths predicted for 2020. With only a 31% 5-year survival rate for patients with an initial diagnosis of stage-four prostate cancer, the necessity for early screening and diagnosis is clear. In this paper, we present navigation accuracy results for Promaxo’s MR system intended to be used in a physician’s office for image-guided transperineal prostate biopsy.

Methods

The office-based low-field MR system was used to acquire images of prostate phantoms with needles inserted through a transperineal template. Coordinates of the estimated sample core locations in the office-based MR system were compared to ground truth needle coordinates identified in a 1.5T external reference scan. The error was measured as the distance between the planned target and the ground truth core center and as the shortest perpendicular distance between the planned target and the ground truth trajectory of the whole core.

Results

The average error between the planned target and the ground truth core center was 2.57 ± 1.02 mm, [1.93–3.21] 95% CI. The average error between the planned target to the actual core segment was 2.05 ± 1.24 mm, [1.53–2.56] 95% CI.

Conclusion

The average navigation errors were below the clinically significant threshold of 5 mm. The initial phantom results demonstrate the feasibility of the office-based system for prostate biopsy.

Reasons for missing clinically significant prostate cancer by targeted magnetic resonance imaging/ultrasound fusion-guided biopsy

OBJECTIVES

This study evaluates cases with clinically significant prostate cancer (csPCa) missed by targeted biopsy (TB) and analyzes the diagnostic impact of an additional systematic biopsy (SB) in a large patient collective.

METHODS

Consecutive patients with a 3 T multiparametric prostate MRI (mpMRI) and a subsequent MRI/US fusion-guided TB plus 12-core US-guided SB from 01/2014 to 04/2019 were included in this study. Primary study endpoint was the analysis of cases with a csPCa missed by TB and detected by SB. Secondary study objectives were the PCa detection and the correlation with clinical and MRI parameters.

RESULTS

In total 785 patients met the inclusion criteria. 342 patients had a csPCa (median PSAD 0.29 ng/mL/cm³). In 42 patients (13 %), a csPCa was detected only by SB. In 36 of these cases, the localization of the positive SB cores matched with the cancer suspicious region described on mpMRI (mCSR). Cases with a csPCA missed by TB showed either an insufficient MRI segmentation (prostate boundary correlation) (31 %) and/or insufficient lesion registration (lesion transfer, tracking, and/or matching) (48 %), a missed small lesion (14 %), or a failed center of a large lesion (10 %). Median PSAD of patients with non-significant PCa detected by SB was 0.15 ng/mL/cm³.

CONCLUSIONS

Main reasons for missing a csPCa by TB were insufficient prostate segmentation or imprecise lesion registration within MRI/US fusion-guided biopsy. Consequently, verification of MRI quality, exact mCSR assessment, and advanced biopsy experience may improve accuracy. Altogether, an additional SB adds limited clinical benefit in men with PSAD ≤ 0.15 ng/mL/cm³.

Moving away from systematic biopsies: image-guided prostate biopsy (in-bore biopsy, cognitive fusion biopsy, MRUS fusion biopsy) -literature review

OBJECTIVE

To compare the detection rate of clinically significant cancer (CSCa) by magnetic resonance imaging-targeted biopsy (MRI-TB) with that by standard systematic biopsy (SB) and to evaluate the role of MRI-TB as a replacement from SB in men at clinical risk of prostate cancer.

METHODS

The non-systematic literature was searched for peer-reviewed English-language articles using PubMed, including the prospective paired studies, where the index test was MRI-TB and the comparator text was SB. Also the randomized clinical trials (RCTs) are included if one arm was MRI-TB and another arm was SB.

RESULTS

Eighteen prospective studies used both MRI-TB and TRUS-SB, and eight RCT received one of the tests for prostate cancer detection. In most prospective trials to compare MRI-TB vs. SB, there was no significant difference in any cancer detection rate; however, MRI-TB detected more men with CSCa and fewer men with CISCa than SB.

CONCLUSION

MRI-TB is superior to SB in detection of CSCa. Since some significant cancer was detected by SB only, a combination of SB with the TB technique would avoid the underdiagnosis of CSCa.

Validating the Transfer of Skills Acquired on a Prostate Biopsy Simulator: A Prospective, Randomized, Controlled Study

OBJECTIVES

To evaluate the ability of students to reproduce the skills acquired on a prostate biopsy simulator in a real-life situation.

DESIGN

A prospective randomized controlled study was conducted. Medical students with no experience of prostate biopsy were randomized between arm A « conventional training » and arm B « simulator-enhanced training. » The training was performed for both groups on the simulator. The students in arm B were provided with visual and numerical feedback. The transfer of skills was assessed by recording the position of the 12 biopsies performed by each student on an unembalmed human cadaver using a 3D ultrasound mapping device.

SETTING

The study was conducted in an academic urology department and the cadaver experiments in the adjoining anatomy laboratory.

RESULTS

Twenty-four students were included, and 22 completed the study. The median score obtained on the simulator at the end of the training was 57% (53-61) for arm A and 66% (59-71) for arm B. The median score obtained on the cadaver by students trained with the simulator was 75% (60-80), statistically superior to the score obtained by students trained conventionally of 45% (30-60), p < 0.0001. The median score obtained by all students when performing biopsies in a real-life situation was 63% (50-80) versus 60% (56-70) for their last training on the simulator.

CONCLUSION

These results support the transfer of skills acquired on the simulator, and the superiority of a training curriculum integrating simulation, and performance feedback.

Magnetic resonance imaging/transrectal ultrasonography fusion guided seed placement in a phantom: Accuracy between 2-seed versus 1-seed strategies

PURPOSE

To investigate whether the 2-seed placement per Magnetic Resonance Imaging (MRI) suspicious lesion yields a higher seed placement accuracy than a 1-seed strategy on a phantom.

METHODS

Eight olives embedded in gelatin, each simulating a prostate, underwent MRI. Three virtual spherical lesions (3, 5, and 8 mm diameters) were marked in each olive on the MRI images and co-registered to the MRI/Transrectal Ultrasonography (TRUS) fusion biopsy system. Two radiologists placed 0.5 mm fiducials, targeting the center of each virtual lesion under fusion image guidance. Half of the 8 olives in each phantom were assigned either to the 1-seed or 2-seeds per lesion strategy. Post-procedure Computed Tomography (CT) images identified each seed and were fused with MR to localize each virtual lesion and collected the seed placement error - distance between the virtual target and the corresponding seed (using the closer seed for the 2-seed strategy). Seed placement success is defined as fiducial placement within a lesion boundary.

RESULTS

Each operator repeated the procedure on three different phantoms, and data from 209 seeds placed for 137 lesions were analyzed, with an overall error of 3.03 ± 1.52 mm. The operator skill, operator phantom procedural experience, lesion size, and number of seeds, were independently associated with the seed placement error. Seed placement success rate was higher for the 2-seed group compared to 1-seed, although the difference was not statistically significant.

CONCLUSIONS

Placing 2 seeds per MRI lesion yielded a significantly lower error compared to 1-seed strategy, although seed placement success rate was not significantly different.

MRI-directed high-frequency (29MhZ) TRUS-guided biopsies: initial results of a single-center study

OBJECTIVES

To evaluate the ability of high-frequency (29 MHz) transrectal micro-ultrasound (microUS) as a second-look examination after biparametric MRI (bp-MRI) and to reidentify focal lesions seen on diagnostic MRI and to detect new ones METHODS: A total of 118 consecutive men (mean age, 66 ± 13 [SD] years; range, 49-93 years) with a mean prostate-specific antigen level of 11 ± 19 (SD) ng/mL (range, 2-200 ng/mL) and at least one focal lesion (MRI+) with a score > 2 on bp-MRI were included. Of these, 79/118 (66.9%) were biopsy-naïve and 102/118 (86.5%) had non-suspicious rectal examination. All patients had MRI-directed microUS-guided biopsy using a 29-MHz transducer. All lesions visible on micro-ultrasound (microUS+) were targeted without image fusion, which was only used for MRI+/microUS- lesions. Significant prostate cancer (sPCa) was defined by a Gleason score ≥ 7 or a maximum cancer core length > 3 mm.

RESULTS

A total of 144 focal prostatic lesions were analyzed, including 114 (114/144, 79.2%) MRI+/microUS+ lesions, 13 MRI+/microUS- lesions (13/144, 9%), and 17 MRI-/microUS+ lesions (17/144, 11.8%). Significant PCa was detected in 70 MRI+/microUS+ lesions (70/114, 61.4%), in no MRI+/microUS- lesion (0/13, 0%), and in 4 MRI-/microUS+ lesions (4/17, 23.5%). The sensitivity and specificity of microUS on a per-patient and a per-lesion basis were 100% (95% CI, 84.9-100%) and 22.8% (95% CI, 12.5-35.8%) and 100% (95% CI, 85.1-100%) and 22.6% (95% CI, 12.3-36.2%), respectively.

CONCLUSION

MicroUS, as a second-look examination, may show promise to localize targets detected on bp-MRI.

KEY POINTS

• Used as a second-look examination, microUS-guided biopsies have a 100% detection rate of sCa originating in the PZ or lower third of the TZ, without microUS-MRI image fusion. • MicroUS results may provide additional information about lesions visible on MRI. • MicroUS may provide the ability to detect small PZ lesions undetected by bp-MRI.

Cartography-based quality control of prostate cancer care: a necessary ground to targeted focal therapy

PURPOSE OF REVIEW

We summarize the evidence on accurate target definition, precise imaging, and guiding systems that are a necessary ground to targeted focal therapy.

RECENT FINDINGS

Accurate target detection is based on the ability of imaging to locate and characterize precisely the tumor burden and differentiation inside the prostate. There is a clear correlation with the multiparametric MRI (mpMRI) images and the morphologic attributes of the tumor. Limitations stem from the heterogeneity and the multifocality of prostate cancer. Some prostate cancers are MRI-negative tumors. Safety margins should also be elaborated based on the tumor grade and burden. PET prostate specific membrane antigen is another promising technology yielding same results as multiparametric MRI for primary detection of prostate cancer, but PET/MRI imaging is promising. Perfect guiding requires sophisticated software with good quality control to track the needle inside the prostate and to record the position allowing recall when second look biopsy, active surveillance, or targeted focal therapy are required.

SUMMARY

The multimodal fusion cartography model proves effective and necessary to fulfill preoperative and postoperative requirements for targeted focal therapy.

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.

Focal salvage low-dose-rate brachytherapy for recurrent prostate cancer based on magnetic resonance imaging/transrectal ultrasound fusion biopsy technique

OBJECTIVE

To examine the effect of permanent salvage brachytherapy in prostate cancer patients suffering recurrence after three-dimensional conformal external beam radiotherapy.

METHODS

The ultra-focal (target lesion alone), hemi-lobe (within a hemi-lobe) or focused whole-gland (focusing on the lesion, but extending into the whole gland) pattern was selected based on the Gleason score for the targeted biopsy, the numbers of positive cores in the targeted and systematic biopsies, and the locations of the positive cores. Novel dosimetry criteria derived from three-dimensional cancer mapping, which was based on targeted magnetic resonance imaging/transrectal ultrasound fusion biopsies, were used in these cases.

RESULTS

Permanent salvage brachytherapy was carried out in 13 patients who suffered prostate-specific antigen failure (prostate-specific antigen 2.1-6.8 ng/mL; age range 57-75 years; Gleason score ≤7 [n = 10], Gleason score ≥8 [n = 2] and Gleason score not available [n = 1]) since 2012. The targeted biopsy showed a single focus in three patients. The ultra-focal, hemi-lobe and focused whole-gland patterns were chosen in three, five and five patients, respectively. During the follow-up period (median duration 48 months), prostate-specific antigen failure occurred in zero of three, one of five and three of five of the patients treated with the ultra-focal, hemi-lobe and focused whole-gland patterns, respectively. The 4-year biochemical recurrence-free survival rate was 74%. No grade 3-4 adverse intestinal or urological events occurred.

CONCLUSIONS

Targeted fusion biopsy-based three-dimensional cancer mapping should be used for permanent salvage brachytherapy treatment planning to reduce the incidence of treatment-related adverse events while maintaining good oncological outcomes.

Robotic Transrectal Ultrasound Guided Prostate Biopsy

We present a robot-assisted approach for transrectal ultrasound (TRUS) guided prostate biopsy. The robot is a hands-free probe manipulator that moves the probe with the same 4 DoF that are used manually. Software was developed for three-dimensional (3-D) imaging, biopsy planning, robot control, and navigation. Methods to minimize the deformation of the prostate caused by the probe at 3-D imaging and needle targeting were developed to reduce biopsy targeting errors. We also present a prostate coordinate system (PCS). The PCS helps defining a systematic biopsy plan without the need for prostate segmentation. Comprehensive tests were performed, including two bench tests, one imaging test, two in vitro targeting tests, and an IRB-approved clinical trial on five patients. Preclinical tests showed that image-based needle targeting can be accomplished with accuracy on the order of 1 mm. Prostate biopsy can be accomplished with minimal TRUS pressure on the gland and submillimetric prostate deformations. All five clinical cases were successful with an average procedure time of 13 min and millimeter targeting accuracy. Hands-free TRUS operation, transrectal TRUS guided prostate biopsy with minimal prostate deformations, and the PCS-based biopsy plan are novel methods. Robot-assisted prostate biopsy is safe and feasible. Accurate needle targeting has the potential to increase the detection of clinically significant prostate cancer.

Magnetic resonance imaging/transrectal ultrasound fusion-targeted prostate biopsy using three-dimensional ultrasound-based organ-tracking technology: Initial experience in Japan

OBJECTIVE

To evaluate the impact of magnetic resonance imaging/transrectal ultrasound fusion-targeted prostate biopsy on the diagnosis of clinically significant prostate cancer using real-time three-dimensional ultrasound-based organ-tracking technology.

METHODS

The present study was a retrospective review of 262 consecutive patients with prostate-specific antigen of 7.1 ng/mL (interquartile range 4.0-19.8). All patients received pre-biopsy magnetic resonance imaging and had a suspicious lesion for clinically significant prostate cancer. All patients underwent a combination of systematic biopsy (6 cores) and three-dimensional ultrasound-based magnetic resonance imaging/transrectal ultrasound fusion-targeted biopsy (2 cores). The positive rate of any cancer, positive rate of clinically significant prostate cancer, Gleason score and maximum cancer core length were compared between systematic biopsy versus magnetic resonance imaging/transrectal ultrasound fusion-targeted prostate biopsy.

RESULTS

Overall, the positive rate of any cancer per patient was 61% (160/262) in systematic biopsy versus 79% (207/262) in magnetic resonance imaging/transrectal ultrasound fusion-targeted biopsy (P < 0.0001); and that of clinically significant prostate cancer per patient was 46% (120/262) in systematic biopsy versus 70% (181/262) in magnetic resonance imaging/transrectal ultrasound fusion-targeted biopsy (P < 0.0001). The positive rate of any cancer per core was 21.7% (330/1523) in systematic biopsy versus 68.6% (406/592) in magnetic resonance imaging/transrectal ultrasound fusion-targeted biopsy (P < 0.0001), and that of clinically significant prostate cancer per core was 12.7% (193/1423) in systematic biopsy versus 60.3% (357/592) in magnetic resonance imaging/transrectal ultrasound fusion-targeted biopsy (P < 0.0001). Adding systematic biopsy leads to 13 more cancer cases (5%). The distribution of Gleason score (6/7/8/9/10) was 59/71/23/6/1 in systematic biopsy versus 48/105/36/15/2 in magnetic resonance imaging/transrectal ultrasound fusion-targeted biopsy (P = 0.005). The maximum cancer core length was 5 mm (0.5-16) in systematic biopsy versus 8 mm (1-19 mm) in magnetic resonance imaging/transrectal ultrasound fusion-targeted biopsy (P < 0.0001).

CONCLUSIONS

Three-dimensional ultrasound-based magnetic resonance imaging/transrectal ultrasound fusion-targeted biopsy seems to be associated with a higher detection rate of clinically significant prostate cancer, with fewer cores than systematic random biopsy. However, significant cancer can still be detected by the systematic technique only. A combination of systematic biopsy with the targeted biopsy technique would avoid the underdiagnosis of clinically significant prostate cancer.

A review of optimal prostate biopsy: indications and techniques

Prostate biopsy is the gold standard diagnostic technique for the detection of prostate cancer. Patient selection for prostate biopsy is complex and is influenced by emerging use of prebiopsy imaging. The introduction of the magnetic resonance imaging (MRI)-transrectal ultrasound (TRUS) fusion prostate biopsy has clear advantages over the historical standard of care. There are several biopsy techniques currently utilized with unique advantages and disadvantages. We review and summarize the current body of literature pertaining to when and how a prostate biopsy should be performed. We discuss current recommendations regarding patient selection for biopsy and discuss future directions regarding prebiopsy imaging. We offer a description of the MRI-TRUS fusion biopsy technique and a comparison of many of the currently available fusion software platforms. Articles pertaining to the title were obtained via PubMed index search with relevant keywords supplemented with personal collection of related publications. Prostate biopsy should be considered for patients with gross digital rectal exam (DRE) abnormality, patients with a prostate-specific antigen (PSA) greater than 4 ng/ml, and concomitant risk factors for prostate cancer or patients with lesions identified on multiparametric MRI (mpMRI) with Prostate Imaging Reporting and Data System 2 (PI-RADS2) score of 4 or 5. MRI-TRUS fusion biopsy has demonstrated advantages in cancer detection when compared with TRUS-guided biopsy. There are currently several fusion software platforms available with a variety of biopsy approaches. Future efforts should detail the role of prebiopsy imaging as a triage tool for prostate biopsy. Consensus should be sought regarding the preferred modality of fusion biopsy. Additional data describing each fusion software platform would enable a more rigorous comparison of platform sensitivities.

Detection rate of clinically significant prostate cancer in magnetic resonance imaging and ultrasonography-fusion transperineal targeted biopsy for lesions with a prostate imaging reporting and data system version 2 score of 3-5

Objectives

To evaluate the detection rates of clinically significant prostate cancer classified according to the prostate imaging reporting and data system scoring system using magnetic resonance imaging/ultrasound rigid fusion targeted biopsy.

Methods

A total of 339 patients underwent transperineal magnetic resonance imaging/ultrasound rigid fusion targeted biopsy in our institution between January 2015 and July 2017. Patients with prostate imaging reporting and data system category 1 or 2 and those with a pre‐biopsy prostate‐specific antigen value of >30 ng/mL were excluded from this study. Finally, 310 patients were recruited.

Results

The detection rates of clinically significant prostate cancer with prostate imaging reporting and data system category 3, 4, and 5 were 1.0% (1/98), 35.1% (47/134) and 73.1% (57/78), respectively. The factors affecting the detection of clinically significant prostate cancer with prostate imaging reporting and data system categories 4 and 5 were: (i) prostate imaging reporting and data system category 5; (ii) prostate volume <40 cc; (iii) no previous biopsy; (iv) lesion located in the peripheral zone; and (v) prostate‐specific antigen density >0.35 ng/mL/mL.

Conclusions

The detection rate of clinically significant prostate cancer on magnetic resonance imaging/ultrasound rigid fusion targeted biopsy is very low in patients with prostate imaging reporting and data system category 3; therefore, patients with this classification should not undergo targeted biopsy. Prostate‐specific antigen density, prostate volume, locations of suspected cancer and history of biopsy should be considered to predict the detection rate of clinically significant prostate cancer with prostate imaging reporting and data system categories 4 and 5.

Accuracy of elastic fusion biopsy in daily practice: Results of a multicenter study of 2115 patients

OBJECTIVES

To assess the accuracy of Koelis fusion biopsy for the detection of prostate cancer and clinically significant prostate cancer in the everyday practice.

METHODS

We retrospectively enrolled 2115 patients from 15 institutions in four European countries undergoing transrectal Koelis fusion biopsy from 2010 to 2017. A variable number of target (usually 2-4) and random cores (usually 10-14) were carried out, depending on the clinical case and institution habits. The overall and clinically significant prostate cancer detection rates were assessed, evaluating the diagnostic role of additional random biopsies. The cancer detection rate was correlated to multiparametric magnetic resonance imaging features and clinical variables.

RESULTS

The mean number of targeted and random cores taken were 3.9 (standard deviation 2.1) and 10.5 (standard deviation 5.0), respectively. The cancer detection rate of Koelis biopsies was 58% for all cancers and 43% for clinically significant prostate cancer. The performance of additional, random cores improved the cancer detection rate of 13% for all cancers (P < 0.001) and 9% for clinically significant prostate cancer (P < 0.001). Prostate cancer was detected in 31%, 66% and 89% of patients with lesions scored as Prostate Imaging Reporting and Data System 3, 4 and 5, respectively. Clinical stage and Prostate Imaging Reporting and Data System score were predictors of prostate cancer detection in multivariate analyses. Prostate-specific antigen was associated with prostate cancer detection only for clinically significant prostate cancer.

CONCLUSIONS

Koelis fusion biopsy offers a good cancer detection rate, which is increased in patients with a high Prostate Imaging Reporting and Data System score and clinical stage. The performance of additional, random cores seems unavoidable for correct sampling. In our experience, the Prostate Imaging Reporting and Data System score and clinical stage are predictors of prostate cancer and clinically significant prostate cancer detection; prostate-specific antigen is associated only with clinically significant prostate cancer detection, and a higher number of biopsy cores are not associated with a higher cancer detection rate.

The emerging role of imaging in prostate cancer secondary screening: multiparametric magnetic resonance imaging and the incipient incorporation of molecular imaging

An increasingly robust body of evidence indicates that multiparametric MRI (mpMRI) prior to prostate biopsy can improve the detection of clinically significant prostate cancer while avoiding unnecessary biopsies. As a result, the use of mpMRI and biopsy platforms that allow for the real-time fusion of mpMRI and transrectal ultrasound images is now routinely used in clinical practice. On the horizon, molecular imaging offers the promise of improved sensitivity relative to mpMRI and early data would suggest that the combination of mpMRI and positron emission tomography using radiotracers targeting prostate-specific membrane antigen provide a more accurate assessment than either modality alone. In this review, we examine the current role of imaging to aid in the initial diagnosis of prostate cancer.

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

PURPOSE

The relative value of rigid or elastic registration during magnetic resonance imaging/ultrasound fusion guided prostate biopsy has been poorly studied. We compared registration errors (the distance between a region of interest and fiducial markers) between rigid and elastic registration during fusion guided prostate biopsy using a prostate phantom model.

MATERIALS AND METHODS

Four gold fiducial markers visible on magnetic resonance imaging and ultrasound were placed throughout 1 phantom prostate model. The phantom underwent magnetic resonance imaging and the fiducial markers were labeled as regions of interest. An experienced user and a novice user of fusion guided prostate biopsy targeted regions of interest and then the corresponding fiducial markers on ultrasound after rigid and then elastic registration. Registration errors were compared.

RESULTS

A total of 224 registration error measurements were recorded. Overall elastic registration did not provide significantly improved registration error over rigid registration (mean ± SD 4.87 ± 3.50 vs 4.11 ± 2.09 mm, p = 0.05). However, lesions near the edge of the phantom showed increased registration errors when using elastic registration (5.70 ± 3.43 vs 3.23 ± 1.68 mm, p = 0.03). Compared to the novice user the experienced user reported decreased registration error with rigid registration (3.25 ± 1.49 vs 4.98 ± 2.10 mm, p <0.01) and elastic registration (3.94 ± 2.61 vs 6.07 ± 4.16 mm, p <0.01).

CONCLUSIONS

We found no difference in registration errors between rigid and elastic registration overall but rigid registration decreased the registration error of targets near the prostate edge. Additionally, operator experience reduced registration errors regardless of the registration method. Therefore, elastic registration algorithms cannot serve as a replacement for attention to detail during the registration process and anatomical landmarks indicating accurate registration when beginning the procedure and before targeting each region of interest.

Follow-up of negative MRI-targeted prostate biopsies: when are we missing cancer?

INTRODUCTION

Multiparametric magnetic resonance imaging (mpMRI) has improved clinicians' ability to detect clinically significant prostate cancer (csPCa). Combining or fusing these images with the real-time imaging of transrectal ultrasound (TRUS) allows urologists to better sample lesions with a targeted biopsy (Tbx) leading to the detection of greater rates of csPCa and decreased rates of low-risk PCa. In this review, we evaluate the technical aspects of the mpMRI-guided Tbx procedure to identify possible sources of error and provide clinical context to a negative Tbx.

METHODS

A literature search was conducted of possible reasons for false-negative TBx. This includes discussion on false-positive mpMRI findings, termed "PCa mimics," that may incorrectly suggest high likelihood of csPCa as well as errors during Tbx resulting in inexact image fusion or biopsy needle placement.

RESULTS

Despite the strong negative predictive value associated with Tbx, concerns of missed disease often remain, especially with MR-visible lesions. This raises questions about what to do next after a negative Tbx result. Potential sources of error can arise from each step in the targeted biopsy process ranging from "PCa mimics" or technical errors during mpMRI acquisition to failure to properly register MRI and TRUS images on a fusion biopsy platform to technical or anatomic limits on needle placement accuracy.

CONCLUSIONS

A better understanding of these potential pitfalls in the mpMRI-guided Tbx procedure will aid interpretation of a negative Tbx, identify areas for improving technical proficiency, and improve both physician understanding of negative Tbx and patient-management options.

Technical Note: Error metrics for estimating the accuracy of needle/instrument placement during transperineal magnetic resonance/ultrasound-guided prostate interventions

PURPOSE

Image-guided systems that fuse magnetic resonance imaging (MRI) with three-dimensional (3D) ultrasound (US) images for performing targeted prostate needle biopsy and minimally invasive treatments for prostate cancer are of increasing clinical interest. To date, a wide range of different accuracy estimation procedures and error metrics have been reported, which makes comparing the performance of different systems difficult.

METHODS

A set of nine measures are presented to assess the accuracy of MRI-US image registration, needle positioning, needle guidance, and overall system error, with the aim of providing a methodology for estimating the accuracy of instrument placement using a MR/US-guided transperineal approach.

RESULTS

Using the SmartTarget fusion system, an MRI-US image alignment error was determined to be 2.0 ± 1.0 mm (mean ± SD), and an overall system instrument targeting error of 3.0 ± 1.2 mm. Three needle deployments for each target phantom lesion was found to result in a 100% lesion hit rate and a median predicted cancer core length of 5.2 mm.

CONCLUSIONS

The application of a comprehensive, unbiased validation assessment for MR/US guided systems can provide useful information on system performance for quality assurance and system comparison. Furthermore, such an analysis can be helpful in identifying relationships between these errors, providing insight into the technical behavior of these systems.

Assessment of Needle Tip Deflection During Transrectal Guided Prostate Biopsy: Implications for Targeted Biopsies

OBJECTIVES

To measure needle tip deflection during transrectal ultrasound (TRUS) prostate biopsy and evaluate predictors for needle tip deflection.

MATERIALS AND METHODS

Analysis of 568 prostate biopsies obtained from 51 consecutive patients who underwent a standard 12-core TRUS guided prostate biopsy. TRUS guided prostate biopsies were performed using BK flex500, with a side-fire biplane probe. Each biopsy core image was captured and clinical data were recorded prospectively. The angle between the expected trajectory of the needle and actual needle course was measured using the longitudinal view of the captured image. The distance between expected and actual needle tip was calculated. We measured median and interquartile needle tip deflection rate stratified by side and location (apex, midgland, base). Univariable and multivariable linear regressions analysis were performed.

RESULTS

The overall median needle tip deflection was 1.77 mm (IQR 1.35-2.47). Location did not significantly alter needle deflection measurements. On multivariable linear regression analysis, higher prostate volume (B = 0.007 95%, CI 0.004, 0.011; p < 0.001) and the right sided biopsy (B = 0.191 95%, CI 0.047, 0.336; p = 0.010) emerged as predictors of higher needle tip deflection.

CONCLUSIONS

To the best of our knowledge this is the first study to measure needle tip deflection during TRUS guided prostate biopsies. We demonstrated that larger prostate size and biopsy side may affect the accuracy of biopsies. These results may have clinical implication to those performing targeted biopsies.

The Current State of MR Imaging-targeted Biopsy Techniques for Detection of Prostate Cancer

Systematic transrectal ultrasonography (US)-guided biopsy is the standard approach for histopathologic diagnosis of prostate cancer. However, this technique has multiple limitations because of its inability to accurately visualize and target prostate lesions. Multiparametric magnetic resonance (MR) imaging of the prostate is more reliably able to localize significant prostate cancer. Targeted prostate biopsy by using MR imaging may thus help to reduce false-negative results and improve risk assessment. Several commercial devices are now available for targeted prostate biopsy, including in-gantry MR imaging-targeted biopsy and real-time transrectal US-MR imaging fusion biopsy systems. This article reviews the current status of MR imaging-targeted biopsy platforms, including technical considerations, as well as advantages and challenges of each technique. ^© RSNA, 2017.

Application of Prostate Imaging Reporting and Data System Version 2 (PI-RADS v2): Interobserver Agreement and Positive Predictive Value for Localization of Intermediate- and High-Grade Prostate Cancers on Multiparametric Magnetic Resonance Imaging

RATIONALE AND OBJECTIVES

To evaluate interobserver agreement with the use of and the positive predictive value (PPV) of Prostate Imaging Reporting and Data System version 2 (PI-RADS v2) for the localization of intermediate- and high-grade prostate cancers on multiparametric magnetic resonance imaging (mpMRI).

MATERIALS AND METHODS

In this retrospective, institutional review board-approved study, 131 consecutive patients who had mpMRI followed by transrectal ultrasound-MR imaging fusion-guided biopsy of the prostate were included. Two readers who were blinded to initial mpMRI reports, clinical data, and pathologic outcomes reviewed the MR images, identified all prostate lesions, and scored each lesion based on the PI-RADS v2. Interobserver agreement was assessed by intraclass correlation coefficient (ICC), and PPV was calculated for each PI-RADS category.

RESULTS

PI-RADS v2 was found to have a moderate level of interobserver agreement between two readers of varying experience, with ICC of 0.74, 0.72, and 0.67 for all lesions, peripheral zone lesions, and transitional zone lesions, respectively. Despite only moderate interobserver agreement, the calculated PPV in the detection of intermediate- and high-grade prostate cancers for each PI-RADS category was very similar between the two readers, with approximate PPV of 0%, 12%, 64%, and 87% for PI-RADS categories 2, 3, 4, and 5, respectively.

CONCLUSIONS

In our study, PI-RADS v2 has only moderate interobserver agreement, a similar finding in studies of the original PI-RADS and in initial studies of PI-RADS v2. Despite this, PI-RADS v2 appears to be a useful system to predict significant prostate cancer, with PI-RADS scores correlating well with the likelihood of intermediate- and high-grade cancers.

Diagnostic accuracy of a five-point Likert scoring system for magnetic resonance imaging (MRI) evaluated according to results of MRI/ultrasonography image-fusion targeted biopsy of the prostate

OBJECTIVE

To evaluate the accuracy of a magnetic resonance imaging (MRI)-based Likert scoring system in the detection of clinically significant prostate cancer (CSPC), using MRI/ultrasonography (US) image-fusion targeted biopsy (FTB) as a reference standard.

PATIENTS AND METHODS

We retrospectively reviewed 1218 MRI-detected lesions in 629 patients who underwent subsequent MRI/US FTB between October 2012 and August 2015. 3-Tesla MRI was independently reported by one of eight radiologists with varying levels of experience and scored on a five-point Likert scale. All lesions with Likert scores 1-5 were prospectively defined as targets for MRI/US FTB. CSPC was defined as Gleason score ≥7.

RESULTS

The median patient age was 64 years, PSA level 6.97 ng/mL and estimated prostate volume 52.2 mL. Of 1218 lesions, 48% (n = 581) were rated as Likert 1-2, 35% (n = 428) were Likert 3 and 17% (n = 209) were Likert 4-5. For Likert scores 1-5, the overall cancer detection rates were 12%, 13%, 22%, 50% and 59%, respectively, and the CSPC detection rates were 4%, 4%, 12%, 33% and 48%, respectively. Grading using the five-point scale showed strong positive correlation with overall cancer detection rate (r = 0.949, P = 0.05) and CSPC detection rate (r = 0.944, P = 0.05). By comparison, in Likert 4-5 lesions, significant differences were noted in overall cancer detection rate (63% vs 35%; P = 0.001) and CSPC detection rate (47% vs 29%; P = 0.027) for the more experienced vs the less experienced radiologists.

CONCLUSIONS

The detection rates of overall cancer and CSPC strongly correlated with the five-point grading of the Likert scale. Among radiologists with different levels of experience, there were significant differences in these cancer detection rates.

Real-time registration of 3D to 2D ultrasound images for image-guided prostate biopsy

PURPOSE

During image-guided prostate biopsy, needles are targeted at tissues that are suspicious of cancer to obtain specimen for histological examination. Unfortunately, patient motion causes targeting errors when using an MR-transrectal ultrasound (TRUS) fusion approach to augment the conventional biopsy procedure. This study aims to develop an automatic motion correction algorithm approaching the frame rate of an ultrasound system to be used in fusion-based prostate biopsy systems. Two modes of operation have been investigated for the clinical implementation of the algorithm: motion compensation using a single user initiated correction performed prior to biopsy, and real-time continuous motion compensation performed automatically as a background process.

METHODS

Retrospective 2D and 3D TRUS patient images acquired prior to biopsy gun firing were registered using an intensity-based algorithm utilizing normalized cross-correlation and Powell's method for optimization. 2D and 3D images were downsampled and cropped to estimate the optimal amount of image information that would perform registrations quickly and accurately. The optimal search order during optimization was also analyzed to avoid local optima in the search space. Error in the algorithm was computed using target registration errors (TREs) from manually identified homologous fiducials in a clinical patient dataset. The algorithm was evaluated for real-time performance using the two different modes of clinical implementations by way of user initiated and continuous motion compensation methods on a tissue mimicking prostate phantom.

RESULTS

After implementation in a TRUS-guided system with an image downsampling factor of 4, the proposed approach resulted in a mean ± std TRE and computation time of 1.6 ± 0.6 mm and 57 ± 20 ms respectively. The user initiated mode performed registrations with in-plane, out-of-plane, and roll motions computation times of 108 ± 38 ms, 60 ± 23 ms, and 89 ± 27 ms, respectively, and corresponding registration errors of 0.4 ± 0.3 mm, 0.2 ± 0.4 mm, and 0.8 ± 0.5°. The continuous method performed registration significantly faster (P < 0.05) than the user initiated method, with observed computation times of 35 ± 8 ms, 43 ± 16 ms, and 27 ± 5 ms for in-plane, out-of-plane, and roll motions, respectively, and corresponding registration errors of 0.2 ± 0.3 mm, 0.7 ± 0.4 mm, and 0.8 ± 1.0°.

CONCLUSIONS

The presented method encourages real-time implementation of motion compensation algorithms in prostate biopsy with clinically acceptable registration errors. Continuous motion compensation demonstrated registration accuracy with submillimeter and subdegree error, while performing < 50 ms computation times. Image registration technique approaching the frame rate of an ultrasound system offers a key advantage to be smoothly integrated to the clinical workflow. In addition, this technique could be used further for a variety of image-guided interventional procedures to treat and diagnose patients by improving targeting accuracy.

Safety and Feasibility of Direct Magnetic Resonance Imaging-guided Transperineal Prostate Biopsy Using a Novel Magnetic Resonance Imaging-safe Robotic Device

OBJECTIVE

To evaluate safety and feasibility in a first-in-human trial of a direct magnetic resonance imaging (MRI)-guided prostate biopsy using a novel robotic device.

METHODS

MrBot is an MRI-safe robotic device constructed entirely with nonconductive, nonmetallic, and nonmagnetic materials and developed by our group. A safety and feasibility clinical trial was designed to assess the safety and feasibility of a direct MRI-guided biopsy with MrBot and to determine its targeting accuracy. Men with elevated prostate-specific antigen levels, prior negative prostate biopsies, and cancer-suspicious regions (CSRs) on MRI were enrolled in the study. Biopsies targeting CSRs, in addition to sextant locations, were performed.

RESULTS

Five men underwent biopsy with MrBot. Two men required Foley catheter insertion after the procedure, with no other complications or adverse events. Even though this was not a study designed to detect prostate cancer, biopsies confirmed the presence of a clinically significant cancer in 2 patients. On a total of 30 biopsy sites, the robot achieved an MRI-based targeting accuracy of 2.55 mm and a precision of 1.59 mm normal to the needle, with no trajectory corrections and no unsuccessful attempts to target a site.

CONCLUSION

Robot-assisted MRI-guided prostate biopsy appears safe and feasible. This study confirms that a clinically significant prostate cancer (≥5-mm radius, 0.5 cm³) depicted in MRI may be accurately targeted. Direct confirmation of needle placement in the CSR may present an advantage over fusion-based technology and gives more confidence in a negative biopsy result. Additional study is warranted to evaluate the efficacy of this approach.

Multimodal Imaging in Focal Therapy Planning and Assessment in Primary Prostate Cancer

PURPOSE

There is increasing interest in focal therapy (male lumpectomy) of localized low-intermediate risk prostate cancer. Focal therapy is typically associated with low morbidity and provides the possibility of retreatment. Imaging is pivotal in stratification of men with localized prostate cancer for active surveillance, focal therapy or radical intervention. This article provides a concise review of focal therapy and the evolving role of imaging in this clinical setting.

METHODS

We performed a narrative and critical literature review by searching PubMed/Medline database from January 1997 to January 2017 for articles in the English language and the use of search keywords "focal therapy", "prostate cancer", and "imaging".

RESULTS

Most imaging studies are based on multiparametric magnetic resonance imaging. Transrectal ultrasound is inadequate independently but multiparametric ultrasound may provide new prospects. Positron emission tomography with radiotracers targeted to various underlying tumor biological features may provide unprecedented new opportunities. Multimodal Imaging appears most useful in localization of intraprostatic dominant index lesions amenable to focal therapy, in early assessment of therapeutic efficacy and potential need for additional focal treatments or transition to whole-gland therapy, and in predicting short-term and long-term outcomes.

CONCLUSION

Multimodal imaging is anticipated to play an increasing role in the focal therapy planning and assessment of low-intermediate risk prostate cancer and thereby moving this form of treatment option forward in the clinic.

Direct magnetic resonance imaging-guided biopsy of the prostate: lessons learned in establishing a regional referral center

MRI-targeted biopsy of the prostate appears to have the potential to reduce the high rates of underdiagnosis and overdiagnosis associated with the current diagnostic standard of transrectal ultrasound guided systematic biopsy. Direct or "in bore" MRI-guided biopsy is one of the three methods for MRI-targeted core needle sampling of suspicious, generally Pi-RADS 4 or 5, foci within the prostate, and our early experience suggests the approach demonstrates substantial utility and promise in the care of patients with prostate cancer. We performed direct MRI-guided biopsies in 50 patients within 19 months of establishing the first referral center for this service in our region. Our preliminary results indicate the service can be easily grown due to unmet demand, primarily in patients with a negative traditional systematic biopsy but with a concerning focus at MRI (30 of 50; 60%). Other applications include evaluation of patients who are on active surveillance (n=14; ten upgraded to higher Gleason score at MRI-guided biopsy), who are biopsy naïve (n=5; all positive at MRI-guided biopsy), or post focal therapy (n=1; positive for recurrent tumor at MRI-guided biopsy). With careful patient selection and technique, we have achieved a favorable overall positive biopsy rate of 73% (37 of 50), with 84% (31 of 37) positive biopsies demonstrating Gleason score 7 or greater disease. Large multicenter comparative trials will be required to determine the relative accuracy and appropriate utilization of direct MRI guided biopsy in the care pathway of patients with known or suspected prostate cancer.

Development and Phantom Validation of a 3-D-Ultrasound-Guided System for Targeting MRI-Visible Lesions During Transrectal Prostate Biopsy

OBJECTIVE

Three- and four-dimensional transrectal ultrasound transducers are now available from most major ultrasound equipment manufacturers, but currently are incorporated into only one commercial prostate biopsy guidance system. Such transducers offer the benefits of rapid volumetric imaging, but can cause substantial measurement distortion in electromagnetic tracking sensors, which are commonly used to enable 3-D navigation. In this paper, we describe the design, development, and validation of a 3-D-ultrasound-guided transrectal prostate biopsy system that employs high-accuracy optical tracking to localize the ultrasound probe and prostate targets in 3-D physical space.

METHODS

The accuracy of the system was validated by evaluating the targeted needle placement error after inserting a biopsy needle to sample planned targets in a phantom using standard 2-D ultrasound guidance versus real-time 3-D guidance provided by the new system.

RESULTS

The overall mean needle-segment-to-target distance error was 3.6 ± 4.0 mm and mean needle-to-target distance was 3.2 ± 2.4 mm.

CONCLUSION

A significant increase in needle placement accuracy was observed when using the 3-D guidance system compared with visual targeting of invisible (virtual) lesions using a standard B-mode ultrasound-guided biopsy technique.