Thirty-two-channel coil 3T magnetic resonance-guided biopsies of prostate tumor suspicious regions identified on multimodality 3T magnetic resonance imaging: technique and feasibility

Paradigm Shift in Prostate Cancer Diagnosis: Pre-Biopsy Prostate Magnetic Resonance Imaging and Targeted Biopsy

With regard to the indolent clinical characteristics of prostate cancer (PCa), the more selective detection of clinically significant PCa (CSC) has been emphasized in its diagnosis and management. Magnetic resonance imaging (MRI) has advanced technically, and recent international cooperation has provided a standardized imaging and reporting system for prostate MRI. Accordingly, prostate MRI has recently been investigated and utilized as a triage tool before biopsy to guide tissue sampling to increase the detection rate of CSC beyond the staging tool for patients in whom PCa was already confirmed on conventional systematic biopsy. Radiologists must understand the current paradigm shift for better PCa diagnosis and management. This article reviewed the recent literature, demonstrating the diagnostic value of pre-biopsy prostate MRI with targeted biopsy and discussed unsolved issues regarding the paradigm shift in the diagnosis of PCa.

Clinical implementation of pre-biopsy magnetic resonance imaging pathways for the diagnosis of prostate cancer

Objective

To assess the outcomes of pre‐biopsy magnetic resonance imaging (MRI) pathways, as a tool in biopsy‐naïve men with suspicion of prostate cancer, in routine clinical practice. Secondary outcomes included a comparison of transrectal MRI‐directed biopsy (TR‐MRDB) and transperineal (TP)‐MRDB in men with suspicious MRI.

Patients and Methods

We retrospectively assessed a two‐centre cohort of consecutive biopsy‐naïve men with suspicion of prostate cancer who underwent a Prostate Imaging‐Reporting and Data System version 2 (PI‐RADS v2) compliant pre‐biopsy MRI in a single, high‐volume centre between 2015 and 2019 (Centre 1). Men with suspicious MRI scans underwent TR‐MRDB in Centre 1 and TP‐MRDB with additional random biopsies (RB) in Centre 2. The MRI and histopathology were assessed in the same institution (Centre 1). Outcomes included: (i) overall detection rates of Grade Group (GG) 1, GG ≥2, and GG ≥3 cancer in men with suspicious MRI; (ii) Biopsy‐avoidance due to non‐suspicious MRI; and (iii) Cancer detection rates and biopsy‐related complications between TR‐ and TP‐MRDB. To reduce confounding bias for MRDB comparisons, inverse probability weighting (IPW) was performed for age, digital rectal examination, prostate‐specific antigen (PSA), prostate volume, PSA density, and PI‐RADS category.

Results

Of the 2597 men included, the overall GG 1, GG ≥2, and GG ≥3 prevalence was 8% (210/2597), 27% (697/2597), and 15% (396/2597), respectively. Biopsy was avoided in 57% (1488/2597) of men. After IPW, the GG 1, GG ≥2 and GG ≥3 detection rates after TR‐ and TP‐MRDB were comparable at 24%, 57%, and 32%; and 18%, 64%, and 38%, respectively; with mean differences of −5.7% (95% confidence interval [CI] −13% to 1.4%), 6.1% (95% CI −2.1% to 14%), and 5.7% (95% CI −1.7% to 13%). Complications were similar in TR‐MRDB (0.50%) and TP‐MRDB with RB (0.62%; mean difference 0.11%, 95% CI −0.87% to 1.1%).

Conclusion

This high‐volume, two‐centre study shows pre‐biopsy MRI as a decision tool is implementable in daily clinical practice. Compared to recent trials, a substantially higher biopsy avoidance rate was achieved without compromising GG ≥2/GG ≥3 detection and coinciding with lower over detection rates of GG 1 cancer. Prostate cancer detection and complication rates were comparable for TR‐ and TP‐MRDB.

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.

Fast 3-T MR-guided transrectal prostate biopsy using an in-room tablet device for needle guide alignment: a feasibility study

OBJECTIVES

To assess the feasibility of adding a tablet device inside the scanner room to assist needle-guide alignment during magnetic resonance (MR)-guided transrectal prostate biopsy.

METHODS

Twenty patients with one cancer-suspicious region (CSR) with PI-RADS score ≥ 4 on diagnostic multiparametric MRI were prospectively enrolled. Two orthogonal scan planes of an MR fluoroscopy sequence (~3 images/s) were aligned to the CSR and needle-guide pivoting point. Targeting was achieved by manipulating the needle-guide under MR fluoroscopy feedback on the in-room tablet device. Technical feasibility and targeting success were assessed. Complications and biopsy procedure times were also recorded.

RESULTS

Needle-guide alignment with the in-room tablet device was technically successful in all patients and allowed sampling after a single alignment step in 19/20 (95%) CSRs (median size 14 mm, range: 4-45). Biopsy cores contained cancer in 18/20 patients. There were no per-procedural or post-biopsy complications. Using the tablet device, the mean time to first biopsy was 5.8 ± 1.0 min and the mean total procedure time was 23.7 ± 4.1 min.

CONCLUSIONS

Use of an in-room tablet device to assist needle-guide alignment was feasible and safe during MR-guided transrectal prostate biopsy. Initial experience indicates potential for procedure time reduction.

KEY POINTS

• Performing MR-guided prostate biopsy using an in-room tablet device is feasible. • CSRs could be sampled after a single alignment step in 19/20 patients. • The mean procedure time for biopsy with the tablet device was 23.7 min.

Value of Serial Multiparametric Magnetic Resonance Imaging and Magnetic Resonance Imaging-guided Biopsies in Men with Low-risk Prostate Cancer on Active Surveillance After 1 Yr Follow-up

BACKGROUND

Active surveillance (AS) aims to reduce overtreatment of low-risk prostate cancer (PC). Incorporating multiparametric magnetic resonance imaging (mp-MRI) and MR-guided biopsy (MRGB) in an AS protocol might contribute to more accurate identification of AS candidates.

OBJECTIVE

To evaluate the value of 3T mp-MRI and MRGB in PC patients on AS at inclusion and after 12-mo follow-up.

DESIGN, SETTING, AND PARTICIPANTS

Patients with cT1c-cT2 PC, prostate-specific antigen (PSA) ≤10ng/ml, PSA density <0.2ng/ml/ml, and Gleason scores (GSs) of ≤6 and ≤2 positive biopsy cores were included and followed in an AS protocol including mp-MRI and MRGB. The mp-MRI and MRGB were performed at <3 and 12 mo after diagnosis. Reclassification was defined as GS >6, >2 positive cores at repeat transrectal ultrasound-guided biopsy (TRUSGB), presence of PC in >3 separate cancer foci upon both MRGB and TRUSGB, or cT3 tumor on mp-MRI.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Reclassification rates, treatment after discontinuation, and outcome on radical prostatectomy after discontinuing AS were reported. Uni- and multivariate analyses were performed to identify predictors of reclassification after 1 yr.

RESULTS AND LIMITATIONS

From 2009 to 2013, a total of 111 of 158 patients were consecutively and prospectively included. Around initial diagnosis, 36 patients were excluded from the study protocol; mp-MRI+MRGB reclassified 25/111 (23%) patients, and 11 patients were excluded at own request. Reasons for reclassification were as follows: GS upgrade (15/25, 60%); cT3 disease (3/25, 12%); suspicion of bone metastases (1/25, 4%); and multifocal disease upon MRGB (6/25, 24%). Repeat examinations after 1 yr showed reclassification in 33/75 patients (44%). Reasons were the following: GS upgrade upon TRUSGB (9/33, 27%); volume progression upon TRUSGB (9/33, 27%); cT3 disease upon mp-MRI (1/33, 3%); GS upgrade upon MRGB (1/33, 3%); volume progression upon MRGB (1/33, 3%); multifocal disease upon MRGB (2/33, 6%); and upgrade or upstage upon both TRUSGB and MRGB (10/33, 30%). On logistic regression analysis, the presence of cancer at initial mp-MRI and MRGB examinations was the only predictor of reclassification after 1 yr (odds ratio 5.9, 95% confidence interval 2.0-17.6).

CONCLUSIONS

Although mp-MRI and MRGB are of additional value in the evaluation of PC patients on AS, the value of mp-MRI after 1 yr was limited. As a considerable percentage of GS ≥7 PC after 1 yr was detected only by TRUSGB, TRUSGB cannot be omitted yet.

PATIENT SUMMARY

More aggressive tumors are detected if low-risk prostate cancer patients are additionally monitored by magnetic resonance imaging. However, some high-grade tumors are detected only by transrectal ultrasound-guided biopsy.

Prostate magnetic resonance imaging for brachytherapists: Diagnosis, imaging pitfalls, and post-therapy assessment

Optimal integration of multiparametric MRI (mp MRI) into prostate brachytherapy practice necessitates an understanding of imaging findings pertinent to prostate cancer detection and staging. This review will summarize prostate cancer imaging findings and tumor staging on mp MRI, including an overview of the Prostate Imaging Reporting and Data System (PIRADS)-structured reporting schema, mp MRI findings observed in the post-therapy setting including cases of post-treatment recurrence, and MRI concepts integral to successful salvage brachytherapy.

Comparing Three Different Techniques for Magnetic Resonance Imaging-targeted Prostate Biopsies: A Systematic Review of In-bore versus Magnetic Resonance Imaging-transrectal Ultrasound fusion versus Cognitive Registration. Is There a Preferred Technique?

CONTEXT

The introduction of magnetic resonance imaging-guided biopsies (MRI-GB) has changed the paradigm concerning prostate biopsies. Three techniques of MRI-GB are available: (1) in-bore MRI target biopsy (MRI-TB), (2) MRI-transrectal ultrasound fusion (FUS-TB), and (3) cognitive registration (COG-TB).

OBJECTIVE

To evaluate whether MRI-GB has increased detection rates of (clinically significant) prostate cancer (PCa) compared with transrectal ultrasound-guided biopsy (TRUS-GB) in patients at risk for PCa, and which technique of MRI-GB has the highest detection rate of (clinically significant) PCa.

EVIDENCE ACQUISITION

We performed a literature search in PubMed, Embase, and CENTRAL databases. Studies were evaluated using the Quality Assessment of Diagnostic Accuracy Studies-2 checklist and START recommendations. The initial search identified 2562 studies and 43 were included in the meta-analysis.

EVIDENCE SYNTHESIS

Among the included studies 11 used MRI-TB, 17 used FUS-TB, 11 used COG-TB, and four used a combination of techniques. In 34 studies concurrent TRUS-GB was performed. There was no significant difference between MRI-GB (all techniques combined) and TRUS-GB for overall PCa detection (relative risk [RR] 0.97 [0.90-1.07]). MRI-GB had higher detection rates of clinically significant PCa (csPCa) compared with TRUS-GB (RR 1.16 [1.02-1.32]), and a lower yield of insignificant PCa (RR 0.47 [0.35-0.63]). There was a significant advantage (p = 0.02) of MRI-TB compared with COG-TB for overall PCa detection. For overall PCa detection there was no significant advantage of MRI-TB compared with FUS-TB (p=0.13), and neither for FUS-TB compared with COG-TB (p=0.11). For csPCa detection there was no significant advantage of any one technique of MRI-GB. The impact of lesion characteristics such as size and localisation could not be assessed.

CONCLUSIONS

MRI-GB had similar overall PCa detection rates compared with TRUS-GB, increased rates of csPCa, and decreased rates of insignificant PCa. MRI-TB has a superior overall PCa detection compared with COG-TB. FUS-TB and MRI-TB appear to have similar detection rates. Head-to-head comparisons of MRI-GB techniques are limited and are needed to confirm our findings.

PATIENT SUMMARY

Our review shows that magnetic resonance imaging-guided biopsy detects more clinically significant prostate cancer (PCa) and less insignificant PCa compared with systematic biopsy in men at risk for PCa.

Open-Source Platform for Prostate Motion Tracking During in-Bore Targeted MRI-Guided Biopsy

Accurate sampling of cancer suspicious locations is critical in targeted prostate biopsy, but can be complicated by the motion of the prostate. We present an open-source software for intra-procedural tracking of the prostate and biopsy targets using deformable image registration. The software is implemented in 3D Slicer and is intended for clinical users. We evaluated accuracy, computation time and sensitivity to initialization, and compared implementations that use different versions of the Insight Segmentation Toolkit (ITK). Our retrospective evaluation used data from 25 in-bore MRI-guided prostate biopsy cases (343 registrations total). Prostate Dice similarity coefficient improved on average by 0.17 (p < 0.0001, range 0.02-0.48). Registration was not sensitive to operator variability. Computation time decreased significantly for the implementation using the latest version of ITK. In conclusion, we presented a fully functional open-source tool that is ready for prospective evaluation during clinical MRI-guided prostate biopsy interventions.

Pitfalls in Interpreting mp-MRI of the Prostate: A Pictorial Review with Pathologic Correlation

Objectives

The purpose of this pictorial review is to present a wide spectrum of prostate multiparametric MRI (mp-MRI) pitfalls that may occur in clinical practice, with radiological and pathological correlation.

Methods

All examinations were performed according to ESUR Guidelines protocols.

Results and Conclusion

mp-MRI imaging of the prostate often leads to interpreting doubts and misdiagnosis due to the many interpretative pitfalls that a tissue, whether healthy or treated, may cause. These “false-positive” findings may occur in each stage of the disease history, from the primary diagnosis and staging, to the post-treatment stage, and whether they are caused by the tissue itself or are iatrogenic, their recognition is critical for proper treatment and management. Knowledge of these known pitfalls and their interpretation in the anatomical-radiological context can help radiologists avoid misdiagnosis and consequently mistreatment.

Main Messages

• Some physiological changes in the peripheral and central zone may simulate prostate cancer.

• Technical errors, such as mispositioned endorectal coils, can affect the mp-MRI interpretation.

• Physiological changes post-treatment can simulate recurrence

Pitfalls and Limitations of Diffusion-Weighted Magnetic Resonance Imaging in the Diagnosis of Urinary Bladder Cancer

Adequately selecting a therapeutic approach for bladder cancer depends on accurate grading and staging. Substantial inaccuracy of clinical staging with bimanual examination, cystoscopy, and transurethral resection of bladder tumor has facilitated the increasing utility of magnetic resonance imaging to evaluate bladder cancer. Diffusion-weighted imaging (DWI) is a noninvasive functional magnetic resonance imaging technique. The high tissue contrast between cancers and surrounding tissues on DWI is derived from the difference of water molecules motion. DWI is potentially a useful tool for the detection, characterization, and staging of bladder cancers; it can also monitor posttreatment response and provide information on predicting tumor biophysical behaviors. Despite advancements in DWI techniques and the use of quantitative analysis to evaluate the apparent diffusion coefficient values, there are some inherent limitations in DWI interpretation related to relatively poor spatial resolution, lack of cancer specificity, and lack of standardized image acquisition protocols and data analysis procedures that restrict the application of DWI and reproducibility of apparent diffusion coefficient values. In addition, inadequate bladder distension, artifacts, thinness of bladder wall, cancerous mimickers of normal bladder wall and benign lesions, and variations in the manifestation of bladder cancer may interfere with diagnosis and monitoring of treatment. Recognition of these pitfalls and limitations can minimize their impact on image interpretation, and carefully applying the analyzed results and combining with pathologic grading and staging to clinical practice can contribute to the selection of an adequate treatment method to improve patient care.

Magnetic resonance sentinel lymph node imaging of the prostate with gadofosveset trisodium-albumin: preliminary results in a canine model

RATIONALE AND OBJECTIVES

To determine if intraprostatic injection of gadofosveset trisodium mixed with human serum albumin (HSA) can identify sentinel lymph nodes (LNs) draining the prostate on magnetic resonance imaging (MRI) in a canine model.

MATERIALS AND METHODS

Three male canines weighing between 25.7 and 41.3 kg were anesthetized, placed in a 3-T MRI, and a needle was placed transrectally into one side of the prostate using a commercially available intrarectal needle guide. Gadofosveset trisodium premixed with 10% HSA was then administered at doses ranging from 0.1 to 2.5 mL. T1W MRI was performed immediately after injection, and two readers evaluated images for visualization of LNs draining the prostate.

RESULTS

Intraprostatic injection of 0.2 mL gadofosveset trisodium premixed with HSA identified the draining periprostatic LNs in all cases. Delayed images demonstrated upper echelon nodes in the pelvis and the abdomen. Higher volume injections resulted in excessive periprostatic extravasation, whereas lower volume injections resulted in suboptimal visualization of LNs.

CONCLUSIONS

We demonstrate that gadofosveset trisodium (premixed with 10% HSA) injected intraprostatically at 0.2 mL visualized LNs draining the prostate. This approach can be readily adapted for clinical applications such as sentinel LN imaging in prostate cancer patients before surgery.

MR imaging-guided prostate biopsy techniques

Nearly all prostate biopsies are performed via the transrectal ultrasound (TRUS)-guided technique which suffers from its inability to accurately visualize and target suspicious lesions. Advances in prostate MR imaging now allow for the detection of suspicious regions of the prostate gland, opening the door for lesion-directed biopsy techniques. The ability to obtain a definitive histologic grade has become increasingly important due to the rise of active surveillance as a popular method to approach low-grade cancer. Biopsies obtained with MR guidance or MR imaging/transrectal ultrasound fusion can accurately identify and characterize cancers and thus appropriately stratify patients for specific therapies.

Transperineal in-bore 3-T MR imaging-guided prostate biopsy: a prospective clinical observational study

PURPOSE

To determine the detection rate, clinical relevance, Gleason grade, and location of prostate cancer ( PCa prostate cancer ) diagnosed with and the safety of an in-bore transperineal 3-T magnetic resonance (MR) imaging-guided prostate biopsy in a clinically heterogeneous patient population.

MATERIALS AND METHODS

This prospective retrospectively analyzed study was HIPAA compliant and institutional review board approved, and informed consent was obtained. Eighty-seven men (mean age, 66.2 years ± 6.9) underwent multiparametric endorectal prostate MR imaging at 3 T and transperineal MR imaging-guided biopsy. Three subgroups of patients with at least one lesion suspicious for cancer were included: men with no prior PCa prostate cancer diagnosis, men with PCa prostate cancer who were undergoing active surveillance, and men with treated PCa prostate cancer and suspected recurrence. Exclusion criteria were prior prostatectomy and/or contraindication to 3-T MR imaging. The transperineal MR imaging-guided biopsy was performed in a 70-cm wide-bore 3-T device. Overall patient biopsy outcomes, cancer detection rates, Gleason grade, and location for each subgroup were evaluated and statistically compared by using χ(2) and one-way analysis of variance followed by Tukey honestly significant difference post hoc comparisons.

RESULTS

Ninety biopsy procedures were performed with no serious adverse events, with a mean of 3.7 targets sampled per gland. Cancer was detected in 51 (56.7%) men: 48.1% (25 of 52) with no prior PCa prostate cancer , 61.5% (eight of 13) under active surveillance, and 72.0% (18 of 25) in whom recurrence was suspected. Gleason pattern 4 or higher was diagnosed in 78.1% (25 of 32) in the no prior PCa prostate cancer and active surveillance groups. Gleason scores were not assigned in the suspected recurrence group. MR targets located in the anterior prostate had the highest cancer yield (40 of 64, 62.5%) compared with those for the other parts of the prostate (P < .001).

CONCLUSION

In-bore 3-T transperineal MR imaging-guided biopsy, with a mean of 3.7 targets per gland, allowed detection of many clinically relevant cancers, many of which were located anteriorly.

Diffusion-weighted magnetic resonance imaging in the prostate transition zone: histopathological validation using magnetic resonance-guided biopsy specimens

OBJECTIVES

The objective of this study was to evaluate the apparent diffusion coefficient (ADC) of diffusion-weighted magnetic resonance (MR) imaging for the differentiation of transition zone cancer from non-cancerous transition zone with and without prostatitis and for the differentiation of transition zone cancer Gleason grade (GG) using MR-guided biopsy specimens as a reference standard.

MATERIALS AND METHODS

From consecutive MR-guided prostate biopsies (2008-2012) in our referral center, we retrospectively included patients from whom diffusion-weighted MR imaging ADC values were acquired during MR-guided biopsy and whose biopsy cores had a (cancer) core length 10 mm or greater and originated from the transition zone. Two radiologists, who were blinded to the ADC data, annotated regions of interest on biopsy sampling locations of MR-guided biopsy confirmation scans in consensus. Median ADC (mADC) of the regions of interest was related to histopathology outcome in MR-guided biopsy core specimens. Mixed model analysis was used to evaluate mADC differences between 7 histopathology categories predefined as MR-guided biopsy core specimens with primary and secondary GG 4-5 (I), primary GG 4-5 secondary GG 2-3 (II), primary GG 2-3 secondary GG 4-5 (III) and primary and secondary GG 2-3 cancer (IV), and noncancerous tissue without (V) or with degree 1 (VI) or degree 2 prostatitis (VII). Diagnostic accuracy was evaluated using areas under the receiver operating characteristic (AUC) curve.

RESULTS

Fifty-two patients with 87 cancer-containing biopsy cores and 53 patients with 101 non-cancerous biopsy cores were included. Significant mean mADC differences were present between cancers (mean mADC, 0.77-0.86 × 10 mm/s) and noncancerous transition zone without (1.12 × 10 mm/s) and with degree 1 to 2 prostatitis (1.05-1.12 × 10 mm/s; P < 0.0001-0.05). Exceptions were mixed primary and secondary GG cancers versus a degree 2 of prostatitis (P = 0.06-0.09). No significant differences were found between subcategories of primary and secondary GG cancers (P = 0.17-0.91) and between a degree 1 and 2 prostatitis and non-cancerous transition zone without prostatitis (P = 0.48-0.94).The mADC had an AUC of 0.84 to differentiate cancer versus non-cancerous transition zone. AUCs of 0.84 and 0.56 were found for mADC to differentiate prostatitis from cancer and from non-cancerous transition zone. The mADC had an AUC of 0.62 to differentiate a primary GG 4 versus GG 3 cancer.

CONCLUSIONS

The mADC values can differentiate transition zone cancer from non-cancerous transition zone and from a degree 1, and from most cases of a degree 2 prostatitis. However, because of substantial overlap, mADC has a moderate accuracy to differentiate between different primary and secondary GG subcategories and cannot be used to differentiate non-cancerous transition zone from degrees 1 to 2 of prostatitis. Diffusion-weighted imaging ADC may therefore contribute in the detection of transition zone cancers; however, as a single functional MR imaging technique, diffusion-weighted imaging has a moderate diagnostic accuracy in separating higher from lower GG transition zone cancers and in differentiating prostatitis from non-cancerous transition zone.

Configurable automatic detection and registration of fiducial frames for device-to-image registration in MRI-guided prostate interventions

We propose a novel automatic fiducial frame detection and registration method for device-to-image registration in MRI-guided prostate interventions. The proposed method does not require any manual selection of markers, and can be applied to a variety of fiducial frames, which consist of multiple cylindrical MR-visible markers placed in different orientations. The key idea is that automatic extraction of linear features using a line filter is more robust than that of bright spots by thresholding; by applying a line set registration algorithm to the detected markers, the frame can be registered to the MRI. The method was capable of registering the fiducial frame to the MRI with an accuracy of 1.00 +/- 0.73 mm and 1.41 +/- 1.06 degrees in a phantom study, and was sufficiently robust to detect the fiducial frame in 98% of images acquired in clinical cases despite the existence of anatomical structures in the field of view.

1.5-T magnetic resonance-guided transgluteal biopsies of the prostate in patients with clinically suspected prostate cancer: technique and feasibility

OBJECTIVES

The aim of this study was to examine the feasibility and safety of magnetic resonance-guided prostate biopsy (MRGBx) with a transgluteal approach in patients with cancer suspicious prostatic lesions.

MATERIALS AND METHODS

This study was approved by the ethical committee. A total of 25 men with clinically suspected prostate cancer with increased prostate-specific antigen levels and at least 1 previous negative transrectal ultrasound-guided prostatic biopsy (TRUSBx) underwent diagnostic magnetic resonance (MR) imaging of the prostate. Cancer suspicious regions (CSR) were identified, and MRGBx with a transgluteal approach in a large closed-bore 1.5-T MR system was manually performed in coaxial technique, using transversal fat-suppressed T2-weighted true fast imaging with steady-state free precession sequences. Success rate, biopsy findings, side effects, procedure time, number of acquisitions for the repositioning of the needle guide, and length of the biopsy channel were documented. Follow-up was performed 24 months after the procedure.

RESULTS

In diagnostic MR imaging of the prostate, a total of 40 CSRs were detected in 25 patients. All MRGBx procedures were technically successful and all CSRs were biopsied. The mean number of core biopsies per CSR was 3.3 ± 1.5 (range, 1-7). Histopathological analysis revealed adenocarcinoma in 35% (14/40), acute or chronic prostatitis in 30% (12/40), adenofibromyomatous changes in 22.5% (9/40), and no identifiable pathology in 17.5% (7/40) of CSRs, with a pathological overlap for chronic prostatitis and adenofibromyomatous changes in 1 patient with biopsies in 2 CSRs. No missed prostate cancer after MR-guided biopsy in clinical follow-up was detected. Mean procedure time was 31 ± 7 minutes (range, 21-46 minutes). Side effects were hematuria (n = 7), hematospermia (n = 3), combined hematuria/hematospermia (n = 2), and infection (n=1).

CONCLUSION

Magnetic resonance-guided prostate biopsy of the prostate gland with a transgluteal approach is feasible, safe, and a promising technique for histological clarification of cancer suspicious lesions in patients with increased prostate-specific antigen levels after negative TRUSBx. Magnetic resonance-guided prostate biopsy offers a reasonable alternative to repeated TRUSBx for histological clarification of prostate cancer.

Prostate cancer detection and diagnosis: the role of MR and its comparison with other diagnostic modalities--a radiologist's perspective

It is now universally recognized that many prostate cancers are over-diagnosed and over-treated. The European Randomized Study of Screening for Prostate Cancer from 2009 evidenced that, to save one man from death from prostate cancer, over 1400 men need to be screened, and 48 need to undergo treatment. The detection of prostate cancer is traditionally based on digital rectal examination (DRE) and the measurement of serum prostate-specific antigen (PSA), followed by ultrasound-guided biopsy. The primary role of imaging for the detection and diagnosis of prostate cancer has been transrectal ultrasound (TRUS) guidance during biopsy. Traditionally, MRI has been used primarily for the staging of disease in men with biopsy-proven cancer. It has a well-established role in the detection of T3 disease, planning of radiation therapy, especially three-dimensional conformal or intensity-modulated external beam radiation therapy, and planning and guiding of interstitial seed implant or brachytherapy. New advances have now established that prostate MRI can accurately characterize focal lesions within the gland, an ability that has led to new opportunities for improved cancer detection and guidance for biopsy. Two new approaches to prostate biopsy are under investigation. Both use pre-biopsy MRI to define potential targets for sampling, and the biopsy is performed either with direct real-time MR guidance (in-bore) or MR fusion/registration with TRUS images (out-of-bore). In-bore and out-of-bore MRI-guided prostate biopsies have the advantage of using the MR target definition for the accurate localization and sampling of targets or suspicious lesions. The out-of-bore method uses combined MRI/TRUS with fusion software that provides target localization and increases the sampling accuracy of TRUS-guided biopsies by integrating prostate MRI information with TRUS. Newer parameters for each imaging modality, such as sonoelastography or shear wave elastography, contrast-enhanced ultrasound and MRI elastography, show promise to further enrich datasets.

3-T in-bore MR-guided prostate biopsy based on a scoring system for target lesions characterization

BACKGROUND

To estimate potential malignant lesions within the prostate gland, the usage of a scoring system has recently been proposed by a European consensus meeting.

PURPOSE

To prospectively investigate a scoring system for functional prostate magnetic resonance imaging (MRI) using in-bore MR-guided prostate biopsy at 3-T.

MATERIAL AND METHODS

Prostate MRI examinations of 59 patients (between February 2011 and May 2012) with no known prostate cancer, elevated prostate specific antigen (PSA) level, and unsuspicious digital rectal examination were included in the study. In each patient up to three lesions were defined and scored using a 5-point scoring system for each MR sequence (T2-weighted images, diffusion-weighted imaging, dynamic contrast-enhanced imaging). Following MRI-guided in-bore biopsy these lesions were correlated to the histopathological findings.

RESULTS

A total number of 144 lesions were defined in 59 patients. In 28 patients (51 lesions) MR-guided in-bore biopsy was positive for tumor (Gleason grade 6 or higher). A cut-off limit of 10 or more points in summation of the individual scores of all three sequences was used, leading to a 90% sensitivity, 63% specificity, 58% positive predictive value, and 92% negative predictive value.

CONCLUSION

A simple 5-point scoring system of functional prostate MRI achieves excellent sensitivity and moderate specificity for directing 3-T-guided prostate biopsy relative to the histopathological findings.

A prospective, blinded comparison of magnetic resonance (MR) imaging-ultrasound fusion and visual estimation in the performance of MR-targeted prostate biopsy: the PROFUS trial

BACKGROUND

Increasing evidence supports the use of magnetic resonance (MR)-targeted prostate biopsy. The optimal method for such biopsy remains undefined, however.

OBJECTIVE

To prospectively compare targeted biopsy outcomes between MR imaging (MRI)-ultrasound fusion and visual targeting.

DESIGN, SETTING, AND PARTICIPANTS

From June 2012 to March 2013, prospective targeted biopsy was performed in 125 consecutive men with suspicious regions identified on prebiopsy 3-T MRI consisting of T2-weighted, diffusion-weighted, and dynamic-contrast enhanced sequences.

INTERVENTION

Two MRI-ultrasound fusion targeted cores per target were performed by one operator using the ei-Nav|Artemis system. Targets were then blinded, and a second operator took two visually targeted cores and a 12-core biopsy.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Biopsy information yield was compared between targeting techniques and to 12-core biopsy. Results were analyzed using the McNemar test. Multivariate analysis was performed using binomial logistic regression.

RESULTS AND LIMITATIONS

Among 172 targets, fusion biopsy detected 55 (32.0%) cancers and 35 (20.3%) Gleason sum ≥7 cancers compared with 46 (26.7%) and 26 (15.1%), respectively, using visual targeting (p=0.1374, p=0.0523). Fusion biopsy provided informative nonbenign histology in 77 targets compared with 60 by visual (p=0.0104). Targeted biopsy detected 75.0% of all clinically significant cancers and 86.4% of Gleason sum ≥7 cancers detected on standard biopsy. On multivariate analysis, fusion performed best among smaller targets. The study is limited by lack of comparison with whole-gland specimens and sample size. Furthermore, cancer detection on visual targeting is likely higher than in community settings, where experience with this technique may be limited.

CONCLUSIONS

Fusion biopsy was more often histologically informative than visual targeting but did not increase cancer detection. A trend toward increased detection with fusion biopsy was observed across all study subsets, suggesting a need for a larger study size. Fusion targeting improved accuracy for smaller lesions. Its use may reduce the learning curve necessary for visual targeting and improve community adoption of MR-targeted biopsy.

MRI-targeted prostate biopsy: a review of technique and results

Multiparametric magnetic resonance imaging (mpMRI) is of interest for the diagnosis of clinically significant prostate cancer and mpMRI-targeted biopsies are being used increasingly in clinical practice. Target acquisition is performed using a range of magnet strengths and varying combinations of anatomical and functional sequences. Target identification at the time of biopsy can be carried out in the MRI scanner (in-bore biopsy) or, more commonly, the MRI-target is biopsied under ultrasonographic guidance. Many groups use cognitive or visual registration, whereby the biopsy target is identified on MRI and ultrasonography is subsequently used to direct the needle to the same location. Other groups use registration software to show prebiopsy MRI data on real-time ultrasonography. The reporting of histological results in MRI-targeted biopsy studies varies greatly. The most useful reports compare the detection of clinically significant disease in standard cores versus mpMRI-targeted cores in the same cohort of men, as recommended by the STAndards of Reporting for MRI-Targeted biopsy studies (START) consensus panel. Further evidence is needed before an mpMRI-targeted strategy can be recommended as the standard intervention for men at risk of prostate cancer.

Value of PCA3 to predict biopsy outcome and its potential role in selecting patients for multiparametric MRI

PCA3 (prostate cancer gene 3) and multiparametric 3 tesla MRI are new promising diagnostic tools in the detection of PCa. Our aim was to study the clinical value of the Progensa PCA3-test: its predictive value for biopsy outcome, Gleason score and MRI outcome. We evaluated, retrospectively, 591 patients who underwent a Progensa PCA3-test at the Radboud University Nijmegen Medical Centre between May 2006 and December 2009. Prostate biopsies were performed in 290 patients; a multiparametric 3 tesla MRI of the prostate was performed in 163/591 patients. The PCA3-score was correlated to biopsy results and MRI outcome. The results show that PCA3 was highly predictive for biopsy outcome (p < 0.001); there was no correlation with the Gleason score upon biopsy (p = 0.194). The PCA3-score of patients with a suspicious region for PCa on MRI was significantly higher (p < 0.001) than in patients with no suspicious region on MRI (52 vs. 21). In conclusion, PCA3 is a valuable diagnostic biomarker for PCa; it did not correlate with the Gleason score. Furthermore, multiparametric MRI outcome was significantly correlated with the PCA3-score. Thus, PCA3 could be used to select patients that require MRI. However, in patients with a negative PCA3 and high clinical suspicion of PCa, a multiparametric MRI should also be done.

Prostate cancer magnetic resonance imaging (MRI): multidisciplinary standpoint

Prostate cancer is the most common cancer diagnosed in men and a leading cause of death. Accurate assessment is a prerequisite for optimal clinical management and therapy selection of prostate cancer. There are several parameters and nomograms to differentiate between patients with clinically insignificant disease and patients in need of treatment. Magnetic resonance imaging (MRI) is a technique which provides more detailed anatomical images due to high spatial resolution, superior contrast resolution, and multiplanar capability. State-of-the-art MRI techniques, such as diffusion weighted imaging (DWI), MR spectroscopic imaging (MRSI), dynamic contrast enhanced MRI (DCE-MRI), improve interpretation of prostate cancer imaging. In this article, we review the major role of MRI in the advanced management of prostate cancer to noninvasively improve tumor staging, biologic potential, treatment planning, therapy response, local recurrence, and to guide target biopsy for clinical suspected cancer with previous negative biopsy. Finally, future challenges and opportunities in prostate cancer management in the area of functional MRI are discussed as well.

Multiparametric magnetic resonance imaging of prostate cancer

In India, prostate cancer has an incidence rate of 3.9 per 100,000 men and is responsible for 9% of cancer-related mortality. It is the only malignancy that is diagnosed with an apparently blind technique, i.e., transrectal sextant biopsy. With increasing numbers of high-Tesla magnetic resonance imaging (MRI) equipment being installed in India, the radiologist needs to be cognizant about endorectal MRI and multiparametric imaging for prostate cancer. In this review article, we aim to highlight the utility of multiparamteric MRI in prostate cancer. It plays a crucial role, mainly in initial staging, restaging, and post-treatment follow-up.

Microvascularity in transition zone prostate tumors resembles normal prostatic tissue

BACKGROUND

The objective of this study was comparison of characteristics of the microvasculature in transition zone tumor (TZT) and benign nodular hyperplasia (BPH) with normal prostatic transition zone (NTZ), applying accurate and objective quantification based on digital image analysis. Results of this study may increase understanding of prostate dynamic contrast enhanced (DCE) MRI analysis.

METHODS

Radical prostatectomy specimens of 28 patients containing TZT ranging from pT2-pT4 were used. In 11 patients a concomitant peripheral zone tumor (PZT) was present. Microvessels were visualized by CD31 immunohistochemistry. Specimens were scanned using a computer-controlled microscope with automatic recognition of microvessels. Pseudocolor maps were produced displaying microvessel density, perimeter, and area of an entire prostate transection. Mean, 75th percentile (p75) and coefficient of variation (CV) were calculated automatically in manually indicated areas of the tumor and corresponding contralateral normal tissue, and BPH.

RESULTS

Large variability was seen in TZT microvascular parameters, indicating presence of patients having both hypo and hypervascularized tumors compared to NTZ. In contrast, areas of BPH showed a more consistent increase in vascular parameters, with decreased CV. Analysis of PZT confirmed results of our previous study, with mean and p75 of all vascular parameters being significantly increased and a decrease in CV. No correlation was found for clinicopathological parameters and microvascular parameters.

CONCLUSION

Microvasculature of transition zone tumor showed increased heterogeneity compared to BPH and peripheral zone tumors, possibly explaining the difficulty of TZT detection on DCE-MRI.

MRI-guided core biopsy of the prostate in the supine position--introduction of a simplified technique using large-bore magnet systems

OBJECTIVES

To introduce a simplified technique for MRI-guided core biopsies (MRGB) of the prostate in the supine position using large-bore magnet systems.

METHODS

Fifty men with a history of negative transrectal ultrasound-guided biopsies underwent MRGB in either a 1.5-T (13/50) or 3.0-T (37/50) wide-bore MRI unit. MRGBs were conducted with the patients in a supine position using a dedicated MR-compatible biopsy device.

RESULTS

We developed a dedicated positioning device for the supine position. Using this device, the biopsies were performed successfully in all patients. Apart from minor rectal bleeding, only one patient developed a major side effect (urosepsis). Histology revealed prostate cancer in 25/50 (50 %) patients.

CONCLUSIONS

The new technique appears feasible. Its major advantage is the more comfortable and patient-friendly supine position during the biopsy without the need to modify the MRI system's patient table.

KEY POINTS

• A novel positioning device for MRI-guided prostate biopsies has been developed. • Biopsies can be performed in the patient-friendly supine position. • The positioning device can be utilised without modifying the MRI's patient table.

[Standardised scoring of a multi-parametric 3-T MRI for a targeted MRI-guided prostate biopsy]

BACKGROUND

The use of multi-parametric MRI and MRI-guided biopsy for the detection of prostate cancer is rapidly increasing. This is a pilot study to evaluate the consensus-based international MRI scoring system as decision criterion for targeted MRI-guided prostate biopsy.

MATERIAL AND METHODS

After a multi-parametric 3-T MRI (T2-weighted imaging, diffusion-weighted imaging, and dynamic contrast-enhanced MRI) in 23 consecutive patients a total of 47 lesions were scored according to a 5-point scale for each MRI sequence. A total score of ≥ 10 points was considered to be suspicious for prostate cancer. All 47 lesions were histologically assessed after MRI-guided biopsy.

RESULTS

At the cut-off score of 10 points, sensitivity, specificity, negative predictive value and positive predictive value of multi-parametric MRI were 94.1, 43.3, 92.9 and 48.5%, respectively.

CONCLUSIONS

A standardised scoring of lesions on multi-parametric MRI is feasible. The cut-off value leads to excellent values for sensitivity and negative predictive value. The values for specificity and positive predictive value are modest. Lesions with a total score <10 points are very unlikely to be malignant.

High-risk prostate cancer: value of multi-modality 3T MRI-guided biopsies after previous negative biopsies

Transrectal ultrasound-guided biopsy is the gold standard for prostate cancer detection. The latter detection rates of random systematic TRUS-guided biopsy do not exceed 44%. As a consequence other biopsy methods have been explored. One of these methods is MR-guided biopsy (MRGB), which revealed detection rates of 38–59% after previous negative TRUSGB sessions. For this reason MRGB will probably become more and more applied in daily practice.

Image registration for targeted MRI-guided transperineal prostate biopsy

PURPOSE

To develop and evaluate image registration methodology for automated re-identification of tumor-suspicious foci from preprocedural MR exams during MR-guided transperineal prostate core biopsy.

MATERIALS AND METHODS

A hierarchical approach for automated registration between planning and intra-procedural T2-weighted prostate MRI was developed and evaluated on the images acquired during 10 consecutive MR-guided biopsies. Registration accuracy was quantified at image-based landmarks and by evaluating spatial overlap for the manually segmented prostate and sub-structures. Registration reliability was evaluated by simulating initial mis-registration and analyzing the convergence behavior. Registration precision was characterized at the planned biopsy targets.

RESULTS

The total computation time was compatible with a clinical setting, being at most 2 min. Deformable registration led to a significant improvement in spatial overlap of the prostate and peripheral zone contours compared with both rigid and affine registration. Average in-slice landmark registration error was 1.3 ± 0.5 mm. Experiments simulating initial mis-registration resulted in an estimated average capture range of 6 mm and an average in-slice registration precision of ±0.3 mm.

CONCLUSION

Our registration approach requires minimum user interaction and is compatible with the time constraints of our interventional clinical workflow. The initial evaluation shows acceptable accuracy, reliability and consistency of the method.

Imaging-guided prostate biopsy: conventional and emerging techniques

Transrectal ultrasonography (US)-guided biopsy is the standard approach for histopathologic diagnosis of prostate cancer. However, this technique has multiple limitations owing to the operator's inability in most cases to directly visualize and target prostate lesions. Magnetic resonance (MR) imaging of the prostate overcomes many of these limitations by directly depicting areas of abnormality and allowing targeted biopsies. Accuracy in the detection of prostate cancer is improved by the combined use of standard T2-weighted MR imaging and advanced MR imaging techniques such as diffusion-weighted imaging, dynamic contrast-enhanced imaging, and MR spectroscopy. Suspicious-appearing regions of the prostate seen on MR images can be targeted at real-time transrectal US-guided biopsy to improve the diagnostic yield. MR imaging also can be performed for real-time guidance of transrectal prostate biopsy. Studies among patients who underwent at least one transrectal US-guided biopsy with a negative result before undergoing an MR imaging-guided biopsy showed improved detection rates with MR imaging-guided biopsy in comparison with the detection rates achieved with a repeat transrectal US-guided biopsy; however, MR imaging-guided biopsy is a more time-consuming procedure. A technique known as fused MR imaging- and transrectal US-guided biopsy, which relies on the coregistration of previously acquired MR images with real-time transrectal US images acquired during the procedure, shows promise but is limited by deformation of the prostate; this limitation is the subject of ongoing investigation. Another technique that is currently under investigation, MR imaging-guided prostate biopsy with robotic assistance, may one day help improve the accuracy of biopsy needle placement.

In-bore setup and software for 3T MRI-guided transperineal prostate biopsy

MRI-guided prostate biopsy in conventional closed-bore scanners requires transferring the patient outside the bore during needle insertion due to the constrained in-bore space, causing a safety hazard and limiting image feedback. To address this issue, we present our custom-made in-bore setup and software to support MRI-guided transperineal prostate biopsy in a wide-bore 3 T MRI scanner. The setup consists of a specially designed tabletop and a needle-guiding template with a Z-frame that gives a physician access to the perineum of the patient at the imaging position and allows the physician to perform MRI-guided transperineal biopsy without moving the patient out of the scanner. The software and Z-frame allow registration of the template, target planning and biopsy guidance. Initially, we performed phantom experiments to assess the accuracy of template registration and needle placement in a controlled environment. Subsequently, we embarked on our clinical trial (N = 10). The phantom experiments showed that the translational errors of the template registration along the right-left (RP) and anterior-posterior (AP) axes were 1.1 ± 0.8 and 1.4 ± 1.1 mm, respectively, while the rotational errors around the RL, AP and superior-inferior axes were (0.8 ± 1.0)°, (1.7 ± 1.6)° and (0.0 ± 0.0)°, respectively. The 2D root-mean-square (RMS) needle-placement error was 3 mm. The clinical biopsy procedures were safely carried out in all ten clinical cases with a needle-placement error of 5.4 mm (2D RMS). In conclusion, transperineal prostate biopsy in a wide-bore 3T scanner is feasible using our custom-made tabletop setup and software, which supports manual needle placement without moving the patient out of the magnet.

Image-guided prostate biopsy using magnetic resonance imaging-derived targets: a systematic review

CONTEXT

Technical improvements in prostate magnetic resonance imaging (MRI) have resulted in the use of MRI to target prostate biopsies.

OBJECTIVE

To systematically review the literature to compare the accuracy of MRI-targeted biopsy with standard transrectal biopsy in the detection of clinically significant prostate cancer.

EVIDENCE ACQUISITION

The PubMed, Embase, and Cochrane databases were searched from inception until December 3, 2011, using the search criteria 'prostate OR prostate cancer' AND 'magnetic resonance imaging OR MRI' AND 'biopsy OR target'. Four reviewers independently assessed 4222 records; 222 records required full review. Fifty unique records (corresponding to 16 discrete patient populations) directly compared an MRI-targeted with a standard transrectal approach.

EVIDENCE SYNTHESIS

Evidence synthesis was used to address specific questions. Where MRI was applied to all biopsy-naive men, 62% (374 of 599) had MRI abnormalities. When subjected to a targeted biopsy, 66% (248 of 374) had prostate cancer detected. Both targeted and standard biopsy detected clinically significant cancer in 43% (236 or 237 of 555, respectively). Missed clinically significant cancers occurred in 13 men using targeted biopsy and 12 using a standard approach. Targeted biopsy was more efficient. A third fewer men were biopsied overall. Those who had biopsy required a mean of 3.8 targeted cores compared with 12 standard cores. A targeted approach avoided the diagnosis of clinically insignificant cancer in 53 of 555 (10%) of the presenting population.

CONCLUSIONS

MRI-guided biopsy detects clinically significant prostate cancer in an equivalent number of men versus standard biopsy. This is achieved using fewer biopsies in fewer men, with a reduction in the diagnosis of clinically insignificant cancer. Variability in study methodology limits the strength of recommendation that can be made. There is a need for a robust multicentre trial of targeted biopsies.

Preclinical evaluation of an MRI-compatible pneumatic robot for angulated needle placement in transperineal prostate interventions

PURPOSE

To evaluate the targeting accuracy of a small profile MRI-compatible pneumatic robot for needle placement that can angulate a needle insertion path into a large accessible target volume.

METHODS

We extended our MRI-compatible pneumatic robot for needle placement to utilize its four degrees-of-freedom (4-DOF) mechanism with two parallel triangular structures and support transperineal prostate biopsies in a closed-bore magnetic resonance imaging (MRI) scanner. The robot is designed to guide a needle toward a lesion so that a radiologist can manually insert it in the bore. The robot is integrated with navigation software that allows an operator to plan angulated needle insertion by selecting a target and an entry point. The targeting error was evaluated while the angle between the needle insertion path and the static magnetic field was between -5.7° and 5.7° horizontally and between -5.7° and 4.3° vertically in the MRI scanner after sterilizing and draping the device.

RESULTS

The robot positioned the needle for angulated insertion as specified on the navigation software with overall targeting error of 0.8 ± 0.5mm along the horizontal axis and 0.8 ± 0.8mm along the vertical axis. The two-dimensional root-mean-square targeting error on the axial slices as containing the targets was 1.4mm.

CONCLUSIONS

Our preclinical evaluation demonstrated that the MRI-compatible pneumatic robot for needle placement with the capability to angulate the needle insertion path provides targeting accuracy feasible for clinical MRI-guided prostate interventions. The clinical feasibility has to be established in a clinical study.