Multiparametric MR imaging for detection of clinically significant prostate cancer: a validation cohort study with transperineal template prostate mapping as the reference standard

The impact of the relationship between lesion diameter and total core length on the detection rate of clinically significant prostate cancer for PI-RADS 3 lesions

BACKGROUND

The aim of our study was to determine the effect of total core length (TCL) for prostate imaging reporting and data system (PI-RADS) 3 lesions to facilitate clinically significant prostate cancer (csPCa) detection based on the lesion diameter.

MATERIALS AND METHODS

A total of 149 patients with at least 1 lesion with a PI-RADS 3 were evaluated retrospectively. The lesions with diameters of < 1 cm were categorized as small lesions and lesions of ≥ 1 cm were categorized as large lesions. The lengths of biopsy cores from PI-RADS 3 lesions were summed for each lesion separately, and TCL was calculated. The relationship between TCL and csPCa was analyzed separately for the small and large groups with multiple logistic regression analyses.

RESULTS

A total of 208 lesions were detected by multiparametric magnetic resonance imaging (MpMRI) in 149 males included in the study. The mean TCL was 44.68 mm (26-92) and the mean lesion diameter was 10.73 mm (4-27) in PIRADS 3 lesions. For small diameter lesions (< 1 cm), the odds of finding clinically insignificant prostate cancer (ciPCa) increase by 1.67 times if TCL increases by one unit. Hence, increasing TCL for small lesions only increases the odds of ciPCa detection. For large diameter lesions (≥ 1 cm), if TCL increases by one unit, the odds of finding ciPCa increase 1.13 times and the odds of finding csPCa increases1.16 times. Accordingly, large lesions are more likely to have both csPCa and ciPCa as TCL increases.

CONCLUSIONS

Our study showed that for PI-RADS 3 lesions, both more csPCa and more ciPCa were detected as TCL increased. However, in lesions with a size of < 1 cm, only ciPCa was detected more frequently as TCL increased. In conclusion, taking more and longer biopsy cores in PI-RADS 3 lesions below 1 cm does not contribute to the detection of csPCa.

A Faster Prostate MRI: Comparing a Novel Denoised, Single-Average T2 Sequence to the Conventional Multiaverage T2 Sequence Regarding Lesion Detection and PI-RADS Score Assessment

BACKGROUND

The T₂ w sequence is a standard component of a prostate MRI examination; however, it is time-consuming, requiring multiple signal averages to achieve acceptable image quality.

PURPOSE/HYPOTHESIS

To determine whether a denoised, single-average T₂ sequence (T₂ -R) is noninferior to the standard multiaverage T₂ sequence (T₂ -S) in terms of lesion detection and PI-RADS score assessment.

STUDY TYPE

Retrospective.

POPULATION

A total of 45 males (age range 60-75 years) who underwent clinically indicated prostate MRI examinations, 21 of whom had pathologically proven prostate cancer.

FIELD STRENGTH/SEQUENCE

A 3 T; T₂ w FSE, DWI with ADC maps, and dynamic contrast-enhanced images with color-coded perfusion maps. T₂ -R images were created from the raw data utilizing a single "average" with iterative denoising.

ASSESSMENT

Nine readers randomly assessed complete exams including T₂ -R and T₂ -S images in separate sessions. PI-RADS version 2.1 was used. All readers then compared the T₂ -R and T₂ -S images side by side to evaluate subjective preference. An additional detailed image quality assessment was performed by three senior level readers.

STATISTICAL TESTS

Generalized linear mixed effects models for differences in lesion detection, image quality features, and overall preference between T₂ -R and T₂ -S sequences. Intraclass correlation coefficients (ICC) were used to assess reader agreement for all comparisons. A significance threshold of P = 0.05 was used for all statistical tests.

RESULTS

There was no significant difference between sequences regarding identification of lesions with PI-RADS ≥3 (P = 0.10) or PI-RADS score (P = 0.77). Reader agreement was excellent for lesion identification (ICC = 0.84). There was no significant overall preference between the two sequences regarding image quality (P = 0.07, 95% CI: [-0.23, 0.01]). Reader agreement was good regarding sequence preference (ICC = 0.62).

DATA CONCLUSION

Use of single-average, denoised T₂ -weighted images was noninferior in prostate lesion detection or PI-RADS scoring when compared to standard multiaverage T₂ -weighted images.

EVIDENCE LEVEL

3.

TECHNICAL EFFICACY

Stage 3.

Dynamic evaluation of MRI-targeted, systematic and combined biopsy for prostate cancer diagnosis through 10 years of practice in a single institution

PURPOSE

To perform a dynamic evaluation of the prostate cancer (PCa) detection rate according to the biopsy strategy over 10 years of practice in a single institution that pioneered MRI-targeted fusion biopsy (MRI-TB).

METHODS

This stage 4 IDEAL study prospectively included all consecutive patients who underwent transrectal prostate biopsy for clinically suspected PCa between January 2010 and November 2020. Patients with positive MRI (PIRADS score ≥ 3) underwent both MRI-TB and systematic biopsy (SB) while those with negative MRI (PIRADS score < 3) underwent SB only. The main outcome was the evolution of the detection rate of clinically relevant PCa (csPCa; grade ≥ 2). The secondary outcome was the change in PCa detection rate according to the biopsy method.

RESULTS

A total of 2942 men underwent prostate MRI and a prostate biopsy: 2322 underwent MRI-TB and 620 had SB only. The detection rate of csPCa increased 2.5-fold from 23 to 58%. The detection rate of PCa and csPCa was significantly higher in patients who underwent MRI-TB compared to those who underwent SB only (67% vs. 52% and 40% vs. 32%, respectively (P < 0.001 for both comparisons)). The number of csPCa diagnosed by MRI-TB increased linearly over the study period and represented the majority of PCa diagnoses after 2016.

CONCLUSION

Implementation of MRI-TB in patients with positive MRI led to improved detection of csPCa.

Population‐based randomized trial of screening for clinically significant prostate cancer ProScreen: pilot study

Objectives

To evaluate the feasibility of a population‐based screening trial using prostate‐specific antigen (PSA), a kallikrein panel and multiparametric magnetic resonance imaging (MRI) aimed at minimizing overdiagnosis, while retaining mortality benefit.

Patients and Methods

Feasibility of the screening algorithm was evaluated in terms of participation, screening test results and cancer detection. A random sample of 400 men aged 65 years was identified from the population registry and invited for screening with three stepwise tests (PSA, kallikrein panel and MRI). Men with PSA levels ≥3 ng/mL were further tested with the kallikrein panel, and those with positive findings (risk >7.5%) were referred for prostate MRI. Men with positive MRI (Prostate Imaging Reporting and Data System [PI‐RADS] score 3–5) had targeted biopsies only. Men with negative MRI, but PSA density ≥0.15 underwent systematic biopsies.

Results

Of the 399 men invited, 158 (40%) participated and 27 had PSA levels ≥3 ng/mL (7% of the invited and 17% of the participants). Of these, 22 had a positive kallikrein panel (6% of the invited and 81% of the PSA‐positive men). Finally, 10 men (3% of the invited and 45% of 4Kscore [kallikrein panel]‐positive) had a suspicious MRI finding (PI‐RADS score ≥3) and five were diagnosed with a clinically significant prostate cancer (Gleason Grade Group [GG] ≥2) at fusion biopsy (3% of the participants), with two GG 1 cases (1%). Additional testing (kallikrein panel and MRI) after PSA reduced biopsies by 56%.

Conclusion

The findings constitute proof of principle for our screening protocol, as we achieved a substantial detection rate for clinically significant cancer with few clinically insignificant cases. Participation, however, was suboptimal.

A Prospective Study and Single-Center Experience: Effectivity of Fusion Prostate Biopsy in Biopsy-Naïve Patients

Objective

Fusion prostate biopsy (FPB) has become a popular technique in biopsy-naïve patients, though not accepted as a standard approach (yet). In this study, we aimed to present the clinical outcomes of biopsy-naïve patients who underwent FPB.

Material and methods

The study included 400 biopsy-naïve patients aged 45-75 years who had a prostate-specific antigen (PSA) level of 2-10 ng/ml and were detected with a Prostate Imaging-Reporting and Data System (PIRADS) ≥3 lesion on multiparametric prostate magnetic resonance imaging (mpMRI)-guided FPB. A combined biopsy (CB) was performed in each patient, in which 2-4 cores were obtained for suspicious lesions by targeted biopsy (TB) and then 12-core standard prostate biopsy (SPB) was conducted in the same session. Cancer detection rates, clinically significant prostate cancer (csPCa) detection rates, histological upgrading rates, and false negative rates were determined.

Results

The 400 patients had a mean age of 62.01±7.00 years and a mean PSA value of 6.84±1.87 ng/ml. Overall PCa detection rate was 50% (200/400). The csPCa detection rates for TB, SPB, and CB were 25.0%, 31.8%, and 44.0%, respectively (p<0.001). In PIRADS 3, 4, and 5 lesions, CB had a csPCa detection rate of 29.2%, 54%, and 64.8%, respectively (p<0.001). The ratio of false negativity was significantly higher for TB compared to SPB (43.2% vs. 27.8%, p=0.003), whereas no significant difference was found between these two techniques with regard to upgrading rates although TB had a higher rate (19.6% vs. 13.7%, p=0.144).

Conclusion

FPB, a combined approach involving TB and SPB, was revealed as the most successful technique in biopsy-naïve patients with PSA<10 ng/ml due to its high cancer detection rates and low false negative rates.

Clinical characteristics and oncological outcomes in negative multiparametric MRI patients undergoing robot-assisted radical prostatectomy

BACKGROUND

Efforts are ongoing to try and find ways to reduce the number of unnecessary prostate biopsies without missing clinically significant prostate cancers (csPCa). The utility of multiparametric magnetic resonance imaging (mpMRI) in detecting prostate cancer (PCa) shows promise to be used as triage test for systematic prostate biopsy. Our aim is to Study clinical parameters and oncological outcomes in men with negative mpMRI (nMRI; PI-RADS v2 scores of ≤ 2) who underwent robot-assisted radical prostatectomy (RARP) to evaluate nMRI's practicality as a biopsy triage test.

METHODS

Retrospective analysis of 331 men with nMRI who underwent RARP between 2014 and 2020 compared with men with positive mpMRI (pMRI; PI-RADS v2 scores ≥ 3, N = 1770). csPCa was defined as Gleason score ≥ 3 + 4 and biochemical recurrence (BCR) was defined as PSA > 0.2 ng/ml on two occasions. Biopsies were graded with the International Society of Urologic Pathology [ISUP] grade. Descriptive statistics for nMRI and pMRI were performed. Mann-Whitney U test was used for continuous variables and χ ² for categorical variables. Univariable and multivariable regression analyses were performed.

RESULTS

Univariable analysis shows statistically significant difference (p < .05) between median age (nMRI-61 years vs. pMRI 63 years), race (higher incidence of nMRI in African American men), use of 5-alpha reductase inhibitors (higher rate in nMRI). While incidence rates of family history of PCa, suspicious digital rectal examination (DRE) findings, median PSA levels and 4Kscore, were lower in nMRI versus pMRI. Rates of positive surgical margins and BCR were comparable in nMRI versus pMRI. Biopsy ISUP Grades I and II upgraded by 51% and 12%, respectively in final pathology. African American race and no history of the prior negative biopsy were significant predictors for upgrading.

CONCLUSION

Men with nMRI pose diagnostic challenges as they tend to be younger patients with lower rates of suspicious DRE findings and lower 4K scores, yet comparable oncological outcomes in csPCa rates, positive surgical margins, and BCR rates.

Diagnostic efficacy and safety of transperineal prostate targeted and systematic biopsy: The preliminary experience of first 100 cases

BACKGROUND

Post-biopsy urosepsis is a major concern for patient morbidity and cost. Trasperineal biopsy is reported to have less complications and higher detection rate of clinically significant prostate cancer (csPCa).

OBJECTIVES

To determine the diagnostic efficacy and safety of transperineal prostate biopsy in patients with elevated prostatic specific antigen (PSA).

MATERIAL AND METHODS

A prospective study included men with elevated PSA > 3 ng/ml and previous negative biopsy from January 2018 to April 2019. All patients had multiparametric magnetic resonance imaging (mpMRI) and suspicious lesions reported as Prostate Imaging Reporting and Data System (PIRADS) score version 2. Average twelve systematic and two targeted cores were biopsied under general anaesthesia. Patients received single dose of antibiotic prebiopsy.

RESULTS

100 Consecutive patients having median age 64.0 years and median PSA of 6.1ng/ml were included for mpMRI-US fusion transperineal biopsies. Cancer detection rate was 45% (targeted 38% and systematic 22%) and csPCa were detected in 75.55% (targeted 86.84% and systematic 59.09%). MRI-US fusion targeted biopsies detected 63.88% csPCa in PIRADS 5, 33.33% in PIRADS 4 and 5.88% in PIRADS 3 lesions. PSA > 10 (p = 0.012), PSA density > 0.15 (p = 0.0002), and PIRADS 5 (0.0001) were significantly associated with PCa. Factors like Age (0.0001), initial PSA (0.022) and PSA density (0.006) were significant on univariate analysis while age (0.0001) was significant on multivariate analysis. There was no case of urinary tract infection.

CONCLUSIONS

Transperineal prostate biopsy is safe and effective in diagnosing csPCa. There is no risk of sepsis and major complications.

Computer-Aided Diagnosis Improves the Detection of Clinically Significant Prostate Cancer on Multiparametric-MRI: A Multi-Observer Performance Study Involving Inexperienced Readers

Recently, Computer Aided Diagnosis (CAD) systems have been proposed to help radiologists in detecting and characterizing Prostate Cancer (PCa). However, few studies evaluated the performances of these systems in a clinical setting, especially when used by non-experienced readers. The main aim of this study is to assess the diagnostic performance of non-experienced readers when reporting assisted by the likelihood map generated by a CAD system, and to compare the results with the unassisted interpretation. Three resident radiologists were asked to review multiparametric-MRI of patients with and without PCa, both unassisted and assisted by a CAD system. In both reading sessions, residents recorded all positive cases, and sensitivity, specificity, negative and positive predictive values were computed and compared. The dataset comprised 90 patients (45 with at least one clinically significant biopsy-confirmed PCa). Sensitivity significantly increased in the CAD assisted mode for patients with at least one clinically significant lesion (GS > 6) (68.7% vs. 78.1%, p = 0.018). Overall specificity was not statistically different between unassisted and assisted sessions (94.8% vs. 89.6, p = 0.072). The use of the CAD system significantly increases the per-patient sensitivity of inexperienced readers in the detection of clinically significant PCa, without negatively affecting specificity, while significantly reducing overall reporting time.

Clinical outcomes associated with prostate cancer conspicuity on biparametric and multiparametric MRI: a protocol for a systematic review and meta-analysis of biochemical recurrence following radical prostatectomy

INTRODUCTION

There is an increasing body of evidence to suggest that visibility of prostate cancer on magnetic resonance (MRI) may be related to likelihood of adverse pathological outcomes. Biochemical recurrence (BCR) after radical prostatectomy remains a significant clinical challenge and a means of predicting likelihood of this prior to surgery could inform treatment choice. It appears that MRI could be a potential candidate strategy for BCR prediction, and as such, there is a need to review extant literature on the prognostic capability of MRI. Here, we describe a protocol for a systematic review and meta-analysis of the utility of biparametric MRI (bpMRI) and multiparametric MRI (mpMRI) in predicting BCR following radical prostatectomy for prostate cancer treatment.

METHODS AND ANALYSIS

PubMed, MEDLINE, Embase and Cochrane databases will be searched and screening will be guided by the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. In order to meet the inclusion criteria, papers must be English-language articles involving patients who have had bpMRI or mpMRI for suspected prostate cancer and have undergone radical prostatectomy as definitive therapy. Patients must have had prostate-specific antigen monitoring before and after surgery. All relevant papers published from July 1977 to October 2020 will be eligible for inclusion. The Newcastle-Ottawa score will be used to determine the quality and bias of the studies. This protocol is written in-line with the PRISMA protocol 2015 checklist.

ETHICS AND DISSEMINATION

There are no relevant ethical concerns. Dissemination of this protocol will be via peer-reviewed journals as well as national and international conferences.

PROSPERO REGISTRATION NUMBER

CRD42020206074.

The diagnostic accuracy of multiparametric MRI for detection and localization of prostate cancer depends on the affected region

Objectives

To determine the diagnostic accuracy of 3T multiparametric magnetic resonance imaging (mpMRI) for detecting and locating prostate cancer (PCa) on Dickinson's 27-sector map, using histopathology specimens from radical prostatectomy (RP) as the reference standard.

Patients and methods

The authors studied a continuous series of 140 patients who underwent RP over three consecutive years. Prior to RP, all patients had mpMRI for detection and localization of PCa and further assessment by biopsy. To minimize the potential of disease progression, 25 patients were excluded because the interval between mpMRI and RP exceeded 6 months, which left 115 patients eligible for analysis. The mpMRI findings were reported using the Prostate Imaging-Reporting and Data System (PI-RADS) v2, considering PI-RADS ≥ 3 to indicate PCa. The histopathology findings from RP specimens were graded using the Gleason scoring system, considering Gleason ≥ 6 to indicate PCa. The location of the tumors was mapped on Dickinson's 27-sector map for both mpMRI and histopathology and compared by rigid sector-by-sector matching.

Results

The cohort of 115 patients eligible for analysis was aged 66.5 ± 6.0 years at RP. Of the 3105 sectors analyzed, there were 412 true positives (13%), 28 false positives (1%), 68 false negatives (2%), and 2597 true negatives (84%). Across the 27 sectors of the prostate, mpMRI sensitivity ranged from 50% to 100% and specificity from 96% to 100%, while PPV ranged from 50% to 100%, and NPV from 91% to 100%. For the anterior prostate, mpMRI had a sensitivity of 80% (CI, 71%-86%), specificity of 99% (CI, 99%-100%), PPV of 91% (CI, 83%-95%), and NPV of 99% (CI, 98%-99%). For the posterior prostate, mpMRI had a sensitivity of 88% (CI, 84%-91%), specificity of 98% (CI, 97%-99%), PPV of 94% (CI, 92%-96%), and NPV of 96% (CI, 94%-97%). Overall, mpMRI had a sensitivity of 86%, specificity of 99%, PPV of 94%, and NPV of 97%.

Conclusions

The accuracy of mpMRI in detecting and locating prostate tumors depends on the affected region, but its high NPV across all sectors suggests that negative findings may not need corroboration by other techniques.

Comparison of MRI, PSMA PET/CT, and Fusion PSMA PET/MRI for Detection of Clinically Significant Prostate Cancer

PURPOSE

The aim of our study is to compare the efficacy of positron emission tomography (PET) and magnetic resonance imaging (MRI) for detecting intraprostatic lesions in patients with clinically significant prostate cancer who underwent radical prostatectomy; additionally, investigate the benefits of rostate-specific membrane antigen (PSMA) PET-MR software fusion images to the diagnosis.

METHODS

Thirty patients, who underwent radical prostatectomy between June 2015 and April 2018, were included in the study. Subjects with gallium PSMA PET-CT and multiparametric prostate MRI performed according to Prostate Imaging Reporting and Data System v2 criteria in our clinic were included in the study. 68Ga-PSMA PET-CT images were fused with MR sequences for analysis.

RESULTS

The mean age of cases was 63.2 years (ranged from 45 to 79 years). Index lesions of 29 cases were detected by MRI and 22 of them by PET CT. Both modalities were found to be less sensitive for detection of bilaterality and multifocality (42.85% and 20% for MRI, 28.57% and 20% for PET CT, respectively). There was no statistically significant difference between modalities. It was observed that if a clinically significant tumor focus was not detected by MRI, it was small (6 mm or less) in diameter or had a low Gleason score.

CONCLUSIONS

Software fusion PSMA PET-MRI increased the sensitivity of the index lesion identification compared with PSMA PET-CT and also increased the sensitivity of real lesion size identification compared with multiparametric prostate MRI.

Adding Value in Radiology Reporting

The major goal of the radiology report is to deliver timely, accurate, and actionable information to the patient care team and the patient. Structured reporting offers multiple advantages over traditional free-text reporting, including reduction in diagnostic error, comprehensiveness, adherence to national consensus guidelines, revenue capture, data collection, and research. Various technological innovations enhance integration of structured reporting into everyday clinical practice. This review discusses the benefits of innovations in radiology reporting to the clinical decision process, the patient experience, the cost of imaging, and the overall contributions to the health of the population. Future directions, including the use of artificial intelligence, are reviewed.

Optimizing size thresholds for detection of clinically significant prostate cancer on MRI: Peripheral zone cancers are smaller and more predictable than transition zone tumors

PURPOSE

To evaluate if size-based cut-offs based on MR imaging can successfully assess clinically significant prostate cancer (csPCA). The goal was to improve the currently applied size-based differentiation criterion in PI-RADS.

METHODS AND MATERIALS

MRIs of 293 patients who had undergone 3 T MR imaging with subsequent confirmation of prostate cancer on systematic and targeted MRI/TRUS-fusion biopsy were re-read by three radiologists. All identifiable tumors were measured on T2WI for lesions originating in the transition zone (TZ) and on DWI for lesions from the peripheral zone (PZ) and tabulated against their Gleason grade.

RESULTS

309 lesions were analyzed, 213 (68.9 %) in the PZ and 96 (31.1 %) in the TZ. ROC-Analysis showed a stronger correlation between lesion size and clinically significant (defined as Gleason Grade Group ≥ 2) prostate cancer (PCa) for the PZ (AUC = 0.73) compared to the TZ (AUC = 0.63). The calculated Youden index resulted in size cut-offs of 14 mm for PZ and 21 mm for TZ tumors.

CONCLUSION

Size cut-offs can be used to stratify prostate cancer with different optimal size thresholds in the peripheral zone and transition zone. There was a clearer separation of clinically significant tumors in peripheral zone cancers compared to transition zone cancers. Future iterations of PI-RADS could therefore take different size-based cut-offs for peripheral zone and transition zone cancers into account.

Manual prostate cancer segmentation in MRI: interreader agreement and volumetric correlation with transperineal template core needle biopsy

OBJECTIVES

To assess interreader agreement of manual prostate cancer lesion segmentation on multiparametric MR images (mpMRI). The secondary aim was to compare tumor volume estimates between MRI segmentation and transperineal template saturation core needle biopsy (TTSB).

METHODS

We retrospectively reviewed patients who had undergone mpMRI of the prostate at our institution and who had received TTSB within 190 days of the examination. Seventy-eight cancer lesions with Gleason score of at least 3 + 4 = 7 were manually segmented in T2-weighted images by 3 radiologists and 1 medical student. Twenty lesions were also segmented in apparent diffusion coefficient (ADC) and dynamic contrast enhanced (DCE) series. First, 20 volumetric similarity scores were computed to quantify interreader agreement. Second, manually segmented cancer lesion volumes were compared with TTSB-derived estimates by Bland-Altman analysis and Wilcoxon testing.

RESULTS

Interreader agreement across all readers was only moderate with mean T2 Dice score of 0.57 (95%CI 0.39-0.70), volumetric similarity coefficient of 0.74 (0.48-0.89), and Hausdorff distance of 5.23 mm (3.17-9.32 mm). Discrepancy of volume estimate between MRI and TTSB was increasing with tumor size. Discrepancy was significantly different between tumors with a Gleason score 3 + 4 vs. higher grade tumors (0.66 ml vs. 0.78 ml; p = 0.007). There were no significant differences between T2, ADC, and DCE segmentations.

CONCLUSIONS

We found at best moderate interreader agreement of manual prostate cancer segmentation in mpMRI. Additionally, our study suggests a systematic discrepancy between the tumor volume estimate by MRI segmentation and TTSB core length, especially for large and high-grade tumors.

KEY POINTS

• Manual prostate cancer segmentation in mpMRI shows moderate interreader agreement. • There are no significant differences between T2, ADC, and DCE segmentation agreements. • There is a systematic difference between volume estimates derived from biopsy and MRI.

The Utility of Diffusion-Weighted Imaging and Perfusion Magnetic Resonance Imaging Parameters for Detecting Clinically Significant Prostate Cancer

Introduction

To establish the diagnostic performance of the parameters obtained from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion-weighted imaging at 3T in discriminating between non-clinically significant prostate cancers (ncsPCa, Gleason score [GS] < 7) and clinically significant prostate cancers (csPCa, GS ≥ 7) in the peripheral zone.

Materials and Methods

Twenty-six male patients with peripheral zone prostate cancer (PCa) who had undergone 3T multiparametric magnetic resonance imaging (MRI) scan prior to biopsy were included in the study and evaluated retrospectively. The GS was obtained by both standard 12-core transrectal ultrasound guided biopsy and targeted MRI-US fusion biopsy and then confirmed by prostatectomy, if available. For each confirmed tumour focus, DCE-derived quantitative perfusion metrics (Ktrans, Kep, Ve, initial area under the curve [AUC]), the apparent diffusion coefficient (ADC) value, and normalized versions of quantitative metrics were measured and correlated with the GS.

Results

Ktrans had the highest diagnostic accuracy value of 82% among the DCE-MRI parameters (AUC 0.90), and ADC had the strongest diagnostic accuracy value of 87% among the overall parameters (AUC 0.92). The combination of ADC and Ktrans have higher diagnostic performance with the area under the receiver operating characteristic curve being 0.98 (sensitivity 0.94; specificity 0.89; accuracy 0.92) compared to the individual evaluation of each parameter alone. The GS showed strong negative correlations with ADC (r = −0.72) and normalized ADC (r = −0.69) as well as a significant positive correlation with Ktrans (r = 0.69).

Conclusion

The combination of Ktrans and ADC and their normalized versions may help differentiate between ncsPCa from csPCa in the peripheral zone.

Magnetic Resonance-Guided Prostate Ablation

In 2019, the American Cancer Society (ACS) estimates that 174,650 new cases of prostate cancer will be diagnosed and 31,620 will die due to the prostate cancer in the United States. Prostate cancer is often managed with aggressive curative intent standard therapies including radiotherapy or surgery. Regardless of how expertly done, these standard therapies often bring significant risk and morbidity to the patient's quality of life with potential impact on sexual, urinary, and bowel functions. Additionally, improved screening programs, using prostatic-specific antigen and transrectal ultrasound-guided systematic biopsy, have identified increasing numbers of low-risk, low-grade "localized" prostate cancer. The potential, localized, and indolent nature of many prostate cancers presents a difficult decision of when to intervene, especially within the context of the possible comorbidities of aggressive standard treatments. Active surveillance has been increasingly instituted to balance cancer control versus treatment side effects; however, many patients are not comfortable with this option. Although active debate continues on the suitability of either focal or regional therapy for the low- or intermediate-risk prostate cancer patients, no large consensus has been achieved on the adequate management approach. Some of the largest unresolved issues are prostate cancer multifocality, limitations of current biopsy strategies, suboptimal staging by accepted imaging modalities, less than robust prediction models for indolent prostate cancers, and safety and efficiency of the established curative therapies following focal therapy for prostate cancer. In spite of these restrictions, focal therapy continues to confront the current paradigm of therapy for low- and even intermediate-risk disease. It has been proposed that early detection and proper characterization may play a role in preventing the development of metastatic disease. There is level-1 evidence supporting detection and subsequent aggressive treatment of intermediate- and high-risk prostate cancer. Therefore, accurate assessment of cancer risk (i.e., grade and stage) using imaging and targeted biopsy is critical. Advances in prostate imaging with MRI and PET are changing the workup for these patients, and advances in MR-guided biopsy and therapy are propelling prostate treatment solutions forward faster than ever.

Machine learning classifiers can predict Gleason pattern 4 prostate cancer with greater accuracy than experienced radiologists

OBJECTIVE

The purpose of this study was: To test whether machine learning classifiers for transition zone (TZ) and peripheral zone (PZ) can correctly classify prostate tumors into those with/without a Gleason 4 component, and to compare the performance of the best performing classifiers against the opinion of three board-certified radiologists.

METHODS

A retrospective analysis of prospectively acquired data was performed at a single center between 2012 and 2015. Inclusion criteria were (i) 3-T mp-MRI compliant with international guidelines, (ii) Likert ≥ 3/5 lesion, (iii) transperineal template ± targeted index lesion biopsy confirming cancer ≥ Gleason 3 + 3. Index lesions from 164 men were analyzed (119 PZ, 45 TZ). Quantitative MRI and clinical features were used and zone-specific machine learning classifiers were constructed. Models were validated using a fivefold cross-validation and a temporally separated patient cohort. Classifier performance was compared against the opinion of three board-certified radiologists.

RESULTS

The best PZ classifier trained with prostate-specific antigen density, apparent diffusion coefficient (ADC), and maximum enhancement (ME) on DCE-MRI obtained a ROC area under the curve (AUC) of 0.83 following fivefold cross-validation. Diagnostic sensitivity at 50% threshold of specificity was higher for the best PZ model (0.93) when compared with the mean sensitivity of the three radiologists (0.72). The best TZ model used ADC and ME to obtain an AUC of 0.75 following fivefold cross-validation. This achieved higher diagnostic sensitivity at 50% threshold of specificity (0.88) than the mean sensitivity of the three radiologists (0.82).

CONCLUSIONS

Machine learning classifiers predict Gleason pattern 4 in prostate tumors better than radiologists.

KEY POINTS

• Predictive models developed from quantitative multiparametric magnetic resonance imaging regarding the characterization of prostate cancer grade should be zone-specific. • Classifiers trained differently for peripheral and transition zone can predict a Gleason 4 component with a higher performance than the subjective opinion of experienced radiologists. • Classifiers would be particularly useful in the context of active surveillance, whereby decisions regarding whether to biopsy are necessitated.

Accelerated 3D T2 w-imaging of the prostate with 1-millimeter isotropic resolution in less than 3 minutes

PURPOSE

To achieve 3D T2 w imaging of the prostate with 1-mm isotropic resolution in less than 3 min.

METHODS

We devised and implemented a 3D T2 -prepared multishot balanced steady state free precession (T2 prep-bSSFP) acquisition sequence with a variable density undersampled trajectory combined with a total variation regularized iterative SENSE (TV-SENSE) reconstruction. Prospectively undersampled images of the prostate (acceleration factor R = 3) were acquired in 11 healthy subjects in an institutional review board-approved study. Image quality metrics (subjective signal-to-noise ratio, contrast, sharpness, and overall prostate image quality) were evaluated by 2 radiologists. Scores of the proposed accelerated sequence were compared using the Wilcoxon signed-rank and Kruskal-Wallis non-parametric tests to prostate images acquired using a fully sampled 3D T2 prep-bSSFP acquisition, and with clinical standard 2D and 3D turbo spin echo (TSE) T2 w acquisitions. A P-value < 0.05 was considered significant.

RESULTS

The 3× accelerated 3D T2 prep-bSSFP images required a scan time (min:s) of 2:45, while the fully sampled 3D T2 prep-bSSFP and clinical standard 3D TSE images were acquired in 8:23 and 7:29, respectively. Image quality scores (contrast, sharpness, and overall prostate image quality) of the accelerated 3D T2 prep-bSSFP, fully sampled T2 prep-bSSFP, and clinical standard 3D TSE acquisitions along all 3 spatial dimensions were not significantly different (P > 0.05).

CONCLUSION

3D T2 w images of the prostate with 1-mm isotropic resolution can be acquired in less than 3 min, with image quality that is comparable to a clinical standard 3D TSE sequence but only takes a third of the acquisition time.

Assessment of PI-RADS v2 categories ≥ 3 for diagnosis of clinically significant prostate cancer

PURPOSE

To assess the diagnostic accuracy of PI-RADS v2 categories ≥ 3 to detect clinically significant prostate cancer (csPCa) against histopathology of Transperineal Mapping Biopsy (TPMB).

MATERIALS AND METHODS

IRB-approved retrospective cohort study included 47 men who had 3.0 T multi-parametric MRI (mpMRI) and TPMB of prostate. Two radiologists independently evaluated T2, DWI, ADC map, and DCE images using PI-RADS v2 categories. A third radiologist served as tie-breaker. PI-RADS v2 score (PS) ≥ 3 lesions were correlated with 3D model of TPMB (3DTPMB) results based on prostate sectors. Two groups of csPCa status were separately analyzed for accuracy measures at lesion and person levels: Group 1 with GS (Gleason Score) ≥ 7 and group 2 with tumor volume ≥ 0.5 cc. Inter-rater reliability for PS and MR lexicon was calculated.

RESULTS

Forty-seven patients with 3DTPMB had at least one lesion with PS ≥ 3 on mpMRI. PS of 5 had high PPV and high specificity of 100% at the lesion and person levels. Sensitivity of a PS ≥ 3 was 68.27% for group 1 and was 48.39% for group 2. Specificity was 93.56% for group 1 and was 95.53% for group 2. At the person level, sensitivity of PS ≥ 3 was 81.25% for group 1 and was 82.35% for group 2. Specificity was 32.26% for group 1 and was 53.85% for group 2.

CONCLUSION

PI-RADS v2 category of 5 had high PPV and specificity; however, combined PS ≥ 3 had mixed performance in detection of csPCa.

68Ga-PSMA-11 PET/MR Detects Local Recurrence Occult on mpMRI in Prostate Cancer Patients After HIFU

High-intensity focused ultrasound (HIFU) is a promising new modality for the treatment of localized prostate cancer (PCa). Follow-up of patients is recommended with biopsies and multiparametric MRI (mpMRI). However, mpMRI in the postinterventional setting is often false-negative. It was our aim to investigate if the new tracer targeting the prostate-specific membrane antigen (⁶⁸Ga-PSMA-11) could be used to localize recurrent disease with PET/MR in patients with discrepant findings between mpMRI and template biopsies. Methods: Interim analysis was performed of the first 10 patients scanned between September 2016 and May 2018 with positive template biopsy and negative mpMRI after HIFU from an ongoing clinical trial (NCT02265159). All patients underwent ⁶⁸Ga-PSMA-11 PET/MRI within 3 mo. Four prostatic quadrants were defined, and for every quadrant suspicion for recurrence was rated on a 5-point Likert scale from definitely no recurrence (1) to highly suspected of recurrence (5), with 4 used as a cutoff for suspected disease based on PET/MRI by a masked reader. ⁶⁸Ga-PSMA-11 uptake of suspected lesions and background areas was measured with the SUV_max The apparent diffusion coefficient values of lesions and background were given for each segment. PET/MRI scans were compared with the template biopsy results, including corresponding Gleason scores (GS), number of positive cores, and tumor length. Results: The quadrant-based sensitivity, specificity, and positive and negative predictive values for PET/MRI were 55%, 100%, 100%, and 85%, respectively. Patient-based PET/MRI was negative in 4 cases with GS 3 + 4 and a tumor length between 0.1 and 3 mm. All tumor lesions with GS 4 + 3 or higher were detected on PET/MRI. Conclusion: Our preliminary results indicate that ⁶⁸Ga-PSMA-11-PET/MR has the potential to localize PCa recurrence after HIFU occult on mpMRI.

[USEFULNESS OF VIVID (VISUALIZATION OF VARIOUS INTEGRATION WITH DIFFUSION) ON COGNITIVE FUSION PROSTATE BIOPSY]

(Purpose) We created an image reconstructing multiparametric MRI system called VIVID (Visualization of Various Integration with Diffusion) and examined the efficacy of VIVID in detecting prostate cancer. (Methods and materials) The subjects were 80 patients who underwent one target biopsy with reference to MRI images in addition to 8-20 biopsies. (Results) The significant cancer detection rate was 61%, the significant cancer detection rate of PI-RADS 4 or 5 was 55%, and the significant cancer detection rate of VIVID score 4 or 5 was 55%. Three cases with PI-RADS 4 at TZ lesion with positive T2WI only were evaluated as having VIVID scores 1 or 2. Cancer was not detected with target biopsy from the site. (Conclusion) Our finding suggest that VIVID correctly excludes TZ lesions with only T2WI positively in multiparametric MRI.

Initial experience of magnetic resonance imaging/ultrasonography fusion transperineal biopsy: Biopsy techniques and results for 75 patients

Purpose

The aim of this study is to describe the technique and to report early results of transperineal magnetic resonance imaging and ultrasonography (MRI-US) fusion biopsy.

Materials and Methods

A total of 75 patients underwent MRI-US fusion transperineal biopsy. Targeted biopsy via MRI-US fusion imaging was carried out for cancer-suspicious lesions with additional systematic biopsy. Detection rates for overall and clinically significant prostate cancer (csPCa) were evaluated and compared between systematic and targeted biopsy. In addition, further investigation into the detection rate according to prostate imaging reporting and data system (PI-RADS) score was done. Results of repeat biopsies were also evaluated.

Results

Overall cancer detection rate was 61.3% (46 patients) and the detection rate for csPCa was 42.7% (32 patients). Overall detection rates for systematic and targeted biopsy were 41.3% and 57.3% (p<0.05), respectively. Detection rates for csPCa were 26.7% and 41.3%, respectively (p<0.05). The cancer detection rates via MRI fusion target biopsy were 30.8% in PI-RADS 3, 62.1% in PI-RADS 4 and 89.4% in PI-RADS 5. Rates of csPCa missed by targeted biopsy and systematic biopsy were 0.0% and 25.0%, respectively. The cancer detection rate in repeat biopsies was 61.1% (11 among 18 patients) in which 55.5% of cancer suspected lesions were located in the anterior portion.

Conclusions

Transperineal MRI-US fusion biopsy is useful for improving overall cancer detection rate and especially detection of csPCa. Transperineal MRI-US targeted biopsy show potential benefits to improve cancer detection rate in patients with high PI-RADS score, tumor located at the anterior portion and in repeat biopsies.

The diagnostic accuracy of multiparametric magnetic resonance imaging before biopsy in the detection of prostate cancer

OBJECTIVES

To determine the extent to which clinically significant prostate cancer (csPCa) can be detected in a routine National Health Service setting in men with no previous biopsy, when multiparametric magnetic resonance imaging (mpMRI) is introduced into the diagnostic pathway.

PATIENTS AND METHODS

In all, 1 090 mpMRIs were performed between July 2013 and April 2016 in biopsy-naïve men with an abnormal prostate-specific antigen level and/or digital rectal examination. Data were collected from patient records at the Royal Devon and Exeter NHS Foundation Trust. mpMRI Prostate Imaging Reporting and Data System (PI-RADS) scores were compared to transperineal or transrectal ultrasonography (TRUS)-guided biopsy findings as the reference standard. csPCa was defined as Gleason score of ≥3+4. The diagnostic accuracy of mpMRI was also assessed.

RESULTS

The mpMRI was interpretable in 1 023 men and 792 underwent biopsy, of which 106 were transperineal. The median number of cores taken in transperineal and TRUS-guided biopsy were 10 and 6, respectively. The detection rate of csPCa was 37%; csPCa rose from 15% of PI-RADS 1 and 2 to 86% of PI-RADS 5. The sensitivity, negative predictive value, specificity, and positive predictive value were 82%, 85%, 59% and 54%, respectively. The study is limited by its retrospective nature and lack of reporting of follow-up for 'missed cancers'. Men with low mpMRI PI-RADS were also less likely to undergo biopsy. Whilst this selection bias may overestimate the detection rate of csPCa, this reflects the shared decisions patients and clinicians make in day-to-day practice outside of research centres.

CONCLUSION

In a routine clinical setting, the higher the mpMRI PI-RADS, the greater the detection rate of csPCa in biopsy-naïve men. A normal mpMRI does not exclude csPCa; however, mpMRI may have utility in informing shared-decision making on whether to proceed to biopsy and subsequent treatment.

MR-Guided Prostate Interventions

Prostate cancer is the most commonly diagnosed noncutaneous cancer and second leading cause of death in men. Many patients with clinically organ-confined prostate cancer undergo definitive treatment of the whole gland, including radical prostatectomy, radiation therapy, and cryosurgery. Active surveillance is a growing alternative option for patients with documented low-volume and low-grade prostate cancer. However, many patients are wanting a less morbid focal treatment alternative. With recent advances in software and hardware of magnetic resonance imaging (MRI), multiparametric MRI of the prostate has been shown to improve the accuracy in detecting and characterizing clinically significant prostate cancer. Targeted biopsy is increasingly utilized to improve the yield of MR detected, clinically significant prostate cancer and to decrease in detection of indolent prostate cancer. MR-guided targeted biopsy techniques include cognitive MR fusion transrectal ultrasound (TRUS) biopsy, in-bore transrectal targeted biopsy using robotic transrectal device, and in-bore direct MR-guided transperineal biopsy with a software based transperineal grid template. In addition, advances in MR-compatible thermal ablation technology allow accurate focal or regional delivery of thermal ablative energy to the biopsy-proved, MRI-detected tumor. MR-guided ablative treatment options include cryoablation, laser ablation, and high-intensity focused ultrasound with real-time or near simultaneous monitoring of the ablation zone. We present a contemporary review of MR-guided techniques for prostatic interventions.

Prostate Cancer Detection with Multiparametric MRI: A Comparison of 1 M-Concentration Gadobutrol with 0.5 M-Concentration Gadolinium-Based Contrast Agents

INTRODUCTION

Gadobutrol (Gd-DO3A-butrol) (Gadovist®) is a macrocyclic gadolinium-based contrast agent for magnetic resonance imaging (MRI) formulated at 1.0 mmol Gd/ml. Gadobutrol's higher concentration compared to other contrast agents (0.5 mmol Gd/ml) is associated with higher T1 relaxivity. We examined whether gadobutrol increases the accuracy of prostate cancer detection using dynamic contrast-enhanced MRI.

MATERIALS AND METHODS

Multiparametric MRI was performed in 379 patients: 94 patients received 1 M gadobutrol while 285 randomly received equivalent doses of 0.5 M gadoterate meglumine or gadopentetate dimeglumine. MRI images were retrospectively and blindly assessed for the presence of cancer by comparing them with prostate biopsy findings.

RESULTS

The specificity and accuracy were significantly higher with 1 M gadobutrol than 0.5 M of the other contrast agents. There were no significant differences in the sensitivity, or positive and negative predictive values.

CONCLUSION

Multiparametric MRI using 1 M gadobutrol may improve the accuracy of prostate cancer detection.

Poor reproducibility of PIRADS score in two multiparametric MRIs before biopsy in men with elevated PSA

Purpose

Since January 2015, all men referred to urologists in Norway due to elevated PSA or other suspicion of prostate cancer underwent multiparametric MRI (mpMRI) before prostate biopsy. At our hospital, patients and the initial MRI were assessed by an urologist and if deemed necessary, patients were referred to another institution for MR/US fusion biopsies. Before MR/US biopsy, patients underwent a second mpMRI. Since we noticed disagreement of these two mpMRIs before biopsy, we retrospectively assessed the level of agreement between the two mpMRIs from the two institutions.

Methods

During the first 6 months of 2015, 292 patients were referred to our outpatient clinic. We referred 126 patients of these to the other institution for MR/US fusion biopsy. The 2 mpMRIs were performed within 4 weeks. We analyzed MR reports and schematics for number of lesions and highest PIRADS score per side of the prostate and histological result of the biopsies. Bland–Altman’s plot was used to compare the level of agreement between the two mpMRIs of the same patient before biopsy.

Results

There was a poor level of agreement between the two mpMRIs and a statistically significant difference in PIRADS scores. Regression analysis showed that there was no proportional or systematic bias.

Conclusion

In unselected patients with elevated PSA, there seems to be a significant variation of mpMRI results across institutions. The PIRADS scoring system needs to be validated with regards to MR equipment, mpMRI protocols and inter-reader variability of radiologists.

Preventing clinical progression and need for treatment in patients on active surveillance for prostate cancer

PURPOSE OF REVIEW

Active surveillance is an established treatment option for men with localized, low-risk prostate cancer (CaP). It entails the postponement of immediate therapy with the option of delayed intervention upon disease progression. The rate of clinical progression and need for treatment on active surveillance is approximately 50% over 15 years. The present review summarizes recent data on current methods, attempting to prevent clinical progression.

RECENT FINDINGS

Patient selection for active surveillance is the first mandatory step required to lower progression. Adherence to active surveillance protocols is critical in making sure patients are monitored well and treated early when progression occurs. Before active surveillance allocation and during active surveillance follow-up, methods involving multiparametric MRI, prostate specific antigen derivatives, biopsy factors, urinary, tissue and genetic markers can be used to prevent clinical progression and/or identify those at risk for progression. Medications such as 5α-reductase inhibitors and others might inhibit disease progression in patients on active surveillance.

SUMMARY

Active surveillance is required because of overdiagnosis, along with our inability to accurately predict individual CaP behavior. Several methods can potentially reduce the risk of CaP progression in patients with active surveillance. However, a measure of uncertainty and fear of progression will always accompany patients with active surveillance and the physicians treating them.

Patient selection for prostate focal therapy in the era of active surveillance: an International Delphi Consensus Project

BACKGROUND

Whole-gland extirpation or irradiation is considered the gold standard for curative oncological treatment for localized prostate cancer, but is often associated with sexual and urinary impairment that adversely affects quality of life. This has led to increased interest in developing therapies with effective cancer control but less morbidity. We aimed to provide details of physician consensus on patient selection for prostate focal therapy (FT) in the era of contemporary prostate cancer management.

METHODS

We undertook a four-stage Delphi consensus project among a panel of 47 international experts in prostate FT. Data on three main domains (role of biopsy/imaging, disease and patient factors) were collected in three iterative rounds of online questionnaires and feedback. Consensus was defined as agreement in ⩾80% of physicians. Finally, an in-person meeting was attended by a core group of 16 experts to review the data and formulate the consensus statement.

RESULTS

Consensus was obtained in 16 of 18 subdomains. Multiparametric magnetic resonance imaging (mpMRI) is a standard imaging tool for patient selection for FT. In the presence of an mpMRI-suspicious lesion, histological confirmation is necessary prior to FT. In addition, systematic biopsy remains necessary to assess mpMRI-negative areas. However, adequate criteria for systematic biopsy remains indeterminate. FT can be recommended in D'Amico low-/intermediate-risk cancer including Gleason 4+3. Gleason 3+4 cancer, where localized, discrete and of favorable size represents the ideal case for FT. Tumor foci <1.5 ml on mpMRI or <20% of the prostate are suitable for FT, or up to 3 ml or 25% if localized to one hemi-gland. Gleason 3+3 at one core 1mm is acceptable in the untreated area. Preservation of sexual function is an important goal, but lack of erectile function should not exclude a patient from FT.

CONCLUSIONS

This consensus provides a contemporary insight into expert opinion of patient selection for FT of clinically localized prostate cancer.

Score 3 prostate lesions: a gray zone for PI-RADS v2

Prostate Imaging Reporting and Data System version 2 (PI-RADS v2) does not offer a precise guidance on the clinical management (biopsy or not biopsy) for PI-RADS v2 score 3 lesions. Lesion volume calculated on biparametric MRI (bpMRI) [T2-weighted imaging (T2WI) and diffusion-weighted imaging (DWI)] by introducing a cut-off of 0.5 mL, allows to distinguish the lesions assigned by the multiparametric MRI (mpMRI) to the category PI-RADS v2 score 3 in two subgroups: a) Indolent or low risk lesions with volume <0.5 mL, and b) Significant or high risk lesions with volume ≥0.5 mL. For mpMRI lesions assigned to PI-RADS v2 score 3, we suggest the following management: 1) Subgroup a (low-risk lesion): Clinical surveillance (accurate evaluation of age and clinical informations, periodic monitoring of prostate specific antigen value and repeated bpMRI 1 year later); 2) Subgroup b (high-risk lesion): Targeted biopsy. The proposed management would reduce the use of unnecessary biopsies and increase the diagostic yield of significant prostate cancer of approximately 50% and 30% respectively. These approaches encourage the radiologist to adopt MRI lesion volume to improve PI-RADS v2 and to optimize the management of PI-RADS v2 score 3 lesions.

[Prostate gland - what would urologists like to know from radiologists?]

A more than 100-year period, where the prostate was only seen and treated as a whole is coming to an end right now. Finally, high resolution imaging is providing deep insights and detailed information so that new therapeutic procedures can aim for the smallest targets within the gland. The long-standing wish of patients for individual noninvasive diagnostics and treatment of prostate diseases can now be fulfilled by providing new tailored concepts; however, in order to transfer the enormous amount of new information into the specific clinical patient situation, a closely knit interdisciplinary approach is required. In this setting, the traditional outpatient consultation service is overstretched in every aspect. It is now the time for new innovative constructs. The current one-sided service concept for urologists, radiologists and radiation therapists is therefore behind the times and the development of a "prostate management team" with equally cooperating partners from each specialty is the task for the future.

Standards for MRI reporting-the evolution to PI-RADS v 2.0

Prostate cancer (PCa) remains a leading cause of death in the United States, but the vast majority of men diagnosed with PCa will die from other causes. While historically the capability of assessing the risk of life-threatening versus indolent PCa has relied heavily on serum prostate-specific antigen (PSA) and transrectal ultrasound (TRUS), multiparametric magnetic resonance imaging (mpMRI) has emerged as the leading tool for detection and characterization of clinically significant PCa. However, wide variations and lack of standardization of mpMRI data acquisition, interpretation, and reporting have hampered its progress. The development of a set of consensus guidelines, initially called Prostate Imaging and Reporting and Data System (PI-RADS) and eventually updated to a document called PI-RADS v2 has attempted to solve these shortcomings. As it stands, PI-RADS v2 currently represents the most up-to-date information on how to acquire, interpret, and report mpMRI of the prostate.

Is contrast enhancement needed for diagnostic prostate MRI?

Prostate Imaging Reporting and Data System version 2 (PI-RADS v2) provides clinical guidelines for multiparametric magnetic resonance imaging (mpMRI) [T2-weighted imaging (T2WI), diffusion-weighted imaging (DWI) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI)] of prostate. However, DCE-MRI seems to show a limited contribution in prostate cancer (PCa) detection and management. In our experience, DCE-MRI, did not show significant change in diagnostic performance in addition to DWI and T2WI [biparametric MRI (bpMRI)] which represent the predominant sequences to detect suspected lesions in peripheral and transitional zone (TZ). In this article we reviewed the role of DCE-MRI also indicating the potential contribute of bpMRI approach (T2WI and DWI) and lesion volume evaluation in the diagnosis and management of suspected PCa.

Multiparametric magnetic resonance imaging of the prostate with computer-aided detection: experienced observer performance study

OBJECTIVES

To compare the performance of experienced readers in detecting prostate cancer (PCa) using likelihood maps generated by a CAD system with that of unassisted interpretation of multiparametric magnetic resonance imaging (mp-MRI).

METHODS

Three experienced radiologists reviewed mp-MRI prostate cases twice. First, readers observed CAD marks on a likelihood map and classified as positive those suspicious for cancer. After 6 weeks, radiologists interpreted mp-MRI examinations unassisted, using their favourite protocol. Sensitivity, specificity, reading time and interobserver variability were compared for the two reading paradigms.

RESULTS

The dataset comprised 89 subjects of whom 35 with at least one significant PCa. Sensitivity was 80.9% (95% CI 72.1-88.0%) and 87.6% (95% CI 79.8-93.2; p = 0.105) for unassisted and CAD paradigm respectively. Sensitivity was higher with CAD for lesions with GS > 6 (91.3% vs 81.2%; p = 0.046) or diameter ≥10 mm (95.0% vs 80.0%; p = 0.006). Specificity was not affected by CAD. The average reading time with CAD was significantly lower (220 s vs 60 s; p < 0.001).

CONCLUSIONS

Experienced readers using likelihood maps generated by a CAD scheme can detect more patients with ≥10 mm PCa lesions than unassisted MRI interpretation; overall reporting time is shorter. To gain more insight into CAD-human interaction, different reading paradigms should be investigated.

KEY POINTS

• With CAD, sensitivity increases in patients with prostate tumours ≥10 mm and/or GS > 6. • CAD significantly reduces reporting time of multiparametric MRI. • When using CAD, a marginal increase of inter-reader agreement was observed.

Detection of Clinically Significant Prostate Cancer: Short Dual-Pulse Sequence versus Standard Multiparametric MR Imaging-A Multireader Study

Purpose To compare the diagnostic performance of a short dual-pulse sequence magnetic resonance (MR) imaging protocol versus a standard six-pulse sequence multiparametric MR imaging protocol for detection of clinically significant prostate cancer. Materials and Methods This HIPAA-compliant study was approved by the regional ethics committee. Between July 2013 and March 2015, 63 patients from a prospectively accrued study population who underwent MR imaging of the prostate including transverse T1-weighted; transverse, coronal, and sagittal T2-weighted; diffusion-weighted; and dynamic contrast material-enhanced MR imaging with a 3-T imager at a single institution were included in this retrospective study. The short MR imaging protocol image set consisted of transverse T2-weighted and diffusion-weighted images only. The standard MR imaging protocol image set contained images from all six pulse sequences. Three expert readers from different institutions assessed the likelihood of prostate cancer on a five-point scale. Diagnostic performance on a quadrant basis was assessed by using areas under the receiver operating characteristic curves, and differences were evaluated by using 83.8% confidence intervals. Intra- and interreader agreement was assessed by using the intraclass correlation coefficient. Transperineal template saturation biopsy served as the standard of reference. Results At histopathologic evaluation, 84 of 252 (33%) quadrants were positive for cancer in 38 of 63 (60%) men. There was no significant difference in detection of tumors larger than or equal to 0.5 mL for any of the readers of the short MR imaging protocol, with areas under the curve in the range of 0.74-0.81 (83.8% confidence interval [CI]: 0.64, 0.89), and for readers of the standard MR imaging protocol, areas under the curve were 0.71-0.77 (83.8% CI: 0.62, 0.86). Ranges for sensitivity were 0.76-0.95 (95% CI: 0.53, 0.99) and 0.76-0.86 (95% CI: 0.53, 0.97) and those for specificity were 0.84-0.90 (95% CI: 0.79, 0.94) and 0.82-0.90 (95% CI: 0.77, 0.94) for the short and standard MR protocols, respectively. Ranges for interreader agreement were 0.48-0.60 (83.8% CI: 0.41, 0.66) and 0.49-0.63 (83.8% CI: 0.42, 0.68) for the short and standard MR imaging protocols. Conclusion For the detection of clinically significant prostate cancer, no difference was found in the diagnostic performance of the short MR imaging protocol consisting of only transverse T2-weighted and diffusion-weighted imaging pulse sequences compared with that of a standard multiparametric MR imaging protocol. ^© RSNA, 2017 Online supplemental material is available for this article.

Enhanced dual-stage correlated diffusion imaging

Prostate cancer is the most common form of cancer and third leading cause of cancer death in Canadian men. Multi-parametric magnetic resonance imaging (mpMRI) has become a powerful non-invasive diagnostic tool for the detection of prostate cancer. Among mpMRI imaging modalities, diffusion-weighed imaging has shown the most promising results in accurate detection of prostate cancer. Introduced recently, correlated diffusion imaging (CDI) is a new form of diffusion imaging which accounts for the joint correlation of diffusion signal attenuation across multiple gradient pulse strengths and timings to improve the separability of cancerous and healthy tissues. Dual-stage CDI (D-CDI) is a newer generation of CDI where in contrast to CDI that does not capture anatomical information, an additional signal mixing stage between the correlated diffusion signal from the first signal mixing stage (CDI) and an auxiliary diffusion signal is performed to incorporate anatomical context. The core of D-CDI is a signal mixing algorithm that combines diffusion images at different b values to construct a single image. In this paper, we enhance the signal mixing algorithm to optimize the contribution of each single b-value image to maximize the separability of cancerous and healthy tissues. We evaluated the enhanced D-CDI (eD-CDI) using area under the ROC curve for datasets of 17 patient cases with confirmed prostate cancer and the results show that eD-CDI outperforms the original D-CDI as well as T2 weighted images and diffusion-weighed images used in the form of apparent diffusion coefficient maps.

The addition of a sagittal image fusion improves the prostate cancer detection in a sensor-based MRI /ultrasound fusion guided targeted biopsy

BACKGROUND

To explore the diagnostic benefit of an additional image fusion of the sagittal plane in addition to the standard axial image fusion, using a sensor-based MRI/US fusion platform.

METHODS

During July 2013 and September 2015, 251 patients with at least one suspicious lesion on mpMRI (rated by PI-RADS) were included into the analysis. All patients underwent MRI/US targeted biopsy (TB) in combination with a 10 core systematic prostate biopsy (SB). All biopsies were performed on a sensor-based fusion system. Group A included 162 men who received TB by an axial MRI/US image fusion. Group B comprised 89 men in whom the TB was performed with an additional sagittal image fusion.

RESULTS

The median age in group A was 67 years (IQR 61-72) and in group B 68 years (IQR 60-71). The median PSA level in group A was 8.10 ng/ml (IQR 6.05-14) and in group B 8.59 ng/ml (IQR 5.65-12.32). In group A the proportion of patients with a suspicious digital rectal examination (DRE) (14 vs. 29%, p = 0.007) and the proportion of primary biopsies (33 vs 46%, p = 0.046) were significantly lower. The rate of PI-RADS 3 lesions were overrepresented in group A compared to group B (19 vs. 9%; p = 0.044). Classified according to PI-RADS 3, 4 and 5, the detection rates of TB were 42, 48, 75% in group A and 25, 74, 90% in group B. The rate of PCa with a Gleason score ≥7 missed by TB was 33% (18 cases) in group A and 9% (5 cases) in group B; p-value 0.072. An explorative multivariate binary logistic regression analysis revealed that PI-RADS, a suspicious DRE and performing an additional sagittal image fusion were significant predictors for PCa detection in TB. 9 PCa were only detected by TB with sagittal fusion (sTB) and sTB identified 10 additional clinically significant PCa (Gleason ≥7).

CONCLUSION

Performing an additional sagittal image fusion besides the standard axial fusion appears to improve the accuracy of the sensor-based MRI/US fusion platform.