What is the most effective tool for detecting prostate cancer using a standard MR scanner?

Applicability of readout-segmented echoplanar diffusion weighted imaging for prostate MRI

To evaluate readout-segmented echoplanar (rsEPI) diffusion weighted imaging (DWI) for multiparametric (mp) magnetic resonance imaging (MRI) of the prostate compared to the established single-shot echoplanar imaging (ssEPI) sequence.One hundred ten consecutive patients with clinical suspicion of prostate cancer underwent mp prostate MRI using both, the ssEPI and the rsEPI DWI sequence. For an objective assessment, delineation of the prostate shape on both DWI sequences was compared to T2-weighted images by measuring organ diameters. Apparent diffusion coefficient (ADC) values, image contrast and contrast-to-noise ratio (CNR) were compared between the 2 sequences on a region-of-interest-based analysis. Diagnostic accuracy for quantitative ADC-values was calculated. Histopathology from MRI/ultrasound fusion-guided biopsy was used as reference standard. For a subjective assessment, 2 independent readers visually assessed image quality of both sequences using Likert-scales.Delineation of the prostate shape was more accurate with rsEPI compared to ssEPI. ADC values in target lesions were not significantly different but significantly higher in the surrounding normal prostatic tissue of the transition zone. CNR was comparable between ssEPI and rsEPI. Sensitivity and specificity were good for both sequences with 84/84% and 82/73% with a Youden selected cut-off of ADC = 0.971*10 mm/s for rsEPI and 1.017*10 mm/s for ssEPI. Anatomic artifacts were significantly less and SNR was lower on rsEPI compared to ssEPI in the subjective analysis.Delineation of the prostate shape was more accurate with rsEPI DWI than with ssEPI DWI with less anatomic artifacts and higher subjective SNR and image quality on rsEPI DW images. Diagnostic ability of quantitative ADC-values was not significantly different between the 2 sequences. Thus, rsEPI DWI might be more suitable for prostate MRI with regard to MRI-guided targeted biopsy and therapy planning.

Optimized b-value selection for the discrimination of prostate cancer grades, including the cribriform pattern, using diffusion weighted imaging

Multiparametric magnetic resonance imaging (MP-MRI), including diffusion-weighted imaging, is commonly used to diagnose prostate cancer. This radiology–pathology study correlates prostate cancer grade and morphology with common b-value combinations for calculating apparent diffusion coefficient (ADC). Thirty-nine patients undergoing radical prostatectomy were recruited for MP-MRI prior to surgery. Diffusion imaging was collected with seven b-values, and ADC was calculated. Excised prostates were sliced in the same orientation as the MRI using 3-D printed slicing jigs. Whole-mount slides were digitized and annotated by a pathologist. Annotated samples were aligned to the MRI, and ADC values were extracted from annotated peripheral zone (PZ) regions. A receiver operating characteristic (ROC) analysis was performed to determine accuracy of tissue type discrimination and optimal ADC b-value combination. ADC significantly discriminates Gleason (G) G4-5 cancer from G3 and other prostate tissue types. The optimal b-values for discriminating high from low-grade and noncancerous tissue in the PZ are 50 and 2000, followed closely by 100 to 2000 and 0 to 2000. Optimal ADC cut-offs are presented for dichotomized discrimination of tissue types according to each b-value combination. Selection of b-values affects the sensitivity and specificity of ADC for discrimination of prostate cancer.

Standardized Reporting of Prostate MRI: Comparison of the Prostate Imaging Reporting and Data System (PI-RADS) Version 1 and Version 2

Introduction

Objective of our study was to determine the agreement between version 1 (v1) and v2 of the Prostate Imaging Reporting and Data System (PI-RADS) for evaluation of multiparametric prostate MRI (mpMRI) and to compare their diagnostic accuracy, their inter-observer agreement and practicability.

Material and Methods

mpMRI including T2-weighted imaging, diffusion-weighted imaging (DWI) and dynamic contrast-enhanced imaging (DCE) of 54 consecutive patients, who subsequently underwent MRI-guided in-bore biopsy were re-analyzed according to PI-RADS v1 and v2 by two independent readers. Diagnostic accuracy for detection of prostate cancer (PCa) was assessed using ROC-curve analysis. Agreement between PI-RADS versions and observers was calculated and the time needed for scoring was determined.

Results

MRI-guided biopsy revealed PCa in 31 patients. Diagnostic accuracy for detection of PCa was equivalent with both PI-RADS versions for reader 1 with sensitivities and specificities of 84%/91% (AUC = 0.91 95%CI[0.8–1]) for PI-RADS v1 and 100%/74% (AUC = 0.92 95% CI[0.8–1]) for PI-RADS v2. Reader 2 achieved similar diagnostic accuracy with sensitivity and specificity of 74%/91% (AUC = 0.88 95%CI[0.8–1]) for PI-RADS v1 and 81%/91% (AUC = 0.91 95%CI[0.8–1]) for PI-RADS v2. Agreement between scores determined with different PI-RADS versions was good (reader 1: κ = 0.62, reader 2: κ = 0.64). Inter-observer agreement was moderate with PI-RADS v2 (κ = 0.56) and fair with v1 (κ = 0.39). The time required for building the PI-RADS score was significantly lower with PI-RADS v2 compared to v1 (24.7±2.3 s vs. 41.9±2.6 s, p<0.001).

Conclusion

Agreement between PI-RADS versions was high and both versions revealed high diagnostic accuracy for detection of PCa. Due to better inter-observer agreement for malignant lesions and less time demand, the new PI-RADS version could be more practicable for clinical routine.

Biparametric versus multiparametric MRI in the diagnosis of prostate cancer

Background

Since multiparametric magnetic resonance imaging (mp-MRI) of the prostate exceeds 30 min, minimizing the evaluation time of significant (Gleason scores > 6) prostate cancer (PCa) would be beneficial. A reduced protocol might be sufficient for the diagnosis.

Purpose

To study whether a short unenhanced biparametric MRI (bp-MRI) matches mp-MRI in detecting significant PCa.

Material and Methods

A total of 204 men (median age, 65 years; mean ± SD, 64.1; range 45–75 years; median serum PSA level, 14 ng/mL; range, 2.2–120 ng/mL; median prostate volume, 60 mL; range, 23–263 mL) fulfilled the criteria for being enrolled. They underwent mp-MRI and prostate biopsy from January through June 2014. Of the included patients, 9.3% underwent prostatectomy, 90.7% had TRUS-bx, and 10.8 had MRI-targeted TRUS-bx. Two radiologists separately assessed the mp-MRI examination (T2-weighted [T2W] imaging, diffusion-weighted imaging [DWI], apparent diffusion coefficient map [ADC-map] and dynamic contrast-enhanced imaging [DCE]). Two months later, the bp-MRI version (T2W imaging, DWI, and ADC-map) was evaluated.

Results

Reader 1: Assessing mp-MRI: 0 false negatives, sensitivity of 1, and specificity 0.04. Assessing bp-MRI: four false negatives, sensitivity of 0.94, and specificity 0.15. Reader 2: Assessing mp-MRI: five false negatives, sensitivity of 0.93, and specificity 0.16. Assessing bp-MRI: three false negatives, sensitivity of 0.96, and specificity 0.15. Intra-reader agreement Cohen’s Kappa (κ) was 0.87 for reader 1 (95% confidence interval [CI], 0.83–0.92) and 0.84 for reader 2 (95% CI 0.78–0.89).

Conclusion

Bp-MRI is as good as mp-MRI at detecting PCa. A large prospective study seems to be strongly warranted.

Index lesion characterization by (11)C-Choline PET/CT and Apparent Diffusion Coefficient parameters at 3 Tesla MRI in primary prostate carcinoma

BACKGROUND

Index lesion characterization is important in the evaluation of primary prostate carcinoma (PPC). The aim of this study was to analyze the contribution of (11) C-Choline PET/CT and the Apparent Diffusion Coefficient maps (ADC) in detecting the Index Lesion and clinically significant tumors in PPC.

METHODS

Twenty-one untreated patients with biopsy-proven PPC and candidates for radical prostatectomy (RP) were prospectively evaluated by means of Ultra-High Definition PET/CT and 3T MRI, which included T2-weighted imaging (T2WI) and ADC maps obtained from diffusion weighted imaging (DWI). Independent experts analyzed all the images separately and were unaware of the pathological data. In each case, the Index lesion was defined as the largest tumor measured on histopathology (Index H). In addition, the largest lesion observed on MRI (Index MRI) and the highest avid (11) C-Choline uptake lesion (Index PET) were obtained. The Gleason scores (GS) of the tumors were determined. PET/CT and ADC map quantitative parameters were also calculated. Measures of correlation among imaging parameters as well as the sensitivity (S), specificity (Sp), negative and positive predictive values (NPV and PPV) for tumor detection were analyzed. All data was validated with the pathological study.

RESULTS

In the morphological study, 139 foci of carcinoma were identified, 47 of which corresponded to clinically significant tumors (>0.5 cm(3)). The remaining foci presented a maximum diameter (dmax ) of 0.1 cm ± SD 0.75 and were not classified as clinically significant. Thirty-two tumors presented a GS (3 + 3), nine GS (3 + 4), and six GS (4 + 3). A total of 21 Index H (dmax = 1.37 cm SD ± 0.61) were identified. The S, Sp, NPV, and PPV for tumor detection with PET were 100%, 70%, 83%, 100%, and for MRI were 46%, 100%, 100%, 54%, respectively. Both Index PET and Index MRI were complementary and identified 95% of the Index H when quantitative criteria were used.

CONCLUSION

In spite of the fact that PET imaging has higher tumor sensitivity than MRI, (11) C-Choline PET and ADC maps have complementary roles in the evaluation of Index Lesion in PPC. Index PET and Index MRI could be complementary targets in the therapeutic planning of PPC.

Multiparametric-MRI in diagnosis of prostate cancer

Multiparametric-magnetic resonance imaging (mp-MRI) has shown promising results in diagnosis, localization, risk stratification and staging of clinically significant prostate cancer. It has also opened up opportunities for focal treatment of prostate cancer. Combinations of T2-weighted imaging, diffusion imaging, perfusion (dynamic contrast-enhanced imaging) and spectroscopic imaging have been used in mp-MRI assessment of prostate cancer, but T2 morphologic assessment and functional assessment by diffusion imaging remains the mainstay for prostate cancer diagnosis on mp-MRI. Because assessment on mp-MRI can be subjective, use of the newly developed standardized reporting Prostate Imaging and Reporting Archiving Data System scoring system and education of specialist radiologists are essential for accurate interpretation. This review focuses on the present status of mp-MRI in prostate cancer and its evolving role in the management of prostate cancer.

3-Tesla magnetic resonance imaging improves the prostate cancer detection rate in transrectral ultrasound-guided biopsy

The detection rate of prostate cancer (PCa) using traditional biopsy guided by transrectal ultrasound (TRUS) is not satisfactory. The aim of this study was to determine the utility of 3-Tesla (3-T) magnetic resonance imaging (MRI) prior to TRUS-guided prostate biopsy and to investigate which subgroup of patients had the most evident improvement in PCa detection rate. A total of 420 patients underwent 3-T MRI examination prior to the first prostate biopsy and the positions of suspicious areas were recorded respectively. TRUS-guided biopsy regimes included systematic 12-core biopsy and targeted biopsy identified by MRI. Patients were divided into subgroups according to their serum prostate-specific antigen (PSA) levels, PSA density (PSAD), prostate volume, TRUS findings and digital rectal examination (DRE) findings. The ability of MRI to improve the cancer detection rate was evaluated. The biopsy positive rate of PCa was 41.2% (173/420), and 41 of the 173 (23.7%) patients were detected only by targeted biopsy in the MRI-suspicious area. Compared with the systematic biopsy, the positive rate was significantly improved by the additional targeted biopsy (P=0.0033). The highest improvement of detection rate was observed in patients with a PSA level of 4–10 ng/ml, PSAD of 0.12–0.20 ng/ml², prostate volume >50 ml, negative TRUS findings and negative DRE findings (P<0.05). Therefore, it is considered that 3-T MRI examination could improve the PCa detection rate on first biopsy, particularly in patients with a PSA level of 4–10 ng/ml, PSAD of 0.12–0.20 ng/ml², prostate volume of >50 ml, negative TRUS findings and negative DRE findings.

Predictive power of the ESUR scoring system for prostate cancer diagnosis verified with targeted MR-guided in-bore biopsy

PURPOSE

This study evaluates the diagnostic value of the ESUR scoring system (PI-RADS) regarding prostate cancer detection using MR-guided in-bore biopsies (IB-GB) as the reference standard.

METHODS

566 lesions in 235 consecutive patients (65.7 ± 7.9 years, PSA 9.9 ± 8.5 ng/ml) with a multiparametric (mp)-MRI (T2WI, DWI, DCE) of the prostate at 3T were scored using the PI-RADS scoring system. PI-RADS single (PSsingle), summed (PSsum), and overall (PSoverall) scores were determined. All lesions were histologically verified by IB-GB.

RESULTS

Lesions with a PSsum below 9 contained no prostate cancer (PCa) with Gleason score (GS) ≥ 4+3=7. A PSsum of 13-15 (PSoverall V) resulted in 87.8% (n=108) in PCa and in 42.3% (n=52) in GS ≥ 4+3=7. Transition zone (TZ) lesions with a PSsum of 13-15 (PSoverall V) resulted in 76.3% (n=36) in PCa and in 26.3% (n=10) in GS ≥ 4+3=7, whereas for peripheral zone (PZ) lesions cancer detection rate at this score was 92.9% (n=79) and 49.4% (n=42) for GS ≥ 4+3=7. Using a threshold of PSsum ≥ 10, sensitivity was 86.0%, and negative predictive value (NPV) was 86.2%. For higher grade PCa sensitivity was 98.6%, and NPV was 99.5%.

CONCLUSION

A PSsum below 9 excluded a higher grade PCa, whereas lesions with a PSsum ≥ 13 (PSoverall V) represented in 88% PCa, and in 42% higher grade PCa. The PSsum or PSoverall demonstrated a better diagnostic value for PZ lesions with higher detection rates for higher grade PCa compared to TZ lesions.

MR-sequences for prostate cancer diagnostics: validation based on the PI-RADS scoring system and targeted MR-guided in-bore biopsy

PURPOSE

This study evaluated the accuracy of MR sequences [T2-, diffusion-weighted, and dynamic contrast-enhanced (T2WI, DWI, and DCE) imaging] at 3T, based on the European Society of Urogenital Radiology (ESUR) scoring system [Prostate Imaging Reporting and Data System (PI-RADS)] using MR-guided in-bore prostate biopsies as reference standard.

METHODS

In 235 consecutive patients [aged 65.7 ± 7.9 years; median prostate-specific antigen (PSA) 8 ng/ml] with multiparametric prostate MRI (mp-MRI), 566 lesions were scored according to PI-RADS. Histology of all lesions was obtained by targeted MR-guided in-bore biopsy.

RESULTS

In 200 lesions, biopsy revealed prostate cancer (PCa). The area under the curve (AUC) for cancer detection was 0.70 (T2WI), 0.80 (DWI), and 0.74 (DCE). A combination of T2WI + DWI, T2WI + DCE, and DWI + DCE achieved an AUC of 0.81, 0.78, and 0.79. A summed PI-RADS score of T2WI + DWI + DCE achieved an AUC of 0.81. For higher grade PCa (primary Gleason pattern ≥ 4), the AUC was 0.85 for T2WI + DWI, 0.84 for T2WI + DCE, 0.86 for DWI + DCE, and 0.87 for T2WI + DWI + DCE. The AUC for T2WI + DWI + DCE for transitional-zone PCa was 0.73, and for the peripheral zone 0.88. Regarding higher-grade PCa, AUC for transitional-zone PCa was 0.88, and for peripheral zone 0.96.

CONCLUSION

The combination of T2WI + DWI + DCE achieved the highest test accuracy, especially in patients with higher-grade PCa. The use of ≤2 MR sequences led to lower AUC in higher-grade and peripheral-zone cancers.

KEY POINTS

• T2WI + DWI + DCE achieved the highest accuracy in patients with higher grade PCa • T2WI + DWI + DCE was more accurate for peripheral- than for transitional-zone PCa • DCE increased PCa detection accuracy in the peripheral zone • DWI was the leading sequence in the transitional zone.