Variability induced by the MR imager in dynamic contrast-enhanced imaging of the prostate.

PURPOSE: To evaluate the variability induced by the imager in discriminating high-grade (Gleason≥7) prostate cancers (HGC) using dynamic contrast-enhanced MRI. MATERIAL AND METHODS: We retrospectively selected 3T MRIs with temporal resolution<10 seconds and comprising T1 mapping from a prospective radiologic-pathologic database of patients treated by prostatectomy. Ktrans, Kep, Ve and Vp were calculated for each lesion seen on MRI using the Weinmann arterial input function (AIF) and three patient-specific AIFs measured in the right and left iliac arteries in pixels in the center of the lumen (psAIF-ST) or manually selected by two independent readers (psAIF-R1 and psAIF-R2). RESULTS: A total of 43 patients (mean age, 63.6±4.9 [SD]; range: 48-72 years) with 100 lesions on MRI (55 HGC) were selected. MRIs were performed on imager A (22 patients, 49 lesions) or B (21 patients, 51 lesions) from two different manufacturers. Using the Weinmann AIF, Kep (P=0.005), Ve (P=0.04) and Vp (P=0.01) significantly discriminated HCG. After adjusting on tissue classes, the imager significantly influenced the values of Kep (P=0.049) and Ve (P=0.007). Using patient-specific AIFs, Vp with psAIF-ST (P=0.008) and psAIF-R2 (P=0.04), and Kep with psAIF-R1 (P=0.03) significantly discriminated HGC. After adjusting on tissue classes, types of patient-specific AIF and side of measurement, the imager significantly influenced the values of Ktrans (P=0.0002), Ve (P=0.0072) and Vp (P=0.0003). For all AIFs, the diagnostic value of pharmacokinetic parameters remained unchanged after adjustment on the imager, with stable odds ratios. CONCLUSION: The imager induced variability in the absolute values of pharmacokinetic parameters but did not change their diagnostic performance.

Detection of locally radio-recurrent prostate cancer at multiparametric MRI: Can dynamic contrast-enhanced imaging be omitted?

OBJECTIVE: The goal of this study was to assess the added value of dynamic contrast-enhanced (DCE) imaging in detecting locally radio-recurrent prostate cancer using multiparametric magnetic resonance imaging (mpMRI) at 3Tesla (T). MATERIALS AND METHODS: We retrospectively analyzed 45 patients with rising prostate-specific antigen level after prostate radiotherapy who underwent mpMRI [T2-weighted (T2w), diffusion-weighted (Dw) and DCE imaging] at 3T before prostate biopsy. Four readers assigned a 5-level Likert score of cancer likelihood in 8 prostate sectors (6 sextants, 2 seminal vesicles) on T2w+Dw and T2w+Dw+DCE images. Biopsy results were used as the standard of reference. RESULTS: T2w+Dw and T2w+Dw+DCE imaging had similar areas under the receiver operating characteristic curves on per-sector (0.87-0.89 vs. 0.87-0.89; P=0.19-0.78) and per-lobe (0.82-0.94 vs. 0.80-0.91; P=0.21-0.84) analysis. Using a Likert score≥2/5 for diagnosis threshold, T2w+Dw+DCE imaging showed non-significantly higher sensitivities on per-sector (0.56-0.72 vs. 0.52-0.73, P=0.34-0.69) and per-lobe (0.80-0.90 vs. 0.73-0.88; P=0.63-0.99) analysis. It also showed non-significantly lower specificities on per-sector (0.74-0.89 vs. 0.82-0.89; P=0.09-0.99) and per-lobe (0.48-0.81 vs. 0.61-0.84; P=0.10-0.99) analysis. Weighted kappa values were respectively 0.57-0.70 and 0.55-0.66 for T2w+Dw and T2w+Dw+DCE imaging at the sector level, and 0.66-0.83 and 0.58-0.85 at the lobe level. CONCLUSION: The use of DCE MR imaging tends to increase sensitivity and decrease specificity for all readers, but the differences are not significant.

Characterization of prostate cancer using T2 mapping at 3T: a multi-scanner study.

RATIONALE AND OBJECTIVES: To assess the prostate T2 value as a predictor of malignancy on two different 3T scanners. PATIENTS AND METHODS: Eighty-three pre-prostatectomy multiparametric MRIs were retrospectively evaluated [67 obtained on a General Electric MRI (scanner 1) and 16 on a Philips MRI (scanner 2)]. After correlation with prostatectomy specimens, readers measured the T2 value of regions-of-interest categorized as "cancers", "false positive lesions", or "normal tissue". RESULTS: On scanner 1, in PZ, cancers had significantly lower T2 values than false positive lesions (P=0.02) and normal tissue (P=2×10(-9)). Gleason≥6 cancers had similar T2 values than false positive lesions and significantly higher T2 values than Gleason≥7 cancers (P=0.009). T2 values corresponding to a 25% and 75% risk of Gleason≥7 malignancy were respectively 132 ms (95% CI: 129-135 ms) and 77 ms (95% CI: 74-81 ms). In TZ, cancers had significantly lower T2 values than normal tissue (P=0.008), but not than false positive findings. Mean T2 values measured on scanner 2 were not significantly different than those measured on scanner 1 for all tissue classes. CONCLUSION: All tested tissue classes had similar mean T2 values on both scanners. In PZ, the T2 value was a significant predictor of Gleason≥7 cancers.

Value of prostate multiparametric magnetic resonance imaging for predicting biopsy results in first or repeat biopsy.

AIM: To assess multiparametric magnetic resonance imaging (mp-MRI) in predicting prostate biopsy results. MATERIALS AND METHODS: Patients who underwent mp-MRI prior to prostate biopsy were prospectively included. The prostate was subdivided into 14 sectors and mp-MRI findings assessed using a five-level subjective suspicion score (SSS). Biopsy included targeted samples of abnormal sectors and systematic samples of normal peripheral zone sectors. RESULTS: Two hundred and eighty-eight patients were included [153 biopsy naïve, 135 with negative (n = 51) or positive (n = 84) prior biopsy]. Biopsy was positive in 168 patients. mp-MRI area under the receiver operating characteristic (ROC) curve (AUC) was 69.1% (95% CI: 67.1-70.9%), 72.5% (95% CI: 69.5-76%), and 73.8% (95% CI: 68.3-79.3%) at per sector, per lobe, and per patient analysis, respectively. At the per sector level, the AUC was significantly larger if detection was limited to cancers with a Gleason score of ≥7 (72.6%; 95% CI: 69.8-75.8%; p < 0.01) or ≥8 (87.1%; 95% CI: 78.3-95.7%; p < 0.01). mp-MRI performance was significantly influenced by prostate volume (p = 0.02), the presence of a concordant hypoechoic area (p < 0.001), but not by prostate-specific antigen (PSA) value, status of prior biopsy, or radiologists' experience. SSS was significantly associated with the Gleason score in true-positive lobes and patients (p < 0.0001). Using a SSS threshold of ≥3, cancer was missed in 13/102 lobes and 4/72 patients with cancers of Gleason score ≥7. CONCLUSION: mp-MRI provides a good detection of cancers with a Gleason score of ≥7 in candidates suitable for prostate biopsy.

Differentiation of transitional zone prostate cancer from benign hyperplasia nodules: evaluation of discriminant criteria at multiparametric MRI.

AIM: To assess topographical and magnetic resonance imaging (MRI) features in characterizing prostate transitional zone (TZ) nodules. MATERIALS AND METHODS: Two radiologists evaluated all TZ nodules visible at multiparametric MRI in 52 consecutive patients who underwent radical prostatectomy. The radiologists assessed topographical (anteroposterior and superior-inferior location, crossing of the sagittal midline) and T2-weighted (shape, presence and distinctness of capsule, distinctness of contours, presence of cysts) features, the apparent diffusion coefficient (ADC), and eight semi-quantitative and quantitative enhancement parameters derived from dynamic contrast-enhanced (DCE) imaging. The nature of the nodules was assessed using prostatectomy specimens. Five statistical methods taking into account multiple testing were used. RESULTS: One hundred and thirty-seven nodules (117 benign, 20 malignant) were evaluated. Mean ADC, all topographical, and all T2-weighted features were significant predictors of malignancy according to at least four out of the five statistical methods. Particularly, 20/20 and 18/20 cancers involved the anterior and apical third of the TZ, respectively. None of the enhancement parameters was significantly different between cancers and benign nodules. By assessing the presence of cysts, the nodules' capsule, and their anteroposterior and superior-inferior location, 111/117 benign nodules were correctly diagnosed, without misclassifying any cancer. CONCLUSION: Topographical, T2-weighted, and diffusion-weighted features can be used to characterize TZ nodules. DCE imaging does not seem to provide additional information.