The development and validation of magnetic resonance elastography for fibrosis staging in primary sclerosing cholangitis.

OBJECTIVES: To develop and internally validate MR elastography (MRE) quantified liver stiffness (LS) cut-off values for distinguishing early/moderate fibrosis from cirrhosis in primary sclerosing cholangitis (PSC) against non-invasive fibrosis test of vibration-controlled transient elastography (VCTE). METHODS: Sixty-seven patients were enrolled prospectively at a tertiary care centre to undergo MRE and VCTE. MRE-quantified LS was calculated using three region-of-interest (ROI) methods: Trace, Average and Maximum. Each ROI method was compared with the reference standard of VCTE. Internal validation was performed with bootstrapping. Univariable and multivariable linear regression determined independent predictors for MRE-quantified LS and final Mayo Risk Score (MRS). RESULTS: MRE-quantified LS by Trace ROI method had the highest sensitivity [87.5%; 95% confidence interval (CI), 66.0-96.8] and specificity (96.1%; 95%CI, 89.6-99.0) for distinguishing cirrhosis; and was the strongest predictor of final MRS (ß, 0.44; 95% CI, 0.27-0.61). Alkaline phosphatase twice the normal upper limit (ß, 1.55; 95% CI, 0.95-2.17), abnormal bilirubin (ß, 1.27; 95% CI, 0.41-2.14) and thrombocytopaenia (ß, 0.79; 95% CI, 0.12-1.46) were independent predictors of LS. CONCLUSIONS: MRE has a higher correlation with MRS than VCTE; and though MRE is possibly influenced by severe cholestasis and portal hypertension, MRE-quantified LS is an independent predictor of worse MRS. KEY POINTS: • MRE is valid and reliable in assessing cirrhosis in PSC, and MRE-quantified Liver stiffness (LS) score was the strongest predictor of final Mayo Risk Score (MRS). • Trace ROI performs best for distinguishing moderate fibrosis from cirrhosis and has the highest correlation with Mayo Risk Score (MRS). • Cholestasis, hyperbilirubinaemia and portal hypertension may influence MRE LS score.

Diagnostic Accuracy of Attenuation Difference and Iodine Concentration Thresholds at Rapid-Kilovoltage-Switching Dual-Energy CT for Detection of Enhancement in Renal Masses.

OBJECTIVE. The objective of our study was to evaluate iodine concentration and attenuation change in Hounsfield unit (ΔHU) thresholds to diagnose enhancement in renal masses at rapid-kilovoltage-switching dual-energy CT (DECT). MATERIALS AND METHODS. We evaluated 30 consecutive histologically confirmed solid renal masses (including nine papillary renal cell carcinomas [RCCs]) and 27 benign cysts (17 simple and 10 hemorrhagic or proteinaceous cysts) with DECT December 2016 and May 2018. A blinded radiologist measured iodine concentration (in milligrams per milliliter) and ΔHU (attenuation on enhanced CT - attenuation on unenhanced CT) using 70-keV corticomedullary (CM) phase virtual monochromatic and 120-kVp nephrographic (NG) phase images. The accuracies of previously described enhancement thresholds were compared by ROC curve analysis. RESULTS. An iodine concentration of ≥ 2.0 mg/mL and an iodine concentration of ≥ 1.2 mg/mL achieved sensitivity, specificity, and the area under the ROC curve (AUC) of 73.3%, 100.0%, and 0.87 and 86.7%, 100.0%, and 0.93, respectively. On 70-keV CM phase images, ΔHU ≥ 20 HU and ΔHU ≥ 15 HU yielded sensitivity, specificity, and AUC of 80.0%, 100.0%, and 0.90 and 90.0%, 100.0%, and 0.95, respectively. The numbers of incorrectly classified papillary RCCs were as follows: iodine concentration of ≥ 2.0 mg/mL, 77.8% (7/9; range, 0.7-1.6 mg/mL); iodine concentration of ≥ 1.2 mg/mL, 44.4% (4/9; range, 0.7-0.9 mg/mL); ΔHU ≥ 20 HU on 70-keV CM phase images, 66.7% (6/9; range, 4-17 HU); and ΔHU ≥ 15 HU on 70-keV DECT images, 33.3% (3/9; 4-12 HU). No cyst pseudoenhancement occurred on DECT. For 120-kVp NG phase DECT, ΔHU ≥ 20 HU and ΔHU ≥ 15 HU yielded sensitivity, specificity, and AUC of 93.3%, 96.3%, and 0.95 and 100.0%, 88.9%, and 0.94, respectively. With ΔHU ≥ 20 HU, 22.2% (2/9) (range, 15-18 HU) of papillary RCCs were misclassified and there was one pseudoenhancing cyst. With ΔHU ≥ 15 HU, no papillary RCCs were misclassified but 11.1% (3/27) of cysts showed pseudoenhancement. Only an iodine concentration of ≥ 2.0 mg/mL showed significantly lower accuracy than other measures (p = 0.031-0.045). CONCLUSION. DECT applied in the CM phase performed best using an iodine concentration of ≥ 1.2 mg/mL or a 70-keV ΔHU ≥ 15 HU; these parameters improved sensitivity for the detection of enhancement in renal masses without instances of cyst pseudoenhancement.

Prediction of the histopathologic findings of intrahepatic cholangiocarcinoma: qualitative and quantitative assessment of diffusion-weighted imaging.

OBJECTIVE: To correlate qualitative and quantitative diffusion weighted imaging (DWI) characteristics of intrahepatic cholangiocarcinoma (ICC) with histopathologic tumour grade and fibrosis content. METHODS: Fifty-one patients (21M/30F; mean age 61y) with ICC and MRI including DWI were included in this IRB-approved multicentre retrospective study. Qualitative tumour features were assessed. Tumour apparent diffusion coefficient (ADC) mean, minimum, and normalized (nADCliver) values were computed. Tumour grade [well(G1), moderately(G2), or poorly differentiated(G3)] and tumour fibrosis content [minimal(1), moderate(2), or abundant(3)] were categorized pathologically. Imaging findings and ADC values were compared with pathologic measures. Utility of ADC values for predicting tumour grade was assessed using ROC analysis. RESULTS: 51 ICCs (mean size 6.5±1.1 cm) were assessed. 33/51(64%) of ICCs demonstrated diffuse hyperintensity and 15/51(29%) demonstrated target appearance on DWI. Infiltrative morphology (p=0.02) and tumour size (p=0.04) were associated with G3. ADCmean and nADCmean of G3 (1.32±0.47x10-3 mm2/sec and 0.97±0.95) were lower than G1+G2 (1.57±0.39x10-3 mm2/sec and 1.24±0.49; p=0.03 and p=0.04). ADCmean and nADCmean were inversely correlated with tumour grade (p<0.025). No correlation was found between ADC and tumour fibrosis content. AUROC, sensitivity and specificity of nADCmean for G3 versus G1+G2 were 0.71, 89.5% and 55.5%. CONCLUSION: ADC quantification has reasonable accuracy for predicting ICC grade. KEY POINTS: • ADC quantification was useful for predicting ICC tumour grade. • Infiltrative tumour morphology and size were associated with poorly differentiated ICCs. • ADC values depended more on ICC tumour grade than fibrosis content. • Ability to predict ICC tumour grade non-invasively could impact patient management.

Attenuation and Degree of Enhancement With Conventional 120-kVp Polychromatic CT and 70-keV Monochromatic Rapid Kilovoltage-Switching Dual-Energy CT in Cystic and Solid Renal Masses.

OBJECTIVE: The purpose of this study was to compare attenuation values (in Hounsfield units) and degree of enhancement (attenuation change) in renal masses using 120-kVp polychromatic (conventional) CT and 70-keV monochromatic dual-energy CT (DECT). MATERIALS AND METHODS: Twenty-two patients with 39 renal masses (24 Bosniak category I and II cysts and 15 solid masses under active surveillance) underwent conventional CT (120-kVp unenhanced and contrast-enhanced CT) and rapid kilovoltage-switching DECT (120-kVp unenhanced CT and 70-keV contrast-enhanced CT). The mean (± SD) time between scans was 648 ± 943 days. A radiologist measured attenuation on matched image sets coregistered between examinations. Absolute attenuation and attenuation change were compared using independent t tests, Pearson correlation, and Bland-Altman analysis. RESULTS: There was no difference in attenuation on 120-kVp versus 70-keV contrast-enhanced CT images for cysts (9.5 ± 5.5 HU [range, -2 to 20 HU] vs 10.1 ± 4.6 HU [range, -2 to 16 HU]; p = 0.33) and solid masses (110.1 ± 72.9 HU [range, 35-267 HU] vs 119.1 ± 73.7 HU [range, 33-265 HU]; p = 0.04). There also was no difference in attenuation change for 120-kVp contrast-enhanced CT minus 120-kVp unenhanced CT (cysts, 3.5 ± 3.9 HU [range, -2 to 13 HU]; solid masses, 80.7 ± 73.3 HU [range, 9-227 HU]; p = 0.45) or for 70-keV contrast-enhanced CT minus 120-kVp unenhanced CT (cysts, 4.3 ± 4.1 HU [range, -3 to 12 HU]; solid masses, 89.8 ± 74.1 HU [range, 7-226 HU]; p = 0.04). The correlation was strong to almost perfect (ß = 0.83-0.98) with substantial agreement. There was no difference in attenuation of cysts and solid masses comparing 120-kVp acquisitions acquired at different time points (p = 0.20-0.92). The correlation was strong to almost perfect (ß = 0.72-0.95) with substantial agreement. CONCLUSION: There are no differences in absolute attenuation or degree of enhancement comparing 70-keV monochromatic CT to conventional 120-kVp CT in renal cysts and solid masses.

ADC Metrics From Multiparametric MRI: Histologic Downgrading of Gleason Score 9 or 10 Prostate Cancers Diagnosed at Nontargeted Transrectal Ultrasound-Guided Biopsy.

OBJECTIVE: The purpose of this study was to evaluate quantitative apparent diffusion coefficient (ADC) metrics for the downgrading of Gleason score (GS) 9 or 10 prostate cancer (PCa) diagnosed by means of nontargeted transrectal ultrasound-guided biopsy. MATERIALS AND METHODS: Between 2012 and 2015, 30 men with a diagnosis of GS 9 or 10 PCa at nontargeted transrectal ultrasound-guided biopsy underwent 3-T multiparametric MRI before radical prostatectomy (RP). Two radiologists blinded to the histopathologic results independently assessed multiparametric MR images using Prostate Imaging Reporting and Data System (PI-RADS) version 2. Whole-lesion ADC mean, centile, and texture features were extracted from coregistered ADC and RP maps by a third blinded radiologist. Comparisons were performed by chi-square, multivariable logistic regression, and ROC analysis. RESULTS: Tumors were downgraded to intermediate risk (GS 4 + 3 [n = 7] and GS 3 + 4 [n = 2]) PCa in 30.0% (9/30) of men after RP. There were no statistically significant differences between groups with respect to age (p = 0.028), prostate-specific antigen level (p = 0.018), or clinical stage (p = 0.021). PI-RADS version 2 scores did not differ between groups (p = 0.035, p = 0.091) with moderate agreement (κ = 0.48). There were no differences in mean or centile ADC (p = 0.269-0.634) between the two groups. ADC entropy was significantly lower in downgraded tumors (5.542 ± 0.721 [SD] vs 8.089 ± 1.237, p < 0.001) with no difference in kurtosis or skewness (p = 0.133, p = 0.296). The ROC AUC for the diagnosis of downgrading was 0.93 (95% CI, 0.84-1.00) with sensitivity of 85.7% and specificity of 88.9% when entropy was less than 6.31. CONCLUSION: ADC entropy was significantly lower in GS 9 and 10 tumors diagnosed by means of nontargeted transrectal ultrasound-guided biopsy that were eventually downgraded to intermediate risk (GS 7) after RP. ADC texture analysis may be useful for further risk stratification of PCa diagnosed at biopsy.

Pharmacokinetic modeling of dynamic contrast-enhanced (DCE)-MRI in PI-RADS category 3 peripheral zone lesions: preliminary study evaluating DCE-MRI as an imaging biomarker for detection of clinically significant prostate cancers.

PURPOSE: To determine if pharmacokinetic modeling of DCE-MRI can diagnose CS-PCa in PI-RADS category 3 PZ lesions with subjective negative DCE-MRI. MATERIALS AND METHODS: In the present IRB approved, bi-institutional, retrospective, case-control study, we identified 73 men with 73 PZ PI-RADS version 2.1 category 3 lesions with MRI-directed-TRUS-guided targeted biopsy yielding: 12 PZ CS-PCa (ISUP Grade Group 2; N = 9, ISUP 3; N = 3), 27 ISUP 1 PCa and 34 benign lesions. An expert blinded radiologist segmented lesions on ADC and DCE images; segmentations were overlayed onto pharmacokinetic DCE-MRI maps. Mean values were compared between groups using univariate analysis. Diagnostic accuracy was assessed by ROC. RESULTS: There were no differences in age, PSA, PSAD or clinical stage between groups (p = 0.265-0.645). Mean and 10th percentile ADC did not differ comparing CS-PCa to ISUP 1 PCa and benign lesions (p = 0.376 and 0.598) but was lower comparing ISUP ≥ 1 PCa to benign lesions (p < 0.001). Mean Ktrans (p = 0.003), Ve (p = 0.003) but not Kep (p = 0.387) were higher in CS-PCa compared to ISUP 1 PCa and benign lesions. There were no differences in DCE-MRI metrics comparing ISUP ≥ 1 PCa and benign lesions (p > 0.05). AUC for diagnosis of CS-PCa using Ktrans and Ve were: 0.69 (95% CI 0.52-0.87) and 0.69 (0.49-0.88). CONCLUSION: Pharmacokinetic modeling of DCE-MRI parameters in PI-RADS category 3 lesions with subjectively negative DCE-MRI show significant differences comparing CS-PCa to ISUP 1 PCa and benign lesions, in this study outperforming ADC. Studies are required to further evaluate these parameters to determine which patients should undergo targeted biopsy for PI-RADS 3 lesions.