Added value of diffusion-weighted imaging to MR cholangiopancreatography for the diagnosis of bile duct dilatations.

PURPOSE: To investigate the added value of diffusion-weighted imaging (DWI) when used with conventional T2-weighted magnetic resonance (MR) imaging (T2WI) and MR cholangiopancreatography (MRCP) for diagnosing bile duct dilatations. METHODS: Our institutional review board approved this retrospective study protocol and waived the informed consent requirement. The study included 151 consecutive patients (70 men, 81 women) with intra- and/or extra-hepatic bile duct dilatation examined using MR imaging. Two radiologists independently and randomly reviewed 3 image sets (A: MRCP and T2WI; B: DWI; and C: combined T2WI, MRCP, and DWI) at different occasions to differentiate between malignancy, biliary lithiasis, and benign dilatation. The sensitivity, specificity, and diagnostic accuracy of these imaging sets were calculated and compared. RESULTS: For both readers, combined T2WI, MRCP, and DWI exhibited significantly higher sensitivity and diagnostic accuracy for malignant dilatation, compared with conventional T2WI and MRCP (P < 0.01 for both readers). However, DWI did not significantly affect the sensitivity and diagnostic accuracy for biliary lithiasis or benign dilatation. CONCLUSION: The addition of DWI to T2WI and MRCP sequences yields significantly higher sensitivity and diagnostic accuracy when examining bile duct dilatations, particularly malignant dilatations.

Diagnostic Performance of Split-Bolus Portal Venous Phase Dual-Energy CT Urography in Patients With Hematuria.

OBJECTIVE: The purpose of this study is to evaluate the diagnostic performance of split-bolus portal venous phase dual-energy CT (DECT) urography in patients with hematuria. MATERIALS AND METHODS: True unenhanced and split-bolus portal venous phase contrast-enhanced weighted-average images were obtained in 171 patients with hematuria. Virtual unenhanced and iodine-overlay images were reconstructed from contrast-enhanced 80-kVp and tin-filtered 140-kVp scans. Images were independently reviewed by two radiologists who were blinded to the final diagnoses in two separate reading sessions: virtual unenhanced and iodine-overlay images (single phase) in the first session and true unenhanced and contrast-enhanced weighted-average images (dual phase) in the second session (mean ± SD, 52 ± 8 days later). Sensitivity, specificity, and accuracy of mass detection were calculated from the data of both reading sessions. The number of calculi detected on virtual unenhanced images was compared with the number detected on true unenhanced images. The difference in radiation dose between the single- and dual-phase protocols was calculated. The statistical significance was determined by ANOVA. RESULTS: The sensitivity, specificity, and accuracy were 98.7%, 98.9%, and 98.8%, respectively, for the single-phase approach to malignant mass detection and 98.7%, 97.9%, and 98.3%, respectively, for the dual-phase approach (p > 0.05 for all comparisons). The overall sensitivity of stone detection was 86.7% (39/45) for virtual unenhanced images. Omitting the unenhanced scan reduced the mean radiation dose from 15.4 to 6.7 mSv. CONCLUSION: The diagnostic performance of both the single- and dual-phase approaches of portal venous phase split-bolus DECT urography is equally good in patients with hematuria, and single-phase acquisition has the added benefit of radiation reduction.

Utility of the iodine overlay technique and virtual nonenhanced images for the preoperative T staging of colorectal cancer by dual-energy CT with tin filter technology.

OBJECTIVES: To evaluate the diagnostic accuracy and the potential radiation dose reduction of dual-energy CT (DECT) for tumor (T) staging of colorectal cancer (CRC) using iodine overlay (IO) and virtual nonenhanced (VNE) images. MATERIALS AND METHODS: This retrospective study included 103 consecutive patients who underwent nonenhanced CT and enhanced DECT for preoperative CRC staging. Enhanced weighted-average (WA), IO and VNE images were reconstructed from enhanced 80 kVp and Sn140 kVp scans. Two radiologists assessed image qualities of the true nonenhanced (TNE) and VNE images. For T-staging, another two radiologists independently interpreted all scans in two separate reading sessions: in the first session, only images derived from the single phase DECT acquisition (IO and VNE images) were read. In the second reading session after 30 to 50 (average:42) days, the same assessment was again performed with the TNE and enhanced WA images thereby simulating conventional dual-phase single-energy CT. The tumor node metastasis (TNM) system was used for staging with histopathologic reports as gold standard. Analysis of variance was used for statistical analysis. RESULTS: The signal-to-noise ratios (SNRs) of the tumors and normal reference tissues showed significant correlation between the TNE and VNE images (P<0.01). The mean iodine overlay value (48.4 HU±12.2) and enhancement (49.4 HU±11.8) value of CRCs had no significant difference (P = 0.52).The mean image noise on TNE (5.0±1.1) and VNE (5.3±1.1) images were similar (P = 0.07). The quantitative qualities of the VNE images were mildly inferior to the TNE images. Overall accuracy of T-stage CRC when using single-phase acquisition was slightly better than the dual-phase acquisition (90.3% vs 87.4%) (P = 0.51). The mean dose of the single-phase DECT acquisition was 6.2 mSv comparing with 14.3 mSv of dual-phase. CONCLUSION: Single-phase DECT using IO and VNE images yields a high accuracy in T-staging of CRCs. Thereby, the radiation exposure of the patients can be reduced.