Dual-layer spectral detector computed tomography versus magnetic resonance cholangiopancreatography for biliary stones.

OBJECTIVE: Dual-layer spectral detector computed tomography (DLCT) can detect noncalcified biliary stones. The diagnostic ability of DLCT for detecting biliary stones may be comparable to that of magnetic resonance cholangiopancreatography (MRCP). This study seeks to compare the diagnostic ability for biliary stones between these two imaging modalities. METHODS: This retrospective study included 102 cases with a diagnosis of biliary stones including gallstones (n = 66) and common bile duct (CBD) stones (n = 25) or spontaneously passing CBD stones (n = 11). The reference standard used was operative findings, endoscopic retrograde cholangiopancreatography or follow-up over 6 months. In DLCT, 120-kVp images, 40-keV virtual monoenergetic images and material decomposition images were created. We compared the diagnostic ability of DLCT and MRCP for biliary stones using the McNemar's test. RESULTS: The sensitivity and specificity of DLCT versus MRCP for biliary stones were 91.2% versus 95.6% and 90.9% versus 90.9%. Thus, the sensitivity and specificity were not significantly different (P = 0.25 and P = 1.0). Although in small stones (<9 mm) the sensitivity of calcified stones was not different between DLCT and MRCP (100% versus 92.5%), the sensitivity of noncalcified stones in DLCT was lower than that in MRCP (38.5% versus 100%). CONCLUSION: The diagnostic ability of biliary stones in DLCT appears comparable to that of MRCP in overall cases. However, detecting noncalcified stones less than 9 mm in size is limited in DLCT.

Reduced iodinated contrast media for abdominal imaging by dual-layer spectral detector computed tomography for patients with kidney disease.

Contrast-enhanced computed tomography using iodinated contrast media is useful for diagnosis of gastrointestinal diseases. However, contrast-induced nephropathy remains problematic for kidney diseases patients. Although current guidelines recommended the use of a minimal dose of contrast media necessary to obtain adequate images for diagnosis, obtaining adequate images with sufficient contrast enhancement is difficult with conventional computed tomography using reduced contrast media. Dual-layer spectral detector computed tomography enables the simultaneous acquisition of low- and high-energy data and the reconstruction of virtual monochromatic images ranging from 40 to 200 keV, retrospectively. Low-energy virtual monochromatic images can enhance the contrast of images, thereby facilitating reduced contrast media. In case 1, abdominal computed tomography angiography at 50 keV using 40% of the conventional dose of contrast media revealed the artery that was the source of diverticular bleeding in the ascending colon. In case 2, ischemia of the transverse colon was diagnosed by contrast-enhanced computed tomography and iodine-selective imaging using 40% of the conventional dose of contrast media. In case 3, advanced esophagogastric junctional cancer was staged and preoperative abdominal computed tomography angiography could be obtained with 30% of the conventional dose of contrast media. However, the texture of virtual monochromatic images may be a limitation at low energy.

Usefulness and limitations of dual-layer spectral detector computed tomography for diagnosing biliary stones not detected by conventional computed tomography: a report of three cases.

Computed tomography (CT) is useful for diagnosing biliary stones. However, the presence of stones not detected by conventional CT, such as iso-dense stones with CT numbers similar to those of bile or small stones, is problematic. Although conventional CT provides only 120-kVp images corresponding to CT numbers at approximately 70 keV, dual-layer spectral detector CT uses one X-ray source and dual-layer detectors to collect low- and high-energy data simultaneously; retrospective spectral analysis, including virtual monochromatic images with photon energy levels of 40-200 keV, material decomposition images, and spectral curves, can be immediately performed on demand. This technique can immediately discriminate between materials with similar conventional CT numbers. Therefore, prompt and accurate diagnosis of iso-dense stones can be performed. In two out of three of our cases, iso-dense stones were detected in virtual monochromatic images at 40 keV, but in the remaining case a common 4-mm bile duct stone was not detected on 120-kVp and 40-keV images by retrospective spectral analysis. However, this stone was detected by magnetic resonance cholangiopancreatography. Retrospective spectral analysis using dual-layer spectral detector CT was useful for prompt and accurate diagnosis of iso-dense stones, but detection of <5-mm stones may be a limitation of this technique and of conventional CT.

Triage of low-risk prostate cancer patients with PSA levels 10 ng/ml or less: comparison of apparent diffusion coefficient value and transrectal ultrasound-guided target biopsy.

OBJECTIVE: The purpose of our study was to identify low-risk prostate cancer on the basis of the D'Amico clinical risk score in patients with prostate-specific antigen (PSA) levels 10 ng/mL or less who had undergone radical prostatectomy by comparing apparent diffusion coefficient (ADC) with transrectal ultrasound (TRUS)-guided target biopsy. MATERIALS AND METHODS: In the preliminary study, we used receiver operating characteristic (ROC) analysis and determined the cutoff ADC to identify prostate cancer with a Gleason score of 6 or less for 117 patients. In the primary study, we assessed the combination of routine MRI (T2-weighted and diffusion-weighted imaging) plus the cutoff ADC value ("method A") to identify low-risk prostate cancer for another 89 patients. Their diagnostic value was compared with that of routine MRI combined with the Gleason score obtained from TRUS-guided target biopsies ("method B"). RESULTS: The preliminary study showed that a mean ADC of 1.04 × 10(-3) mm(2)/s was the best cutoff. In the primary study, accuracy was statistically higher with method A for each reader (p = 0.041). CONCLUSION: In patients with PSA levels 10 ng/mL or less, the combination of MRI findings plus the cutoff ADC is significantly more accurate for the identification of low-risk prostate cancer than is the combination of MRI followed by TRUS-guided target biopsy.

Three-dimensional computed tomographic angiography of the liver for planning hepatic surgery: effect of low tube voltage and the iterative reconstruction algorithm on image quality.

OBJECTIVE: The aim of this study was to evaluate the effect of a low tube voltage technique and hybrid iterative reconstruction (HIR) on image quality at 3-dimensional computed tomographic angiography (3D-CTA) of the liver. METHODS: Before hepatic surgery, we randomly assigned 60 patients (17 women, 43 men; mean ± SD age, 68.9 ± 10.1 years) who had undergone 3D-CTA to 1 of 2 protocols; 30 patients underwent scanning under the conventional 120-kilovolt (peak) protocol with filtered back projection (P1); and 30 patients, under an 80-kilovolt (peak) protocol with HIR (P2). The estimated effective radiation dose, computed tomographic attenuation, image noise, contrast-to-noise ratio, and figure of merit were calculated, and the visual image quality of 3D-CTA was scored on a 4-point scale. RESULTS: The mean effective radiation dose was significantly lower under P2 than P1 (4.8 ± 1.2 vs 7.2 ± 1.5 mSv, P < 0.01). P1 and P2 did not significantly differ with respect to the image noise (10.5 ± 2.3 vs 9.9 ± 1.6 Hounsfield units; P = 0.46). Computed tomographic attenuation, contrast-to-noise ratio, figure of merit, and the visual scores for image quality were higher under P2 than P1 (P < 0.01). CONCLUSIONS: The use of low tube voltage and HIR can yield significantly improved image quality at 3D-CTA of the liver.

Preoperative evaluation of the cystic duct for laparoscopic cholecystectomy: comparison of navigator-gated prospective acquisition correction- and conventional respiratory-triggered techniques at free-breathing 3D MR cholangiopancreatography.

OBJECTIVE: To evaluate the quality of magnetic resonance cholangiopancreatography (MRCP) images obtained with a three-dimensional navigator-gated (NG) technique and compare findings with conventional respiratory-triggered (RT) images in pre-laparoscopic cholecystectomy patients. METHODS: Turbo-spin-echo (TSE) RT-MRCP (average 242 s) and balanced turbo-field-echo (bTFE) NG-MRCP (average 263 s) were acquired at 1.5-T MRI for 49 pre-laparoscopic cholecystectomy patients. Two radiologists independently assessed image quality, visibility of anatomical structures, common bile duct (CBD) stones, and signal-to-noise ratios (SNRs). Interobserver agreement was also evaluated. RESULTS: The anatomical details of the cystic duct were clearly demonstrated in 33 (67.3 %, reader A) and 35 (71.4 %, reader B) patients on RT-MRCP, and in 45 (91.8 %) and 44 (89.7 %) patients on NG-MRCP. On NG-MRCP, visualisation of the cystic duct (3.22/3.12), its origin (3.57/3.55), and the gallbladder(3.61/3.59) was statistically better than on RT-MRCP (2.90/2.78, 3.29/3.12, 2.98/2.88, respectively). The overall image quality was statistically better on NG-MRCP than RT-MRCP. Each technique identified the presence of CBD stones in all affected patients. The SNR was significantly higher on NG-MRCP (CHD 22.40, gallbladder 17.13) than RT-MRCP (CHD 17.05, gallbladder 9.30). Interobserver agreement was fair to perfect. CONCLUSION: Navigator-gated MRCP is more useful than respiratory-triggered MRCP for evaluating the gallbladder and cystic duct in patients scheduled for laparoscopic cholecystectomy. KEY POINTS: • Magnetic resonance cholangiopancreatography (MRCP) provides important cystic duct information before laparoscopic cholecystectomy. • Navigator-gated (NG) MRCP images were better than conventional respiratory-triggered (RT) MRCP. • The signal-to-noise ratio was significantly higher for NG-MRCP than for conventional RT-MRCP. • Balanced turbo-field-echo NG-MRCP is useful for evaluating the gallbladder and cystic duct.

Usefulness of diffusion-weighted imaging in the localization of prostate cancer.

PURPOSE: Advances in high-precision radiation therapy techniques for patients with prostate cancer permit selective escalation of the radiation dose delivered to the dominant intraprostatic lesion and improve the therapeutic ratio. We evaluated the value of diffusion-weighted imaging (DWI) for dominant intraprostatic lesion assessment. METHODS AND MATERIALS: The study population consisted of 23 patients with early prostate cancer. Before undergoing total prostatectomy, they were evaluated by means of magnetic resonance imaging, including DWI. T2-weighted imaging (T2WI) with and without DWI were retrospectively assessed by six independent observers. Imaging findings were compared with pathologic results from whole prostate specimens on a lesion-by-lesion basis. RESULTS: Pathologic study identified 43 lesions in 23 patients. On magnetic resonance imaging, the six observers correctly identified 11-22 of 43 lesions (sensitivity, 26-51%) on T2WI alone and 20-31 (sensitivity, 47-72%) on T2WI plus DWI. Positive predictive values were 42-73% on T2WI alone and 58-80% on T2WI plus DWI. For all observers, detection was higher on combined T2WI and DWI than on T2WI alone. CONCLUSION: Because the addition of DWI to T2WI improves the detectability of prostate cancer, DWI may offer a promising new approach for radiation therapy planning.

[Case of drug-induced lung injury due to Rebamipide].

A 76-year-old man was admitted because of chest discomfort and diffuse pulmonary interstitial shadows. The diagnosis of drug-induced lung injury due to Rebamipide was made based on the transbronchial lung biopsy specimen and Drug Lymphocyte Stimulating Test (DLST) for Rebamipide (Mucosta). Corticosteroid therapy was effective.