Yukichi Tanahashi

Fibrosis and Postoperative Fistula of the Pancreas: Correlation with MR Imaging Findings—Preliminary Results

PURPOSE To assess the potential value of magnetic resonance (MR) imaging in evaluating pancreatic fibrosis and predicting the development of postoperative pancreatic fistula. MATERIALS AND METHODS This retrospective study had institutional review board approval, and the requirement for informed consent was waived. MR images obtained in 29 consecutive patients (15 men, 14 women; mean age, 64.9 years; age range, 21-80 years) who underwent pancreatectomy were evaluated. The pancreas-to-muscle signal intensity (SI) ratio on unenhanced T1- and T2-weighted, dynamic contrast material-enhanced, and diffusion-weighted images and the apparent diffusion coefficient (ADC) of the pancreas were measured. MR imaging parameters were correlated with the degrees of pancreatic fibrosis and expression of activated pancreatic stellate cells (PSCs) by using univariate and multivariate regression analyses and receiver operating characteristic curve analysis. The relationships between the development of postoperative pancreatic fistula and the MR imaging measurements were examined by using logistic regression analysis and the Mann-Whitney U test. RESULTS Multiple regression analysis showed that pancreas-to-muscle SI ratios on T1-weighted images and ADC values were independently associated with pancreatic fibrosis (r(2) = 0.66, P < .001) and with activated PSC expression (r(2) = 0.67, P < .001). The mean pancreas-to-muscle SI ratio (± standard deviation) on T1-weighted images was higher (P = .0029) for patients with postoperative pancreatic fistula (1.6 ± 0.2) than for those without (1.2 ± 0.2), and the odds ratio for postoperative pancreatic fistula was 21.3 in patients with an SI ratio of 1.41 and higher. CONCLUSION The pancreas-to-muscle SI ratio on T1-weighted MR images of the pancreas may be a potential biomarker for assessment of pancreatic fibrosis and prediction of postoperative pancreatic fistula.

Low-Iodine-Load and Low-Tube-Voltage CT Angiographic Imaging of the Kidney by Using Bolus Tracking with Saline Flushing

PURPOSE To prospectively determine the feasibility of low-iodine-load and low-tube-voltage computed tomographic (CT) angiographic imaging of the kidney and to evaluate the opacification and image quality compared with moderate-iodine-load and high-iodine-load techniques. MATERIALS AND METHODS Institutional review board approval and written informed consent was obtained. One hundred thirteen consecutive patients randomly underwent three protocols for dual-phase renal CT angiographic imaging: high-iodine-load (600 mg iodine per kilogram of body weight at 120 kVp); moderate-iodine-load (400 mg iodine per kilogram of body weight at 80 kVp); and low-iodine-load (contrast agent injection initially prepared at 400 mg iodine per kilogram of body weight but stopped immediately after bolus-tracking trigger at 80 kVp) scanning. CT numbers of vessels and kidneys were measured. CT numbers and signal-to-noise ratio (SNR) were compared with one-way analysis of variance and posthoc Tukey-Kramer test and depiction of vessels and image noise, with Kruskal-Wallis test and pair-wise Mann-Whitney test with Bonferroni correction. RESULTS Mean iodine weight administered was significantly reduced in order of low- (16.4 g), moderate- (23.5 g), and high-iodine-load (33.7 g) protocols (P < .001). Mean CT numbers of abdominal aorta, renal artery, and renal cortex in first phase were significantly lower with high-iodine-load protocol (308, 274, and 132 HU, respectively) than with moderate- (347, 334, and 156 HU, respectively; P = .001-.006) or low-iodine-load (362, 316, and 161 HU, respectively; P = .001-.003) protocol. Mean CT number of renal vein in second phase was significantly lower with low-iodine-load protocol (223 HU) than with moderate- (299 HU; P < .001) or high-iodine-load (258 HU; P = .020). Mean SNR of renal medulla in second phase was significantly lower (P = .019) with moderate-iodine-load protocol (mean SNR, 7.2) than with high-iodine-load protocol (mean SNR, 10.0). No significant difference in image quality grades was found between high-iodine-load (mean grade, 2.6-2.9), moderate-iodine-load (mean grade, 2.6-3.0), and low-iodine-load (mean grade, 2.6-2.9) protocols (P = .018-.31). CONCLUSION Combined application of low-iodine-load, bolus tracking with saline flushing, and low-tube-voltage scanning is feasible and resulted in substantial reduction of iodine dose for renal CT angiographic imaging without compromising image quality.

Reducing iodine load in hepatic CT for patients with chronic liver disease with a combination of low-tube-voltage and adaptive statistical iterative reconstruction

PURPOSE To prospectively assess the effect of reduced iodine load to contrast enhancement, image quality, and detectability of hepatocellular carcinomas (HCCs) in hepatic CT with a combination of 80 kVp tube voltage setting and adaptive statistical iterative reconstruction (ASIR) technique in patients with chronic liver disease. MATERIALS AND METHODS This HIPAA-compliant study was approved by our institutional review board and written informed consent was obtained in all patients. During a recent 9-month period, 170 consecutive patients (114 men and 56 women; age range, 40-85 years; mean, 67.7 years) with suspected chronic liver diseases were randomized into three CT groups according to the following iodine-load and tube-voltage protocols: 600 milligram per kilogram body weight (mg/kg) iodine load and 120 peak kilovolt (kVp) tube voltage setting (600-120 group), 500 mg/kg and 80 kVp (500-80 group), and 400mg/kg and 80 kVp (400-80 group). Analysis of variance was conducted to evaluate differences in CT number, background noise, signal-to-noise ratio (SNR), effective dose, HCC-to-liver contrast-to-noise ratio (CNR), and figure of merit (FOM). Sensitivity, specificity, and area under the receiver-operating-characteristic curve (AUC) were compared to assess the detectability of HCCs. RESULTS Vascular and hepatic enhancement in the 400-80 and 500-80 groups was comparable to or greater than that in the 600-120 group (P<.05). Subjective image quality was comparable among the three groups. Sensitivity, specificity, and AUC for detecting HCCs were comparable among the groups. The effective dose was kept low (3.3-4.1 mSv) in all three groups. CONCLUSION Iodine load can be reduced by 33% in CT of the liver with a combination of 80 kVp tube voltage setting and ASIR technique, without compromising the contrast enhancement, image quality, and detection of HCCs.

Reduction of iodine load in CT imaging of pancreas acquired with low tube voltage and an adaptive statistical iterative reconstruction technique.

Purpose To prospectively assess the contrast enhancement, image quality, radiation dose, and detectability of malignant pancreatic tumors with pancreatic computed tomography (CT) obtained at an 80-kilovolt (peak) (kV[p]) tube voltage setting and reduced iodine dose. Methods Institutional review board approval and written informed consent were obtained. During a recent 10-month period, 136 patients (66 men and 70 women; age range, 21–86 years; mean ± SD age, 65.9 ± 11.0 years) with suspected pancreatic disease were randomized into 3 groups according to the following iodine-load and tube-voltage protocols: 600 mg of iodine per kilogram body weight (mg/kg) and 120 kV(p) (600-120 group), 500 mg/kg and 80 kV(p) (500-80 group), and 400 mg/kg and 80 kV(p) (400-80 group). Analysis of variance was conducted to evaluate differences in CT number, background noise, signal-to-noise ratio, effective dose, lesion-to-pancreas contrast-to-noise ratio, and figure of merit. Sensitivity, specificity, and area under the receiver-operating-characteristic curve were compared to assess the detectability of malignant pancreatic tumors. Results The signal-to-noise ratios in vessels were greater (P < 0.05) in the 400-80 and 500-80 groups than in the 600-120 group, and those in pancreas were comparable between the 400-80 and 600-120 groups. No significant difference was found in effective dose, image quality, lesion-to-pancreas contrast-to-noise ratio, or figure of merit between the groups. Sensitivity, specificity, and area under the receiver-operating-characteristic curve for detecting malignant pancreatic tumors were comparable between the groups. Conclusions Pancreatic CT with an 80-kV(p) setting and 400-mg iodine per kilogram contrast material load facilitates the reduction of iodine dose while maintaining image quality and the detectability of malignant pancreatic tumors.

Diffusion kurtosis imaging of the pancreas for the assessment of HbA1c levels

To evaluate the feasibility of diffusion kurtosis (DK) imaging of the pancreas for the assessment of hemoglobin (Hb) A1c values.

Multiphase Contrast-Enhanced Magnetic Resonance Imaging Features of Bacillus Calmette-Guérin-Induced Granulomatous Prostatitis in Five Patients

Objective To evaluate the multiphase contrast-enhanced magnetic resonance (MR) imaging features of Bacillus Calmette-Guérin (BCG)-induced granulomatous prostatitis (GP). Materials and Methods Magnetic resonance images obtained from five patients with histopathologically proven BCG-induced GP were retrospectively analyzed for tumor location, size, signal intensity on T2-weighted images (T2WI) and diffusion-weighted images (DWI), apparent diffusion coefficient (ADC) value, and appearance on gadolinium-enhanced multiphase images. MR imaging findings were compared with histopathological findings. Results Bacillus Calmette-Guérin-induced GP (size range, 9-40 mm; mean, 21.2 mm) were identified in the peripheral zone in all patients. The T2WI showed lower signal intensity compared with the normal peripheral zone. The DWIs demonstrated high signal intensity and low ADC values (range, 0.44-0.68 × 10-3 mm2/sec; mean, 0.56 × 10-3 mm2/sec), which corresponded to GP. Gadolinium-enhanced multiphase MR imaging performed in five patients showed early and prolonged ring enhancement in all cases of GP. Granulomatous tissues with central caseation necrosis were identified histologically, which corresponded to ring enhancement and a central low intensity area on gadolinium-enhanced MR imaging. The findings on T2WI, DWI, and gadolinium-enhanced images became gradually obscured with time. Conclusion Bacillus Calmette-Guérin-induced GP demonstrates early and prolonged ring enhancement on gadolinium-enhanced MR imaging which might be a key finding to differentiate it from prostate cancer.

Whole-body CT with high heat-capacity X-ray tube and automated tube current modulation—Effect of tube current limitation on contrast enhancement, image quality and radiation dose

PURPOSE To evaluate the effect of tube current limitation on contrast enhancement, image quality, and radiation dose in whole-body 64-detector CT with a high heat-capacity X-ray tube and automated tube current modulation. MATERIALS AND METHODS One hundred eighteen patients were randomized into three whole-body CT protocols: tube current limitation at 210 mA, 450 mA, and no limitation. Signal-to-noise ratio (SNR), dose-length product (DLP), estimated effective dose (ED), and image quality were assessed. RESULTS Mean SNR of aorta was comparable among protocols, but that of liver was somewhat lower in 210-mA than in 450-mA and no-limitation protocols (p<0.05). Mean DLP with 210-mA (533.8 mGy cm) was reduced by 31% from that with 450-mA (768.4 mGy cm) and by 38% from that with no-limitation protocol (861.3 mGy cm), respectively. Image quality was slightly degraded (p<0.017) with 210 mA relative to the others in thorax and pelvis, but no difference was found in diagnostic acceptability. CONCLUSION For whole-body CT using multidetector CT mounted with a high heat-capacity X-ray tube, an appropriate tube current limitation setting may help reduce excessive radiation dose without significant compromise in diagnostic acceptability.

Peritoneal chronic inflammatory mass formation due to gallstones lost during laparoscopic cholecystectomy

We here describe the radiologic findings of peritoneal chronic abscess formation due to gallstones lost within the peritoneum during laparoscopic cholecystectomy (LC). A radiologic workup 7 months after LC revealed a soft-tissue mass with contrast enhancement, harboring internal necrosis and punctate calcium located in the Morrisons pouch. The mass exhibited restricted water molecule diffusion, absence of fat deposition, and increased F-18 fluorodeoxy-D-glucose uptake, thus mimicking a malignant tumor. The biopsy revealed an inflammatory granuloma. Another patient with similar findings was treated with percutaneous abscess drainage. Thus, radiologists should be aware of this disease condition and its imaging findings.

Prediction of early response to uterine artery embolization in fibroids: Value of MR signal intensity ratio

OBJECTIVE To quantitatively assess magnetic resonance (MR) imaging findings that help predict early post-therapeutic response in fibroids following uterine artery embolization (UAE). METHODS Fifteen patients with a total of 52 fibroids underwent UAE. The signal intensity ratio (SIR) on T1-, T2-, diffusion weighted and gadolinium-enhanced images was calculated by dividing the mean signal intensity of fibroids by that of the abdominal rectus muscle. Fibroids were divided into the two groups: affected (post-UAE volume reduction rate>median of all fibroids) and unaffected (<median rate). The SIRs were compared between the two groups. ROC analysis was used to evaluate the predictive performance for differentiating the affected from unaffected lesions. RESULTS The SIRs of the affected group were significantly lower on T1-weighted images (0.85±0.1 vs 0.95±0.2) (P=0.0001), but higher on T2-weighted (1.30±0.6 vs 1.12±0.9) (P=0.026) and gadolinium-enhanced images (1.51±0.2 vs 1.20±0.4) (P=0.0002) than those of the unaffected group. There was no significant difference in ADC values between the two groups (P=0.510). The sensitivity, specificity, and area under the ROC curve (AUC) in the prediction of the affected lesions were 92%, 50%, and 0.712 with SIR on T1-weighted images, and 85%, 62%, and 0.731 with SIR on gadolinium-enhanced images, respectively. CONCLUSIONS The SIRs on T1-weighted images and gadolinium-enhanced images were useful for the prediction of the changes in size of fibroids responding to UAE.

Simultaneous acquisition of MR angiography and diagnostic images of abdomen at view-sharing multiarterial phases and comparing the effect of two different contrast agents: MRA Acquisition in Abdominal MRI

Simultaneous acquisition of magnetic resonance angiography (MRA) and diagnostic images is challenging in contrast‐enhanced upper abdominal MRI.