Shigeru Kiryu

Free-breathing diffusion-weighted imaging for the assessment of inflammatory activity in Crohn's disease.

To investigate the application of free‐breathing diffusion‐weighted MR imaging (DWI) to the assessment of disease activity in Crohns disease.

Noninvasive bioluminescence imaging of luciferase expressing intracranial U87 xenografts: correlation with magnetic resonance imaging determined tumor volume and longitudinal use in assessing tumor growth and antiangiogenic treatment effect.

OBJECTIVE: Outcome studies in rodent tumor models rely on both histological and noninvasive study end points. Intracranial models require special tools to observe tumor growth over time noninvasively, such as magnetic resonance imaging (MRI), computed tomographic scanning, or cranial window techniques. These techniques share disadvantages in terms of cost, technical expertise required, and overall animal throughput for analysis. In this report, we sought to validate the use of the relatively newer technique of bioluminescence imaging (BLI) of intracranial glioblastoma xenograft growth by comparing it with gadolinium-enhanced MRI. METHODS: U87MG glioma cell lines genetically engineered to express the firefly luciferase gene were stereotactically injected into nude mice in the left frontal lobe. Weekly BLI and MRI were performed after the inoculation of tumor cells. For BLI, tumor growth was assessed as the peak BLI after systemic injection of luciferin substrate. MRI-based growth curves were created by three-dimensional volumetric reconstruction of axial gadolinium-enhanced MRI data covering the whole brain. In a separate experiment, mice were treated with adenoviruses encoding antiangiogenic soluble vascular endothelial growth factor receptors, and treatment effect was monitored by BLI. RESULTS: Untreated tumor growth was readily detected and observed over time by serial BLI measurements. Furthermore, tumor-derived light emission was highly correlated with volume of tumor as assessed by MRI. Furthermore, the tested antiangiogenic treatment effect was readily detected using this technique, suggesting the power of the technique for sensitive monitoring of novel therapeutics. CONCLUSION: BLI offers a simple and rapid technique for assessing intracranial glioblastoma growth in rodent models noninvasively, which correlates well with MRI. The speed of the BLI technique can increase experimental throughput, allows for targeted histological analysis in animals showing the greatest treatment effects, and provides new insights into the kinetics of intracranial tumor growth in the setting of different treatments.

Spectrum of Epstein-Barr virus-related diseases: a pictorial review

Epstein-Barr virus (EBV) prevails among more than 90% of the adult population worldwide. Most primary infections occur during young childhood and cause no or only nonspecific symptoms; then the virus becomes latent and resides in lymphocytes in the peripheral blood. Inactive latent EBV usually causes no serious consequences, but once it becomes active it can cause a wide spectrum of malignancies: epithelial tumors such as nasopharyngeal and gastric carcinomas; mesenchymal tumors such as follicular dendritic cell tumor/sarcoma; and lymphoid malignancies such as Burkitt lymphoma, lymphomatoid granulomatosis, pyothorax-associated lymphoma, immunodeficiency-associated lymphoproliferative disorders, extranodal natural killer (NK) cell/T-cell lymphoma, and Hodgkin’s lymphoma. The purpose of this article is to describe the spectrum of EBV-related diseases and their key imaging findings. EBV-related lymphoproliferative disorders and lymphomas are especially common in immunocompromised patients. Awareness of their clinical settings and imaging spectrum contributes to early detection and early treatment of possibly life-threatening disorders.

Breath-hold T2-weighted Mri of Hepatic Tumors: Value of Echo Planar Imaging with Diffusion-sensitizing Gradient

PURPOSE The purpose of our study was to evaluate the efficacy of echo planar imaging (EPI) as a breath-holding T2-weighted technique for imaging focal hepatic lesions. METHOD Forty-eight patients with focal hepatic lesions (9 metastases, 21 hepatocellular carcinomas, 1 cholangiocarcinoma, 16 hemangiomas, and 2 cysts) underwent single shot EPI with and without a small diffusion-sensitizing gradient (DSG) (beta values = 55 s/mm2) at 1.5 T. Comparison was made with breath-holding T2-weighted fast SE (FSE) sequences. RESULTS Lesion-to-liver signal intensity ratio of EPI was significantly better than that of T2-weighted FSE (p < 0.05) in patients with metastasis. Use of DSG suppressed bright signals from vessels or periportal tissue, resulting in better conspicuity of small lesions. EPI with DSG visualized more metastatic deposits than T2-weighted FSE (p < 0.01). CONCLUSION EPI with a small DSG is helpful for detection of small hepatic metastases.

Detection of hepatocellular carcinoma by Gd-EOB-DTPA-enhanced liver MRI: comparison with triple phase 64 detector row helical CT.

PURPOSE To compare the diagnostic performance of Gd-EOB-DTPA-enhanced MRI with that of triple phase 64-MDCT in the detection of hepatocellular carcinoma (HCC). PATIENTS AND METHODS Thirty-four patients with 52 surgically proven lesions underwent Gd-EOB-DTPA-enhanced MRI and triple phase 64-MDCT. Two observers independently evaluated MR and CT imaging on a lesion-by-lesion basis. Sensitivity, positive and negative predictive values and reproducibility were evaluated. The diagnostic accuracy of each modality was assessed with alternative-free response receiver operating characteristic (ROC) analysis. RESULTS Both observers showed higher sensitivity in detecting lesions with MRI compared to CT, however, only the difference between the two imaging techniques for observer 2 was significant (P=0.034). For lesions 1cm or smaller, MRI and CT showed equal sensitivity (both 62.5%) with one observer, and MRI proved superior to CT with the other observer (MRI 75% vs. CT 56.3%), but the latter difference was not significant (P=0.083). The difference in positive and negative predictive value between the two imaging techniques for each observer was not significant (P>0.05). The areas under the ROC curve for each observer were 0.843 and 0.861 for MRI vs. 0.800 and 0.833 for CT and the differences were not significant. Reproducibility was higher using MRI for both observers, but the result was not significant (MRI 32/33 vs. CT 29/33, P=0.083). CONCLUSION Gd-EOB-DTPA-enhanced MRI tended to show higher diagnostic accuracy, sensitivity and reproducibility compared to triple phase 64-MDCT in the detection of hepatocellular carcinoma, however statistical significance was not achieved.

Relationship between liver function and liver signal intensity in hepatobiliary phase of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging.

Objective: To evaluate the effect of liver function on liver signal intensity in gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging in humans and to examine the biochemical factors related to signal intensity in the hepatobiliary phase. Methods: This study included 48 patients with suspected hepatocellular carcinoma or metachronous liver metastases from colorectal cancer. The patients were divided into 2 groups: the chronic liver dysfunction and the normal liver function. All the individuals of both groups had magnetic resonance imaging before injection and at 5, 10, 15, 20, 25, and 30 minutes after bolus administration of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid. The time point when the mean liver signal-to-noise ratio (SNR) reached a peak was determined for each group, and the mean liver SNR at the peak point was compared between the groups. In all the patients, stepwise multivariate analysis was used to evaluate the relationship between the liver SNR at the peak time point and the laboratory data, using the following biochemical factors: prothrombin time, total bilirubin level, cholinesterase level, albumin level, creatinine level, indocyanine green retention rate at 15 minutes, and Child-Pugh score. Results: The mean values of liver SNR increased gradually. The mean liver SNR reached peak at 30 minutes after contrast injection in both groups and was significantly lower in the chronic liver dysfunction group than in the normal liver function group. Indocyanine green retention rate at 15 minutes was the only significant contributor to the liver signal intensity at the peak time point (30 minutes). Conclusions: The degree of liver enhancement in the hepatobiliary phase may reflect liver cell function. The measurement of liver signal intensity in the hepatobiliary phase may be useful in predicting whole and regional hepatic functional reserves.

MR imaging of the biliary tract with Gd-EOB-DTPA: effect of liver function on signal intensity.

OBJECTIVE To quantitatively evaluate the signal intensity of the biliary tract in gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance (MR) imaging and to investigate the effect of liver function on the signal intensity of the biliary tract. MATERIALS AND METHODS A total of 32 patients with and without chronic liver disease (normal liver group, n = 15; chronic liver disease group, n = 17) were included in this study. All patients were prospectively enrolled for evaluation of known or suspected focal liver lesions. In the chronic liver disease group, the etiologies were chronic hepatitis C virus infection (n = 12) and chronic hepatitis B virus infection (n = 5). The median Child-Pugh score was 5 (range, 5-7). Each patient received the standard dose of Gd-EOB-DTPA (0.025 mmol/kg of body weight). Post-contrast T1-weighted MR images were obtained at 5, 10, 15, 20, 25, and 30 min after administration of Gd-EOB-DTPA. Maximum signal intensities (SIs) of the right and left hepatic ducts, common hepatic duct, and common bile duct were measured. Relative signal intensity was calculated as follows: relative SI = maximum SI(bileduct)/mean SI(muscle). Serum albumin level, serum total bilirubin level, prothrombin time, indocyanine green retention rate at 15 min (ICG-R15), and estimated glomerular filtration rate were entered into regression analysis. RESULTS The signal intensity of the bile duct reached a peak 30 min after administration of Gd-EOB-DTPA. The mean relative signal intensity of the right and left hepatic ducts at the peak time point was not significantly different between the two groups, while increase in signal intensity was delayed in the chronic liver disease group. The mean relative signal intensity of the common hepatic duct and that of the common bile duct at the peak time point were significantly different between the two groups (Wilcoxon rank-sum test, P = 0.03, respectively). Stepwise regression analysis revealed that ICG-R15 was a significant predictor of the signal intensity of the bile duct (right and left hepatic ducts, P = 0.04; common hepatic duct, P = 0.008; common bile duct, P = 0.003). CONCLUSIONS The results of our study demonstrate that the presence of chronic liver disease significantly affects the signal intensity of the bile duct in Gd-EOB-DTPA-enhanced MR imaging. ICG-R15 was only a significant predictor of the signal intensity of the bile duct. The signal intensity of the bile duct may reflect underlying liver function.

Fate of hypointense lesions on Gd-EOB-DTPA-enhanced magnetic resonance imaging

PURPOSE To investigate the natural outcome and clinical implication of hypointense lesions in the hepatobiliary phase of Gd-EOB-DTPA-enhanced MRI. MATERIALS AND METHODS Forty patients underwent Gd-EOB-DTPA-enhanced MRI for preoperative evaluation of HCC. Hypointense lesions in the hepatobiliary phase that were hypovascular 5mm of more were extracted for follow-up. We performed a longitudinal study retrospectively for these lesions regardless of whether classical HCC developed or emerged in a different area from that of the lesions being followed. RESULTS Thirty one patients displayed 130 hypointense lesions on MRI and only nine showed no hypointense lesions. In total, 17 (13.1%) of 130 hypointense lesions on MRI developed into classical HCC. The cumulative rates for these lesions to develop into classical HCC were 3.2% at 1 year, 11.1% at 2 years and 15.9% at 3 years. The total occurrence rates of classical HCC (25.8% at 1 year, 52.6% at 2 years and 76.4% at 3 years) were higher compared to those regarding only occurrence of classical HCC from hypointense lesions on MRI (10.0% at 1 year, 35.6% at 2 years and 44.6% at 3 years), although no significant difference was observed (p=0.073). CONCLUSIONS Hypointense lesions that are detected in the hepatobiliary phase of Gd-EOB-DTPA-enhanced MRI have some malignant potential, although treating these lesions aggressively in patients who already have HCC may be too severe.

Adaptive Iterative Dose Reduction in coronary CT angiography using 320-row CT: Assessment of radiation dose reduction and image quality

BACKGROUND Several methods have been developed to reduce the radiation dose in coronary computed tomography angiography (CTA). OBJECTIVE The objective of our study was to evaluate the effects of Adaptive Iterative Dose Reduction (AIDR) on objective and subjective image quality as well as the radiation dose, compared with conventional filtered back projection (FBP), in coronary CTA. METHODS We retrospectively reviewed 100 consecutive patients who underwent coronary CTA. In the first 50 patients, a higher tube current was used, and images were reconstructed with FBP. In the last 50 patients, a lower tube current was used, and images were reconstructed with AIDR. Subjective and objective image quality (noise, signal-to-noise ratio, contrast-to-noise ratio) were assessed. RESULTS The median radiation dose of the AIDR group was 22% lower than that of the FBP group (4.2 vs 5.4 mSv; P = 0.0001). No significant difference was found in subjective image quality, noise, signal-to-noise ratio, or contrast-to-noise ratio between the 2 groups. CONCLUSION AIDR reduced the tube current which resulted in reduction of radiation dose in coronary CTA while maintaining subjective and objective image quality compared with coronary CTA reconstructed with FBP.

Magnetic resonance diffusion-weighted imaging in the characterization of pancreatic mucinous cystic lesions

AIM The aim of the study was to evaluate the utility of diffusion-weighted imaging (DWI), including apparent diffusion coefficient (ADC) measurement, in order to differentiate mucinous cystic neoplasms (MCNs) from intraductal papillary mucinous neoplasms (IPMNs) of the pancreas. MATERIALS AND METHODS Fifty cases of IPMN with a total of 62 lesions, and eight cases of MCN, were retrospectively selected for the study. The cases of IPMN were selected using multimodality clinical or histopathological criteria, while all MCN lesions were histopathologically proven. DWI was carried out using b values of 500 and 1000s/mm(2). Visual assessment was performed by two radiologists who used two categories (low-iso or high signal intensity). ADC values of the lesions were also calculated. Fishers exact test and the Mann-Whitney U test were used for statistical analysis. RESULTS All IPMN lesions demonstrated low-iso signal intensities compared with the pancreatic parenchyma on DWI. Two of the MCN lesions demonstrated low-iso signal intensities, and six lesions demonstrated high signal intensities. The ADC values for IPMNs (mean 2.9 ± 0.024 × 10(-3)mm(2)/s) were significantly higher than those for MCNs (mean 2.1 ± 0.30 × 10(-3)mm(2)/s). ROC analysis showed an optimal cut-off value of 2.4 × 10(-3)mm(2)/s for differentiating between the two types of lesions, providing a sensitivity of 98% and a specificity of 88%. CONCLUSION The results of the present study suggest that ADC values in mucinous cystic lesions of the pancreas can be advantageous for their characterization into IPMN and MCN.