Shintaro Ichikawa

Dilution method of gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI).

To elucidate whether a contrast agent dilution method (dilution method), in which gadoxetate disodium (Gd‐EOB‐DTPA) is diluted with saline, is useful for good‐quality arterial‐phase images.

Intravoxel incoherent motion imaging of the kidney: alterations in diffusion and perfusion in patients with renal dysfunction

PURPOSE To investigate the relationship between estimated glomerular filtration rate (eGFR) and parameters calculated using intravoxel incoherent motion (IVIM) imaging of the kidneys. MATERIALS AND METHODS We studied 365 patients, divided into 4 groups based on eGFR levels (mL/min/1.73m(2)): group 1, eGFR≥80(n=80); group 2, eGFR 60-80 (n=156); group 3, eGFR 30-60 (n=114); and group 4 ,eGFR<30 (n=15). IVIM imaging was used to acquire diffusion-weighted images at 12 b values. The diffusion coefficient of pure molecular diffusion (D), the diffusion coefficient of microcirculation or perfusion (D*), and perfusion fraction (f) were compared among the groups using group 1 as control. RESULTS In the renal cortex, D* values were significantly lower in groups 2, 3, and 4 than in group 1. The D value of renal cortex was significantly low in only group 3. In the renal medulla, the D* and D values were significantly lower only in groups 2 and 3, respectively. CONCLUSION As renal dysfunction progresses, renal perfusion might be reduced earlier and affected more than molecular diffusion in the renal cortex. These changes are effectively detected by IVIM MR imaging.

Comparison of the diagnostic accuracies of magnetic resonance elastography and transient elastography for hepatic fibrosis

OBJECTIVES To compare the diagnostic accuracies of magnetic resonance elastography (MRE) and transient elastography (TE) for hepatic fibrosis. MATERIALS AND METHODS This retrospective study was approved by the institutional review board and included 113 patients (mean age, 63.1±12.2years; 84 men and 29 women) with chronic liver disease who underwent liver biopsy or resection, histopathologic assessment (METAVIR scoring system), and TE within 6months of MRE. Diagnostic accuracies of MRE and TE were compared using receiver operating characteristic curve analysis. Appropriate cutoff values of the two methods determined by maximum positive and minimum negative likelihood ratios were used to calculate the positive and negative predictive values for discriminating significant fibrosis (≥F2) from F0-F1 or cirrhosis (F4) from F0-F3. RESULTS Mean (95% confidence interval) area under the receiver operating characteristic curve values of MRE for cirrhosis (F4) (0.97 [0.93-0.99] vs. 0.93 [0.87-0.96]; P=0.0308), clinically significant fibrosis (≥F2) (0.98 [0.94-0.99] vs. 0.87 [0.79-0.92]; P=0.0003), and any fibrosis (≥F1) (0.97 [0.92-0.99] vs. 0.87 [0.76-0.93]; P=0.0126) were significantly higher than those of TE. By using the cutoff values derived from the maximum positive likelihood ratio, the positive and negative predictive values for≥F2 were 98.8% and 83.9%, respectively, by MRE and 98.2% and 44.8%, respectively, by TE; and for F4, 97.0% and 86.3%, respectively, by MRE and 95.8% and 77.5%, respectively, by TE. CONCLUSION MRE has better diagnostic accuracy than TE for staging hepatic fibrosis.

Intravoxel incoherent motion imaging of focal hepatic lesions

To compare diffusivity values between malignant and benign focal hepatic lesions using the intravoxel incoherent motion model.

MRI-based staging of hepatic fibrosis: Comparison of intravoxel incoherent motion diffusion-weighted imaging with magnetic resonance elastography.

To evaluate the use of intravoxel incoherent motion (IVIM) imaging for staging hepatic fibrosis, and compare its staging ability with that of magnetic resonance elastography (MRE).

Added Value of a Gadoxetic Acid-enhanced Hepatocyte-phase Image to the LI-RADS System for Diagnosing Hepatocellular Carcinoma

PURPOSE We investigated the added value of the hypointensity on hepatocyte-phase (HP) imaging of gadoxetic acid-enhanced MRI (EOB-MRI) in the 2014 version of the Liver Imaging Reporting and Data System (LI-RADS) for distinguishing hepatocellular carcinoma (HCC) from benign hepatic lesions in patients with chronic liver disease. METHODS We retrospectively evaluated targeted lesions (111 HCCs, 28 benign hepatic lesions) of 139 patients (101 men, 38 women; aged 18 to 89 years, mean age, 68 ± 11 years) with chronic liver disease. EOB-MRI and dynamic contrast-enhanced computed tomography (CECT) were performed within 3 months. Two abdominal radiologists independently reviewed 3 imaging datasets: (1) EOB-MRI without an HP image using the LI-RADS system (MR imaging without HP); (2) EOB-MRI with an HP image using a modified version of the LI-RADS system in which hypointensity on the HP image was used as an additional major criterion of malignancy (MR imaging with HP); and (3) dynamic contrast-enhanced computed tomography (CECT) images using the LI-RADS system. We evaluated intra- and inter-reader agreement with kappa statistics along with 95% confidence intervals and compared diagnostic sensitivity and specificity of the 3 imaging datasets with McNemars test. RESULTS The sensitivities of MR imaging were statistically higher with HP (Reader 1, 95% [107/111]; Reader 2, 95% [106/111]) than without HP (Reader 1, 84% [93/111], P = 0.002; Reader 2, 86% [96/111], P = 0.002). Specificity was comparably high between MR imaging with HP (Reader 1, 96% [27/28]; Reader 2, 96% [27/28]) and dynamic CECT (Reader 1, 100% [28/28], P = 0.317; Reader 2, 100% [28/28], P = 0.317) and MR imaging without HP (Reader 1, 96% [27/28], P = 1.00; Reader 2, 100% [28/28], P = 0.317). CONCLUSION The use of an HP image from EOB-MRI as an additional major criterion improved the sensitivity of LI-RADS to distinguish HCCs from benign hepatic lesions while retaining high specificity.

Hepatitis activity should be considered a confounder of liver stiffness measured with MR elastography

To evaluate the effect of hepatitis activity on liver stiffness measurements and the role of serum alanine aminotransferase (ALT) in liver fibrosis staging by MR elastography (MRE).

Presence of a hypovascular hepatic nodule showing hypointensity on hepatocyte-phase image is a risk factor for hypervascular hepatocellular carcinoma

To determine whether the presence of a hypovascular nodule in the liver showing hypointensity on hepatocyte‐phase of gadoxetic acid‐enhanced magnetic resonance imaging (EOB‐MRI) is a risk factor for hypervascular hepatocellular carcinoma (HCC) in patients with chronic liver disease.

Association of splenic MR elastographic findings with gastroesophageal varices in patients with chronic liver disease.

To identify magnetic resonance imaging (MRI)‐based parameters associated with gastroesophageal varices (GEVs) in patients with chronic liver disease.

Usefulness of MR elastography for detecting clinical progression of cirrhosis from child-pugh class A to B in patients with type C viral hepatitis.

To evaluate the usefulness of magnetic resonance elastography (MRE) in detecting the clinical progression of cirrhosis from Child‐Pugh class A to B in patients with hepatitis C.