Tosiaki Miyati

Noninvasive MRI assessment of intracranial compliance in idiopathic normal pressure hydrocephalus

To assess the state and dynamics of the intracranial system in idiopathic normal‐pressure hydrocephalus (I‐NPH), we determined intracranial compliance using magnetic resonance imaging (MRI).

Imaging parameter effects in apparent diffusion coefficient determination of magnetic resonance imaging

PURPOSE Although an apparent diffusion coefficient (ADC) value is often used for differential diagnosis of tumours, it varies with scanning parameters. The present study was performed to investigate the influence of imaging parameters, i.e., b value, repetition time (TR) and echo time (TE), on ADC value. METHODS The phantoms were scanned using diffusion weighted imaging (DWI) with changing b values (b=0-3000 s/mm(2)), TR and TE to determine the influence on ADC. Moreover, ADC of the brain in normal volunteers was determined with varying b values (b=0-1000 s/mm(2)). RESULTS Diffusion decay curves were obtained by biexponential fitting in all phantoms. The points where fast and slow components of the biexponential decay crossed were called turning points. The b values of turning points that crossed from the biexponential curve were different in each phantom. The b values of turning points depended on ADC of fast diffusion component. When ADC is calculated using two b values of front and back for the turning point, the ADC value may be different. Therefore, it was necessary to perform calculations by b value until the turning point to obtain the ADC value of the fast component. In addition, b≥100 was recommended to avoid the influence of perfusion by blood. Furthermore, the choice of long TR and short TE was effective for accurate measurement of ADC. CONCLUSION It is important to determine the turning point for measuring ADC.

Gd-EOB-DTPA-enhanced magnetic resonance imaging and alpha-fetoprotein predict prognosis of early-stage hepatocellular carcinoma

The survival of patients with hepatocellular carcinoma (HCC) is often individually different even after surgery for early‐stage tumors. Gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd‐EOB‐DTPA)‐enhanced magnetic resonance imaging (MRI) has been introduced recently to evaluate hepatic lesions with regard to vascularity and the activity of the organic anion transporter OATP1B3. Here we report that Gd‐EOB‐DTPA‐enhanced MRI (EOB‐MRI) in combination with serum alpha‐fetoprotein (AFP) status reflects the stem/maturational status of HCC with distinct biology and prognostic information. Gd‐EOB‐DTPA uptake in the hepatobiliary phase was observed in ∼15% of HCCs. This uptake correlated with low serum AFP levels, maintenance of hepatocyte function with the up‐regulation of OATP1B3 and HNF4A expression, and good prognosis. By contrast, HCC showing reduced Gd‐EOB‐DTPA uptake with high serum AFP levels was associated with poor prognosis and the activation of the oncogene FOXM1. Knockdown of HNF4A in HCC cells showing Gd‐EOB‐DTPA uptake resulted in the increased expression of AFP and FOXM1 and the loss of OATP1B3 expression accompanied by morphological changes, enhanced tumorigenesis, and loss of Gd‐EOB‐DTPA uptake in vivo. HCC classification based on EOB‐MRI and serum AFP levels predicted overall survival in a single‐institution cohort (n = 70), and its prognostic utility was validated independently in a multi‐institution cohort of early‐stage HCCs (n = 109). Conclusion: This noninvasive classification system is molecularly based on the stem/maturation status of HCCs and can be incorporated into current staging practices to improve management algorithms, especially in the early stage of disease. (Hepatology 2014;60:1674–1685)

The Effect of Susceptibility of Gadolinium Contrast Media on Diffusion-weighted Imaging and the Apparent Diffusion Coefficient

RATIONALE AND OBJECTIVES The development of parallel magnetic resonance imaging has resulted in the frequent use of diffusion-weighted imaging (DWI) in clinical medicine, which usually involves the use of contrast medium. However, gadolinium (Gd) contrast medium may have some effect on DWI and the apparent diffusion coefficient (ADC). The present study was performed to determine whether the magnetic susceptibility of contrast medium alters the DWI signal and the value of ADC in some imaging techniques. MATERIALS AND METHODS Nonfat suppression DWI, short-time inversion recovery (STIR) combination, and chemical shift selective (CHESS) combination DWI were performed to examine 10 phantoms with gadolinium-meglumine gadopentetate (Gd-DTPA) dissolved at concentrations from 0.0005 to 0.1 mmol in physiologic saline as a contrast medium. The average pixel value and ADC of each method were determined. RESULTS ADC showed no differences between before and after treatment with contrast medium for all imaging techniques with Gd considered distributed over the whole tumor. The signal intensity did not change on nonfat suppression or CHESS combination DWI, but deteriorated on STIR. CONCLUSIONS ADC was not influenced by the magnetic susceptibility of contrast medium. In addition, it was suggested that the ability of tumor detection may be reduced if STIR is used as fat suppression.

Diffusion analysis with triexponential function in liver cirrhosis

To acquire more detailed information noninvasively through on diffusion and perfusion in normal and cirrhotic livers, we analyzed three diffusion components using triexponential function.

Influence of Gadoxetate Disodium on Oxygen Saturation and Heart Rate during Dynamic Contrast-enhanced MR Imaging.

PURPOSE To investigate whether gadoxetate disodium affects peripheral capillary oxygen saturation (SpO2) and/or heart rate (HR) during dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging in patients with liver diseases. MATERIALS AND METHODS This retrospective study was approved by the institutional review board, who waived the requirement for informed consent. Four hundred fifty-eight patients (171 women [mean age, 66.5 years; range, 23-87 years] and 287 men [mean age, 61.1 years; range, 25-89 years]) who underwent liver DCE MR imaging with gadoxetate disodium (0.025 mmol per kilogram of body weight) from October 28, 2013, to June 24, 2014, were included in this study. They were monitored for SpO2 and HR during DCE MR imaging. Motion artifact severity was graded by using a five-point scale, and transient severe motion (TSM) was defined by a score of at least 4. The association between TSM and baseline predictors was assessed, and HR and SpO2 at each postcontrast phase were compared with those at the precontrast phase in the TSM and non-TSM groups. RESULTS Four hundred thirty-six patients were included in the non-TSM group, and 22 were included in the TSM group. Although the motion score was the worst at the arterial phase, the observed mean differences in SpO2 and HR between the precontrast phase and the arterial phase were less than 1% and 5 beats per minute, respectively (mean SpO2 ± standard deviation for the non-TSM group, 96.7% ± 1.8 vs 96.9% ± 1.8 [P = .11]; SpO2 for the TSM group, 96.4% ± 1.6 vs 96.1% ± 1.6 [P > .99]) (HR for the non-TSM group, 68.9 beats per minute ± 12.4 vs 70.9 beats per minute ± 12.1 [P < .0001]; HR for the TSM group, 75.0 beats per minute ± 11.8 vs 79.9 beats per minute ± 10.2 [P < .0001]). CONCLUSION Intravenous gadoxetate disodium (a weight-based dose) does not cause changes in SpO2 and HR that lead to image quality degradation.

3 Tesla MRI detects accelerated hippocampal volume reduction in postmenopausal women

To clarify age‐related structural changes specific to hippocampal volume by hierarchizing according to age, gender, and menopausal status. Many studies report the neuroprotective effects of estrogen and age‐related brain volume changes; however, there are no studies regarding age‐related change specific to hippocampal volume in terms of age, gender, and menopausal status.

Idiopathic Normal-Pressure Hydrocephalus: Temporal Changes in ADC during Cardiac Cycle

PURPOSE To determine whether temporal changes in apparent diffusion coefficient (ADC) over the cardiac cycle are different in patients with idiopathic normal-pressure hydrocephalus (INPH) as compared with patients with ex vacuo ventricular dilatation and healthy control subjects. MATERIALS AND METHODS This prospective study was approved by the institutional review board and was performed only after informed consent was obtained from each patient. At 1.5 T, electrocardiographically triggered single-shot diffusion echo-planar magnetic resonance imaging (b = 0 and 1000 sec/mm(2)) was performed with sensitivity encoding and half-scan techniques to minimize bulk motion. ΔADC was defined as the difference between maximum and minimum ADC on a pixel-by-pixel basis over 20 phases of the cardiac cycle. Mean ADC during the diastolic phase and ΔADC in the frontal white matter were determined in patients with INPH (n = 13), patients with ex vacuo ventricular dilatation (n = 8), and healthy volunteers (n = 10). Kruskal-Wallis tests were used to determine significance between groups. RESULTS Mean ΔADC in the INPH group was significantly higher than that in the ex vacuo ventricular dilatation and control groups (P < .01 for both). There was no significant difference in ΔADC between the ex vacuo ventricular dilatation and control groups (P = .86). There was no significant difference in mean ADC during the diastolic phase among groups (P > .05 for all). There was no significant correlation between ΔADC and mean ADC during the diastolic phase in any group. CONCLUSION Determination of fluctuation of ADC over the cardiac cycle may render it possible to noninvasively obtain new and more detailed information than that provided by standard ADC measurement in suspected INPH, potentially facilitating the diagnosis of this disease.

Entorhinal cortex volume measured with 3T MRI is positively correlated with the Wechsler Memory Scale-Revised logical/verbal memory score for healthy subjects

IntroductionPrevious studies revealed a correlation between local brain volume and cognitive function. The aim of the present study was to investigate the correlation between local gray matter volume and the Wechsler Memory Scale-Revised (WMS-R) logical/verbal memory (WMS-R-verbal) score in healthy adults using a 3 Tesla magnetic resonance scanner and voxel-based morphometry (VBM).MethodsT1-weighted magnetic resonance images were obtained in 1,169 healthy adults. The T1-weighted images in native space were bias-corrected, spatially normalized, and segmented into gray matter, white matter, and cerebrospinal fluid images with Statistical Parametric Mapping 5. To investigate regionally the specific effects of the WMS-R-verbal score on the gray matter images, simple regression analysis was performed by VBM treating age, total intracranial volume, and gender as confounding covariates. A P value of less than 0.05 corrected with false discovery rate in voxel difference was considered to be statistically significant.ResultsOur study showed a significant positive correlation between the WMS-R-verbal score and the bilateral entorhinal cortex volume. In the right entorhinal, T value is 4.75, and the size of the clusters is 155 voxels. In the left entorhinal, T value is 4.08, and the size of the clusters is 23 voxels. A significant negative correlation was not found.ConclusionTo our knowledge, this is the first VBM study showing that entorhinal cortex volume is positively correlated with the WMS-R-verbal score for healthy subjects. Therefore, in our structural neuroimaging study, we add evidence to the hypothesis that the entorhinal cortex is involved in verbal memory processing.

Head Motion and Correction Methods in Resting-state Functional MRI

Resting-state functional magnetic resonance imaging (RS-fMRI) is used to investigate brain functional connectivity at rest. However, noise from human physiological motion is an unresolved problem associated with this technique. Following the unexpected previous result that group differences in head motion between control and patient groups caused group differences in the resting-state network with RS-fMRI, we reviewed the effects of human physiological noise caused by subject motion, especially motion of the head, on functional connectivity at rest detected with RS-fMRI. The aim of the present study was to review head motion artifact with RS-fMRI, individual and patient population differences in head motion, and correction methods for head motion artifact with RS-fMRI. Numerous reports have described new methods [e.g., scrubbing, regional displacement interaction (RDI)] for motion correction on RS-fMRI, many of which have been successful in reducing this negative influence. However, the influence of head motion could not be entirely excluded by any of these published techniques. Therefore, in performing RS-fMRI studies, head motion of the participants should be quantified with measurement technique (e.g., framewise displacement). Development of a more effective correction method would improve the accuracy of RS-fMRI analysis.