Makoto Obara

Salivary Gland Tumors: Use of Intravoxel Incoherent Motion MR Imaging for Assessment of Diffusion and Perfusion for the Differentiation of Benign from Malignant Tumors

PURPOSE To prospectively evaluate the intravoxel incoherent motion (IVIM) parameters (microvascular volume fraction, f; pure diffusion coefficient, D; and perfusion-related incoherent microcirculation, D*) for differentiating between benign and malignant salivary gland tumors. MATERIALS AND METHODS All participants in this prospective institutional review board-approved study provided written informed consent. The perfusion and diffusion of 20 (65%) benign (12 pleomorphic adenomas and eight Warthin tumors) and 11 (35%) malignant salivary gland tumors were assessed on the basis of the IVIM theory. Diffusion-weighted magnetic resonance imaging was performed by using 11 b values (0-800 sec/mm(2)). The IVIM parameters of the salivary gland tumors were determined by a radiologist, and significant differences between the tumor types were assessed by using the Steel-Dwass test. RESULTS The f values of Warthin tumors (0.156 ± 0.039 [standard deviation]) were significantly larger than those of pleomorphic adenomas (0.066 ± 0.031) (P = .003). The D values of malignant tumors (0.96 × 10(-3) mm(2)/sec ± 0.22) were significantly different from those of benign tumors (pleomorphic adenomas, 1.38 × 10(-3) mm(2)/sec ± 0.30 [P = .002]; Warthin tumors, 0.61 × 10(-3) mm(2)/sec ± 0.11 [P = .005]). The D* values of malignant tumors (21.99 × 10(-3) mm(2)/sec ± 19.01) were significantly smaller than those of Warthin tumors (42.64 × 10(-3) mm(2)/sec ± 20.17) (P = .022). The combination of D and D* criteria provided the best diagnostic accuracy (100%) for differentiation among the three tumor types. CONCLUSION IVIM imaging may be helpful for differentiation between benign and malignant salivary gland tumors.

Relation of bimanual coordination to activation in the sensorimotor cortex and supplementary motor area: Analysis using functional magnetic resonance imaging

The aim of this study was to analyze how functional activation in the supplementary motor area (SMA) and sensorimotor cortex (SMC) is related to bimanual coordination using functional magnetic resonance imaging. Subjects included 24 healthy volunteers, 15 of whom were right-handed and 9 left-handed. Three kinds of activation tasks, all of which required the repetitive closing and opening of a fist, were performed: unimanual movement of the nonpreferred hand (task A); simultaneous, agonistic movement of both hands (task B); simultaneous, antagonistic movement of both hands (task C). The SMA activation during task C was more pronounced than that during the other two tasks for right and left handers. The results suggested that the activation of the SMA, at least during a simple motion used in the present study, was little influenced by whether the motion was unimanual or bimanual but instead how the bimanual motion was composed of the motion element of a single hand. The SMC activation during task C was significantly larger than that during task B, whereas hemispheric differences in the activation were not found. This indicated that the complexity of the bimanual movement also affected the SMC activation.

Ultra-short echo time (UTE) MR imaging of the lung: Comparison between normal and emphysematous lungs in mutant mice

To investigate the utility of ultra‐short echo time (UTE) sequence as pulmonary MRI to detect non‐uniform disruption of lung architecture that is typical of emphysema.

Dynamic Oxygen-Enhanced MRI Versus Quantitative CT: Pulmonary Functional Loss Assessment and Clinical Stage Classification of Smoking-Related COPD

OBJECTIVE The purpose of the present study is to prospectively compare the capability of dynamic oxygen-enhanced MRI and quantitative CT for pulmonary functional loss assessment and clinical stage classification of smoking-related chronic obstructive pulmonary disease (COPD). SUBJECTS AND METHODS Ten nonsmoking and 61 consecutive smoking-related COPD subjects underwent dynamic oxygen-enhanced MRI, CT, and pulmonary function tests. COPD subjects were classified into four clinical stages on the basis of the ATS-ERS guidelines. Wash-in time and relative enhancement ratio maps were generated by pixel-by-pixel analyses. Mean wash-in time and relative enhancement ratio were determined as averages of region of interest (ROI) measurements. CT-based functional lung volumes were measured on quantitative CT using the density-masked CT technique. For comparison of assessment capability for smoking-related functional loss, the three parameters were correlated with the percentage predicted forced expiratory volume in 1 second (%FEV1) and the percentage predicted diffusing capacity of the lung for carbon monoxide corrected for alveolar volume (%DL(CO)/VA). To determine the clinical stage classification capability, these parameters were statistically compared for nonsmoking subjects and all clinical stages of smoking-related COPD subjects. RESULTS Correlation between mean wash-in time and %FEV1 (r = -0.74, p < 0.0001) and between mean relative enhancement ratio and %DL(CO)/VA (r = 0.66, p < 0.0001) was better than that between CT-based functional lung volume and either %FEV1 (r = 0.61, p < 0.0001) or %DL(CO)/VA (r = 0.56, p < 0.0001). Mean wash-in time showed a significant difference between nonsmoking and smoking-related COPD subjects at all clinical stages (p < 0.05). CONCLUSION Dynamic oxygen-enhanced MRI has potential for pulmonary functional loss assessment and clinical stage classification of smoking-related COPD as does quantitative CT.

Clinical utility of apparent diffusion coefficient values obtained using high b-value when diagnosing prostate cancer using 3 tesla MRI: Comparison between ultra-high b-value (2000 s/mm2) and standard high b-value (1000 s/mm2)

To determine whether the apparent diffusion coefficient (ADC) obtained using b = 2000 s/mm2 upon 3 Tesla (T) diffusion‐weighted MRI is superior to b = 1000 s/mm2 for discriminating malignant from normal prostate tissue and predicting the aggressiveness of prostate cancer, using histopathological findings of radical prostatectomy as a reference.

Activation of Pre–Supplementary Motor Area (SMA) and SMA Proper During Unimanual and Bimanual Complex Sequences: An Analysis Using Functional Magnetic Resonance Imaging

Several functional imaging studies have shown that the extent of activation and percentage change in cerebral blood flow in the supplementary motor area (SMA) during a bimanual mirror performance of a simple repetitive movement are almost identical to those during a unimanual movement. The aim of this study was to investigate whether this finding was also applicable to a more complex movement. Eight right‐handed, healthy volunteers performed unimanually (with their right and left hands) and bimanually (in a mirror fashion) thumb‐finger opposition in a nonconsecutive order (index‐middle‐index‐ring‐index‐little‐index‐middle… fingers). The SMA proper was more activated during the bimanual movement than the unimanual movement with either hand. This is in accordance with the hypothesis that bimanual movement, even in a mirror fashion, is more difficult than unimanual movement when the task is complex but not when the task is simple. Pre‐SMA was inconsistently activated. The results suggest that the SMA proper plays an active role in executive processing during bimanual mirror performance of complex movements.

MR prediction of liver fibrosis using a liver-specific contrast agent: Superparamagnetic iron oxide versus Gd-EOB-DTPA.

To examine whether the uptake of a liver‐specific contrast agent in the liver parenchyma was correlated with the degree of liver fibrosis.

Ultra‐high b‐value diffusion‐weighted MRI for the detection of prostate cancer with 3‐T MRI

To determine, with histopathological findings of radical prostatectomy as reference, whether diffusion‐weighted imaging (DWI) using b = 2000 s/mm2 for 3‐T magnetic resonance imaging (MRI) is superior to the use of b = 1000 s/mm2 for prostate cancer detection.

Quantitative analysis of liver function using superparamagnetic iron oxide- and Gd-EOB-DTPA-enhanced MRI: Comparison with Technetium-99m galactosyl serum albumin scintigraphy

PURPOSE To examine whether or not the parameters regarding the signal intensity of the liver parenchyma on superparamagnetic iron oxide (SPIO)- and gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced MRI are correlated with the parameters of Technetium-99m galactosyl serum albumin ((99m)Tc-GSA) scintigraphy. MATERIALS AND METHODS This retrospective study consisted of 55 and 33 patients who underwent SPIO- and Gd-EOB-DTPA-enhanced MRI in addition to (99m)Tc-GSA scintigraphy, respectively. For each patient, we calculated Pre R2* and Pre R2, which are equivalent to R2* (=1/T2*) and R2 (=1/T2) values of the liver parenchyma; ΔR2* and ΔR2, which represent differences in R2* and R2 values of the liver parenchyma before and after administration of SPIO; and the increase rates of both the liver-to-spleen signal intensity ratio (LSR) and the liver-to-major psoas muscle signal intensity ratio (LMR) on the hepatobiliary phase compared with the precontrast image. For (99m)Tc-GSA scintigraphy, the receptor index LHL15 and the blood clearance index HH15 were recorded. RESULTS Regression analysis showed a moderate correlation between Pre R2* and LHL15 (P<0.05). Mild to moderate correlations were also obtained between any combination of ΔR2* and ΔR2 on the one hand, and LHL15 and HH15 on the other (P<0.05). There were moderate correlations between any combination of increase rates of LSR and LMR on the one hand, and LHL15 and HH15 on the other (P<0.05-0.001). CONCLUSION Pre R2*, ΔR2*, ΔR2 and the increase rates of LSR and LMR could be used as quantitative indicators of liver function.

Pharmacokinetic analysis based on dynamic contrast-enhanced MRI for evaluating tumor response to preoperative therapy for oral cancer

To evaluate whether a pharmacokinetic analysis is useful for monitoring the response of oral cancer to chemoradiotherapy (CRT).