Biomedical subjects

Toshiyuki Okubo

Publications and source records attributed to Toshiyuki Okubo.

7 recordsLinked to original sources

PubMed2003

Hemangiomas in the face and extremities: MR-guided sclerotherapy--optimization with monitoring of signal intensity changes in vivo.

The feasibility of a method of magnetic resonance (MR)-guided sclerotherapy for hemangioma was evaluated. The distribution of a test injection and a contiguous sclerosant injection was monitored clearly with MR fluoroscopy. Postsclerotherapy T2-weighted MR images depicted areas with and those without effective sclerosant concentration, which enabled performance of selective supplemental sclerotherapy. This method of MR-guided sclerotherapy seems feasible for clinical application.

Adolescent↗

PubMed2003

T1-weighted fluid-attenuated inversion recovery at low field strength: a viable alternative for T1-weighted intracranial imaging.

BACKGROUND AND PURPOSE: T1-weighted spin-echo imaging has been widely used to study anatomic detail and abnormalities of the brain; however, the image contrast of this technique is often poor, especially at low field strengths. We tested a new pulse sequence, T1-weighted fluid-attenuated inversion recovery (FLAIR), which provides good contrast between lesions, surrounding edematous tissue, and normal parenchyma at low field strengths and at acquisition times comparable to those of T1-weighted spin-echo imaging. METHODS: Thirteen patients with brain lesions underwent T1-weighted spin-echo and T1-weighted FLAIR imaging during the same imaging session. T1-weighted spin-echo and T1-weighted FLAIR images were compared on the basis of four quantitative (lesion-white matter [WM] contrast-to-noise ratio [CNR], lesion-CSF CNR, gray matter-WM CNR, and WM-CSF CNR) and three qualitative criteria (conspicuousness of lesions, image artifacts, and overall image contrast). RESULTS: CNRs obtained with T1-weighted FLAIR were comparable but statistically superior to those obtained with T1-weighted spin-echo imaging. In general, T1-weighted FLAIR and T1-weighted spin-echo imaging produced comparable image artifacts. Conspicuousness of lesions and the overall image contrast were judged to be superior on T1-weighted FLAIR images. CONCLUSION: T1-weighted FLAIR imaging may be a valuable alternative to conventional T1-weighted imaging, because the former technique offers superior image contrast at low field strengths and comparable acquisition times.

Adult↗

PubMed2003

[Improving diffusion-weighted imaging of liver with SENSE technique: a preliminary study].

Diffusion-weighted imaging (DWI) has not commonly been performed for assessment of the liver because of technical and physiologic problems. The sensitivity-encoding (SENSE) technique enables the acquisition time to be shortened and reduces artifacts on DWI. We compared the DWI without SENSE, with SENSE only, and with SENSE and half-Fourier technique using a 1.5 Tesla MRI unit. In general, imaging quality was improved and fewer artifacts were observed in DWI with SENSE. DWI of liver with SENSE is expected to be a useful tool for clinical application.

Aged↗

PubMed2002

Optimal inversion time for acquiring flow-sensitive alternating inversion recovery images to quantify regional cerebral blood flow.

The purpose of this study was to correlate regional cerebral blood flow (rCBF) measured by I-123-IMP and flow-sensitive alternating inversion recovery (FAIR) studies with different inversion time (TI) values to find out the optimum TI that gives comparable rCBF and images on FAIR study. Nine patients with symptoms and signs of internal carotid or major cerebral arterial stenosis were enrolled in this study. Both I-123-IMP single photon emission computed tomography (SPECT) and FAIR images were acquired in all patients. Single-slice FAIR images (with different TI values) were acquired using a 1.5-T MRI unit. The rCBF was calculated from all I-123-IMP and FAIR images. Receiver operating characteristics (ROC) analysis was performed to detect hypoperfused segments on FAIR images. The rCBF calculated from FAIR and I-123-IMP studies were compared and correlated with each other. The ROC analysis showed no significant differences among the readers or TI values, but a trend of higher sensitivity, specificity, and accuracy was observed with TI of 1400 ms. The rCBF values of FAIR and I-123-IMP studies significantly correlated with each other. The FAIR images with TI value of 1400 ms gave more comparable CBF. A TI value of 1400 ms might be optimum for 1.5-T MR strength to get high quality FAIR images and comparable CBF.

Aged↗

PubMed2002

Radiation-induced arteritis: thickened wall with prominent enhancement on cranial MR images report of five cases and comparison with 18 cases of Moyamoya disease.

PURPOSE: To evaluate magnetic resonance (MR) imaging findings of radiation-induced cranial arteritis regarding arterial wall thickening and degree of enhancement, as well as to compare the findings with those of idiopathic moyamoya disease. MATERIALS AND METHODS: We reviewed cerebral MR images in five patients with radiation-induced large cerebral arteritis. All patients had undergone irradiation 2-25 years prior to this study. Conventional nonenhanced MR, MR angiographic, and contrast material-enhanced MR images were evaluated. Special attention was paid to wall enhancement of the affected arteries (distal internal carotid artery). Wall enhancement was staged in three levels by two neuroradiologists. We also reviewed MR images in 18 patients with primary moyamoya disease for comparison and analyzed them statistically (Fisher exact test). RESULTS: Wall thickening and prominent ring enhancement of the wall of the affected large cerebral arteries were observed in all (five of five) patients with radiation-induced arteritis. In contrast, wall thickening and prominent ring enhancement of the wall of the occluded arteries either were not seen (13 of 18 patients) or were faint (five of 18 patients) in patients with moyamoya disease. Contrast enhancement of the arterial walls in patients with radiation-induced arteritis was significantly more prominent than in patients with moyamoya disease (P =.003). CONCLUSION: MR images of wall thickening and prominent ring enhancement of the wall of affected large cerebral arteries may be a diagnostic clue in differentiating radiation-induced arteritis from moyamoya disease.

Adolescent↗

PubMed2002

[Line scan diffusion weighted imaging (LSDI) on 0.2 Tesla MRI of the normal cervical cord in vivo: preliminary study].

Diffusion weighted imaging(DWI) has been widely performed in the brain. However, DWI of the spinal cord is rarely performed because of technical and physiologic problems. Line scan diffusion weighted imaging(LSDI) is spin-echo based and relatively insensitive to susceptibility artifacts. We calculated the apparent diffusion coefficient(ADC) values of the normal cervical spinal cord by LSDI on a 0.2 Tesla MR imager and compared the ADC values with those from 1.5 Tesla MRI previously reported in the literature. The ADC values were adequate, and LSDI on 0.2 Tesla MRI is expected to become a useful tool for clinical application.

Adult↗

PubMedDate not supplied

Normal aging in the central nervous system: quantitative MR diffusion-tensor analysis.

The purpose of this study is to elucidate changes in mean diffusivity (ADC) and fractional anisotropy (FA) using MR diffusion tensor imaging (DTI) in the central nervous system during normal aging. We studied 50 normal volunteers (30 men, 20 women; mean age 44.8 +/- 14.0; age range, 21-69 years) without disorders affecting the central nervous system. The frontal, parietal white matter, lentiform nucleus, posterior limb of internal capsule, thalamus, genu and splenium of the corpus callosum were selected for investigation. There was no significant difference in ADC or FA between male and female or between the right and left hemisphere. A significant ADC increase with advancing age was observed in frontal white matter (P = 0.010) and lentiform nucleus (P = 0.022). A significant FA decline was found only in the genu of the corpus callosum (P < 0.001) with advancing age. Quantitative diffusion tensor analysis correlate with normal aging and may help in assessing normal age-related changes and serve as a standard for comparison with neurodegenerative disorders.

Adult↗