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Biomedical subjects

K Kichikawa

Publications and source records attributed to K Kichikawa.

60 records · Page 4Linked to original sources
PubMedDate not supplied

Age correlation of the time lag in signal change on EPI-fMRI.

PURPOSE: We measured the time lags between the start or end of tasks and signal changes in functional MRI (fMRI) for various age groups and evaluated the age correlation of the time lags. METHODS: Forty subjects, 20-76 years old, were evaluated. fMRI was performed with and echo planar imaging sequence at 0.5 s intervals. We measured the time for the signal of the precentral gyrus to make a half-maximal increase after starting the task (T-inc) and the time to reach the initial level after ceasing the task (T-dec). RESULTS: Average T-inc was 3.09 s and T-dec was 6.63 s. The values of T-inc could be correlated to age. T-dec had no age correlation. CONCLUSION: The time lag in fMRI was revealed to be prolonged with increasing age. Our results suggest that the time lag in fMRI is influenced by some factors associated with aging.

Adult↗
PubMedDate not supplied

MR and CT of tuberous sclerosis: linear abnormalities in the cerebral white matter.

A review of MR and CT images in five patients, 8 months to 22 years old, diagnosed as having tuberous sclerosis, revealed linear abnormalities in the cerebral white matter. A linear abnormality connecting a subependymal nodule to a subcortical lesion was shown in two patients as an area of hypointensity on T1-weighted MR images and as an area of hyperintensity on T2-weighted images. These appeared as faintly high-density areas on CT images. Seventeen linear abnormalities extending from the ventricle to the cortex with a subependymal nodule or subcortical lesion on each end were visible in all five patients as areas of hyperintensity on the T2-weighted images. On the T1-weighted images, only nine hypointense lines were noted. CT scans did not show these latter lines. Linear abnormalities in cerebral white matter are suggestive of lesions of demyelination, dysmyelination, hypomyelination, or lines of migration disorder. MR imaging, especially T2-weighted, is particularly sensitive in detecting these abnormalities.

Adolescent↗
PubMedDate not supplied

Improvement of T2-weighted images of central nervous system by motion artifact suppression technique (MAST).

Standard spin echo sequences of MRI with and without motion artifact suppression technique (MAST) were compared in 45 paired images of brain and 21 paired images of spine. The images were obtained on a Picker 1.5 T system with TR = 2 sec and TE = 100 or 120 msec. MAST is a method of refocusing transverse magnetization at echo time by modification of the gradient waveforms. Transverse, coronal, and sagittal planes of brain were compared in 10 paired images obtained from adults and five paired images from children. The spine was studied in sagittal images, 11 cervical images of adults, five lumbar images of adults, and five lumbar images of children. MAST was proven to be valuable not only for the detection of lesions but also for picturing anatomical details as in MR-cisternography and MR-myelography and the effects of iron ions. MAST improves significantly the quality of T2-weighted images, especially in children.

Brain↗
PubMedDate not supplied

Normal myelination of anatomic nerve fiber bundles: MR analysis.

PURPOSE: In order to establish milestones of brain maturation by MR imaging, we examined the initiation of myelination of fiber bundles and of surrounding white matter. METHODS: The subjects included 54 healthy infants ranging in age from 35 to 145 weeks by corrected gestational age. Images were obtained on a 1.5-T MR unit. In 24 sites of 18 fiber bundles in eight cross sections obtained perpendicular to the long axis of the brain stem, we analyzed the initiation of myelination and the age at which fiber bundles become indistinguishable owing to myelination of the surrounding white matter (blurring). RESULTS: The fiber bundles were classified into two groups on the basis of the presence or absence of blurring. The first group (no blurring) was further divided into group 1A, in which myelination began at 35 weeks or less, and group 1B, in which myelination began at 44 weeks or later. The second group (blurring) was divided into group 2A, in which myelination began at 35 weeks or less and blurring occurred at 43 to 49 weeks; group 2B, in which myelination started at 35 weeks or less and blurring began at 67 to 145 weeks; and group 2C, in which myelination began at 36 weeks or later and blurring occurred at 67 to 145 weeks. CONCLUSION: The time of blurring, when myelinated fiber bundles become indistinguishable from surrounding white matter owing to the initiation of myelination, is considered to be a useful parameter of brain maturation in infancy.

Brain↗
PubMedDate not supplied

Ultrasonographic screening for arterial occlusive disease in the pelvis and lower extremities.

PURPOSE: To evaluate the accuracy of pulsed Doppler ultrasound (PDUS) and color Doppler ultrasound (CDUS) for the screening of arterial occlusive disease in the pelvis and lower extremities. METHODS: We studied 52 patients with intermittent claudication or lower extremity "coolness." Pulsed Doppler waveforms were measured in the inguinal and popliteal regions and were classified according to their pattern. Patients with abnormal waveforms underwent subsequent CDUS evaluation from the aortic bifurcation to the popliteal arteries. All patients also underwent conventional angiography. RESULTS: All stenoses (> 50%) and occlusions on angiography were detected by PDUS. The combination of PDUS and CDUS allowed detection of 78.0% of stenotic lesions (> 50% narrowing) and 96.6% of occlusive lesions in the iliofemoral regions and in 100% of stenotic lesions (> 50% narrowing) and occlusive lesions in the femoropopliteal regions. PDUS required approximately 3 min. About more 5 min are required when CDUS was added. CONCLUSION: Combined PDUS and CDUS appears to be a rapid, highly sensitive means of screening for arterial occlusive disease in the pelvis and lower extremities.

Angiography↗