Search PubMed⌕ Search

Biomedical subjects

R Asato

Publications and source records attributed to R Asato.

85 records · Page 5Linked to original sources
PubMedDate not supplied

MR imaging of the sellar spine.

Magnetic resonance images of two cases of sellar spine are reported. The sellar spine is an anatomical variant characterized by an osseous spine that arises in the midline from the dorsum sellae and protrudes into the pituitary fossa. On short repetition time/short echo time (T1-weighted) images the sellar spine is demonstrated as a hypointense structure within the high intensity posterior pituitary. We suggest that the sellar spine is the ossified remnant of the cephalic tip of the notochord.

Adult↗
PubMedDate not supplied

MR imaging of a group I case of Hallervorden-Spatz disease.

Magnetic resonance (MR) imaging of a case of Hallervorden-Spatz disease (HSD) using a 1.5 T system is described. The patient showed progressive spastic diplegia with equinovarus deformity of the feet, dystonic postural movements, dysarthria, dysphagia, mental deterioration, optic nerve atrophy, and peripheral neuropathy. These clinical features were compatible with HSD. Symmetrical, decreased signal intensity was seen on both proton density weighted and T2-weighted spin echo images in the globus pallidus as well as in the substantia nigra (Group I). This MR finding suggests an increased iron deposition in these subcortical nuclei, which is characteristic of HSD. The characteristic MR imaging, together with the relevant clinical features, was considered to be useful for establishing the diagnosis of HSD.

Adult↗
PubMedDate not supplied

Hyperintense signal of the posterior pituitary on T1-weighted MR images: an experimental study.

The origin of the hyperintense signal (HIS) of the pituitary gland posterior lobe (PL) on T1-weighted magnetic resonance (MR) images was investigated. Six rabbits were imaged on a 1.5 T device before and after 2 weeks' feeding of hypertonic saline solution (phase I). Two were killed soon after the second imaging; the pituitary gland was examined histochemically for neurosecretory granules containing antidiuretic hormone (ADH). The other four rabbits were given regular water for another 2 weeks (phase II) and then were again imaged. The plasma ADH level was monitored at each imaging session. In all subjects, the signal intensity of the PL decreased at the end of phase I, and the HIS reappeared at the end of phase II. The neurosecretory granules in the PL significantly diminished in number in phase I. Plasma ADH levels significantly increased in phase I and returned to their normal range in phase II. These clear correlations between MR findings and hormonal and histochemical results strongly suggest that the source of the HIS of the PL is the neurosecretory granules containing ADH.

Animals↗
PubMedDate not supplied

Fatty filum terminale: assessment with MR imaging.

Five cases of fatty filum terminale were encountered in a retrospective analysis of 332 routine lumbosacral magnetic resonance studies. The T1-weighted and GRASS images were particularly useful in evaluating the filum. An irregularly thickened fatty filum, especially if associated with a low conus, is likely to be pathologic and responsible for a patient's symptoms and signs.

Adult↗
PubMedDate not supplied

White matter hyperintensities may correspond to areas of increased blood volume: correlative MR and PET observations.

A method for correlating positron emission tomography with magnetic resonance (MR) imaging enabled the authors to examine the high intensity white matter areas in T2-weighted images in patients with internal carotid artery occlusion. The high intensity areas showed increased cerebral blood volume compared with the ipsilateral and contralateral normal intensity white matter. This observation may have relevance in explaining some of the patchy white matter lesions seen in MR images.

Aged↗
PubMedDate not supplied

"Fogging effect" in MR of cerebral infarct.

In a case of cerebral infarction the lesions were isointense to slightly hyperintense in the T2-weighted MR images obtained approximately 2 weeks after the onset. Earlier (1 week after onset), they had been markedly hyperintense. The probably mechanisms behind this phenomenon, referred to as "MR fogging" are discussed.

Aged↗
PubMedDate not supplied

Differentiation of suprasellar nonneoplastic cysts from cystic neoplasms by Gd-DTPA MRI.

Magnetic resonance imaging in 9 cases of surgically confirmed nonneoplastic intra- and/or suprasellar cysts was analyzed and compared with that from 17 cases of craniopharyngioma and 12 of cystic pituitary adenoma. Signal intensity did not help in distinguishing nonneoplastic cysts from cystic neoplasms. No postcontrast (Gd-DTPA) cyst wall enhancement was observed among the nonneoplastic cysts, although all 6 craniopharyngiomas and 12 cystic pituitary adenomas that underwent postcontrast study did enhance. Three nonneoplastic cysts were surrounded by the pituitary gland, thus mimicking wall enhancement in the postcontrast studies. Rapid enhancement in the early postcontrast-administration phase (dynamic studies) helped avoid confusion between the normal pituitary tissue and cyst wall enhancement. Magnetic resonance studies with contrast enhancement play an essential role in differentiating nonneoplastic cysts from cystic neoplasms in the sella region.

Adenoma↗
PubMedDate not supplied

Contrast enhanced area of posterior pituitary gland in early dynamic MRI exceeds hyperintense area on T1-weighted images.

Seventeen normal pituitary glands were studied by midline sagittal (and in one case axial) dynamic MRI before and immediately after injection of Gd-DTPA, using spin-echo sequences with a short repetition time. Images were obtained at 1 min intervals for 6 min at 1.5 T. A well-defined focal area with marked enhancement was seen in the posterior portion of the pituitary gland on the first image after injection of Gd-DTPA. The size of the early enhancing area in the posterior pituitary (EEPP) was compared with the high signal of the posterior pituitary (HSPP) on the precontrast image. The EEPP was larger than the HSPP in 10 cases (59%). The two were equal in size in seven cases (41%). The EEPP was anteriorly convex in 11 cases (65%), whereas HSPP was anteriorly convex in 4 cases (24%). We believe that EEPP closely represents the real extent of the posterior lobe. Our results support the hypothesis that HSPP may involve only a portion of the posterior pituitary.

Contrast Media↗
PubMedDate not supplied

Degeneration of the posterior columns of the spinal cord: postmortem MRI and histopathology.

Postmortem MR images of two cases of posterior column degeneration were correlated with histopathological findings. The abnormal MR findings were volume loss and high signal intensity of the posterior columns associated with mild deformity of the dorsal surface of the spinal cord, corresponding to tract degeneration on histopathological examination. These results strongly suggest that further development of MR technique will permit in vivo detection of posterior column degeneration.

Adult↗
PubMedDate not supplied

Chronological sequences and blood-brain barrier permeability changes in local injury as assessed by nuclear magnetic resonance (NMR) images from sliced rat brain.

Two experiments were done with a prototype mini-NMR imager to evaluate the potential application of nuclear magnetic resonance (NMR) imaging in neuropathology. Cryo-injury-induced brain edema in brain slices from 22 adult male rats was imaged for observing the chronological sequences. Blood-brain barrier permeability changes were evaluated in 12 other brain slice images. EDTA-2Na-Mn solution was intravenously injected as an indicator of blood-brain barrier permeability. Contrast enhancement was achieved by changing the NMR imaging parameters. High resolution imaging permitted visualization of the corpus callosum, the thickness of which was only 0.2-0.4 mm. The extent of edema in gray matter was clearly shown with a striking contrast; no consistent findings were seen with slight differences in water content between edema and the surrounding normal cortex. As a result, the chronological sequences of brain edema were clearly observed. Mn-EDTA leaking from the circulating blood through the damaged capillary wall had a "paradoxical enhancement" effect on the NMR images; this effect might be suitable for evaluating blood-brain barrier permeability changes in NMR images.

Animals↗
PubMedDate not supplied

Three-dimensional MR vascular imaging of the spine using gadolinium-DTPA.

To investigate the fine vascular structures in the spinal and paraspinal region, the authors performed three-dimensional GRASS scanning after the administration of contrast material. The scan sequence was sagittal volume scan, TR/TE 100/16, with a flip angle of 45 degrees. First-order gradient moment nulling was employed. Four normal volunteers and 31 patients were studied. Using this technique, longitudinal anterior epidural veins and vertebral arteries were clearly identified. Paraspinal fine vessels of slow to moderate flow, including dilated anterior spinal artery, radiculo-medullary vein, and perimedullary coronal venous plexus, were demonstrated in pathological cases. In addition, with processing of the volume data set, phlebographic projection images of the ladder-shaped anterior epidural venous system could be generated. This method provided more detailed information on epidural and intradural vessels than conventional MR imaging.

Contrast Media↗
PubMedDate not supplied

High-resolution MR of the spinal cord in humans and rats.

Human and rat cervical spinal cords were imaged with high-resolution spin-echo and inversion-recovery pulse sequences in an experimental 1.9-T MR system. The gross morphology of the cord was easily discernible in fresh and fixed specimens, including the white and gray commissures, dorsal and ventral horns, and lateral and posterior funiculi. The T1, T2, and spin-density values for gray and white matter were determined from these images and were found to be 914 msec, 114 msec, and 71% for white matter other than the dorsal columns, and 946 msec, 87 msec, and 80% for gray matter in human spinal cords. These values are reduced considerably after formalin fixation: T1 to 56% (white matter) and 54% (gray matter) of prefixation values, T2 to 52% (white matter) and 70% (gray matter) of fresh values, and spin density to 90% (white matter) and 96% (gray matter) of prefixation values. Interestingly, the central gray matter demonstrates higher signal intensity than the white matter on both short and long TR/TE images. This intensity difference was observed for both human and rat spinal cords, before and after fixation, and can be explained by the relatively small T1 differences between gray matter and white matter and the gray matter-white matter spin-density ratios: 1.127 for fresh and 1.203 for fixed specimens.

Animals↗