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Biomedical subjects

R Asato

Publications and source records attributed to R Asato.

At least 73 records · Page 4Linked to original sources
PubMed1982

[Nuclear magnetic resonance (NMR) imaging of brain edema from sliced rat brain: preliminary report].

A series of the sliced rat brain were imaged by proton nuclear magnetic resonance (1H-NMR) using a Carr-Purcell-Meiboom-Gill sequence. The slices were obtained from the adult male Wistar rats, normal or suffering from vasogenic brain edema at 2, 6, 24Hr, 2Wk and 2Mo period after the application of cryo-injury. The imaging time was arranged 17 to 22 minutes dependently upon signal to noise ratio. The slice thickness was 1.2 mm, and pixel dimensions were 0.2 X 0.2 mm. Whereas a voxel size in our images is mere 1/1,200 compared to that reported about the prototype human NMR imaging devices, high resolution has been realized. The spatial resolution is very fine, as evidenced by the appearance of major internal structures of rat brain, and the object contrast is so high that cerebral white-gray contrast is excellent, although the difference in water concentration between them is only 7%. It has been impossible to measure serially in vivo change in water concentration of small organs as rat brain, NMR has the capability to generate images in response to tissue state of hydration, therefore we can easily recognize the extent and intensity of the brain edema, which has been defined as an expansion of the brain volume resulting from an increase in its fluid content. And in this study, using the prototype mini-NMR-CT of excellent spatial and contrast resolution, we have been able to show this advantage of NMR as a new tool for research in the field of neurological surgery.

Animals↗
PubMed1977

Abducens nerve palsy as initial symptom of trigeminal schwannoma.

The insidious onset and slow progression of symptoms may cause delay in the recognition of trigeminal schwannomas. Two cases with abducens nerve palsy as an initial symptom are reported, in both of whom the tumour was growing mainly below and anterior to the intracavernous portion of the internal carotid artery. Early detection of clinical symptoms and thorough radiological investigations are important in the early diagnosis of these lesions.

Abducens Nerve↗
PubMed1977

Surgical treatment of intracranial hematoma and hydrocephalus in an infant with hemophilia A.

A seven-month0old hemophiliac infant developed intracerebral, subdural and intraventricular hematomas and hydrocephalus. Removal of hematomas and placement of ventriculoperitoneal shunt could be performed quite safely even in an infant under the cover of highly potent human antihemophilic factor concentrate. Computerized tomography is very useful for neurosurgical care of the hemophiliac patients as a noninvasive and atraumatic method of examination. Intracranial bleeding is listed as the most common cause of death among hemophiliacs. The literature of intracranial operations on the patients with hemophilia A is reviewed.

Cerebral Hemorrhage↗
PubMedDate not supplied

Uterine contractions: possible diagnostic pitfall at MR imaging.

A total of 206 nongravid patients with various gynecologic problems underwent pelvic magnetic resonance (MR) examinations that included both sagittal T2-weighted and contrast agent-enhanced T1-weighted images. MR images were retrospectively reviewed to identify changes in endometrial configuration on serial images obtained during the same MR examination. In 20 MR examinations (all in women of reproductive age), endometrial distortion due to myometrial bulging was noted on T2-weighted or contrast-enhanced T1-weighted images. It was absent on other MR images obtained at different times. Myometrial bulging exhibited low signal intensity in 18 examinations. The finding resembled adenomyosis or leiomyoma on T2-weighted or contrast-enhanced T1-weighted images. These results evidence the presence of transient myometrial bulging and transient low-intensity myometrium in the nongravid uterus. This phenomenon is thought to represent uterine contraction. Clinicians should be aware of the potential presence of transient low-signal-intensity myometrial bulging that could present diagnostic problems in the normal uterus.

Adolescent↗
PubMedDate not supplied

Intracranial contour extraction with active contour models.

A novel image processing scheme for extracting the intracranial contours in axial magnetic resonance data sets is proposed. The scheme incorporates the method of active contour models, a recently introduced paradigm for contour extraction. Its performance is nearly ideal for T2-weighted images. Although the performances for proton-density-weighted images and T1-weighted images drop slightly, qualitatively satisfactory extraction still can be obtained for T1-weighted images. Due to high degree of automation, the scheme should help speed up some image processing applications that require the presegmentation of the intracranial cavity.

Artifacts↗
PubMedDate not supplied

123I-IMP SPECT findings in mitochondrial encephalomyopathies.

We performed N-isopropyl-[123I]p-iodoamphetamine (IMP) single photon emission computed tomography (SPECT) in three patients with Leigh syndrome, two patients with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS), and two siblings with progressive external ophthalmoplegia (PEO). The SPECT images were compared with the findings on magnetic resonance imaging (MRI) and computed tomography (CT). All Leigh syndrome patients showed low accumulation areas (LAA) bilaterally in the frontal lobes and the basal ganglia. The frontal lobe LAA was seen even in an area without abnormalities on CT/MRI. Each MELAS patient showed a focal LAA. SPECT could also detect an old stroke-like lesion that was no longer shown by CT/MRI. However, SPECT did not show LAA in the basal ganglia, which showed calcification on CT or abnormal signal intensity on MRI. MRI in the 2 PEO patients showed lesions bilaterally in the basal ganglia in one, and in the internal capsules in the other. SPECT showed LAA not only in corresponding areas, but also in the occipital lobes, where no lesions were revealed by MRI. Thus, 123I-IMP SPECT was more sensitive than CT/MRI for detecting stroke-like lesions in MELAS patients, although it did not detect small lesions in the basal ganglia. LAA in the frontal lobes and occipital lobes may be SPECT findings characteristic of Leigh syndrome and PEO, respectively.

Adolescent↗
PubMedDate not supplied

Nontraumatic spinal intramedullary hemorrhage in an infant.

After an uncomplicated pregnancy and delivery, this female child suddenly became quadriplegic on the fifth day of life. She gradually regained movement in her upper extremities. At 2 months of age, she exhibited paraplegia with exaggerated deep tendon reflexes in the lower extremities. Babinski reflex was present bilaterally and sensory disturbances below the trunk were suspected. Somatosensory evoked potentials after median and ulnar nerve stimulation revealed preserved conduction from the upper extremities through the cervical spinal cord to the cortex. Somatosensory evoked potentials after posterior tibial nerve stimulation suggested disturbed conduction in the upper thoracic spinal cord. Magnetic resonance imaging disclosed a hypodense area in the thoracic cord between T1 and T4 on both the T1-weighted and gradient echo images consonant with an old hematoma cavity. Digital subtraction angiography failed to demonstrate any vascular malformation.

Evoked Potentials, Somatosensory↗
PubMedDate not supplied

MRI in infantile neuroaxonal dystrophy.

A 6-year-old boy with the typical clinical features of infantile neuroaxonal dystrophy was examined with magnetic resonance imaging. The findings suggested increased metal deposition in the globus pallidus. Magnetic resonance imaging findings of Hallervorden-Spatz syndrome and infantile neuroaxonal dystrophy are similar, suggesting that these two disease entities overlap. Magnetic resonance imaging findings, as well as relevant clinical features, may be useful in the diagnosis and classification of infantile neuroaxonal dystrophy.

Basal Ganglia Diseases↗
PubMedDate not supplied

Early diagnosis of leukoencephalopathy of acute lymphocytic leukemia by MRI.

Using repeated computed tomographic and magnetic resonance imaging scans, we examined 8 patients with acute lymphocytic leukemia during remission induction therapy between 1988 and 1989. In 3 patients, leukoencephalopathy was diagnosed by T2-weighted magnetic resonance imaging. In 1 patient, leukoencephalopathy was progressive and irreversible brain damage and mental retardation persisted. In the other 2 patients, hyperintense lesions in the periventricular white matter were transient and no neurologic sequelae ensued. Magnetic resonance imaging was more useful than computed tomography in the early diagnosis and management of these acute lymphocytic leukemia patients with leukoencephalopathy.

Antineoplastic Combined Chemotherapy Protocols↗
PubMedDate not supplied

Somatosensory evoked potentials after posterior tibial nerve stimulation in focal spinal cord diseases.

We investigated the somatosensory evoked potentials (SEPs) produced by posterior tibial nerve (PTN) stimulation in 8 infants and children with focal spinal cord disorders. The spinal responses of the PTN-SEPs were considered to assist in the localization of spinal lesions because their abnormalities were consistent with the neurologic and/or radiologic findings in all 6 examinations that revealed abnormal spinal SEPs. The cortical responses correlated significantly with proprioception in the lower limbs because proprioception was only disturbed when the cortical SEPs were absent (3 examinations). When both the spinal and cortical responses were abnormal, the spinal lesion probably involved the dorsal column so extensively that it completely interrupted the afferent impulses. In contrast, when SEP studies demonstrated abnormal spinal and normal cortical SEPs (3 examinations), the dorsal column involvement was probably less severe; therefore, both the spinal and cortical responses provided useful information regarding afferent conduction in the dorsal column. PTN-SEPs appear to have the potential to be of value in the diagnosis of focal spinal disease, especially in infants and young children who cannot cooperate with detailed neurologic examinations.

Child↗
PubMedDate not supplied

Epidural venous system (meningorachidian venous plexus) in juvenile amyotrophy of distal upper extremity: assessment with GD-DTPA enhanced volumetric MR study.

The epidural venous system (meningorachidian venous plexus) was analyzed utilizing gadolinium-diethylenetriamine pentaacetic acid (DTPA) (Gd-DTPA) enhanced volumetric magnetic resonance (MR) images in 11 patients with focal cervical spinal cord atrophy, clinically consistent with juvenile amyotrophy of distal upper extremity. In our series, all of the patients showed unusual posterior epidural venous enhancement at the C5-6 level, suggesting posterior epidural venous dilatation. Three patients also showed prominent dilatation of cervico-thoracic epidural veins surrounding the thecal sac. These MR findings were also demonstrated by spinal phlebography. Gd-DTPA enhanced MR images, especially high resolutional volumetric MR images, were efficient for evaluating these vessels. The observation of meningorachidian venous plexus along the disease course should be necessary for searching the pathogenesis of this disease.

Adolescent↗
PubMedDate not supplied

Anterior and posterior lobes of the pituitary gland: assessment by 1.5 T MR imaging.

Pituitary glands of 60 normal volunteers (30 men 20-36 years old, and 30 women 18-42 years old) were studied by 1.5 T magnetic resonance (MR) imaging. The T1-weighted images (T1WI) [repetition time (TR) = 400 ms; echo time (TE) = 25 ms] were obtained in the coronal, sagittal, and axial planes. Proton density (PD)/T2-weighted images (PDWI/T2WI) (TR = 2,000 ms; TE = 25/100 ms) were obtained in the sagittal plane using 3 mm slice thickness. On T1WIs of all subjects the posterior part (PP) of the pituitary fossa showed the highest signal, which was indistinguishable from fatty tissue. This study reveals that this region of high signal intensity (PP) corresponds to the posterior lobe and not intrasellar fat because its shape, size, and position are compatible with the posterior lobe; its signal intensity differs from that of fatty tissue on PDWI and T2WI; the absence of an intrinsic chemical shift artifact (CSA) characteristic of fat; and due to CSA, a dorsum with fatty marrow is shifted relative to the PP (or may be made to merge with it). Regarding the differentiation of the two lobes of the pituitary gland on MR, the morphology of the anterior and posterior lobes was evaluated and great variation found. Appreciation of normal is particularly important in evaluating coronal images for small pituitary lesions.

Adolescent↗
PubMedDate not supplied

Posterior lobe of the pituitary in diabetes insipidus: MR findings.

The posterior lobe of the pituitary gland was evaluated by 1.5 T magnetic resonance (MR) in five cases of diabetes insipidus (DI), including one primary (idiopathic) and four secondary DI cases due to germinomas (two), teratoma (one), and histiocytosis X (one). The normal posterior lobe displays high signal indistinguishable from fatty tissue on T1-weighted images (T1WI) (short T1 value). In all five DI cases the normal high signal of the posterior lobe was not detected in the pituitary fossa on T1WI. Hence, because of this characteristic finding, MR may greatly assist in the diagnosis of DI. We may speculate that the short T1 value of the posterior lobe is closely related to its functional integrity and may be due to the neurosecretory materials in the axons of the hypothalamohypophyseal tract.

Adolescent↗