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Biomedical subjects

S Saiwai

Publications and source records attributed to S Saiwai.

18 recordsLinked to original sources
PubMed1992

[Gd-DTPA-enhanced MR imaging of the normal facial nerve].

We performed a prospective imaging study of the normal facial nerve within the temporal bone before and after injection of Gd-DTPA. The study included 29 patients using a 1.5T superconducting unit and 40 nerves (right: 21; left: 19) were available for analysis. There was no enhancement of the facial nerve within the internal auditory canal in the entire series. However, the enhancement at the labyrinthine segment was observed in one nerve (3%); at the geniculate ganglion in seven (18%); at the tympanic segment in 18 (45%) and at the mastoid segment in 28 nerves (70%). Our results indicate that enhancement of the facial nerve in normal subjects is not a rare condition.

Adolescent↗
PubMed1991

[MR imaging of the thymoma--differentiation of invasive thymoma from noninvasive thymoma].

Magnetic resonance imaging (MRI) findings were reviewed in nine patients with histologically confirmed thymoma. The morphologic findings obtained by MRI were useful in distinguishing invasive from noninvasive thymoma. Invasive thymomas (2 cases) showed irregular contours and broad obliteration of the fatty plane between the mass and great vessels on T1-weighted coronary images. Perivascular infiltration shadow was considered to be characteristic of invasive thymoma. Noninvasive thymomas (7 cases) were round or oval in shape and showed slight obliteration of the fatty plane. In conclusion, MRI was helpful in differentiating invasive from noninvasive thymoma and defining the extent of thymoma.

Adult↗
PubMed1990

[Sagittal MR images of normal pineal glands after Gd-DTPA injection].

We evaluated normal pineal glands on Gd-DTPA enhanced MR images on a 1.5 Tesla superconducting unit. On enhanced sagittal MR images with a 3-mm slice thickness, pineal glands were identified as solid or cystic structures. The solid and cystic pineal glands were divided into two subgroups according to the degree of enhancement. The solid pineal glands showed diffuse or subtle enhancement and cystic ones showed peripheral enhancement either completely or incompletely. Of the 50 patients, 19 (38%) had solid pineal glands and 31 (62%) had cystic ones. In male, 7 out of 11 (63%) showed solid pineal glands and in female, 27 out of 39 (70%) showed cystic ones.

Adolescent↗
PubMed1989

Monostotic fibrous dysplasia of the left parietal bone--case report.

A 14-year-old female presented with a hard, painless mass, 5 x 5 cm, in the left parietal region. Skull x-rays showed a radiolucent skull tumor with a sclerotic margin in the parietal region. Computed tomography revealed an intradiploic multilocular mass separated by bony trabeculae. The outer table had thinned and protruded outward. The inner table was also thin and protruded inward slightly. External carotid angiography revealed a faint tumor stain and feeding from the middle meningeal artery. Bone scintigraphy revealed abnormal uptake in the lesion. Total removal of the skull tumor and cranioplasty were performed. The histological diagnosis was fibrous dysplasia. Fibrous dysplasia within the cranial vault is often expressed as painless bulging without neurological symptoms. Surgery is recommended when neurological symptoms and/or cosmetic problems are present. Histological confirmation of the diagnosis is also important.

Adolescent↗
PubMed1988

Congenital muscular dystrophy (Fukuyama type)--changes in the white matter low density on CT.

Sixty-two computed tomographic (CT) scans of 36 patients with congenital muscular dystrophy of Fukuyama type (FCMD) were analysed. A low density area in the cerebral white matter was characteristic of FCMD and a special reference was made to the changes in the white matter low density. It was present in 15 patients out of 36 (42%) and frequently seen in the scans obtained on the younger patients; among 11 scans taken of patients between 1 and 2 years of age, 10 scans (91%) showed the white matter low density. Repeated CT scans were carried out on 26 of the 36 cases. Follow-up study revealed that the white matter low density areas were most apparent around the age of one year and decreased or disappeared at 2 or 3 years of age. From these observations, delayed myelination was suspected for the pathogenesis of the low density area found in FCMD.

Adolescent↗
PubMed1981

Postcontrast computed tomography in subarachnoid hemorrhage from ruptured aneurysms.

Computed tomography (CT) scans of 49 patients with subarachnoid hemorrhage (SAH) secondary to ruptured aneurysms were reviewed. Subarachnoid blood was detected in 95% when CT was performed within 5 days after the bleeding. Prediction of the site of the ruptured aneurysm from distribution of the cisternal blood varied from 92% for the anterior cerebral artery aneurysms to 70% for the middle cerebral and 47% for the internal carotid artery aneurysms. Following plain CT scans, postcontrast studies were performed in 27 patients. Aneurysms were directly visualized in 8 cases and subarachnoid enhancement was noted in 21. In 3 cases, subarachnoid enhancement made possible a correct diagnosis of SAH in the absence of evidence of cisternal blood on precontrast CT scans.

Adult↗
PubMed1980

Sequential computed tomography scans in acute cerebral infarction.

Sequential computed tomography (CT) scans were obtained in 30 patients with acute cerebral infarction. In some cases, infarction was seen on the scans as early as three to six hours after onset of symptoms. Although small areas of petechial hemorrhagic infarction are not easily detected by currently available equipment, positive contrast enhancement helps locate petechial hemorrhagic infarction, which is usually in the cortical gray matter of the cerebral mantle and the central gray matter of the deep central gray matter. Contrast-enhanced CT scans are a useful method for detecting small infarctions. However, when a CT scan is performed within five days of ictus, contrast enhancement is usually not required.

Acute Disease↗
PubMedDate not supplied

Computed tomography of ovarian masses.

A retrospective analysis of CT images in 138 histologically proven ovarian masses in 100 patients was undertaken to evaluate the usefulness and limitation of CT in the diagnosis of ovarian tumors. Benign masses were purely cystic in 98 (94.2%) and had solid component (including thickened walls, thickened septa, papillary projections) in five of 104 lesions (4.8%) on CT. These five masses, which are classified as benign solid tumors, could not be differentiated from malignant tumors by either the size of the solid portion or the intensity of contrast enhancement. In the malignant tumors a solid portion was detected in 32 of 34 tumors (94%). When a solid component is detected in an ovarian mass, the mass should be considered malignant although a few cases will be benign solid tumors. In Krukenberg tumors, which were all of gastric origin, the solid component was so large that it occupied more than one-half the mass. Therefore, if the solid portion of the ovarian mass is large on CT, upper gastrointestinal study should be performed to rule out Krukenberg tumor.

Diagnosis, Differential↗
PubMedDate not supplied

Facial nerve neuromas: CT findings.

Although neuromas of the facial nerve are rare, they present with uniform clinical and radiological findings. Their pluridirectional tomography findings have been well described; however, the appearance of the intracranial extension of the neuroma which is best visualized by CT has not been emphasized. We report five cases of facial nerve neuromas with particular attention to their intracranial extension. For comparative purposes we also have reviewed 10 cases of acoustic and eight cases of trigeminal neuromas, all involving the cerebellopontine angle (CPA) and the middle cranial fossa. Two of the five facial nerve neuromas affected the second and third segments of the facial canal, and three involved both the CPA and the middle cranial fossa spreading across the midpetrosal bone. This type of tumor extension seems to be characteristic of facial nerve neuromas. In acoustic and trigeminal neuromas the tumor crossing toward the middle fossa takes place via the tentorial hiatus (acoustic) and the petrous apex (trigeminal).

Adult↗
PubMedDate not supplied

Multiple sclerosis simulating brain tumor on computed tomography.

A 44-year-old woman with multiple sclerosis (MS) stimulating a brain tumor on CT is reported. At the first hospitalization, a heterogeneously enhancing mass lesion with perifocal edema was identified on CT in the left parietal lobe. Biopsy of the lesion revealed necrotic change of the brain, gliosis, and perivascular cuffing; several months later no tumor cells were identified. The follow-up CT revealed reduction of the enhancing lesion and disappearance of the perifocal edema, with only a low density area persisting. At the second hospitalization, CT revealed a ring enhancing lesion with perifocal edema in the right temporoparietal region. Follow-up CT several months later revealed reduction of the lesion, with the residual of a small low density area. Magnetic resonance (MR) allowed us to identify multiple lesions in addition to those visualized on CT. In some cases of MS, the CT findings are very similar to those found in brain tumors. In these instances, MR is more useful in the diagnosis of MS than CT.

Adult↗
PubMedDate not supplied

Potential usefulness of an artificial neural network for assessing ventricular size.

An artificial neural network approach was applied to assess ventricular size from computed tomograms. Three layer, feed-forward neural networks with a back propagation algorithm were designed to distinguish between three degrees of enlargement of the ventricles on the basis of patient's age and six items of computed tomographic information. Data for training and testing the neural network were created with computed tomograms of the brains selected at random from daily examinations. Four radiologists decided by mutual consent subjectively based on their experience whether the ventricles were within normal limits, slightly enlarged, or enlarged for the patient's age. The data for training was obtained from 38 patients. The data for testing was obtained from 47 other patients. The performance of the neural network trained using the data for training was evaluated by the rate of correct answers to the data for testing. The valid solution ratio to response of the test data obtained from the trained neural networks was more than 90% for all conditions in this study. The solutions were completely valid in the neural networks with two or three units at the hidden layer with 2,200 learning iterations, and with two units at the hidden layer with 11,000 learning iterations. The squared error decreased remarkably in the range from 0 to 500 learning iterations, and was close to constant over two thousand learning iterations. The neural network with a hidden layer having two or three units showed high decision performance. The preliminary results strongly suggest that the neural network approach has potential utility in computer-aided estimation of enlargement of the ventricles.

Cerebral Ventricles↗