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Biomedical subjects

Y Korogi

Publications and source records attributed to Y Korogi.

At least 73 records · Page 4Linked to original sources
PubMed1997

Comparison of HASTE and segmented-HASTE sequences with a T2-weighted fast spin-echo sequence in the screening evaluation of the brain.

OBJECTIVE: The purpose of this study was to evaluate the neuroradiologic application of half-Fourier acquisition single-shot turbo spin-echo (HASTE) and segmented-HASTE (s-HASTE) sequences in comparison with a T2-weighted fast spin-echo sequence. MATERIALS AND METHODS: First, HASTE, s-HASTE, and fast spin-echo sequences were evaluated for blurring artifacts with a stationary phantom and for motion artifacts with a moving phantom, which repeated constant or intermittent to-and-fro motions at variable intervals. Second, 30 consecutive patients with various intracranial diseases were prospectively examined with the three sequences. Lesions were classified into four groups according to size and signal intensity on fast spin-echo MR images as follows: large hyperintense, small hyperintense, small markedly hyperintense, and hypointense lesions. Signal intensities of the lesion, putamen, and gray matter were compared with the signal intensity of white matter, and contrast-to-noise ratios were calculated. Overall image quality, conspicuity of lesions, delineation of the junction between gray matter and white matter, conspicuity of the putamen, and certain types of artifacts were evaluated qualitatively. RESULTS: In the phantom study, the HASTE sequence was least affected by motion artifacts and the fast spin-echo sequence was most affected although the images of the HASTE sequence were most degraded by blurring artifacts. In the clinical study, we found no significant differences among the three sequences for contrast-to-noise ratios or conspicuity of large hyperintense and small markedly hyperintense lesions. However, the contrast-to-noise ratios of hypointense lesions and gray matter, and the conspicuity of hypointense lesions were significantly poorer for the HASTE sequence than for the fast spin-echo sequence. The contrast-to-noise ratios of small hyperintense lesions and the putamen, conspicuity of small hyperintense lesions and putamen, and delineation of the junction between gray matter and white matter were significantly poorer for HASTE and s-HASTE sequences than for the fast spin-echo sequence. Ghost artifacts, which were observed during the s-HASTE sequence, were sometimes superimposed on the image. CONCLUSION: The HASTE and s-HASTE sequences afford substantial time reduction and also decrease motion artifacts and thus have potential advantages for neuroradiologic application, especially in uncooperative or unsedated children. The s-HASTE sequence may be preferable to the HASTE sequence because of fewer blurring artifacts and higher T2 contrast. However, small hyperintense and hypointense lesions may be overlooked when HASTE and s-HASTE sequences are used.

Artifacts↗
PubMed1997

Intracranial vascular stenosis and occlusion: MR angiographic findings.

PURPOSE: To investigate whether obtaining axial source images from three-dimensional Fourier transform (3DFT) time-of-flight MR angiography improves the detection of intracranial vascular stenosis and occlusion if added to maximum-intensity projection (MIP) images. METHODS: The angiograms of 103 patients who had MR angiography for evaluation of possible intracranial vascular disease were reviewed retrospectively in a quantitative and nonquantitative fashion. Diameters of vessels on MR angiograms were measured quantitatively by two reviewers using a magnifying loupe and compared with the results from conventional angiograms. Degrees of stenoocclusive disease were categorized into five classes; an artery with stenosis of 50% or greater was considered to be diseased. Another five observers also reviewed the MIP images with and without source images in a blinded fashion by means of nonquantitative visual inspection. RESULTS: In all, 23 stenoocclusive lesions of 50% or greater were available for review. In the quantitative analysis, with MIP images alone, 14 (78%) of 18 moderate and severe stenoses and four (80%) of five occlusions were identified correctly. The addition of the source images increased the sensitivity to 100% for moderate and severe stenoses and to 100% for occluded vessels. In the visual inspection study, however, no statistically significant differences were found between interpretations of MIP images alone and those of MIP images in combination with source images. CONCLUSION: In the quantitative study, interpretation of source images rather than MIP images reduced the tendency to overestimate stenosis seen with MR angiography and improved the sensitivity for detecting stenosis of 50% or greater. There was a discrepancy between the quantitative study and visual inspection. Experienced observers had a tendency to underestimate the degree of stenosis.

Adult↗
PubMed1997

[Cerebellar atrophy in Minamata disease: comparison with spino-cerebellar degeneration on MR images].

We evaluated atrophic patterns of the cerebellar vermis in seven patients with Minamata disease (MD) and nine patients with spino-cerebellar degeneration (SCD) on MR images. Twenty-five control subjects were also examined. The cerebellar vermis was divided into superior, middle, and inferior parts by the primary fissure and the prepyramidal fissure on the median sagittal T1-weighted MR image. The length and area of each part were measured. In the patients with SCD, there were no significant differences in the degree of atrophy among the three parts. However, MR images of the patients with MD showed more severe atrophy in the middle and inferior parts than in the superior part. Atrophy of the superior part was less frequently observed in MD patients.

Adult↗
PubMed1997

Evaluation of intracranial lesions with inversion recovery half-Fourier single-shot turbo spin-echo MR: initial observations.

PURPOSE: To determine the value of inversion recovery half-Fourier single-shot turbo spin-echo (IR-HASTE) MR sequences in the characterization of a variety of intracranial lesions, with the focus on differentiating between epidermoids and nonneoplastic cystic lesions. METHODS: We used a 1.5-T MR unit to study five epidermoids, seven arachnoid cysts, seven other nonneoplastic cysts (three neuroepithelial cysts, two interhemispheric cysts, and two Rathke's cleft cysts), and eight solid neoplasms (three meningiomas, two astrocytomas, one subependymoma, one cavernoma, and one metastatic tumor) using IR-HASTE sequences with variable inversion times (TI). Imaging time for each section was 2 seconds for the sequence. The TI nulling values were analyzed statistically. RESULTS: The TI nulling values were 1200 to 2300 for the epidermoids, 2800 to 3000 for the arachnoid cysts, 300 and 800, respectively, for the Rathke's cleft cysts, 2500 to 3000 for the other nonneoplastic cysts, and 300 to 1500 for the solid neoplasms. There was no overlap of TI nulling values between the arachnoid cysts and the epidermoids; the difference was statistically significant. Both patients with interhemispheric cysts had two lesions in which the TI nulling values were different. CONCLUSION: IR-HASTE sequences provide a rapid and reliable imaging method for differentiating among epidermoids, arachnoid cysts, and solid neoplasms. This technique also provides information about the continuity of the multicystic lesions in terms of the differences in their TI nulling values. For solid intraaxial masses, the use of IR-HASTE helps to differentiate intratumoral cysts and necrosis from solid components.

Adolescent↗
PubMed1997

T2 shortening in the visual cortex: effect of aging and cerebrovascular disease.

PURPOSE: To evaluate the effect of aging and cerebrovascular disease on T2 shortening in the visual cortex at MR imaging. METHODS: MR images of 72 neurologically normal subjects (45 men and 27 women, 35 to 92 years old) and 32 (13 men and 19 women, 54 to 92 years old) with cerebrovascular disease were evaluated retrospectively. On T2-weighted spin-echo images, the signal intensity of the visual, motor, and sensory cortices was divided into three grades and compared with the signal intensity of the frontal subcortical white matter. RESULTS: Decreased signal intensity (grade III) was rarely seen in the visual and sensory cortices of the neurologically normal subjects who were less than 60 years old. The signal intensity of the motor cortex decreased rapidly after the age of 50 years. At 61 to 70 years of age, 53% of these subjects had grade III intensity, and at age 71 years or older, 94% had reached grade III. The frequency of progression from grade I to grade III was lower in the visual cortex than in the motor cortex; 22% of these subjects had grade III appearance at age 61 to 70 years, and at age 71 years older, 56% had reached grade III. In patients with cerebrovascular disease who were older than 60 years of age, the frequency of grade III signal intensity in the visual cortex was almost equal to that in the neurologically normal subjects. CONCLUSIONS: T2 shortening in the visual cortex is frequently seen in neurologically normal older persons. These findings are compatible with a previously reported histochemical study of normal iron deposition in the visual cortex. Cerebrovascular disease has no effect on T2 shortening in the visual cortex.

Adult↗
PubMed1997

MR changes in the calcarine area resulting from retinal degeneration.

PURPOSE: To study MR images for atrophic changes in the calcarine area resulting from retinal degeneration. METHODS: MR images from nine patients with retinal degeneration confirmed by ophthalmologic examination and from 30 healthy volunteers were reviewed. The causes of retinal degeneration were hereditary pigmentary degeneration of the retina (four patients), high myopia (two patients), and chorioretinal atrophy (three patients); all patients had visual disturbances and visual field abnormalities. To estimate the morphological changes of the calcarine area, the widths of the right and left calcarine fissures were measured on T1-weighted sagittal images and compared with images from age-matched control subjects. RESULTS: The calcarine fissures were significantly dilated in the patients with retinal degeneration. The anterior and middle points, which represent the peripheral visual field center, were more dilated than the posterior point. CONCLUSION: The MR findings suggested calcarine atrophy related to retinal degeneration. Transneuronal degenerative changes may occur in the calcarine area after retinal degeneration.

Aged↗
PubMed1997

MR of epidermoids with a variety of pulse sequences.

PURPOSE: To assess the usefulness of fluid-attenuated inversion recovery (FLAIR) and constructive interference in steady state (CISS) sequences in depicting epidermoid tumors. METHODS: Six patients with surgically confirmed epidermoid tumors in the subarachnoid space were examined with T1-weighted MR imaging with a spin-echo sequence, and with T2- and proton density-weighted imaging with a fast spin-echo sequence, a FLAIR sequence, and a CISS sequence. In the qualitative analysis, three observers compared the five sequences for visibility of tumors and presence of artifacts. A quantitative analysis was also performed by measuring the contrast-to-noise ratio. RESULTS: On visual assessment, the FLAIR sequence depicted all tumors as hyperintense relative to cerebrospinal fluid. The CISS sequence depicted all tumors as hypointense relative to cerebrospinal fluid and was considered to show tumor extension better than the FLAIR sequence. At quantitative analysis, the mean contrast-to-noise ratios of tumor to cerebrospinal fluid on T1-, T2-, and proton density-weighted images, and on FLAIR and CISS sequences were 2.85, 3.41, 4.42, 16.13, and 20.23, respectively. The contrast-to-noise ratios for the FLAIR and CISS sequences were significantly higher than those for the T1-, T2-, and proton density-weighted sequences. The contrast-to-noise ratio was not significantly different between FLAIR and CISS sequences, although the CISS sequence was slightly superior. CONCLUSION: CISS and FLAIR sequences depicted epidermoid tumors in the subarachnoid spaces better than conventional spin-echo images did. The CISS sequence produced a relatively constant contrast between the tumors and less artifactual interference.

Adolescent↗
PubMed1996

MR signal intensity of the perirolandic cortex in the neonate and infant.

Our purpose was the study the magnetic resonance (MR) signal intensity of the perirolandic gyri perinatally and to correlate it with the histological findings in formalin-fixed brains, focusing on myelination. MRI of 20 neurologically normal neonates and infants, of 37-64 weeks postconception (PCA), were studied retrospectively. We reviewed four formalin-fixed brains of infants 37-46 weeks PCA microscopically. The posterior cortex of the precentral gyrus (P-PRE) and the anterior cortex of the postcentral gyrus (A-PST) had different signal intensity from the adjacent surrounding cortex. On T1-weighted images P-PRE and A-PST gave higher signal 41-44 weeks PCA; on T2-weighted images, they gave lower signal 37-51 weeks PCA. Histological examination revealed very little myelination of the nerve fibres within both the P-PRE and the A-PST, while considerable myelination was present in the internal capsule and central corona radiata. The changes in signal intensity in the perirolandic gyri may reflect not only the degree of myelination but also the more advanced development of the nerve cells, associated with rapid proliferation and formation of oligodendroglial cells, synapses and dendrites. They could be another important landmark for brain maturation.

Age Factors↗
PubMed1996

Intracranial aneurysms: diagnostic accuracy of MR angiography with evaluation of maximum intensity projection and source images.

PURPOSE: To determine whether evaluation of source images from magnetic resonance (MR) angiography in addition to maximum-intensity projection (MIP) images improves the detection of aneurysms. MATERIALS AND METHODS: Conventional and MR angiography were performed in 193 patients with various intracranial vascular lesions or normal findings. Images were evaluated in a blinded manner. Two readings were performed 6 weeks apart by evaluating MIP images with and without source images. Results were evaluated with receiver operating characteristic analysis. RESULTS: Sensitivity for the detection of aneurysms increased slightly when source images were included. The detection rate of internal carotid artery aneurysms was most improved with the addition of source images. No statistically significant differences in performance were found between the readings with MIP images alone and with source images. CONCLUSION: Sensitivity may improve with combined reading of nonselective MIP and source images.

Case-Control Studies↗
PubMed1996

T2 shortening in the motor cortex: effect of aging and cerebrovascular diseases.

PURPOSE: To evaluate the effect of aging and cerebrovascular diseases on T2 shortening in the motor cortex at magnetic resonance (MR) imaging. MATERIALS AND METHODS: High-field-strength (1.5-T) MR images of 298 neurologically normal patients (157 male patients, 141 female patients; age range, 2-86 years) and 107 patients with cerebrovascular diseases (66 men, 41 women; age range, 41-86 years) were evaluated retrospectively. On T2-weighted spin-echo images, the signal intensities of the motor, sensory, parietal, temporal, and prefrontal cortices were divided into three grades compared with the signal intensity of the frontal subcortical white matter. RESULTS: Decreased signal intensity (grade III) was not seen in any region in the neurologically normal patients younger than 60 years. After the age of 60 years, however, the signal intensity of the motor cortex decreased, and 43 (66%) of 65 neurologically normal patients reached grade III by age 80 years. In patients with cerebrovascular disease, grade III was seen in 12 (34%) of the 35 patients younger than 60 years (5th and 6th decades). CONCLUSION: T2 shortening of the motor cortex was seen frequently in the older neurologically normal individuals and in patients with cerebrovascular diseases. These findings are compatible with those of a previously reported histochemical study of normal iron deposition in the motor cortex.

Adolescent↗
PubMed1996

Carotid-cavernous sinus fistula and aneurysmal rupture associated with fibromuscular dysplasia. A case report.

A patient with carotid-cavernous sinus fistula associated with fibromuscular dysplasia, who died from rupture of an associated splenic aneurysm despite successful treatment of the CCF, is reported. When multivessel involvement with aneurysmal dilatation is observed in patients with fibromuscular dysplasia, the possibility of aneurysm ruptures in any of the arteries should be considered.

Adult↗
PubMed1996

Prevention of intimal hyperplasia by irradiation. An experimental study in rabbits.

PURPOSE: This experimental study was designed to investigate the effect of irradiation in prevention of intimal hyperplasia. MATERIAL AND METHODS: Twenty rabbits were divided into 4 groups, which were irradiated with 2, 5, 10 and 20 Gy, respectively. The intima of both femoral arteries was injured by air-drying, and irradiation was performed on the unilateral side. The contralateral+ femoral artery served as a control. Angiograms as well as histologic specimens were obtained 1 month later. RESULTS: Marked intimal hyperplasia was observed in all control sites. There were no significant differences in thickness of intimal hyperplasia between irradiated and control sites in groups irradiated with 2 and 5 Gy. However, in the 10-Gy- and 20-Gy-irradiated groups, intimal hyperplasia of the irradiated site was significantly suppressed. Medial thinning and dilation of the lumen were observed in the 20-Gy-irradiated group. CONCLUSION: Radiation may prevent intimal hyperplasia. Further investigation of the optimal dose, timing of irradiation, and long-term patency of irradiated vessels may be needed.

Animals↗
PubMed1996

Lingual carcinoma. Correlation of MR imaging with histopathological findings.

PURPOSE: To determine the utility of MR imaging in the evaluation of lingual carcinomas. MATERIAL AND METHODS: Eleven patients with lingual carcinoma were evaluated with MR imaging including dynamic study within one week before surgery. Nine patients underwent preoperative chemotherapy or irradiation, and 2 patients had no preoperative treatment. Delineation of the tumor, the contrast between tumor and surrounding tissue, and extent of the tumor were evaluated in a blinded manner. After glossectomy, MR images were correlated with pathological findings. Statistical analysis was performed on the visual assessment ratings. RESULTS: Blinded evaluation suggested that dynamic and T2-weighted images (T2WI) were significantly superior to postcontrast T1WI in demonstrating the lesion. There were no significant differences between dynamic MR images and T2WIs. However, histopathological correlation showed that in patients with preoperative treatment, dynamic MR imaging demonstrated more accurately the size and extent of the residual tumor than did T2WI and postcontrast T1WI, which tended to demonstrate an area of signal abnormality that was more extensive than the true size of the residual lesion. In patients without preoperative treatment, dynamic MR imaging, T2WI, and postcontrast T1WI gave an equivalent depiction of the extent of the carcinoma. CONCLUSION: In patients with no preoperative treatment, dynamic MR imaging does not appear to offer any advantage over T2WI. However, in patients with preoperative treatment, dynamic MR imaging provides a more accurate assessment of the residual tumor than do T2WI and postcontrast T1WI.

Aged↗
PubMed1996

Case report: varicella-zoster virus myelitis--serial MR findings.

The authors describe a 32-year-old male in whom herpes zoster of the left upper extremity was complicated by the development of cervical myelitis. Contrast enhancement and abnormal signal intensity on T1 and T2 weighted images was seen at C1-C6 levels in the spinal cord and medulla. There was also slight enlargement of the cord at these levels. On serial MR imaging the degree of enhancement changed from marked to none with corresponding clinical improvement.

Adult↗
PubMed1996

MR signal intensity of the optic radiation.

PURPOSE: To determine whether a hyperintense layer adjacent to the lateral ventricle on T2-weighted MR images represents the optic radiation. METHODS: We reviewed 11 brain specimens from patients with nonneurologic diseases and MR images from 43 healthy volunteers. The MR images in a patient with cerebral infarction involving the lateral geniculate body were also reviewed to evaluate wallerian degeneration of the optic radiation. RESULTS: The external sagittal stratum, composed of the optic radiation, showed a pale layer in specimens stained by Bodian's method. On high-power microscopic views of the specimens, the axons of the external sagittal stratum were large and separated by wide translucent spaces. In the volunteers, the external sagittal stratum appeared hyperintense on T2-weighted MR images and hypointense on T1-weighted images. The MR images in a patient with cerebral infarction showed hyperintensity within the layer corresponding to the external sagittal stratum. CONCLUSIONS: The hyperintense layer on T2-weighted images represents the external sagittal stratum, or optic radiation. The signal intensity of the external sagittal stratum reflects histologic characteristics of low axonal density.

Aged↗
PubMed1995

Intravascular ultrasonography of supra-aortic arteries as an adjunct to percutaneous transluminal angioplasty.

We report the intravascular ultrasonographic appearances of three supra-aortic atherosclerotic lesions in two patients before and after percutaneous transluminal angioplasty. Atherosclerotic plaques with calcification and dissection of the arterial wall after percutaneous transluminal angioplasty were demonstrated to better advantage, although they were difficult to see on conventional angiograms.

Aortic Dissection↗