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Biomedical subjects

Y Korogi

Publications and source records attributed to Y Korogi.

At least 55 records · Page 3Linked to original sources
PubMed1999

MR imaging of Tornwaldt's cysts.

OBJECTIVE: The purpose of this study was to assess the characteristics of Tornwaldt's cysts as revealed by routine MR studies. MATERIALS AND METHODS: We retrospectively reviewed MR images of the brain in 1208 consecutive subjects who ranged in age from 3 weeks to 93 years (mean, 57.1 years). The signal intensity, shape, and size of Tornwaldt's cysts were assessed. Patients with Tornwaldt's cysts were then questioned about the presence of persistent nasal discharge, occipital headaches, and halitosis and an unpleasant taste in the mouth and about a history of adenoidectomy. RESULTS: Tornwaldt's cysts were found in 23 patients (1.9%) who ranged in age from 39 to 78 years (mean, 57.3 years). Of the 23 Tornwaldt's cysts, all were isointense to CSF on T2-weighted images and hyperintense to gray matter on the fluid-attenuated inversion-recovery images. The cysts showed high signal intensity compared with muscle on T1-weighted images. Nineteen cysts were round and four were oval. The mean size of the lesions was 6.0 mm in the major axis and 5.5 mm in the minor axis. Two patients with Tornwaldt's cysts had persistent nasal discharge and occipital headaches, and another patient had occipital headaches alone. None of the patients had undergone an adenoidectomy. CONCLUSION: Lesions consistent with Tornwaldt's cysts were found in 1.9% of the routine MR studies of the brain. The cysts had high signal intensity on T1-weighted, T2-weighted, and fluid-attenuated inversion-recovery images.

Adolescent↗
PubMed1999

[Differential diagnosis of astrocytic tumors].

Primary brain tumors are subdivided into two basic groups: tumors of neuroglial origin (so-called gliomas) and nonglial tumors. The most common glioma is astrocytoma. In this review article, we describe the differential diagnosis of benign and malignant astrocytic tumors (astrocytoma, anaplastic astrocytoma, and glioblastoma) on conventional MR images. Regardless of the degree of histopathologic differentiation or anplasia, all infiltrating gliomas are clinically malignant. Therefore, it is important to diagnose the infiltrative nature of the tumors on MR images. Characteristic MR findings including signal intensity, contrast enhancement, and localization of the astrocytic tumors are discussed.

Adult↗
PubMed1999

Detection of intracranial hemorrhage with susceptibility-weighted MR sequences.

BACKGROUND AND PURPOSE: Detection of hemorrhage is important in the diagnosis and management of a variety of intracranial diseases. We evaluated the sensitivity of the following sequences for depicting chronic hemorrhagic foci associated with susceptibility dephasing: gradient-recalled echo (GRE) imaging, GRE-type single-shot echo-planar imaging (GRE-EPI), spin-echo-type single-shot echo-planar imaging (SE-EPI), turbo spin-echo (TSE) imaging, half-Fourier single-shot turbo spin-echo (HASTE) imaging, and segmented HASTE (s-HASTE) imaging. To our knowledge, no previous comparison has been made with these techniques in the same patient. METHODS: Fifty patients with suspected chronic hemorrhage were examined prospectively with the above six sequences. Contrast-to-noise ratio (CNR), sensitivity to detection of lesions, conspicuity of internal architecture, and sensitivity to small hemorrhagic foci were evaluated. RESULTS: Hemorrhagic foci were found in 35 patients. The CNR of the GRE, GRE-EPI, SE-EPI, TSE, s-HASTE, and HASTE sequences was 30.9, 23.7, 3.6, 6.1, -29.3, and -13.1, respectively; the number of small hemorrhagic foci detected was 85, 96, 44, 22, two, and one, respectively, for the supratentorial white matter; 70, 40, 19, four, zero, and zero, respectively, for the supratentorial cortical/subcortical region; and 73, 50, 26, 37, zero, and zero, respectively, for the infratentorial/skull-base region. CONCLUSION: The GRE sequence was best for detecting susceptibility dephasing associated with chronic intracranial hemorrhage. GRE-EPI, while comparable to GRE in the supratentorial compartment, was reduced in its sensitivity near the skull base, and may be used as an alternative to GRE in uncooperative, unsedated, pediatric, or claustrophobic patients. SE-EPI should not be used in screening for intracranial hemorrhage.

Adolescent↗
PubMed1999

Contrast enhancement of intracranial lesions: conventional T1-weighted spin-echo versus fast spin-echo MR imaging techniques.

BACKGROUND AND PURPOSE: The T1-weighted fast spin-echo (T1-FSE) MR imaging sequence is not used routinely, since the speed advantage is not as dramatic as it is in T2-weighted imaging. We evaluated the T1-FSE sequence to determine whether this technique can replace the conventional T1-weighted spin-echo (T1-SE) sequence for routine contrast-enhanced imaging. METHODS: Sixty-nine patients with intracranial enhancing lesions underwent both T1-SE and T1-FSE sequences in a random order after administration of contrast agent. Acquisition time was 55 seconds for the T1-FSE sequence and 2 minutes 38 seconds for the SE sequence. The conspicuity of enhancing lesions, peritumoral edema, and gray-to-white matter contrast as well as motion and flow artifacts were analyzed. Signal-to-noise ratios of enhancing lesions, gray matter, and white matter as well as contrast-to-noise ratios (CNRs) of enhancing lesions, with gray matter with white matter as the standard, were calculated. RESULTS: The conspicuity of enhancing lesions was better on T1-FSE sequences than on T1-SE sequences, although the difference in the CNRs of enhancing lesions did not reach significance. Images obtained with the T1-FSE sequence showed less flow and motion artifacts than did those obtained with the T1-SE sequence. The conspicuity of peritumoral edema and gray-to-white matter contrast was lower on the T1-FSE images than on the T1-SE images. CONCLUSION: The T1-FSE sequence reduces imaging time and has the potential to replace the conventional T1-SE sequence for the evaluation of enhancing lesions in the brain when time is a consideration.

Adolescent↗
PubMed1998

Virtual MRI endoscopy of the intracranial cerebrospinal fluid spaces.

We used constructive interference in steady state (CISS) 3D Fourier transform (3DFT) MRI data sets to obtain three-dimensional (3D) virtual MRI endoscopic views of the intracranial cerebrospinal fluid (CSF) spaces, processing them with a commercially available perspective endoscopic algorithm. We investigated the potential of the intracranial virtual MRI endoscopy applied to visualisation of the pathology in 13 patients with surgically confirmed trigeminal neuralgia (3), hemifacial spasm (3), acoustic neuroma (3), suprasellar germinoma (1), Langerhans cell histiocytosis (1), lateral ventricle nodules (1) and pituitary dwarfism (1). All images were acquired using a 1.5-T imager employing a circular polarised head coil. The CISS-3DFT data sets were transferred to a workstation for processing with the perspective endoscopic algorithm. Postprocessing for virtual MRI endoscopy was possible for all data sets. The lesions in 12 patients, and their complex anatomical relationships with the surrounding structures, were well seen on the 3D images. A small acoustic neuroma in the internal auditory meatus was not seen using virtual endoscopy. Although virtual MRI endoscopy has limitations, it provides 3D images which cannot be acquired using any other procedure.

Adolescent↗
PubMed1998

MRI in occipital lobe infarcts: classification by involvement of the striate cortex.

We reviewed the MRI studies of 25 patients with occipital lobe infarcts to clarify the distribution of infarcts in the posterior cerebral arterial territory, focussing on their relationship to the striate cortex. Visual field defects and MRI findings were also correlated in 16 patients. On coronal and/or sagittal images, the distribution of the infarct and its relationship to the striate cortex were classified. Involvement of the cortex of both upper and lower lips of the calcarine fissure was observed in 10 patients, and involvement of the lower lip alone in 15. The upper cortical lesions were always accompanied by lower cortical lesions. The visual field defects were complete hemianopia in nine patients, superior quadrantanopia in six and hemianopia with a preserved temporal crescent in one. All patients with superior quadrantanopia had involvement of the lower cortex alone; there were no cases of inferior quadrantanopia. The characteristic vascular anatomy, and poor development of the collateral circulation in the lower cortical area, may explain the vulnerability of this area to infarcts.

Adult↗
PubMed1998

Pulsatile cycle-specific data acquisition in carotid MR angiography with segmented FLASH sequence: experimental and clinical investigation.

RATIONALE AND OBJECTIVES: The authors evaluated the usefulness of diastolic data acquisition in magnetic resonance (MR) angiography of the carotid artery. MATERIALS AND METHODS: MR angiographic images of phantom models of 30%, 40%, and 50% stenosis were obtained at different pulsatile cycles by using variable delay times from the electrocardiogram triggering with segmented fast low-angle shot sequences (14/7.3 [repetition time msec/echo time msec]) with k-space segmentation. The degree of stenosis was measured on the MR angiographic images by three observers. Poststenotic signal intensity loss was analyzed by measuring the signal intensity on the axial image acquired 10 mm distal to the stenotic portion of the 50% stenosis phantom at variable delay time from triggering. Six patients with stenosis of the internal carotid artery also underwent conventional and MR angiography. The degree of stenosis depicted on diastolic- and systolic-phase MR angiographic images was measured by three observers and compared with that shown on the conventional angiographic images. RESULTS: The diastolic-phase images more accurately depicted the degree of stenosis than did the systolic-phase images in the phantom and all six patients, although the degree of stenosis tended to be overestimated on both images. The degree of stenosis was most overestimated with triggering that occurred at the time of peak flow velocity. In the phantom with 50% stenosis, the signal intensity 10 mm distal to the stenotic portion was decreased in the systolic phase. CONCLUSION: Diastolic data acquisition is a useful method of reducing intra- and poststenotic signal intensity loss in the carotid artery.

Aged↗
PubMed1998

Dural carotid cavernous fistulas: role of conventional radiation therapy--long-term results with irradiation, embolization, or both.

PURPOSE: To evaluate the long-term results of irradiation alone or of embolization with or without irradiation in patients with dural carotid cavernous fistulas (DCCFs). MATERIALS AND METHODS: Between 1984 and 1996, symptomatic DCCFs in 26 patients were treated by using irradiation alone (protocol 1, n = 12) before April 1988 and by using embolization as an initial treatment (protocol 2, n = 14) during and after April 1988. When angiography showed no improvement after embolization, irradiation was added (n = 6). On the basis of drainage flow speed, DCCFs were classified as fast, medium, or slow. RESULTS: With irradiation alone, all six patients with slow- to medium-type DCCFs had cure with a mean follow-up of 62 months. Four of six patients with fast-type DCCFs had cure or improvement, but the remaining two had no change. In the embolization group, irradiation was added in six patients with fast-type DCCFs. With a mean follow-up of 24 months, four of the six patients had cures, one had improvement, and one had no clinical change. Those who underwent protocol 2 had cures significantly earlier than those who underwent protocol 1 (P < .05). CONCLUSION: Conventional radiation therapy resulted in cure of DCCFs in nine (75%) of the 12 patients and in improvement of signs and symptoms in one (8%). Fast-type DCCFs may not always be improved. Radiation therapy may be useful in DCCFs after embolization.

Adult↗
PubMed1998

Use of fluid-attenuated inversion recovery (FLAIR) pulse sequences in perinatal hypoxic-ischaemic encephalopathy.

The purpose of this study was to evaluate the usefulness of fluid-attenuated inversion recovery (FLAIR) techniques in patients with perinatal hypoxic-ischaemic encephalopathy. 13 patients with a history of perinatal hypoxic-ischaemic encephalopathy (age range 1 month to 3.6 years) underwent T1 and T2 weighted spin echo and FLAIR imaging with a 1.5 T superconducting unit. FLAIR images were qualitatively evaluated in comparison with T1 and T2 weighted images by three experienced radiologists. Quantitative analysis (contrast and contrast-to-noise ratio) was also performed. FLAIR images were preferred to T1 and T2 weighted images in the demonstration of periventricular leukomalacia (PVL), cystic PVL and subcortical lesions near the brain surface. On T1 and T2 weighted images, almost all lesions were demonstrated as hypointense or hyperintense areas, respectively. However, FLAIR images could differentiate cystic lesions by their signal intensities. FLAIR images were not diagnostic in two cases with PVL. In conclusion FLAIR sequences provide useful information in patients with perinatal hypoxic-ischaemic encephalopathy.

Child, Preschool↗
PubMed1998

CT angiography in vascular intervention for steno-occlusive diseases: role of multiplanar reconstruction and source images.

The aim of this study was to assess the efficacy of CT angiography for steno-occlusive diseases before and after interventional procedures, focusing on the role of multiplanar reconstruction (MPR) and source images. 17 patients with 20 steno-occlusive lesions underwent CT angiography before and after interventional procedures. For each lesion, the percentage stenosis obtained on CT angiography was compared with that on conventional angiography. In addition, MPR and source images were evaluated for the presence of wall thickening and calcification before interventional procedures, and the presence of dissection and luminal shape after interventional procedures. These findings were compared with those of conventional angiography. Although the percentage stenosis depicted on CT angiography correlated well with that on conventional angiography, MPR and source images clearly demonstrated the effect of intervention and the residual stenosis. MPR and source images clearly depicted wall thickening, wall calcification, the presence of dissection and the luminal shape. CT angiography provides useful information before intervention, while MPR and source images are of value in evaluating arterial wall abnormalities and morphological changes associated with interventional procedures.

Adult↗
PubMed1998

Correlation of MR imaging-determined cerebral blood volume maps with histologic and angiographic determination of vascularity of gliomas.

OBJECTIVE: Our purpose was to evaluate the relationships between the ratio of maximum relative cerebral blood volume (rCBV) (rCBV ratio = rCBV[tumor]/rCBV[contralateral white matter]) and histologic and angiographic vascularities of gliomas using the gradient-echo echoplanar MR imaging technique. We also evaluated the usefulness of rCBV maps for grading gliomas. SUBJECTS AND METHODS: We examined 30 patients with histologically verified gliomas. Gliomas were classified as glioblastoma, anaplastic glioma with enhancement, anaplastic glioma without enhancement, and low-grade glioma. The maximum rCBV ratio of each glioma was compared with both histologic and angiographic vascularities, and the relationship between the maximum rCBV ratios and each type of glioma was established. RESULTS: The maximum rCBV ratios of the gliomas significantly correlated with both histologic and angiographic vascularities (p < .001). Mean values and SDs of maximum rCBV ratios of each type of tumor were 7.32+/-4.39 for glioblastomas, 5.84+/-1.82 for anaplastic gliomas with enhancement, 1.53+/-0.75 for anaplastic gliomas without enhancement, and 1.26+/-0.55 for low-grade gliomas. The maximum rCBV ratios of the glioblastomas were significantly higher than those of the anaplastic gliomas without enhancement (p = .002) and the low-grade gliomas (p < .001). The maximum rCBV ratios of the anaplastic gliomas with enhancement were higher than those of the anaplastic gliomas without enhancement and the low-grade gliomas, but the differences were not statistically significant (p = .08 and p = .03, respectively). CONCLUSION: The results of perfusion-sensitive MR imaging with gradient-echo echoplanar technique correlated with both histologic and angiographic vascularities.

Adolescent↗
PubMed1998

Three-dimensional FISP imaging in the evaluation of carotid cavernous fistula: comparison with contrast-enhanced CT and spin-echo MR.

PURPOSE: The purpose of this study was to assess the value of three-dimensional fast imaging with steady-state precession (FISP) MR sequences relative to contrast-enhanced CT and spin-echo MR imaging in the diagnosis of carotid cavernous fistula (CCF). METHODS: Seventeen patients with 19 angiographically proved CCFs had contrast-enhanced CT, spin-echo MR imaging, and 3-D FISP imaging. Three observers assessed these imaging studies as well as those of 43 control sides in a blinded manner for the presence or absence of CCF. Receiver operating characteristic analysis was used to assess the diagnostic utility of each imaging technique. In a nonblinded study, contrast-enhanced 3-D FISP images were also evaluated. RESULTS: Higher diagnostic accuracy was obtained with 3-D FISP sequences, as the shunt flow within the cavernous sinus was well seen. Sensitivity of 3-D FISP images was 83% and specificity was 100% in the blinded study. In the receiver operating characteristic analysis, the diagnostic performance of observers was found to be better with the 3-D FISP images than with the spin-echo MR images. Although there were no significant difference between 3-D FISP and contrast-enhanced CT, higher diagnostic performance was obtained with 3-D FISP images. In three CCFs without anterior drainage, a diagnosis was made only from the 3-D FISP images. The contrast-enhanced 3-D FISP images were not helpful, since the cavernous sinuses enhanced. CONCLUSION: Three-dimensional FISP imaging is superior to spin-echo MR imaging and contrast-enhanced CT in the diagnosis of CCF. Contrast-enhanced 3-D FISP images are not helpful for the evaluation of CCF.

Adolescent↗
PubMed1998

Contrast-enhanced T1-weighted three-dimensional gradient-echo MR imaging of the whole spine for intradural tumor dissemination.

BACKGROUND AND PURPOSE: When evaluating intradural tumor dissemination in the spine, contrast-enhanced T1-weighted 2D spin-echo (2D-SE) images are frequently problematic because most of the lesions are very small. Our purpose was to compare 2D-SE images with 3D gradient-echo (3D-GE) postcontrast images to determine which technique is better for depicting intradural tumor dissemination. METHODS: Ten patients with and 10 without intradural tumor dissemination were examined prospectively with MR imaging. After contrast administration, all patients underwent sagittal imaging with 2D-SE and 3D-GE sequences. Subsequently, the 2D-SE, 3D-GE, and multiplanar reconstruction (MPR) images of the 3D-GE sequence were evaluated for image quality, lesion detectability, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of the disseminated lesions. RESULTS: Although delineation of spinal cord from CSF was slightly poorer on the 3D-GE sequences than on the 2D-SE sequences, the difference was not significant. In the evaluation of image artifacts and contrast between spinal cord and CSF, there was no significant difference. In seven patients with nodular enhancement, the 3D-GE sequence detected 46 lesions and the 2D-SE sequence detected 36. With MPR, the greatest number of lesions (n = 51) was detected, and vascular enhancement was clearly distinguished. There was no difference in SNR and CNR of lesions between the 3D-GE and 2D-SE sequences. CONCLUSION: The contrast-enhanced 3D-GE technique offers advantages over 2D-SE imaging in detecting intradural tumor dissemination, especially when the MPR technique is applied. This technique should be used for detecting intradural tumor dissemination.

Adolescent↗
PubMed1997

Cost containment and diffusion of MRI: oil and water?. Japanese experience.

The total number of MR units available in Japan relative to the population is the highest in the world. The total number of MR units installed in 1996 was 2,663, equivalent to 24 per million population. The average charge per procedure in Japan is only one fifth of that in the United States (USA), approximately US$200 and US$950, respectively, suggesting that economic considerations in Japan may not take the highest priority. Despite the low costs, the utilisation (the number of patients examined each year or per week) of MR units in Japan is only about half that in the USA. As such, an increase in the number of MR units per se does not result in excessive health care costs.

Cost Control↗
PubMed1997

Dynamic MRI of meningiomas and schwannomas: is differential diagnosis possible?

We studied 23 patients with meningiomas and 14 with schwannomas using dynamic spin-echo (TR/TE 200/15 ms) MRI. Histologically the meningiomas were classified according to the 1993 WHO classification. Serial images were obtained every 30s for 210s after rapid injection of gadopentetate dimeglumine (0.1 mmol/kg). The contrast-enhancement ratio (CER) was divided into three patterns; a sharp rise with a peak within 60 s (A), a relatively rapid increase with a peak between 60 and 210s (B), a slow increase without a peak (C). The patterns were correlated with the histology of the tumors. The signal intensities of the tumours on T2-weighted images were also analyzed and correlated with the dynamic patterns. Meningiomas had more varied dynamic patterns than schwannomas. Almost half of the meningiomas showed pattern A, and one third pattern C. Of six meningiothelial meningiomas showed pattern A; all schwannomas and fibrous meningiomas showed pattern C. Various patterns were observed in transitional meningiomas. Of the 8 meningiomas showing pattern C, only one gave high signal on T2-weighted images, and could not be differentiated from the schwannomas. Thus, one third of meningiomas could not be differentiated from schwannomas by the dynamic contrast enhancement alone. However, when this was combined with the signal intensity on T2-weighted images, most meningiomas could be differentiated from schwannomas.

Brain↗
PubMed1997

Variable tip angle slab selection pulses for carotid and cerebral time-of-flight MR angiography. Theory and experimental analysis.

OBJECTIVE: To determine the optimal parameters of variable tip angle slab selection (tilted optimized nonsaturating excitation, TONE) pulses in time-of-flight MR angiography, in order to produce the best visualization of vessels distal to the entry partition. MATERIAL AND METHODS: The influences of the mean flip angle (MFA) and the profile tilt of the TONE pulse in three-dimensional (3D) time-of-flight MR angiography were evaluated with a mathematical modeling of the flow signal amplitude. We compared the calculated flow signals with the signals from flow-phantom models and with those from 6 normal volunteers. 3D gradient echo images (TR/TE 30/7) were acquired with a single variable of the MFA and the profile tilt. The flow velocity of the phantom was maintained at 15 cm/s. Regions of interest were measured on the source images. We also evaluated the visualization of the cerebral vessels on maximum intensity projection images obtained with and without TONE pulses in 5 other healthy volunteers. RESULTS: The changes of flow signals in the phantom and in the volunteers were in good accord with those of the signals mathematically predicted and plotted by a computer, as each parameter was varied. The peripheral saturation was weaker at smaller MFA than at larger MFA. A greater profile tilt produced a more pronounced TONE effect than a lower one. The visualization of the peripheral cerebral vessels was markedly improved by the addition of the TONE pulse. CONCLUSION: Computer simulation is useful for examining the optimal TONE parameters. The TONE pulse markedly improves the visualization of the distal branches of the cerebral vessels.

Adult↗
PubMed1997

Orbital pseudotumors: value of short inversion time inversion-recovery MR imaging.

PURPOSE: To evaluate magnetic resonance (MR) signal intensities of orbital pseudotumors on short inversion time inversion-recovery (STIR) images and to predict the effect of treatment. MATERIALS AND METHODS: Sequential MR examinations were performed in 17 patients with orbital pseudotumors, before and after treatment. All patients underwent MR imaging with T1- and T2-weighted spin-echo or fast spin-echo sequences, and STIR sequences with two 0.5-T systems. Quantitatively and qualitatively, the differences in signal intensities among three therapeutic response groups (good, mild, and no responses) were analyzed for each pulse sequence. RESULTS: Quantitatively, both contrast and contrast-to-noise ratio on STIR images corresponded well to the results of response to therapy for all background markers; contrast and contrast-to-noise ratio values in the good response group were the largest, while those in the no response group were the smallest (P < .0001). Qualitatively, the signal intensities of the lesions in the good response group were interpreted as hyperintense to the cerebral cortex in 14 (93%) or 11 (73%) of 15 lesions by two observers, respectively, while in the no response group, both observers assessed 16 (89%) of 18 lesions as hypo- or isointense to the muscle (P < .0001). CONCLUSION: STIR images showed a variety of signal intensities in the lesions, and the signal intensities on the STIR images helped predict the response to the therapy in orbital pseudotumors.

Adult↗