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Biomedical subjects

K Houkin

Publications and source records attributed to K Houkin.

At least 109 records · Page 6Linked to original sources
PubMed1994

In vivo proton magnetic resonance spectroscopy for metabolic changes of human brain edema.

The metabolism of the brain was investigated in eight patients with peritumoral edema, six patients with ischemic stroke, and 28 normal controls using proton magnetic resonance (MR) spectroscopy. The MR studies were performed using a 1.5-T whole-body imaging and spectroscopy system with a 1500-msec repetition time (TR) and a 270-msec echo time (TE). The peak areas for N-acetyl-aspartate (NAA), choline-containing compounds (Cho), creatine and phosphocreatine (Cr), and lactate (Lac) were measured, and the NAA/Cr, Cho/Cr, and Lac/Cr ratios were calculated. To quantify and compare the serial spectra, relaxation effects were investigated by acquisitions at two different points (TRs or TEs) and by monoexponential fitting. The normal NAA/Cr and Cho/Cr ratios were 2.76 and 1.09, respectively. Lac could not be identified in normal brains. In ischemic stroke and peritumoral edema, significantly increased Lac/Cr and decreased NAA/Cr ratios were observed. Resolution of peritumoral edema was associated with normalized NAA/Cr ratio and disappearance of Lac. The T1 relaxation times of the metabolites were similar in normal brain and peritumoral edema, but the T2 values were significantly shortened. Serial measurements of T2 values in two patients with peritumoral edema showed gradual normalization corresponding to improvement of the edema. To absolutely quantify metabolite concentrations in edema, changes in relaxation times should be considered.

Adult↗
PubMed1993

The cerebrospinal fluid in patients with moyamoya disease (spontaneous occlusion of the circle of Willis) contains high level of basic fibroblast growth factor.

The level of basic fibroblast growth factor (bFGF) in cerebrospinal fluid (CF) was measured by an EIA in 15 patients with moyamoya disease, in 11 patients with atherosclerotic occlusive disease, and in 8 patients with spinal disc disease. In the moyamoya patients, bFGF was found in 13 out of 15 CF samples with a mean value of 101 pg/ml. However, bFGF was detected in only 4 out of 11 patients with atherosclerotic disease with a mean of 8 pg/ml. In all the patients with disc disease, bFGF was not detected. The elevated level of bFGF may play a crucial role in the pathogenesis of moyamoya disease.

Adult↗
PubMed1993

Identification of central sulcus by using somatosensory evoked magnetic fields and brain surface MR images: three dimensional projection analysis.

We present a novel non-invasive technique for identification of the central sulcus on the brain surface by using three-dimensional magnetic resonance imaging (3D-MRI) in combination with somatosensory evoked magnetic fields (SEFs). The central sulcus was supposed anatomically on the brain surface by using 3D-MRI. On the other hand, the primary somatosensory area is determined by using SEF data with median nerve stimulation. Superimposition of the SEFs of the 25 ms response onto the brain surface MR images clearly demonstrated the dipole source located in the gyral fold just behind the supposed central sulcus in all subjects analyzed. Three-dimensional reconstruction of the brain surface image data facilitated visualizing the precise anatomical localization of the magnetic field activities from any angle and measuring the distance from the source to any point of interest. The potential clinical application of this technique is discussed.

Adult↗
PubMed1993

Longitudinal changes in proton magnetic resonance spectroscopy in cerebral infarction.

BACKGROUND AND PURPOSE: Proton magnetic resonance spectroscopy has revealed changes in lactate and N-acetyl-aspartate in acute cerebral infarction. However, the details of these drastic changes and subsequent chronic changes have not been clarified. The purpose of this study was to disclose longitudinal changes in spectra seen in proton magnetic resonance spectroscopy. METHODS: Six patients with completed cerebral infarction were examined longitudinally with localized proton magnetic resonance spectroscopy. RESULTS: (1) In the acute stage (within 2 days after onset), two drastic changes were observed: N-acetyl-aspartate decreased rapidly and severely within 2 days after onset, and lactate increased immediately and reached a high level in the acute stage after onset. (2) In the chronic stage (more than 1 month after onset), two features were observed: lactate, which had increased in the acute stage, remained high for more than 1 month, and other signals such as those of N-acetyl-aspartate, choline, and phosphocreatine/creatine decreased dramatically. CONCLUSIONS: These results suggest that N-acetyl-aspartate and lactate as revealed by proton magnetic resonance spectroscopy can be useful indicators of the ischemic damage to the brain in clinical cases of cerebral infarction.

Adult↗
PubMed1993

Acetazolamide test in detecting reduced cerebral perfusion reserve and predicting long-term prognosis in patients with internal carotid artery occlusion.

In a series of 32 patients with internal carotid artery occlusion, regional cerebral blood flow (rCBF) and regional cerebral vasoreactivity (rCVR) were measured by xenon-133 single photon emission computed tomography and the acetazolamide test. We evaluated its usefulness in detecting the reduced cerebral perfusion reserve and predicting long-term prognosis. All Type 1 patients (normal rCBF and rCVR) were medically treated and experienced no recurrent ischemic attack. Cerebral hemodynamics remained unchanged. Type 2, 3, and 4 patients underwent superficial temporal artery-middle cerebral artery double anastomosis, if they consented to surgery. All Type 2 (normal rCBF and reduced rCVR) and Type 3 (reduced rCBF and rCVR) patients, who underwent surgery, showed no further ischemic attacks, as well as long-term normalization of rCVR, although long-term rCBF normalization was obtained in only three of seven Type 3 patients. Cerebral hemodynamics remained unchanged in Type 4 patients after surgery. In follow-up periods, major completed stroke occurred in all 3 Type 2 and Type 3 patients who were medically treated. These results suggest that the acetazolamide test is valuable in assessing the cerebral perfusion reserve and predicting long-term prognosis in patients with internal carotid artery occlusion, although further long-term or randomized studies are needed.

Acetazolamide↗
PubMed1993

Functional neurosurgical simulation with brain surface magnetic resonance images and magnetoencephalography.

We present a novel noninvasive technique for functional neurosurgical simulation combining three-dimensional magnetic resonance imaging of the brain surface with somatosensory evoked magnetic fields (SEFs) in a case of subcortical brain tumor. The preoperative analysis using this technique revealed that the central sulcus was located between the SEF source projected onto the brain surface and the tumor. At the time of surgery, the central sulcus was clearly identified by phase reversal of the cortical recordings of somatosensory evoked potentials. The actual cortical anatomy and the maximum somatosensory evoked potential location showed excellent agreement with the preoperative analysis of the brain surface magnetic resonance images and the SEF source. The subcortical tumor, which was barely identifiable without reliable functional cortical anatomy, was easily found in the motor area, just before the somatosensory evoked potential (and SEF) source. The potential clinical application of this technique is discussed.

Brain Mapping↗
PubMed1993

Visualization of the ostium of an arteriotomy in bypass surgery.

Visualization of the ostium of an arteriotomy by staining it blue with methylrosaniline chloride (pyoctaninum blue) in anastomotic bypass surgery for children with moyamoya disease is described. This technique enables surgeons to create an anastomosis more precisely and quickly. No adverse effects were observed.

Anastomosis, Surgical↗
PubMed1993

Cerebral blood flow in children with spontaneous occlusion of the circle of Willis (moyamoya disease): comparison with healthy children and evaluation of annual changes.

Changes in the mean cerebral blood flow (mCBF) with growth in normal children (1-20 years old) were evaluated, and compared to serial mCBF changes in children with spontaneous occlusion of the circle of Willis (moyamoya disease) after vascular reconstructive surgery. mCBF gradually decreased with growth in control children. Preoperative mCBF was similar or decreased in moyamoya disease patients with transient ischemic attack, and slightly decreased in those with cerebral infarction. Postoperative mCBF gradually decreased similarly to physiological changes with growth in controls. These results suggest that changes with age should be considered when preoperative and long-term cerebral hemodynamics are evaluated in children with moyamoya disease.

Age Factors↗
PubMed1993

Clinical application of angioscopy during carotid endarterectomy for patients with internal carotid artery stenosis.

The accuracy of angioscopy in detecting atherosclerotic changes, such as plaque, ulcer, and mural thrombus, in the extracranial cerebral arteries was evaluated during carotid endarterectomy by comparison with angiographic and operative findings. Ten patients with internal carotid artery stenosis underwent intraoperative angioscopy during surgery. After clamping the carotid bifurcation, intra-arterial atherosclerotic lesions were observed with an angioscope (0.8 or 1.4 mm outer diameter) inserted through a small incision in the common carotid artery. Angioscopic findings correlated well with both angiographic and operative findings in six patients, and provided additional information in two patients, such as organized thrombi within the ulcer and mural thrombi. Angioscopic findings were quite different to those from angiograms in two patients. In one, an ulcer on angiograms was false positive, and in the other, false negative. These findings were confirmed intraoperatively. Our results suggest that preoperative carotid angioscopy is of great value in detecting ulcers more accurately than angiography, and in selecting candidates for carotid endarterectomy, although further development of equipment is needed.

Adult↗
PubMed1993

[Analysis of cerebral blood flow dynamics and evaluation of extracranial-intracranial arterial bypass function using magnetic resonance angiography with presaturation pulse sequence].

Magnetic resonance (MR) angiography was applied to the study of blood flow dynamics and evaluation of extracranial-intracranial arterial bypass function in patients who had received bypass surgery. Three-dimensional gradient-echo acquisitions with selective presaturation of individual vessels were used to determine the direction of blood flow. Presaturation causes signal loss within the territory supplied by the presaturated artery, without affecting vessels not coursing through the presaturation slab. The patency of arterial bypass graft could be demonstrated as properly with MR angiography as with conventional angiography. In addition to that, MR angiography with presaturation pulse clearly demonstrated the direction of blood flow and the territory supplied by arterial bypass graft. The results were correlated with those from transcranial Doppler sonography and conventional angiography. We concluded that MR angiography is a noninvasive useful method for the evaluation of dependency on post-surgical collaterals and bypass function.

Aged↗
PubMed1993

[Usefulness and limitation of MR imaging and MR angiography in diagnosis of juvenile moyamoya disease].

Magnetic resonance (MR) images and MR angiograms (MRA) were studied in 20 childhood cases of moyamoya disease. Both MRI and MRA successfully demonstrated moyamoya vessels in the basal ganglia in all cases, with a positive but not definite correlation to the conventional angiographic findings. MRI depicted the stenotic and occlusive lesions of the carotid fork and horizontal portion of the middle cerebral artery effectively. MRA demonstrated some lesions which even MRI failed to prove, but it tended to overestimate the lesions. Post-operative state of collateral flow and the patency of EC-IC bypass graft could be evaluated as accurately with MRA as with conventional angiography, although MRA was limited in spatial resolution and evaluation of flow direction. In conclusion, MRI and MRA were considered to be useful in the diagnosis of moyamoya disease in stage 3 and 4, but less effective in the evaluation of its angiographical stage.

Child↗
PubMed1993

[Diagnosis of intracranial occlusive vascular disease and evaluation of extracranial-intracranial (EC/IC) arterial bypass using three-dimensional magnetic resonance angiography].

The three-dimensional time-of-flight (TOF) magnetic resonance angiograms (MRA) were studied to evaluate its accuracy in the assessment of the intracranial carotid occlusive lesions, collateral circulation and also the patency of extracranial-intracranial (EC/IC) arterial bypass surgery. All occlusive lesions of the intracranial major arteries seen in conventional angiograms were revealed clearly with MRA. However MRA had its practical limitation in the evaluation of the leptomeningeal anastomosis (collateral circulation) probably due to the deterioration of contrast in its slow flow and saturation effect of the magnetization. In addition to that, MRA often exaggerated the severity of the stenotic lesions, mostly in severe cases. The post-operative state of collateral flow and the patency of EC/IC bypass could be evaluated as properly with MRA as with conventional angiography, although MRA was limited in spatial resolution and evaluation of flow direction. In conclusion, MRA was considered t be a reliable non-invasive modality as a screening examination for the evaluation of the carotid occlusive disease and as the follow-up study of the post-operative patients with EC/IC bypass surgery.

Carotid Artery Diseases↗
PubMed1992

[Clinical application of phase contrast angiography].

"Phase Contrast Angiography" is a new technique of Magnetic Resonance Angiography as reported by Dumoulin CL et al. Using this technique, we can obtain images of vessels (angiograms) without injection of contrast medium. We present the results of phase contrast angiography on cerebral and spinal vascular disease. We utilized the General Electric SIGNA, 1.5 tesla NMR. One hundred and ninety-one cases of cerebral and spinal vascular diseases were scanned using phase contrast angiography. Included were 90 cases of occlusive vascular disease, 16 cases of moyamoya disease, 39 cases of arteriovenous malformation, and 28 aneurysms. The phase contrast angiography uses flow encoding gradient pulses, which impart a velocity-dependent phase shift to the transverse magnetization of moving spins. The resulting image contains only information from the moving spins; while information from stationary tissue remains suppressed. In cases using 3-D angiogram, we made 32 images 6 degrees apart in their projection direction and displayed them on a video terminal. We were able to visualize occlusions of vessels, aneurysms, bypassed vessels, and abnormal vessels of arteriovenous malformations. Retrospective evaluation comparing phase contrast angiography with conventional angiography of the stenotic findings on the horizontal portion of middle cerebral arteries (64 vessels of 32 patients), resulted in a false positive ratio of 39.1%. We obtained clinically valuable results regarding the hydrodynamics of patients using "phase contrast angiography" non-invasively. These results reveal not only "anatomical" images of vessels, but also "functional" images, which are sensitive to the pattern of the blood flow. This study would strongly suggest that phase contrast angiography presents a valuable tool for the clinical diagnosis of cerebral and spinal vascular diseases.

Cerebral Angiography↗
PubMed1992

[Evaluation of cerebral blood circulation using fast magnetic resonance imaging (turbo-FLASH)].

In its initial stage of development, poor time resolution was supposed to be inevitable for magnetic resonance imaging (MRI). The development of the gradient echo technique, however, has made an opening for a breakthrough to a fast MRI technique. However, conventional gradient echo technique is not fast enough to disclose the cerebral blood circulation. A new technique (turbo-FLASH), which combines gradient echo and preparation pulse, has opened the door to a true dynamic (high time resolution) MRI. The authors performed a basic study of this new fast imaging technique (Turbo-FLASH) for the evaluation of cerebral blood circulation. Using this dynamic MRI, the conventional Gd-DTPA administration (0.1mmol/kg, intravenous manual administration) has produced sufficient contrast to reveal a difference of the extent of enhancement between normal gray matter and white matter. In patients of cerebral infarction, the infarcted brain does not show any significant increase of signal intensity after the administration of contrast medium, whereas the normal brain shows a sharp increase of signal intensity after the administration of contrast medium. Indeed, many puzzling questions remain to be solved for clinical application of this new dynamic MRI. For example, the optimal quantity of contrast medium and optimal parameters for this sequence (T1 weighted or T2 weighted?) are still unknown. But, in any case, this dynamic MRI is expected to be a clinically powerful tool for the evaluation of cerebral blood flow.

Brain↗
PubMed1992

[Quantitative analysis of cerebrospinal fluid dynamics in syringomyelia using cine MRI with pre-saturation].

Some reports show the qualitative analysis of cerebrospinal fluid (CSF) pulsation in the subarachnoid space and the syrinx using cine magnetic resonance imaging (MRI). However, few reports studied the quantitative analysis of CSF pulsation. We report here the results of quantitative analysis of CSF pulsation using the cine MRI with pre-saturation pulse. Using flow phantom, we calibrated the correlation between the true velocity and calculated velocity acquired from the movement of pre-saturated low signal. Three cases of syringomyelia with Chiari malformation, two cases of traumatic syringomyelia, and three normal volunteers were examined using this technique, and we could obtain time-velocity curves of CSF in both subarachnoid spaces and syrinx. Although obvious pulsation of CSF was observed in the syrinx of all Chiari malformations, no pulsation of CSF was observed in the syrinx of traumatic syringomyelia. CSF in the syrinx moves upward in the early systolic cardiac cycle, downward in the systolic cycle, and upward again in the diastolic cycle. Patterns of CSF pulsation in syrinx were similar to those in the subarachnoid space, but "phase" of these pulsations differed from case to case. These results suggest the close relationship between CSF pulsation in the syrinx and CSF obstruction at the cranio-vertebral junction. Dissociation of the "phase" of CSF pulsation in the syrinx and subarachnoid space may be significant in the analysis of the pathogenesis of syringomyelia.

Adult↗
PubMed1992

[Anatomical analysis of the sources of somatosensory evoked fields (SEFs) using 3D-MRI].

We have recorded short latency somatosensory evoked magnetic fields (SEFs) to left median nerve stimulation in three healthy subjects. The locations of the deduced dipole sources were projected onto the 3-Dimensional magnetic resonance imaging (3D-MRI) of the individual subjects providing an anatomical localization. We found that the deduced sources were located at the primary sensorimotor hand area on the posterior surface of the central sulcus, at an average depth of 26mm (11mm) from the scalp (brain surface). This technique that combined MEG with 3D-MRI was able to precisely determine source locations and analyze the relationships between dipole sources and brain structures. By using this technique, we can confirm functional anatomy of the brain noninvasively, and obtain much useful information preoperatively and during operation.

Adult↗