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Biomedical subjects

I Shirouzu

Publications and source records attributed to I Shirouzu.

At least 19 recordsLinked to original sources
PubMed2003

Physical characteristics of low and medium energy collimators for 123I imaging and simultaneous dual-isotope imaging.

Septal penetration of high energy photons may degrade 123I images obtained with a low energy collimator. We evaluated the physical characteristics of a low energy, high resolution (LEHR) collimator, special LEHR (SLEHR) collimator, and medium energy collimator for 123I studies. The cross-talk of 99mTc and 123I into the 201Tl window was also examined. Sensitivity and spatial resolution were measured with each collimator. Point sources of 99mTc and 123I were imaged at various source-collimator distances using multiple energy windows, and the effects of collimator choice on energy spectrum and spatial distribution of photopeak counts were assessed. For 99mTc, both sensitivity and resolution were similar with the low energy collimators, and higher sensitivity and lower resolution were observed with the medium energy collimator. For 123I, the full width at tenth maximum was larger for 123I than for 99mTc when using the LEHR collimator. Acquisitions with multiple energy windows revealed severe degradation due to septal penetration in imaging 123I with the LEHR collimator, especially at short distances. The degradation was reduced with the SLEHR collimator and further with the medium energy collimator. In both 99mTc and 123I imaging, cross-talk into the 201Tl window was larger at shorter distances and the largest with the LEHR collimator. In conclusion, variation in collimator geometry causes differences in the effect of septal penetration on 123I images and in cross-talk into the 201Tl window. The SLEHR collimator may be suitable for use in high resolution 123I imaging and simultaneous 99mTc/201Tl imaging. Use of the medium energy collimator appears to be preferable in quantitative 123I studies.

Equipment Failure Analysis↗
PubMed2002

Hemiparkinsonism associated with a mesencephalic tumor.

A 66-year-old woman presented with a 3-year history of progressive right-sided hemiparkinsonism manifested by a right-hand resting tremor and right-sided bradykinesia. Magnetic resonance imaging (MRI) of the brain revealed a non-enhanced polycystic mass in the left midbrain. (11)C-methylspiperone ((11)C-NMSP) and (18)F-fluorodopa ((18)F-DOPA) positron emission tomography (PET) revealed a striatal hypometabolism that was restricted to the left side. These findings are consistent with a dysfunction in the left nigrostriatal dopaminergic pathway that is presumably induced by the cystic mass in the left midbrain. This case is significant due to the paucity of reports regarding the occurrence of a relatively pure parkinsonism that is associated with a mesencephalic space-occupying lesion.

Brain Stem Neoplasms↗
PubMed2000

Temporal changes of the apparent diffusion coefficients of water and metabolites in rats with hemispheric infarction: experimental study of transhemispheric diaschisis in the contralateral hemisphere at 7 tesla.

The purpose of the present study was to clarify the temporal changes of the apparent diffusion coefficients (ADCs) of cerebral metabolites during early focal ischemia using stimulated echo acquisition mode with short echo time at a 7 T magnet to assess the pathophysiology of the reduction in diffusion properties observed both in the ischemic cerebral hemisphere and in the contralateral hemisphere. The ADCs of metabolites in the infarcted hemisphere 1 hour and 3 hours after the onset of ischemia decreased with 25% and 29% for choline containing compounds (Cho), 16% and 26% for creatine and phosphocreatine (Cre), and 19% and 19% for N-acetylaspartate (NAA), respectively, compared with the ADC values 2 hours later in the contralateral hemisphere. There were decreases in the ADC of Cho, Cre, and NAA with 21%, 7%, and 18% 8 hours later, respectively, in the noninfarcted hemisphere, which suggested transhemispheric diaschisis in rats with focal cerebral ischemia. The present study proposed that the diffusion characteristics of the brain metabolites might offer new insights into circulatory and metabolic alteration in the cerebral intracellular circumstance.

Animals↗
PubMed1999

Early diagnosis of central nervous system aspergillosis with combination use of cerebral diffusion-weighted echo-planar magnetic resonance image and polymerase chain reaction of cerebrospinal fluid.

We treated a patient diagnosed as central nervous system (CNS) aspergillosis with the combined use of cerebral diffusion-weighted echo-planar magnetic resonance imaging (DWI) and polymerase chain reaction of the cerebrospinal fluid (CSF-PCR). DWI, a cutting-edge imaging modality to reveal the earliest changes of cerebral infarction, detected cerebral fungal embolization when the conventional computed tomographic scan and magnetic resonance imaging failed to reveal it. CSF-PCR demonstrated the presence of Aspergillus-specific DNA in the specimen, when the conventional examination and culture of CSF were nonspecific or negative. These diagnostic methods could be useful in the early diagnosis of CNS aspergillosis.

Aspergillosis↗
PubMed1998

Physiological analyses of a patient with extreme widening of Virchow-Robin spaces.

We report on a 60-year-old woman with extreme widening of Virchow-Robin spaces who showed neither neurological symptoms nor signs. Magnetic resonance imagings (MRIs) of her brain disclosed multiple abnormalities located along the perforating medullary arteries in the white matter. Central sensory and motor conduction studies (sensory evoked potentials (SEPs) and magnetic stimulation) showed no conduction delays and several modulatory inputs normally influenced the motor and sensory cortical excitability, as expected from clinical features. These physiological analyses confirmed the functional integrity of the central sensory and motor systems, even though imaging studies showed seemingly serious abnormalities.

Brain↗
PubMed1998

Avulsion injury of cervical nerve roots: enhanced intradural nerve roots at MR imaging.

PURPOSE: To study the magnetic resonance (MR) imaging features of intradural nerve roots in avulsion injury of the cervical nerve roots. MATERIALS AND METHODS: Presurgical gadolinium-enhanced MR imaging was performed in 27 consecutive patients. The images were evaluated for enhancement of the intradural nerve roots and enhancement of the spinal cord surface at the root entry zone ("root stump" enhancement) by two radiologists, who were blinded to the clinical information. Intradural nerve roots were classified as enhanced, normal, or not visible. Root stumps were classified as enhanced or normal. The results were compared with the results of nerve root continuity studies (exploratory surgery with intraoperative recording of somatosensory evoked potentials or neurologic examination). RESULTS: At the 250 nerve levels (500 nerve roots) studied, 12 enhanced nerve roots and 42 enhanced root stumps were found. Seven enhanced nerve roots and 38 enhanced root stumps were related to preganglionic injury. Results of the kappa test for interobserver concordance on findings of intradural nerve roots and root stumps were 0.55 and 0.93, respectively. CONCLUSION: Although visualization of nerve roots is a problem, enhanced MR imaging is a noninvasive means of obtaining anatomic information and unique physiologic information on injured intradural nerve roots.

Adolescent↗
PubMed1998

Dental bur fragments causing metal artifacts on MR images.

PURPOSE: Our purpose was to define the role of dental bur fragments in producing metal artifacts on MR images. METHODS: Dental prosthetic reconstructions were made for two dogs. The two lower second premolars were prepared for full-cast crowns by using a diamond bur. The crown margin was placed subgingivally on the right side (1 mm below the free gingival margin) and at the same level as the free gingival margin on the left side. After 1 week, full-cast crowns were cemented in place. MR imaging was performed 7 days later. RESULTS: Metal artifacts appeared in both second premolar regions of the mandible on MR images, with the right side, in which the crown margin was positioned subgingivally, displaying a larger signal distortion than the left side. After removal of the crown, the artifact remained on the right. On histopathologic examination, bur fragments were detected in the gingiva, more on the right than on the left. X-ray fluorescent element analysis showed iron in the gingival tissue containing bur fragments. CONCLUSION: Distortion of MR images was considered to be attributable in part to the damage of the gingiva and in part to the presence of dental bur fragments.

Animals↗
PubMed1997

Motor cortical reflex myoclonus: a case study with MEG.

Cortical reflex myoclonus usually depends for its generation on the hyperexcitability of sensory cortex, which manifests itself as an enhanced somatosensory evoked potential (SEP). A 25-year-old female, presenting with involuntary jerky dorsiflexion of the left foot, was found to have cortical reflex myoclonus which was aggravated during intended movements. The jerks were also elicited by electrical stimulation of the posterior tibial nerve, although the SEP evoked by the same stimulus was normal in latency and amplitude. Both the spontaneous spikes and the premyoclonus spike demonstrated by jerk-locked back averaging were localized to the superior frontal gyrus, just anterior to the paracentral sulcus. Paired-pulse magnetic stimulation disclosed lack of inhibition in the right hemisphere leg motor area, whereas the excitability of sensory cortex as studied by paired SEP testing was normal. This suggests that the myoclonus was caused mainly by enhanced excitability of the motor cortex and that this alone was enough for the production of long loop reflexes. We propose to designate this type of cortical myoclonus as motor cortical reflex myoclonus. It is generated in the motor cortex, but is at the same time stimulus-sensitive.

Adult↗
PubMed1995

Enhancement of the intracranial arterial wall at MR imaging: relationship to cerebral atherosclerosis.

PURPOSE: To investigate the relationship between intracranial arterial wall enhancement and atherosclerosis. MATERIALS AND METHODS: Intracranial vertebral arteries of 30 patients and carotid arteries of 62 patients were studied with spin-echo magnetic resonance imaging with contrast enhancement and spatial presaturation. Arterial wall enhancement was graded as follows: stage 1, no substantial enhancement; stage 2, faint or thin area of enhancement; stage 3, definite and thick area of enhancement. RESULTS: In vertebral arteries, stage 3 enhancement was seen in 11 patients (mean age, 73.7 years) and stage 1 in eight (mean age, 56.4 years). In carotid arteries, stage 3 enhancement was seen in 13 patients (mean age, 71.0 years) and stage 1 in 21 patients (mean age, 39.0 years). In both arteries, stage was well correlated with age (P < .05). CONCLUSION: Arterial wall enhancement is related to aging and is probably due to neovascularity in association with atherosclerotic plaques. This finding may permit assessment of intracranial atherosclerosis and other vascular diseases.

Adult↗
PubMed1993

Posterior cranial fossa dural arteriovenous malformation with a varix mimicking a thrombosed aneurysm: case report.

Dural arteriovenous malformations (AVMs) in the posterior cranial fossa are relatively infrequent. Intradural haemorrhage is one of their specific complications. Angiographic demonstration of varices or aneurysmal structures is one of the hallmarks of severe cases. We report a patient with posterior cranial fossa dural AVM associated with a varix mimicking a thrombosed aneurysm on CT and MRI. Internal carotid and vertebral angiography failed to demonstrate an aneurysm, but external carotid injection revealed a dural AVM affecting the sigmoid sinus, and a varix. The AVM was completely eliminated by embolization. When a dural AVM is suspected clinically selective angiography should be performed to confirm the diagnosis even when CT or MRI do not show dilated vessels.

Cerebral Angiography↗
PubMed1993

Acquired epidermoid tumour in the thoracic spinal canal.

Acquired spinal epidermoid tumours are rare, and probably caused by skin fragments that have been transplanted by trauma or lumbar puncture. They almost always occur in the region of the cauda equina. We present an acquired spinal epidermoid tumour at the T 10 level, with pathological confirmation. A skin fragment had migrated to a site where it developed into a tumour.

Epidermal Cyst↗
PubMed1993

Postaortic left innominate vein: radiological assessment and pathogenesis.

Postaortic left innominate vein (PALIV) is a rare venous anomaly and the findings on plain chest radiographs have not been well described. Plain chest radiographs, CT and MR of nine adults known to have PALIV were reviewed. They all showed a high aortic arch, including four with a right-sided aortic arch and one with a double aortic arch, in postero-anterior radiographs, and seven showed curved shadows in the left upper mediastinum. On all lateral chest radiographs (n = 5), the superior retrosternal region was opacified by the high aortic arch. CT or MR images confirmed the aortic arch and/or innominate artery to be in that part of the retrosternal space, normally occupied by the left innominate vein, in all cases. Association of a curved shadow in the superior mediastinum with a high aortic arch on plain chest radiographs is therefore suggestive of, though not diagnostic for, PALIV. This entity was well documented by CT or MR and the radiological findings were considered to imply that developmentally PALIV is secondary to a high position of the aortic arch.

Adult↗
PubMed1990

[Clinical usefulness of 67Ga-citrate scintigraphy combined early image in malignant lymphoma--detection of abdominal lesions].

In order to improve the diagnostic accuracy in detecting abdominal lesions of malignant lymphoma, we studied prospectively the usefulness of 67Ga-citrate scintigraphy combined 5 to 6-hour early image with conventional 72-hour delayed image after injection. During the period from July 1986 to September 1988, total 41 67Ga-citrate scintigrams performed on 28 patients with malignant lymphoma (3 Hodgkin's disease, 25 non-Hodgkin lymphoma) were evaluated between early and delayed image regarding to such points as follows; 1) the physiologic bowel uptake of 67Ga-citrate, 2) detection of abdominal lesions indicated by other diagnostic modalities involving computed tomography, lymphography and ultrasonography. Following results were obtained: 1) Prominent bowel uptake of 67Ga-citrate thought to be difficult to interpret the scintigram was observed in only 1 of 41 (2%) on early image versus 13 of 41 (32%) on delayed image. 2) Known lesion sites were detected in 24 of 31 (77%) on early image versus 21 of 31 (68%) on delayed image, resulting in 26 of 31 (84%) in combination with both images. 3) There were 2 false-positive and 5 false-negative lesions. Two false-positive lesions on early image were explained by physiologic hepatic uptake with ill-defined outline and bladder uptake. On the other hand, all of 5 lesions on delayed image were explained by prominent bowel uptake. 4) Two patients were revealed higher splenic uptake comparing with hepatic uptake on both images, later proved to be diffuse splenic involvement without evidence of lesions on other diagnostic modalities. 5) The lesions less than 2 cm in diameter could not be detected in both images.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdominal Neoplasms↗
PubMed1989

[CT appearance of uterine adenomyosis].

CT findings in 37 cases with pathological diagnosis of uterine adenomyosis were reviewed retrospectively. The attenuation coefficient of adenomyosis is almost same as normal parenchyma on both plain and enhanced CT. The margin was obscure except for one case. In focal type, deviation of the endometrium and deformity of the uterus may be a clue to the detection of adenomyosis. But differential diagnosis of adenomyosis from leiomyoma with ill-defined margin was very difficult. In diffuse type, the uterine body is swollen without deviation of the endometrium. This type can be diagnosed if the endometrium identified clearly.

Adult↗