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S Imakita

Publications and source records attributed to S Imakita.

At least 19 recordsLinked to original sources
PubMed2001

Embolic distribution through patent foramen ovale demonstrated by (99m)Tc-MAA brain SPECT after Valsalva radionuclide venography.

UNLABELLED: Cryptogenic stroke might relate to paradoxical embolism stemming from right-to-left shunt caused by patent foramen ovale (PFO). We performed radionuclide venography using the Valsalva maneuver, followed by (99m)Tc-macroaggregated albumin (MAA) brain SPECT to investigate the fate of emboli originating from the lower extremities. METHODS: Ten patients (9 men, 1 woman; mean age, 61 +/- 17 y) with PFO underwent radionuclide venography with and without the Valsalva maneuver on the whole-body image, followed by brain SPECT with (99m)Tc-MAA to determine the cortical uptake that would detect right-to-left shunt. After counts in each region of interest (ROI) were normalized by comparison with the averaged count, the distribution of MAA was compared with that of (99m)Tc-hexamethyl-propyleneamine oxime (HMPAO) brain SPECT by drawing ROIs on frontal, temporoparietal (anterior circulation territory), occipital, and cerebellar areas (posterior circulation territory). RESULTS: The thyroid on the whole-body scan was visualized after the Valsalva maneuver in 2 of the 10 patients. In 7 of 10 patients, 56 ROIs in the visualized cortical uptake showed that the distribution of MAA correlated well with that of HMPAO according to the equation: HMPAO = -71.21 + 1.71 x MAA, (r = 0.575, P < 0.01). The excess difference in the relative counts in the posterior over anterior circulation territory was 5.6% and 16.1% of the HMPAO and MAA values, respectively. CONCLUSION: Brain SPECT with (99m)Tc-MAA was more sensitive than thyroid visualization in detecting right-to-left shunt. The excess flow in the posterior cerebral circulation indicated an increased likelihood of cerebral emboli originating from the lower extremities and indicated that the flow difference between HMPAO and MAA probably resulted from poor linearization of HMPAO in the high-flow area.

Adult↗
PubMed2000

Hemodynamic and metabolic state of hyperfixation with 99mTc-HMPAO brain SPECT in subacute stroke.

By means of positron emission tomography (PET), we investigated the hemodynamic and metabolic state of the hyperfixation identified as the increased accumulation with 99mTc-d,l-hexamethylpropyleneamine oxime (HMPAO) by single photon emission computed tomography (SPECT) in patients with subacute stroke. We studied four patients with subacute stroke having hyperfixed areas evaluated with CBF, CMRO2, OEF and CBV by PET. The hyperfixation rate with 99mTc-HMPAO was obtained by comparing the surplus rate with standardized CBF. The OEF and CMRO2 values in the hyperfixed areas of 4 patients were significantly lower than those in normal 5 controls (p < 0.01), but CBF and CBV were almost the same in patients and normal controls, but the hyperfixation rate of 0.30 +/- 0.15 in 4 patients correlated well with CBV (r = 0.97, y = 11.75x + 0.42; p < 0.05). Hyperfixation with 99mTc-HMPAO in the infarct area revealing a mismatch between CMRO2 and CBF meant relative luxury perfusion. The hyperfixation rate determined by 99mTc-HMPAO brain SPECT correlated with CBV in the PET study. We can conclude that one of the main factors which caused hyperfixation was vasodilatation as well as the blood brain barrier disruption and the neovascularization.

Adult↗
PubMed1999

Intracranial aneurysms: detection with three-dimensional CT angiography with volume rendering--comparison with conventional angiographic and surgical findings.

PURPOSE: To assess the diagnostic accuracy of three-dimensional (3D) computed tomographic (CT) angiography for intracranial aneurysms. MATERIALS AND METHODS: The 3D CT angiograms obtained in 49 patients with or without intracranial aneurysms were evaluated by four blinded observers. Results were compared with findings at conventional angiography or surgery. A volume-rendering method was used, and 13 images obtained in different directions were reviewed in each study. The diameter of aneurysms was divided into four sizes: large, greater than 13 mm; medium, 5-12 mm; small, 3-4 mm; and very small, less than 3 mm. Results were also evaluated by means of receiver operating characteristic analysis. RESULTS: At conventional angiography, 47 aneurysms, including 14 less than 3 mm, were depicted in 35 patients. The mean sensitivity of CT angiography for very small aneurysms was 64%; small, 83%; medium, 95%; and large, 100%. Some very small aneurysms that were not depicted at conventional angiography were depicted at CT angiography, and one was proved at surgery. CONCLUSION: CT angiography has good sensitivity for depiction of intracranial aneurysms 3 mm or larger and relatively good sensitivity for aneurysms less than 3 mm. CT angiography may be a noninvasive technique for detection of asymptomatic unruptured or ruptured aneurysms.

Adult↗
PubMed1999

Value of diffusion-weighted imaging and apparent diffusion coefficient in recent cerebral infarctions: a correlative study with contrast-enhanced T1-weighted imaging.

BACKGROUND AND PURPOSE: The clinical usefulness and the time course of diffusion-weighted imaging and apparent diffusion coefficient (ADC) in acute and subacute cerebral infarction have not yet been established, although it is known that contrast-enhanced T1-weighted spin-echo imaging can detect a subacute infarct. Our aim was to study which imaging technique is useful in detecting recent infarcts, and whether an increase in ADC or a decrease in signal intensity on diffusion-weighted images is correlated with enhancement on T1-weighted spin-echo images. METHODS: Forty-one infarctions with a duration of 9 hours to 27 days were studied in 29 patients. The ADC and signal intensity on diffusion-weighted images were compared with the contrast-enhancement ratio (CER) on T1-weighted spin-echo images (CER = signal intensity after contrast injection/signal intensity before contrast injection). RESULTS: ADC was linearly correlated with CER, and signal intensity on diffusion-weighted images was inversely correlated with CER. The correlation between ADC and age of the infarct in the subacute phase was weak. CONCLUSION: Diffusion-weighted and contrast-enhanced T1-weighted spin-echo images complement each other in detecting subacute infarcts. Neovascularization and disruption of the blood-brain barrier in infarcts can be important in increasing ADC in subacute infarcts.

Aged↗
PubMed1999

[MR angiography of steno-occlusive lesions of intracranial arteries: a comparative study between turbo MRA and conventional MRA].

PURPOSE: To compare the quality and diagnostic accuracy of images of intracranial steno-occlusive lesions obtained by conventional MRA and turbo MRA reconstructed using the zero-filled interpolation technique in the slice-select direction. MATERIALS AND METHODS: Eighteen patients with suspected steno-occlusive lesions of the intracranial arteries were studied with two types of three-dimensional time-of-flight angiography and conventional digital subtraction angiography. In total, 45 steno-occlusive lesions were quantitatively measured using calipers and correlated with DSA stenosis. A phantom that simulated vessels with stenosis was also imaged using the two types of MRA under the same conditions as those employed in the clinical study. RESULTS: Compared with conventional MRA, turbo MRA reduced the jaggedness of vessels and offered appearances more similar to those of DSA in the antero-posterior and lateral views. The severity of stenosis was classified into five grades based on the percentage of occlusion: not significant (0-24%), mild (25-49%), moderate (50-74%), severe (75-99%), and occlusive (100%). Neither turbo MRA nor conventional MRA showed any discrepancy from DSA above grade-1 stenosis. CONCLUSION: The advantage of turbo MRA is its ability to reduce the jaggedness of vessels on conventional MRA, and to simplify the recognition of vessel contours without prolonging acquisition time. Turbo MRA and conventional MRA have equally high diagnostic accuracy for steno-occlusive lesions.

Aged↗
PubMed1998

Increased bone mineral turnover without increased glucose utilization in sclerotic and hyperplastic change in fibrous dysplasia.

Fibrous dysplasia is a benign bone disorder. It is diagnosed by distinctive X-ray radiography, CT, and MRI findings. Although bone scintigraphy helps to identify the tumor origin according to accelerated bone turnover, the glucose metabolism in fibrous dysplasia has not yet been investigated. We reported a case of fibrous dysplasia in craniofacial bone which showed signs of the acceleration of bone mineral turnover without elevated glucose utilization by Technetium-99m-HMDP SPECT and Fluorine-18-FDG PET. We concluded that the growth of fibrous dysplasia needed the acceleration of bone mineral turnover without an increase in glucose metabolism.

Bone Density↗
PubMed1998

Subtraction CT angiography with controlled-orbit helical scanning for detection of intracranial aneurysms.

PURPOSE: Our goal was to evaluate the utility of subtraction three-dimensional CT angiography for the detection of intracranial aneurysms. METHODS: Thirty-six patients with intracranial aneurysms were examined using newly devised controlled-orbit helical scanning and conventional angiography. Three-dimensional CT angiograms and subtraction 3-D CT angiograms were compared with conventional angiograms for their characterization of intracranial aneurysms. RESULTS: Fifty aneurysms were depicted on conventional angiograms, of which 48 (96%) were seen on the 3-D CT angiograms. Three-dimensional CT angiography was superior or equivalent to conventional angiography for depicting the shape, direction, and location of 33 (66%) of 50 aneurysms; however, it was often less useful than conventional angiography in delineating intracranial aneurysms adjacent to bone. Subtraction 3-D CT angiograms were obtained in 32 patients with a total of 46 aneurysms (in four cases, aneurysms were not depicted owing to excessive motion artifacts), and were superior or equivalent to conventional angiograms in all 46 cases. CONCLUSIONS: Subtraction 3-D CT angiography with the use of controlled-orbit helical scanning is effective in the detection of intracranial aneurysms.

Adult↗
PubMed1996

Intracranial calcification on gradient-echo phase image: depiction of diamagnetic susceptibility.

PURPOSE: To differentiate calcification from hemorrhage on the basis of susceptibility at magnetic resonance imaging. MATERIALS AND METHODS: Gradient-recalled echo (GRE) phase imaging was performed at 1.5 T in 101 calcified areas (15 in the basal ganglia, 86 out of the basal ganglia) and 39 uncalcified locations (13 choroid plexus and pineal glands, 26 old hemorrhages). Experiments with a small lead particle and a numerical simulation were also performed. RESULTS: The majority of calcifications outside the basal ganglia (n = 63) revealed a phase shift that represents diamagnetic susceptibility and was similar to the phase shift in the lead particle and to the calculated phase shift for a diamagnetic sphere. All hemorrhages and almost all calcified basal ganglia revealed a phase shift that represents paramagnetic susceptibility. All uncalcified choroid plexus and pineal glands revealed no obvious phase shift. Any location without calcification did not reveal the diamagnetic phase shift. CONCLUSION: GRE phase imaging differentiated paramagnetic from diamagnetic susceptibility, which was specific for calcification.

Aged↗
PubMed1995

[Three dimensional CT angiography using helical scanning].

Thirty-seven intracranial aneurysms were examined with three dimensional CT angiography (3D-CTA) using helical scanning. The raw data were acquired using a helical CT scanner (X vigor, Toshiba). The collimation was 1 mm or 2 mm, and the table speed was 1 mm or 2 mm/rotation. The contrast medium (iohexol 350) of 1.2-1.5 ml/body weight kg was intravenously injected at an initial rate of 1.5 ml/sec and a second rate of 1.0 ml/sec. The scan delay time was 40-45 sec after the injection of the contrast medium. The 3D-CTA was compared with cerebral angiography (CAG) in the detectability of aneurysms. The 3D-CTA was equal or superior to CAG in 22 aneurysms. The 3D-CTA was less useful in the most aneurysms adjacent to the bone such as aneurysms of internal carotid artery. The subtraction 3D-CTA was useful in the detection of those aneurysms which could not clearly be detected on the 3D-CTA.

Cerebral Angiography↗
PubMed1994

Very early demonstration of secondary pyramidal tract degeneration by computed tomography.

BACKGROUND: While magnetic resonance imaging has revealed progressive changes in the pyramidal tract in accordance with histopathologic stages of wallerian degeneration secondary to a supratentorial lesion, computed tomography (CT) has only demonstrated a shrinkage of the pyramidal tract in the midbrain or pons during the chronic stage. We present a patient with frontoparietal subcortical hemorrhage in whom serial CT scans clearly demonstrated wallerian degeneration along the axis of the pyramidal tract early in the acute stage. CASE DESCRIPTION: A 63-year-old man with a history of hypertension suddenly developed a deterioration of consciousness, transcortical mixed aphasia, and dense hemiplegia on the right side. CT scans revealed a massive intracerebral hematoma in the frontoparietal subcortices of the left hemisphere. Although initial CT did not detect any hypodense areas along the left pyramidal tract below the hematoma, ill-defined areas of decreased density appeared in the posterior limb of the internal capsule, cerebral peduncle of the midbrain, and pontine base of the left side on day 13 after the stroke. These areas became well demarcated on day 22 and persisted thereafter. CONCLUSIONS: An extensive hematoma can interrupt the pyramidal tract fibers that arise not only from the motor cortex and caudal premotor cortex but also from the somatosensory and parietal cortices, allowing very early CT demonstration of wallerian degeneration of the pyramidal tract.

Cerebral Hemorrhage↗
PubMed1993

[Growth rates of aortic aneurysms as a risk factor in rupture: an evaluation with CT].

There is a lack of information on the rates of growth of aortic aneurysms. In the present study, the growth rates and survival rates of thoracic and abdominal aortic aneurysms were determined. One hundred seventy-one patients with aortic aneurysm managed nonoperatively have been followed more than 6 months with sequential X-ray computed tomography. The number of aneurysms was 211 (thoracic aortic aneurysm: 82, abdominal aortic aneurysm: 129). The growth rate of thoracic and abdominal aortic aneurysms were 0.42 and 0.28 cm/year, respectively. Aneurysms at the aortic arch (n = 34) grow at a higher average rate (0.56 cm/year) than aneurysms arising at other levels (p < 0.05). The survival rates showed the tendency that the higher the growth rate, the worse the survival rate. The survival rate of aortic arch aneurysm was significantly decreased when the growth rate was higher than the mean value. It is recommended that thoracic aortic aneurysms, especially aortic arch aneurysms, be followed frequently with computed tomographic examination of size.

Adult↗
PubMed1993

Magnetic resonance imaging of pericardial malignant mesothelioma.

Magnetic resonance imaging of pericardial malignant mesothelioma in two patients is reported. Magnetic resonance imaging clearly depicted the tumor location and expansion, and was useful in delineating the anatomic extent of pericardial malignant mesothelioma.

Adult↗
PubMed1993

Transesophageal echocardiography for detecting intracardiac thrombi in embolic stroke.

The authors studied 56 patients with cardioembolic stroke to search for intracardiac thrombi by use of transesophageal and transthoracic echocardiography. Forty consecutive patients were examined within four weeks of stroke onset and the remaining 16 in the chronic stage. They also performed ultrafast computed tomography in 9 of them. Underlying heart disease was present in all subjects. Anticoagulant therapy had already been started in 29 at the time of examinations. Using their own criteria for echocardiography, they diagnosed intracardiac thrombus in 7 cases and valvular vegetation in 1. Six thrombi were located in the left atrial appendage, 4 of which were smaller than 10 mm in diameter. These small thrombi were not found by either transthoracic echocardiography or computed tomography. Transesophageal echocardiography appears to be superior to the other two methods, especially for detecting small intracardiac thrombi in the left atrial appendage.

Adult↗
PubMed1993

Detection of postural cerebral hypoperfusion with technetium-99m-HMPAO brain SPECT in patients with cerebrovascular disease.

Seventeen of 19 patients (67 +/- 8 yr, 17 males and 2 females) had more than 75% unilateral stenosis or occlusion of the internal carotid or middle cerebral artery and two patients had carotid endarterectomy that previously had 90% stenosis of the internal carotid artery. They were studied during upright 99mTc-HMPAO brain SPECT. HMPA was injected immediately after arising from a supine position. Patients were classified into Group A (n = 10) with occlusion of the internal carotid or the middle cerebral artery or Group B (n = 9) with more than 75% unilateral stenosis of the internal carotid or the middle cerebral artery and with carotid endarterectomy. Additional cerebral blood flow perfusion abnormalities between upright and supine 99mTc-HMPAO brain SPECT were detected in seven patients in Group A and in only one patient in Group B. Semiquantitative analysis showed that the asymmetric ratios between upright and supine positions changed significantly in Group A from 0.82 +/- 0.15 to 0.89 +/- 0.10 (p < 0.01), but not in Group B, from 0.89 +/- 0.11 to 0.92 +/- 0.12 (ns). Additional perfusion abnormalities were relevant to occlusion of the internal carotid or middle cerebral artery indicated postural cerebral hypoperfusion. We conclude that upright 99mTc-HMPAO brain SPECT visualizes postural cerebral hypoperfusion possibly related to silent cerebral ischemia.

Aged↗
PubMed1992

[Growth rate of abdominal aortic aneurysms as measured by Computerized tomography].

To evaluate the growth rate of abdominal aortic aneurysms, sequential computed tomography (CT) examinations were performed on 125 nonoperated patients (M/F 101/24, mean age 67 +/- 8 years, 129 lesions) at intervals of at least 6 months. Growth rates of aneurysms were obtained by subtracting the first from the last diameter and adjusting for examination interval. Mean growth rate was 0.28 +/- 0.26 cm/year. Aneurysms with an initial diameter exceeding 4 or 5 cm showed significantly faster growth than smaller aneurysms. There was no significant correlation between growth rate and atherosclerogenic factors, but systolic blood pressure was significantly higher in patients whose aneurysms ruptured. Our study showed quantitatively that aneurysms with a large diameter have a rapid growth rate, the growth rate of infrarenal aneurysms is significantly faster than that of suprarenal aneurysms, and blood pressure control is important to prevent rupture.

Adult↗
PubMed1992

Visualization of posture-dependent cerebral blood flow in a patient with Takayasu's disease by means of 99mTc-HMPAO brain single photon emission tomography.

A case of Takayasu's disease in a 22-year-old woman who complained of severe fainting attacks is presented. Bilateral obstruction of the cervical arteries was confirmed by digital subtraction angiography. Preoperative technetium-99m hexamethylpropylene amine oxime brain SPET in the sitting position showed bilateral hypoactivity in the temporoparietal areas. Subtraction brain SPET showed slightly increased activity in the lying position. The patient has had no fainting attacks since bypass surgery. Postoperative 99mTc-HMPAO brain SPET in the sitting position showed normal activity except in the right temporoparietal area. This area was filled in the lying position. 99mTc-HMPAO brain SPET is the only technique that can visualize the cerebral blood flow in any position, this capability deriving on the fact that the distribution of 99mTc-HMPAO in the brain is fixed in the first 2-3 min following injection. The use of both sitting and lying 99mTc-HMPAO brain SPET is very useful for detecting an abnormality (i.e. an inhomogeneous response due to the fall in perfusion pressure) that could not be seen if the cerebral blood flow were to be assessed only in the lying position.

Adult↗
PubMed1992

Favorable biodistribution of 99mTc-ECD for brain SPECT comparing with 123I-IMP using alternative body scan.

In order to evaluate the lung and brain uptake of 99mTc ethyl cysteinate dimer (99mTc-ECD) and N-isopropyl-p-[123I]-iodoamphetamine (123I-IMP), alternative body scans were carried out in 15 cases of cerebrovascular disease. The biodistribution of 99mTc-ECD was 5.5 +/- 0.7%, 3.8 +/- 0.7% in the brain; 13.1 +/- 3.7%, 2.2 +/- 1.2%, in the lung at 15 min and at 4 hours, respectively, whereas that of 123I-IMP was 3.9 +/- 1.4%, 5.0 +/- 1.0% in the brain; 32.2 +/- 7.6%, 12.7 +/- 3.3%, in the lung at 15 min and at 4 hours, respectively. 99mTc-ECD accumulated in comparatively high amounts in the brain but remained low in the lung in the early image compared to 123I-IMP. However there was a high inverse correlation between brain and lung uptake of 123I-IMP (r = -0.82), but not of 99mTc-ECD (r = -0.18). We concluded that 99mTc-ECD had a better biodistribution in terms of low lung accumulation than 123I-IMP in brain SPECT.

Aged↗