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Biomedical subjects

I Kanno

Publications and source records attributed to I Kanno.

At least 55 records · Page 3Linked to original sources
PubMed1996

New display methods of combined topographic EEG and cerebral blood flow images in the evaluation of cerebral ischemia.

To evaluate complicated changes in the EEG and cerebral blood flow (CBF) in cerebral infarction, EEG was recorded under various blood pressure levels, during CBF measurement with positron emission tomography, in patients with chronic cerebral infarction. Newly developed display methods which combine topographic EEG and its significance probability mapping with CBF, clearly provided objective measures of changes in EEG parameters and CBF, during induced hypo- and hypertension.

Aged↗
PubMed1996

Carotid artery resection for head and neck cancer.

BACKGROUND: Carotid artery resection has been shown to yield a chance of cure in patients with advanced head and neck carcinoma involving the carotid artery. However, the criteria for the identification of those who are vulnerable to neurologic injury after resection have not been established. Interposition grafting may minimize the risk of neurologic morbidity, although it is technically difficult when there is involvement of the internal carotid artery close to the skull base. METHODS: We studied 24 patients with head and neck tumor involvement of the carotid artery. We performed carotid artery resection in 16 of them, including 10 in whom the carotid artery was reconstructed with interposition grafts covered with muscle flaps. When it was thought that the reconstruction would be difficult, positron emission tomography was performed during balloon test occlusion of the internal carotid artery to assess the adequacy of hemispheric collateral blood flow before carotid resection. In one patient with interposition graft, carotid rupture occurred as a result of wound infection, but none of the other patients experienced perioperative death, persistent hemiplegia, or delayed stroke. RESULTS: Twelve patients have survived longer than 8 months, and seven (43.8%) were alive without disease at 12 months after resection, whereas all four patients who could not be treated operatively died within 8 months as a result of local primary tumors. CONCLUSIONS: Carotid artery resection is the only therapy offering any potential for cure or palliation. Positron emission tomography is a rapid quantitative means of determining the cerebral blood flow, particularly when resection is planned without reconstruction.

Aged↗
PubMed1996

Minimum cross-entropy reconstruction of PET images using prior anatomical information.

An algorithm is presented for the reconstruction of PET images using prior anatomical information derived from MR images of the same subject. The cross-entropy or Kullback-Leiber distance is a measure of dissimilarity between two images. We propose to reconstruct PET images by minimizing a weighted sum of two cross-entropy terms. The first is the cross-entropy between the measured emission data and the forward projection of the current estimate of the PET image. Minimizing this term alone is equivalent to the ML-EM reconstruction. The second term is the cross-entropy between the current estimate of the PET image and a prior image model which incorporates anatomical information derived from registered MR images. A weighting parameter determines the relative emphasis given to the emission data and the prior model in the reconstruction. Details of this algorithm are presented as well as test reconstructions for real and simulated data. The performance of the algorithm was evaluated with respect to errors in prior anatomical information. The algorithm provided significant improvement in the quality of reconstructed images as compared with the ML-EM reconstruction technique. The reconstructed images had higher resolution as compared with the images obtained from MAP-like reconstructions which do not utilize anatomical information. The algorithm displayed robustness with respect to errors in prior anatomical information.

Algorithms↗
PubMed1996

Automated interstudy image registration technique for SPECT and PET.

UNLABELLED: We report the extended application of an automated computer technique for three-dimensional spatial registration of SPECT and PET studies. METHODS: The technique iteratively reslices a misaligned data set until the sum of the absolute differences (SAD) from a reference data set is minimized. The registration accuracy was assessed in Hoffman brain phantom studies collected with known misalignments and transmission studies of a thorax phantom with fiducial markers. The SAD was compared with three other cost functions: stochastic sign change criterion, sum of products and standard deviation (s.d.) of ratios. In clinical neurological and myocardial perfusion studies, registration accuracy was estimated from the relative locations of landmarks in the reference and registered data sets. RESULTS: Registration accuracy in the Hoffman brain phantom studies was -0.07 +/- 0.46 mm (mean +/- s.d.) for translations and -0.01 +/- 0.20 degrees for rotations, with maximum translation and rotation errors of 1.2 mm and 0.8 degree, respectively. The SAD was the most accurate and reliable cost function. Registration errors in the thorax phantom were 3.1 +/- 1.7 mm. Mean accuracy in the neurological studies, estimated from landmark pairs, was 2.0 +/- 1.1 mm for SPECT to SPECT and 1.8 +/- 1.1 mm for PET to SPECT registrations. Average registration accuracy in 201Tl myocardial perfusion studies was 2.1 +/- 1.2 mm. CONCLUSION: Our registration method (a) provided accurate registrations for phantom and clinical SPECT and PET studies, (b) is fully automated, (c) simplifies comparison of data sets obtained at different times and with different modalities, and (d) can be applied retrospectively.

Algorithms↗
PubMed1996

[A case of AIDS with bronchial tuberculosis].

A case is 48 years-old Japanese man who had a history of frequent sexual contact with prostitutes in Thailand and the Philippines. He presented with chief complaint of chest discomfort in April 1995. His chest X-ray film showed right mediastinal lymph node swelling in other hospital and the sputum smear was strongly positive for acid fast bacilli. In May 1995, he was admitted to our hospital and serological tests for HIV were positive both by EIA and Western blot methods. The CD4 lymphocyte count was 167/microliters. He was diagnosed as a case of AIDS according to the criteria proposed by the AIDS surveillance committee of the Japanese Ministry of Health and Welfare. Although numerous tubercule bacilli were detected in sputum, the chest X-ray did not show abnormal shadow in lung fields. So the diagnosis of bronchial tuberculosis was suspected by these apparently contradictory findings and the bronchoscopy was performed. Biopsy specimen of the bronchial mucous membrane obtained by bronchoscopy confirmed the presence of acid fast bacilli by Ziehl-Neelsen's staining method, however, histological findings were atypical of tuberculosis. A month after the initiation of treatment with isoniazid, rifampicin and ethambutol and AZT, his clinical symptoms improved and the sputum smear and the culture tests for tubercule bacilli converted to negative. Complications of AIDS, (Pneumocystis carinii infection, Cytomegalo virus infection, Kaposi's sarcoma, etc) other than tuberculosis have not developed to date. In the past reports, we could not find reports of bronchial tuberculosis with AIDS. Tuberculous granuloma formation was scarce in this case, and it was suspected that bronchial tuberculosis with AIDS would show characteristic sign as same as pulmonary tuberculosis with AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1996

[Observation of relation between object size or length and count rate for 3D PET].

We obtained the concentration range of better S/N in 3D than 2D acquisition by measuring count rate for phantoms of different size and length. We used noise equivalent count rate (NECR) for evaluation of S/N of images. For 20 cm diameter 15 cm length cylindrical phantom, NECR of 2D was higher than that of 3D more than 1.2 microCi/ml. For 30 cm diameter 15 cm length cylindrical phantom, NECR of 2D was higher than that of 3D more than 0.7 microCi/ml. For 14 cm diameter 25 cm length cylindrical phantom, NECR of 3D was lower than that of 25 cm length phantom. With these results, though 3D is useful when administered dose is small, image quality of 2D becomes better than 3D more than a certain concentration. For the larger diameter or longer object, the advantage of 3D is diminished at lower concentration.

Body Constitution↗
PubMed1996

[Development of a front shield for a 3D positron emission tomograph].

Accidental coincidence rate and scatter coincidence rate of 3-dimensional (3D) acquisition of positron emission tomograph (PET) are higher than 2-dimensional (2D) acquisition and count loss becomes higher because slice shield collimator is not used in 3D acquisition. If one could decrease the gamma ray from outside of the axial field of view (FOV), it may be possible to improve image quality of 3D acquisition. Thus, using a Shimadzu SET-2300W (Headtome V) PET camera, we developed and tested a front shield for brain study to shut off gamma ray from the outside of the axial FOV. Using the front shield, gamma ray from outside of the FOV and the accidental coincidence rate could be decreased. The count loss in high count rate was also decreased. With these effect, the image quality of the clinical studies in 3D acquisition could be increased.

Brain↗
PubMed1996

Regional cerebral blood flow response in gray matter heterotopia during finger tapping: an activation study with positron emission tomography.

We examined regional cerebral blood flow response in a patient with gray matter heterotopia located beneath the sensorimotor cortex during a finger tapping task. We found regional cerebral blood flow was specifically increased during contralateral finger tapping. This indicated the possibility of functional differentiation of the ectopic neurons despite incomplete migration.

Adult↗
PubMed1996

Clinical positron emission tomography for brain tumors: comparison of fludeoxyglucose F 18 and L-methyl-11C-methionine.

PURPOSE: To evaluate the differences between fludeoxyglucose F 18 (FDG) and L-methyl-11C-methionine (11C-methionine) as tracers for positron emission tomography (PET) in the evaluation of brain tumors. METHODS: We analyzed 10 patients with histologically verified cerebral glioma or meningioma and 1 patient with a neuroradiologic diagnosis of low-grade glioma by using FDG, 11C-methionine, and PET. We qualitatively and quantitatively evaluated the extent and degree of accumulation of FDG and 11C-methionine in the tumor tissue. RESULTS: Although PET with FDG depicted malignant tumors as a hot spot in all cases, it was not able to delineate the extent of the tumor. Conversely, PET with 11C-methionine outlined the tumors as areas of increased accumulation of 11C-methionine, regardless of the degree of malignancy. CONCLUSION: PET with FDG and with 11C-methionine can play complementary roles in the evaluation of brain tumors.

Blood Glucose↗
PubMed1995

Regional cerebral blood flow, blood volume, oxygen extraction fraction, and oxygen utilization rate in normal volunteers measured by the autoradiographic technique and the single breath inhalation method.

By means of a high resolution PET scanner, the regional cerebral blood flow (rCBF), cerebral blood volume (rCBV), oxygen extraction fraction (rOEF), and metabolic rate of oxygen (rCMRO2) for major cerebral gyri and deep brain structures were studied in eleven normal volunteers during an eye-covered and ear-unplugged resting condition. Regional CBF was measured by the autoradiographic method after intravenous administration of H2(15)O. Regional OEF and rCMRO2 were measured by the single inhalation of 15O2. With MR T1-weighted images as an anatomical reference, thirteen major cerebral gyri, caudate nucleus, lentiform nucleus, thalamus, midbrain, pons, cerebellum and vermis were defined on the CMRO2 images. Values were read by using circular regions of interest 16 mm in diameter. The posterior part of the cingulate gyri had the highest rCBF and rCMRO2 values among brain structures, followed by the lentiform nucleus, the cerebellum, the caudate nucleus, and the thalamus. Parahippocampal gyri had the lowest rCBF and rCMRO2 values among the cortical gyri. Regional OEF for the pontine nuclei (0.34 +/- 0.04), the midbrain (0.35 +/- 0.05), the parahippocampal gyri (0.35 +/- 0.04 for the right and 0.37 +/- 0.05 for the left), and the thalami (0.37 +/- 0.05 for the right and 0.36 +/- 0.04 for the left) were significantly lower than the mean OEF for the cerebral cortices (0.42 +/- 0.04) (p < 0.05 or less). The global CBF and CMRO2 were consistent with those obtained by the Kety-Schmidt method.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Photic stimulation study of changing the arterial partial pressure level of carbon dioxide.

To investigate the effect of the level of baseline cerebral blood flow (CBF) on local CBF augmentation by activation, we have used positron emission tomography to measure regional CBF (rCBF) in 12 normal volunteers with and without photic stimulation during hypocapnia, normocapnia, and hypercapnia. The increase in rCBF in the primary visual cortex by photic stimulation was 10.8 +/- 3.1, 18.6 +/- 9.3, and 19.5 +/- 6.1 ml 100 ml-1 min-1 in hypo-, normo-, and hypercapnia, respectively. The increase was significantly smaller in hypocapnia than in normocapnia (p < 0.005). The fractional CBF increase caused by the photic stimulation was the same in all breathing conditions. This result indicates that the magnitude of the CBF increase induced by neuronal activity correlates proportionally with the level of baseline CBF.

Adult↗
PubMed1995

Commentary and opinion: I. Principal component analysis, variance partitioning, and "functional connectivity".

We briefly review the need for careful study of "variance partitioning" and "optimal model selection" in functional positron emission tomography (PET) data analysis, emphasizing the use of principal component analysis (PCA) and the importance of data analytic techniques that allow for heterogeneous spatial covariance structures. Using an [15O]water dataset, we demonstrate that--even after data processing--the intrasubject signal component of primary interest in baseline activation studies constitutes a very small fraction of the intersubject variance. This small intrasubject variance component is subtly but significantly changed by using analysis of covariance instead of scaled subprofile model processing before applying PCA. Finally, we argue that the concept of "functional connectivity" should be interpreted very generally until the relative roles of inter- and intrasubject variability in both disease and normal PET datasets are better understood.

Analysis of Variance↗
PubMed1995

A comparative study of three fast algorithms to estimate cerebral blood flow and distribution volume using N-isopropyl-p-[123I]iodoamphetamine and two SPECT scans.

To estimate regional cerebral blood flow (rCBF) and distribution volume (Vd) using N-isopropyl-p-[123]iodoamphetamine (IMP) and two SPECT data (early and delayed data) measured at two discrete time points, three fast algorithms are implemented, which are the table look-up method (TLU), the linear least-squares fitting method (LLSF), and the linear search method (LS). A two-compartment model was used as the IMP kinetic model. These algorithms were applied to the early and delayed data measured by the two scan protocols, t1 = 12 min, t2 = 54 min (scan A) and t1 = 12 min, t2 = 85 min (scan B). The estimated rCBF and Vd values using the present three algorithms were in good agreement with those using the nonlinear least-squares fitting technique and dynamic SPECT data. The quantitative value and signal to noise (S/N) ratio of rCBF images by TLU was not changed whether scan A or scan B was used. However, the S/N of the Vd image by TLU using scan B improved over that using scan A. The same tendency was observed in the results of LLSF and LS. The CPU times for the parametric imaging of CBF and Vd images for one slice (64 x 64 matrix) were 0.04, 0.09, and 0.14 s using TLU, LLSF, and LS, respectively. In conclusion, the present three algorithms gave reasonably accurate estimates of rCBF and Vd using two SPECT data, and are well suited for parametric imaging because of their good statistical properties and high computational efficiency.

Algorithms↗
PubMed1995

Acute subarachnoid hemorrhage: MR imaging with fluid-attenuated inversion recovery pulse sequences.

PURPOSE: To evaluate the usefulness of fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) imaging sequences in the detection of acute subarachnoid hemorrhage (SAH). MATERIALS AND METHODS: MR imaging with FLAIR sequences was performed with a 0.5-T superconducting unit in 20 patients (aged 30-72 years) with acute SAH due to a ruptured aneurysm and in 27 control subjects (aged 32-72 years). FLAIR images were obtained 2 hours to 2 days after ictus. Findings were evaluated and compared with computed tomographic (CT) findings. RESULTS: In all patients, acute SAH was clearly demonstrated as an area with signal intensity that was high relative to that of the normal cerebrospinal fluid and surrounding brain parenchyma at FLAIR imaging. This sequence was especially useful in demonstration of acute SAH in the posterior fossa, which was difficult to show at CT because of beam-hardening artifacts. In a double-blind comparison, no FLAIR images acquired in control subjects were confused with those acquired in control subjects were confused with those acquired in patients. CONCLUSION: FLAIR sequences reliably provide diagnostic images in patients with acute SAH.

Acute Disease↗
PubMed1995

Human cortical regions activated by wide-field visual motion: an H2(15)O PET study.

1. Several areas in the monkey dorsal visual pathway, including the dorsal part of the medial superior temporal area, have been found to contain cells responding to movements of a wide visual field and are suggested to be involved in analyzing self-induced motion information. In the present study, positron emission tomography was used to localize human cortical regions responding to wide-field visual motion. Changes in regional cerebral blood flow (rCBF) were measured when subjects maintained fixation and viewed low-contrast (0.15 log units brighter than the background) dots subtending 80 x 80 degrees and moving either coherently or incoherently. Brain foci were localized after activity in a fixation-only paradigm was subtracted from that in the two moving dot paradigms. 2. Both the coherent and incoherent movements significantly activated the primary/secondary visual cortex and surrounding visual areas in the cuneus and superior occipital gyrus. Subtraction of images between the coherent and incoherent movements showed that the activity caused by the two types of movement was comparable in these early visual cortical regions. 3. In the lateral occipitotemporoparietal cortex, the coherent movement specifically activated two separate areas; a posterior focus was located at the border of the right occipitotemporal gyri, and a dorsoanterior focus was located bilaterally in the temporoparietal cortex. The incoherent movement did not activate these regions. 4. A fine anatomic localization using individual magnetic resonance images was performed for the bilateral activation in the temporoparietal cortex, which was found to be located mainly in the depth of the inferior parietal lobule and a small portion of the superior and middle temporal gyri. 5. Both the coherent and incoherent movements activated a part of the superior parietal lobule located within the intraparietal sulcus (Brodmann area 7). The bilateral foci activated by the coherent movement were located more anteriorly than the focus activated by the incoherent movement. Subtraction images between the coherent and incoherent movements, however, did not reveal any significant rCBF increases in the superior parietal lobule. 6. Several other cortical regions known to be involved in visuospatial and visuomotor functions were also activated by the coherent movement, including the frontal eye field (Brodmann area 8) and premotor cortex (Brodmann area 6) in the frontal lobe. 7. The posteriorly located activation at the border of occipito-temporal gyri corresponds to the homologue of the middle temporal area reported in previous activation studies using small to medium-sized motion stimuli. The bilateral activation in the inferior parietal lobule appeared to rely on wide-field motion stimulation.

Adult↗
PubMed1995

Central benzodiazepine receptor distribution after subcortical hemorrhage evaluated by means of [123I]iomazenil and SPECT.

BACKGROUND AND PURPOSE: [123I]Iomazenil is a single-photon emission computed tomography (SPECT) tracer that selectively binds to central benzodiazepine receptor in the neuron membrane. With this ligand, we studied the central benzodiazepine receptor distribution in the cortex remote from subcortical hematoma in intracerebral hemorrhage patients. METHODS: Four patients with unilateral putaminal hemorrhage and one patient with right thalamic hemorrhage were studied (mean +/- 1 SD age, 50.0 +/- 8.8 years). The initial volume of hematoma ranged from 4.3 to 31.0 mL (mean +/- 1 SD, 17.5 +/- 12.3 mL). SPECT images obtained 3 hours after intravenous administration of [123I]iomazenil (167 MBq/750 ng) were analyzed. In three patients, perfusion was evaluated with [123I]IMP. On SPECT images, the radioactivity ratio of the ipsilateral to the contralateral cerebral cortex (I/C ratio) or of the contralateral to the ipsilateral cerebellar hemisphere (C/I ratio) was measured. RESULTS: The I/C ratio for iomazenil was significantly decreased compared with unity in the temporal lobe (0.84 +/- 0.08, P < .01) and the parietal lobe (0.87 +/- 0.10, P < .05), but the C/I ratio in the cerebellum (1.00 +/- 0.03) was not. The C/I ratio for perfusion in the cerebellar cortex (0.83 +/- 0.04, P < .01) was significantly decreased compared with that in normal subjects. CONCLUSIONS: Central benzodiazepine receptor-[123I]iomazenil binding was decreased in the ipsilateral cerebral cortex remote from the subcortical hematoma. This preliminary result may facilitate further study of the potential damage of the cortical neurons remote from subcortical hematoma.

Cerebral Cortex↗