Search PubMed⌕ Search

Biomedical subjects

Y Tateno

Publications and source records attributed to Y Tateno.

At least 91 records · Page 5Linked to original sources
PubMed1990

Carbon-13 NMR imaging study of in-vivo glucose metabolism.

Carbon-13 NMR spectroscopy and chemical shift selective imaging studies of in vivo glucose metabolism were performed at 2.0 T. Some metabolite peaks were observed in 13C NMR spectra, and carbon NMR imaging focused in the spectral region attributed to D-1-13C-glucose were also performed. A 13C NMR signal accumulated in the liver was detected and the average time resolution of these spectra and images were 10 and 30 minutes, respectively.

Animals↗
PubMed1990

[Measurement of myocardial blood flow using N-13 ammonia dynamic PET-theory and methodology].

Positron emission tomography (PET) offers the potential capability of noninvasive measurement of regional myocardial blood flow (RMBF) in man. Because N-13 ammonia exhibits properties which to some extent resemble those of the radioactive microsphere, we developed a first-pass flow method for noninvasive measurement of RMBF. In the present method, RMBF was determined by dividing myocardial activity at time T by arterial input integrated from the injection start to that time, where time T is the endpoint of first circulation of N-13 ammonia. Also in the present method a time-activity curve of left atrium was used as the arterial input function to make the procedure totally noninvasive. To validate the present method, we compared it with the compartment analysis. 5 patients with hypertrophic cardiomyopathy (HCM) and with a considerably thickened ventricular wall, were selected for the comparison between the first-pass flow method and the compartment analysis. The relationship of RMBFs by the two methods was y = 1.8 + 1.097x-0.002037x2 (n = 30, SEE = 5.5), where x (ml/min/100 g) was obtained by the compartment analysis, while y (ml/min/100 g) by the first-pass flow method. The result indicated that both were almost identical in physiological flow range (less than 100 ml/min/100 g), but that the first-pass flow method underestimated RMBF in the higher flow range due to venous leakage of N-13 ammonia. As the conclusion, we could at least measure RMBF of HCM patient in the physiological flow range by the present method. The future extension of the method was discussed.

Ammonia↗
PubMed1989

[Risk-benefit analysis for mass screening of breast cancer utilizing mammography as a screening test].

Incidence of breast cancers in Japanese women is increasing steadily. Mass screening of breast cancer was started in Japan under auspices of Adult Health Promotion Act of the Japanese Government from 1987. As the first screening method, the palpation of breasts is employed at present, but it is expected to be replaced by the mammography. In this report, the risk-benefit analysis is presented between risk of breast carcinogenesis due to radiation and benefit of mass screening of breast cancer. The benefit of mass screening is taken as the net elongation of average life expectancy of women due to survival from breast cancers. The risk of mammography is taken as the net loss of average life expectancy of women due to breast carcinogenesis. In the latter, the latency time and plateau period of radiation carcinogenesis were taken into consideration in the calculation. The results show that the ages at which the benefit and risk become equal are between 30 and 35 years old when dose equivalent of mammography is between 10 and 20 mSv, that are conventionally used. However, the critical age will be reduced to 20 years old if the dose equivalent becomes 1 mSv. Therefore, it is strongly recommended that a low dose mammographic system should be developed in order to achieve 1 mSv for the mass screening of breast cancer of Japanese women. In author's opinion, this is quite feasible by employing a new digital radiography with imaging plate.

Adolescent↗
PubMed1989

[On the assessment of the diagnostic accuracy of imaging diagnosis by ROC and BVC analyses--in reference to X-ray CT and ultrasound examination of liver disease].

To achieve an effective assessment of diagnostic accuracies of currently used imaging methods on liver diseases, X-ray CT (CT) and realtime ultrasound (US), ROC analysis and a new analysis method, "the bias to variance characteristics (BVC)" were applied in parallel. The survey has been carried out to assess an image interpretation accuracy on cases with established diagnosis collected on the multi-institutional basis. The images, CT and US of liver diseases including localized and diffuse lesions were selected for image reading sessions and the interpretative difficulties were geared to an appropriate grade so that it does fit to the basic requirement of ROC analysis. Consequently, 91 cases were selected from a total of 258 cases which were collected from 16 institutions. Two image reading sessions were scheduled and a total of 28 radiologists and sonologists undertook the first session. The final analysis covered 8 radiologists for CT and 9 sonologists who carried out both sessions. The image interpretation results were fed to the computer and analyses were made accordingly. Analysis of the first image reading session gave true positive ratios (TPR) of CT and US as 92.5% and 97.4%, and true negative ratios (TNR) of 50.5% and 46.8%, respectively. The second reading session, in which both CT and US images were interpreted simultaneously, gave the similar values of TPRs, 96-97% and TNRs, 44-47%. The ROC analysis of existence of liver mass and diagnosis of malignancy resulted in the higher values in US compared to CT in the first separate reading, however, the 2nd session gave almost identical values in each modality. The diagnostic accuracy for the benign tumors, mostly consisted of hemangioma, CT reading gave higher accuracy rates compared to the US. The entirely new interpretations scheme, arbitrarily named as BVC was carried ou on matrix data obtained in the same experiment. The scatterograms plotted according to the BV values, the mean and the standard deviation inherent to individual cases have demonstrated marked variations among individual cases most likely reflecting the interpretative difficulty of respective images, thus indicating the method to be well in adjunct to the ROC analysis.

Adult↗
PubMed1989

Duchenne muscular dystrophy carriers. Proton spin-lattice relaxation times of skeletal muscles on magnetic resonance imaging.

By means of magnetic resonance imaging (MRI), the proton spin-lattice relaxation times (T1 values) of the skeletal muscles were measured in Duchenne muscular dystrophy (DMD) carriers and normal controls. The bound water fraction (BWF) was calculated form the T1 values obtained, according to the fast proton diffusion model. In the DMD carriers, T1 values of the gluteus maximus and quadriceps femoris muscles were significantly higher, and BWFs of these muscles were significantly lower, than in normal control. Degenerative muscular changes accompanied by interstitial edema were presumed responsible for this abnormality. No correlation was observed between the muscle T1 and serum creatine kinase values. The present study showed that MRI could be a useful method for studying the dynamic state of water in both normal and pathological skeletal muscles. Its possible utility for DMD carrier detection was discussed briefly.

Adult↗
PubMed1989

Detection of benzodiazepine receptor occupancy in the human brain by positron emission tomography.

Benzodiazepine receptor occupancy in the brain following oral administration of clonazepam (CZP) with a dose of 30 micrograms/kg in six healthy young men and a further dose of 50 micrograms/kg in one of the subjects was estimated by carbon-11 labeled Ro15-1788 and positron emission tomography (PET). The effects of CZP on the latency of auditory event-related potentials (P300) were also studied. Overall brain 11C uptake was depressed and the % inhibition of 11C uptake in the gray matter of the brain at 30 min after [11C]Ro15-1788 injection was 15.3-23.5% (mean, n = 6) following 30 micrograms/kg CZP when compared with that in the control experiment without any previous treatment. The 11C uptake in the cerebral cortex in the subject who received both doses decreased in a dose-related manner after 30 micrograms/kg and 50 micrograms/kg CZP. The P300 latency was prolonged significantly by 30 micrograms/kg CZP [31.6 +/- 16.3 ms (mean +/- SD, n = 6), P less than 0.05]. The P300 latency in the same subject was prolonged in a dose-related manner by 30 micrograms/kg and 50 micrograms/kg CZP. The technique using [11C]Ro15-1788 and PET permits comparison of the pharmacological effects with the percentage of receptor sites which benzodiazepines occupy in the human brain. P300 also seems to be useful to investigate the pharmacological effects of benzodiazepines.

Adult↗
PubMed1989

On the maximum likelihood method for estimating molecular trees: uniqueness of the likelihood point.

Studies are carried out on the uniqueness of the stationary point on the likelihood function for estimating molecular phylogenetic trees, yielding proof that there exists at most one stationary point, i.e., the maximum point, in the parameter range for the one parameter model of nucleotide substitution. The proof is simple yet applicable to any type of tree topology with an arbitrary number of operational taxonomic units (OTUs). The proof ensures that any valid approximation algorithm be able to reach the unique maximum point under the conditions mentioned above. An algorithm developed incorporating Newton's approximation method is then compared with the conventional one by means of computer simulation. The results show that the newly developed algorithm always requires less CPU time than the conventional one, whereas both algorithms lead to identical molecular phylogenetic trees in accordance with the proof.

Algorithms↗
PubMed1989

Computer system and software of POSITOLOGICA II: a whole body positron emission tomograph.

Since a whole body PET-scanner POSITOLOGICA II was installed at the National Institute of Radiological Sciences (NIRS) in 1982, improvements of the computer system and developments of new software have been continuously made to correspond to clinical requirements. As the result, POSITOLOGICA II possesses one of the most powerful systems and sophisticated software in Japan. This report describes the present status of the computer system and software of POSITOLOGICA II. It also discusses problems which still exist and proposes a future computer system for the PET study.

Brain↗
PubMed1988

Proton spin-lattice relaxation time of Duchenne dystrophy skeletal muscle by magnetic resonance imaging.

By means of proton MRI, the spin-lattice relaxation times (T1 values) of pelvic and leg muscles were measured in Duchenne muscular dystrophy (DMD) patients and normal controls. The bound water fraction (BWF) was calculated from the T1 value obtained. In normal children, the T1 value decreased, and BWF increased with age. In DMD, the T1 value rapidly decreased, from an abnormally high value in the early stages, with the progress of the disease. This reduction of the T1 value in DMD was not the same for all muscles; it was most prominent in the gluteus maximus and least prominent in the sartorius and gracilis muscles. BWF was below normal in the early stages of DMD. It is suggested that both regenerating and degenerating muscle fibers, together with the increased muscle water content, cause the high T1 value and low BWF in the early stages of DMD, whereas replacement of muscle by fat causes the decreased T1 value in the advanced stages.

Child↗
PubMed1988

[Potential use of positron-emission tomography in clinical oncology].

Positron-emission tomography (PET) is an excellent technique, utilizing positron-labeled radiopharmaceuticals which provide a quantitative image of tissue metabolism in the living body. Cancer tissue is characterized by increased forms of metabolism, such as glycolysis and protein synthesis. Consequently, PET makes it possible to evaluate the metabolic activity of cancer tissue. Such information is useful not only for a better understanding of human cancer biology but for utilization in cancer clinics. The potential use of the PET technique for clinical oncology are cancer detection, cancer grading, biological characterization of tumors, and evaluation of therapeutic effectiveness. From this viewpoint, much clinical research has been done and good results obtained in both the characterization of hepatoma and lung cancer, and the grading of brain tumor, showing good correlation with prognosis after cancer therapy. However, PET is not commonly available and has not yet been established as a diagnostic technique in cancer clinics. Further extensive studies will thus be necessary in order to achieve these aspects.

Carbon Radioisotopes↗