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M Akisada

Publications and source records attributed to M Akisada.

At least 73 records · Page 4Linked to original sources
PubMed1986

Synchrotron radiation at the Photon Factory for non-invasive coronary angiography: experimental studies.

Synchrotron radiation available at the Photon Factory, National Laboratory for High Energy Physics, provides a new X-ray source which is highly suitable for K-edge subtraction. This is due to its high intensity, its parallelism and its monochromaticity, available in a monochromator system. Experiments were performed using wiggler synchrotron radiation. Since the beam size is relatively-small for in-vivo imaging, a phantom coupled with a detector was moved horizontally using a scanning table. K-edge subtraction was successfully applied both to the coronary artery phantom filled with barium sulphate, and to rat angiography using iodine contrast material. The potential use and value of energy subtraction was successfully demonstrated.

Animals↗
PubMed1986

Clinical validity of washout time constant images obtained by digital subtraction angiography.

Functional images of left ventricular myocardial perfusion were obtained using the washout time constant obtained from the analysis of digital subtraction angiograms (DSA). The results were compared with those of left ventriculography to evaluate its clinical validity. DSA examinations were performed in eight patients with old anterior myocardial infarction and in 10 control subjects. Washout time constant images of the left ventricular wall were nearly homogeneous in normal cases. On the contrary, regional heterogeneity on the washout time constant images was observed in cases of anterior infarction. The abnormal region in the washout time constant image corresponded well to the area of abnormal percent wall thickening, whereas the extent of the abnormal wall motion area tended to be broader than that of the abnormal washout time constant area or area of abnormal percent wall thickening. Thus, the washout time constant images obtained by DSA may comprise a reliable means of estimating the extent of ischemia in the myocardium.

Aged↗
PubMed1986

Digital subtraction angiography: image-sequence analysis for regional myocardial perfusion dynamics.

Digital subtraction angiography with selective coronary injections of contrast media has enabled us to obtain clear images, not only of the artery, but of the capillary and venous phases of the myocardial perfusion. In the present study, densitometry was used to estimate regional myocardial perfusion dynamics in 10 control cases and 11 anterior myocardial infarction cases. The time density curve showed that contrast material increased rapidly in the arterial phase and appeared to be washed out monoexponentially in the venous phase. The time from the onset of contrast medium injection to the maximal density of the contrast medium (Tp), and the time constant obtained from the washout curve (Tc) were analyzed. In the control group, Tp in the apical region was slightly prolonged as compared with Tp in the anterobasal region, but the difference was not significant (5.2 +/- 0.5 vs 4.2 +/- 0.4 sec: mean +/- SEM). Tc did not definitely change in any portion of the myocardium (anterobasal 5.1 +/- 0.5, anterior 4.8 +/- 0.5, apex 4.6 +/- 0.5 sec, respectively). In anterior myocardial infarction, Tp in the marginal region was significantly prolonged compared to Tp in the control region (6.0 +/- 0.3 vs 4.7 +/- 0.3 sec, p less than 0.01). Tp was prolonged for more than 10 sec in the infarcted region. Tc in the marginal region was markedly prolonged compared to Tc in the control region (7.4 +/- 0.9 vs 4.4 +/- 0.5 sec, p less than 0.025). Tc could not be determined in the infarcted regions because data acquisition time of our apparatus was inadequate.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Angiography↗
PubMed1985

A giant tumor thrombus in the right atrium clearly detected by 111In-oxine labeled platelet scintigraphy.

A 54-year-old man was admitted to hospital with a 3-month history of progressive dyspnea with coughing. A giant right atrial mass, originating from a hepatocellular carcinoma, was visualized by computed tomography, and digital subtraction angiography. The volume of the right atrial mass was increasing rapidly. It was therefore essential to determine whether this giant mass was a tumor thrombus or a multiplication of the hepatocellular carcinoma. 111In-oxine labeled platelet scintigraphy revealed active accumulation in the right atrium caused by the presence of active platelet deposition, and slight accumulation in the lung fields probably due to embolic showers originating from the tumor thrombus in the right atrium. This is the first case report showing that 111In-oxine labeled platelet scintigraphy can aid in confirming the nature of a giant tumor thrombus in the right atrium and can clarify the pathogenesis of the respiratory symptoms.

Blood Platelets↗
PubMed1985

Significance of ST-segment and T wave changes in the resting electrocardiograms of patients with exertional angina, studied by exercise radionuclide angiocardiograms.

In order to investigate the clinical significance of ST-T changes in resting ECG in angina pectoris, symptom-limited ergometer exercise radionuclide angiocardiography with ECG was performed in 60 patients with exertional angina. In those with normal ECG at rest (Group N), left ventricular ejection fraction (EF) did not change during exercise (71 +/- 5% to 71 +/- 6%). In those with only ST change at rest (Group ST) and those with only T change at rest (Group T), EF decreased significantly during exercise (68 +/- 5% to 63 +/- 7%, p less than 0.01; 68 +/- 6% to 61 +/- 7%, p less than 0.001). In those with ST and T changes at rest (Group ST + T), EF was low at rest (58 +/- 11%) and decreased further at exercise (52 +/- 8%, p less than 0.001). In those whose negative or flat T wave became more negative during exercise, EF was low both at rest and at exercise. In conclusion, ST and T changes at rest in patients with exertional angina might suggest a depressed reserve of myocardial function for exercise.

Adult↗
PubMed1985

Relationship between serum free thyroxine, total thyroxine and thyroxine-binding globulin concentrations in patients with Graves' disease.

Statistical analysis of relationship between free thyroxine (FT4) and thyroxine (T4) in patients with Graves' disease has revealed that serum FT4 values correlated well with serum T4 values at variable thyroid states before and during treatment with anti-thyroid drugs. However, the ratio of FT4 concentration to T4 concentration at hyperthyroid state was more than twice as large as the ratio at euthyroid and hypothyroid states. These findings are considered to denote the elevation of per cent of FT4 to T4 (% FT4) in thyrotoxicosis. Nevertheless, thyroxine-binding globulin (TBG) concentrations in hyperthyroid patients were slightly, but significantly lower by 7.3% than those in normal euthyroid volunteers. These results indicate the minimal contribution of the slight decrease in TBG concentrations to the marked elevation of %FT4 in patients with thyrotoxicosis.

Adolescent↗
PubMed1985

[Quantitative analysis of myocardial perfusion by digital subtraction angiography].

Digital subtraction angiography (DSA) has been adopted to detect ischemic myocardial areas and to quantitatively evaluate the degrees of myocardial perfusion abnormalities. Subtraction for selective coronary arteriography was performed sequentially between mask and enhanced images in the same cardiac phases by means of ECG signals. We obtained three distinct perfusion phases which we termed the arterial, capillary, and venous phases. Densitometry of the circumferential cardiac wall was performed on these sequential images. The results were compared with 201Tl myocardial scintigrams and cine angiograms. In the arterial phase, the abnormalities of the coronary artery, such as stenosis, obstruction and collaterals were represented. In the capillary phase, contrast materials served as markers of myocardial perfusion and delineated infarctions as areas of low contrast enhancement compared to the normally perfused myocardium. In the venous phase, the infarcted areas were represented as areas with greater relative contrast enhancement than that of the normal myocardium. Circumferential analysis of perfusion could provide more detailed information about myocardial ischemic areas and the degrees of ischemia. Although we used invasive selective coronary arteriography, DSA techniques have numerous merits such as excellent temporal resolution, spatial resolution, and good contrast resolution, over conventional methods. Quantitative DSA methodology which we developed provided not only anatomical information about the main coronary arteries but new information about abnormalities of peripheral myocardial perfusion.

Angiography↗
PubMed1985

[Regional myocardial perfusion abnormality detected by digital subtraction angiography in a case of patent ductus arteriosus with coronary arterial fistulae].

A 19-year-old woman with patent ductus arteriosus and increasingly severe chest pain received various examinations including exercise stress radionuclide test, which revealed hypokinesis and decreased myocardial perfusion in the apex and left ventricular dilatation. Conventional selective coronary arteriography and newly-developed ECG synchronized digital subtraction angiography (DSA) were performed to identify the genesis of her myocardial ischemia. Selective coronary arteriography revealed congenital coronary arterial fistulae in the right and left coronary arteries. The largest fistula was observed around the obtuse marginal artery terminating in the left ventricle. Although stenosis of the left circumflex and left anterior descending arteries (LAD) were not observed, the LAD appeared to be hypoplastic. Hypoplasia of the LAD and the steal phenomenon by arterial fistula could have been responsible for the myocardial ischemia in the apex, but this method did not clearly reveal the area and the degree of myocardial ischemia in the apex. Sequentially subtracted images during the arterial and capillary phases were obtained by utilizing ECG-synchronized DSA for selective coronary arteriography. For these images, densitometric analysis was adapted to the myocardial region, i.e. circumferential densitometry using 21 segments around the left ventricular wall. Decreased myocardial perfusion was clearly demonstrated in the apex in capillary phase images. Moreover, circumferential analysis provided detailed information about the area and the degree of impaired peripheral circulation in the myocardium. This analysis by DSA may prove useful for evaluating myocardial perfusion abnormalities.

Adult↗
PubMed1985

[Recent advances in mammographic diagnosis with respect to its technical aspects].

Technological advance has made remarkable improvements in image quality in the field of X-ray mammography which ensure to successful management of breast cancer in Japan. We convince simple mammographic technique is the state of arts in early detection of the curable breast cancer, however, attempts for further progress with respect to technology and its medical applications should be performed. Our fundamental and clinical works on this theme were presented here.

Breast Neoplasms↗
PubMed1984

Peripheral arterial disease diagnosed with high-count-rate radionuclide arteriography.

Thirty-seven patients with peripheral vascular disease involving the legs were studied with first-pass peripheral radionuclide arteriography (RNA) and contrast arteriography to determine whether RNA could be used to evaluate perfusion of the toes. Data were acquired for 100 seconds using a multicrystal gamma camera following bolus injection of 30-35 mCi (1,110-1,295 MBq) of Tc-99m-labeled albumin during reactive hyperemia. Peripheral time-activity curves were examined and the time required for activity to decline to 75% of peak activity ( T75 ) was recorded. When an abnormal RNA was defined as T75 greater than or equal to 50 seconds, sensitivity was 92%, positive predictive accuracy 100%, and negative predictive accuracy 75%. These data suggest that peripheral RNA of the toes is a reliable, noninvasive procedure for evaluation of peripheral arterial disease; it can be valuable as a screening test prior to contrast arteriography as well as for follow-up.

Adult↗
PubMed1984

Whole-body distribution of 11C-(4)-L-aspartic acid in rats.

Enzymatic synthesis of 11C-(4)-L-aspartic acid was undertaken using commercially available wheat germ phosphoenolpyruvate carboxylase. Whole-body distribution of the radioactive compound in rats showed higher accumulation in the salivary gland, glandular stomach and the pancreas, as well as in the lungs. Within 60 minutes after intravenous injection of 11C-(4)-L-aspartic acid, about 60% is removed as 11CO2 by expiration, indicating that the carbon atom at the fourth position of the radioactive compound is easily subjected to decarboxylation.

Animals↗
PubMed1984

Functional significance of coronary collateral vessels during exercise evaluated by radionuclide angiocardiography: the importance of supplying arteries.

To investigate the function of coronary collateral vessels, especially from view point of supplying arteries, radionuclide angiocardiography was performed before and during a symptom-limited ergometer exercise in 54 patients with effort angina. In single vessel disease, during exercise, left ventricular ejection fraction (EF) (%) increased in the cases with coronary collateral vessels (supplied from patent arteries) (72 +/- 7----77 +/- 8, p less than 0.025), but decreased in those without (66 +/- 10----61 +/- 10, P less than 0.001). In multivessel disease, EF decreased during exercise even in those with collaterals (supplied from stenosed arteries) (67 +/- 10----59 +/- 8, p less than 0.001). It is concluded that angiographic appearance of the coronary arteries supplying collateral vessels is a major predictive factor of the function of coronary collateral vessels and of left ventricle during exercise.

Adult↗