Biomedical subjects

H Toyama

Publications and source records attributed to H Toyama.

256 records · Page 15Linked to original sources

PubMedDate not supplied

Improvement in Fourier analysis of gated blood-pool studies using single photon emission computed tomography: methodology and clinical feasibility.

We have developed a new method for obtaining reconstructed left ventricular (LV) planar images acquired from multidirectional views using gated blood-pool single photon emission computed tomography (SPECT), and have applied Fourier analysis to these planar images. In this paper, we describe the methodology of our new technique and discuss its feasibility for the detection of LV wall motion abnormalities (WMA) in patients with coronary artery disease (CAD). Sagittal long-axis, horizontal long-axis and short-axis sections of the LV were generated from the reconstructed transaxial tomograms. Sections covering only the LV at the same phase of the cardiac cycle were added to reconstruct planar images. Fourier analysis was then performed to construct phase and amplitude images. In 42 patients with significant WMA, a comparative study concerning the detection of WMA was performed between conventional and SPECT methods. The SPECT method had greater sensitivity in all segments of the LV, with no significant loss in specificity. In particular, the sensitivity of the SPECT method was significantly greater than that of the conventional method for inferior and posterior WMA (91% vs 57%; and 76% vs 35%, respectively). The method described here shows greater clinical effectiveness for the detection of LV WMA in patients with CAD.

Adult↗

PubMedDate not supplied

Sterilization of hepatitis B surface antigen-contaminated materials.

The sterilizing conditions of HBs Ag-contaminated materials were studied by means of the inactivation of the antigenicity (infectivity being thought to be lost when HBs Ag is inactivated). HBs Ag-coated beads and the serum from an HBs Ag-positive patient were used. After each sterilizing procedure, the antigenicity was studied by radioimmunoassay. HBs Ag-positive serum is easily inactivated by boiling and by steam under pressure; however, HBs Ag-coated beads require increased steam under pressure. For sterilizing HBs Ag-contaminated materials, 30 minutes at 132 degrees C is recommended.

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PubMedDate not supplied

The value of the modified high temporal resolution phase analysis for the detection of myocardial infarction.

Recently, cardiac nuclear medicine, especially gated RI cardiac blood pool scan has been improved remarkably, and now phase analysis has been introduced. We have developed a new modified phase image, with the objective of improving the time resolution, by displaying a special range of phase angles (about pi/3 radian) with 16 color scales, which correspond to the ventricles. Compared with the conventional method, the high resolution phase image improved the sensitivity of diagnosis of the region of myocardial infarction. The sensitivity of the modified phase image was 91% (10 cases our of 11), whereas that of the conventional method was 27% (3 cases out of 11).

Adult↗

PubMedDate not supplied

Functional imaging of thallium-201 myocardial washout and the clinical utility of this method.

In exercise testing with Thallium-201 myocardial scintiscan, we developed a quantitative myocardial Tl-201 washout image, a washout ratio and a washout index to detect ischemic segments. The washout value was measured with a pixel by pixel calculation between counts of the initial image and images that were delayed for three hours after the initial image. We compared the color displayed functional washout images with the original image in the detection of ischemic segments which had been confirmed by coronary angiography. A study of 22 patients showed 20 cases of coronary artery disease (with MI 8, but without MI 12) and two cases of normal control. The sensitivity for detection of a diseased vessel was 81% in the washout ratio imaging method and 79% in the washout index method, and both were superior to the sensitivity of the original image, which was 69%. As concerns MI cases, eight out of nine infarcted segments showed a lower washout, which represented partial redistribution on the delayed image. Six out of seven ischemic but not infarcted segments could be detected by the washout image, but only three were detected by the original image. These results indicate the washout image could provide not only transient ischemia but also additional ischemia of MI. We conclude that the washout image will be useful in producing a visual indication of ischemic areas.

Adult↗