Biomedical subjects

Sadatoshi Kuwahara

Publications and source records attributed to Sadatoshi Kuwahara.

3 recordsLinked to original sources

PubMed2006

Accuracy of attenuation measurement of vascular wall in vitro on computed tomography angiography: Effect of wall thickness, density of contrast medium, and measurement point.

OBJECTIVES: We sought to assess the effects of measurement point, wall thickness, and intravascular density of contrast material on attenuation measurement of vascular wall. MATERIALS AND METHODS: We used vascular models (actual attenuation value of the wall: 83 HU) with wall thicknesses of 1.5, 1.0, or 0.5 mm, filled with contrast material of 254, 325, or 400 HU. The 9 vascular models were fixed in an oil-filled container and scanned with a 16-detector computed tomography. The wall attenuation values were measured at 1 point for 0.5-mm thickness models, 3 for 1.0-mm thickness models, and 5 for 1.5-mm thickness models with the same interval of 0.25 mm. Total 20 measurements were done for each point. RESULTS: For 1.0-mm and 1.5-mm thickness models, wall attenuation progressively increased as the measurement points approached the lumen (P < 0.0001). At all the measurement points for 0.5-mm and 1.0-mm thickness models and the 2 inner measurement points for 1.5-mm thickness models, the densities of contrast material affected the wall attenuations significantly (P < 0.0001). At the midportion for 1.5-mm thickness models, the wall attenuations were not affected by the densities of the contrast material (P = 0.6301), and were 65-68 HU. CONCLUSIONS: The effects of the intravascular density of contrast material, measurement point, and wall thickness should be considered in the attenuation measurement of the wall.

Angiography↗

PubMed2006

Accuracy and efficiency of left ventricular ejection fraction analysis, using multidetector row computed tomography: effect of image reconstruction window within cardiac phase, slice thickness, and interval of short-axis sections.

BACKGROUND: The aim of the present study was to assess the accuracy and efficiency of left ventricular ejection fraction (LVEF) analysis by multidetector row computed tomography (CT). METHODS AND RESULTS: The CT data of 21 patients were analyzed by semi-automated software on a workstation. In analysis of LVEF using systolic volumes in the 6 phases (30-55%), systolic images of 10% interval (35, 45, 55%) were underestimated with a mean measurement error of -0.4% and the standard error of the estimate (SEE) of 0.6%, compared with the LVEF using images of 5% interval. In analysis of LVEF using 3-slice thicknesses of axial images (1, 2, and 3 mm), and 3-slice numbers of short-axis sections (10 14, and 30 slices), there was no significant difference between the SEE of the intraobserver reproducibility and that of the analysis with 30 short-axis sections using axial images of 1-, 2- and 3-mm thickness, and that with 14 short-axis sections using axial images of 1- and 2-mm thickness. The mean analysis times were 96.9 s, 119.8 s, and 227.0 s for the analysis with 10, 14, and 30 short-axis sections, respectively. CONCLUSION: The proper selection of the reconstruction interval in the cardiac phase, the slice thickness of the axial images, and the number of short-axis sections reduces the analysis time, maintaining the accuracy of LVEF analysis. This will be acceptable for practical use at present, although more accurate analysis is preferable.

Adult↗

PubMed2005

Evaluation of coronary stents in vitro with CT angiography: effect of stent diameter, convolution kernel, and vessel orientation to the z-axis.

BACKGROUND: The aims of the present study were to assess the effect of the stent diameter, convolution kernel, and vessel orientation to the z-axis on the evaluation of coronary stents, in vitro with computed tomography (CT) angiography. METHODS AND RESULTS: Seven vascular models (2 models without stenosis, 2 with obstruction, and 3 with stenosis) with an approximate inner diameter of 3 or 4 mm, filled with contrast material (79 or 330 HU) were scanned with a 16-detector CT. The diameter measurement of the stent lumen and stenosis evaluation were both done in an orientation parallel to the z-axis of the scanner using 4 convolution kernels. The measured diameters of the stented lumen were 47-57% and 36-45% smaller than the actual inner diameter of the 3- and 4-mm diameter models, respectively. The diameter measurement of the stent lumen and visualization of the in-stent stenosis were improved by using convolution kernels with higher spatial resolution. The in-stent artifacts were evaluated in 4 orientations (0 degrees , 30 degrees , 60 degrees , 90 degrees ) to the z-axis. The artifact was the minimum in 0 degrees to the z-axis, and the maximum in 90 degrees . CONCLUSION: Visualization of the lumen of a stent by CT is affected by its diameter, convolution kernel, and vessel orientation to the z-axis, and these factors should be taken into consideration in the stent evaluation.

Angiography↗