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Yasuo Saito

Publications and source records attributed to Yasuo Saito.

10 recordsLinked to original sources
PubMed2006

Investigation of retrospective respiratory gating techniques for acquisition of thin-slice 4D-Multidetector-computed Tomorgraphy (MDCT) of the lung: Feasibility study in a large animal model.

Respiratory gated 3D-MDCT acquisition of the whole chest over time (4D-MDCT) allow retrospective reconstruction of raw data at any point of the respiratory cycle might be beneficial in severely ill or sedated patients. Aim of this feasibility study was to investigate 2 prototype devices as input for retrospective respiratory gating in order to calculate lung volumes (LVs) and mean lung densities (MLDs) over time. Sixteen-row MDCT data were acquired in 5 ventilated pigs using a laser sensor and charge-coupled devine (CCD) camera and retrospectively reconstructed at every 10% of the respiratory cycle. Semiautomatic segmentation of the 3D data sets was performed, and LV and MLD were calculated. Data acquisition was successful in all cases. The mean difference of LV between maximum inspiration and expiration was 246 and 240 mL (laser and CCD, respectively). The mean difference of MLD between inspiration and expiration was 70 (laser) and 67 (CCD) HU. The lowest MLD was found at the beginning of the respiratory cycle (0%) for laser, and at 90% for CCD. Both gating devices allowed for reliable 4D-MDCT image acquisition. No differences were found for calculated LV and MLD, whereas the respiratory cycle was more precisely detected using the laser based gating device.

Animals↗
PubMed2006

Free-breathing three-dimensional computed tomography of the lung using prospective respiratory gating: charge-coupled device camera and laser sensor device in an animal experiment.

PURPOSE: The aim was to investigate the feasibility and image quality of prospective respiratory gating for 3-D computed tomography (CT) of the lung. MATERIAL AND METHODS: Eight anesthetized pigs underwent prospectively gated multidetector computed tomography using 2 devices: a charge-coupled device (CCD) camera and a laser sensor. The output signal of both gating devices was connected to the scanner instead of ECG unit. Inspiratory and expiratory images were obtained during "free-breathing" and analyzed in MPR mode for sharpness of bronchi, diaphragm and lung using a 4-point-score (1, excellent to 4, severe artifacts). RESULTS: The CCD camera worked in all animals. Using the laser sensor, only 50% of expiratory scans could be acquired. All acquired images showed excellent sharpness (CCD camera vs. laser sensor) for trachea (1.1 +/- 0.3 vs. 1.3 +/- 0.5), bronchi (1.4 +/- 0.7 vs. 1.8 +/- 0.6), lung fissures (1.0 vs. 1.1 +/- 0.3), and lung parenchyma (1.0 +/- 0.2 vs. 1.4 +/- 0.6), and minor to major artifacts for diaphragm (1.5 +/- 0.8 vs. 2.0 +/- 1.0, P < 0.05) and pericardial lung structures (1.9 +/- 0.7 vs. 2.3 +/- 0.5). CONCLUSION: High image quality for inspiratory and expiratory scans was achieved by free-breathing 3-D CT of the lung using noncontact prospective respiratory gating.

Animals↗
PubMed2005

Prototype heel effect compensation filter for cone-beam CT.

The prototype cone-beam CT (CBCT) has a larger beam width than the conventional multi-detector row CT (MDCT). This causes a non-uniform angular distribution of the x-ray beam intensity known as the heel effect. Scan conditions for CBCT tube current are adjusted on the anode side to obtain an acceptable clinical image quality. However, as the dose is greater on the cathode side than on the anode side, the signal-to-noise ratio on the cathode side is excessively high, resulting in an unnecessary dose amount. To compensate for the heel effect, we developed a heel effect compensation (HEC) filter. The HEC filter rendered the dose distribution uniform and reduced the dose by an average of 25% for free air and by 20% for CTDI phantoms compared to doses with the conventional filter. In addition, its effect in rendering the effective energy uniform resulted in an improvement in image quality. This new HEC filter may be useful in cone-beam CT studies.

Equipment Design↗
PubMed2004

Monitoring the cell number and viability of Lactobacillus helveticus GCL1001 in human feces by PCR methods.

Real-time polymerase chain reaction (PCR) and nested reverse transcription (RT) PCR were applied to demonstrate the viability of lactobacilli in the feces of volunteers fed fermented milk containing lactobacilli. Two sets of specific primers and a TaqMan probe for real-time PCR were constructed using the S-layer gene as a target. After fermented milk ingestion, Lactobacillus helveticus GCL1001 was detected in the feces of 12 volunteers over a few days, with the maximum number being between 10(4.5) and 10(7.8) cells g(-1) of feces. Moreover, mRNA from this strain was detected in the feces of all volunteers by nested RT-PCR. The results show that these methods are applicable to the demonstration of bacterial viability in feces, and that ingested L. helveticus GCL1001 can survive through the gastrointestinal tract.

Colony Count, Microbial↗
PubMed2004

Physical performance evaluation of a 256-slice CT-scanner for four-dimensional imaging.

We have developed a prototype 256-slice CT-scanner for four-dimensional (4D) imaging that employs continuous rotations of a cone-beam. Since a cone-beam scan along a circular orbit does not collect a complete set of data to make an exact reconstruction of a volume [three-dimensional (3D) image], it might cause disadvantages or artifacts. To examine effects of the cone-beam data collection on image quality, we have evaluated physical performance of the prototype 256-slice CT-scanner with 0.5 mm slices and compared it to that of a 16-slice CT-scanner with 0.75 mm slices. As a result, we found that image noise, uniformity, and high contrast detectability were independent of z coordinate. A Feldkamp artifact was observed in distortion measurements. Full width at half maximum (FWHM) of slice sensitivity profiles (SSP) increased with z coordinate though it seemed to be caused by other reasons than incompleteness of data. With regard to low contrast detectability, smaller objects were detected more clearly at the midplane (z = 0 mm) than at z = 40 mm, though circular-band like artifacts affected detection. The comparison between the 16-slice and the 256-slice scanners showed better performance for the 16-slice scanner regarding the SSP, low contrast detectability, and distortion. The inferiorities of the 256-slice scanner in other than distortion measurement (Feldkamp artifact) seemed to be partly caused by the prototype nature of the scanner and should be improved in the future scanner. The image noise, uniformity, and high contrast detectability were almost identical for both CTs. The 256-slice scanner was superior to the 16-slice scanner regarding the PSF, though it was caused by the smaller transverse beam width of the 256-slice scanner. In order to compare both scanners comprehensively in terms of exposure dose, noise, slice thickness, and transverse spatial resolution, K=Dsigma2ha3 was calculated, where D was exposure dose (CT dose index), sigma was magnitude of noise, h was slice thickness (FWHM of SSP), and a was transverse spatial resolution (FWHM of PSF). The results showed that the K value was 25% larger for the 16-slice scanner, and that the 256-slice scanner was 1.25 times more effective than the 16-slice scanner at the midplane. The superiority in K value for the 256-slice scanner might be partly caused by decrease of wasted exposure with a wide-angle cone-beam scan. In spite of the several problems of the 256-slice scanner, it took a volume data approximately 1.0 mm (transverse) x 1.3 mm (longitudinal) resolution for a wide field of view (approximately 100 mm long) along the zeta axis in a 1 s scan if resolution was defined by the FWHM of the PSF or the SSP, which should be very useful to take dynamic 3D (4D) images of moving organs.

Biophysical Phenomena↗
PubMed2004

The cause of the artifact in 4-slice helical computed tomography.

The causes of the image artifacts in a 4-slice helical computed tomography have been discussed as follows: (1) changeover in pairs of data used in z interpolation, (2) sampling interval in z, and (3) the cone angle. This study analyzes the first two causes of the artifact and describes how the current algorithm [K. Taguchi and H. Aradate, Radiology 205P, 390 (1997); 205P, 618 (1997); Med. Phys. 25, 550-561 (1998); H. Hu, ibid. 26, 5-18 (1999); S. Schaller et al., IEEE Trans. Med. Imaging 19, 822-834 (2000); K. Taguchi, Ph.D. thesis, University of Tsukuba, 2002] solves the problem. An interpolated sinogram for a slice at the edge of a ball phantom shows discontinuity caused by the changeover. If we extend the streak artifact in the reconstructed image, it crosses the focus orbit at the corresponding projection angle. Applying z filtering can reduce such causes by its feathering effect and mixing data obtained by different cone angles; the best results are provided when z filtering is applied to densely sampled helical data.

Algorithms↗
PubMed2004

[Effects of radiation therapy for paraaortic lymph node involvement and recurrent lymph node metastases from gastric cancer].

Effects of radiation therapy for lymph node metastases from gastric cancer were retrospectively analyzed. The radiation sites were residual paraaortic lymph node involvement and postoperative recurrent lymph node metastases in 10 patients. The size of lymph node swelling was decreased in 6 (60%) patients after radiation therapy using liniac. Complaints due to lymph node metastases such as pain and edema of extremities were voiced by 7 patients. These complaints were eventually relieved or disappeared in all 7 patients. There were no severe adverse effects during radiation therapy, and 7 patients (70%) could shift to home care. One-year and 3-year survival rates were 20 and 10%, respectively. Radiation therapy for lymph node metastases from gastric cancer was chiefly effective in relieving complaints. Although it is unclear whether radiation therapy can improve the survival rate, these results suggest that radiation therapy could be one of the most useful locoregional therapies for paraaortic lymph node involvement and recurrent lymph node metastases from gastric cancer.

Aged↗
PubMed2002

Stability of species composition of fecal bifidobacteria in human subjects during fermented milk administration.

Bifidobacteria play important roles in human health. However, the influence of exogenous factors on species composition of fecal bifidobacteria is still unclear. The objective of this study was to investigate the effects of fermented milk administration on the species composition of fecal bifidobacteria by molecular biological methods. Fermented milk containing Lactobacillus helveticus was given to seven healthy subjects, and the probiotic effect on human fecal microflora was demonstrated as a significant increase of bifidobacteria and decrease of clostridia by the conventional culture method. Species composition of bifidobacteria in the human fecal microflora was then investigated directly in fecal specimens by the PCR detection method. The species composition of bifidobacteria in the fecal specimens did not change significantly throughout the study period. These findings suggest that the species composition of bifidobacteria remains stable even when fecal microflora is improved by food management.

Adult↗
PubMedDate not supplied

Four-dimensional computed tomography (4D CT)--concepts and preliminary development.

Four-dimensional computed tomography (4D CT) is a dynamic volume imaging system of moving organs with an image quality comparable to that of conventional CT. 4D CT will be realized by several technical breakthroughs for dynamic cone-beam CT: (1) a large-area two-dimensional (2D) detector; (2) high-speed data transfer system; (3) reconstruction algorithms; (4) ultra-high-speed reconstruction computer; and (5) high-speed, continuously rotating gantry. Among these, development of the 2D detector is one of the main tasks because it should have as wide a dynamic range and as high a data acquisition speed (view rate) as present CT detectors. We are now developing a 4D CT scanner together with the key components. It will take one volume image in 0.5 sec with a 3D matrix of 512 x 512 x 512. This paper describes the concepts and designs of the 4D CT system, as well as preliminary development of the 2D detector.

Equipment Design↗