Biomedical subjects

Hideo Tsujii

Publications and source records attributed to Hideo Tsujii.

4 recordsLinked to original sources

PubMed2006

Development of a method for reconstructing three-dimensional data from axial, sagittal, and coronal MR images.

Magnetic resonance (MR) imaging is useful for the diagnosis of brain atrophy and intracranial abnormalities. We have developed a method of automated volumetry to evaluate the degree of brain atrophy for the diagnosis of dementia. Whole-brain MR images with thin slices without gaps are required for segmentation and volumetry. However, obtaining such images requires that the patient remain at rest for a prolonged period, thereby reducing the throughput of MR imaging examinations. Therefore, a method is needed for the reconstruction of isotropic three-dimensional (3D) data using routine axial, sagittal, and coronal MR images with 30% gaps and measurement of brain volume. The method of reconstructing 3D data consists of four processes: 1) segmentation of the brain region on axial, sagittal, and coronal MR images using the region-growing technique; 2) setting data to a 3D domain; 3) registration by manual operation; and 4) interpolation between the data based on linear interpolation. In clinical MR images, the differences between this method and the conventional technique were less than 10%. These results demonstrate that this technique is able to construct 3D data from axial, sagittal, and coronal MR images.

Adult↗

PubMed2005

Evaluation of variations in absorbed dose and image noise according to patient forms in X-ray computed tomography.

Excessive radiation exposure in pediatric computed tomography (CT) scanning has become a serious problem, and it is difficult to select scan parameters for the scanning of small patients such as children. We investigated differences in absorbed dose and standard deviation (SD) in Hounsfield unit (HU) caused by differences in the form of the subject using a body-type phantom with removable body parts. Using four X-ray CT scanners, measurements were made with values from 50 mAs to 300 mAs, with slices of 50 mAs, using scan protocols that were assumed to perform thorough examinations. The results showed that the mAs values and absorbed doses were almost proportional, and the absorbed doses in the phantom without body parts were about 1.1-2.2-fold higher than those of the phantom with body parts at the same points. The SD values obtained indicated that the absorbed doses in the phantom with body parts were 0.3-0.6 times those of the phantom without body parts when the mAs values used were adjusted so that both SD values were the same. The absorbed doses in various patient forms can be estimated from these results, and they will become critical data for the selection of appropriate scan protocols.

Dose-Response Relationship, Radiation↗

PubMed2005

[Evaluation and comparison of dose profiles and patient doses among X-ray CT scanners].

The increased clinical use of multi-detector-row CT (MDCT) may result in increased radiation doses for patients. The objective of this study was to compare radiation dose profiles between MDCT with 16 data acquisition systems, MDCT with 4 data acquisition systems, and single-detector-row CT (SDCT), and to compare effective doses among them to measure specific organ doses. When comparing radiation dose profiles on the Z-axis, doses outside the scanning range increased, especially when a 20 mm X-ray beam width was used. Effective doses also were higher with MDCT (low helical pitch) than with SDCT (helical pitch 1.0:1), but were not higher with MDCT (high helical pitch) than with SDCT (helical pitch 1.0:1). When a 20 mm X-ray beam width or high helical pitch was used, scanning time was shortened, but doses outside the scanning range were increased. When the standard deviation (SD) is the same, there is not much difference between SDCT and MDCT in terms of effective doses if the helical pitch is 1.0:1. It can be expected that X-ray over-wrap under low helical pitch and incorrect parameter setting cause increased radiation dose to the patient. Therefore, high helical pitch should be used if it is possible to disregard the influence of image noise. It is important to be cautious in regard to patient radiation dose when MDCT is used, and it is necessary to perform high-quality examinations at as low a dose as possible. Optimization of the scan parameters is an important issue for the future.

Organ Specificity↗

PubMed2005

[Visualization of the lower cranial nerves by 3D-FIESTA].

MR cisternography has been introduced for use in neuroradiology. This method is capable of visualizing tiny structures such as blood vessels and cranial nerves in the cerebrospinal fluid (CSF) space because of its superior contrast resolution. The cranial nerves and small vessels are shown as structures of low intensity surrounded by marked hyperintensity of the CSF. In the present study, we evaluated visualization of the lower cranial nerves (glossopharyngeal, vagus, and accessory) by the three-dimensional fast imaging employing steady-state acquisition (3D-FIESTA) sequence and multiplanar reformation (MPR) technique. The subjects were 8 men and 3 women, ranging in age from 21 to 76 years (average, 54 years). We examined the visualization of a total of 66 nerves in 11 subjects by 3D-FIESTA. The results were classified into four categories ranging from good visualization to non-visualization. In all cases, all glossopharyngeal and vagus nerves were identified to some extent, while accessory nerves were visualized either partially or entirely in only 16 cases. The total visualization rate was about 91%. In conclusion, 3D-FIESTA may be a useful method for visualization of the lower cranial nerves.

Accessory Nerve↗