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Biomedical subjects

Yoshihisa Muramatsu

Publications and source records attributed to Yoshihisa Muramatsu.

5 recordsLinked to original sources
PubMed2006

Simulator-assisted setting of scan protocols for X-ray CT: development and clinical usefulness of the Scan Plan Simulator.

To assist in the selection of complicated computed tomography (CT) scan protocols and to obtain stable image SD values, prototype "Scan Plan Simulator" software with the following functions was developed and evaluated. 1) The image SD value that will be obtained in actual scanning is estimated by entering the patient's body size and scan protocol, after which a simulated image is displayed so that the estimated image SD value can be checked. The exposure dose can also be estimated in the Scan Plan Simulator. 2) The appropriate tube current is automatically set by entering the required image SD value. We evaluated the accuracy of the Scan Plan Simulator by comparing the simulation results with the image SD values and exposure dose obtained in actual scanning and assessed the usefulness of this method using Monte Carlo simulation based on body thickness data obtained in clinical examinations. The results showed that the Scan Plan Simulator not only stabilizes image SD by minimizing the effects of body size but also permits the exposure dose to be reduced by optimizing tube current.

Body Constitution↗
PubMed2005

[Screening for lung cancer by low-dose computed tomography].

The primary screening method for lung cancer in Japan is the chest x-ray, although it is not the accepted international standard because its accuracy is lower than that of procedures used to detect other types of cancer. Since the incidence and mortality rate of lung cancer are higher than in many other cancers, more effective screening modalities need to be developed. Lung cancer screening was improved about ten years ago through the introduction of computed tomography (CT) scanning techniques. CT provides a higher level of accuracy in detecting early lung cancers and there have been reports of improvement in the five-year survival rate, although its effect on decreasing the mortality rate has not been demonstrated as yet. There are two significant disadvantages, however, associated with using CT for the detection of lung cancer. First, CT scanning results in a considerably higher level of radiation exposure than chest x-ray. Secondly, CT scanning is so sensitive that it can reveal shadows unrelated to lung cancer, resulting in additional, but unnecessary CT scans being performed for further examination. Accordingly, this report reviews the basic points that should be considered when conducting CT scanning for lung cancer screening purposes.

Cost-Benefit Analysis↗
PubMedDate not supplied

The development and use of a chest phantom for optimizing scanning techniques on a variety of low-dose helical computed tomography devices.

PURPOSE: To develop a chest phantom for determining the optimal scan conditions for chest computed tomography (CT) screening. METHODS: The basic structure of the phantom is an arms-elevated-positioned anthropomorphic chest phantom. The internal structure includes simulated tumors (which are assumed to be the target lesions of chest CT screening examinations) placed at the levels of the lung apex, the bifurcation of the trachea, and the lung base of both simulated lungs. The image contrast of the simulated tumors is taken as the difference in CT value and is specified as 1 of 2 target values: Delta270 and Delta100. An opening for placement of a dosimeter is provided on the central axis of the phantom. Initial field tests were conducted focusing on the scan conditions for chest CT screening. RESULTS: Images similar to those obtained in chest CT screening examinations and clearly showing pathologic changes were obtained. The dose measurement at the center was 2.0 mGy. The diameters of the simulated tumors that could be detected were 6 mm for Delta270 and 10 mm for Delta100. CONCLUSION: The use of this phantom makes it possible to determine the optimal scan conditions for chest CT screening based on objective evaluation criteria.

Adult↗
PubMedDate not supplied

Computer-simulation technique for low dose computed tomographic screening.

OBJECTIVES: The purpose of this study is to assess the relative influence of noise and artifact in detecting lung nodules on low dose computed tomographic (CT) screening. METHODS: We develop the computer-simulation technique that allows tube current simulation and virtual nodule insertion in any CT images. The tube current simulation uses a reduction model that adds random Gaussian noise distribution to existing projection data. The virtual nodules are generated using a dedicated CT simulation tool with same scanner geometry. RESULTS: The coefficient of the correlations between the contrast-to-noise ratio of the actual scan and simulated tube current images was 0.98. There was no difference in CT number between virtual nodules and actual nodules [t test results = 0.60, t50(0.01) = 2.70 at 10 mA] and the coefficient of the correlations of the image noise was 0.99. CONCLUSIONS: Our technique is useful for systematic evaluation of radiation dose reduction and structure visibility in low-dose CT screening.

Computer Simulation↗