Study of the Ability to Visualize Blood Vessels Using Virtual Monochromatic Images / 日本農村医学会雑誌

The purpose of this study was to investigate the effects of energy of virtual monochromatic images (VMIs) and the strength of iterative reconstruction on computed tomography (CT) number, image noise, and visual evaluation. Low keV VMIs improve the CT number of the contrast agent but also increases image noise, making them difficult to use. However, the adoption of iterative reconstruction has made low keV VMIs possible to use. We scanned a phantom containing dilute contrast agent with single energy (SE) and dual energy (DE) scanned images, comparing CT number, image noise (SD), and the contrast-to-noise ratio (CNR). The CT number and SD of 40 keV VMIs were 2.8 and 2.4 times higher, respectively, than those of 120-kV CT images. VMIs showed an inferior CNR compared with SE images due to increased image noise. The higher the strength of iterative reconstruction, the higher the visual evaluation score. Visual evaluation scores were highest at 50 keV. Low-keV VMIs are greatly affected by increased image noise. But by taking into the effects of parameters such as tube voltage and strength of iterative reconstruction, low keV VMIs can improve the visualization of blood vessels and reduce the use of contrast agent.

Fundamental Study of Reduced Radiation Exposure of Virtual Endoscopy by 16 DAS MDCT / 日本農村医学会雑誌

Our aim was to study the scan protocol of 16 DAS (Data Acquisition System) multidetector-row CT (MDCT) and to ascertain whether we could reduce radiation exposure and scanning time, while maintaing image quality in the Virtual endoscopy (VE).We made a mimic gastrointestinal tract and examined the result by changing a scan protocol of 16 DAS MDCT.We found that a reduction of radiation exposure and scanning time depended on slice width, angle of the table, rotation time, table speed, mAs/slice and resolution.The study confirmed that it was possible to use the scan protocol of MDCT with a radiographic dose of 40% and scanning time of 50%, without changing image quality in the VE.

Retrospective Studies of Serum Pepsinogen Levels in Stomach Cancer Cases Detected by Health Screening Project in the Past 5 Years / 日本農村医学会雑誌

In addition to barium swallow, the health screening center of our hospital has started meansuring serum pepsinogen (PG) levels in the stomach cancer screening tests since 1998 if patients wish to receive the PG test. During the past five years, 94 gastric cancer cases were detected by both methods. The average detection ratio worked out at 79.8% for the barium method and 71.3% for the PG method. Of the 94 cases, 51.1% tested positive by both methods. The positivity ratio was 28.7% for the barium method alone and 20.2% for the pepsinogen method alone. In other words, it follows that nearly half of the cancer cases have been picked out by either of the two techniques. Therefore, it could be said that the two methods serve as complementary one to the other. Thus, it was confirmed that using the PG method together with the barium method is worthwhile.The hitting ratio of positive reaction was high in patients at level 2 and upward when checked according to PG levels, and in patients whose initial test results were negative and later shifted to level 2 or level 4 with the lapse of time. These findings suggest that it is feasible to presupposed a group of people at higher risk for developing gastric cancer.