[Evaluation of the Image Registration Program for Portal Images Using CR and DRR Images in Radiation Therapy].

In this study, computer simulations and experiments were used to verify the accuracy of a two-dimensional image registration program (program) for portal images that we previously developed. The program used a computed radiography cassette system and digitally reconstructed radiography images as planning images for external beam radiation therapy. Using this program, we also investigated the reason two-dimensional automatic image registration images experienced large misregistration in clinical practice using commercial image registration systems.

[Failure analysis of medical linear accelerator with reliability analyses].

We analyzed a number of cases about the Linac troubles in our hospital and have examined the effect of preventive maintenance with Weibull analysis and exponential distribution from April 2001 to March 2012. The total failure by irradiation disabled was 1, 192. (1) Medical linear accelerator (MLC) system was 24.

[Effect of changing into slippers on the pollution situation in the nuclear medicine management district].

Changing into slippers when entering the nuclear medicine management district prevented pollution expansion. Accidents involving patients falling occurred in university facilities. It was thought that changing slippers was the cause.

[Improvement of method of determining fluoroscopy loading factor in digital angiographic x-ray system with a flat panel detector].

A catheterization study and treatment of coronary arteriopathy are performed by investigating the coronary artery from different angles to find the region to be treated. In doing so, our system always started from the initial value of the loading factor, using this only for the first time, and the system started from the last loading factor the second time and later, at all angles. Therefore, depending on the angle, the loading factor at the start of fluoroscopy sometimes became unstable, and it took time to stabilize.

[CT scanners with automatic focus alteration capability].

Heat accumulation in X-ray tubes results in disarrangement of focus owing to heat expansion of the anode. CT scanners with automatic focus alteration capability have been developed to counteract this problem. We compared CT scanners with and without focus alteration capabilities and discuss the effect of focus disarrangement on the CT images.