[Development of automatic verification system for portal image in radiotherapy].

The current method of verification for external beam radiation therapy visually compares a simulation image with a portal image. However, because this method depends largely upon the observer's experience, it sometimes results in inter-observer differences. In this study, we developed software to measure atomatically the quantitative difference between the simulation image and portal image using an image-analysis method.

Effect of scattered radiation on image noise in cone beam CT.

Cone beam CT has a capability for the 3-dimensional imaging of large volumes with isotropic resolution, and has a potentiality for 4-dimensional imaging (dynamic volume imaging), because cone beam CT acquires data of a large volume with one rotation of an x-ray tube-detector pair. However, one of the potential drawbacks of cone beam CT is a larger amount of scattered x-rays, which may enhance the noise in reconstructed images, and thus affect the low-contrast detectablity. Our aim in this work was to estimate the scatter fractions and effects of scatter on image noise, and to seek methods of improving image quality in cone beam CT.

Relation between radiographic mottle for double and single emulsions.

The radiographic density fluctuations produced by using dual screen-film systems are designated as the radiographic mottle. The density fluctuation of the radiographic mottle for the double emulsions at a density of the double emulsions consists of those for the front and back emulsions on a radiograph. However, the relation between the Wiener spectra of the radiographic mottle for the double and single emulsions had not been studied.

Computer-aided diagnosis: development of automated schemes for quantitative analysis of radiographic images.

Preliminary results obtained with computer-aided diagnosis (CAD) from various radiographic examinations are very encouraging. However, CAD is still at an early stage of its development. It will be necessary to increase further the understanding of image features of normal and abnormal patterns, to establish databases, and to devise specific approaches for particular types of pathology.

Effect of heart-size parameters computed from digital chest radiographs on detection of cardiomegaly. Potential usefulness for computer-aided diagnosis.

Heart size is an important and useful diagnostic parameter in chest radiographs. However, there is a large variation in the subjective judgment of cardiac enlargement (cardiomegaly). To reduce this subjective element, the authors are developing an automated system for quantitative analysis of heart size in digital chest radiographs.