Gifu University of Medical Science

About: Gifu University of Medical Science is a education organization based out in Gifu City, Japan. It is known for research contribution in the topics: Imaging phantom & Motion sickness. The organization has 89 authors who have published 202 publications receiving 1350 citations.

Influence of Acquisition Mode of Cone-beam Computed Tomography on Accuracy of Image Registration for Image-guided Radiotherapy.

Abstract: Half scan can acquire images at the 200° rotation in image-guided radiation treatment using cone-beam CT and is useful to evaluate the influence of the half-scan-imaging start angle and imaging direction on image registration accuracy. The half-scan-imaging start angle is changed from 180° to 340° in the clockwise direction and from 180° to 20° in the counter clockwise direction to calculate the registration error. As a result, registration errors between -0.37 mm and 0.27 mm in the left and right directions occur because of the difference in the imaging start angle and approximately 0.3° in the gantry rotation direction because of the difference in the imaging direction. Because half scan does not have data for 360° rotation, depending on the subject structure, inconsistency of opposing data can lower reconstruction accuracy and cause a verification error. In addition, in image acquisition during rotation, the slower the shutter speed is, the more the actual gantry angle and angle information of the image are apart, which is considered the cause of rotation errors. Although these errors are very minute, it is thought that there is no influence on the treatment effect, but these errors are considered an evaluation item indispensable for ensuring the accuracy of high-precision radiation treatment. In addition, these errors need to be considered for ensuring the quality of high-precision radiation treatment.

Image Evaluation Method for Digital Mammography with Soft-copy Reading Using a Digital Phantom

Abstract: Mammograms are evaluated on soft-copy films or hard copies. In Japan, soft-copy diagnoses shift rapidly, and the method for facilities applying it is necessary for soft-copy diagnosis. Digital mammography has high resolution and a large matrix size. On a monitor, the image is either displayed partially at 1:1 pixel mapping or narrowed to fit the screen, resulting in loss of image quality. Therefore, we developed a digital phantom for soft-copy diagnosis in digital mammography.We developed the digital phantoms used by every mammographicdetector sold in Japan. For our digital phantom, we used C to create signals, which we converted to DICOM using Osirix. This phantom is like the Contrast Detail Phantom and comprises 12 different shapes and eight different brightness levels. It becomes one group of nine, and each signal is located at the prime number coordinate from a central signal coordinate. Visual evaluation refers to the visibility of the nine signal coordinates when the image is adjusted to fit the monitor’s display. A digital phantom is useful not only for evaluating display systems that feature reducing functions and monitor resolution but also for educational purposes such as confirming the effects of the monitor’s resolution and reducing functions as well as for precision management with regard to deterioration and malfunction. Although digital phantoms have been implemented at 120 facilities, at two other facilities, viewer problems were detected.