Among several techniques for contrast-enhanced MRA, the elliptical centric view ordering method, originally developed at the Mayo Clinic, is a promising one. It has been difficult to apply a fat-suppression prepulse, mainly because the conventional fat suppression method requires a longer acquisition time during sampling of the lowfrequency domain in k-space, and it causes severe image distortion due to the great change in longitudinal magnetization derived from fat tissue. We developed a novel method to append fat saturation to the elliptical centric view ordering technique, and assessed the feasibility of its use. Our method is to apply fat-saturation pulses only at selected sampling points when any gradient is applied in the slice-encoding direction. In this way, we achieved efficient suppression of fat-derived signal within a relatively short time, comparable to that of the conventional fat-saturation method, and succeeded in minimizing artifacts.
A new imaging plate (IP) with a transparent support and reading system that can detect emissions from both sides of the IP has been developed and has already been introduced in some facilities. In this study, low contrast threshold detectability was investigated experimentally for a CR system with a two-sided reading system (new CR) and for a conventional CR system. Images of a Contrast-Detail phantom were obtained with the new and conventional CR systems at dose levels corresponding to 26%, 49%, 82%, 103%, and 164% of the dose used for the screen-film system. Using an observer performance study of Contrast-Detail phantom images, the threshold contrast of disk-shaped objects ranging from 0.3 mm to 4.0 mm in diameter was determined. We also calculated image quality figure (IQF) from the results of observation. The new CR system showed significantly better contrast detectability than the conventional CR system. The use of a new CR system provided a reduction of approximately 25% in radiographic dose while providing comparable IQF.
To develop a method of kinetic radiography and a computer-aided diagnosis (CAD) system for quantitative evaluation of the temporomandibular joint (TMJ), dynamic images of the TMJ from one healthy volunteer were obtained by fluoroscopy in the lateral view on the right and left sides. The accumulated image subtraction technique extracted the condyle in each image. A sequential similarity detection algorithm (SSDA) was employed to trace the movement path and the velocity of the condyle. The shape of the path of the right condyle was smoother than that of the left condyle. The size of the maximum vertical and horizontal movements of the condyle were 4.6±0.1 mm and 15.0±0.2 mm, respectively. The velocity of the movement of the condyle was higher in the area close to the articular eminence than in any other area during the opening and closing of the mouth. This CAD system will contribute to the kinetic analysis of the TMJ for screening, follow-up study, and informed consent, providing speed, quantitation, and cost-effectiveness.
The INNOVA 2000, an all-digital cardiovascular X-ray system with flat panel detector, is equipped with a monitoring function that makes it possible to track a patient's absorbed dose by displaying the realtime presumed absorbed dose. We verified this dose monitoring system and evaluated how it is affected by various parameters. We also compared the INNOVA 2000 to a conventional machine, the Advantx LC. The average absorbed dose of the INNOVA 2000 was 1,066 mGy, while that of the Adnantx LC was calculated to be 2,028 mGy. Dose reduction with the INNOVA 2000 was 76% at Low mode and 52% even at Normal mode. The INNOVA provides an advantage in lowering absorbed dose, even considering that it has a rectangular image intensifier (I. I.) versus the Advantx LC's round I. I. This comparison was made by cine and digital angiography.