Masayuki Tsuneoka

Digital TV tomography: Description and physical assessment

A digital TV tomography system, capable of retrospective reconstruction of multiple digital tomographic images, has been developed and its basic physical characteristics have been evaluated. The multiple tomographic images were formed through retrospective reconstruction of digital data acquired on a linear tomographic x-ray unit and an image intensifier-television system. Digital data were obtained with a series of 30 pulsed exposures during linear motion of the system. A distortion correction algorithm for the convex surface of the image intensifier was developed in order to reduce image distortion. A phantom study showed that the square-wave response at the fulcrum plane was slightly inferior to that in conventional tomography. There was also a slight decrease in the square-wave response away from the fulcrum plane and upon application of a correction algorithm, as compared with the response of the original reconstructed image at the fulcrum plane. The exposure dose for a single image was approximately half that in conventional tomography. Because of many advantages, including low exposure, short examination time, digital image manipulation, and applicability to picture archiving and communication systems, this is likely to become an important method in radiology when further technical refinements have been made.

Determination of left ventricular volumes with use of DSA density values

A computer program was developed to obtain left ventricular volumes from the density values of DSA. The highest density value along the horizontal pixel line over the left ventricle in 30 degrees RAO was considered to correspond to the greatest width on the same level of 60 degrees LAO. The left ventricular volume was obtained by converting the density values into the width and integrating these values. This method estimated experimental balloon volumes with considerable accuracy. Clinical evaluation revealed good correlation between DSA and conventional cine left ventriculography.

High Resolution Digital Subtraction System

We have developed a high resolution digital subtraction angiography (DSA) system which has a 1024 x 1024 pixel matrix incorporating a high resolution TV camera. The resolution of a DSA system is usually restricted by a TV camera so far. A diode-operating implegnated-cathode SATICON (DIS) imaging tube was selected and the TV camera was operated in slow scan mode with 1125 scan line numbers to improve the resolution of the TV camera. This system was free from degradation in resolution due to 512 X 512 pixel matrix. Diagnostic accuracy was improved by using the high resolution DSA system.