ABSTRACT
Initial attempts used for storing fluorographic images used video techniques. The video images from the camera tube were captured on a video disk which was then displayed without further irradiation of the patient. This gave great benefits regarding reduction of patient dose but had limitations regarding image quality, speed of display, and image storage. The development of digital fluorography allowed much faster image acquisition and storage and, more importantly, digital image manipulation. The patient dose reduction was significant. The machines used for digital fluorography commonly use C-arm geometry although under-and over-table designs now use digital acquisition. A digital imaging system offers the following advantages:
• Dose reduction • Wide dynamic range • Image storage • Instant imaging (filmless) • Dynamic imaging (up to 30 fps) • Image copying without loss of quality • Image data transfer (PACS)
The imaging chain of a modern digital fluorography (DF) system is shown in Fig. 13.1. The important
component parts are:
• The image intensifier • Input phosphor • Photocathode • Output phosphor • Coupling optics • The video camera: Plumbicon, CCD • The amplifier • The analog-to-digital converter • The signal conversion circuit and look-up table A large field of view (40 cm) image intensifier is commonly used for DSA so that both legs can be imaged during ‘bolus chasing’ or serial studies. Specifications for a typical image intensifier suitable for digital fluorography have been given in Table 10.4.
