X-ray image intensifiers: applications and current limitations

Early intensifiers having small fields of view and poor contrast were so difficult to use with normal patient tables that specialized use was the rule, and routine work unusual, though rewarding in patient dosage and detail rendition, when aerial images were used. Deposited amorphous screens suffered traumatic voids, severe halation and short lifetimes. Closed-circuit television presentation led to widespread acceptance of intensifiers for gastro-intestinal work and provided variable contrast for cardiac and renal examinations, but quantum and shot noise were suppressed by increased radiation dosage. Lag prevented close study of moving organs. Caesium iodide input screens provide physical stability, reduced halation, high contrast, improved definition, short lag, with increased quantum absorption efficiency at ‘diagnostic energies’. Reduced closed-circuit television gain and noise improve low contrast soft tissue differentiation, particularly with relative motion; lung metastases are detected before radiographs confirm, and small contrast-filled vessels are sharply defined for cineradiography. Current developments include compact intensifiers, whose field of view accepts cardiopulmonary images or includes the liver, spleen and both kidneys, or the kidneys and a considerable length of both ureters, for functional or vascular studies.