Digital cardiac imaging--the death knell of cineangiography?

Abstract

Digital X-ray imaging techniques have achieved wide-spread acclaim in general vascular diagnosis and in the support of interventional procedures. However, in cardiac angiography, acceptability of digital imaging until recently, has been less enthusiastic. To a large extent this has reflected the effectiveness of cine fluorography and the exacting performance standards that it sets to any competing technique. Whereas cine fluorography provides rapid acquisition of dynamic sequences of high (spatio-temporal) fidelty images, the review of these images has to be retrospective and in practice it is necessary to rely heavily on the modest image quality provided by TV fluoroscopy for the on-line evaluation of the procedure. Early attempts at digital cardiac imaging based upon digital subtraction angiography (DSA) produced results of widely inconsistent quality. This was partly because of the inferior specification of the equipment used at that time. In addition, however, the dynamic nature of the heart itself sets limits to the precision with which subtractive imaging could be performed. Nonsubtractive, or grey-scale, digital imaging on the other hand promised several practical advantages over DSA for cardiac studies, provided that the quality of the images could be enhanced using digital imaging techniques (Rouse et al, 1986). The recent introduction of extremely fast but economical analogue to digital converters and microprocessors now means that the contest between digital and cine fluorography in cardiac imaging can begin in earnest. Viable digital imaging systems which are custom designed for cardiac applications are now available.