Image quality assessment in contemporary interventional cardiology laboratories: spatial and low-contrast video resolution.

Two measures of fluoroscopic image quality-high-contrast video spatial resolution and low-contrast video resolution-were assessed in 64 interventional cardiology catheterization laboratories. The results of high-contrast spatial resolution testing indicate variable levels of performance with median values of 1.5, 2.0, and 2.5 line pairs/mm at the three levels of magnification. The results of the low-contrast video resolution testing indicate clinically relevant limitations in performance. This was particularly true when testing was performed in a dynamic mode under simulated large patient conditions. Under these conditions, 50% of systems failed to detect a wire of diameter 0.017". In addition, limited system dynamic range was identified in a substantial fraction of laboratories and may contribute to these important variations in performance. Taken together, these findings serve to characterize overall system performance in the current era of interventional cardiology and reaffirm the continued need for image quality assessment programs.

Variability of radiation output dynamic range in modern cardiac catheterization imaging systems.

Automatic exposure control (AEC) is one of the most important characteristics for optimizing cardiac catheterization imaging; this allows the X-ray system to provide sufficient radiation output under a variety of clinical conditions so that a satisfactory image is obtained. AEC was assessed in 97 cardiac catheterization laboratories using a standard set of phantoms. Three different copper attenuators were used to simulate three patient sizes. As magnification increased, many systems had limited dynamic range and were unable to increase radiation output. With increasing atttenuator thickness, the problem worsened. With the thickest attenuator and largest magnification (4.5"-5.0" FOV), 60% of systems could not achieve the typical 70% increase in exposure while 20% were unable to increase radiation output at all.

Causes of cine image quality deterioration in cardiac catheterization laboratories.

Deterioration of cineangiographic image quality can result from malfunctions or technical errors at a number of points along the cine imaging chain: generator and automatic brightness control, x-ray tube, x-ray beam geometry, image intensifier, optics, cine camera, cine film, film processing, and cine projector. Such malfunctions or errors can result in loss of image contrast, loss of spatial resolution, improper control of film optical density (brightness), or some combination thereof. While the electronic and photographic technology involved is complex, physicians who perform cardiac catheterization should be conversant with the problems and what can be done to solve them. Catheterization laboratory personnel have control over a number of factors that directly affect image quality, including radiation dose rate per cine frame, kilovoltage or pulse width (depending on type of automatic brightness control), cine run time, selection of small or large focal spot, proper object-intensifier distance and beam collimation, aperture of the cine camera lens, selection of cine film, processing temperature, processing immersion time, and selection of developer.