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Digital subtraction angiography: Techniques and applications for evaluating cardiac anatomy and function
Abstract
The conversion of fluoroscopic x-ray data into a digital form has an added advantage for the study of the central cardiovascular system: it permits the contrast enhancement of the images and also facilitates quantitative and functional analysis of the x-ray data. Several applications are described in this article.
... Functional imaging in small animals can be addressed particularly well using x-ray digital subtraction angiography (DSA), given the ease of use and its ability to capture rapid physiological changes in blood flow [1]. Extensive work ranging from initial studies first suggested by Mistretta et al. in the 1970s to evaluating the efficacy of subtraction angiography in clinical diagnosis has been done in canines, porcines, and humans23456789101112. Scaling DSA to the higher temporal and spatial resolutions encountered in the rodent requires unique approaches for an optimal small animal DSA imaging system. ...
... The bolus dilution contributes to increase in blood volume from contrast because one must inject more contrast agent to achieve adequate enhancement. This can lead to retrograde flow and the inability to separate left/right heart and lung [2,4,5,15,17]. The computer-controlled system described here can inject small volumes of contrast agent at high flow rates with high reproducibility at very precise times in the physiological cycles. ...
The availability of genetically altered animal models of human disease for basic research has generated great interest in new imaging methodologies. Digital subtraction angiography (DSA) offers an appealing approach to functional imaging in small animals because of the high spatial and temporal resolution, and the ability to visualize and measure blood flow. The micro-injector described here meets crucial performance parameters to ensure optimal vessel enhancement without significantly increasing the total blood volume or producing overlap of enhanced structures. The micro-injector can inject small, reproducible volumes of contrast agent at high flow rates with computer-controlled timing synchronized to cardiopulmonary activity. Iterative bench-top and live animal experiments with both rat and mouse have been conducted to evaluate the performance of this computer-controlled micro-injector, a first demonstration of a new device designed explicitly for the unique requirements of DSA in small animals. Injection protocols were optimized and screened for potential physiological impact. For the optimized protocols, we found that changes in the time-density curves for representative regions of interest in the thorax were due primarily to physiological changes, independent of micro-injector parameters.
It has been 25 years since my colleagues and I were first approached to apply the then newly emerging technique of coronary arteriography to the study of the effects of the new vasodilator isosorbide dinitrate (ISDN) on coronary arteries in vivo. Through a combination of careful patient assessment and serendipity, we were able to visualize the prompt release of coronary artery spasm by ISDN. Ensuing years have seen dramatic advances both in angiographic techniques and in the knowledge of ISDN efficacy. This review will briefly summarize the early work with ISDN and detail how the improvements in cineangiography have fostered better understanding of the actions of ISDN.
The increasing use of small animals in basic research has spurred interest in new imaging methodologies. Digital subtraction angiography (DSA) offers a particularly appealing approach to functional imaging in the small animal. This study examines the optimal x-ray, molybdenum (Mo) or tungsten (W) target sources, and technique to produce the highest quality small animal functional subtraction angiograms in terms of contrast and signal-difference-to-noise ratio squared (SdNR2). Two limiting conditions were considered-normalization with respect to dose and normalization against tube loading. Image contrast and SdNR2 were simulated using an established x-ray model. DSA images of live rats were taken at two representative tube potentials for the W and Mo sources. Results show that for small animal DSA, the Mo source provides better contrast. However, with digital detectors, SdNR2 is the more relevant figure of merit. The W source operated at kVps >60 achieved a higher SdNR2. The highest SdNR2 was obtained at voltages above 90 kVp. However, operation at the higher potential results in significantly greater dose and tube load and reduced contrast quantization. A reasonable tradeoff can be achieved at tube potentials at the beginning of the performance plateau, around 70 kVp, where the relative gain in SdNR2 is the greatest.
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