Calibration with Currently Available Low-Radiopacity Catheters for Scaling in Digital Quantitative Coronary Angiography

RATIONALE AND OBJECTIVES: In quantitative coronary angiography, the absolute diameters of coronary artery lumina are obtained by using a catheter as a scaling device. METHODS: We examined the effect of x-ray opacity on the accuracy of calibration methods that use such catheters by varying the concentration of contrast medium in the catheters in phantom experiments with a digital cine imaging system. RESULTS: With contrast-filled, currently available catheters, the average increase in the measured calibration factor from the gold standard (as determined by using a measuring scale) was 1.0% and 0.4% in the 13-cm and 17-cm image-intensifier modes, respectively, compared with -9.9% and -12.4% for catheters without contrast medium. The corresponding figures for catheters of the previous generation that lacked contrast medium were 1.0% and 0.4%, respectively. The image contrast of previous-generation catheters filled with saline was closer to that of current-generation catheters filled with contrast medium than that of current-generation catheters filled with saline. CONCLUSIONS: When used for quantitative coronary angiography by digital angiography, currently available low-radiopacity catheters give more accurate data when filled with contrast medium.