Use of a metal ring‐marked catheter for geometric calibration in quantitative coronary angiography

Quantitative coronary angiography depends on accurate measurement of catheter shaft diameter for correction of X-ray magnification errors. We compared the use of coronary catheters with a single metal ring (R), inserted during manufacture, with measurements using the edges of the catheter shaft (S) as a calibration mark. Both ring and shaft were 2.50 mm in diameter. On unmagnified X-ray images, the ring measured 2.49 +/- 0.40 mm, and the shaft measured 2.39 +/- .040 mm in diameter. Quantitative coronary angiography using both ring and shaft for calibration provided the same percent stenosis (R:72 +/- 12; S: 71 +/- 13), but stenosis cross-sectional area was 28% different (R: 1.44 +/- .24; S: 1.84 +/- .34 mm2). Use of the catheter shaft for calibration causes overestimation of actual coronary artery dimensions. To prevent this problem, absolute measurements of coronary artery dimensions should be made with metal ring-marked catheters.