OPTIMAL SAMPLING INTERVAL AND EDGE-DETECTION ALGORITHM FOR MEASUREMENT OF BLOOD-VESSEL DIAMETER ON A CINEANGIOGRAM

RATIONALE AND OBJECTIVES. The authors studied the effects of image mag nification and the type of edge detection filter on the precision of m easuring blood vessel diameters on coronary angiograms. METHOD. A bloo d vessel phantom containing five channels of various diameters filled with contrast medium was filmed. The magnifications examined were x4, x10, and x20, and the edge detection filters used were the first deriv ative, second derivative, composite, and entropy filters. The regressi on line y = a + bx was introduced, where x represents the nominal diam eter and y the diameter measured by the edge-detection filters. Determ ination criteria were the offset, slope, and residual variance from th e regression equation. RESULTS. The best value among three criteria wa s obtained with a magnification of x10 or x20. The entropy filter gave the best value of slope and residual variance. The composite filter g ave the best value of offset. CONCLUSION. The most precise measurement is obtained when the entropy filter and a magnification of x10 or x20 are applied.