INACCURACY OF QUANTITATIVE CORONARY ARTERIOGRAPHY WHEN ANALYZED FROM S-VHS VIDEOTAPE

In the transition period between 35-mm cinefilm as the medium for coro nary arteriographic data and digital media such as CD-R, S-VHS videota pe has been used both as an exchange and store medium, and for quantit ative coronary arteriographic (QCA) studies. To determine the extent t o which S-VHS video tape affects QCA measurements, an X-ray phantom st udy was completed. A plexiglass phantom with 12 straight circular tube s (0.51-5.00 mm in diameter) filled with contrast medium was recorded under clinical conditions using both the 5 '' and 7 '' modes of the im age intensifier with the phantom tubes positioned horizontally as well as vertically in the field of view, The digitally acquired images wer e recorded on S-VHS tape without any image enhancement (raw data) and with default image enhancement. Video frames were then selected on a p rofessional VCR such that individual tubes were positioned in the cent er of the field of view and digitized (512(2) x 8 bits) with a high-qu ality frame grabber onto a QCA workstation. The contours along the ind ividual tubes were defined using previously validated automated contou r detection techniques, For each tube, an average diameter (mm) and a standard deviation (mm) were calculated. Calibration was based on a cm grid acquired at the same geometry as the phantom, Due to the poor si gnal-to-noise ratio and the limited bandwidth of the S-VHS video tape, the following objective observations were made: 1) large overestimati ons (up to 0.87 mm) occur for tube sizes below 1 mm for vertically pos itioned tubes; 2) random errors in measurements are much larger for ve rtically positioned tubes (0.36 mm, 7 '' II) than for horizontally pos itioned tubes (0.17 mm, 7 '' II); and 3) little differences in results between enhanced and nonenhanced images were found due to these deter iorating factors. In conclusion, S-VHS video tape is unacceptable for QCA and should be excluded from quantitative angiographic clinical tri als. (C) 1995 Wiley-Liss, Inc.