Quantitative coronary arteriography: current status and future.

Quantitative coronary arteriography (QCA) has been accepted as a means for the objective assessment of vessel sizing. Gradient field transform (GFT) is now available as a third generation QCA approach for the quantification of complex morphology. In the meantime the DICOM-3 (DICOM: Digital Imaging and Communications in Medicine) standard has been accepted for the exchange of digital data acquired in a catheterization laboratory. Issues to be resolved in digital imaging include the basic question of whether the commonly used matrix size of 512 x 512 pixels and 8 bits of density resolution is really sufficient to appreciate the same fine details as are visible on cinefilm. Other major issues of differences between the conventional cinefilm and the modern digital approach are edge enhancement and image compression. We believe that digital imaging and the DICOM-3 standard are here to stay; although the transition period may take longer and be hampered in practice by more hurdles than were originally anticipated, in a few years' time, 35-mm film will be an exception.

Inaccuracy of quantitative coronary arteriography when analyzed from S-VHS videotape.

In the transition period between 35-mm cinefilm as the medium for coronary arteriographic data and digital media such as CD-R, S-VHS videotape has been used both as an exchange and store medium, and for quantitative coronary arteriographic (QCA) studies. To determine the extent to which S-VHS video tape affects QCA measurements, an X-ray phantom study was completed. A plexiglass phantom with 12 straight circular tubes (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 image intensifier with the phantom tubes positioned horizontally as well as vertically in the field of view. The digitally acquired images were recorded on S-VHS tape without any image enhancement (raw data) and with default image enhancement. Video frames were then selected on a professional VCR such that individual tubes were positioned in the center of the field of view and digitized (512(2) x 8 bits) with a high-quality frame grabber onto a QCA workstation. The contours along the individual tubes were defined using previously validated automated contour 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 signal-to-noise ratio and the limited bandwidth of the S-VHS video tape, the following objective observations were made: 1) large overestimations (up to 0.87 mm) occur for tube sizes below 1 mm for vertically positioned tubes; 2) random errors in measurements are much larger for vertically positioned tubes (0.36 mm, 7" II) than for horizontally positioned tubes (0.17 mm, 7" II); and 3) little differences in results between enhanced and nonenhanced images were found due to these deteriorating factors. In conclusion, S-VHS video tape is unacceptable for QCA and should be excluded from quantitative angiographic clinical trials.