Reproducibility of measurements of coronary narrowings by videodensitometry: Unreliability of single view measurements

Abstract

Computer-assisted videodensitometry has been shown to be a reliable and reproducible method of measuring absolute and relative coronary narrowings. Using a commercially available analyzer (Vanguard XR70) we confirmed the intra- and interobserver reproducibilities in 34 narrowings in 9 patients. Analyses were performed on normal area and diameter, stenotic area and diameter, percent area stenosis and percent diameter stenosis. For all 6 analyses, excellent intra- and interobserver correlations were found (r = 0.93-0.98), with slopes close to 1 and intercepts close to zero. In a separate study of 16 lesions in 11 patients, each lesion was analyzed in both the RAO and LAO planes. Correlation between the measurements was reasonable with r = 0.76 for the stenotic area and r = 0.75 for the absolute diameter stenosis. However, with suboptimal slopes (0.54 and 0.63 respectively), actual differences between measurements in the two planes were often unacceptably large. These data suggest that videodensitometry is a highly reproducible quantitative angiographic method; however, single view analyses are inadequate for comparative studies.

The impact of vessel orientation in space on densitometric measurements of cross sectional areas of coronary arteries

“…The correlation between the uncorrected cross sectional areas As1 and As2 was moderate (Figure 1), but somewhat better than correlations published by other authors [14][15][16]. This is probably due to the 3D calibration, and possibly also to the rather vigorous and sustained contrast medium injections.…”

“…The potential accuracy of this approach has been confirmed by many in vitro and in vivo studies [1][2][3][4][5][6][7][8][9][10][11][12][13]. Yet strong discrepancies between cross sectional areas (in mm 2) measured in two projections in patients have also been reported [14][15][16]. Among the many possible reasons for such findings, non-perpendicularity of the vessel axes involved with the relevant x-rays is probably an important one because: (1) densitometry can be rather sensitive to the actual orientation of the cross sections in space, in contrast to geometric methods, and: (2) it is practically impossible to achieve an optimal orientation of the two cross sections of interest with respect to both planes (or even to only one of them.)…”

Reproducibility of Measurements of Coronary Narrowings by Videodensitometry and by Digital Calipers

“…Theoretically, these precautions should not be necessary for videodensitomet ric studies, but we [11] and others [24] have shown that measurements of lesions in differ ent projections give widely different results.…”

“…The apparatus used for video densitometry was a Vanguard XR70 Analyzer. The system has been described in detail in recent publica tions [9][10][11] and the techniques used were those re ported by these authors. Briefly, as described, a dia stolic frame from the coronary cineangiogram was cho sen for analysis which satisfied the following criteria: the frame was selected from the mid-phase of the injec tion with the vessel well filled: the radiographic projec tion chosen was approximately at right angles to the X-ray beam, in order to display the long axis of the vessel without foreshortening; there was no overlap ping of side branches at the stenotic or normal seg ment: finally the catheter and arterial segments were not on the extreme margins of the field.…”

Towards a gold standard for quantitative coronary arteriography

“…The alternative approach, densitometry, has always proven in vitro to be at least equivalent to the geometric techniques for circular lumens, and clearly superior for small or non-circular ones (Sandor et al 1979, Doriot et al 1982, Nichols et al 1984, Di Mario et al 1992. In patients, however, appreciable discrepancies between cross sectional areas or area reduction percentages measured independently in two different projections have been reported by some authors (Sanz et al 1987, Tobis et al 1987, Katritsis et al 1988, Nichols et al 1988, Balkin et al 1990, Escaned et al 1993. Among the reasons that can explain such discrepancies, one is the sensitivity of densitometry to the actual orientation of the x-rays relatively to the vessel axis in space.…”