Validation of quantitative analysis of intravascular ultrasound images

This study investigated the accuracy and reproducibility of a computer-aided method for quantification of intravascular ultrasound. The computer analysis system was developed on an IBM compatible PC/AT equipped with a framegrabber. The quantitative assessment of lumen area, lesion area and percent area obstruction was performed by tracing the boundaries of the free lumen and original lumen. Accuracy of the analysis system was tested in a phantom study. Echographic measurements of lumen and lesion area derived from 16 arterial specimens were compared with data obtained by histology. The differences in lesion area measurements between histology and ultrasound were minimal (mean ± SD: -0.27±1.79 mm2, p>0.05). Lumen area measurements from histology were significantly smaller than those with ultrasound due to mechanical deformation of histologic specimens (-5.38±5.09 mm2, p0.05). Finally, intra- and interobserver variability of our quantitative method was evaluated in measurements of 100 in vivo ultrasound images. The results showed that variations in lumen area measurements were low (5%) whereas variations in lesion area and percent area obstruction were relatively high (13%, 10%, respectively). Results of this study indicate that our quantitative method provides accurate and reproducible measurements of lumen and lesion area. Thus, intravascular ultrasound can be used for clinical investigation, including assessment of vascular stenosis and evaluation of therapeutic intervention

The angle of incidence of the ultrasonic beam: a critical factor for the image quality in intravascular ultrasonography

The effects of the angle of incidence of the ultrasound beam on the image quality were studied in 21 pressurized arterial specimens examined with a 30 MHz intravascular ultrasonographic catheter. When the ultrasonographic catheter was in an eccentric position in the vessel lumen, the videodensity of the segments of the vessel wall with the least favorable angle of interrogation (a shift of 49 +/- 6 degrees from the tangent to the tissue surface) was 27% +/- 19% lower than the videodensity measured with the catheter in the center of the lumen. When the catheter was placed in a position that was not parallel to the long axis of the vessel, a further decrease was observed, especially in the vessel wall opposite the position of the catheter. An artificial dissection was induced in eight specimens. Dropouts that involved the dissection plane and the underlying structures were produced with positions of the echographic catheter inducing a narrow angle between ultrasound beam and dissection plane. These ex