Intravascular Ultrasound Radiofrequency Research Articles

Geometrical validation of intravascular ultrasound radiofrequency data analysis (Virtual Histology) acquired with a 30 MHz boston scientific corporation imaging catheter

Recently, the plaque characterization field was explored with the use of the substrate (frequency domain analysis) rather than the envelope (amplitude or gray-scale imaging) of the intravascular ultrasound (IVUS) radiofrequency data. However, there is no data about the agreement of quantitative outcome between the two methods. The aim of this study was to assess the correlation and agreement between quantitative coronary ultrasound and the geometrical measurements provided by the spectral analysis of ultrasound radiofrequency data [IVUS-Virtual Histology (IVUS-VH), Volcano Therapeutics). Twenty-five patients were included in this study. The IVUS catheter used was a commercially available mechanical sector scanner (Ultracross 2.9 Fr 30 MHz catheter, Boston Scientific) covered with an outer sheath. IVUS-VH significantly underestimated lumen [relative difference (RD)=14.8+/-5.6; P<0.001], vessel (RD=14.1+/-4.8; P<0.001), and plaque (RD=11.5+/-10.8; P<0.001) cross-sectional areas (CSAs). Nevertheless, when adjusted for the ultrasound propagation delay caused by the sheath, relative differences of measurements were remarkably low (0.49%+/-6.3%, P=0.64 for lumen; 2.33%+/-4.6%, P=0.007 for vessel; and 4.2%+/-10.4%, P=0.005 for plaque CSA). These data suggest that the volumetric output of the IVUS-VH software underestimates measurements when acquired with a 30 MHz catheter. However, after applying a mathematical adjustment method for the ultrasound propagation delay caused by the outer sheath of the 30 MHz catheter, relative differences of direct measurements were negligible. These results suggest that ultrasound radiofrequency data analysis could provide, aside from precise compositional data, an accurate geometrical output.

1006-58 The relation between the statin's effects on coronary plaque composition and plasma low-density lipoprotein cholesterol level evaluated by intravascular ultrasound radiofrequency signal analysis

1006-58 The relation between the statin's effects on coronary plaque composition and plasma low-density lipoprotein cholesterol level evaluated by intravascular ultrasound radiofrequency signal analysis

Significance of cyclic variation of integrated backscatter in intravascular ultrasound radio-frequency signal analysis for coronary atherosclerosis Nobuyuki Komiyama, Akio Oshima, Matthew L. Kolz, Brian Courtney, Paul G. Yock, Peter J. Fitzgerald. Chiba University Hospital, Chiba, Japan, Stanford University Medical Center, Stanford, CA

Significance of cyclic variation of integrated backscatter in intravascular ultrasound radio-frequency signal analysis for coronary atherosclerosis Nobuyuki Komiyama, Akio Oshima, Matthew L. Kolz, Brian Courtney, Paul G. Yock, Peter J. Fitzgerald. Chiba University Hospital, Chiba, Japan, Stanford University Medical Center, Stanford, CA

Tissue characterization of atherosclerotic plaques by intravascular ultrasound radiofrequency signal analysis: An in vitro study of human coronary arteries

Background Conventional gray-scale images of intravascular ultrasound (IVUS) cannot accurately differentiate histologic subtypes of sonolucent coronary plaques with or without a lipid core. Methods We analyzed radiofrequency signals obtained in vitro from 24 regions of interest (ROI) of noncalcified (sonolucent) plaques in 10 atherosclerotic coronary artery specimens pressure-fixed by formalin. Radiofrequency signals were sampled with a 30-MHz IVUS catheter and digitized at 500 MHz in 8-bit resolution. The ROIs were histologically categorized into 12 plaques with a lipid core and 12 plaques without it. Integrated backscatter and statistical parameters of the radiofrequency envelope (mean/SD ratio [MSR], skewness, and kurtosis) within the ROI were calculated offline, and their ability to detect a lipid core was compared with visual analysis of the IVUS video images. In the group with lipid cores, percent area of a lipid core in each ROI was measured in a digitized histologic image by a computerized planimeter. Results Sensitivity and specificity of MSR, skewness, and kurtosis for lipid core detection were substantially greater than visual video image analysis (83.3% and 91.7%, 100% and 91.7%, 100% and 91.7% vs 53.3% and 71.7%). Furthermore, the parameters of integrated backscatter, MSR, skewness, and kurtosis were significantly correlated to percent of core area (r = –0.64, –0.73, 0.78, and 0.63, respectively; P < .05). Conclusions Compared with IVUS video images, the parameters of radiofrequency signal analysis may be used to aid in more accurate detection and quantitative evaluation of a lipid core, which is one of the major factors of a vulnerable coronary plaque. (Am Heart J 2000;140:565-74.)

The progression of thrombus in an ex-vivo shunt model evaluated by intravascular ultrasound radiofrequency analysis

We tested the ability of ultrasound radiofrequency (RF) signal analysis to characterize thrombus accumulation in a Dacron graft incorporated into the exteriorized arteriovenous shunt in 3 baboons with constant blood flow for 60 min. Thrombus formation was quantified by sequential measurements of 111Indium-labeled platelet deposition. RF signals were acquired every 15 min at 2 sites in the graft, using a 2.9 Fr intravascular ultrasound catheter-based transducer (30 MHz) and digitized at 250 MHz in 8-bit resolution. Regions of interest were placed within a 0.5-mm perimeter adjacent to the graft wall. Integrated backscatter increased significantly ( p < 0.001) with increasing platelet deposition. However, mean-to–standard deviation ratio of the RF envelope showed no significant change and the distribution pattern of the RF probability function remained constant and consistent with a Rayleigh scattering process. These results provide a basis for using RF analysis to monitor the time-course of thrombus formation.