Dedicated calibration formulas permit correction of differences between measurements by different IVUS devices as demonstrated in atherosclerotic human coronary arteries in vitro

Abstract

Serial intravascular ultrasound (IVUS) measurements of coronary vessel dimensions are major endpoints of studies focusing on pharmacological interventions, efficiency of drug eluting stents, and vascular remodeling. In serial studies measurement variability among different IVUS devices may cause substantial misinterpretation and error. We analyzed 33 human coronary plaques in vitro using two different IVUS systems (mechanical IVUS system with a 40 MHz Atlantis SR catheter; solid-state electronic IVUS system with a 20 MHz Invision catheter) and repeatedly measured the total vessel, lumen, and plaque + media cross-sectional area and plaque burden (plaque + media area divided by total vessel area). Between the "raw" measurements made by the two devices, there was a significant difference for both plaque + media area (2.35+/-1.86 mm(2), P < 0.01) and plaque burden (5.39+/-3.68%, P < 0.05). Measurements were then corrected by use of recently introduced calibration formulas; as a result the differences decreased significantly for all IVUS parameters measured ( P < 0.0001). After correction, the remaining differences between the corrected mechanical and solid-state IVUS measurements similar to differences between repeated measurements with the same IVUS device (i.e., the intraobserver variability). Thus, in serial studies the use of different IVUS devices at index and follow-up procedure may introduce a substantial error as a result of system-related differences. The application of dedicated calibration formulas allows for correction for these differences by decreasing such differences to the level of intraobserver variability.

Reproducibility of volumetric intravascular ultrasound radiofrequency-based analysis of coronary plaque composition in vivo

“…The number of coronary segments was limited but comparable to other studies that addressed the reproducibility of IVUS measurements [13–15, 34, 38, 39]. All patients had stable angina pectoris.…”

“…Therefore, measurement reproducibility may be somewhat lower in routine clinical IVUS cases; nevertheless, the selection criteria of target segments in serial IVUS studies are similar [7–10]. Inter-catheter and inter-system variability was not addressed [34, 38, 39]. The high accuracy of the off-line RF-IVUS analysis was achieved at the expense of manual correction of the automatically derived lumen and vessel contours; accordingly, our data may not be generalized to on-line application of RF-IVUS.…”

Comparison of quantitative measurements between two different intravascular ultrasound catheters and consoles: in vitro and in vivo studies

“…We do believe that IVUSderived measurements are accurate and reproducible. However, early studies demonstrated discrepancies in quantitative results between different IVUS systems [9][10][11]. An in vitro study comparing between 40 MHz mechanical IVUS (Atlantis SR/Ultracross, Boston Scientific) and 20 MHz phased array IVUS (InVision/Avanar, Volcano, Rancho Cordova, CA, USA) demonstrated up to 18% differences in quantitative results between the 2 systems [9].…”

“…Intravascular ultrasound (IVUS) is widely used to guide percutaneous coronary intervention (PCI) [1][2][3][4][5] and to assess efficacy of medication or PCI on coronary atherosclerotic plaque or stent in vivo [6][7][8]. Previously, there were discordance in quantitative measurements of the coronary arteries using different IVUS systems from different providers mainly because of the differences in the speed of sound used in each IVUS system [9][10][11]. The aim of this study was to assess compatibility of two different IVUS catheters and consoles for quantitative measurements of coronary arteries.…”

Impact of analyzing less image frames per segment for radiofrequency-based volumetric intravascular ultrasound measurements in mild-to-moderate coronary atherosclerosis

“…The data of this study do not predict whether a reduction of image density may introduce an additional measurement variability (for instance when data are sampled at a pullback speed of 1.0 mm/s instead of 0.5 mm/s). In serial studies, [33] potential variability between different IVUS catheters or IVUS systems may add to the overall measurement variability of RF–IVUS studies [34]. …”