Reproducibility of intravascular ultrasound iMAP for radiofrequency data analysis: implications for design of longitudinal studies.

BACKGROUND

iMAP is a new intravascular ultrasound (IVUS) derived technique for tissue characterization using spectral analysis. Since there is a need for reproducibility data to design longitudinal studies, we sought to assess the in vivo reproducibility of this imaging technique.

METHODS

iMAP (40 MHz, Boston Scientific Corporation) was performed in patients referred for elective percutaneous intervention and in whom a nonintervened vessel was judged suitable for a safe IVUS analysis. Overall 20 patients with 20 non-angiographically significant lesions were assessed by two independent observers. Five of these 20 patients received an additional iMAP analysis using a new IVUS catheter and using the same catheter after its engagement and reengagement.

RESULTS

The interobserver relative difference in plaque area was 2.5%. Limits of agreement for lumen, vessel, and plaque area measurements were 1.62, -2.47 mm(2) ; 2.09, -3.71 mm(2) ; 2.80, -3.72 mm(2) ; respectively. Limits of agreement for fibrotic, lipidic, necrotic, and calcified measurements were 1.32, -1.44 mm(2) ; 0.24, -0.36 mm(2) ; 1.50, -2.26 mm(2) ; 0.09, -0.11 mm(2) ; respectively. The intercatheter and intracatheter relative difference in plaque area were 0.9% and 4.1%, respectively. Although the variability for compositional measurements increased using two different catheters or using the same catheter twice, the variability for compositional measurements keeps always below 10%.

CONCLUSIONS

Our analysis demonstrates that the geometrical and compositional iMAP analysis is acceptably reproducible.