This chapter presents a new method to assess brachial artery vasodilation in US sequences. This method, based on image registration, minimizes the effect of low-level artifacts. It also incorporates a motion compensation phase, which relieves the operator of manually tracking a region of interest.

The method is accurate (bias = +0.05%, and limits of agreement ± 2.05 %FMD), has better reproducibility (CV = 0.40%) than manual measurements (CV = 1.04%), and is robust, yielding clinically relevant information in at least 80% of the sequences in an uncontrolled setting. Finally, the method requires minimal user intervention having limited effect on the repro-ducibility of the measurements.

In this work we have also introduced a novel parameterization of the va-sodilation curve in the FMD test. This parameterization is of applicability in conjunction with the FMD measurement technique provided in this chapter or with any other alternative (e.g. [12-20]). We have shown that this parameterization yields a number of FMD-related indexes that are consistent with the traditional AFMDc coefficient and basically replicates previous findings in the literature linking FMD to serum lipid levels. This parameterization has several advantages over the classical alternative as it captures more comprehensive information of vasodilation and does not require manual selection of the FMD peak or baseline diameters to extract EigenD modes from absolute diameter curves. However, EigenFMD modes still require manual determination of the basal FMD level or diameter to process relative or absolute curves, respectively. More important, EigenFMD and EigenD coefficients bear a graphical interpretation in terms of FMD-peak, time-to-FMD-peak, recovery speed, etc. This can be useful to gain understanding in the relationship between the dynamics of the endothelium dependent vasodilation and the underlying processes related to endothelial dysfunction. Although this method enables such investigations that are impossible with classical measurements of FMD, further clinical research is required to fully validate its utility.

0 0

Post a comment