Common carotid intima-media thickness: does it matter how it is measured

Intima media thickness (IMT) has proved to be a useful tool in predicting cardiovascular morbidity. However, methods are not well standardized, and several software packages softwares are available although they have never been compared with one other. Thus, the extrapolation of data from large studies might be questionable on routine practice. Our objective was to compare 2 software packages largely used for semi-automatic measurement of IMT.

We have measured IMT on left and right common carotid in 97 patients in standardized conditions.

The same image was processed through the 2 software (Metris and Iôdp). There was no difference for IMT measured at various times by the same investigator, although the number of measurable points increased as the operator became more experienced. The number of measurable points was significantly greater with Iôdp. IMT was lower with Iôdp than Metris (mean difference 0.066 mm on the right side).

These results suggest that the same software must be used for repeated measurements in 1 patient. One must be careful in using data from large studies or normality values. At the individual level, the use of IMT to determine vascular risk is dependent upon the software used. It is urgent to standardize the methods of IMT measurement.