There is some controversy of the accuracy of observing the lesion MLD itself, since many atherosclerotic lesions may create uneven "hills and valleys" within the lumen, making a true MLD difficult to obtain or estimate. Some research indicates calculating "area stenosis" is also a valid measure of actual vessel stenosis compared to diameter stenosis alone, but this requires additional analysis because a tracing of the lumen border must be performed. However, there are computer programs available to automatically perform this function. It may be helpful to obtain both percent diameter and area percent stenosis, especially since the two percentages may not always correlate with each other.