Ultrasound imaging cannot discriminate between the intima and media layers because of insufficient axial resolution. Therefore an elevated CIMT may be the result of an increased intima layer from atherosclerosis, an increased media layer due to vascular hypertrophy as seen in hypertension, or both. For this reason, some researchers argue that CIMT, when measured in the absence of intrusive plaque, should be considered as a marker of early arterial wall changes rather than as a true surrogate for atherosclerosis.