Non-Invasive Vascular Very-High Resolution Ultrasound to Quantify Artery Intima Layer Thickness: Validation of the Four-Line Pattern

Preliminary findings suggest that very-high resolution ultrasound (VHRU, 55 MHz) could differentiate arterial intima layer thickness (IT) non-invasively in vivo. We aimed to validate ultrasound-derived IT measurements and describe a four-line pattern consistent with intimal thickening. VHRU was applied to temporal arteries of 37 patients with suspected giant cell arteritis without inflammation on histology. Anatomically matched ultrasound-derived measurements of arterial layer thickness with the leading-edge method was compared to histology. Intimal thickening (IT >0.06 mm on histology) was identified as a four-line pattern in VHRU with a sensitivity of 96.3% and a specificity of 100%. Histologic and VHRU IT measurement agreement was excellent (mean difference 0.007 mm; 95% limits of agreement, −0.043 to 0.057) and intra-class coefficient (ICC) 0.923 (95% confidence interval [CI], 0.833–0.964). Intra- and inter-observer agreements for VHRU IT were high: ICC 0.946 (95% CI, 0.877–0.976) and 0.872 (95% CI, 0.773–0.943). VHRU utilizing the leading-to-leading edge method allows accurate and reliable measurements of arterial IT in patients with IT >0.06 mm. Measurements of IT will provide the opportunity to explore early subclinical structural intimal changes in the arterial wall increasing with age.