B-mode versus A-mode ultrasonographic measurements of mucosal thickness in vivo

Objective. The objective of this study was to compare the measurement accuracy of A-mode and B-mode ultrasonographic assessments of palatal masticatory mucosal thickness in vivo. Study design. Thickness of palatal masticatory mucosa in the molar region of 50 volunteers was measured once with a B-mode ultrasound device (10 MHz) combined with a standoff for intraoral applications. At identical reading points thickness was also assessed with an A-mode device (5 replicates) and by needle probing for determination of true thickness. Results. On average true thickness ranged between 2.9 and 3.3 mm (95% confidence intervals; median, 3.1 mm). B-mode ultrasonography overestimated truth by 0.19 mm (median) and differed significantly from truth (P=.008), whereas A-mode ultrasonography slightly underestimated true thickness by -0.05 mm (median). Limits of agreement were wider for A-mode ultrasonography (2.00 mm) than for B-mode ultrasonography (0.88 mm). Conclusions. Because accuracy of 0.2 mm is acceptable for many clinical indications, B-mode and A-mode yield sufficient accuracy for measurements of mucosal thickness.