P138 Influence of Ultrasound Settings on Carotid Biomarker Assessment by B-Mode Image Processing

Abstract

Purpose/Background/Objectives

This study aims to investigate how image settings affect carotid Intima-Media-Thickness (IMT) and diameter estimation performed with CarotidStudio (Quipu Srl).

Methods

14 healthy volunteers (24.4 ± 4.4 years; 8 men) were recruited. Longitudinal scans 3cm deep of common-carotid-arteries with the same region-of-interest were obtained by expert operator, starting from a “default” setup (central Time Gain Compensation-TGC; gain:50 dB; no persistence filter) and adjusting one parameter at a time (oblique TGC; gain:10 dB increments from 30 to 70 dB; persistence filter). The acquisition was performed twice and repeatability was expressed for each setup as coefficient of variation (CV). Significant changes (p < 0.05) with respect to the “default” setup were analysed by paired Student-t-test.

Results

A 70 dB gain results in overestimating IMT (from 0.46 mm ± 0.01 mm to 0.54 mm ± 0.01 mm), underestimating diameter (from 6.04 mm ± 0.04 mm to 5.70 mm ± 0.23 mm), increasing their CVs (from 2.14% ± 1.92% to 6.85% ± 5.23% for IMT, from 1.79% ± 1.22% to 4.77% ± 4.71% for diameter) and in 4/14 cases the estimation wasn’t possible. Distension CV increases also with 60 dB (from 5.71% ± 4.31% to 10.84% ± 5.91% and to 12.59% ± 7.97%). Persistence and TGC do not affect repeatability, whereas diameter (5.96 mm ± 0.03 mm) and distension (from 0.82 mm ± 0.02 mm to 0.66 mm ± 0.02 mm) values are influenced by persistence.

Conclusions

CarotidStudio precision does not show significant alterations except from 70 dB gain, which, due to the image grey-level saturation, results in poor image quality and modified values. Persistence does not affect precision but leads to reduced diameter and distension, possibly for the intrinsic behaviour of mathematical operator and image temporal filtering. Gain and persistence influence ultrasound biomarker estimation; the chosen setup should be documented and replicated in follow-up scans.