Purpose
Quantitative ultrasound (QUS) provides objective indices of Vision Degrading Myodesopsia (VDM) that correlate with contrast sensitivity (CS). To date, QUS methods were only tested on a single ultrasound machine. Here, we evaluate whether QUS measurements are machine independent.
Methods
In this cross-sectional study, 47 eyes (24 subjects; age = 53.2 ± 14.4 years) were evaluated with Freiburg acuity contrast testing (%Weber), and ultrasonography using 2 machines: one with a 15-MHz single-element transducer and one with a 5-ring, 20-MHz annular-array. Images were acquired from each system in sequential scans. Artifact-free, log-compressed envelope data were processed to yield three parameters (mean amplitude,
M
; energy,
E
; and percentage filled by echodensities,
P50
) and a composite score (
C
). A B-mode normalization method was applied to the 20-MHz datasets to match QUS parameters at both frequencies. Statistical analyses were performed to evaluate correlations among CS,
E
,
M
,
P50
, and
C
for both machines.
Results
QUS parameters from each machine correlated with CS (
R
≥ 0.57,
P
< 0.001) and there was correlation between machines (
R
≥ 0.84,
P
< 0.001). Correlations between CS and QUS parameters were statistically similar for both machines (
P
≥ 0.14) except when the 20-MHz data were normalized (
P
= 0.04). Reproducibility of QUS parameters computed from 20-MHz data were satisfactory (52.3%–96.3%) with intraclass correlation values exceeding 0.80 (
P
< 0.001).
Conclusions
The high correlation between QUS parameters from both machines combined with a statistically similar correlation to CS suggests QUS is an effective, machine-independent, quantitative measure of vitreous echodensities.
Translational Relevance
QUS may be applied across clinical ophthalmic ultrasound scanners and imaging frequencies to effectively evaluate VDM.