Multi‐system evaluation of baseline‐referenced gray scale CNR profile deviation for phantom‐based ultrasound quality assurance
Ji‐Hye Kim, Yeong‐Cheol HeoAbstract
Background
Phantom‐based ultrasound quality assurance (QA) commonly incorporates qualitative image assessment, whereas robust baseline‐referenced quantitative indicators for routine monitoring across multiple systems remain limited.
Purpose
To investigate whether controlled transducer surface acoustic shielding produces measurable baseline‐referenced changes in selected dead zone (DZ) and gray scale (GS) indicators across multiple ultrasound systems using an ATS‐539 phantom.
Methods
Four ultrasound systems (GE LOGIQ P10, GE LOGIQ P6, Mindray DC‐70 Exp, and Siemens X150) were evaluated. The transducer aperture was partially shielded with insulating tape at 0%, 5%, 10%, 15%, 20%, and 30% coverage, applied either centrally or at the indicator‐side margin. Five repeated images were acquired for each condition. GS performance was assessed using the contrast‐to‐noise ratio (CNR) of six cylindrical targets. Target‐specific CNR values were converted to within‐device z‐deviations relative to baseline (L0), and the root‐mean‐square z‐deviation across all six targets (RMS‐z) was used as the primary GS profile indicator. DZ performance was evaluated using landmark‐based pin brightness as a secondary near‐field indicator.
Results
Under central shielding, the GS RMS‐z profile deviation score increased with shielding ratio in all four systems (Spearman ρ = 0.642–0.975, all p < 0.001). Central shielding produced consistent RMS‐z increases across all four systems, whereas indicator‐side shielding yielded a more heterogeneous response: RMS‐z remained positively associated with shielding ratio in three systems ( ρ = 0.734–0.917, all p < 0.001), but the response was weaker and non‐significant in the GE LOGIQ P10. Central DZ pin brightness decreased with increasing shielding ratio across all systems ( ρ = −0.581 to −0.865, all p < 0.001). Baseline CNR profiles and absolute CNR magnitudes differed substantially among systems, and within‐device baseline referencing was therefore preferred over direct cross‐system comparison. Manual landmark placement demonstrated high repeatability for target‐specific CNR and DZ brightness measurements (ICC(A,1) = 0.88–0.97), whereas the aggregate RMS‐z score showed moderate‐to‐good repeatability (ICC(A,1) = 0.771).
Conclusions
Baseline‐referenced GS CNR profile deviation demonstrated a consistent response to controlled acoustic shielding across multiple ultrasound systems. DZ brightness provided complementary near‐field information but remained a secondary indicator. These findings support device‐specific longitudinal monitoring of phantom‐based QA metrics rather than interpretation based on universal cutoff values.