Assessment of cervical spine CT by an image quality audit using qualitative and quantitative methods

To study the feasibility and assess the correlation of qualitative and quantitative methods for an image quality (IQ) audit of a Cervical spine CT.

Five radiologists retrospectively performed a blinded visual grading analysis (VGA) on 20 studies (10 from Protocol 1 and 10 from Protocol 2), using the RANZCR CT IQ Self-Audit worksheet. A Visual Grading Analysis Score (VGAS) and Area under the curve using Visual Grading Characteristics (AUC_VGC) were the figures of merit. Quantitative metrics for noise and contrast were correlated to the qualitative assessment.

No statistically significant difference was observed in the IQ, VGAS_Protocol 1 = 0.65, 95% CI [0.54, 0.75] and VGAS_{Protocol 2} = 0.73, 95% CI [0.67, 0.79] and AUC_VGC = 0.548, 95% CI [0.40, 0.69]. Protocol 2 indicated a statistically significant average dose reduction of 35% in CTDI_vol (P = 0.020) and a higher noise; however, the difference was statistically insignificant. There was a moderate correlation between the manual noise measurements in soft tissue and air (P = 0.035) and a strong correlation between the manual and automated noise measurements (P < 0.001). The contrast resolution-based quantitative parameter, EdgeGradientSoft, correlated to the qualitative scores (P = 0.031).

Validated VGA tools can be used for IQ audits; however, tailoring the image criteria and rating scale to the clinical practice is suggested. The use of contrast-based IQ metrics showed encouraging results, and further larger-scale studies are needed to explore their potential use in quality management.