Clinical magnetic resonance image quality of the equine foot is significantly influenced by acquisition system

Background Investigation of image quality in clinical equine magnetic resonance (MR) imaging may optimise diagnostic value. Objectives To assess the influence of field strength and anaesthesia on image quality in MR imaging of the equine foot in a clinical context. Study design Analytical clinical study. Methods Fifteen equine foot studies (five studies per system) were randomly selected from the clinical databases of three MR imaging systems: low-field standing (LF St), low-field anaesthetised (LF GA) and high-field anaesthetised (HF GA). Ten experienced observers graded image quality for entire studies and seven clinically important anatomical structures within the foot (briefly, grade 1: textbook quality, grade 2: high diagnostic quality, grade 3: satisfactory diagnostic quality, grade 4: non-diagnostic). Statistical analysis assessed the effect of anaesthesia and field strength using a combination of the Pearson chi-square test or Fisher's exact test and Mann-Whitney test. Results There was no difference in the proportion of entire studies of diagnostic quality between LF St (90%, 95% CI 78%-97%) and LF GA (88%, 76-95%,P = .7). No differences were evident in the proportion of diagnostic studies or median image quality gradings between LF St and LF GA when assessing individual anatomical structures (both groups all median grades = 3). There was a statistically significant difference in the proportion of entire studies of diagnostic quality between LF GA and HF GA (100%, 95% CI lower bound 94%,P = .03). There were statistically significant differences in median image quality gradings between LF GA (all median grades = 3) and HF GA (median grades = 1 (5/7 structures) or 2 (2/7 structures) for all individual anatomical structures (allP < .001). The reasons reported for reduced image quality differed between systems. Main limitations Randomised selection of cases from clinical databases. Individual observer preferences may influence image quality assessment. Conclusions Field strength is a more important influencer of image quality than anaesthesia for magnetic resonance imaging of the equine foot in clinical patients.