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 (all P < .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.