New-generation 0.55T MRI in patients with total hip arthroplasty: a comparison with 1.5T MRI.

PURPOSE

To quantitatively and qualitatively compare the magnitude of metal total hip arthroplasty-induced imaging artifacts in vivo between 1.5T and 0.55T MRI.

MATERIALS AND METHODS

15 patients (69 ± 14 years) with THA, prospectively underwent 0.55T and 1.5T MRI of the hip. Two fellowship-trained musculoskeletal radiologists qualitatively rated artifact magnitude on T1-weighted and fluid-sensitive sequences using a 5-point Likert scale (0 = severe - 5 = no artifact). Quantitative artifact magnitude was assessed by a third fellowship-trained musculoskeletal radiologist, by measuring the maximum diameter of the THA-induced signal void (mm) anteroposteriorly d(ap) and mediolaterally d(ml) at the level of the acetabulum, proximal, mid and distal stem, including the prosthesis. Additionally, the area of signal void was noted (mm). Statistical differences between Likert scores were evaluated using the t-test or the Wilcoxon signed-rank test (P-values <.05 = significant).

RESULTS

Qualitative artifact magnitude was on average rated as moderate to small on 0.55T and as large to moderate on 1.5T by both readers. Artifacts were rated less severe on 0.55T compared with 1.5T on T1-weighted (3.7 ± 0.7 vs. 2.4 ± 1.1, p=0.004) and fluid-sensitive sequences (3.1 ± 0.5 vs. 2.2 ± 1.1, p=0.18). Overall image quality did not show any statistically significant differences between 0.55T and 1.5T MRI (each p≥0.18). Metal artifacts' areas and diameters were smaller on 0.55T when compared with 1.5T MRI for all sequences (each p>0.016).

CONCLUSIONS

Total hip arthroplasty-induced metal artifacts are perceived as less severe at new-generation 0.55T when compared with conventional 1.5T MRI with no difference in overall image quality.