In vitro assessment of knee MRI in the presence of metal implants comparing MAVRIC-SL and conventional fast spin echo sequences at 1.5 and 3 T field strength

Abstract

PURPOSE To assess lesion detection and artifact size reduction of a MAVRIC-SEMAC hybrid sequence (MAVRIC-SL) compared to standard sequences at 1.5T and 3T in porcine knee specimens with metal hardware. METHODS Artificial cartilage and bone lesions of defined size were created in the proximity of titanium and steel screws with 2.5 mm diameter in 12 porcine knee specimens and were imaged at 1.5T and 3T MRI with MAVRIC-SL PD and STIR, standard FSE T2 PD and STIR and fat-saturated T2 FSE sequences. Three radiologists blinded to the lesion locations assessed lesion detection rates on randomized images for each sequence using ROC. Artifact length and width were measured. RESULTS Metal artifact sizes were largest in the presence of steel screws at 3T (FSE T2 FS: 28.7cm2) and 1.5T (16.03cm2). MAVRIC-SL PD and STIR reduced artifact sizes at both 3T (1.43cm2; 2.46cm2) and 1.5T (1.16cm2; 1.59cm2) compared to FS T2 FSE sequences (27.57cm2; 13.20cm2). At 3T, ROC derived AUC values using MAVRIC-SL sequences were significantly higher compared to standard sequences (MAVRIC-PD: 0.87, versus FSE-T2-FS: 0.73 (p=0.025); MAVRIC- STIR: 0.9 versus T2-STIR: 0.78 (p=0.001) and versus FSE-T2-FS: 0.73 (p=0.026)). Similar values were observed at 1.5T. Comparison of 3T and 1.5T showed no significant differences (MAVRIC-SL PD: p=0.382; MAVRIC-SL STIR: p=0.071. CONCLUSION MAVRIC-SL sequences provided superior lesion detection and reduced metal artifact size at both 1.5T and 3T compared to conventionally used FSE sequences. No significant disadvantage was found comparing MAVRIC-SL at 3T and 1.5T, though metal artifacts at 3T were larger.

Metal artifact suppression at the hip: diagnostic performance at 3.0 T versus 1.5 Tesla

“…There might be some instances where the residual metal artifact size would prevent an accurate diagnosis and, hence, we believe that a larger population would need to be studied to conclusively investigate potential limitations at the higher field strength. However, a recent publication [15] performed in an animal model found similar diagnostic performance in lesion detection using MAVRIC sequences at both field strengths, which is in agreement with the findings of our study.…”

“…For example, two publications by Lee at al. [15,17] described the application of fat saturated T2-weighted SEMAC sequences for metal artifact 3.0 T image shows less efficient fat-saturation when compared to 1.5 T image. Fat saturation scores were 3 and 1, at 1.5 and 3.0 T, respectively.…”

“…Image quality was visually assessed in regard to signal-tonoise ratio, blurring, spatial resolution and contrast; again a 5-grade quality score was used [13,15]. Figure 2 provides an example of good image quality.…”

“…Joint effusion was defined as abnormal presence of fluid (greater than 7 mm in thickness) within the joint as described by Lee et al [15]. ALVAL was defined as a soft tissue mass or fluid-filled cavity with thickened low intensity capsule in the periarticular region with joint effusion bursitis and possible remodeling of the adjacent bone as previously described [16].…”

“…However, with the increasing use of 3.0 T magnetic field strength for musculoskeletal imaging applications, several studies have also aimed at showing feasibility of these techniques at 3.0 T [13,14]. Two previous studies have demonstrated that effective metal artifact reduction was possible at both 1.5 and 3.0 T, but it was performed in vitro using animal specimens [14,15]; however, to the best of our knowledge to date no study was published directly comparing MAVRIC imaging at 1.5 and 3.0 T in vivo in the same patients with hip prosthesis.…”