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 multiacquisition variable-resonance image combination, slice encoding for metal artifact correction (MAVRIC-SEMAC) hybrid sequence (MAVRIC-SL) compared to standard sequences at 1.5T and 3T in porcine knee specimens with metal hardware.

Materials and 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 magnetic resonance imaging (MRI) with MAVRIC-SL PD and short T1 inversion recovery (STIR), standard fast spin echo (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 receiver operating characteristic (ROC). Artifact length and width were measured.

Results: Metal artifact sizes were largest in the presence of steel screws at 3T (FSE T2 FS: 28.7 cm(2) ) and 1.5T (16.03 cm(2) ). MAVRIC-SL PD and STIR reduced artifact sizes at both 3T (1.43 cm(2) ; 2.46 cm(2) ) and 1.5T (1.16 cm(2) ; 1.59 cm(2) ) compared to FS T2 FSE sequences (27.57 cm(2) ; 13.20 cm(2) ). 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 vs. T2 -STIR: 0.78 [P = 0.001] and vs. 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, although metal artifacts at 3T were larger. J. Magn. Reson. Imaging 2015;41:1291-1299. © 2014 Wiley Periodicals, Inc.

Keywords: MAVRIC-SL; artifact reduction; magnetic resonance imaging (MRI); periprosthetic imaging.

Figure 1

Chart illustrating the hardware placement scheme and the eight compartments defined surrounding the hardware placed. Compartments were defined as proximal/distal to the shaft screws and anterior/posterior to the screws placed at the femur condyles/tibia epiphysis. Black circles mark screw positions.

Figure 2

Pig knee specimen prepared with a titanium screw placed at the tibia epiphysis showing an artificially created cartilage lesion (short arrows) at the medial femoral condyle and a drill hole simulating a lytic bone lesion (long arrow) in the medial tibia plateau at two field strengths: 3T (top row) and 1.5T (bottom row). Sequences: 3T MAVRIC-SL PD (a), 3T FSE PD (b), 3T MAVRIC-SL STIR (c), 3T FSE STIR (d), 3T FSE T2 fs.(e) 1.5T MAVRIC-SL PD (f), 1.5T FSE PD (g), 1.5T MAVRIC-SL STIR (h), 1.5T FSE STIR (i), 1.5T FSE T2 fs (j)

Figure 3

Pig knee specimen demonstrating a cartilage lesion in the presence of metal artifacts caused by two steel screws placed at the tibia epiphysis and the femoral condyle imaged at 3T (top row) and 1.5T (bottom row). Sequences: Sequences: 3T MAVRIC-SL PD (a), 3T FSE PD (b), 3T MAVRIC-SL STIR (c), 3T FSE STIR (d), 3T FSE T2 fs.(e) 1.5T MAVRIC-SL PD (f), 1.5T FSE PD (g), 1.5T MAVRIC-SL STIR (h), 1.5T FSE STIR (i), 1.5T FSE T2 fs (j). Metal artifact areas are noticeably smaller in size in the MAVRIC-SL sequences (a,c,f,h) and visualization of the cartilage lesion is improved.

Figure 4

Average image quality grading for each individual sequence and field strength: subjective image quality parameters rated using a 4-level grading, where 1 is poor and 4 is excellent image quality/visualization of corresponding structure.

Figure 5

Pig knee specimen demonstrating bone drill hole lesions in the presence of steel screws placed at the tibia epiphysis and the femoral condyle imaged at 3T (top row) and at 1.5T (bottom row). Sequences: 3T MAVRIC-SL PD (a), 3T FSE PD (b), 3T MAVRIC-SL STIR (c), 3T FSE STIR (d), 3T FSE T2 fs.(e) 1.5T MAVRIC-SL PD (f), 1.5T FSE PD (g), 1.5T MAVRIC-SL STIR (h), 1.5T FSE STIR (i), 1.5T FSE T2 fs (j). Lesions are in part visualized in FSE STIR (d,i) and FSE PD (b,g) sequences (vertical arrows) and an additional lesion is only revealed with MAVRIC-SL (a,c,f,h) metal artifact suppression (horizontal arrows).