3D-multi-spectral T2 mapping near metal implants

Abstract

Purpose: Due to host-mediated adverse reaction to metallic debris, there is an increasing need for noninvasive assessment of the soft tissue surrounding large joint arthroplasties. Quantitative $T_2$ mapping can be beneficial for tissue characterization and early diagnosis of tissue pathology but current $T_2$ mapping techniques lack the capability to image near metal hardware. A novel multi-spectral $T_2$ mapping technique is proposed to address this unmet need.

Methods: A $T_2$ mapping pulse sequence based on routinely implemented 3D multi-spectral imaging (3D-MSI) pulse sequences is described and demonstrated. The 3D-MSI pulse sequence is altered to acquire images at 2 echo times. Phantom and knee experiments were performed to assess the quantitative capabilities of the sequence in comparison to a commercially available $T_2$ mapping sequence. The technique was demonstrated for use within a clinical protocol in 2 total hip arthroplasty (THA) cases to assess $T_2$ variations within the periprosthetic joint space.

Results: The proposed multi-spectral $T_2$ mapping technique agreed, within experimental errors, with $T_2$ values derived from a commercially available clinical standard of care $T_2$ mapping sequence. The same level of agreement was observed in quantitative phantoms and in vivo experiments. In THA cases, the method was able to assess variations of $T_2$ within the synovial envelope immediately adjacent to implant interfaces.

Conclusions: The proposed 3D-MSI $T_2$ mapping sequence was successfully demonstrated in assessing tissue $T_2$ variations near metal implants.

Keywords: ${\text{T}}_2$ mapping; metal implants; multi-spectral imaging.