3D-multi-spectral T mapping near metal implants.

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 multispectral 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.