MRI-based Zero Echo Time and Black Bone Pseudo-CT Compared with Whole-Body CT to Detect Osteolytic Lesions in Multiple Myeloma

Background MRI is highly sensitive for assessing bone marrow involvement in multiple myeloma (MM) but does not enable detection of osteolysis. Purpose To assess the diagnostic accuracy, repeatability, and reproducibility of pseudo-CT MRI sequences (zero echo time [ZTE], gradient-echo black bone [BB]) in detecting osteolytic lesions in MM using whole-body CT as the reference standard. Materials and Methods In this prospective study, consecutive patients were enrolled in our academic hospital between June 2021 and December 2022. Inclusion criteria were newly diagnosed MM, monoclonal gammopathy of undetermined significance at high risk for MM, or suspicion of progressive MM. Participants underwent ZTE and BB sequences covering the lumbar spine, pelvis, and proximal femurs as part of 3-T whole-body MRI examinations, as well as clinically indicated fluorine 18 fluorodeoxyglucose PET/CT examination within 1 month that included optimized whole-body CT. Ten bone regions and two scores (categorical score = presence/absence of osteolytic lesion; semiquantitative score = osteolytic lesion count) were assessed by three radiologists (two experienced and one unfamiliar with pseudo-CT reading) on the ZTE, BB, and whole-body CT images. The accuracy, repeatability, and reproducibility of categorical scores (according to Gwet agreement coefficients AC1 and AC2) and differences in semiquantitative scores were assessed at the per-sequence, per-region, and per-patient levels. Results A total of 47 participants (mean age, 67 years ± 11 [SD]; 27 male) were included. In experienced readers, BB and ZTE had the same high accuracy (98%) in the per-patient analysis, while BB accuracy ranged 83%-100% and ZTE accuracy ranged 74%-94% in the per-region analysis. An increase of false-negative (FN) findings in the spine ranging from +17% up to +23%, according to the lumbar vertebra, was observed using ZTE (