Comparison of MRI and computed tomography in the various stages of plasma cell disorders: correlations with biological and histological findings. Myélome-Midi-Pyrénées Group.

OBJECTIVE: Our study had a double aim: (i) to evaluate the sensitivity and the specificity of computed tomography (CT) and magnetic resonance imaging (MRI) in the different stages of plasma cell disorders, and (ii) to correlate CT and MRI with the biological, cytological and histomorphometric parameters.
METHODS: Twenty-four patients with MGUS according to Kyle, 12 patients with stage 1 and 12 with stage 3 myeloma, and 30 age-matched controls underwent MRI (sagittal views of the spine and coronal views of pelvis and femurs), CT (axial views from T10 to L5, sacrum, iliac crests), a histomorphometric study, determination of plasmocyte infiltration, and measurement of paraprotein, B2-microglobulin, the ca/cr ratio and osteocalcin.
RESULTS: Heterogeneous osteopenia with microlacunae seen on CT scan and diffuse decreased signal intensity which remained higher than the signal of the intervertebral disk on T1 weighted sequences (MRI) were not peculiar to myeloma. Lacunae larger than 5 mm with trabecular disruption observed on CT, diffuse decreased signal intensity lower than the disk signal, and a multinodular appearance on MRI, not seen in the controls or in patients with MGUS, were observed in all stage 3 myeloma and in 40% of stage 1 myeloma patients. MGUS and stage 1 myeloma patients with abnormal MRI had a higher monoclonal component, plasma cell percentage and hypercellular bone marrow than those with normal MRI findings. MGUS or stage 1 myeloma patients with abnormal CT had a lower trabecular bone volume than those with normal CT.
CONCLUSIONS: CT and MRI both reveal specific lesions in 40% of stage 1 myeloma patients. These methods are thus complementary in bone and bone marrow studies in myeloma.