Evaluation of PET/MR and PET/CT Imaging for Bone Marrow Lesions

Overview

Developing an MRI protocol at 1.5 T allowing quantification of the hematopoietic, fatty and trabecular moieties of marrow. An ideal protocol would differentiate red marrow from neoplastic cellular infiltration, and detect loss of trabecular bone. This study assesses the feasibility of a multiple gradient echo sequence for differentiation of water and fat constituents of marrow, combined with T2\* mapping to interrogate the trabecular component The investigators hypothesize that these techniques will allow better identification of lesion type than routine MR sequences, and can be used to quantitatively characterize myelomatous marrow replacement, with iliac crest biopsy (which is routinely performed in the diagnosis of myeloma) as gold standard. Fluoro-deoxyglucose (FDG)/PET CT imaging can detect FDG uptake in active myeloma and is obtained routinely for certain cohorts of patients with myeloma. PET/CT is commonly used in both initial whole body assessment and in monitoring remission. PET has been found to be about 59% sensitive and 75% specific for detection of myeloma . Myelomatous lesions are detected on MRI by the replacement of marrow fat. Routine MRI however is limited by scope/field of view, usually evaluating marrow in a single anatomic region (such as an extremity, the pelvis or spine). To assess the diffuse marrow involvement in MM, whole body MRI imaging potentiates near global assessment of the marrow, which aids in evaluating tumor burden, and may be useful in staging.

Imaging of the pelvis and bilateral femora at 1.5 Tesla in a 30 minute research time "slots" at NYU-FPO MRI, Tisch Hospital, NYU Medical Center, Department of Radiology, HCC basement. This protocol utilizes routine, Dixon sequences and multi-echo MR "spectroscopic" sequences, allowing quantization of the fat water and trabecular moieties of marrow. The opposed phase portion of a Dixon sequence can aid differentiation between dense red marrow and a metastatic deposits by assaying for intravoxel fat. Diffusion sequences may also potentially improve specificity by assessing mobility of water in hypercellular and hypocellular portions of marrow, and will be added to the protocol if scan time permits. The new sequences conform to FDA safety regulations regarding static magnetic field, time varying magnetic fields, specific absorption rate, and acoustic noise levels. However, since they have not been fully validated for diagnostic accuracy, the resulting images will be analyzed for research purposes only and will not be used in the patient's diagnostic assessment.