Applicability of 3T body MRI in assessment of nonfocal bone marrow involvement of hematopoietic neoplasia in dogs

Background: The utility of whole body magnetic resonance imaging (MRI) in detecting bone marrow infiltration in dogs with cancer has not been investigated. Objectives: To assess the feasibility of 3T body MRI for bone marrow assessment in dogs with hematopoietic neoplasia. Animals: Seven dogs with B-cell lymphoma, 3 dogs with myelodysplastic syndrome (MDS), and 2 clinically normal dogs. Methods: A prospective study of dogs with hematopoetic cancer was conducted using T1W, T2W, In-Phase, Out-of-Phase and STIR pulse sequences of the body excluding the head prior to bone marrow sampling. The relative signal intensity of a midlumbar vertebral body and a midshaft femoral bone marrow was compared by visual and point region of interest analysis to regional skeletal muscle. Results: Similarity of femoral diaphyseal and vertebral body marrow signal intensity to that of skeletal muscle on the Out-of-Phase sequence was useful in distinguishing the 3 dogs with hypercellular marrow because of MDS from the 7 dogs with B-cell lymphoma and from the 2 clinically normal dogs. 1/7 dogs with lymphoma had proven bone marrow involvement but normal cellularity and less than 5% abnormal cells. Unaffected midfemoral marrow had greater signal intensity than skeletal muscle and unaffected vertebral marrow had less signal intensity than skeletal muscle on the Out-of-Phase sequence. Conclusions and Clinical Importance: 3T, Out-of-Phase MR pulse sequence was useful in distinguishing diffuse bone marrow infiltrate (MDS) from minimally or unaffected marrow using skeletal muscle for signal intensity comparison on whole body MRI.