Pre-treatment MRI of leukaemia and lymphoma in children: are there differences in marrow replacement patterns on T1-weighted images?

OBJECTIVES: To investigate the prevalence and distribution of specific marrow patterns on pre-treatment magnetic resonance imaging (MRI) examinations in children with leukaemia and lymphoma and with respect to the anatomic location. MATERIALS AND METHODS: This retrospective IRB-approved and HIPAA-compliant study included children with leukaemia or lymphoma who underwent pre-treatment MRI examinations over 18 years (between 1 January 1995 and 31 August 2013). Two radiologists blinded to the clinical diagnosis reviewed each study to determine the presence or absence of abnormal marrow signal and, when present, sub-categorised the pattern into diffuse, patchy, or focal abnormal marrow. Chi-square and Fisher's exact tests were used to compare marrow patterns between leukaemia and lymphoma. RESULTS: The study included 50 children (32 males and 18 females; mean age 9.5 ± 5.3 years) with 54 MRI examinations (27 leukaemia and 27 lymphoma) that included 26 spine and 28 non-spine studies. Marrow replacement was present on 43 (80%) studies, significantly more common with leukaemia than with lymphoma (p = 0.039). The diffuse replacement pattern was significantly more common with leukaemia when compared to lymphoma (p < 0.001) and the focal pattern was only observed with lymphoma. In the spine, the diffuse pattern was observed with lymphoma (3/14, 21%). All patients with leukaemia and MRI outside of the spine showed marrow involvement. CONCLUSION: Marrow replacement is common on MRI from children with leukaemia and lymphoma. A diffuse pattern was significantly associated with leukaemia on studies outside of the spine and a focal pattern was only observed with lymphoma, independently of the anatomic location. KEY POINTS: • Bone marrow replacement on pre-treatment MRI examinations in children with leukaemia and lymphoma was observed in 93% (25/27) and 67% (18/27), respectively. • Diffuse pattern of marrow replacement was significantly more common in leukaemia even though this pattern was also observed with lymphoma on the spine MRI studies. • Focal pattern of marrow replacement was present only with lymphoma and not with leukaemia regardless of the anatomic location.