Quantitative Bone Marrow MRI in Children with Acute Lymphoblastic Leukemia

The aim of this study was to evaluate, using MRI, the changes in bone marrow fat fraction (BMFF) of patients with acute lymphoblastic leukemia (ALL), in comparison with children without hematological disorders. Methods and Results: The cohort of the study subjects included 20 patients aged between 5 and 17 years (mean age of 11.2±3.6 years; 10 boys and 10 girls) with clinically and morphologically confirmed diagnosis of ALL All patients underwent MRI scanning in the acute phase of the disease before the start of specific therapy. Then, the study was repeated in 10 patients (mean age of 12.2±2.3 years; 8 boys and 2 girls) during treatment, according to the ALL-MB 2015 protocol for patients with primary ALL and according to the ALL-REZ-MB 2016 protocol for patients with relapsed ALL. The control group consisted of 24 healthy controls of the same age group (mean age of 12±2.8; 17 boys and 7 girls) with no prior hematologic diseases. MRI scanning was carried out using a Philips Achieva dStream 3T scanner with a 32-channel FlexCoverage abdominal receiving coil. The MRI protocol included images obtained with the mDIXON Quant technique in the coronal plane, completely covering the pelvic bones and lumbar spine. Fat fraction (FF) maps were generated automatically on the MRI console using the 7-peak fat model and were corrected for T2* effects. Regions of interest (ROI) measuring 150 mm2 were placed in the bodies of the left and right iliac bones (Ilium L, Ilium R) as well as in the L4 and L5 vertebral bodies, taking care to avoid blood vessels, cortical bones and areas that could potentially contain artifacts. In the group of healthy controls, BMFF value was 51%±11% in the bodies of the iliac bones and 32%±10% in the lumbar vertebrae. In the group of patients with the acute phase of the disease, BMFF was as low as 3.1%±2.6% in all the bone structures. In patients who had undergone chemotherapy, the mean BMFF increased up to 77%±7% in the iliac bones and up to 65%±13% in the vertebrae. Student's t-test for dependent samples revealed a statistically significant increase in the mean BMFF values in all the bone structures after chemotherapy (P<0.01). After specific therapy, BMFF was also significantly higher than under normal conditions (P<0.01). Conclusion: This study provides important diagnostic information for various phases of ALL treatment, especially in suspected cases of resistant or recurrent disease.