Diffusion-weighted MRI of bone marrow oedema,soft tissue oedema and synovitis in paediatric patients: feasibility and initial experience

Background: mri has become the mainstay of diagnostic imaging in paediatric rheumatology for lesion detection,differential diagnosis and therapy surveillance. mr imaging of synovitis,in particular,is indispensable for early diagnosis and follow-up in arthritis patients. we used diffusion-weighted mri (dwi) as a new imaging modality in comparison to standard mri sequences to study bone marrow oedema,soft-tissue oedema and synovitis in paediatric patients.methods: a total of 52 patients (mean age 11 ± 5 years) with bone marrow oedema (n = 31),soft-tissue oedema (n = 20) and synovitis (n = 15) were examined with transversal diffusion-weighted single-shot echoplanar imaging in addition to standard mr sequences (t2w tirm,t1w pre- and post-contrast). diffusion-weighted images were used for lesion detection and apparent diffusion coefficient (adc,unit × 10-3 mm2/s) values were measured with roi technique on adc maps.results: in 50 of 52 patients,dwi delineated the lesion of interest corresponding to pathological signal increase on standard sequences. mean adc was 1.60 ± 0.14 (range 1.38 - 1.99) in osseous lesions,1.72 ± 0.31 (range 1.43 - 2.56) in soft tissue oedema and 2.82 ± 0.24 (range 2.47 - 3.18) for joint effusion (anova p < 0.001). no significant difference in mean adc was seen for inflammatory vs. non-inflammatory lesions. relative signal intensity of oedema was similar for dwi and t2w tirm. dwi visualised synovial restricted diffusion with a mean adc of 2.12 ± 0.45 in 12 of 15 patients with synovitis.conclusions: diffusion-weighted mri reliably visualises osseous and soft tissue oedema,as compared to standard sequences. dwi of synovitis is feasible in large joints and presents a novel approach to contrast-free imaging of synovitis. whole-body dwi for chronic non-bacterial osteomyelitis should be evaluated in future studies. © 2012 neubauer et al.; licensee biomed central ltd.