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

Abstract

BackgroundMRI 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.MethodsA 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.ResultsIn 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.ConclusionsDiffusion-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.

Intravoxel incoherent motion magnetic resonance imaging of the knee joint in children with juvenile idiopathic arthritis

“…Although the underlying pathophysiological mechanism for these findings is not clarified, several studies observed high synovial signal indicating arthritis in small and large joints [9][10][11][12][13]. Some researchers noted high signal of joint effusion on diffusionweighted scans, which may be attributed to T2 shine-through artefact or to truly increased signal arising from restricted motion of water molecules by macromolecules [12,13].…”

“…The sequences are generally signal-starved, and the synovial layer, even in the presence of active synovitis, rarely exceeds 3 mm in thickness in the knee joint of children and adolescents with juvenile idiopathic arthritis. In contrast, in-plane spatial resolution is practically limited to the range of 1×1 mm 2 to 1.5×1.5 mm 2 [9,12,13].…”

“…In 2009, Agarwal et al [8] first described altered diffusivity and anisotropy in the inflamed synovia of adults with rheumatic arthritis. In 2012, we proposed diffusion-weighted MR imaging (DWI) as a new technique for gadolinium-free imaging of synovitis in children [9]. Since then, synovial imaging with DWI has been explored in adults and children with arthritis of small and large joints [10][11][12].…”

Autoinflammatory bone disorders

“…MRI is especially sensitive in detecting bone edema during the early stages of inflammation, before bone erosions and/or sclerosis can be detected, and in displaying adjacent inflammatory reactions, e.g. periostitis or synovitis [24]. Although the use of contrast agents can be helpful in the initial assessment of ambiguous bone lesions, nonenhanced sequences may be sufficient for follow-up imaging in CNO patients [23].…”

Novel Imaging Techniques in Rheumatic Diseases

“…In juvenile idiopathic arthritis (JIA), research into DWI had been conducted in the knee joint [44][45][46][47] and the sacroiliac (SI) joints. 48,49 In the SI joints of patients with enthesis-related arthritis, normalized ADC values (calculated as ADC of the linear ROI over SI joints/by ADC of reference ROI in normal sacral bone) were significantly higher (2.57) than in controls with mechanical lower back pain (1.28).…”