Whole-Body Diffusion-Weighted Imaging in Chronic Recurrent Multifocal Osteomyelitis in Children

Abstract

Objective: Chronic recurrent multifocal osteomyelitis/ chronic non-bacterial osteomyelitis (CRMO/ CNO) is a rare auto-inflammatory disease and typically manifests in terms of musculoskeletal pain. Because of a high frequency of musculoskeletal disorders in children/ adolescents, it can be quite challenging to distinguish CRMO/ CNO from nonspecific musculoskeletal pain or from malignancies. The purpose of this study was to evaluate the visibility of CRMO lesions in a whole-body diffusion-weighted imaging (WB-DWI) technique and its potential clinical value to better characterize MR-visible lesions.

Material and methods: Whole-body imaging at 3T was performed in 16 patients (average: 13 years) with confirmed CRMO. The protocol included 2D Short Tau Inversion Recovery (STIR) imaging in coronal and axial orientation as well as diffusion-weighted imaging in axial orientation. Visibility of lesions in DWI and STIR was evaluated by two readers in consensus. The apparent diffusion coefficient (ADC) was measured for every lesion and corresponding reference locations.

Results: A total of 33 lesions (on average 2 per patient) visible in STIR and DWI images (b = 800 s/mm2 and ADC maps) were included, predominantly located in the long bones. With a mean value of 1283 mm2/s in lesions, the ADC was significantly higher than in corresponding reference regions (782 mm2/s). By calculating the ratio (lesion to reference), 82% of all lesions showed a relative signal increase of 10% or higher and 76% (25 lesions) showed a signal increase of more than 15%. The median relative signal increase was 69%.

Conclusion: This study shows that WB-DWI can be reliably performed in children at 3T and predominantly, the ADC values were substantially elevated in CRMO lesions. WB-DWI in conjunction with clinical data is seen as a promising technique to distinguish benign inflammatory processes (in terms of increased ADC values) from particular malignancies.

Fig 1. MR images of 12-year old girl with known CRMO.

a) STIR-weighted images show diaphyseal edematous bone marrow involvement, periostal reaction of the left humerus b) axial series showing large and homogenous bony involvement c) signal alteration in DWI b = 800 images d) ADC increase at the corresponding site.

Fig 2. “At-a-glance” visualisation of Whole-body-DWI.

Intuitive visualisation of Whole-body-DWI with maximum intensity projection MIP in a 12-year-old girl with multifocal CRMO manifestations shows signal alterations on DWI in the left pelvis (Os ilium) and in the right ankle/ distal tibia.

Fig 3. Multiparametric MRI.

a) contrast-enhancement of a CRMO-lesion in the right Os ilium on axial T1-TSE FS b) corresponding signal alteration on STIR images c) correlating signal changes on axial DWI b800 d) and high signal intensity on ADC.

Fig 4. Box-Plot of ADC values.

Increased ADC in CRMO-lesions compared to the corresponding reference regions. Since bone marrow cellularity is highly dependent form lesion location and other individual clinical factors, absolute ADC values both in affected and normal bone varied substantially, which made the recommendation of a generalized threshold impossible.