Whole-body MRI in children with Langerhans cell histiocytosis for the evaluation of the skeletal system

Purpose: The usefulness of whole-body MRI (WB-MRI) for the detection of skeletal lesions in patients with Langerhans cell histiocytosis should be documented on the basis of case presentations. Materials and Methods: In six patients with histologically proven Langerhans cell histiocytosis, 14 WB-MRI examinations were performed to evaluate the skeletal system within disease staging (6 primary, 8 follow-up examinations). The examinations were performed on a 1.5 Tesla, 32-channel whole-body scanner. The examination protocol consisted of T1-weighted and STIR sequences in coronal and sagittal orientation. For comparison, radiographs of the initial skeletal lesions and those that were additionally detected on WB-MRI were available. Results: In 4 patients no additional skeletal lesions were found on WB-MRI besides the initial lesion leading to the diagnosis of unifocal single system disease. In 2 patients WB-MRI was able to identify additional skeletal lesions. In a 51/2 year-old boy with the primary lesion located in the cervical spine, a second lesion was detected in the lumbar spine on the initial scan and in the skull and proximal femur during follow-up examination. In a 12 year-old girl with a primary lesion of the thoracic spine, WB-MRI diagnosed additional lesions in the pelvic bone and the tibia. In both patients the diagnosis of multifocal skeletal involvement led to chemotherapy. During follow-up examination, the healing response under therapy could be demonstrated. Comparison with conventional imaging showed that especially lesions located in the spine or the pelvis were not detectable on radiographs even when knowing the MR results. Conclusion: The extent of skeletal involvement in Langerhans cell histiocytosis has crucial impact on therapy and prognosis. Whole-body MRI has been reported to be an established method for the evaluation of disseminated skeletal disease with distinct advantages over conventional radiography and bone scintigraphy. Our results suggest that WB-MRI should also be the imaging modality of choice for the assessment of skeletal involvement in children with Langerhans cell histiocytosis.