18 F-FDG PET/MR Assessment of Pediatric Langerhans Cell Histiocytosis

Introduction Langerhans cell histiocytosis (LCH) is a histiocytic proliferative disease without a well-understood etiology. The aim of our study is to summarize the imaging features of PET/MR in children with LCH and to explore its diagnostic role in LCH. Methods Retrospective analysis was performed of the pretreatment PET/MR imaging data of 15 children with LCH. Comparison of ADC values was done between lesions and normal tissues. Results Of the fifteen patients enrolled, five had single-organ or single-system involvement, and ten had multiple-system involvement. Nine patients had varying degrees of bone destruction and increased FDG uptake, whereas thickening and deviation of the pituitary stalk and disappearance of the normal high-signal intensity of T1WI in the neurohypophysis were observed in the pituitary gland in six of them. Splenomegaly with diffuse increased FDG uptake or a normal spleen with increased FDG uptake was found in four cases, liver in three, multiple lymph node enlargement in three, pulmonary lesions in three, and increased metabolism in medullary cavity in two cases. Additionally, two cases involved the skin. Hypermetabolic nodules were detected in muscle in one case, thyroid involvement in one case, and a mediastinal lesion in one case. Conclusion PET/MR can show well the distribution of the organs, systems, and lesions involved in LCH and is of considerable significance in the systemic evaluation of LCH.