Imaging assessment plays a critical role in management of pediatric MSK diseases. Cross sectional imaging is often the initial modality of assessment of several MSK malignancies and benign MSK conditions in pediatric patients. However, over the last two decades, hybrid imaging methods that combine data provided by physiologic molecular imaging with conventional anatomic imaging modalities such as PET/CT and PET/MRI have emerged as critical tools that enhance clinical management of patients by enabling rapid and early detection and better characterization of disease as well as treatment related changes. Hybrid imaging, by providing metabolic insight into the cellular processes, and by allowing assessment of whole body, allows for assessment of not only the primary lesion, but also other known or suspected occult sites of disease. There are several FDA approved PET radiotracers, but FDG, a radioactive analogue of glucose, is the most used FDA approved clinically available tracer in assessment of pediatric MSK diseases. While high FDG uptake signifies higher cellular metabolism and is therefore noted in several malignancies, it can also be seen in a variety of non-malignant conditions such as inflammation. As such, complimentary information with combined PET/CT or PET/MRI can better characterize lesions and add specificity to imaging assessment.

Hybrid imaging has been proven to be useful in initial assessment of disease, staging and treatment monitoring, and compliments the assessment by Response Evaluation Criteria in Solid Tumors (RECIST). The feasibility and value of PET imaging in combination with CT or MRI has been shown in staging, restaging and assessment of treatment response in several malignancies as well as in evaluation of benign diseases. We discuss below in more detail, the technical aspects and role PET/CT and PET/MRI in some common benign and malignant pediatric MSK diseases.