Lymphomas are common malignancies in children [1]. Lymphomas account for about 5% to 6% of all malignancies [2] and include a number of different pathologic subtypes, which arise from the constituent cells of the immune system or from their precursor, lymphoma is now highly treatable. Imaging plays a major role in diagnosis, staging and response making surgical staging unnecessary in most cases [3].~The treatment regimen and the prognosis depend on the morphological type of lymphoma and the disease stage [4].~PET/CT using (18F) FDG is considered one of the functional imaging techniques used to assess the glucose metabolism in vivo; its use has been widely increased in evaluation of oncology patients being highly sensitive in assessment of malignancy as PET/CT can detect malignancy prior to morphological change[5].~Imaging by PET is vastly improved by combining it with CT technology. FDG-PET and CT provide functional and anatomic information, respectively. Integration of both modalities can compensate for the disadvantages of each, and the combination method outperforms , thus PET CT has a proved role for Lymphoma in adult [6].~F-FDG PET/CT is now considered the most accurate imaging modality in the management of adult lymphomas. Its value has been well documented for initial staging, at mid chemotherapy, after the end of therapy, and for assessing tumor recurrence in the follow-up [7,8].~Diagnostic information obtained from 18F-FDG PET scans changed management in 24% of pediatric oncology patients, including those with lymphoma [9].~The sensitivities of FDG-PET for the detection of nodal and extra nodal lesions of lymphoma are 92-100 and 74-78% [10].~The formation of multiple lymph node lesions in distant sites is one of the characteristics differentiating this disease from lymph node metastasis of common cancer, and thus the fact that FDG-PET allows whole-body scanning is a strong point in its favor.[11].~Ultrasonography is an imaging modality that is favored worldwide because of its precision, portability, practicality, and cost. The use of this technology to distinguish metastatic from benign cervical lymph nodes, this determination has implications for diagnosis, staging, and determining optimal treatment regimens [12].~Lymph node enlargement is a common feature of various benign and malignant disorders. It is well recognised that ultrasound is superior to palpation in detecting and characterising subcutaneous lymph nodes, various sonographic modalities can be used for lymph node evaluation, including gray-scale, color Doppler [13].~Nodal sonographic features can offer a clue for whether a lymph node contains cancer. Ultrasound provides detailed information about the internal and external features of a lymph node and demonstrates superior sensitivity and specificity in detecting malignant nodes compared with physical examination [14].~With the use of color Doppler sonography, the vasculature of the lymph nodes can also be evaluated which provides additional information about the nodes. It has become an effective way to obtain more information about the examined lymph nodes with no appreciable increase in the duration or invasiveness of the examination [15].
To evaluate the accuracy of different sonographic modalities vs PET/CT in assessment of response to therapy in lymphoma patients: both early and late therapeutic response assessment.~To evaluate whether imaging features of pathologic lymph nodes on PET/CT and ultrasonography have a predictive role before, during and after treatment in comparison to clinical outcome.