The gold standard for investigating the detection of pulmonary metastases is Multi-Detector Computed Tomography (MDCT). Computed Tomography (CT) is routinely used in the staging of pediatric patients with primary tumors which commonly metastasize to the lungs (with approximate percentage incidence of pulmonary metastases at presentation) are Ewing's sarcoma (15-20%), osteosarcoma (15-20%), Wilm's Tumor (10%), rhabdomyosarcoma (10%), and hepatoblastoma (10%). However, CT scanning has two central limitations. Firstly, it carries associated radiation risks. This risk is increased if multiple scans need to be performed during treatment and follow up. This is of particular concern in children who frequently have curable disease and may have years to live with the radiation risk. Secondly, CT is limited in its ability to distinguish between benign and malignant nodules.