Comparative Evaluation of MRI and MDCT for the Detection of Metastic Pulmonary Nodules

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.

Recently, Magnetic Resonance Imaging (MRI) of the lung has been shown to be a feasible alternative to CT for the detection of pulmonary metastases in adults with sensitivities and specificities of over 90% for the detection of nodules 5mm or larger. It has also shown promise in the characterization of nodules as benign or malignant. Since MRI does not involve radiation, it may prove to be a preferable imaging technique for children. We wish to evaluate the potential for MRI to complement or even replace CT in the imaging of pulmonary metastatic disease in children.