The use of magnetic resonance imaging in the diagnosis and followup of pediatric pelvic rhabdomyosarcoma

Purpose: Previous radiological descriptions of pelvic rhabdomyosarcoma emph asized ultrasonography and computerized tomography (CT). Few reports are av ailable on the use of magnetic resonance imaging (MRI) for diagnosing and f ollowing pelvic rhabdomyosarcoma. We retrospectively compared MRI to CT for diagnosing and following children with pelvic rhabdomyosarcoma. Materials and Methods: We treated 4 boys and 3 girls for pelvic rhabdomyosa rcoma. Initial and followup evaluations included pelvic CT and MRI at inter vals determined by treatment and disease status. We retrospectively reviewe d the clinical charts and imaging studies of these patients. The initial ra diological report was evaluated and then 1 radiologist reviewed all studies . Attention was directed toward identifying lesions revealed by CT or MRI b ut not by the other modality. Results: MRI detected all lesions shown by CT. On the other hand, MRI detec ted residual disease in 1 case that was not demonstrated by CT. In 2 other patients MRI was superior to CT for delineating the local extent of disease , especially urethral involvement. Conclusions: Compared with CT, MRI improves the detection of residual pelvi c rhabdomyosarcoma. Tissue planes are well delineated, allowing more accura te assessment of tumor invasion into adjacent structures. MRI is the imagin g modality of choice for following pediatric patients with pelvic rhabdomyo sarcoma.