Children with sarcomas are routinely assessed with a variety of imaging techniques that involve the use of ionizing radiation. These include computed tomography (CT), nuclear bone scan, and positron emission tomography-CT (PET-CT). Pediatric sarcoma patients undergo many imaging studies at the time of diagnosis, during therapy and for years following completion of therapy. Because children are in a stage of rapid growth, their tissues and organs are more susceptible to the harmful effects of ionizing radiation than are adults. Furthermore, compared to adults, children have a longer life expectancy and, therefore, a longer period of time in which to develop the adverse sequelae of radiation exposure, such as the development of second malignancies.
Alternative experimental methods of measuring tumor response will be compared to current standard of care measures to determine if the experimental method is equivalent to methods currently being used. Investigators wish to determine if they can reduce patient's exposure to the harmful effects of ionizing radiation by replacing imaging studies that use radiation with whole body diffusion weighted magnetic resonance imaging (DW-MRI) which does not use any radiation. They also want to know if DW-MRI measurements of the tumor can tell how well the tumor is responding to therapy. There have been studies in adults with cancer that have shown that DW-MRI provides useful information about how tumors are responding to therapy. There have only been very small studies of DW-MRI in children with tumors in the body. Therefore, the role of DW-MRI in pediatric sarcoma patients is not yet known and it is still experimental. This study might give us important information that could help us treat other children with bone or soft tissue sarcomas in the future.