Radiation Exposure in Patients Undergoing VEPTR Treatment for Thoracic Insufficiency Syndrome

1. Radiation Exposure in Patients Undergoing VEPTR Treatment for Thoracic Insufficiency Syndrome Derek Khorsand1, Jonathan Swanson, MD 2, Kit Song, MD3 1 University of Washington School of Medicine, 2Department of Orthopedics and Sports Medicine, Seattle Children’s Hospital and Regional Medical Center, 3Department of Radiology, Seattle Children’s Hospital and Regional Medical Center Introduction Children with Thoracic insufficiency syndrome (TIS) undergo extensive evaluations to characterize their deformity and subsequent respiratory impacts. This study quantifies total ionizing radiation exposure, in units of millisieverts (mSv), to these children during the course of their treatment with a Vertically Expandable Prosthetic Titanium Rib (VEPTR), a device to correct spinal deformity for patients with TIS. Summary The 62 children had a total of 447 procedures. There were a total of 290 CT scans, 4293 xrays, 147 MRI scans, and 134 V/Q scans. Average radiation exposure up to initial surgery was 13 mSv. The average exposure/epoch for subsequent surgical treatments was 3.16 mSv (0.4 to 19.0 mSv). CT scans accounted for 70% of total radiation per patient throughout the entirety of care • Methods • Cases reviewed from 62 children who had VEPTR surgical treatment for TIS at our center from 2001-2011. • All X-rays, CT scans, nuclear medicine studies, fluoroscopic evaluation, and MRI related to treatment for all patients were reviewed. • Epochs of treatment were time of initial evaluation to end of initial surgery and each subsequent epoch was marked by another surgical intervention. • Radiation exposure from plain radiographs and V/Q scans were calculated from reference values and applied to each study. • Direct radiation exposure for CTs since 2007 was calculated and reported as mSv using the method of Allesio and Phillips from the variables of dose length product (DLP), kilovoltage peak (KVP), phantom, and age at time of study. • An average of spine/chest/pelvis CTs from 2007-2011 was used to estimate radiation exposure for scans before 2007. • Fluoroscopy exposures were directly calculated from the dose area product (DAP) multiplied by the conversion factor 0.2 mSv per Gy cm2. • Conclusions • Average yearly background radiation exposure in the United States is 3.6 mSv/ year. • Mean exposure prior to any surgery: 13mSv • After initial implantation, exposure was 6 mSv/year with an average of 2 surgeries/year • CT scans account for 70% of radiation exposure in this cohort of patients. • The results of this study suggest the need to consider the quantity and type of imaging studies used to characterize thoracic deformities over the course of treatment with a VEPTR device. Acknowledgements The authors would like to thank the University of Washington School of Medicine Medical Student Summer Research Training Program as well as the Seattle Children’s Hospital and Regional Medical Center Department of Orthopedics and Sports Medicine Staheli Fund for their support of this project.