Radiation exposure of young patients with abdominal neuroblastoma from therapeutic and imaging procedures: a phantom study.

This study calculated the radiation dose to young patients with high-risk abdominal neuroblastoma from therapeutic and imaging procedures. Computational XCAT phantoms representing typical patients aged 5-15 years were used. Intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) plans were generated with 6 MV photons for a planning target volume (PTV) on the left and right abdominal side. Dose-volume-histograms from the plans were used to find the average dose (D) to critical normal abdominal and thoracic organs. The imaging dose to these organs and PTV was calculated by simulating kV cone-beam computed tomography (CBCT) scanning for patient setup before radiotherapy. Different CBCT protocols were simulated with Monte Carlo methods. The IMRT and VMAT plans provided similar PTV coverage and organ sparing. For a 21.6 Gy target dose, the D of the abdominal organs from the treatment plans was 3.6-19.6 Gy and that of thoracic organs was 0.1-2.3 Gy. Daily CBCT scans on 15-year-old patients with the standard adult protocol gave total PTV and organ doses of 95.3-485.3 mGy. The doses from the modified standard protocol for 5- and 10-year-old patients were 74.2-159.6 mGy. The dose calculations with a specially designed CBCT protocol for patients up to 10 years were 6.0-27.8 mGy. The total imaging dose to the PTV was up to 2.2% of the delivered therapeutic dose. The replacement of the modified adult CBCT protocol with a special protocol solely defined for children reduced the radiation dose to target and normal organs by more than five times.