Purpose The midventilation (midV) approach can be used to take respiratory-induced pancreatic tumor motion into account during radiation therapy. In this study, the dosimetric consequences for organs at risk and tumor coverage of using a midV approach compared with using an internal target volume (ITV) were investigated. Methods and Materials For each of the 18 patients, 2 treatment plans (25 × 2.0 Gy) were created, 1 using an ITV and 1 using a midV approach. The midV dose distribution was blurred using the respiratory-induced motion from 4-dimensional computed tomography. The resulting planning target volume (PTV) coverage for this blurred dose distribution was analyzed; PTV coverage was required to be at least V<inf>95%</inf> >98%. In addition, the change in PTV size and the changes in V<inf>10Gy</inf>, V<inf>20Gy</inf>, V<inf>30Gy</inf>, V<inf>40Gy</inf>, D<inf>mean</inf> and D<inf>2cc</inf> for the stomach and for the duodenum were analyzed; differences were tested for significance using the Wilcoxon signed-rank test. Results Using a midV approach resulted in sufficient target coverage. A highly significant PTV size reduction of 13.9% (P<.001) was observed. Also, all dose parameters for the stomach and duodenum, except the D<inf>2cc</inf> of the duodenum, improved significantly (P≤.002). Conclusions By using the midV approach to account for respiratory-induced tumor motion, a significant PTV reduction and significant dose reductions to the stomach and to the duodenum can be achieved when irradiating pancreatic tumors.
|Journal||International Journal of Radiation Oncology Biology Physics|
|Publication status||Published - 2015|