A new pencil beam model for photon dose calculations

The pencil beam method has been frequently used for dose calculations in intensity modulated radiation therapy (IMRT). In this work, a new pencil model is proposed for photon dose calculations in the heterogeneous media. To avoid the bias caused by oblique kernels and reduce the computation time, the dose distributions are calculated in a spherical coordinate system with pencil kernels of the different source to surface distance (SSD). To...