Organ at risk radiation dose analysis in nasopharyngeal cancer with analytical anisotropic algorithm (AAA) and pencil beam convolution (PBC): A comparative study

The Analytical Anisotropic Algorithm (AAA) and PBC (Pencil Beam Convolution) are dose calculation methods for tumors and Organ At Risk (OAR) as part of Treatment Planning System (TPS). The TPS aims to determine the angle geometry design, radiation energy, the amount of radiation field, accessories and dosimetry of patients who will be given treatment using radiation. However, there are healthy organs around nasopharyngeal cancer, which also receive the radiation. This healthy organs are the brainstem and spinal cord. This work aims to determine the dose received by the brainstem and spinal cord on AAA and PBC method. There are 5 data of the brainstem and spinal cord dose that are obtained from the AAA calculation method and 5 data are obtained from the PBC calculation method. The dose evaluation was done by analyzing the DVH (Dose Volume Histogram) on the brainstem and spinal cord. The brainstem and spinal cord radiation dose calculation are analyzed by using the SPSS independent t-test (α = 0,05). The average dose that received by brainstem on AAA calculation method is 34,55±0,02 Gy and PBC calculation method is 34,34±0,02 Gy. The average dose that received by the spinal cord of the AAA calculation method is 41,25±0,02 Gy and PBC calculation method is 41,02±0,02 Gy. There is no significant difference between the radiation dose received by the brainstem from AAA and PBC calculation methods (p = 0.91). There is no significant difference between the radiation dose received by the spinal cord from AAA and PBC calculation methods (p = 0.51). Indeed, both calculation methods have the same safety level.