Hybrid Algorithm for Dose Calculation in Cms Xio Treatment Planning System

Abstract

This study aimed at designing an improved hybrid algorithm by explicitly solving the linearized Boltzmann transport equation (LBTE) which is the governing equation that describes the macroscopic behaviour of radiation particles (neutrons, photons, electrons, etc). The algorithm accuracy will be evaluated using a newly designed in-house verification phantom and its results will be compared to those of the other XiO photon algorithms. The LBTE was solved numerically to compute photon transport in a medium. A programming code (algorithm) for the LBTE solution was developed and applied in the treatment planning system (TPS). The accuracy of the algorithm was evaluated by creating several plans for both the designed phantom and solid water phantom using the designed algorithm and other Xio photon algorithms. The plans were sent to a pre-calibrated Eleckta linear accelerator for measurement of absorbed dose.The results for all treatment plans using the hybrid algorithm compared to the 3 Xio photon algorithms were within 4 % limit. Calculation time for the hybrid algorithm was less in plans with larger number of beams compared to the other algorithms; however, it is higher for single beam plans. The hybrid algorithm provides comparable accuracy in treatment planning conditions to the other algorithms. This algorithm can therefore be employed in the calculation of dose in advance techniques such as IMRT and Rapid Arc by a radiotherapy centres with cmsxio treatment planning system as it is easy to implement. I. Introduction The knowledge of radiation dose distribution in the patient is required before they undergo radiotherapy treatment. This can be ascertained by planning the treatment procedure on a dedicated computer system (treatment planning). Treatment planning can be described as the iterative process whereby the treatment strategy of the oncologist is quantified as a set of instructions including a description of the expected dose distribution in the patient. Planning is based on predictions of dosage delivered to the patient by the proposed arrangement of radiation beams. When a treatment planning system (TPS) is commissioned, beam data from local linear accelerator must be entered into it. The data requirements for computerised treatment planning systems may be categorised in terms of how the data will be used. It is necessary for the TPS to represent each individual treatment machine. The details and format of the required data will depend on the requirements of each planning system. Treatment planning will almost certainly include measured data and user-determined data. It must also be verified that any averaging of data by the TPS algorithms does not produce unacceptable differences from the measured data. The efficiency of the calculation algorithm in both standard and non- standard conditions must be tested to determine its applicability and limitations. The distinction must be made between the data collected for entry into the TPS and data collected in order to validate the TPS. Basic data are entered into and used by the TPS to calculate dose distributions. Reference data are acquired under standard conditions (usually in water-filled plotted tank) to validate basic data or check the TPS algorithm. After the full commissioning process of the TPS, verification of its accuracy is often done by using a verification phantom, an object that mimics human body that can be used for planning and treated like a normal patient.