B. Treatment planning system

The AAA commissioning process within the Eclipse TPS has three steps: 1) data entry, 2) calculation of the beam model, and 3) verification of the beam model. ¹¹ , ¹² , ¹³ Table 1 shows each of the data elements required for the commission procedure and where they fall in terms of dose contribution. The data required to calculate the beam model come from a combination of data entered manually by the user (e.g., beam geometry, output factors, depth dose curves, beam profiles, flattening filter material) and data retrieved from a machine data library (mean radial energy, initial photon energy spectrum). Primary parameters are those used to model the primary source of photons, which consists of Bremstrahlung X‐rays produced in the target that do not interact in the head of the treatment unit. Secondary parameters model dose from photons scattered from the flattening filter and collimators, which is modeled as a virtual plane source located at the bottom of the flattening filter. Electron contamination parameters model dose from electrons generated in the treatment unit head and in air, and is modeled at the target plane using two Gaussian curves (which determine lateral spread of electrons and field size dependence) and one dose deposition curve, which is derived empirically by the beam modeling algorithm as the difference between the largest field size depth dose curves measured with and calculated without the electron contamination. While the primary photon, secondary photon, and electron contamination are defined, modeled, and verified within the AAA commissioning procedure, the MLC parameters are not included in this process and are, instead, defined separately from the beam model.

During the first step of the commissioning process, machine parameters are input and, using these parameters, the TPS accesses a machine library that includes information about the specific machine that is being commissioned. Step 2 (calculation of the beam model) occurs once the required data have been entered. During this step, the beam model parameters, such as the initial beam spectra and second source parameters, are fit to match the input beam profiles and depth curves. After the AAA beam modeling algorithm is prepared, the TPS allows the user to evaluate the agreement between the calculated and measured curves. This comparison is done for all input beam profiles and depth‐dose curves.

Treatment planning system commissioning parameters for AAA.