# Dose Calculation Algorithms for External Radiation Therapy: An Overview for Practitioners
## 5 Calculation Algorithm Possibilities in Commercial Treatment Planning Systems
### Dosimetric Performance of the Commercial Algorithms  
Many authors have examined the dosimetric performance of the commercial dose calculation algorithms against measured data under homogeneous and heterogeneous irradiation geometries. According to [PERSON] [118], the accuracy of algorithms has been ranked in the following descending order: MC and LBTE, CCC, AAA, PBA (Figure 1). In the photon scenario, [PERSON] et al. [119] presented, in a homogeneous medium for 6 MV and 10 MV photon beams, the RayStation CCCS-based dose calculation accuracy and the plan quality assessment compared with the then-more-established Pinnacle TPS. Tolerances of 3% for in-field and out-of-field regions, 10% for buildup and penumbral regions, and gamma values of 2%/2 mm dose/distance acceptance criteria were reported versus the treatment machine-measured data. Equivalent plan quality was reported, compared to Pinnacle. Furthermore, the RayStation MC-based dose calculations, tested on both homogeneous and heterogeneous irradiation geometries for 6 MV and 10 MV FFF photon beams, showed a considerable agreement between measured and calculated dose curves. In most cases, the concordance was higher than 2%/2 mm across the high-dose regions of the profiles, whereas the out-of-field dose errors were lower than 1% [120]. The equivalent dosimetric performance of the Acuros XB algorithm in Eclipse TPS was demonstrated versus the X-ray voxel Monte Carlo (XVMC) algorithm. [PERSON] et al. [121] reported that AXB values agreed with MC values within 3.5% for all dose metrics in a patient cohort of 147 lung cancer patients treated using stereotactic body radiation therapy (SBRT). In a similar cohort, the different types of algorithms of the Eclipse TPS were investigated [98]. The lung SBRT target doses calculated by type-A algorithms were not affected by lung density variations, whereas type-B and type-C algorithms showed systematic correlations between density differences and target dose differences. [PERSON] et al. examined the accuracy of Monaco under different conditions [122]. Measurements of percent depth doses (PDDs) and profiles, open-field point-doses in homogenous and heterogeneous media, obliquely incident electron beams and gamma analysis were performed. Point-doses in water agreed within 2% with commissioning data in 99.5% and 98.6% of the points computed by MC and CC, respectively. The comparison of PDDs and profiles calculated by Monaco with measured data for photon beams led to Gamma index values lower than 1. All point-dose calculations for the eMC algorithm in water yielded agreement within 4% with measurements, whereas in heterogeneous media, at extended distances from source to surface or in the case of electron beams at oblique incident angles, values were below 5%. In the electron scenario and for low- and medium-energy electron dosimetry at oblique incident angles, an acceptable accuracy at the clinical level was also reported by [PERSON] et al. [123] for RayStation's application of the VMC++ algorithm. The results of the eMC algorithm compared with those of the GGPB algorithm in Eclipse TPS were reported by [PERSON] et al. [102] in the case of flat and varied surfaces for energies ranging from 6 to 20 MeV electron beams. The eMC algorithm resulted in predicted output changes within 3% for most scenarios and up to 6% at the lowest energy, in comparison with the GGPB algorithm, for which the discrepancies were up to 17% at the lowest energies. A poor accuracy was reported for the electron PBA algorithm in Pinnacle TPS. In bolus electron conformal therapy using a cylindrical patient, a pencil beam redefinition algorithm (PBRA, in-house C++ program) resulted at least twice the accuracy of the PBA [124]. In the proton scenario, [PERSON] et al. [125] tested the effect of varying planning parameters on pencil beam scanning dose distributions of four proton TPSs: Eclipse, Pinnacle, RayStation and XiO. An investigation was made into the implementation and optimal selection of different proton planning parameters by each system.