Collapsed cone convolution and analytical anisotropic algorithm dose calculations compared to VMC++ Monte Carlo simulations in clinical cases

Abstract

The purpose of this work was to study and quantify the differences in dose distributions computed with some of the newest dose calculation algorithms available in commercial planning systems. The study was done for clinical cases originally calculated with pencil beam convolution (PBC) where large density inhomogeneities were present. Three other dose algorithms were used: a pencil beam like algorithm, the anisotropic analytic algorithm (AAA), a convolution superposition algorithm, collapsed cone convolution (CCC), and a Monte Carlo program, voxel Monte Carlo (VMC++). The dose calculation algorithms were compared under static field irradiations at 6 MV and 15 MV using multileaf collimators and hard wedges where necessary. Five clinical cases were studied: three lung and two breast cases. We found that, in terms of accuracy, the CCC algorithm performed better overall than AAA compared to VMC++, but AAA remains an attractive option for routine use in the clinic due to its short computation times. Dose differences between the different algorithms and VMC++ for the median value of the planning target volume (PTV) were typically 0.4% (range: 0.0 to 1.4%) in the lung and -1.3% (range: -2.1 to -0.6%) in the breast for the few cases we analysed. As expected, PTV coverage and dose homogeneity turned out to be more critical in the lung than in the breast cases with respect to the accuracy of the dose calculation. This was observed in the dose volume histograms obtained from the Monte Carlo simulations.

The photon dose calculation algorithm used in breast radiotherapy has significant impact on the parameters of radiobiological models

“…Studies on the performance and accuracy of the dose calculation algorithms in inhomogeneous phantoms have revealed that the type‐b algorithms are superior to the type‐a algorithms, 5 , 6 , 7 , 8 and that the Acuros XB algorithm is an accurate alternative to Monte Carlo calculations (9) . Type‐a and type‐b algorithms calculate absorbed dose to water.…”

“…The impact of the algorithm on the target coverage in lung cancer treatment has been described 1 , 7 , 8 , 10 . Two recent studies have quantified the difference between AAA and Acuros XB in stereotactic body radiation therapy of non‐small cell lung cancer 11 , 12 .…”

“…There is some knowledge on the dose distributions in target volumes close to air cavities like, for example, in the head and neck region 1 , 8 , 13 . Recent planning studies discuss the impact of low‐density organs on the coverage of adjacent target volumes, as in breast cancer treatment 7 , 14 , 15 , 16 …”

A clinical database to assess action levels and tolerances for the ongoing use of Mobius3D

“…In situations like this, the AAA of Eclipse has been shown to underpredict dose5, 20 and CCCS overpredict dose,21 both relative to gold standard Monte Carlo calculations. These publications are consistent with local observations whereby Mobius3D systematically calculates more dose to lung targets than Eclipse , where the reality is most likely to be somewhere in between.…”

Does intensity modulation increase target dose calculation errors of conventional algorithms for lung SBRT?

“…Another limitation of our study was that only one Type‐A and one Type‐B algorithm were investigated; therefore, the results and trends found may or may not be generalizable to other algorithms. Herein, the Type‐B algorithm utilized was AAA, which may be less accurate than another Type‐B algorithm, CCC 24, 25, 26. However, it should also be noted that AAA is still quite prevalent in the current clinical treatment planning, which makes this study quite relatable to contemporary practice.…”