A clinical study of lung cancer dose calculation accuracy by using Monte Carlo simulation

Objective: To study the evaluate the PBC and CCC algorithms for lung cancer radiotherapy with the Monte Carlo (MC). Methods: From 2012 to 2013 years, 24 patients with lung cancer were studied. For each patient was designed four plans with Oncentra Masterplan TPS.Two IMRT plans and two 3DCRT plans were developed with the PBC and CCC algorithms. Then the DICOM-RT files of the plans were exported to the MC system for recalculate. The differences of results were analyzed by paired-t test. Results: For 3DCRT and IMRT plans, the mean dose differences for GTV between CCC and MC, PBC and MC increased with the GTV volume decreasing (P = 0.00, 0.00, 0.00, 0.00), for IMRT plans the mean dose differences were found to be higher than that of 3DCRT plans (P = 0.00, 0.01).Comparison of DVHs, the differences became smaller gradually from D₉₈, D₉₅, D₉₀, D₅₀ to D₂ (P = 0.00, 0.00, 0.00, 0.00, 0.00), but the effect is not obvious in 3DCRT plans (P = 0.18, 0.08, 0.62, 0.08, 0.97) similarly, the same effect was found in the differences between PBC and MC for IMRT plans, and the differences of dose volume are lager than that of CCC and MC. For the dose of ipsilateral lung, CCC algorithm overestimated dose for all lung, PBC algorithm overestimated V_2O(P = 0.00, 0.00), but underestimated V₅(P = 0.00, 0.00), the difference of V₁₀ have no statistical significant (P = 0.47). Conclusions: It is recommended that the treatment plan of lung cancer should be calculated by an advanced algorithm other than PBC. MC can calculate dose distribution of lung cancer accurately and can provide a very good tool for benchmarking the performance of other dose calculation algorithms. (authors)