Dosimetric comparison of peripheral NSCLC SBRT using Acuros XB and AAA calculation algorithms

Abstract

There is a concern for dose calculation in highly heterogenous environments such as the thorax region. This study compares the quality of treatment plans of peripheral non-small cell lung cancer (NSCLC) stereotactic body radiation therapy (SBRT) using 2 calculation algorithms, namely, Eclipse Anisotropic Analytical Algorithm (AAA) and Acuros External Beam (AXB), for 3-dimensional conformal radiation therapy (3DCRT) and volumetric-modulated arc therapy (VMAT). Four-dimensional computed tomography (4DCT) data from 20 anonymized patients were studied using Varian Eclipse planning system, AXB, and AAA version 10.0.28. A 3DCRT plan and a VMAT plan were generated using AAA and AXB with constant plan parameters for each patient. The prescription and dose constraints were benchmarked against Radiation Therapy Oncology Group (RTOG) 0915 protocol. Planning parameters of the plan were compared statistically using Mann-Whitney U tests. Results showed that 3DCRT and VMAT plans have a lower target coverage up to 8% when calculated using AXB as compared with AAA. The conformity index (CI) for AXB plans was 4.7% lower than AAA plans, but was closer to unity, which indicated better target conformity. AXB produced plans with global maximum doses which were, on average, 2% hotter than AAA plans. Both 3DCRT and VMAT plans were able to achieve D95%. VMAT plans were shown to be more conformal (CI = 1.01) and were at least 3.2% and 1.5% lower in terms of PTV maximum and mean dose, respectively. There was no statistically significant difference for doses received by organs at risk (OARs) regardless of calculation algorithms and treatment techniques. In general, the difference in tissue modeling for AXB and AAA algorithm is responsible for the dose distribution between the AXB and the AAA algorithms. The AXB VMAT plans could be used to benefit patients receiving peripheral NSCLC SBRT.

Dosimetric Impact of Acuros XB Dose-to-Water and Dose-to-Medium Reporting Modes on Lung Stereotactic Body Radiation Therapy and Its Dependency on Structure Composition

“…Regarding PTV coverage parameters, our results differed from those published in the literature. While we found a lower D 95 and no significant difference in D 98 when comparing AAA with AXB, it is widely reported that AAA overestimates these parameters and the minimum dose 7,9,[18][19][20][21][22][25][26][27]30 . The reason for this discrepancy is that while our plans were initially optimized for AXB and then recalculated, keeping identical beam parameters for AAA, most prior studies adopted the opposite method.…”

“…An important aspect of our study concerns the change introduced with AXB v11 regarding the determination of tissue types from CT images 32,33 . The version of AXB used in our study could produce different results than those previously obtained in studies that used v10 [7][8][9]21,25,26,30 .…”

“…Differences in all cases are below 1.5%. In contrast, studies based on AXB v10 found that AAA overestimated D mean or D 50 by up to 4% 7,9,21,25,26,30 . This finding, probably attributable to the different material assignment between version 10 and 11, may affect PTV dose prescription.…”

“…Several studies have assessed the implications of using AXB for lung SBRT treatment planning [7][8][9][18][19][20][21][22][23][24][25][26][27][28][29][30] . In most cases, the impact in dose-volume parameters is below 2% except for the target coverage, which is considerably lower, and the Dw maximum dose in bony structures, which is significantly higher, in AXB-recalculated plans, as happens when MC is adopted 31 .…”

“…In most cases, the impact in dose-volume parameters is below 2% except for the target coverage, which is considerably lower, and the Dw maximum dose in bony structures, which is significantly higher, in AXB-recalculated plans, as happens when MC is adopted 31 . Certain studies used an older version of AXB (v10) [7][8][9]21,25,26,30 , which differs from more recent versions in many respects, most importantly with regard to CT-to-material conversions 32,33 . The number of dose-volume parameters for organs at risk (OARs) is limited in all studies, particularly those examining Dw, which is a better estimate of dose to sensitive tissue in bone than Dm 34 .…”