Difference in dose‐volumetric data between the analytical anisotropic algorithm, the dose‐to‐medium, and the dose‐to‐water reporting modes of the Acuros XB for lung stereotactic body radiation therapy

Abstract

The purpose of this study was to evaluate the difference in dose‐volumetric data between the analytical anisotropic algorithms (AAA) and the two dose reporting modes of the Acuros XB, namely, the dose to water (AXB−normalDw) and dose to medium (AXB−normalDm) in lung stereotactic body radiotherapy (SBRT). Thirty‐eight plans were generated using the AXB−normalDm in Eclipse Treatment Planning System (TPS) and then recalculated with the AXB−normalDw and AAA, using identical beam setup. A dose of 50 Gy in 4 fractions was prescribed to the isocenter and the planning target volume (PTV) D95%. The isocenter was always inside the PTV. The following dose‐volumetric parameters were evaluated; D2%, D50%, D95%, and D98% for the internal target volume (ITV) and the PTV. Two‐tailed paired Student's t‐tests determined the statistical significance. Although for most of the parameters evaluated, the mean differences observed between the AAA, AXB−normalDmand AXB−normalDw were statistically significant (p<0.05), absolute differences were rather small, in general less than 5% points. The maximum mean difference was observed in the ITV D50% between the AXB−normalDm and the AAA and was 1.7% points under the isocenter prescription and 3.3% points under the D95 prescription. AXB−normalDm produced higher values than AXB−normalDw with differences ranging from 0.4 to 1.1% points under isocenter prescription and 0.0 to 0.7% points under the PTV D95% prescription. The differences observed under the PTV D95% prescription were larger compared to those observed for the isocenter prescription between AXB−normalDm and AAA, AXB−normalDm and AXB−normalDw, and AXB−normalDw and AAA. Although statistically significant, the mean differences between the three algorithms are within 3.3% points.PACS number(s): 87.55.x, 87.55.D‐, 87.55.dk

Variation in current prescription practice of stereotactic body radiotherapy for peripherally located early stage non-small cell lung cancer: Recommendations for prescribing and recording according to the ACROP guideline and ICRU report 91

“…The effect of specifying the dose to medium should be further investigated. Although a study of Mampuya et al showed that dose to medium produced higher values than dose to water, the differences in PTV D95% were small and range between 0 and 0.7% [17].…”

European Organization for Research and Treatment of Cancer (EORTC) recommendations for planning and delivery of high-dose, high precision radiotherapy for lung cancer

“…Differences between more advanced algorithms still exist [76][77][78][79], with Monte Carlo algorithms possibly more accurate for estimating dose at the tumour periphery [80]. There is no consensus yet about the clinical acceptability and relevance of reported differences [76,81,82]. Comparisons between 3D dose calculations using the 'average CT' dataset and full 4D calculations show small differences of a few per cent [83,84].…”

AAPM Task Group 329: Reference dose specification for dose calculations: Dose‐to‐water or dose‐to‐muscle?

“…While this preference is clear for reference conditions of water versus soft tissue (the focus of this report), this can introduce more substantial changes in the dose reported to other media, particularly for media with very different atomic composition such as bone. Even in the lung, differences between D w,w , D w,m , and D m,m have been observed, although the magnitude of this difference varies depending on the metrics studied . These differences underscore the need for diligence if the dose reporting medium is changed, as is appropriate for any change in clinical practice.…”