title: Clinical impact of using the deterministic patient dose calculation algorithm Acuros XB for lung stereotactic body radiation therapy.
abstract: OBJECTIVE
  To evaluate the clinical impact of using the deterministic dose calculation algorithm, Acuros XB, for early stage lung cancer patients undergoing stereotactic body radiotherapy (SBRT).
  
  
  METHODS
  Seventy-seven stage I non-small cell lung cancer patients who underwent lung SBRT from 2008 to 2012 at our center were included in this study. All treatment plans originally calculated by the anisotropic analytical algorithm (AAA) were recalculated using the AAA and Acuros XB algorithms with identical monitor units and beam arrangements. The dose, dose distribution, conformality number (CN) and heterogeneity index (HI) of the target were determined for each plan. A paired matched t-test was used to evaluate the difference between the mean dose, the dose distribution, and the CN and HI for the target. The importance of tumor (volume, location), patient (pulmonary functional, body mass index) and treatment (number of SBRT beams) on the dose distributions obtained from the two algorithms was statistically determined using linear regression analyses.
  
  
  RESULTS
  The mean target dose was same for both algorithms. Compared to AAA, a small and significant difference in dose distribution in the target was found for the Acuros XB algorithm, resulting in lower conformity (-2.1%, p < 0.0001) and higher heterogeneity (p < 0.0001) of dose. Single logistic regression identified pulmonary function, number of beams and target location as being correlated with the difference of CN between the two calculations. Multivariate analysis indicated that the patient's pulmonary function (p = 0.0296) was the only predictor for the difference in conformality between the two dose calculation algorithms.
  
  
  CONCLUSIONS
  In lung SBRT, the patient's pulmonary function is responsible for the difference in target dose distribution between the Acuros XB and AAA algorithms. The Acuros XB algorithm could be used to advantage in patients with compromised pulmonary function based on its accurate modeling of lung tissue in comparison to AAA.
authors: Department of Radiation Oncology, Tom Baker Cancer Center , Calgary , University of Calgary , Alberta , Canada.
authors: Hong-Wei
authors: HW
authors: Liu
authors: Zoann
authors: Z
authors: Nugent
authors: Ravinder
authors: R
authors: Clayton
authors: Peter
authors: P
authors: Dunscombe
authors: Harold
authors: H
authors: Lau
authors: Rao
authors: R
authors: Khan
mesh_terms: D000465:Algorithms; D015992:Body Mass Index; D002289:Carcinoma, Non-Small-Cell Lung / Q000601:surgery*; D006801:Humans; D008175:Lung Neoplasms / Q000601:surgery*; D015999:Multivariate Analysis; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*