title: Differences in dose-volumetric data between the analytical anisotropic algorithm and the x-ray voxel Monte Carlo algorithm in stereotactic body radiation therapy for lung cancer.
abstract: The objective of this study was to evaluate the differences in dose-volumetric data obtained using the analytical anisotropic algorithm (AAA) vs the x-ray voxel Monte Carlo (XVMC) algorithm for stereotactic body radiation therapy (SBRT) for lung cancer. Dose-volumetric data from 20 patients treated with SBRT for solitary lung cancer generated using the iPlan XVMC for the Novalis system consisting of a 6-MV linear accelerator and micro-multileaf collimators were recalculated with the AAA in Eclipse using the same monitor units and identical beam setup. The mean isocenter dose was 100.2% and 98.7% of the prescribed dose according to XVMC and AAA, respectively. Mean values of the maximal dose (D(max)), the minimal dose (D(min)), and dose received by 95% volume (D₉₅) for the planning target volume (PTV) with XVMC were 104.3%, 75.1%, and 86.2%, respectively. When recalculated with the AAA, those values were 100.8%, 77.1%, and 85.4%, respectively. Mean dose parameter values considered for the normal lung, namely the mean lung dose, V₅, and V₂₀, were 3.7Gy, 19.4%, and 5.0% for XVMC and 3.6Gy, 18.3%, and 4.7% for the AAA, respectively. All of these dose-volumetric differences between the 2 algorithms were within 5% of the prescribed dose. The effect of PTV size and tumor location, respectively, on the differences in dose parameters for the PTV between the AAA and XVMC was evaluated. A significant effect of the PTV on the difference in D₉₅ between the AAA and XVMC was observed (p = 0.03). Differences in the marginal doses, namely D(min) and D₉₅, were statistically significant between peripherally and centrally located tumors (p = 0.04 and p = 0.02, respectively). Tumor location and volume might have an effect on the differences in dose-volumetric parameters. The differences between AAA and XVMC were considered to be within an acceptable range (<5 percentage points).
authors.affiliation: Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Wambaka Ange
authors.initials: WA
authors.lastname: Mampuya
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Matsuo
authors.forename: Akira
authors.initials: A
authors.lastname: Nakamura
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Nakamura
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Mukumoto
authors.forename: Yuki
authors.initials: Y
authors.lastname: Miyabe
authors.forename: Masaru
authors.initials: M
authors.lastname: Narabayashi
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Sakanaka
authors.forename: Takashi
authors.initials: T
authors.lastname: Mizowaki
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hiraoka
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008175:Lung Neoplasms / Q000532:radiotherapy* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009010:Monte Carlo Method; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods*