TITLE:
Verification and Dosimetric Impact of Acuros XB Algorithm for Stereotactic Body Radiation Therapy (SBRT) and RapidArc Planning for Non-Small-Cell Lung Cancer (NSCLC) Patients
AUTHORS:
Suresh Rana, Kevin Rogers, Terry Lee, Daniel Reed, Christopher Biggs
KEYWORDS:
Acuros XB; AAA; Heterogeneity Correction; SBRT; RapidArc; Lung Cancer
JOURNAL NAME:
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology,
Vol.2 No.1,
February
26,
2013
ABSTRACT: Purpose: The experimental verification of the Acuros XB (AXB) algorithm was conducted in
a heterogeneous rectangular slab phantom, and compared to the Anisotropic
Analytical Algorithm (AAA). The dosimetric impact of the AXB for stereotactic
body radiation therapy (SBRT) and RapidArc planning for 16 non-small-cell lung
cancer (NSCLC) patients
was assessed due to the dose recalculation from the AAA to the AXB. Methods: The calculated central axis percentage depth doses
(PDD) in a heterogeneous slab phantom for an open field size of 3 ×3 cm2 were
compared against the PDD measured by an
ionization chamber. For 16 NSCLC patients, the dose-volume parameters from the
treatment plans calculated by the AXB and the AAA were compared using identical
jaw settings, leaf positions, and monitor units (MUs). Results: The results from the heterogeneous slab phantom study
showed that the AXB was more accurate than the AAA; however, the dose
underestimation by the AXB (up to ?3.9%) and AAA (up to ?13.5%) was observed.
For a planning target volume (PTV) in the NSCLC patients, in comparison to the
AAA, the AXB predicted lower mean and minimum doses by average 0.3% and 4.3%
respectively, but a higher maximum dose by average 2.3%. The averaged maximum
doses to the heart and spinal cord predicted by the AXB were lower by 1.3% and
2.6% respectively; whereas the doses to the lungs predicted by the AXB were
higher by up to 0.5% compared to the AAA. The percentage of ipsilateral lung volume
receiving at least 20 and 5 Gy (V20 and V5 respectively) were higher in the AXB
plans than in the AAA plans by average 1.1% and 2.8% respectively. The AXB
plans produced higher target heterogeneity by average 4.5% and lower plan
conformity by average 5.8% compared to the AAA plans. Using the AXB, the PTV
coverage (95% of the PTV covered by the 100% of the prescribed dose) was
reduced by average 8.2% than using the AAA. The AXB plans required about 2.3%
increment in the number of MUs in order to achieve the same PTV coverage as in
the AAA plans. Conclusion: The AXB
is more accurate to use for the dose calculations in SBRT lung plans created
with a RapidArc technique; however, one should also note the reduced PTV
coverage due to the dose recalculation from the AAA to the AXB.