Prog Med Phys.  2021 Dec;32(4):130-136. 10.14316/pmp.2021.32.4.130.

Dosimetric Comparison between Varian Halcyon Analytical Anisotropic Algorithm and Acuros XB Algorithm for Planning of RapidArc Radiotherapy of Cervical Carcinoma

• Mbewe J
• Shiba S

• KMID: 2524159
• DOI: http://doi.org/10.14316/pmp.2021.32.4.130

Abstract

Purpose
The Halcyon radiotherapy platform at Groote Schuur Hospital was delivered with a factory-configured analytical anisotropic algorithm (AAA) beam model for dose calculation. In a recent system upgrade, the Acuros XB (AXB) algorithm was installed. Both algorithms adopt fundamentally different approaches to dose calculation. This study aimed to compare the dose distributions of cervical carcinoma RapidArc plans calculated using both algorithms.
Methods
A total of 15 plans previously calculated using the AAA were retrieved and recalculated using the AXB algorithm. Comparisons were performed using the planning target volume (PTV) maximum (max) and minimum (min) doses, D95%, D98%, D50%, D2%, homogeneity index (HI), and conformity index (CI). The mean and max doses and D2% were compared for the bladder, bowel, and femoral heads.
Results
The AAA calculated slightly higher targets, D98%, D95%, D50%, and CI, than the AXB algorithm (44.49 Gy vs. 44.32 Gy, P=0.129; 44.87 Gy vs. 44.70 Gy, P=0.089; 46.00 Gy vs. 45.98 Gy, P=0.154; and 0.51 vs. 0.50, P=0.200, respectively). For target min dose, D2%, max dose, and HI, the AAA scored lower than the AXB algorithm (41.24 Gy vs. 41.30 Gy, P=0.902; 47.34 Gy vs. 47.75 Gy,P<0.001; 48.62 Gy vs. 50.14 Gy, P<0.001; and 0.06 vs. 0.07, P=0.002, respectively). For bladder, bowel, and left and right femurs, the AAA calculated higher mean and max doses.
Conclusions
Statistically significant differences were observed for PTV D2%, max dose, HI, and bowel max dose (P>0.05).

Keyword

Halcyon; Acuros XB; Analytical anisotropic algorithm; RapidArc; Radiotherapy

Figure

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  Fig. 1 Comparison of dosimetric parameters for PTV coverage calculated using AAA and AXB. PTV, planning target volume; AAA, analytical anisotropic algorithm; AXB, Acuros XB; Max, maximum; Min, minimum; HI, homogeneity index; CI, conformity index; MU, monitor unit.

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  Fig. 2 Comparison of dosimetric parameters for organs at risk calculated using AAA and AXB. AAA, analytical anisotropic algorithm; AXB, Acuros XB; Rt, right; Lt, Left; NTID, normal tissue integral dose; Max, maximum.

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  Fig. 3 Comparison of dose distributions calculated using AAA and AXB on the left- and right-hand sides, respectively, for a selected treatment plan. AAA, analytical anisotropic algorithm; AXB, Acuros XB.

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  Fig. 4 PTV dose–volume histograms calculated using AAA (squares) and AXB (triangles) for a selected treatment plan.

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  Fig. 5 Organs at risk dose–volume histograms calculated using AAA (squares) and AXB (triangles) for a selected treatment plan. The left femur, right femur, bowel, and bladder histograms are in purple, blue, red, and yellow, respectively.

Reference

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