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Investigating the Impact of the AXB Dose Calculation Algorithm in Tangential Breast Plans

A Kejda1 , N Nahar2 , T Wang2,3 , S Ashworth2 , J Sykes1*, (1) Blacktown Cancer and Haematology Centre, Blacktown, NSW, (2) Crown Princess Mary Cancer Centre, Westmead, NSW, (3) University of Sydney


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: To quantify dosimetric differences between photon breast treatment plans created in Eclipse, calculated with the default Anisotropic Analytic Algorithm (AAA) and Acuros External Beam (AXB) dose calculation algorithm.

Methods: Twenty 6X breast plans, originally generated using Eclipse and calculated with AAA, were recalculated using AXB reporting dose to water. Plan metrics for AAA and AXB plans evaluated were D99%, D98%, D95%, D90%, D50%, D1%, D2cc and mean heart dose. The dose distribution was also compared qualitatively.

Results: No statistically significant difference between plan metrics was found between the two algorithms, except for D2cc (t-test P<0.001), where mean dose was approximately 1 Gy higher for AXB (figure 1). For AAA, all plans met a D2cc < 110% criteria, while for AXB only nine plans met this. Local dose differences between the algorithms of up to ±2 Gy were observed within the PTV, however these had little impact on overall plan quality. Mean dose to heart was not statistically significantly different however a pattern of decreased dose to left sided heart was observed.

Conclusion: The use of AXB dose calculation algorithm reporting dose to water, has a minimal impact on the PTV dose distribution for clinical breast plans. However, it does calculate D2cc to be on average 1 Gy hotter than AAA, and higher for individual plans. This should be considered when deciding if AXB is to be implemented for clinical breast planning.


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