Experimental evaluation of a GPU-based Monte Carlo dose calculation algorithm in the Monaco treatment planning system

Area of Science:

• Medical Physics
• Radiotherapy
• Computational Dosimetry

Background:

• Monte Carlo (MC) methods are crucial for accurate dose calculation in radiotherapy.
• Advancements in GPU technology enable faster and more complex MC simulations.
• Elekta's Monaco treatment planning system (TPS) introduced a new GPU-based MC dose calculation algorithm (GPUMCD).

Purpose of the Study:

• To experimentally evaluate the accuracy of the new GPU-based Monte Carlo dose calculation algorithm (GPUMCD) in the Monaco TPS.
• To compare GPUMCD performance against the existing XVMC algorithm and the collapsed cone convolution (CCC) algorithm.
• To assess dose calculation accuracy in heterogeneous phantom scenarios relevant to clinical practice.

Main Methods:

• A beam model for a 6 MV Elekta Agility linac was commissioned in Monaco TPS.
• A heterogeneous phantom simulating tumor-in-lung, lung, and bone-in-tissue scenarios was constructed.
• Dose calculations were performed using GPUMCD, XVMC (Monaco), and CCC (Pinnacle TPS).
• Calculated doses were compared with experimental measurements using ionization chambers and Gafchromic films for various field sizes.

Main Results:

• GPUMCD and XVMC showed excellent agreement with measurements in homogeneous phantoms (within 2%/2 mm).
• In the tumor-in-lung phantom, GPUMCD dose calculations were within 2.5%/2.5 mm of film measurements.
• All algorithms performed within 3%/3 mm in the lung phantom, except CCC for small fields which underestimated dose.
• GPUMCD and XVMC accurately modeled interface effects in the bone phantom, outperforming CCC.

Conclusions:

• The GPUMCD algorithm demonstrates high accuracy for dose calculation with a standard linear accelerator, comparable to existing MC methods.
• GPUMCD shows improved accuracy in heterogeneous environments, particularly for complex scenarios like tumor-in-lung.
• The algorithm's ability to model interface effects accurately enhances its clinical potential for precise radiotherapy planning.