Fast dose calculation in magnetic fields withGPUMCD

Abstract

A new hybrid imaging-treatment modality, the MRI-Linac, involves the irradiation of the patient in the presence of a strong magnetic field. This field acts on the charged particles, responsible for depositing dose, through the Lorentz force. These conditions require a dose calculation engine capable of taking into consideration the effect of the magnetic field on the dose distribution during the planning stage. Also in the case of a change in anatomy at the time of treatment, a fast online replanning tool is desirable. It is improbable that analytical solutions such as pencil beam calculations can be efficiently adapted for dose calculations within a magnetic field. Monte Carlo simulations have therefore been used for the computations but the calculation speed is generally too slow to allow online replanning. In this work, GPUMCD, a fast graphics processing unit (GPU)-based Monte Carlo dose calculation platform, was benchmarked with a new feature that allows dose calculations within a magnetic field. As a proof of concept, this new feature is validated against experimental measurements. GPUMCD was found to accurately reproduce experimental dose distributions according to a 2%-2 mm gamma analysis in two cases with large magnetic field-induced dose effects: a depth-dose phantom with an air cavity and a lateral-dose phantom surrounded by air. Furthermore, execution times of less than 15 s were achieved for one beam in a prostate case phantom for a 2% statistical uncertainty while less than 20 s were required for a seven-beam plan. These results indicate that GPUMCD is an interesting candidate, being fast and accurate, for dose calculations for the hybrid MRI-Linac modality.

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

“…Recently, a new commercial GPU‐based Monte Carlo dose calculation algorithm (GPUMCD) 10 , 11 has been proposed by the vendor Elekta (Elekta AB, Stockholm, Sweden) and is available in the research version of the Monaco TPS. The Monaco TPS currently has a clinical MC dose calculation algorithm called XVMC (12) for photons, which is founded on the voxel‐based MC algorithm (VMC) (13) for electron beams.…”

Magnetic field dose effects on different radiation beam geometries for hypofractionated partial breast irradiation

“…Monaco uses a Monte Carlo radiation transport method accelerated by a fast graphics processing unit currently under evaluation for clinical deployment, called the Graphics Processing Unit Monte Carlo Dose algorithm (GPUMCD) 18, 19. This Monte Carlo dose calculation algorithm can account for the magnetic field effects on the dose deposition by the radiation beam, which for the MRI‐Linac has an energy of 7 MV.…”

New concept on an integrated interior magnetic resonance imaging and medical linear accelerator system for radiation therapy

“…Hence, treatment planning with the magnetic field considered is necessary, which has also been suggested previously by other studies. [28][29][30][31][32][33] The most distinct feature differentiating our conceptual system from the existing MRI-LINAC systems is its smaller FoV. As opposed to integrating a full body MRI scanner with a LINAC, we propose using a new MRI design that has a small (∼15 cm diameter) FoV.…”