Commissioning and characterization of the spot scanning proton beam with a mini-beam option for intensity modulated proton beam therapy
Dr. Vadim Moskvin
St. Jude Children’s Research Hospital, Memphis, TN
Friday, February 8 at 2 pm
101 Kinard Hall
Spot scanning proton beam with an option of intensity modulated proton therapy (IMPT) is considered to be the most advanced option in proton therapy. A non-collimated narrow spot scanning beam eliminates undesired secondary neutrons from the collimator or patient specific aperture, reducing the risks of secondary malignancies for long-term survivors. With the intend to increase the dose field conformity, IMPT systems’ design shows development toward smaller beam sizes. Currently, the size of 3 mm sigma is common among the recently opened facilities. Novel spot scanning beam systems with a vacuum chamber can produce spot sizes below 2 mm sigma. Small beam size presents challenges for the commissioning measurements and for treatment planning algorithms. In my talk, I will discuss the commissioning of the novel spot scanning proton therapy beam system with mini beam option, featuring the role of the Monte Carlo (MC) modeling with its application to patient dose calculation, and the developments in mini-beam beam dose delivery characterization. We commissioned the Hitachi Probet-V spot scanning proton therapy system to produce primary beam (sigma ~2.5 mm for 221 MeV at isocenter, and less than 2 mm at a short airgap) and novel mini-beam (spot size with sigma of 1.4 mm for 221 MeV at isocenter, with less than 1 mm at a short airgap). The commissioning method consists of the MC simulation with the TOPAS Monte Carlo transport code and a system of validation measurements. The results of MC simulation generated data were applied to Eclipse (Eclipse v13.7.15, Varian) treatment planning system commissioning. The designed treatment machine MC model was used to develop an independent patient dose calculation tool. The small beam size and confined dose distribution for novel proton beam requires the development of new approaches to control range uncertainties. The 3D radiation acoustic imaging method (RACT) was proposed to verify the range and dose distribution from spot scanning proton beam in-vivo. Radiation acoustics method of range uncertainty measurements will be presented together with the new developments in dose delivery verification method based on Positron Emission Tomography (PET). The proton beam has elevated relative biological effectiveness (RBE) area at the distal edge of the spread-out Bragg Peak (SOBP), which may affect sensitive organs. The spot scanning proton mini-beams present additional challenges associated with the lateral increase of the RBE for each spot. The novel approach to radiobiological characterization of the spot scanning beam method will be presented. Monte Carlo simulation remains the most efficient computational method both for beam characteristic calculation and for commissioning and treatment planning simulation. Beam delivery monitoring method is required for spot-scanning proton beam therapy. The narrow proton beam provides higher conformal dose distribution, which would be beneficial for patients.
Refreshments will be served after the colloquium in the PandA Café.
Friday, February 8, 2019 at 2:00pm to 3:00pm
Kinard Laboratory of Physics, 101 Kinard Lab
140 Delta Epsilon Ct., Clemson, SC 29634, USA