Abstract
Purpose: The aim of this study was to develop a method for the direct measurement of electron beam width and distribution at the scattering foil on the carrousel in a medical linear accelerator gantry head, which differs from an existing indirect method for measuring the focal spot size using a camera or metallic slit located outside the gantry head. Methods: The electron beam emitted by the linear accelerator was used to irradiate radiochromic film mounted on the scattering foil on the carrousel, which was not used for clinical treatment. The electron beam width at the scattering foil position was then evaluated using the full width at half maximum of the Gaussian distribution approximated from each one dimensional distribution of the irradiated radiochromic film. Results: The electron beam width at the scattering foil position was found to be 3.1 to 6.4 mm in the crossline direction and 2.8 to 5.5 mm in the inline direction with electron energy of 4 to 16 MeV. The two-dimensional distribution of the electron beam was therefore elliptical or distorted in shape, not circular. Conclusions: Direct measurement of the electron beam width at the scattering foil in the carrousel of a medical linear accelerator is possible, though the use of lower sensitivity film in addition to indirect methods is expected to bring about better results. However, as this method does not allow for direct measurement of the incident angle of the accelerated electron beam, further improvements and refinements are still needed.
Highlights
IntroductionIn previous research into X-ray irradiation used for external radiation therapy, the focal spot size of the electron beam incident on a target was measured using indirect methods involving a spot camera [3] or metallic thin slit [4] [5] [6] located outside the irradiation gantry head
The aim of this study was to develop a method for the direct measurement of electron beam width and distribution at the scattering foil on the carrousel in a medical linear accelerator gantry head, which differs from an existing indirect method for measuring the focal spot size using a camera or metallic slit located outside the gantry head
As this method does not allow for direct measurement of the incident angle of the accelerated electron beam, further improvements and refinements are still needed
Summary
In previous research into X-ray irradiation used for external radiation therapy, the focal spot size of the electron beam incident on a target was measured using indirect methods involving a spot camera [3] or metallic thin slit [4] [5] [6] located outside the irradiation gantry head. This approach, makes it difficult to calculate the distribution of the accelerated electron beam before reaching the X-ray target, as the spread of the focal spot through this target can vary if it is not manufactured uniformly. This means that the electron beam is absorbed and scattered by the metallic target, which increases the spread of its distribution after the target
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
