Investigation of Alternate Materials for Apertures In Proton Therapy

The use of protons for radiation treatments was first developed in the late 1950's. Now, proton therapy has become increasing popular in recent years because of its effectiveness in treating cancer/tumors in sensitive areas of the human body, at a cost comparable to other radiation treatments. The primary components of proton radiation are the: cyclotron/synchrotron (produces the protons), nozzle (focuses and aims protons), compensator (controls the depth of protons penetration in the z direction), and aperture (shapes the protons). Unlike the compensator, the aperture must completely stop the incoming protons, allowing none to penetrate into the patient. Because the aperture must completely stop the incoming protons, there are parameters considered in addition to those of the compensator, such as: heat dissipation, stopping power, and life cycle. Due to these numerous parameters, the two most common materials used for apertures are Brass and Cerrobend. While Brass is cheap, readily available, easy to machine, and has reasonable stopping power for a given thickness, it is limited in its number of uses, to only a few times before it is too radioactive. Cerrobend while also a good material to use as an aperture has environmental issues. Therefore, the focus of this paper is to look at possible alternatives such as composite materials that can continue to maintain all the benefits of Brass and Cerrobend while increasing the useful life and reducing its environmental impact.