Modern medical linear gas pedals are fully functional, fully digitalized, and can carry out three-dimensional conformal radiotherapy, intensity-modulated conformal radiotherapy, and X-knife (also known as photon knife) therapy. It usually contains two or more grades of high-energy X-rays and multiple grades of electron rays, which facilitates clinicians to choose the type of rays according to the tumor site.
Compared with cobalt-60, its advantages are better skin protection and high depth dose, but with higher energy, the shot dose increases and the relative bone absorption rises. Therefore, the energy of high-energy X-rays is generally selected from 4 to 10 MV, and the most commonly used energy is 6 MV. Cobalt-60 machines use permanent radioactive sources, cobalt source half-life of about 5 to 10 years need to be replaced once, the nuclear waste disposal is more difficult to maintain engineers and operating technicians inevitably receive nuclear radiation. Linear gas pedals produce high-energy X-rays and electron beams only when they are energized, and there are no gamma rays produced by cobalt-60 machines during use and maintenance. According to the ALARA principle of radiotherapy protection (as low as reasonably achievable), gamma rays will give way to X-rays, i.e. linear gas pedals will gradually replace cobalt-60 treatment machines.