In a cyclotron particle is injected with a very small velocity near the canter of the cyclotron. Due to the Lorentz force acting on it, it starts rotating in a circle but the radius of the locus of the particle increases monotonously. Let us assume that that the DEE's of the cyclotron has a radius . So this is the maximum radius of the path followed by the particle.
Here,
This is the maximum speed achieved by the particle (where, has usual meaning).
As the velocity increases its KE also increases and becomes
just before exiting the cyclotron. This is very large compared to the initial KE ie. almost zero.