Gamma Knife surgery is unique in that no surgical incision is made to expose the inside of the brain, thereby reducing the risk of surgical complications and eliminating the side effects and dangers of general anesthesia. The "blades" of the Gamma Knife are the beams of gamma radiation programmed to target the lesion at the point where they intersect. In a single treatment session, 201 beams of gamma radiation focus precisely on the lesion. Over time, most lesions slowly decrease in size and dissolve. The exposure is brief and only the tissue being treated receives a significant radiation dose, while the surrounding tissue remains unharmed. With the Gamma Knife, a surgical incision is not required; the attendant risks of open neurosurgical procedures (hemorrhage, infection, cerebrospinal fluid leakage, etc.) are therefore avoided.