The gamma knife is a type of what we call stereotactic radiosurgery.

伽玛刀是一种立体定向放射外科手术。

This treatment is called stereotactic radiosurgery, and those light beams are beams of radiation: their task is to destroy tumors by gradually scrubbing away malignant cells.

这种治疗称为立体定向放射外科手术，那些光束就是辐射束：它们的任务是通过逐渐清除恶性细胞来摧毁肿瘤。