Stereotactic-guided radiation therapy system with variable-length compensating collimator

A system for stereotactic-guided radiation therapy for treating a lesion within a patient's body comprising:

• a stereotactic fixation device;
• a linear accelerator having a rotatable couch;
• and
• a collimator for focusing a beam of radiation from the linear accelerator, including means for providing a variable length pathway for the beam of radiation, the pathway having a material substantially equivalent to tissue of the patient associated with the pathway, the beam of radiation passing through the pathway prior to entering the patient, the length of the pathway throughout the therapy being varied to pass the beam of radiation through substantially the same distance of tissue and tissue equivalent material before the beam of radiation is delivered to the lesion, whereby the lesion is treated throughout the therapy with substantially the same amount of radiation.

A method of stereotactic-guided radiation therapy of a lesion within a patient's body comprising the steps of:

• placing the patient on a rotatable couch associated with a linear accelerator having a collimator and a gantry;
• disposing the lesion of the patient at the isocenter of the linear accelerator;
• focusing a beam of radiation toward the lesion and through a variable length pathway associated with the collimator, the pathway having a material substantially equivalent to the tissue of the patient, the beam of radiation passing through the pathway prior to entering the patient;
• moving the collimator with respect to the patient while focusing the beam of radiation toward the lesion;
• and
• varying the length of the variable length pathway while moving the collimator, so that the beam of radiation passes through substantially the same distance of tissue and tissue equivalent material while the collimator is being moved, and the lesion is treated throughout the therapy with substantially the same amount of radiation.