Systems and methods for tissue tracking with radiation therapy beams

A method for performing a radiation therapy treatment comprising:

• delivering a radiation therapy beam from a radiation source to a patient having a fiducial marker positioned on the patient during a radiation therapy treatment;
• receiving the radiation therapy beam after passing through the patient using a first radiation detector tuned to acquire first imaging data;
• attenuating at least a portion of the radiation therapy beam as it travels from the radiation source to the patient;
• receiving the radiation therapy beam after passing through the patient using a second radiation detector tuned to acquire second imaging data at an attenuated intensity level corresponding to the portion of the radiation therapy beam that is attenuated;
• receiving, using one or more processors, the first imaging data and the second imaging data;
• reconstructing, using the one or more processors, images including the fiducial marker based on the first and second imaging data, when the fiducial marker is irradiated by the at least a portion of the radiation therapy beam that is attenuated;
• generating, a first image using the first imaging data and a second image using the second imaging data;
• combing the first image and the second image by weighting the second image over the first image when the fiducial is within the periphery of the radiation therapy beam;
• subtracting the second image from the first image to generate a subtracted second image;
• and
• locating the imaging fiducial in the subtracted second image.

A radiation therapy system comprising:

• a radiation source configured to emit a radiation therapy beam toward a patient at a selected energy level;
• a collimator positioned to receive the radiation therapy beam before reaching the patient and to attenuate at least a periphery of the radiation therapy beam to an attenuated intensity level;
• a radiation fiducial configured to be coupled to a patient;
• a first radiation detector positioned to acquire first imaging data from the patient using a first plurality of sensing elements tuned to acquire the radiation therapy beam at the selected intensity level;
• a second radiation detector positioned to acquire second imaging data from the patient using a second plurality of sensing elements tuned to acquire the radiation therapy beam at the attenuated intensity level;
• a processor configured to receive the first imaging data and the second imaging data and selective combine the first imaging data and the second imaging data to track the position of the imaging fiducial in an attenuated periphery of the radiation therapy beam.