Respiratory biofeedback for MRI-guided radiotherapy

A method of operating a medical system, wherein the medical system comprises:

• a magnetic resonance imaging system;
• a radiotherapy system configured to controllably irradiate a target volume within an irradiation zone;
• a subject support configured to support at least a ventral region of a subject within the irradiation zone;
• a breath monitor system comprising a camera, the breath monitor system configured to provide a motion signal descriptive of subject breathing motion;
• and
• a subject display configured to display a breathing phase indicator to the subject supported by the subject support;
• wherein the method comprises:
• acquiring a measured motion signal with the breath monitor system for a predetermined duration;
• controlling the magnetic resonance imaging system with calibration pulse sequence commands to acquire calibration magnetic resonance data, wherein the calibration pulse sequence commands are configured to acquire calibration magnetic resonance data from an imaging zone according to a four-dimensional magnetic resonance imaging protocol, wherein the calibration magnetic resonance data is divided into movement phase bins, and
• wherein the method further comprises repeatedly:
• determining a temporary desired motion signal by temporally stepping through the measured motion signal;
• acquiring a calibration motion signal using the breath monitor system;
• bin the calibration magnetic resonance data into the movement phase bins using the calibration motion signal, and
• rendering the breathing phase indicator on the subject display, wherein the breathing phase indicator is configured to indicate a difference between the temporary desired motion signal and the calibration motion signal;
• wherein the method further comprises repeatedly:
• determining a desired motion signal by temporally stepping through the measured motion signal;
• acquiring a current motion signal using the breath monitor system;
• rendering the breathing phase indicator on the subject display, wherein the breathing phase indicator is configured to indicate a difference between the desired motion signal and the current motion signal;
• and
• generating control commands configured to control targeting of the radiotherapy system using a first portion of time resolved magnetic resonance imaging dataset synchronized to the desired motion signal or a second portion of the time resolved magnetic resonance imaging dataset referenced by the current motion signal wherein the control commands are selected between the first portion of the time resolved magnetic resonance imaging dataset and the second portion of the time resolved magnetic resonance imaging dataset by applying a predetermined criterion to a match between the current motion signal and the measured motion signal.

A tangible, non-transitory computer readable medium that stores machine executable instructions, which when executed by a processor, cause the processor to:

• acquire a measured motion signal with a breath monitor system for a predetermined duration;
• control a magnetic resonance imaging system with calibration pulse sequence commands to acquire calibration magnetic resonance data, wherein the calibration pulse sequence commands are configured to acquire the calibration magnetic resonance data from an imaging zone according to a four-dimensional magnetic resonance imaging protocol, wherein the calibration magnetic resonance data is divided into movement phase bins;
• determine a temporary desired motion signal by temporally stepping through the measured motion signal;
• acquire a calibration motion signal using the breath monitor system;
• bin the magnetic resonance imaging data into the movement phase bins using the calibration motion signal, and
• render a breathing phase indicator on a subject display, wherein the breathing phase indicator is configured to indicate a difference between the temporary desired motion signal and the calibration motion signal;
• and
• repeatedly:
• determine a desired motion signal by temporally stepping through the measured motion signal;
• acquire a current motion signal using the breath monitor system;
• render the breathing phase indicator on the subject display, wherein the breathing phase indicator is configured to indicate a difference between the desired motion signal and the current motion signal;
• and generate control commands configured to control targeting of a radiotherapy system using a first portion of a time resolved magnetic resonance imaging dataset synchronized to the desired motion signal or a second portion of the time resolved magnetic resonance imaging dataset referenced by the current motion signal wherein the control commands are selected between the first portion of the time resolved magnetic resonance imaging dataset and the second portion of the time resolved magnetic resonance imaging dataset by applying a predetermined criterion to a match between the current motion signal and the measured motion signal.