Systems and methods for fault detection in emission-guided radiotherapy
Disclosed herein are systems and methods for monitoring calibration of positron emission tomography (PET) systems. In some variations, the systems include an imaging assembly having a gantry comprising a plurality of positron emission detectors. A housing may be coupled to the gantry, and the housing may include a bore and a radiation source holder spaced away from a patient scan region within the bore. A processor may be configured to receive positron emission data from the positron emission detectors and to distinguish the positron emission data from the radiation source holder and from the patient scan region. A fault signal may be generated when the positron emission data from the radiation source holder exceeds one or more threshold parameters or criteria.
1. A method for monitoring PET detector function during a radiotherapy session, the method comprising:
acquiring positron emission data using one or more PET detectors during delivery of radiation therapy;
extracting positron emission data representing positron emission activity from a calibration source;
determining whether one or more PET detectors are faulty based on the extracted positron emission data; and
generating a fault signal if one or more PET detectors are faulty.
2. The method of claim 1 , wherein determining whether the one or more PET detectors are faulty comprises determining whether the extracted positron emission data meets a pre-determined criterion.
3. The method of claim 2 , wherein the pre-determined criterion comprises a spatial filter that selects for positron emission data originating from a location of the calibration source, and wherein determining whether one or more PET detectors is faulty comprises applying the spatial filter to the extracted positron emission data and determining whether the filtered positron emission data co-localizes with the location of the calibration source.
4. The method of claim 3 , wherein the spatial filter is adjustable.
5. The method of claim 2 , wherein the pre-determined criterion comprises a threshold number of coincident photon events detected with a first time difference, and wherein determining whether one or more PET detectors are faulty comprises generating a plot of an actual number of coincident photon events detected with the time difference, and wherein a fault signal is generated when the actual number of coincident photon events occurring with the time difference does not exceed the threshold number.
6. The method of claim 1 , wherein extracting positron emission data comprises calculating a location of the calibration source using the acquired positron emission data and wherein determining whether one or more PET detectors are faulty comprises determining whether the calculated location of the calibration source sufficiently corresponds to a location of the calibration source.
7. The method of claim 6 , wherein calculating the location of the calibration source uses a spatial filter.
8. The method of claim 1 , wherein the extracted positron emission data comprises PET detector calibration data.
9. The method of claim 8 , wherein the PET detector calibration data comprises one or more of spatial resolution data, temporal resolution data, energy sensitivity data, energy precision data, a number of detected lines-of-response (LORs) that intersect with a location of the calibration source, and/or energy levels of the detected LORs.
10. The method of claim 8 , wherein determining whether one or more PET detectors are faulty comprises determining whether the PET detector calibration data exceeds a threshold parameter.
11. The method of claim 1 , further comprising one or more of pausing the delivery of radiation therapy, performing diagnostics on the one or more PET detectors, de-activating the one or more PET detectors, and/or recalibrating the one or more PET detectors if one or more of the PET detectors are faulty.
12. The method of claim 11 , wherein recalibrating the one or more PET detectors occurs after pausing the delivery of radiation therapy.
13. The method of claim 1 , wherein extracting positron emission data comprises classifying positron emission data as originating from the calibration source or not originating from the calibration source.
14. The method of claim 13 , wherein classifying positron emission data uses reference time offsets and/or a spatial filter.
15. The method of claim 1 , further comprising measuring a temperature of the one or more PET detectors, and wherein determining whether a sensor is faulty further comprises determining whether the measured temperature exceeds a threshold value.
16. The method of claim 1 , further comprising identifying which of the one or more PET detectors is faulty and de-activating the faulty PET detector(s).
17. The method of claim 1 , wherein the fault signal comprises an interlock having a graphical user interface.
18. The method of claim 1 , further comprising de-activating up to three faulty PET detectors.
19. The method of claim 1 , further comprising de-activating all of the PET detectors if one or more PET detectors are determined to be faulty.