Automatic air-calibration

1. A computed tomography system, the system comprising:

an x-ray source;

an x-ray detector;

a gantry configured to move the x-ray source and x-ray detector relative to an air space defined by a bore wherein the air space has a patient-receiving portion and an air-calibration portion and wherein the gantry is configured to move the x-ray source and the x-ray detector to the air-calibration portion during an air-calibration and to the patient receiving portion during scanning of the patient; and

a controller configured to automatically initiate the air-calibration using the x-ray source and x-ray detector with air in the air space and to determine gain values for channels of the x-ray detector from the automatically initiated air-calibration and wherein the controller is also configured to automatically initiate the air-calibration upon activation of the computed tomography system for scanning a patient.

2. The system of claim 1 wherein scanning parameters for the air-calibration are the same as scanning parameters for scanning the patient.

3. The system of claim 2 wherein the scanning parameters that are the same include x-ray source voltage, x-ray source focal spot, and/or x-ray filter.

4. The system of claim 1 wherein the controller is further configured to detect the presence of the patient in the patient-receiving portion and to automatically initiate the air-calibration based on the presence of the patient in the patient-receiving portion.

5. The system of claim 1 wherein the controller is further configured to automatically initiate the air-calibration while the patient is present in the patient-receiving portion and in response to activation to start the scanning of the patient, and

wherein the gain values from the air-calibration are used in scanning the patient.

6. The system of claim 1 , wherein the controller is further configured to receive a contextual measure, compare the contextual measure to a threshold, and to automatically initiate the air-calibration when the contextual measure exceeds the threshold.

7. The system of claim 6 , wherein the contextual measure is a measure of time, temperature, humidity, or location.

8. The system of claim 1 , wherein the computed tomography system is a mobile computed tomography system.

9. The system of claim 1 , further comprising:

x-ray blocking curtains movable between an open and closed position,

wherein the controller is further configured to cause the curtains to move to the closed position during the air-calibration.

10. A method of calibrating a computed tomography system having a patient bore, a controller, an x-ray source, and a detector, the method comprising:

receiving, by the controller, a setting for a medical scan to be performed by the computed tomography system for a particular patient, the setting being one of a plurality of optional values;

scanning air and not the patient in the patient bore with the x-ray source and the detector, the scanning using the setting;

determining, by the controller, a gain value based on the scanning with the setting and not the other optional values;

scanning the patient with the x-ray source and the detector using the setting and the gain value; and

moving the x-ray source and x-ray detector by a gantry to an air-calibration portion of the patient bore during the scanning of air and to a patient-receiving portion of the patient bore during scanning of the patient.

11. The method of claim 10 , wherein the setting is an x-ray source voltage, an x-ray source focal spot, and/or an x-ray filter.

12. The method of claim 10 , further comprising:

detecting the presence of the patient in the bore; and

initiating, by the controller, the air scanning and automatically determining the gain value based on the determined presence of the patient.

13. The method of claim 10 , further comprising:

receiving, by the controller, a contextual measure;

comparing, by the controller, the contextual measure to a threshold; and

initiating, by the controller, the air scanning and automatically determining the gain value when the contextual measure exceeds the threshold.

14. The method of claim 13 wherein the contextual measure is a measure of time, temperature, humidity, or location.

15. The method of claim 10 wherein the computed tomography system is a mobile computed tomography system.

16. The method of claim 10 , further comprising:

moving x-ray blocking curtains to a closed position during air scanning.

17. The method of claim 10 , wherein scanning the air and then scanning the patient are both performed in response to activation by a user of the computed tomography system for scanning the patient.

18. A method of calibrating a vehicle-dispatched mobile computed tomography system having a patient bore, an x-ray source, an x-ray detector, a gantry, and a controller, the method comprising:

moving, by the gantry, the x-ray source and the x-ray detector to an air-calibration portion of the patient bore during scanning of air and to a patient-receiving portion of the patient bore during scanning of a patient;

automatically initiating, by the controller, an air-calibration using the x-ray source and x-ray detector with air in the air-calibration portion; and

determining, by the controller, gain values for channels of the x-ray detector from the automatically initiated air-calibration.