X-ray CT apparatus with adaptive photon counting detectors
An embodiment of a computed tomography apparatus includes an x-ray source and scan control circuitry configured to control the x-ray source to expose a subject with x-rays over a scan having a plurality of views. A detector is disposed to receive x-rays from the x-ray source, has a plurality of anodes arranged in groups, and a common conductive strip between the anodes. Photon counting circuits are respectively provided for each of the anodes and have adjustable operating parameters. Connection circuitry is configured to adaptively connect, in a first mode, each anode to one of the photon counting circuits and, in a second mode, each anode in a group to a same one of the photon counting circuits. Processing circuitry, connected to the connection circuitry and the photon counting circuits, is configured to, for each of the views, select the first mode or the second mode and adjust the operating parameters based upon exposure data obtained from exposing the subject with the x-rays from the x-ray source.
1. A computed tomography apparatus, comprising:
an x-ray source;
scan control circuitry configured to control the x-ray source to expose a subject with x-rays over a scan having a plurality of views;
a detector disposed to receive x-rays from the x-ray source and having plurality of anodes arranged in groups;
photon counting circuits respectively provided for each of the anodes and having adjustable operating parameters;
connection circuitry configured to adaptively connect, in a first mode, each anode to one of the photon counting circuits and, in a second mode, each anode in a group to a same one of the photon counting circuits; and
processing circuitry, connected to the connection circuitry and the photon counting circuits, configured to, for each of the views, select the first mode or the second mode and adjust the operating parameters based upon exposure data obtained from exposing the subject with the x-rays from the x-ray source.
2. The computed tomography apparatus according to claim 1 , wherein:
scan control circuitry configured to control the x-ray source to expose the subject with the x-rays over the scan, the scan including a first exposure before a second exposure; and
the processing circuitry is configured to select the first mode or second and adjust the operating parameters based upon the first exposure.
3. The computed tomography apparatus according to claim 2 , wherein:
the first exposure has a duration and an x-ray exposure level each less than that of the second exposure.
4. The computed tomography apparatus according to claim 2 , wherein:
each of the photon counting circuits is configured to determine a number of photons and an energy distribution of the photons for a corresponding anode during the first exposure.
5. The computed tomography apparatus according to claim 2 , wherein:
the processing circuitry comprises:
a processor, and
a storage containing mode data and operating parameter data as a function of x-ray flux and energy;
the processor is configured to compare data from the first exposure of the scan with data in the storage to select the first mode or the second mode and adjust the operating parameters; and
the scan control circuitry is configured to control the x-ray source to expose the subject with x-rays during the second exposure of the scan using the selected mode and adjusted operating parameters from the comparison based upon the data from first exposure of the scan.
6. The computed tomography apparatus according to claim 5 , wherein the storage is a look up table.
7. The computed tomography apparatus according to claim 1 , wherein the processing circuitry is configured to:
generate exposure data; and
process the exposure data to increase spatial uniformity.
8. The computed tomography apparatus according to claim 7 , where the processing circuitry is configured to down-sample data collected from the anodes connected to one of the photon counting circuits and up-sample data connected from anodes connected in the group.
9. The computed tomography apparatus according to claim 1 , wherein the photon counting circuitry comprises:
a charge sensitive preamplifier which outputs a pulse signal having a shape and a width; and
shaping circuitry configured to adjust at least one of the shape and width of the pulse signal.
10. The computed tomography apparatus according to claim 9 , wherein the processing circuitry is configured to adjust at least one of an integration time of the charge sensitive preamplifier and a pulse width of the shaping circuitry based upon the exposure data.
11. The computed tomography apparatus according to claim 9 , wherein the shaping circuitry is configured to adjust at least one of the shape and width of the pulse signal based upon at least one of x-ray energy and flux.
12. The computed tomography apparatus according to claim 1 , comprising a common conductive strip disposed between the anodes having a lower applied voltage that that of the anodes.
13. A photon counting computed tomography method, comprising:
exposing a subject with x-rays over a scan having a plurality of views, each of the views having a first exposure period before a second exposure period;
determining an energy distribution of x-ray received during the first exposure period using photon counting circuitry and a detector having a plurality of anodes arranged in groups, for each of the plurality of views;
selecting a number of anodes in each group and operating parameters of the photon counting circuitry based upon the x-rays received during the first exposure period; and
exposing the subject during the second period based upon the selected number of anodes and operating parameters.
14. The photon counting computed tomography method according to claim 13 , wherein said first exposure period has a duration and an x-ray exposure level each less than that of the second exposure period.
15. The photon counting computed tomography method according to claim 13 , comprising:
comparing the energy distribution to mode data and operating parameter data stored as a function of x-ray flux and energy; and
selecting the number of anodes in each group and the operating parameters of the photon counting circuitry based upon the comparing.
16. The photon counting computed tomography method according to claim 13 , comprising:
exposing the subject to a level of x-rays during the first period designed to sense x-ray flux and energy of the view; and
exposing the subject to a level of x-rays during the second period designed to generate image data of the view.
17. The photon counting computed tomography method according to claim 13 , comprising:
generating exposure data from exposing the subject during the second exposure period; and
processing the exposure data to increase spatial uniformity.
18. The photon counting computed tomography method according to claim 13 , comprising:
down-sampling data collected from the anodes connected to one of the photon counting circuitry; and
up-sampling data collected from the anodes connected as a group to the photon counting circuitry.
19. The photon counting computed tomography method according to claim 13 , wherein the photon counting circuitry comprises:
a charge sensitive preamplifier which outputs a pulse signal having a shape and a width; and
shaping circuitry configured to adjust at least one of the shape and width of the pulse signal, the method comprising:
adjusting at least one of an integration time of the charge sensitive preamplifier and a pulse width of the shaping circuitry based upon the exposure data.
20. The photon counting computed tomography method according to claim 13 , comprising:
disposing a common electrode strip between the anodes in a group; and
applying a voltage to the strip less than that applied to the anodes.