Photon-counting X-ray CT apparatus and photon-counting imaging method
View Patent ↗A photon-counting X-ray CT apparatus in an embodiment includes an X-ray tube, an X-ray detector, correction circuitry, and processing circuitry. The X-ray tube is configured to irradiate a subject with X-rays. The X-ray detector is configured to include an X-ray detection element that detects photons of the X-rays that the X-ray tube emits. The correction circuitry is configured to correct a count value observed by the X-ray detection element in each of a plurality of energy bins, based on at least one of the probability of escape in the X-ray detection element and the probability of crosstalk in the X-ray detection element. The processing circuitry is configured to generate a reconstruction image, based on the count values corrected by the correction circuitry.
1. A photon-counting X-ray CT apparatus comprising:
an X-ray tube configured to irradiate a subject with X-rays;
an X-ray detector including an X-ray detection element configured to detect photons of the X-rays and to convert the photon into an electrical signal;
data collection circuitry configured to collect a count value by counting a number of electrical signals in each of a plurality of energy bins output by the X-ray detection element;
correction circuitry configured to determine a true count value for each X-ray detection element in each of the plurality of energy bins, based on at least one of probability of escape in the X-ray detection element and probability of crosstalk in the X-ray detection element; and
processing circuitry configured to generate a reconstruction image, based on the true count value.
2. The photon-counting X-ray CT apparatus according to claim 1 , wherein
the energy bins include a first energy bin that includes first energy and a second energy bin that includes second energy and is lower than the first energy bin, and
the correction circuitry is configured to determine a true count value of the first energy bin and a true count value of the second energy bin by using the determined true count value of the first energy bin.
3. The photon-counting X-ray CT apparatus according to claim 1 , wherein
the X-ray detector includes a plurality of such X-ray detection elements, and
the correction circuitry is configured to determine a true count value for each of the X-ray detection elements.
4. The photon-counting X-ray CT apparatus according to claim 2 , wherein
the X-ray detector includes a plurality of X-ray detection elements, and
the correction circuitry is configured to determine a true count value for each of the X-ray detection elements.
5. The photon-counting X-ray CT apparatus according to claim 3 , wherein the probability of escape includes at least one of probability in which a photon having entered the X-ray detection element is not counted in an energy bin that includes energy of the photon by escape and probability in which the photon having entered the X-ray detection element is counted in one energy bin other than the energy bin that includes energy of the photon by escape.
6. The photon-counting X-ray CT apparatus according to claim 3 , wherein the probability of crosstalk is probability in which a photon having entered an X-ray detection element other than the X-ray detection element a true count value of which is determined, out of the X-ray detection elements enters the X-ray detection element the true count value of which is determined, by crosstalk and is counted in an energy bin including energy the photon has at time of entering the X-ray detection element the true count value of which is determined.
7. The photon-counting X-ray CT apparatus according to claim 5 , wherein the probability of crosstalk is probability in which a photon having entered an X-ray detection element other than the X-ray detection element a true count value of which is determined, out of the X-ray detection elements enters the X-ray detection element the true count value of which is determined, by crosstalk and is counted in an energy bin including energy the photon has at time of entering the X-ray detection element the true count value of which is determined.
8. The photon-counting X-ray CT apparatus according to claim 6 , wherein the correction circuitry is configured to use a result of the probability of crosstalk calculated on at least one of the other X-ray detection elements in advance when determining the true count value.
9. The photon-counting X-ray CT apparatus according to claim 7 , wherein the correction circuitry is configured to use a result of the probability of crosstalk calculated on at least one of the other X-ray detection elements in advance when determining the true count value.
10. The photon-counting X-ray CT apparatus according to claim 8 , wherein the correction circuitry is configured to use a result of the probability of crosstalk calculated in advance on the other X-ray detection element that is in a predetermined positional relation with the X-ray detection element as the result when determining the true count value.
11. The photon-counting X-ray CT apparatus according to claim 9 , wherein the correction circuitry is configured to use a result of the probability of crosstalk calculated in advance on the other X-ray detection element that is in a predetermined positional relation with the X-ray detection element as the result when determining the true count value.
12. The photon-counting X-ray CT apparatus according to claim 8 , wherein the correction circuitry is configured to reduce number of other X-ray detection elements that are used for the result when determining the true count value in response to an increase in number of energy bins.
13. The photon-counting X-ray CT apparatus according to claim 9 , wherein the correction circuitry is configured to reduce number of other X-ray detection elements that are used for the result when determining the true count value in response to an increase in number of energy bins.
14. The photon-counting X-ray CT apparatus according to claim 8 , wherein the correction circuitry is configured to use the result on only the other X-ray detection elements for which the probability of crosstalk is equal to or higher than a predetermined threshold when determining the true count value.
15. The photon-counting X-ray CT apparatus according to claim 9 , wherein the correction circuitry is configured to use the result on only the other X-ray detection elements for which the probability of crosstalk is equal to or higher than a predetermined threshold when determining the true count value.
16. The photon-counting X-ray CT apparatus according to claim 8 , wherein the correction circuitry is configured to reduce number of other X-ray detection elements that are used for the result when determining the true count value in response to a decrease in a speed of correction.
17. The photon-counting X-ray CT apparatus according to claim 1 , wherein at least one of the probability of escape and the probability of crosstalk is obtained by actual measurement.
18. The photon-counting X-ray CT apparatus according to claim 1 , wherein at least one of the probability of escape and the probability of crosstalk is obtained by simulation.
19. The photon-counting X-ray CT apparatus according to claim 18 , wherein the simulation is performed considering at least one of size, shape, and position of the X-ray detection element in the X-ray detector.
20. A photon-counting imaging method comprising:
collecting, by data collection circuitry, a count value by counting a number of electrical signals in each of a plurality of energy bins output by X-ray detection element, the X-ray detection element being configured to detect photons of X-rays and to convert the photons into the electrical signals;
determining, by correction circuitry, a true count value for each X-ray detection element in each of the plurality of energy bins, based on at least one of probability of escape in the X-ray detection element and probability of crosstalk in the X-ray detection element; and
generating, by processing circuitry, a reconstruction image, based on the true count value.