Radiation detector and computer tomography apparatus including the same

1. A radiation detector which includes a plurality of pixels including a plurality of unit detectors configured to detect radiation, wherein each of the plurality of unit detectors comprises:

a radiation absorbing layer configured to convert incident photons into electric signals;

a plurality of comparators configured to compare each of the electric signals with a respective one of a plurality of reference values which have different values than each other, in order to classify the photons in a plurality of energy bands; and

a plurality of counters, which have different sizes than each other and are respectively and independently connected with the plurality of comparators, configured to count and store a respective number of photons that are classified in each of the plurality of energy bands, and

wherein a size of a first counter from among the plurality of counters is greater than a size of a second counter when a first reference value applied to a first comparator connected to the first counter from among the plurality of comparators is smaller than a second reference value applied to a second comparator connected to the second counter, and

wherein at least one pixel comprises a plurality of unit detectors divided into at least two sub-pixel groups, the at least two sub-pixel groups including a first sub-pixel group and a second sub-pixel group and a first image pixel value in a computed tomography (CT) image is generated based on the first sub-pixel group and a second image pixel value in the CT image is generated based on the second sub-pixel group.

2. The radiation detector of claim 1 , wherein the sizes of the plurality of counters vary inversely with respect to the corresponding plurality of reference values.

3. The radiation detector of claim 1 , wherein each of the plurality of counters has a first bit depth if an energy band in which the corresponding photons are classified is a low energy band, and a second bit depth that is less than the first bit depth if the energy band in which the corresponding photons are classified is a high energy band.

4. The radiation detector of claim 1 , wherein the respective size of each of the counters varies based on at least one from among the reference values, a type of radiation being detected by the radiation detector, and an energy band of a reconstruction energy of the radiation being detected by the radiation detector.

5. The radiation detector of claim 1 , wherein the radiation absorbing layer is disposed on a front portion of the radiation detector, and each of the plurality of comparators and each of the plurality of counters is disposed on a rear portion of the radiation detector.

6. The radiation detector of claim 1 , wherein the radiation absorbing layer is formed of at least one from among cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe).

7. A radiation detector comprising a plurality of pixels configured to detect radiation, wherein each of the plurality of pixels comprises a plurality of sub-pixels, and each of the plurality of sub-pixels comprises:

a radiation absorbing layer configured to convert incident photons into electric signals;

a plurality of comparators configured to compare the electric signals with a respective one of a plurality of reference values which have different values than each other, in order to classify the photons in a plurality of energy bands; and

a plurality of counters, which have different sizes than each other and are respectively and independently connected with the plurality of comparators, configured to count and store a respective number of photons that are classified in each of the plurality of energy bands, and

wherein a size of a first counter from among the plurality of counters is greater than a size of a second counter when a first reference value applied to a first comparator connected to the first counter from among the plurality of comparators is smaller than a second reference value applied to a second comparator connected to the second counter, and

wherein at least one pixel comprises a plurality of unit detectors divided into at least two sub-pixel groups, the at least two sub-pixel groups including a first sub-pixel group and a second sub-pixel group and a first image pixel value in a computed tomography (CT) image is generated based on the first sub-pixel group and a second image pixel value in the CT image is generated based on the second sub-pixel group.

8. A computed tomography (CT) apparatus comprising:

a radiation detector comprising a plurality of pixels, each of the plurality of pixels comprising a respective plurality of sub-pixels configured to detect radiation; and

an image processor configured to reconstruct a CT image based on a number of photons detected by the radiation detector,

wherein each of the each respective plurality of sub-pixels comprises:

a radiation absorbing layer configured to convert incident photons into electric signals;

a plurality of comparators configured to compare each of the electric signals with a respective one of a plurality of reference values which have different values than each other, in order to classify the photons in a plurality of energy bands; and

a plurality of counters, which have different sizes than each other and are respectively and independently connected with the plurality of comparators, configured to count and store a number of photons that are classified in each of the plurality of energy bands, and

wherein a size of a first counter from among the plurality of counters is greater than a size of a second counter when a first reference value applied to a first comparator connected to the first counter from among the plurality of comparators is smaller than a second reference value applied to a second comparator connected to the second counter, and

wherein the image processor is further configured to generate a first image pixel value in the CT image and a second image pixel value in the CT image by dividing a second plurality of sub-pixels included in at least one pixel into at least a first sub-pixel group and a second subpixel group, wherein the at least one pixel comprises a plurality of unit detectors divided into the at least first sub-pixel group and the second sub-pixel group, and wherein the first image pixel value is generated based on the first sub-pixel group and the second image pixel value is generated based on the second sub-pixel group.

9. The CT apparatus of claim 8 , wherein each of the at least two sub-pixel groups includes a plurality of sub pixels included in one pixel.

10. The CT apparatus of claim 8 , wherein each of the at least two sub-pixel groups includes a plurality of sub pixels included in at least two adjacent pixels.

11. A method for using a radiation detector which includes a plurality of pixels including a plurality of unit detectors configured to detect radiation to process detected radiation, each of the plurality of unit detector including a radiation absorbing layer, a plurality of comparators, and a plurality of counters, and the method comprising:

converting, by the radiation absorbing layer, incident photons into electric signals;

comparing, by the plurality of comparators, each of the electric signals with a respective one of a plurality of reference values which have different values than each other, in order to classify the photons in a plurality of energy bands; and

counting and storing, by the plurality of counters which have different sizes than each other and are respectively and independently connected with the plurality of comparators, a respective number of photons that are classified in each of the plurality of energy bands, and

wherein a size of a first counter from among the plurality of counters is greater than a size of a second counter when a first reference value applied to a first comparator connected to the first counter from among the plurality of comparators is smaller than a second reference value applied to a second comparator connected to the second counter, and

wherein at least one pixel comprises a plurality of unit detectors divided into at least two sub-pixel groups, the at least two sub-pixel groups including a first sub-pixel group and a second sub-pixel group and a first image pixel value in a computed tomography (CT) image is generated based on the first sub-pixel group and a second image pixel value in the CT image is generated based on the second sub-pixel group.

12. The method of claim 11 , wherein the comparing comprises:

using a first comparator to compare each of the electric signals with a first reference value;

using a second comparator to compare each of the electric signals with a second reference value; and

using a third comparator to compare each of the electric signals with a third reference value.

13. The method of claim 12 , wherein the counting and storing comprises:

using a first counter to count and store a number of photons which have energy values greater than the first reference value, based on a result of the comparison performed by the first comparator;

using a second counter to count and store a number of photons which have energy values greater than the second reference value, based on a result of the comparison performed by the second comparator; and

using a third counter to count and store a number of photons which have energy values greater than the third reference value, based on a result of the comparison performed by the third comparator.

14. A method for using a computed tomography (CT) apparatus to generate a CT image, the CT apparatus including a radiation detector which includes at least one unit detector configured to detect radiation, each of the at least one unit detector including a radiation absorbing layer, a plurality of comparators, and a plurality of counters, and the method comprising:

detecting, by the radiation detector, incident radiation; and

generating, by an image processor, the CT image based on a number of photons detected by the radiation detector,

wherein the detecting comprises:

converting, by the radiation absorbing layer, incident photons into electric signals;

comparing, by the plurality of comparators, each of the electric signals with a respective one of a plurality of reference values which have different values from each other, in order to classify the photons in a plurality of energy bands; and

counting and storing, by the plurality of counters which have different sizes than each other and are respectively and independently connected with the plurality of comparators, a respective number of photons that are classified in each of the plurality of energy bands, and

wherein a size of a first counter from among the plurality of counters is greater than a size of a second counter when a first reference value applied to a first comparator connected to the first counter from among the plurality of comparators is smaller than a second reference value applied to a second comparator connected to the second counter, and

wherein each of the at least one unit detector comprises a pixel, and the pixel includes a respective plurality of sub-pixels, and

wherein the generating the CT image comprises generating a first image pixel value in the CT image and a second image pixel in the CT image by dividing a corresponding plurality of sub-pixels into at least a first sub-pixel group and a second sub-pixel group, wherein the at least one pixel comprises a plurality of unit detectors divided into the at least first sub-pixel group and the second sub-pixel group, and wherein the first image pixel value is generated based on the first sub-pixel group and the second image pixel value is generated based on the second subpixel group.