Optimized signal detection by quantum-counting detectors
A method is described for setting the detection of a macropixel signal of an x-ray detector with a plurality of pixels, each combined to form at least one macropixel. The geometrical efficiency and the signal drift factor of the individual pixels are first established. A target drift value is established. A parameter, which sets a compromise between an allowed drift of the macropixel signals and the achievable dose efficiency, is also defined. Based on the established parameters, the weighting of the individual pixel signals, taking into account a function taking account of the signal drift and the dose utilization of the resulting macropixel signal depending on the weightings of the pixel signals, is established. A weighted addition of the individual pixel signals to form macropixel signals is defined on the basis of the weightings. A signal detection device, an x-ray detector and a computed tomography system are also described.
1. A method for generating a reconstructed image of a region of a patient based on macropixel signals of an x-ray detector including a plurality of pixels, each of the plurality of pixels combined into at least one macropixel, the method comprising:
establishing weightings of individual pixel signals from the plurality of pixels as a function of signal drift factors for the individual pixel signals, a target drift value for a resulting macropixel signal, dose utilization of the resulting macropixel signal and a geometrical efficiency of the plurality of pixels;
generating the macropixel signals according to weighted sums of the individual pixel signals using the established weightings; and
generating the reconstructed image of the region of the patient based on the generated macropixel signals.
2. The method of claim 1 , wherein the target drift value is zero.
3. A non-transitory computer readable medium, loadable directly into a memory of a computed tomography system, including program code sections for out carrying the method of claim 2 .
4. The method of claim 1 , wherein the function is formulated as:
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wherein e i is the geometrical efficiency of the plurality of pixels, d i is a signal drift factor, and t is the target drift value, λ is a user-defined value indicative of a compromise between an allowed signal drift of the generated macropixel signals and an achievable dose efficiency, ω i represents the weightings of the individual pixel signals and l specifies the number of pixels combined to form a macropixel.
5. The method of claim 1 , further comprising:
detecting the individual pixel signals from the plurality of pixels; and
combining the detected individual pixel signals by weighted addition of the detected individual pixel signals with the aid of the established weightings, to generate the macropixel signals.
6. A non-transitory computer readable medium, loadable directly into a memory of a computed tomography system, including program code sections for carrying out the method of claim 5 .
7. A non-transitory computer readable medium, loadable directly into a memory of a computed tomography system, including program code sections for carrying out the method of claim 1 .
8. An image reconstruction device for reconstructing an image of a region of a patient based on macropixel signals of an x-ray detector including a plurality of pixels, each of the plurality of pixels combined to form at least one macropixel, the image reconstruction device comprising:
at least one processor configured to execute computer-readable instructions to
establish weightings of individual pixel signals from the plurality of pixels of the x-ray detector as a function of signal drift factors for the individual pixel signals, a target drift value for a resulting macropixel signal, dose utilization of the resulting macropixel signal and a geometrical efficiency of the plurality of pixels;
generate the macropixel signals by performing weighted addition of the individual pixel signals using the established weightings; and
generate the reconstructed image of the region of the patient based on the generated macropixel signals.
9. An x-ray detector comprising the image reconstruction device of claim 8 .
10. The x-ray detector of claim 9 , wherein the at least one macropixel includes a group of 9 or 16 individual pixels.
11. A computed tomography system comprising the x-ray detector of claim 10 .
12. A computed tomography system comprising the x-ray detector of claim 9 .