FIELD OF THE INVENTION

The invention relates to large-area pixelated radiation detectors, in particular the present invention relates to a radiation detector.

BACKGROUND OF THE INVENTION

In recent years, new advanced X-ray and computed tomography, CT, applications are emerging, which require advanced imaging features such as spectral, also “multi-energy”, imaging, higher dynamic range and higher spatial resolution. Examples are for instance spectral CT, spectral X-ray, differential phase contrast imaging, DPCI, dark field X-ray, DAX, imaging, and so-called multi-modality XSPECT imaging, a complete integration of SPECT single photon emission computed tomography—and CT data during image reconstruction for sharp clinical detail and accurate measurement of disease.

Current X-ray and CT detectors have limited performance and cannot meet the required specification levels to enable these new applications at acceptable cost levels.

US 2002/054954 A1 describes a multidimensional detector array for detecting electromagnetic radiation, wherein a layer composite is produced, which has a sensor layer with a material sensitive to the radiation, and a carrier layer.

US 2010/0282972 A1 describes an indirect radiation detector for detecting radiation, the detector comprising: an array of pixels, each pixel being sub-divided into at least a first and a second sub-pixel, each sub-pixel having a cross-sectional area parallel to a surface plane of the array of pixels.

SUMMARY OF THE INVENTION

There may be a need to facilitate the design and manufacture the radiation conversion in indirect or direct conversion detectors.

This need is met by the subject-matter of the independent claims. Further exemplary embodiments are evident from the dependent claims and the following description.

A first aspect of the invention relates to a radiation detector comprising a substrate and a sensor, which is coupled to the substrate, the sensor comprising: —a first array of sensor pixels; —a second array of signal read-out elements; and —an electronic circuitry which is configured to provide image data based on signals received from the signal read-out elements.

The radiation detector further comprises a transducer, which is coupled to the substrate and to the sensor, the transducer comprising: a third array of subpixels, wherein at least two subpixels are assigned to one sensor pixel. The second array of signal read-out elements and the third array of subpixels correspond to each other, wherein each of the subpixels comprises a radiation conversion material.

The restriction that the second array of signal read-out elements and the third array of subpixels correspond to each other may be understood that the array correspond in size of the array as defined by the number of rows and columns that it contains.

The present invention advantageously uses the assembly concept of color display technologies for realization of (large-area) pixelated radiation detectors, i.e. replacing the flat panel display technology, as for instance realized by the so-called “microLED” by a radiation conversion material for X-ray/γ-ray detection and replacing the receiving substrate by a pixelated read-out sensor.

In the coming years the large display industry will rapidly develop the required process assembly technology and equipment for LED die (pick-and-place) transfer from donor substrates to receiving substrates.

Based on the present invention, medical detector suppliers can then easily re-use the developed microLED technologies to realize cost-effective manufacturing of multi-piece radiation detectors. A similar transfer of key enabling technologies occurred in the past for current a-Si and CMOS flat panel detectors, derived from respective displays, LCDs, and semiconductors, CMOS image sensors.

According to an embodiment of the invention, at least one of the signal read-out elements is a photodiode and the radiation conversion material of each of the subpixels is a scintillator; wherein a composition of the radiation conversion material and/or a thickness of the radiation conversion material is varied between at least two subpixels assigned to one sensor pixel.

According to an embodiment of the invention, the composition of the radiation conversion material to be varied between the at least two subpixels assigned to one sensor pixel is at least one of the following: i) a doping level of the radiation conversion material, ii) a doping material, and/or iii) a combination of doping materials.

According to an embodiment of the invention, the radiation conversion material is the radiation conversion material is caesium iodide, optionally doped with thallium, lutetium iodide, optionally doped with cerium, gadolinium oxysulfide, optionally doped with terbium or optionally doped with praseodymium, calcium tungstate, lutetium-yttrium oxyorthosilicate, sodium iodide, zinc sulfide, scintillating garnet materials such as lutetium gadolinium gallium garnet, yttrium aluminum garnet, or bismuth germanium oxide.

According to an embodiment of the invention, at least one of the signal read-out elements is a conductive electrode and the radiation conversion material of each of the subpixels is a photoconductor, wherein a composition of the photoconductor and/or a thickness the photoconductor is varied between at least two subpixels assigned to one sensor pixel.

According to an embodiment of the invention, the composition of the photoconductor to be varied between the at least two subpixels assigned to one sensor pixel is at least one of the following: i) a doping level of the photoconductor ii) a doping material, and/or iii) a combination of doping materials.

According to an embodiment of the invention, the photoconductor is at least one of the following: i) amorphous selenium, ii) cadmium zinc telluride, iii) cadmium telluride, iv) perovskite, v) gallium arsenide, vi) mercury(II)iodide, vii) lead(II) oxide, viii) thallium(I) bromide, and ix) inorganic photoconductor nanoparticles embedded in an organic matrix.

According to an embodiment of the invention, the at least two subpixels assigned to one sensor pixel are subpixels with different dimension and/or different size and/or different distance gaps and/or different radiation conversion materials and/or different material composition between the subpixels.

According to an embodiment of the invention, the third array comprises a non-uniform distribution of the different dimension of the subpixels and/or the different size of the subpixels and/or the different distance gaps and/or the different radiation conversion materials of the subpixels and/or the different material composition between the subpixels.

For example, according to an embodiment of the invention the non-uniform distribution of subpixels may be provided by a non-uniform distribution of the composition and/or the thickness of the used radiation conversion material.

According to an embodiment of the invention, a thicker scintillator may be provided in a center region of the pixel, and a in comparison to the thicker thinner scintillator may be provided in any non-center, e.g. any periphery region of the detector.

According to an embodiment of the invention, a high-quality, expensive scintillator, for example CsI, may be provided in a center region of the pixel, and lower quality, cheap scintillator, for example GOS, may be provided in any non-center, e.g. any periphery region of the detector.

For example, according to an embodiment of the invention the non-uniform distribution of subpixels may be provided by a non-uniform distribution of level of subpixel binning, for example 4×4, 3×3, 2×2 or 1×1 binning from a center region towards a periphery of detector.

According to an embodiment of the invention, this may be achieved by using equal pixel size across the complete detector area.

According to an embodiment of the invention, an increase of pixel size from center towards periphery may be provided. This advantageously results in high spatial resolution in center and lower resolution at periphery, while saving material costs of electronics compared to a detector with 4×4 subpixel binning across complete area.

According to an embodiment of the invention, the first array of sensor pixels and/or the second array of signal read-out elements and/or the third array of subpixels is a two-dimensional array.

According to an embodiment of the invention, the first array of sensor pixels and/or the second array of signal read-out elements and/or the third array of subpixels is a one-dimensional array.

According to an embodiment of the invention, the second array of signal read-out elements and/or the third array of subpixels define a subarray scheme of the first array of sensor pixels. In other words, at least a small portion in a center region of the detector is provided with subpixels.

According to an embodiment of the invention, the second array of signal read-out elements and/or the third array of subpixels are configured to provide a spatial resolution, a spectral energy resolution, or a dynamic range or a spectral energy range.

According to an embodiment of the invention, the substrate comprises a flat or a substantially flat or a curved shape. The term “substantially flat” as used by the present invention may refer to a flatness comprising a minimum bend radius of up to 1 cm.

According to an embodiment of the invention, the substrate comprises silicon, glass or polymer foil.

Further embodiments of the invention are provided in the description for explanatory purpose. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

