Photon counting cone-beam CT apparatus with monolithic CMOS integrated pixel detectors
CBCT including monolithic photon counting FPD for medical applications requiring real-time 3D imaging, like mammography, interventional guided procedures or external beam radiotherapy, includes CMOS processed readout electronics monolithically integrated with a single crystalline X-ray absorber by covalent wafer bonding near room temperature and adapted for single photon counting providing high energy, temporal and spatial resolution.
1. A cone beam computer tomography (CBCT) system, comprising
a. at least one X-ray source, and a monolithic flat panel detector (FPD) disposed for the direct detection of X-ray radiation comprising at least one buttable monolithic detector comprising a covalent wafer bond between at least one absorber wafer made from single crystal material and a backside of at least one thin CMOS processed readout wafer configured so that the backside of the at least one readout wafer faces the radiation, the readout wafer comprising on its front side a readout unit communicating with implanted charge collectors on its front side defining a pixel size L wherein the implanted charge collectors are disposed to collect electric charges generated by X-rays incident on the at least one absorber wafer and drifting along electric field lines towards the charge collectors when the detector is in operation and wherein electrical signals induced by the charges are amplified, shaped and transformed into digital signals in the readout unit, and
b. one or more devices providing data collection, computation and/or storage functionality, arranged and connected to receive the digital electrical signals from the readout unit of the FPD and to generate computed tomography images on at least one computer screen.
2. The system of claim 1 , wherein the at least one X-ray source and the FPD are mounted on a C-arm permitting interventional radiology.
3. The system of claim 1 , wherein the at least one X-ray source and the FPD are mounted on a C-arm permitting 3D imaging for mammography.
4. The system of claim 1 , wherein the FPD and the one or more devices providing data collection are configured to provide photon counting capability to permit energy resolved single photon counting.
5. The system of claim 1 , wherein the at least one thin readout wafer has a thickness of 10-100 μm.
6. The system of claim 1 , wherein the at least one thin readout wafer has a thickness of 10-20 μm.
7. The system of claim 1 , wherein the monolithic FPD comprises an oxide-free covalent wafer bond between the at least one absorber wafer and the backside of the at least one CMOS processed readout wafer.
8. The system of claim 1 , wherein the FPD comprises buttable tiles and wherein the FPD comprises an area of at least 20×20 cm 2 .
9. The system of claim 8 , wherein the spacing between buttable tiles is in the range of 50-100 μm.
10. The system of claim 1 , wherein the FPD is adapted to provide a spatial resolution in the range of 100-200 μm.
11. The system of claim 1 , wherein the FPD is adapted to provide a spatial resolution in the range of 50-100 μm.
12. The system of claim 1 , wherein the FPD is adapted to provide a spatial resolution in the range of 20-50 μm.
13. The system of claim 1 , wherein the at least one X-ray source, FPD and the one or more devices providing data collection, computation and/or storage functionality are adapted for use in one of a group of applications consisting of projection radiography, mammography and interventional radiology.
14. The system of claim 1 , wherein the at least one X-ray source, FPD and the one or more devices providing data collection, computation and/or storage functionality are adapted for use in mammography.
15. The system of claim 1 , wherein the absorber wafer comprises at least one element with an atomic number larger than that of Si.
16. The system of claim 1 , wherein the absorber wafer is made from at least one of a group of absorber materials consisting of Si, Si 1-x Ge x alloys with Ge fractions 0≤x≤1, GaAs, CdTe, and Cd 1-x Zn x Te with x of about 10%.
17. The system of claim 1 , wherein the absorber wafer is made from a Si 1-x Ge x alloy with a Ge fraction of 0≤x≤1.
18. The system of claim 17 , wherein the absorber wafer comprises a 100-200 μm thick epitaxial layer on a Si substrate.
19. The system of claim 1 , wherein the absorber wafer is made from a Si 1-x Ge x alloy with a Ge fraction of 0.6≤x≤0.8.
20. The system of claim 19 , wherein the absorber wafer comprises a 100-200 μm thick epitaxial layer on a Si substrate.
21. The system of claim 1 , wherein the at least one thin CMOS processed readout wafer comprises implants on a front surface configured to receive the analog electrical signals generated by absorbed X-ray photons in the at least one absorber wafer, and wherein further circuitry amplifies, shapes and transforms these electrical signals into digital signals to be further processed in the one or more devices providing data collection, computation and/or storage functionality to be displayed as a computed tomography image on at least one computer screen.
22. A method for performing cone beam computer tomography (CBCT), the method comprising steps of
a. providing at least one X-ray source;
b. forming a monolithic FPD by covalently bonding at least one single crystal absorber wafer to at least one CMOS processed readout wafer;
c. disposing the FPD and at least one device providing data collection, computation and storage functionality to provide single-photon counting capability;
d. with the at least one X-ray source and the FPD mounted on a C-arm and a patient positioned in an appropriate operation position, activating the at least one readout wafer to communicate with the at least one device providing data collection, computation and storage functionality;
e. disposing the at least one device to receive electrical signals from the FPD, and
f. scanning the patient; and
g. generating computed tomography images on at least one computer screen.