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US 9,753,160 B2Granted
Digital X-ray sensor
OwnerRonaldo Bellazziniinventor
Life of this patent
Estimating the term…
Abstract
A digital X-ray sensor having a detection layer, and a collection layer formed by pixels in the form of a CMOS ASIC, wherein the sensor is provided with a “photon-counting” function and is suitable for radiological applications, so that the best arrangement is obtained between the image quality and the radiation dose absorbed by a subject.
Claims28
A digital X-ray sensor (100) comprising:
- a semiconductor conversion layer (10), configured for receiving X-ray photons (2) and for converting said X-ray photons (2) into an electric charge (14);
- a semiconductor collection layer (20) integrated with said conversion layer (10), said collection layer (20) formed by a plurality of collection pixels (22) that are arranged in a predetermined pattern, each collection pixel (22) of said collection layer (20) configured for receiving electrons (16) of said electric charge (14) from said conversion layer (10);
- a data output means (213) for transferring data collected by said collection pixels (22) to an acquisition electronics (50);
- wherein each collection pixel (22) comprises:
- an amplification means (203) arranged for receiving said electric charge as an inlet charge, which comprises said electrons (16) produced by said conversion layer (10), said amplification means (203) configured for generating a voltage signal (17) that has a peak value (21) proportional to said inlet electric charge (16);
- a plurality of N window discriminators (24i), each discriminator (24i) comprising a plurality of CMOS transistors, each discriminator (24i) configured for:
- carrying out a comparison between said peak value (21) and two charge threshold values (25i, 25i+1) comprising a lower threshold value (25i) and an upper threshold value (25i+1), and
- carrying out an instantaneous transition between a 0-level and an 1-level if:
- said peak value (21) is higher than said lower threshold value (25i), and
- said peak value (21) is lower than said upper threshold value (25i+1);
- wherein, for each discriminator (24i), at least one condition occurs that is selected between:
- said upper threshold value (25i+1) is lower than said lower threshold value of at least one of said discriminators (24k,k≠i) distinct from said each discriminator (24i), in particular said upper threshold value (25i+1) is equal to said lower threshold value of said at least one of said discriminators (24k,k≠i) distinct from said each discriminator (24i);
- said lower threshold value (25i) is higher than said lower threshold value of at least one of said discriminators (24k,k≠i) distinct from said each discriminator (24i), in particular said lower threshold value (25i) is equal to said upper threshold value of said at least one of said discriminators (24k,k≠i) distinct from said each discriminator (24i),
- wherein each collection pixel (22) comprises a plurality of N counters (26i), each of said counters (26i) associated with a respective discriminator of said discriminators (24i),
- wherein each counter (26i) is configured to increase by 1 unit a value of an own counting if:
- said peak value (21) is higher than said lower threshold value (25i) of said respective discriminator (24i), and
- said peak value (21) is lower than said upper threshold value (25i+1) of said respective discriminator (24i),
- while said counters (26k,k≠i) distinct from said each counter (26i) are configured for keeping unchanged an own count value,
- wherein said data output means (213) is configured for receiving from said counters (26i) of each collection pixel (22) measurement data of the radiation (2) incident in N “colours” corresponding to the counts stored in N energy windows for each charge threshold,
- characterized in that it comprises:
- a digital-to-analog converter (DAC) (28i) for at least one discriminator (24i) of each collection pixel (22), said digital-to-analog converter (28i) configured for receiving combinations of a predetermined number of bits and for generating current values corresponding to said combinations of bits;
- a current supply means (206) for supplying a current to each collection pixel (22), configured for supplying a current to said amplification means (203) responsive to said combinations of bits of said at least one discriminator (24i);
- a logical means (34) resident in each of said collection pixels (22), configured for determining an offset correction current value, said logical means configured for carrying out a calibration step within each collection pixel in order to establish which combination of bits of said combinations of bits of said or each digital-to-analog converter (28i) has to be used for supplying said correction current, said calibration step preliminarily carried out in each pixel by said logical means (34) at the same time for all said collection pixels (22),
- wherein each of said collection pixels (22) comprises a memory unit (35) of said offset correction current value;
- and wherein said logical means (34) is also configured for storing said correction current value into said memory unit (35).
22 more elements
A radiographic imaging method by an X-ray sensor (100), said method comprising:
- irradiating a semiconductor conversion layer (10) with X-ray photons (2) and converting said X-ray photons (2) into an electric charge (14) by said conversion layer (10);
- prearranging a semiconductor collection layer (20) integrated with said conversion layer (10), said collection layer (20) formed by a plurality of collection pixels (22) that are arranged in a predetermined pattern;
- receiving electrons (16) of said electric charge (14) from said conversion layer (10) by each collection pixel (22) of said collection layer (20);
- amplifying (203) said electric charge in each collection pixel (22), and producing a voltage signal (17) that has a peak value (21) proportional to said electric charge (16);
- discriminating said peak value in each collection pixel (22) by a plurality of N window discriminators (24i), each discriminator (24i) comprising a plurality of CMOS transistors, wherein each discriminator (24i):
- performs a comparison between said peak value (21) and two charge threshold values (25i, 25i+1) comprising a lower threshold value (25i) and a upper threshold value (25i+1), and
- performs an instantaneous transition between a 0-level and a 1-level if:
- said peak value (21) is higher than said lower threshold value (25i), and
- said peak value (21) is lower than said upper threshold value (25i+1);
- wherein, for each discriminator (24i) at least one condition occurs selected between:
- said upper threshold value (25i+1) is lower than said lower threshold value of at least one of said discriminators (24k,k≠i) distinct from said each discriminator (24i), in particular said upper threshold value (25i+1) is equal to said lower threshold value of said at least one of said discriminators (24k,k≠i) distinct from said each discriminator (24i);
- said lower threshold value (25i) is higher than said lower threshold value of at least one of said discriminators (24k,k≠i) distinct from said each discriminator (24i), in particular said lower threshold value (25i) is equal to said upper threshold value of said at least one of said discriminators (24k,k≠i) distinct from said each discriminator (24i);
- counting, in each collection pixel (22), the peak values discriminated at each discriminator by means of a plurality of N counters (26i), each of said counters (26i) associated with a respective discriminator of said discriminators (24i),
- wherein said counting in each counter (26i) is carried out by increasing a value of an own counting by 1 unit, if:
- said peak value (21) is higher than said lower threshold value (25i) of said respective discriminator (24i) and
- said peak value (21) is lower than said upper threshold value (25i+1) of said respective discriminator (24i),
- while said counters (26k,k≠i) distinct from said each counter (26i) maintain unchanged an own count value,
- acquiring, by a data output means (213), data collected by said collection pixels (22) for transmitting said data to an acquisition electronics (50);
- characterized in that it comprises:
- prearranging a digital-to-analog converter (DAC) (28i) for at least one discriminator (24i) of each collection pixel (22), said converter configured for receiving combinations of a predetermined number of bits and for generating current values corresponding to said combinations of bits;
- supplying a correction current (206) to said amplification means (203) of each of said collection pixels (22), said current supplied responsive to said combinations of bits of said at least one discriminator (24i);
- and in that it also comprises a calibration step carried out within each collection pixel in order to establish which combination of bits of said combinations of bits of said or each digital-to-analog converter (28i) has to be used for supplying said correction current, said calibration step carried out preliminarily in each pixel by a logical means (34) that is resident in each of said collection pixels (22);
- wherein said calibration step is carried out within each collection pixel at the same time for all said collection pixels (22).
20 more elements
Dependencies are inferred from the claim text.