Semiconductor gamma-ray camera and medical imaging system

• US 6,080,984 A
• Filed: 09/09/1998
• Issued: 06/27/2000
• Est. Priority Date: 12/23/1994
• Status: Expired due to Term

• Current Assignee: Digirad Corporation
• Original Assignee: Digirad Corporation
• Inventors: Friesenhahn, Stanley J.
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Israel, Andrew
• Application Number:
  US09/150,520
• Time in Patent Office: 657 Days
• Field of Search: 250/363.07, 250/370.09, 250/363.09, 250/370.11, 250/252.1, 250/369, 250/363.05
• US Class Current: 250/252.1
• CPC Class Codes: A61B 6/037 Emission tomography
• CPC Class Codes: A61B 6/4258 for detecting non x-ray radiation, e.g. gamma radiation A61B6/037 takes precedence
• CPC Class Codes: G01T 1/161 Applications in the field of nuclear medicine, e.g. in vivo counting apparatus for radiation diagnosis A61B6/00
• CPC Class Codes: G01T 1/1642 using a scintillation crystal and position sensing photodetector arrays, e.g. ANGER cameras
• CPC Class Codes: G01T 1/243 Modular detectors, e.g. arrays formed from self contained units constructional or manufacturing details H01L25/00
• CPC Class Codes: G01T 1/247 Detector read-out circuitry for processing gain or off-set correction H04N
• CPC Class Codes: H01L 27/146 Imager structures
• CPC Class Codes: H01L 27/14658 X-ray, gamma-ray or corpuscular radiation imagers measuring X-, gamma- or corpuscular radiation G01T1/00
• CPC Class Codes: H01L 27/14676 X-ray, gamma-ray or corpuscular radiation imagers measuring X-, gamma- or corpuscular radiation G01T1/00
• CPC Class Codes: H04N 23/30 for generating image signals from X-rays
• CPC Class Codes: H04N 5/32 Transforming X-rays cameras or camera modules for generating image signals from X-rays H04N23/30; circuitry of SSIS for transforming X-rays into image signals H04N25/30

Abstract

A high-energy photon imaging system includes an imaging head, a signal processor, a data acquisition system and an image processing computer. The imaging head includes a detector that includes a plurality of closely-packed detection modules. Each detection module includes a plurality of detection elements mounted to a circuit carrier. The detection elements produce electrical pulses having amplitudes indicative of the magnitude of radiation absorbed by the detection elements. The circuit carrier includes channels for conditioning and processing the signals generated by corresponding detection elements and for preparing the processed signals for further processing by a signal processor. Each conditioning and processing channel stores the amplitudes of the detection element electrical pulses exceeding a predetermined threshold. The detection modules employ a fall-through circuit which automatically finds only those detection elements that have a stored pulse amplitude exceeding the threshold. The fall-through circuit searches for the next detection element and associated channel having a valid event. The signal processor performs diagnostics, gain normalization, and response efficiency normalization functions. The data acquisition system controls the acquisition and processing of data received from the conditioning and processing channels, produces image data based upon the data in a format that is compatible with existing imaging cameras, and transmits the data to the image processing computer. The image processing computer formulates images based upon the processed signals and displays the formulated images on a display device.

Claims

1. A signal processor for processing signals generated by a plurality of conditioning and processing channels, each channel operatively coupled to a corresponding detection element which produces electrical pulses indicative of an amount of energy associated with radiation quanta absorbed by the detection element, each channel storing an amplitude of the electrical pulse exceeding a predetermined threshold, and each channel generating an event whenever the electrical pulse exceeds a predetermined threshold, comprising:

a. means for sampling a stored amplitude of a channel generating an event;

b. means, operatively coupled with the sampling means, for normalizing gain introduced by the channel and the corresponding detection element, wherein the normalization means normalizes the sampled amplitude; and

c. means, coupled with the normalization means, for storing the normalized amplitude.

2. The signal processor of claim 1, wherein each detection element has a unique address, and wherein each channel generating an event transmits an address of the corresponding detection element to the signal processor, and wherein the signal processor further includes means, coupled to the sampling means, for reading the transmitted address.

3. The signal processor of claim 2, wherein the signal processor generates an advance signal after storing the normalized amplitude.

4. The signal processor of claim 2, wherein the signal processor further includes means, coupled to the sampling means, for tagging the transmitted address and normalized amplitude with a time-tag, and wherein the address, amplitude and time tag are stored together on a storage device coupled to the signal processor.

5. The signal processor of claim 4, wherein the addresses, amplitudes and time tags stored on the storage device are sorted into time bins related to an external event flag.

6. The signal processor of claim 1, wherein the normalization means includes:

a. an analog-to-digital converter having a reference input and an analog input, wherein the analog input is coupled to the sampled amplitude; and

b. means, coupled to the reference input, for storing a plurality of gain normalization factors, wherein each detection element has a corresponding pre-stored gain normalization factor, and wherein the storage means outputs a gain normalization factor of the detection element coupled to the channel generating the event to the reference input thereby causing the analog-to-digital converter to produce a normalized signal.

7. A method of normalizing electrical pulses generated by a plurality of detection elements, the electrical pulses indicative of an amount of energy associated with radiation quanta absorbed by the detection elements, comprising the steps of:

a. exposing the detection elements to a uniform radiation field;

b. generating a map of the efficiency of each detection element; and

c. normalizing the electrical pulses produced by each detection element based upon a peak location in an un-normalized peak height distribution.

8. A circuit for normalizing gain of signals produced by a plurality of processing channels, comprising:

a. an analog-to-digital converter having a reference input and an analog input, wherein the analog input is coupled to a signal produced by a selected channel; and

b. means, coupled to the reference input, for storing a plurality of gain normalization factors, wherein each channel has a corresponding pre-stored gain normalization factor, and wherein the storage means outputs a gain normalization factor corresponding to the selected channel to the reference input thereby causing the analog-to-digital converter to produce a gain-normalized signal.

9. The gain normalization circuit of claim 8, wherein the gain-normalized signals are produced in real-time.

10. A computer program, residing on a computer readable medium, for use in normalizing electrical pulses indicative of an amount of energy associated with radiation quanta absorbed by the detection elements, the computer program comprising executable instructions for causing a computer to:

a. generate a map of the efficiency of each detection element when the detection elements are exposed to a uniform radiation field; and

b. normalize the electrical pulses produced by each detection element based upon a peak location in an unnormalized peak height distribution.