Radiological imaging apparatus and method

• US 6,904,126 B2
• Filed: 06/18/2003
• Issued: 06/07/2005
• Est. Priority Date: 06/19/2002
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Endo, Tadao
• Primary Examiner(s): Church, Craig E.
• Assistant Examiner(s): Kiknadze, Irakli
• Application Number:
  US10/464,039
• Publication Number:
  US 20040017891A1
• Time in Patent Office: 720 Days
• Field of Search: 378/98.8, 378/98.7, 378/98.11, 378/98.12, 378/108, 378/19, 250/370.09
• US Class Current: 378/98.8
• CPC Class Codes: A61B 6/583 using calibration phantoms
• CPC Class Codes: A61B 6/585 Calibration of detector units
• CPC Class Codes: G01N 2223/419 computed tomograph
• CPC Class Codes: G01N 23/04 and forming images of the material
• CPC Class Codes: G01N 23/046 using tomography, e.g. computed tomography [CT]

Abstract

A radiological imaging apparatus and method corrects fixed pattern noise (FPN) generated within the apparatus and suppresses increases in random noise attendant upon FPN correction to provide radiological imaging having improved reliability and image quality. The apparatus has a signal processing circuit that digitizes analog output from a read-out circuit, four FPN memories for storing four dark outputs, a light memory for storing a light output after X-ray exposure of a subject, a CPU for controlling the signal processing circuit as well as FPN and light memories, and a shift resister 7 controlled by the CPU. The method involves averaging multiple dark outputs and subtracting the FPN data average so obtained from the light output which includes the X-ray imaged to enhance picture quality. Since the FPN correction uses FPN data that has been averaged over multiple dark outputs, the method also suppresses random noise generated by the FPN correction for enhanced imaging accuracy.

Claims

1. A radiological imaging apparatus for forming X-ray images, comprising:

a radiation detection unit composed of a plurality of photoelectric converters arrayed in a matrix-like formation for the purpose of detecting and converting radiation from an irradiated subject into electrical signals;

a drive control unit operatively connected to said radiation detection unit for the purpose of controlling movement of said radiation detection unit;

a read-out unit operatively connected to said radiation detection unit for reading the electrical signals output by said radiation detection unit; and

a signal processing unit operatively connected to said read-out unit and said drive control unit for processing the electrical signals read out by the read-out unit,

said signal processing unit selecting between a first read-out operation, in which the radiation detection unit is operated with irradiation of a subject, and a second read-out operation, in which the radiation detection unit is operated without irradiation of the subject,

said signal processing unit further performing said second read-out operation at least twice, averaging the results of said second read-out operation so as to obtain an average signal value thereof, and subtracting said average signal value from a signal value obtained by said first read-out operation so as to obtain a processed image.

2. The radiological imaging apparatus of claim 1, wherein the signal processing unit comprises a first storage unit for storing electrical signals output from said first read-out operation and a second storage unit for storing electrical signals output by said second read-out operation.

3. The radiological imaging apparatus of claim 1, wherein the radiation detection unit further comprises a wavelength converter for converting said radiation into visible light and a photoelectric converter for detecting and converting said visible light into one or more electrical signals.

4. The imaging apparatus of claim 3, wherein the wavelength converter comprises a matrix material selected from the group consisting of Gd₂O₃, Gd₂O₂S and CsI.

5. The radiological imaging apparatus of claim 4, wherein the photoelectric converter comprises mainly amorphous silicon.

6. The radiological imaging apparatus of claim 1, wherein the radiation detection unit comprises one or more switchers.

7. The radiological imaging apparatus of claim 1, wherein the radiation detection unit is made of a material selected from the group consisting of amorphous silicon, gallium arsenic, mercury iodide and lead iodide.

8. A radiological imaging method, comprising the steps of:

detecting and converting radiation from and irradiated subject into electrical signals using a photoelectric converter unit;

reading the electrical signals output by the photoelectric converter unit using a read-out unit operatively connected to said photoelectric converter unit;

processing the electrical signals connected to the electrical signal read-out unit so as to select between a first read-out operation, in which the subject is irradiated with radiation, and a second read-out operation, in which the subject is not irradiated;

performing said second read-out operation at least twice and averaging the results of said second read-out operation so as to obtain an average signal value thereof; and

subtracting said average signal value from a signal value obtained by said first read-out operation so as to obtain a processed image.

9. The radiological imaging method of claim 8, wherein said second read-out operation is performed at least twice but no more than five times.