Apparatus for acquisition of CT data with penumbra attenuation calibration

• US 7,260,171 B1
• Filed: 10/25/2004
• Issued: 08/21/2007
• Est. Priority Date: 10/25/2004
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Ruimi, David, Meirav, Oded, Armstrong, Robert H., Arenson, Jerome S.
• Primary Examiner(s): KAO, CHIH CHENG G
• Application Number:
  US10/904,116
• Time in Patent Office: 1,030 Days
• Field of Search: 378/16, 378/147, 378/148, 378/149, 378/19
• US Class Current: 378/16
• CPC Class Codes: A61B 6/027 characterised by the use of a particular data acquisition trajectory, e.g. helical or spiral
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/06 Diaphragms
• CPC Class Codes: A61B 6/542 involving control of exposure
• CPC Class Codes: G21K 1/04 using variable diaphragms, shutters, choppers

Abstract

The present invention is a directed method and apparatus for collimating a radiation beam such that the full intensity of the radiation beam does not impinge detectors of a radiation detector assembly that are particularly susceptible to saturation or over-ranging. This collimation can be dynamically adjusted on a per view basis using empirical or scout scan data.

Claims

1. A CT system comprising:

a radiation source configured to project a radiation beam toward a subject to be scanned;

a collimator configured to collimate the radiation beam;

a multi-row CT detector configured to detect radiation emitted by the radiation source and attenuated by the subject; and

a controller operationally connected to the collimator and configured to control the collimator so as to limit exposure of a full intensity of the radiation beam to less than all detector rows of the multi-row CT detector and to use readings from outer detector rows to calibrate the less than all detector rows of the multi-row CT detector when any of the less than all detector rows of the multi-row CT detector saturates.

2. The CT system of claim 1 wherein the controller is further configured to limit exposure of the full intensity of the radiation beam to N-2 detector rows of the multi-row CT detector having N detector rows.

3. The CT system of claim 2 wherein the controller is further configured to select the N-2 detector rows for exposure to the full intensity of the radiation beam to include one detector row from extremities of the multi-row CT detector.

4. The CT system of claim 3 wherein the controller is further configured to control the collimator to collimate the radiation beam in a z-direction such that outer detector rows of the multi-row CT detector only receive radiation from a penumbra of the radiation beam.

5. The CT system of claim 1 wherein the controller is further configured to define less than all detector rows of the multi-row CT detector to include all rows of the multi-row CT detector except a single outer-most detector row.

6. The CT system of claim 1 wherein the controller is further configured to define less than all detector rows of the multi-row CT detector to include all detector rows except for a center-most detector row.

7. The CT system of claim 6 wherein the controller is further configured to use output from the center-most detector row for intensity calibration of all of the other detector rows of the multi-row CT detector.

8. The CT system of claim 1 further comprising a filter of attenuating material disposed in proximity to the less than all detector rows of the multi-row CT detector to reduce z-direction focal spot drift.

9. The CT system of claim 1 wherein the collimator is further controlled to define a slice-width for full intensity exposure of the radiation beam.

10. The CT system of claim 9 wherein the controller is further configured to control the collimator to define an x-ray fan beam sized to a width in a z-direction less than a width, in the z-direction, of the multi-row detector.

11. A radiographic imaging system comprising:

a multi-slice CT detector configured to detect radiation emitted by a radiation source and attenuated by a subject to be imaged; and

a slice-width collimator disposed between the radiation source and the multi-slice CT detector and configured to collimate a radiation beam in a direction parallel to a long axis of the subject such that full intensity of the radiation beam is prevented from impinging upon at least one intensity calibration detector row of the multi-slice CT detector, wherein the at least one intensity calibration detector row is constructed to saturate at a higher x-ray flux rate than a non-intensity calibration detector row of the multi-slice CT detector.

12. The radiographic imaging system of claim 11 wherein the slice-width collimator is further configured to define a full intensity radiation beam that extends to include all detector rows but one outer-most detector row at a fore end and an aft end of the multi-slice CT detector.

13. The radiographic imaging system of claim 11 further comprising a computer programmed to interpolate data collected from the at least one intensity calibration detector row to estimate data for an over-ranging portion of the multi-slice CT detector.

14. The radiographic imaging system of claim 11 wherein the at least one intensity calibration detector row includes a single detector row centrally disposed in the multi-slice CT detector.

15. The radiographic imaging system of claim 11 wherein the at least one intensity calibration detector row is constructed to have less z-coverage than a non-intensity calibration detector row of the multi-row CT detector.