Dose control in CT-images

• US 7,042,977 B2
• Filed: 09/05/2001
• Issued: 05/09/2006
• Est. Priority Date: 09/05/2001
• Status: Expired due to Term

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Dafni, Ehud
• Primary Examiner(s): Glick, Edward J.
• Assistant Examiner(s): Kiknadze, Irakli
• Application Number:
  US10/488,643
• Publication Number:
  US 20040247071A1
• Time in Patent Office: 1,707 Days
• Field of Search: 378/16, 378/4, 378/8, 378/15, 378/18, 378/19, 378/20, 378/21, 378/22, 378/23, 378/25, 378/26, 378/108, 378/145
• US Class Current: 378/16
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/488 involving pre-scan acquisition
• CPC Class Codes: A61B 6/542 involving control of exposure

Abstract

A method for determining a modulation function for modulating intensity of X-rays provided by an X-ray source of a CT-system for CT-imaging a slice of a region a person'"'"'s body, the method comprising: acquiring X-ray attenuation data for a first substantially anterior-posterior or lateral view of the slice; determining a first maximum X-ray attenuation from the attenuation data; determining a length of a projection of the slice along an axis in the plane of the slice that is substantially orthogonal to the view angle using the attenuation data; determining a second maximum X-ray attenuation for a second view orthogonal to the first view based on the determined length; and using the first and second attenuation maxima to determine the modulation function.

Claims

1. A method for determining a modulation function for modulating intensity of X-rays provided by an X-ray source of a CT-system for CT-imaging a slice of a region a person'"'"'s body, the method comprising:

acquiring X-ray attenuation data for a first substantially anterior-posterior or lateral view of the slice;

determining a first maximum X-ray attenuation from the attenuation data;

determining a length of a projection of the slice along an axis in the plane of the slice that is substantially orthogonal to the view angle using the attenuation data;

determining a second maximum X-ray attenuation for a second view orthogonal to the first view based on the determined length; and

using the first and second attenuation maxima to determine the modulation function.

2. A method according to claim 1 wherein determining the second maximum X-ray attenuation comprises determining the second maximum to be equal to a product of the length of the projection multiplied by an average X-ray absorption coefficient of for the slice.

3. A method according to claim 2 wherein the average X-ray absorption coefficient is equal to a predetermined average absorption coefficient characteristic of a region of the human body in which the slice is located.

4. A method according to claim 3 wherein the characteristic absorption coefficient is a function of at least one personal characteristic of the patient.

5. A method according to claim 4 wherein the at least one personal characteristic comprises the person'"'"'s body-type.

6. A method according to claim 4 wherein the at least one personal characteristic comprises the person'"'"'s gender.

7. A method according to claim 4 wherein the at least one personal characteristic comprises the person'"'"'s age.

8. A method according to claim 1 wherein determining a length for the projection comprises:

acquiring the first view with an array of X-ray detectors that face the X-ray source and that are located on a side of the body opposite to a side at which the X-ray source is located;

determining first and second boundaries between detectors in the detector array that receive X-rays attenuated by material in the slice and detectors in the array that receive X-rays that are not attenuated by material in the slice;

determining locations of projections of edges of the slice on the perpendicular axis from positions of the X-ray source at the first view angle and positions of detectors in neighborhoods of the first and second boundaries; and

determining the length of the projection to be equal to a distance between the projections of the edges.