Method And Computed Tomography Scanner For Carrying Out An Angiographic Examination

• US 20120014500A1
• Filed: 07/14/2011
• Published: 01/19/2012
• Est. Priority Date: 07/15/2010
• Status: Active Grant

• Current Assignee: Siemens Healthineers AG (Siemens AG)
• Original Assignee: Siemens AG
• Inventors: Flohr, Thomas, Grasruck, Michael, Sedlmair, Martin, Schmidt, Bernhard
• Granted Patent: US 8,447,009 B2
• Time in Patent Office: Days
• US Class Current: 378/5
• 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 6/4021 involving movement of the focal spot
• CPC Class Codes: A61B 6/4035 the source being combined with a filter or grating
• CPC Class Codes: A61B 6/405 Source units specially adapted to modify characteristics of the beam during the data acquisition process A61B6/4021, A61B6/4035 take precedence
• CPC Class Codes: A61B 6/4241 using energy resolving detectors, e.g. photon counting
• CPC Class Codes: A61B 6/482 involving multiple energy imaging
• CPC Class Codes: A61B 6/504 for diagnosis of blood vessels, e.g. by angiography
• CPC Class Codes: A61B 6/507 for determination of haemodynamic parameters, e.g. perfusion CT

Abstract

A method and a computed tomography scanner are disclosed for carrying out an angiographic examination of a patient, wherein the utilized computed tomography scanner includes at least one recording system mounted on a gantry such that it can rotate about a z-axis. Projection data is acquired from at least one prescribed angular position of the gantry for at least two different energies of X-ray radiation. The projection data is subsequently combined to form a resulting projection image by evaluating the projection data corresponding to the respective angular position, in which projection image at least one substance, which should be displayed selectively, is imaged with a high image contrast compared to the respective individual projection data. This procedure extends the field of application of the computed tomography scanner to projection-based angiography examinations, which were previously restricted to C-arm systems. 3D image reconstruction methods and projection methods can be carried out on opposite sides and with great flexibility during an examination, without the need for an additional modality. By using a multispectral technique, it is possible to contrast agent. The projection data at dispense with recording a native projection data record without the different energies are moreover acquired with no or little time offset, and so a computationally expensive and error-prone registration of the data records can be dispensed with.

Claims

1. A method involving angiographic examination of a patient using a computed tomography scanner with at least one recording system mounted on a gantry so as to be rotatable about a z-axis, the method comprising:

acquiring projection data from at least one angular position of the gantry for at least two different energies of X-ray radiation; and

combining the acquired projection data corresponding to a respective one of the at least one angular position to form a resulting projection image, in which at least one substance, which is selectively displayable, is imaged with a relatively high image contrast compared to the respective individual projection data.

2. The method as claimed in claim 1, wherein the projection data is acquired with a non-rotating gantry after setting the gantry to the at least one angular position.

3. The method as claimed in claim 1, wherein the projection data is obtained with a rotating gantry such that the acquisition of projection data only takes place when the gantry passes through the at least one angular position.

4. The method as claimed in claim 3, wherein projection data is recorded at a plurality of angular positions during the rotation.

5. The method as claimed in claim 1, wherein the projection data is acquired by different X-ray spectra.

6. The method as claimed in claim 5, wherein the different X-ray spectra are generated by changing an X-ray tube voltage or a radiation filter.

7. The method as claimed in claim 1, wherein the projection data is obtained by an energy-selective X-ray detector.

8. The method as claimed in claim 1, wherein the projection data is acquired at different sub-pixel positions at the same X-ray radiation energy.

9. The method as claimed in claim 1, wherein the projection data is acquired within one z-axis section.

10. The method as claimed in claim 8, wherein there is a continuous or oscillatory motion of a patient table, serving to support the patient, in the direction of the z-axis.

11. The method as claimed in claim 8, wherein the focus of an X-ray source is made to undergo an oscillatory motion.

12. The method as claimed in claim 1, wherein a concentration of the at least one substance is established from the projection data for each pixel of the projection image using a two or three material decomposition.

13. The method as claimed in claim 1, wherein the projection image is established from a weighted subtraction of the projection data with substance-specific weightings.

14. The method as claimed in claim 1, wherein the angular position to be set is selected automatically, depending on an examination region of the patient and taking into account previous anatomical knowledge, such that a tissue or vessel structure to be illustrated has as few overlays as possible.

17. The method as claimed in claim 7, wherein the projection data is obtained by a direct conversion semiconductor detector.

18. The method as claimed in claim 9, wherein there is a continuous or oscillatory motion of a patient table, serving to support the patient, in the direction of the z-axis.

19. The method as claimed in claim 9, wherein the focus of an X-ray source is made to undergo an oscillatory motion.

20. A tangible computer readable medium including program segments for, when executed on a computer device, causing the computer device to implement the method of claim 1.

15. A computed tomography scanner with at least one recording system mounted on a gantry so as to be rotatable about a z-axis, embodied to carry out an angiographic examination of a patient and comprising:

acquisition means for acquiring projection data from at least one angular position of the gantry for at least two different energies of X-ray radiation; and

combination means for combining the acquired projection data corresponding to a respective one of the at least one angular position to form a resulting projection image, in which at least one substance, which is selectively displayable, is imaged with a relatively high image contrast compared to the respective individual projection data.

16. A computed tomography scanner with at least one recording system mounted on a gantry so as to be rotatable about a z-axis, embodied to carry out an angiographic examination of a patient and comprising:

an acquisition device to acquire projection data from at least one angular position of the gantry for at least two different energies of X-ray radiation; and

a combination device to combine the acquired projection data corresponding to a respective one of the at least one angular position to form a resulting projection image, in which at least one substance, which is selectively displayable, is imaged with a relatively high image contrast compared to the respective individual projection data.