Computer tomography imaging

• US 20030007593A1
• Filed: 06/25/2002
• Published: 01/09/2003
• Est. Priority Date: 06/28/2001
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Heuscher, Dominic J., Wang, Ge, Zhao, Shiying, Matthews, David D.
• Granted Patent: US 7,058,440 B2
• Time in Patent Office: Days
• US Class Current: 378/4
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/7289 Retrospective gating, i.e. associating measured signals or images with a physiological event after the actual measurement or image acquisition, e.g. by simultaneously recording an additional physiological signal during the measurement or image acquisition
• 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 6/4085 Cone-beams
• CPC Class Codes: A61B 6/5247 combining images from an ionising-radiation diagnostic technique and a non-ionising radiation diagnostic technique, e.g. X-ray and ultrasound
• CPC Class Codes: A61B 6/541 involving acquisition triggered by a physiological signal
• CPC Class Codes: A61B 6/583 using calibration phantoms
• CPC Class Codes: A61B 8/08 Detecting organic movements or changes, e.g. tumours, cysts, swellings A61B8/02 - A61B8/06 take precedence
• CPC Class Codes: A61B 8/4416 related to combined acquisition of different diagnostic modalities, e.g. combination of ultrasound and X-ray acquisitions

Abstract

An apparatus for computed tomography (CT) imaging of a cyclically moving organ includes a positional state monitor (24, 40) that monitors a positional state of the cyclically moving organ such as the heart. A cone-beam CT scanner (10) acquires image data at least within a plurality of time windows. Each time window is centered about an occurrence of a selected positional state of the organ. A window analyzer (38) selects a data segment within each time window such that the data segments combine to form a complete data set covering a selected angular range. A reconstruction processor (44) reconstructs the selected data segments into an image representation.

Claims

1. A method for acquiring diagnostic imaging data of a dynamically moving organ, the method comprising:

monitoring a positional state of the organ motion as a function of time;

selecting time windows arranged about occurrences of a selected positional state;

acquiring imaging data of the dynamically moving organ at least during the time windows;

combining portions of the imaging data acquired during the time windows to form a complete image data set; and

reconstructing an image representation from the complete image data set.

2. The method as set forth in claim 1, wherein the step of monitoring a positional state includes:

measuring a physiological parameter;

determining a positional state relationship that relates the positional state to the physiological parameter; and

identifying occurrences of the selected positional state based on the measured physiological parameter and the state relationship.

3. The imaging method as set forth in claim 2, wherein the determining of a positional state relationship includes:

defining a parametric functional model of the positional state relationship.

4. The imaging method as set forth in claim 2, wherein the positional state includes a volume of a selected heart chamber, and the measuring of a physiological parameter includes:

performing an electrocardiographic measurement.

5. The imaging method as set forth in claim 1, further including:

correcting the occurrences of the selected positional state based on the reconstructed image representations;

adjusting the arrangement of the time windows based on the corrected occurrences; and

repeating the combining and reconstructing steps using the adjusted time windows.

6. The method as set forth in claim 1, wherein the time windows include two time windows within a single cycle of the dynamically moving organ.

7. The method as set forth in claim 1, wherein the time windows include time windows arranged in at least two consecutive cycles of the dynamically moving organ.

8. The method as set forth in claim 1, wherein the combining step includes:

selecting a data portion within each window such that the data portions provide a selected angular coverage.

9. The method as set forth in claim 1, wherein the acquiring of imaging data includes:

acquiring cone-beam computed tomography (CT) imaging data using a generally helically orbiting x-ray source.

10. The imaging method as set forth in claim 9, wherein the combining step includes:

for each time window, selecting an angular segment of the orbiting x-ray source substantially centered within the time window; and

adaptively adjusting each angular segment within its corresponding time window to provide angularly continuous data sets for reconstruction while optimizing centering of the angular spans within their respective windows.

11. The method as set forth in claim 10, wherein the complete image data set includes data spanning 180°

of angular orientations of the cone-beam plus at least a fan angle.

12. The method as set forth in claim 10, wherein the complete image data set comprises at least two angularly contiguous and temporally discontinuous angular segments.

13. The method as set forth in claim 10, further including:

weighting each angular segment.

14. The method as set forth in claim 9, wherein the reconstructing step includes:

weighting the complete image data set by a weighting function that reduces the contribution of data from the angular extremities; and

performing a three-dimensional backprojection to generate the image representation.

15. The method as set forth in claim 1, wherein the positional state includes one of a spatial position of the organ and a spatial volume of the organ.

16. The method as set forth in claim 1, wherein the dynamically moving organ includes at least a portion of the heart, and the time windows include:

a first time window arranged about a first occurrence of the selected positional state during the systolic cardiac cycle portion; and

a second time window arranged about a second occurrence of the selected positional state during the diastolic cardiac cycle portion.

18. The apparatus as set forth in claim 17, wherein the window analyzer includes:

a means for selecting a data segment in each time window, which data segments (1) taken together form a complete set of image data for reconstruction, and (2) are optimally centered within the time windows.

19. The apparatus as set forth in claim 17, wherein the cyclically moving organ is a cardiac organ, and the positional state monitor includes:

an electrocardiograph that monitors a cardiac phase; and

a cardiac state analyzer that relates the measured cardiac phase with a positional cardiac state.

20. The apparatus as set forth in claim 17, wherein the positional state monitor includes:

an auxiliary imaging apparatus that images a position of the cyclically moving organ during the CT image data acquisition.

21. The apparatus as set forth in claim 20, wherein the auxiliary imaging apparatus includes an ultrasonic imaging apparatus.

17. An apparatus for computed tomography (CT) imaging of a cyclically moving organ, the apparatus comprising:

a positional state monitor that monitors a positional state of the cyclically moving organ;

a cone-beam CT scanner that acquires image data at least within a plurality of time windows, each time window centered about an occurrence of a selected positional state of the organ;

a window analyzer that selects a data segment within each time window such that the data segments combine to form a complete data set covering a selected angular range; and

a reconstruction processor that reconstructs the selected data segments into an image representation.

22. An apparatus for acquiring volumetric medical imaging data of a dynamically moving organ, the apparatus comprising:

a means for monitoring an anatomical state of the organ motion cycling;

a means for determining time windows centered on occurrences of substantially similar states of organ motion cycle;

a means for acquiring imaging data at least during the time windows;

a means for combining portions of the imaging data acquired during the time windows to form a complete image data set; and

a means for reconstructing an image representation from the complete image data set.

23. The apparatus as set forth in claim 22, wherein the acquiring means includes:

a means for projecting x-rays into an examination region containing the dynamically moving organ;

a means for detecting x-ray intensity after passing through the examination region;

a means for assembling the detected x-ray intensity data to form computed tomography projection data;

a means for rotating the means for projecting to acquire projection data at a plurality of projection angles; and

a means for advancing the dynamically moving organ linearly in a direction transverse to the rotation plane.

24. The apparatus as set forth in claim 22, wherein the combining means includes:

a means for selecting an angular interval within each time window;

a means for adaptively adjusting each angular interval using a constrained optimization in which the constraints include retaining each angular interval within its associated time window and the optimizing criteria include minimizing a separation between a center of each angular interval and the center of its associated time window, the adaptive adjusting arranging the angular intervals to collectively span at least an angular range corresponding to an angular range of a complete data set; and

a means for combining projection data portions corresponding to the adaptively adjusted angular intervals to form the complete image data set.

25. The apparatus as set forth in claim 22, wherein the means for monitoring a state include:

a means for monitoring a temporal percentage phase of a cycle of the dynamically moving organ; and

a means for correlating the temporal percentage phase with an anatomical state of at least a portion of the dynamically moving organ.