Detector head position correction for hybrid SPECT/CT imaging apparatus

• US 20060214097A1
• Filed: 03/28/2005
• Published: 09/28/2006
• Est. Priority Date: 03/28/2005
• Status: Active Grant

• Current Assignee: Siemens Medical Solutions USA Incorporated (Siemens AG)
• Original Assignee: Siemens Medical Solutions USA Incorporated (Siemens AG)
• Inventors: Wang, Sharon Xiaorong, Fang, Joseph
• Granted Patent: US 7,307,252 B2
• Time in Patent Office: Days
• US Class Current: 250/252.100
• CPC Class Codes: G01T 1/1611 using both transmission and emission sources sequentially SPECT imaging G01T1/1642; PET imaging G01T1/2985; detecting prohibited goods, e.g. weapons, explosives, hazardous substances, contraband or smuggled objects G01V5/20
• CPC Class Codes: G01T 1/1612 with scintillation detectors G01T1/20 takes precedence
• CPC Class Codes: G01T 1/1648 Ancillary equipment for scintillation cameras, e.g. reference markers, devices for removing motion artifacts, calibration devices adapted for flow studies G01T1/1647
• CPC Class Codes: G01T 1/169 Exploration, location of contaminated surface areas
• CPC Class Codes: G01T 7/005 calibration techniques stabilization of spectrometer G01T1/40

Abstract

A system and method provide for more accurate SPECT/CT image registration. CT data is utilized to establish a global spatial coordinate system of a common test phantom. The common test phantom is then used to obtain a set of point source nuclear images. Three-dimensional CT point source data is mapped to a two-dimensional image plane of corresponding point source data, to obtain a pair of intersecting projection cones that are used to obtain a set of detector head position correction parameters to correct detector head positioning in the CT coordinate system when obtaining SPECT projection images of the same object.

Claims

1. A method for calibrating a medical imaging apparatus that is capable of acquiring medical images of a region using least two different imaging modalities, comprising the steps of:

imaging a multiple point source test phantom using each of said at least two different modalities;

calculating centroids of imaged point source data for each of said at least two different modalities;

aligning a point source centroid of a first of said at least two different modalities with a corresponding point source centroid of a second of said at least two different modalities so as to obtain a pair of conical generators;

determining a pair of lines on intersections of cones generated by said pair of conical generators having an angle therebetween corresponding to the angle between said cones; and

adjusting an image plane of one of said at least two modalities by modifying a normal thereof to correspond to said angle.

2. The method of claim 1, wherein one of said imaging modalities is SPECT, and is obtained using at least one detector head of said apparatus.

3. The method of claim 2, wherein another of said imaging modalities is CT, and is obtained using a CT scanning device of said apparatus.

4. The method of claim 3, wherein imaged point data of said SPECT modality is two-dimensional data, imaged point source data of said CT modality is three-dimensional data, and said image plane corresponds to said SPECT modality.

5. The method of claim 4, further comprising the steps of determining rotational detector head position correction parameters for each of said three dimensions in an image space of said CT modality.

6. The method of claim 5, wherein the steps of determining rotational detector head position correction parameters comprise the steps of solving vector equations describing locations of two-dimensional point source centroids of said SPECT modality in said three-dimensional image space of said CT modality.

7. The method of claim 1, wherein said test phantom comprises a structure having a plurality of point source isotopes at locations such that lines connecting any two pairs of said point source isotopes will be skewed with respect to each other.

8. The method of claim 7, wherein said test phantom is placed on a patient bed of said apparatus for imaging of said point source isotopes.

9. A method for calibrating a hybrid medical imaging apparatus that is capable of acquiring medical images of a region using a two-dimensional imaging modality and a three-dimensional imaging modality, comprising the steps of:

imaging a multiple point source test phantom in three-dimensional space using said three-dimensional modality, and imaging said multiple point source test phantom in multiple two-dimensional images using said two-dimensional modality;

calculating centroids of imaged point source data for each of said three-dimensional and multiple two-dimensional images;

aligning a point source centroid of said three-dimensional image with a corresponding point source centroid of one of said multiple two-dimensional images so as to obtain a pair of conical generators;

determining a pair of lines on intersections of cones generated by said pair of conical generators having an angle therebetween corresponding to the angle between said cones; and

adjusting the image plane of said two-dimensional image by modifying a normal thereof to correspond to said angle.

10. The method of claim 9, wherein said two-dimensional imaging modality is SPECT, and is obtained using at least one detector head of said apparatus.

11. The method of claim 10, further comprising the steps of determining rotational SPECT detector head position correction parameters for each of said three dimensions in an image space of said CT modality.

12. The method of claim 9, wherein said three-dimensional imaging modalities is CT, and is obtained using a CT scanning device of said apparatus.

13. The method of claim 9, wherein said test phantom comprises a structure having a plurality of point source isotopes at locations such that lines connecting any two pairs of said point source isotopes will be skewed with respect to each other.

14. A test phantom structure for calibration of a hybrid medical imaging apparatus to co-register a nuclear medical image with a medical image of a different modality, both obtained with said hybrid medical imaging apparatus, comprising a structure supporting a plurality of point source isotopes at locations such that lines connecting any two pairs of said point source isotopes will be skewed with respect to each other.

15. The test phantom structure as set forth in claim 14, wherein said hybrid medical imaging apparatus is a SPECTICT imaging apparatus.

16. A method of correcting a SPECT projection image of an object obtained by a nuclear medical imaging apparatus to provide for accurate registration of said SPECT projection image with a three-dimensional CT image of the same object, comprising the steps of:

storing a set of detector head position correction parameters for each of a plurality of predetermined image view angles;

retrieving detector head position correction parameters corresponding to a specific view angle of said SPECT projection image, with respect to said CT image;

adjusting a position of a detector head of said nuclear medical imaging apparatus in accordance with retrieved detector head position correction parameters;

calculating view angle-dependent linearity correction coefficients in accordance with a retrieved detector head position correction parameter;

acquiring SPECT projection image counts from said object with said detector head positioned at said adjusted position; and

framing resulting SPECT projection image data in accordance with said view angle-dependent linearity correction coefficients.

17. The method of claim 16, further comprising the step of adding said view angle-dependent linearity correction coefficients to originally obtained linearity correction coefficients to obtain final linearity correction coefficients, and wherein said framing step utilizes said final linearity correction coefficients.

18. The method of claim 16, further comprising the step of packaging a frame of resulting SPECT projection image data into a DICOM format along with a selected one of said detector head position correction parameters, for input to an image reconstruction engine.

19. The method of claim 16, wherein the step of retrieving further includes the step of interpolating retrieved detector head position correction parameters to correspond to said specific view angle.

20. The method of claim 16, wherein said detector head position correction parameters map two-dimensional SPECT image data to a three-dimensional coordinate system of said CT image.