Single photon emission computed tomography system

1. A single photon emission computed tomography system for producing multiple tomographic images of the type representing a three-dimensional distribution of a photon-emitting radioisotope in a field of view, said system comprising:

a detector assembly adjacent the field of view, said detector assembly including a photon-responsive detector is operable to detect if a photon strikes the detector, the detector assembly operable to detect photons emitted from the field of view;

a collimating assembly including at least two spaced apart collimating vanes of photon-attenuating material, each of the vanes being disposed between the detector assembly and the field of view;

a photon-blocking member disposed between the field of view and the detector, the blocking member having an aperture defined therethrough for passage of photons aligned with the aperture, a line of response being defined from the detector assembly through the aperture;

a mask disposed adjacent the detector assembly and between the detector assembly and the field of view, the mask having at least one aperture defined therethrough for passage of photons aligned with the aperture; and

a displacement actuator for moving the photon-blocking member relative to the detector assembly such that the aperture is displaced relative to the detector assembly and the line of response is swept across at least a portion of the field of view.

2. The system according to claim 1 , wherein a longitudinal axis is defined thin the field of view, the photon blocking member being a ring of photon attenuating material generally coaxial with the longitudinal axis, the photon blocking member generally disposed in an imaging plane, the aperture defined in the photon blocking member comprising a plurality of spaced apart aperture slots defined thru the ring of photon attenuating material.

3. The system according to claim 2 , wherein each aperture slot is generally parallel to the longitudinal axis and perpendicular to the imaging plane.

4. The system according to claim 2 , wherein the photon blocking member is disposed between the collimating assembly and the field of view.

5. The system according to claim 1 , wherein a longitudinal axis is defined thru the field of view, the mask being a ring of photon attenuating material generally coaxial with the longitudinal axis, the mask generally disposed in an imaging plane, the aperture defined in the mask comprising a plurality of spaced apart aperture slots defined thru the ring of photon attenuating material.

6. The system according to claim 5 , wherein each aperture slot is generally parallel to the longitudinal axis and perpendicular to the imaging plane.

7. The system according to claim 1 , wherein a longitudinal axis is defined thru the field of view, the collimating vanes each being generally ring shaped and disposed in a plane perpendicular to the longitudinal axis, each vane having a depth extending radially from a front edge to a rear edge in the plane and a thickness perpendicular to the plane, the depth of each vane being greater than the thickness.

8. The system according to claim 7 , wherein a radiolucent material is disposed in the spaces between said vanes.

9. The system according to claim 7 , wherein the collimating assembly includes only vanes that are generally parallel to each other and generally perpendicular to the longitudinal axis.

10. The system according to claim 1 , wherein a longitudinal axis is defined thru the field of view, the detector assembly being generally ring shaped and generally coaxial with the longitudinal axis, the detector assembly generally disposed in an imaging plane.

11. The system according to claim 10 , wherein the detector assembly comprises a ring of scintillation material with an outwardly adjacent ring of photo detectors.

12. The system according to claim 10 , wherein the detector assembly comprises a plurality of solid state photon detectors disposed generally in a ring.

13. The system according to claim 1 , wherein the detector assembly, the collimating assembly, the photon-blocking member and the mask are each generally arcuate members extending between a pair of spaced apart ends.

14. The system according to claim 1 , wherein each arcuate member extends over an arc between 180 and 360 degrees.

15. The system according to claim 1 , wherein the photon-blocking member and the mask are each generally flat members.

16. The system according to claim 1 , wherein a generally vertical longitudinal axis is defined thru the field of view, the system being generally ring shaped and generally coaxial with the longitudinal axis, the system disposed in a generally horizontal imaging plane.

17. The system according to claim 1 , wherein the collimating assembly comprises a stack of alternating sheets of photon-blocking material and sheets of radiolucent material, the sheets of photon-blocking material defining the collimating vanes.

18. The system according to claim 1 , further comprising a chair-like base having a generally horizontal bottom portion for supporting a patient's hips and a generally vertical back portion of supporting the patient's back.

19. The system according to claim 18 , wherein the detector assembly, the collimating assembly, the photon-blocking member and the mask are each generally ring shaped members and are disposed such that the field of view is positioned to receive a patient's head when the patient is seated in the chair-like base.

20. The system according to claim 1 , wherein the mask is moveable relative to the detector so as to expose different portions of the photon receiving face of the detector to photons passing through the mask.