MR/PET IMAGING SYSTEMS

• US 20100219347A1
• Filed: 06/23/2008
• Published: 09/02/2010
• Est. Priority Date: 07/25/2007
• 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: Schulz, Volkmar, Solf, Torsten J., Morich, Michael A., Demeester, Gordon D.
• Granted Patent: US 8,525,116 B2
• Time in Patent Office: Days
• US Class Current: 250/363.40
• CPC Class Codes: G01T 1/1603 with a combination of at least two different types of detector see provisionally also G01T1/16

Abstract

An imaging system includes positron emission tomography (PET) detectors (30) shrouded by broadband galvanic isolation (99) and coincidence detection electronics (50, 50_ob), or other radiation detectors. A magnetic resonance scanner includes a main magnet (12, 14) and magnetic field gradient assembly (20, 20′, 22, 24) configured to acquire imaging data from a magnetic resonance examination region at least partially overlapping the examination region surrounded by the PET detectors. A radio frequency coil (80, 100) has plurality of conductors (66, 166) and a radio frequency screen (88, 188, 188_EB, 188_F) substantially surrounding the conductors to shield the coil at the magnetic resonance frequency. The radiation detectors are outside of the radio frequency screen. Magnetic resonance-compatible radiation collimators or shielding (60, 62) containing an electrically non-conductive and non-ferromagnetic heavy atom oxide material are disposed with the radiation detectors.

Claims

1. An imaging system comprising:

positron emission tomography (PET) detectors (30) substantially encircling an examination region;

electronics operatively coupled with the PET detectors to perform coincidence detection of probative radiation comprising 511 keV gamma rays generated by electron-positron annihilation events occurring in the examination region; and

radiation shielding disposed adjacent the PET detectors to reduce interaction of non-probative radiation with the PET detectors, at least a portion of the radiation shielding comprising an electrically non-conductive and non-ferromagnetic heavy atom oxide material.

2. The imaging system as set forth in claim 1, wherein the radiation shielding comprises a lead oxide material.

3. The imaging system as set forth in claim 1, wherein the radiation shielding comprises a lead oxide powder material.

4. The imaging system as set forth in claim 3, wherein the radiation shielding further comprises a resin, glass, or plastic host material in which is dispersed the lead oxide powder material.

5. The imaging system as set forth in claim 1, wherein the radiation shielding comprises a ceramic material including lead oxide.

6. The imaging system as set forth in claim 1, wherein the radiation shielding is selectively extendible toward or away from the examination region.

7. The imaging system as set forth in claim 1, further comprising:

a magnetic resonance scanner comprising a main magnet, a magnetic field gradient assembly, and a radio frequency coil, the magnetic resonance scanner configured to acquire imaging data from a magnetic resonance examination region at least partially overlapping the examination region surrounded by the PET detectors.

8. The imaging system as set forth in claim 7, wherein the magnetic resonance scanner is a bore-type scanner, the PET detectors are arranged as an annular ring concentric with a bore of the bore-type scanner, and the radiation shielding comprising an electrically non-conductive and non-ferromagnetic heavy atom oxide material is arranged in two annular shielding rings concentric with the bore and on opposite sides of the annular ring of PET detectors.

9. The imaging system as set forth in claim 7, wherein the magnetic resonance scanner further comprises:

annular ferromagnetic shims disposed at a same axial position as the annular shielding rings.

10. The imaging system as set forth in claim 7, wherein the magnetic resonance scanner is a bore-type scanner, the PET detectors are arranged as an annular ring concentric with a bore of the bore-type scanner, and the magnetic resonance scanner further comprises:

a cylindrical radio frequency screen arranged coaxially with the bore, the magnetic field gradient assembly being disposed outside of the cylindrical radio frequency screen.

11. The imaging system as set forth in claim 10, wherein the cylindrical radio frequency screen has an annular groove or channel receiving the annular ring of PET detectors.

12. The imaging system as set forth in claim 10, further comprising:

electrical power and communication cabling operatively connected with the PET detectors and disposed outside of the cylindrical radio frequency screen; and

fluid cooling lines operatively connected with the PET detectors and disposed outside of the cylindrical radio frequency screen.

13. The imaging system as set forth in claim 10, wherein the PET detectors comprise PET detector modules each substantially surrounded by a shield that shields the PET detectors at the magnetic resonance frequency.

14. The imaging system as set forth in claim 7, wherein the radio frequency coil comprises:

a plurality of conductive elements arranged in a line-of-sight between the PET detectors and the examination region, the conductive elements having thickness along the line-of-sight effective to be substantially transparent to the probative radiation.

15. The imaging system as set forth in claim 7, wherein the radio frequency coil comprises:

a plurality of conductive elements arranged in a line-of-sight between the PET detectors and the examination region, the conductive elements having thickness along the line-of-sight of less than or about 50 microns.

16. The imaging system as set forth in claim 15, wherein at least a portion of the conductive elements are generally planar copper strips or strip lines.

17. The imaging system as set forth in claim 15, wherein the radio frequency coil further comprises:

lumped capacitors disposed outside of the line-of-sight between the PET detectors and the examination region.

18. The imaging system as set forth in claim 7, wherein the radio frequency coil and the PET detectors are integrally arranged as a local radio frequency coil module comprising:

a plurality of conductors;

a radio frequency shield substantially surrounding the conductors, the conductors and the radio frequency screen being configured to be resonant at about the magnetic resonance frequency to provide radio frequency shielding between the conductors and surrounding structures at the magnetic resonance frequency, the radio frequency shield being substantially transparent to fields produced by the magnetic field gradient assembly and to the probative radiation;

the PET detectors (30) being arranged outside of the radio frequency shield and including broadband radio frequency shielding, conductors defining the coil that lie in a line-of-sight between the PET detectors and the examination region having a thickness along the line-of-sight effective to be substantially transparent to the probative radiation, the plurality of conductors, radio frequency shield, and PET detectors being arranged as a module that is selectively insertable into the magnetic resonance examination region.

19. The imaging system as set forth in claim 18, wherein the local radio frequency coil is a generally cylindrical end-capped radio frequency coil in which the radio frequency shield has an end cap at a capped end and the conductors defining the coil include rods or an end ring that connect with the radio frequency shield proximate to the capped end to define a radio frequency mirror.

20. The imaging system as set forth in claim 18, wherein the local radio frequency coil has at least one flanged end at which the radio frequency shield includes an outwardly extending flange, the magnetic resonance scanner being a cylindrical bore scanner further comprising:

a whole-body radio frequency shield, the outwardly extending flange of the local radio frequency coil extending toward the whole-body radio frequency shield to define separate radio frequency and radio frequency-free spaces.

21. An imaging system comprising:

positron emission tomography (PET) detectors substantially encircling an examination region;

electronics operatively coupled with the PET detectors to perform coincidence detection of probative radiation comprising 511 keV gamma rays generated by electron-positron annihilation events occurring in the examination region;

a magnetic resonance scanner comprising a main magnet and a magnetic field gradient assembly, the magnetic resonance scanner configured to acquire imaging data from a magnetic resonance examination region at least partially overlapping the examination region surrounded by the PET detectors; and

a radio frequency coil comprising a plurality of conductors and a radio frequency screen encircling the plurality of conductors, the PET detectors being disposed outside of the radio frequency screen, the radio frequency screen providing radio frequency shielding for the PET detectors at the magnetic resonance frequency.

22. The imaging system as set forth in claim 21, further comprising:

radiation shielding disposed with the PET detectors and including a heavy metal oxide to reduce interaction of non-probative radiation with the PET detectors.

23. The imaging system as set forth in claim 22, wherein the radiation shielding includes lead oxide dispersed in a resin, glass, or plastic host material.

24. The imaging system as set forth in claim 22, wherein the radiation shielding is selectively extendible toward or away from the examination region.

25. The imaging system as set forth in claim 21, wherein the magnetic resonance scanner is a bore-type scanner, the radio frequency screen comprises a cylindrical radio frequency screen arranged coaxially with a bore of the bore-type scanner, and the PET detectors are arranged as an annular ring concentric with the bore and outside of the cylindrical radio frequency screen.

26. The imaging system as set forth in claim 25, wherein the cylindrical radio frequency screen has an annular groove or channel receiving the annular ring of PET detectors.

27. The imaging system as set forth in claim 21, wherein conductors that lie in a line-of-sight between the PET detectors and the examination region have a thickness along the line-of-sight of less than or about 50 microns.

28. The imaging system as set forth in claim 27, wherein the radio frequency coil further comprises:

lumped capacitors disposed outside of the line-of-sight between the PET detectors and the examination region.

29. The imaging system as set forth in claim 21, wherein the radio frequency coil and the PET detectors are integrally arranged as a local radio frequency coil module that is selectively insertable into the magnetic resonance examination region.

30. The imaging system as set forth in claim 29, wherein the local radio frequency coil is an end-capped radio frequency coil in which the radio frequency screen has an end cap at a capped end to define a radio frequency mirror.

31. The imaging system as set forth in claim 30, wherein the local radio frequency coil has a flanged end opposite the capped end, the radio frequency screen at the flanged end including an outwardly extending flange.

32. An imaging system comprising:

a magnetic resonance scanner comprising a main magnet, a magnetic field gradient assembly, and a whole-body radio frequency screen;

a local radio frequency coil having a radio frequency screen including an end-cap portion and a flanged open portion, the flanged portion sized such that an annular edge of the flange portion is proximate to the whole-body radio frequency screen to define a radio frequency space including an interior of the local radio frequency coil and a radio frequency-free space including most of an exterior of the local radio frequency coil; and

an annular ring of positron emission tomography (PET) detectors mounted on the local radio frequency coil in the radio frequency-free space to view the interior of the local radio frequency coil.

33. An imaging system comprising:

a bore-type magnetic resonance scanner comprising a main magnet, a magnetic field gradient assembly, and a generally cylindrical radio frequency screen arranged coaxially with the scanner bore, the generally cylindrical radio frequency screen having a radius except at a central annular groove or channel of smaller radius compared with the radius;

one or more radiation detectors received into the annular groove or channel of the generally cylindrical radio frequency screen and operatively coupled with electronics to perform radiation detection, the one or more radiation detectors including a radiation collimator or radiation shielding comprising an electrically non-conductive and non-ferromagnetic heavy atom oxide material.

34. The imaging system as set forth in claim 33, wherein the one or more radiation detectors comprise an annular ring of positron emission tomography (PET) detectors received into the annular groove or channel and including cladding annular rings of radiation shielding comprising an electrically non-conductive and non-ferromagnetic heavy atom oxide material.

35. The imaging system as set forth in claim 33, wherein the one or more radiation detectors are selected from a group consisting of:

(i) positron emission tomography (PET) detectors (30) having radiation shielding comprising an electrically non-conductive and non-ferromagnetic heavy atom oxide material and (ii) one or more movable radiation detector heads having radiation collimators comprising an electrically non-conductive and non-ferromagnetic heavy atom oxide material.

36. A radio frequency screen for use in an imaging system, the radio frequency screen comprising:

a generally cylindrical radio frequency screen having a radius respective to a central axis, the generally cylindrical radio frequency screen having a central annular groove or channel at which the generally cylindrical radio frequency screen has a smaller radius compared with the radius.