RF coil assemblies

1. An RF coil assembly comprising:

a plurality of multiturn loops formed of conductors configured to receive RF signals from a patient during MRI, each of the plurality of multiturn loops comprising an inner loop and an outer loop that both lie substantially in a plane of the RF coil assembly, the inner loop at least partially nested within the outer loop, the plurality of multiturn loops including a first multiturn loop and a third multiturn loop that is not adjacent the first multiturn loop; and

an inductor pair connected between the first multiturn loop and the third multiturn loop to electromagnetically isolate the first multiturn loop and the third multiturn loop.

2. The RF coil assembly of claim 1 , wherein the inner loop and the outer loop form a spiral shape.

3. The RF coil assembly of claim 1 , wherein the inner loop and the outer loop within a multiturn loop are arranged in series.

4. The RF coil assembly of claim 1 , wherein the inner loop being nested within the outer loop increases the inductance of the RF coil assembly.

5. The RF coil assembly of claim 1 , the plurality of multiturn loops comprising a first multiturn loop and a second multiturn loop, wherein the outer loops in each are at least partially formed from a common conductor.

6. The RF coil assembly of claim 1 , wherein at least one of the plurality of multiturn loops further comprises a third loop at least partially nested within the inner loop.

7. The RF coil assembly of claim 1 , further comprising:

a second multiturn loop that is adjacent the first multiturn loop, wherein the outer loops in each are at least partially formed from a common conductor; and

a passive isolation circuit disposed in the common conductor to electromagnetically isolate the first multiturn loop and the second multiturn loop.

8. The RF coil assembly of claim 1 , wherein the plurality of multiturn loops form a phased array coil.

9. The RF coil assembly of claim 1 , wherein the first multiturn loop of the plurality of multiturn loops is adjacent a second multiturn loop of the plurality of multiturn loops, but electromagnetically isolated.

10. The RF coil assembly of claim 9 , further comprising a capacitor between the first multiturn loop and the second multiturn loop to provide the electromagnetic isolation.

11. The RF coil assembly of claim 1 , wherein the RF coil assembly is part of a surface coil.

12. The RF coil assembly of claim 11 , wherein the surface coil further comprises a second RF coil assembly having a second plurality of multiturn loops and the second RF coil assembly at least partially overlapping the plurality of multiturn loops.

13. The RF coil assembly of claim 12 , wherein each of the second plurality of multiturn loops comprises a second inner loop and a second outer loop, and wherein each of the outer loops at least partially overlap an adjacent second outer loop and wherein each of the inner loops at least partially overlap an adjacent second inner loop.

14. The RF coil assembly of claim 12 , wherein each of the second plurality of multiturn loops comprises a second inner loop and a second outer loop, and wherein each of the outer loops at least partially overlap an adjacent second outer loop.

15. The RF coil assembly of claim 12 , wherein each of the second plurality of multiturn loops comprises a second inner loop and a second outer loop, and wherein each of the outer loops at least partially overlap an adjacent second outer loop and an adjacent second inner loop.

16. The RF coil assembly of claim 1 , wherein the RF coil assembly is part of a head coil.

17. The RF coil assembly of claim 16 , wherein the plurality of multiturn loops is formed circularly around an axis and has a larger radius at a proximal end than at a distal end.

18. The RF coil assembly of claim 16 , wherein the head coil further comprises a second RF coil assembly having a second plurality of multiturn loops and the second RF coil assembly at least partially overlapping the plurality of multiturn loops.

19. The RF coil assembly of claim 16 , the head coil comprising:

a second RF coil assembly, wherein the first multiturn loop of the plurality of multiturn loops and a second multiturn loop in the second RF coil assembly do not overlap; and

a capacitor connected between the RF coil assembly and the second RF coil assembly to provide electromagnetic isolation.

20. The RF coil assembly of claim 16 , further comprising a flexible foam housing having an opening to allow access by a head of the patient, wherein the plurality of the multiturn loops are housed at least partially by the flexible foam housing.

21. An RF coil assembly comprising:

a plurality of multiturn loops formed of conductors configured to receive RF signals from a patient during MRI, each of the plurality of multiturn loops comprising an inner loop and an outer loop that both lie substantially in a plane of the RF coil assembly, the inner loop at least partially nested within the outer loop, and

a single-turn loop in the plane of the RF coil assembly.

22. The RF coil assembly of claim 21 , wherein the single-turn loop is disposed between two of the plurality of multiturn loops.

23. The RF coil assembly of claim 21 , wherein the RF coil assembly is part of a head coil and the plurality of multiturn loops is formed circularly around an axis and has a larger radius at a proximal end than at a distal end.

24. The RF coil assembly of claim 21 , the plurality of multiturn loops comprising a first multiturn loop and a second multiturn loop, wherein the outer loops in each are at least partially formed from a common conductor.

25. The RF coil assembly of claim 21 , further comprising a flexible foam housing having an opening to allow access by a head of the patient, wherein the plurality of the multiturn loops are housed at least partially by the flexible foam housing.