MRI-compatible surgical cannulae for transferring a substance to and/or from a patient

1. A cannula for transferring a substance to and/or from a brain of a patient, the cannula comprising:

a tubular member defining a lumen extending from a proximal end to a distal end of the tubular member; and

a transfer tube axially slidably mounted in the lumen, wherein the transfer tube is telescopically extendable and retractable relative to the tubular member,

wherein a distance between the distal end of the tubular member and a distal end of the transfer tube is adjustable by telescopically extending and retracting the transfer tube relative to the tubular member,

wherein the transfer tube has an axially extending length that is greater than an axially extending length of the tubular member, wherein the transfer tube comprises a cylindrical outer wall surrounding an axially extending through lumen that extends for the axially extending length of the transfer tube and that defines an axially extending flow channel for a target substance for transfer, and wherein the transfer tube has a distal end portion with a constant outer diameter extending to a distal end face thereof.

2. The cannula of claim 1 , wherein the tubular member comprises a rigid, MRI-compatible material that has a linear straight shape and is configured such to retain the linear straight shape during use.

3. The cannula of claim 1 , wherein the tubular members comprises a ceramic material.

4. The cannula of claim 1 , including a conformal polymeric sleeve surrounding the tubular member.

5. The cannula of claim 1 , wherein an inner diameter of the tubular member is in a range of about 85 μm and 1.1 mm, and wherein an outer diameter of the tubular member is in a range of about 150 μm and 2.0 mm.

6. The cannula of claim 1 , wherein the tubular member comprises at least one exit port extending through a wall thereof and positioned between the distal end and the proximal end, and wherein the tubular member and the transfer tube are configured to be relatively rotated to align an exit port of the transfer tube with the tubular member at least one exit port.

7. The cannula of claim 6 , wherein the at least one exit port of the tubular member comprises a plurality of circumferentially spaced apart exit ports, and wherein the tubular member and the transfer tube are configured to relatively rotate to align the exit port of the transfer tube with one or more of the plurality of exit ports of the tubular member.

8. The cannula of claim 6 , wherein the tubular member and the transfer tube are relatively rotatable to cause the transfer tube exit port and one or more of the at least one exit port of the tubular member to overlap by a selected amount so as to adjust a flow rate of delivery of the substance through the transfer tube exit port.

9. The cannula of claim 8 , wherein the at least one exit port of the tubular member comprises a helical slot, and wherein the exit port of the transfer tube comprises a helical slot.

10. The cannula of claim 1 , wherein the tubular member comprises a rigid, MRI-compatible material, wherein the cannula is coupled to a targeting cannula, and wherein an adapter sleeve resides between the tubular member and the targeting cannula.

11. The cannula of claim 1 , wherein the tubular member comprises a ceramic material, and wherein the transfer tube is formed of fused silica.

12. The cannula of claim 1 , wherein the tubular member comprises at least one exit port extending above the distal end face and through a wall of the tubular member, and wherein the tubular member and the transfer tube are configured to relatively rotate to align an exit port extending through the cylindrical wall of the transfer tube with at least one of the at least one exit port of the tubular member.

13. The cannula of claim 1 , in combination with a trajectory guide assembly comprising a cylindrical channel sized and configured to slidably receive the cannula and position the distal end of the tubular member and the distal end of the transfer tube in a desired orientation and position that is internal to the patient during a therapeutic treatment.

14. The cannula of claim 1 , wherein the tubular member is a first tubular member, the cannula further comprising a second tubular member disposed in the first tubular member and extending beyond the distal end of the first tubular member, wherein the first tubular member tapers inward toward the second tubular member and terminates proximally to a distal end portion of the second tubular member.

15. The cannula of claim 1 , wherein the transfer tube is formed of rigid, MRI-compatible fused silica, wherein the transfer tube has an outer diameter in a range of 75 μm to 1.08 mm and a transfer lumen with a diameter in a range of 10 μm to 1 mm, wherein the transfer tube extends through the tubular member and out of the proximal and distal ends of the tubular member, wherein a sub-length of the transfer tube exits out of the proximal end of the tubular member and extends inside a length of flexible tubing.

16. The cannula of claim 1 , wherein the transfer tube is in fluid communication with a fluid reservoir comprising a therapeutic via a length of flexible tubing.

17. The cannula of claim 6 , wherein the exit port of the transfer tube is provided as a single exit port through the cylindrical wall of the transfer tube.

18. The cannula of claim 6 , wherein the at least one exit port of the tubular member is a single exit port.

19. The cannula of claim 18 , wherein the single exit port of the tubular member has an asymmetric perimeter shape.