Apparatus for accurately controlling needle extension

1. A medical device comprising:

a needle comprising a proximal portion and a distal portion, wherein the distal portion of the needle comprises a sharpened tip;

a sheath comprising a proximal portion, a distal portion, and a lumen extending between the proximal portion and the distal portion of the sheath, the lumen being defined by an inner surface of the sheath, wherein at least a portion of the needle is movably disposed through the lumen of the sheath;

a plurality of spaced apart first engagement members affixed to the inner surface of the sheath, comprising at least one change in an inner diameter between neighboring first engagement members;

a second engagement member affixed to the proximal portion of the needle, and comprises an annular component with at least one wing disposed about an outer surface of the annular component, wherein the wing of the annular component is configured to engage the at least one change in the inner diameter of the plurality of spaced apart first engagement members.

2. The medical device of claim 1 , further comprising a handle in communication with the sheath, where the handle is configured for axial retraction or extension of the sheath to expose or conceal the distal portion of the needle.

3. The medical device of claim 1

wherein the wing of the annular component is configured to frictionally engage the first engagement members.

4. The medical device of claim 1 , wherein the at least one change in the inner diameter of the plurality of spaced apart first engagement members further comprises:

a first change in inner diameter;

a second change in inner diameter; and

a third change in inner diameter;

wherein the first change in inner diameter comprises a diameter smaller than a diameter of the second and third changes in inner diameter, wherein the second change in inner diameter comprises a diameter larger than the first change in inner diameter, and wherein the third change in inner diameter comprises a diameter larger than the second change in inner diameter.

5. The medical device of claim 4 , wherein the first change in inner diameter, second change in inner diameter, and third change in inner diameter each traverse a length of the sheath along a longitudinal axis of the sheath.

6. The medical device of claim 5 , wherein each of the first, second, and third changes in inner diameter traverse a different length of the sheath along the longitudinal axis.

7. The medical device of claim 1 , wherein the annular component further comprises a retrieval loop comprising a proximal portion and a distal portion, wherein the distal portion is attached to the at least one wing of the annular component, and wherein the retrieval loop is configured to compress the at least one wing of the annular component when the proximal portion of the retrieval loop is pulled.

8. The medical device of claim 1 , wherein the sheath further comprises a retrieval slot disposed about an inner surface of the sheath, wherein the retrieval slot is configured to slideably engage the at least one wing of the annular component.

9. The medical device of claim 1 , wherein the proximal portion of the needle is sufficiently flexible such that angulation of an endoscope is not unduly diminished or hindered when disposed through a working channel of the endoscope.

10. The medical device of claim 1 , wherein each of the first engagement members are cylindrical.

11. The medical device of claim 1 , wherein the annular component comprises two wings.

12. The medical device of claim 1 , wherein the at least one change in diameter between neighboring first engagement members defines a step upon an end of a portion of the inner surface of the sheath with the smaller diameter of the at least one change in diameter, wherein the wing of the annular component engages the step when the sheath is urged toward the distal end of the needle, which prevents distal motion of the sheath with respect to the needle.

13. A medical device comprising:

a needle comprising a proximal portion and a distal portion, wherein the distal portion of the needle comprises a sharpened tip;

a sheath comprising a proximal portion, a distal portion, and a lumen extending between the proximal portion and the distal portion of the sheath, the lumen being defined by an inner surface of the sheath, wherein at least a portion of the needle is movably disposed through the lumen of the sheath,

wherein the inner surface of the sheath further comprises at least one change in a diameter between neighboring portions of the sheath;

an annular component disposed around a portion of a surface of the needle, wherein the annular component further comprising at least one wing disposed about an outer surface of the annular component,

wherein the winq of the annular component is configured to incrementally engage the change in the diameter of the inner surface of the sheath; and

a handle attached to the sheath and the needle, where the handle is configured for axial retraction and extension of the sheath to incrementally engage the annular component and expose or conceal a distal portion of the needle.

14. The medical device of claim 13 , wherein the needle further comprises at least one marker, wherein the marker is configured for visualization by a direct or indirect visualization device.

15. The medical device of claim 13 , further comprising a connector connected to a proximal portion of the handle, wherein the connector is configured to receive a syringe.

16. The medical device of claim 13 , wherein the proximal portion of the needle is sufficiently flexible such that angulation of an endoscope is not unduly diminished or hindered when disposed through a working channel of the endoscope.

17. The medical device of claim 13 , wherein the at least one change in diameter between neighboring portions of the inner surface of the sheath defines a step upon an end of a portion of the inner surface of the sheath with the smaller diameter of the at least one change in diameter, wherein the wing of the annular component engages the step when the sheath is urged toward the distal end of the needle, which prevents distal motion of the sheath with respect to the needle.

18. A medical device comprising:

a needle comprising a proximal portion and a distal portion, wherein the distal portion of the needle comprises a sharpened tip;

a sheath comprising a proximal portion, a distal portion, and a lumen extending between the proximal portion and the distal portion of the sheath, the lumen being defined by an inner surface of the sheath, wherein at least a portion of the needle is movably disposed through the lumen of the sheath;

a first accurate needle extension member in communication with the inner surface of the sheath comprising at least one change in a diameter between neighboring portions of the inner surface of the sheath; and

a second accurate needle extension member in communication with the needle, wherein the second extension member comprises an annular component comprising at least one wing disposed about an outer surface of the annular component,

wherein the wing of the second accurate needle extension member is configured for engagement with the change in the diameter of the first accurate needle extension member for accurately extending a length of the needle from the distal portion of the sheath.

19. The medical device of claim 18 , wherein the at least one change in diameter between neighboring portions of the inner surface of the sheath defines a step upon an end of a portion of the inner surface of the sheath with the smaller diameter of the at least one change in diameter, wherein the wing of the annular component engages the step when the sheath is urged toward the distal end of the needle, which prevents distal motion of the sheath with respect to the needle.