Segmented catheter for tissue ablation
A near-field antenna structure is described that is an effective delivery tool for radiofrequency (RF) and microwave power to achieve coagulative necrosis in metastatic tumors while reducing or eliminating thermal conduction along the structure. This tool is a probe small enough to be used safely virtually anywhere in the neck, chest, abdomen, and pelvis, and be guided by computerized tomography (CT) or ultrasonic imaging.
1. A catheter comprising an outer sheath, wherein said outer sheath comprises a plurality of segments and non-conductive elements, wherein said plurality of segments are successively aligned in a longitudinal manner, wherein each segment is resonant at a drive frequency, wherein each segment has a length of (2n−1)λ/4 where n is a non-zero positive integer, wherein one of said non-conductive elements is positioned between each of said successively aligned segments, wherein said non-conductive elements permit efficient passage of microwave energy at said drive frequency along said successively aligned segments while inhibiting the passage of power at other frequencies along said successively aligned segments so as to minimize production of thermal energy along said catheter.
2. The catheter of claim 1 having an inner co-axial cable with a center conductor suspended by said non-conductive materials and an air dielectric.
3. The catheter of claim 1 having inner coaxial sections of lengths resonant at a drive frequency.
4. The catheter of claim 1 , further comprising a middle conductor and a center conductor; wherein said outer sheath, said middle conductor and said center conductor comprise a triaxial arrangement.
5. The catheter of claim 1 , wherein said outer sheath is a needle.
6. The catheter of claim 4 , wherein said middle conductor and said center conductor comprise a co-axial cable.
7. The catheter of claim 1 , wherein said drive frequency is 2.45 GHz.
8. The catheter of claim 4 , wherein said middle conductor extends from said outer sheath by a length.
9. The catheter of claim 8 , wherein said length that the middle conductor extends from said outer sheath is (2n−1)λ/4 where n is a non-zero positive integer.
10. The catheter of claim 8 , wherein said center conductor extends from said middle conductor by a length.
11. The catheter of claim 10 , wherein said length that said center conductor extends from said middle conductor is (2n−1)λ/4 where n is a non-zero positive integer.
12. The catheter of claim 11 , wherein n equals 2.
13. The catheter of claim 1 , wherein said non-conductive elements are configured to reduce heat generated at an ablation site by a distal end of said catheter from traveling to a proximal portion of said catheter.