Electrosurgical instrument
Electrical instrument for applying radiofrequency and/or microwave frequency energy to tissue, comprising: a distal part comprising an instrument tip for applying radiofrequency and/or microwave frequency energy to tissue, the instrument tip comprising first and second conductive elements; a coaxial feed cable comprising an inner conductor, a tubular outer conductor coaxial with the inner conductor, and dielectric material separating the inner and outer conductors, the coaxial feed cable being for conveying radiofrequency and/or microwave frequency energy to the distal part; wherein: the inner conductor is electrically connected to the first conductive element and the outer conductor is electrically connected to the second conductive element through a rotatable connection between the distal part and the coaxial feed cable that allows rotation of the distal part relative to the coaxial feed cable; and the instrument comprises an actuator for rotating the distal part in a first rotational direction relative to the feed cable.
1. An electrosurgical apparatus for applying radiofrequency energy and/or microwave frequency energy to biological tissue, the apparatus comprising:
a distal part comprising an instrument tip for applying radiofrequency energy and/or microwave frequency energy to biological tissue, wherein the instrument tip comprises a first conductive element and a second conductive element;
a coaxial feed cable comprising an inner conductor, a tubular outer conductor coaxial with the inner conductor, and a dielectric material separating the inner and outer conductors, the coaxial feed cable being for conveying radiofrequency energy and/or microwave frequency energy to the distal part; and
a generator connected to a proximal end of the coaxial feed cable, the generator being configured to supply microwave frequency energy having a predetermined wavelength λ to the coaxial feed cable;
wherein:
the inner conductor is electrically connected to the first conductive element and the outer conductor is electrically connected to the second conductive element through a rotatable connection between the distal part and the coaxial feed cable that allows rotation of the distal part relative to the coaxial feed cable about a central axis of the distal part;
the apparatus comprises an actuator for rotating the distal part in a first rotational direction relative to the coaxial feed cable; and
wherein a length of the instrument tip is substantially equal to
λ
2
.
wherein the distal part comprises an impedance transformer that substantially matches a characteristic impedance of the coaxial transmission line to a characteristic impedance of a tissue load in contact with the instrument tip at the predetermined frequency, and
wherein the distal part further comprises a section of coaxial transmission line between the impedance transformer and a proximal end of the instrument tip.
2. The electrosurgical apparatus according to claim 1 , wherein the predetermined frequency is 5.8 GHz.
3. The electrosurgical apparatus according to claim 1 , wherein a length of the impedance transformer is substantially equal to
(
2
n
+
1
)
λ
4
,
where n is an integer number greater than or equal to zero and λ is the wavelength of the microwave frequency energy in the impedance transformer at the predetermined frequency.