025-0169-311 Revision: B
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9
Standard RF Lesion Size
Lesion size and shape is determined by numerous factors including:
•
cannula active tip length
•
cannula active tip diameter
•
impedance of tissue
•
current intensity
•
length of time that energy is applied
One published approximation method for lesion size and shape describes a lesion as a prolate spheroid in shape with
the major axis = 2 x length of the active tip and the minor axis = 2/3 the major axis.
1
This approximation is valid for
active tip lengths of up to 5 mm.
Eg: based on Active tip = 5 mm (0.197”)
Major axis = 10mm (0.394”)
Minor axis = 6.7mm (0.263”)
For active tip lengths in excess of 5 mm, the active tip diameter will primarily dictate the minor axis dimension of the
lesion. The maximum minor axis dimension will not typically exceed 8 mm for 18 to 22 gauge cannulae.
Note: In Multi-RF Auto Temp mode, maintain a minimum distance of 10 mm between probe tips and ensure that the
probe tips do not touch.
So long as this distance is maintained, all lesions formed will be non-contiguous.
1- ORGAN, L.W.: Electrophysiologic Principles of Radiofrequency Lesion Making. Appl. Neurophys. 39:69-76
Minor Axis = (2/3)M
Major axis (M) = 2L
