Physics & Application of Radiofrequency for the treatment

of chronic pain

Erik SpeekenbrinkProject ManagerNeuroTherm

Two different treatments possible with RF

•Conventional RF (Heat-RF)•Pain relief is achieved by effectively breaking the nerve pathway to the brain through the application of heat

•Pulsed Radiofrequency•Pain relief is achieved by the application of an electro-magnetic field onto the nerve through small pulse bursts or radiofrequency energy

Conventional RF

• A current flows from the active tip of the electrode and heat is generated by the movement of charged ions in the tissue electrolytes

• The current is returned to the generator through a large area reference plate to prevent heating on this side of the circuit

480 kHz

Golden rules for heat RF

• Tip temperature and electrode geometry completely characterize the size and shape of equilibrium lesions

• Lesion size stops growing after 45 seconds because thermal equilibrium is reached

• The RF current heats the tissue and the tissue heats the electrode

• Use a tangential approach to the nerve

Temperature

Time dependance

Pulsed RF

Why is Pulsed RF usefull

• Because it is non-destructive

• Because it is safe- no reports of morbidity

• Because you can use it in areas you would not want to heat- e.g. peripheral nerves, DRG, C1

• Because it is easier on the patient

Pulsed RF protocol

• Pulse Amplitude should be set to 45 V

• If electrode temperature reaches 42 C, reduce the pulse amplitude or pulse width Note: 42C was never an endpoint!!

• Pulses should be delivered for 2-3 minutes

• Try to place needle perpendicular to the target, since the electric field is strongest near the tip

Pulsed RF misconceptions

• The goal is to apply pulsed RF at a level of 45 voltsWithout exceeding 42 C!

• It is not necessary to reach 42 C. In fact it is desirable to be between 38-42 C

What is commonly treated with RF/PRF

• Facet joints

• Medial branch neurotomy

• Dorsal root ganglion

• Trigeminal neuralgia

• Cordotomy

• Inter-vertebral Disc

• Peripheral nerves

Current developments

• Multiple output generators

• More flexible treatment parameters

• More efficient treatment algorithms

• Procedure specific electrodes

Simplicity electrode