Radiofrequency Nerve Lesioning For Pain Relief.

Title: Radiofrequency Nerve Lesioning For Pain Relief.

Author        : Bassant Mohamed Abd El-Fatah Badwy 
Collection   : M.Sc. Electric

Abstract:

Actually, pain is a self-protective mechanism, where the sense of pain occurs as the brain’s response toelectrical and chemical changes that appear as a result of injury, disease or damage to the body. Pain is anunpleasant sensory experience distinct from other sensory modalities such as touch, warmth, and cold. Patient has been curious to fmd relief from this problem and has made sustained efforts to discover answer for pain. Pain is transmitted through nociceptors which are sensory neurons that respond to potentially damaging stimuli by sending nerve signals to the spinal cord and brain.The adjective ”Radio frequency” (RF) is currently used to describe a variety of percutaneous procedure used in medicine. RF lesioning, or RF ablation, is a method that uses high frequency currents for thermal coagulation of pathological tissue or signal pathways. The current is delivered from an electrode, which also contains a temperature sensor permitting control of the current at a desired target temperature. RF is minimally invasive technique has been used to alleviate pain. RF lesioning blocks the pain signal sensation and interrupt the nociceptive pathways at various levels and effectively control pain on long-term basis. RF lesioning technique is based on heating the target nerve by the application of RF current. A portion of the nerve is thermally coagulated and then prevents the pain signal transmission to the brain. An RF lesion generator is used to produce high frequency energy of 500 KHz similar to one used in radio transmitters.

Finite element models (FEMs) have been widely used to calculate the lesion size and temperature distribution around the RF electrode tip. It divides the solution domain into a finite number of elements. The process of discretization converts the continuous problem into a pro blem with a fmite number of unknowns within each element.

The present thesis focuses on modeling and simulation of the medium surrounding the RF electrode used for nerve lesioning with the aim of gaining better understanding and predictability of the nerve lesioning process. A few numbers of FEMs had been used to simulate the nerve lesioning based on a simplified model, where the area surrounding the RF lesioning electrode was assumed a homogenous tissue. The objective of the present thesis is to study the influence of inhomogeneous environment surrounding the RF electrode on lesion size and temperature distribution, where the case of the facet joint denervation is modeled as an example of inhomogeneous medium.

The results are compared with the homogeneous case. Also the electric conductivity as function of temperature is considered in the homogeneous and inhomogeneous medium and its effect on the temperature distribution and lesion size is investigated.

For pulsed radiofrequency (PRF) mode, an FEM is constructed to calculate the value of hot flashes to see how much its effect extend. The results obtained from the inhomogeneous model are more realistic than that obtained with homogeneous model, where the constructed inhomogeneous model describes the actual physical situation surrounding the RF electrode. So, the effect of other tissues around the target nerve in the lesioning area must be taken into consideration in the calculation of lesion Size.