This thesis focuses on the characterisation and modelling of the radio frequency (RF) lesioning with emphasis on size estimation in functional neurosurgery. A computer-assisted video system has been set up for standardised test and documentation of protein clots generated by RF-lesioning electrodes in an albumin solution. A standardised test is essential in comparing assessed results of the size and shape of protein clots generated using different parameters. This is beneficial to both the manufacturer oflesioning electrodes as well as the surgeon.

In an animal study, performed analogously to thalamotomy in man, the correlation in size between in vitro protein clots and in vivo lesions has been investigated. The result shows a high correlation between protein clots and lesions observed on MR images; and lesions observed on MR images and corresponding coagulated tissue in histological sectionings. This actualises the value of presurgical electrode tests to validate the electrode function and lesion size in vitro.

A finite element model has been set-up in order to facilitate studies of the growth and the temperature distribution during the lesioning process. Of the utmost importance is the finding of a difference in temperature between maximum temperature, located outside the electrode, compared to the intra-electrode (thermocouple) temperature.

A method for real time monitoring of lesion growth and estimation of lesion size utilising static and/or Doppler broadened laser light is proposed. Implemented in a surgical-assist system, this could give valuable guidance to the surgeon as to whether the desired lesion size is obtained or not and keep the destruction precise, but to a minimum.