In vitro evaluation of brain lesioning electrodes (Leksell (R)) using a computer-assisted video system

Radiofrequency (RF) generated thermal brain lesions are widely used in func tional neurosurgery. The size, shape and development of the lesions depends on system parameter settings and the electrode configuration. Difficulties in studying the effect of these factors in vivo stimulated us to develop a n in vitro system for standardized comparison between different electrodes and physical parameters. A computer-assisted video system was set-up allowi ng continuous video recording of RF-generated coagulations in either a stan dard albumin solution or in the fresh white of a hen's egg as transparent t est substrates. Ten lesions were made with each test electrode (two bipolar and three monopolar) in each of the two substrates at 70 degrees, 80 degre es and 90 degrees C (t= 60 sec). Due to the better homogeneity the lesions in the albumin solution were much more regular and reproducible. This made it possible to calculate the size (width 2.2 +/- 0.7 to 5.3 +/- 0.1 mm and length 3.0 +/- 0.1 to 8.1 +/- 0.3 mm) as well as the volume (8.5 +/- 1.4 mm (3) to 133.5 +/- 26.8 mm(3)). It is concluded that this in vitro system off ers a reproducible way to study and document the effect of different electr ode configurations and RF-generator settings on the formation of a heat les ion. Even lithe results are not directly applicable to the living human bra in they give an estimate of the form and size of a coagulation lesion and c an be of value for standardized comparisons between different electrodes.