Experimental exploration of equipment for stereotactic functional neurosurgery based on heating induced by radio-frequency current is most often carried out prior to surgery in order to secure a correct function of the equipment. The experiments are normally conducted in an experimental model including an albumin solution in which the treatment electrode is submerged, followed by a heating session during which a protein clot is generated around the electrode tip. The clot is believed to reflect the lesion generated in the brain during treatment. It is thereby presupposed that both the thermal and electric properties of the model are similar to brain tissue. This study investigates the presence of convective movements in the albumin solution using laser Doppler velocimetry. The result clearly shows that convective movements that depend on the time dependent heating characteristics of the equipment arise in the solution upon heating. The convective movements detected show a clear discrepancy compared with the in vivo situation that the experimental model tries to mimic; both the velocity (maximum velocity of about 5mms) and mass flux are greater in this experimental setting. Furthermore the flow geometry is completely different since only a small fraction of the tissue surrounding the electrode in vivo consists of moving blood, whereas the entire surrounding given by the albumin solution in the experimental model is moving. Earlier investigations by our group (Eriksson et al., 1999, Med. Biol. Eng. Comput. 37, pp. 737–741; Wren, 2001, Ph.D. thesis; and Wren et al., 2001, Med. Biol. Eng. Comput. 39, pp. 255–262) indicate that the heat flux is an essential parameter for the lesion growth and final size, and that presence of convective movements in the model might substantially increase the heat flux. Thus, convective movements of the magnitude presented here will very likely underestimate the size of the brain lesion, a finding that definitely should be taken into consideration when using the model prior to patient treatment.

1.
Gildenberg
,
P. L.
, 1998, “
Stereotactic Surgery—The Past and the Future
,”
Stereotact. Funct. Neurosurg.
1011-6125,
70
(
2–4
), pp.
57
70
.
2.
Giladi
,
N.
, 2000, “
The Role of Functional Neurosurgery in Parkinson's Disease
,”
Isr. Med. Assoc. J.
,
2
(
6
), pp.
455
461
.
3.
Dieckmann
,
G.
,
Gabriel
,
E.
, and
Hassler
,
R.
, 1965, “
Size, Form and Structural Pecularities of Experimental Brain Lesions Obtained by Thermocontrolled Radiofrequency
,” Confin. Neurol., Proceedings 2nd International Symposium on Stereoencephalotomy, Copenhagen, pp.
134
142
.
4.
Vinas
,
F. C.
,
Zamorano
,
L.
,
Dujovny
,
M.
,
Zhao
,
J. Z.
,
Hodgkinson
,
D.
,
Ho
,
K. L.
, and
Ausman
,
J. I.
, 1992, “
In Vivo and In Vitro Studies of the Lesions Produced with a Computerized Radiofrequency System
,”
Stereotact. Funct. Neurosurg.
1011-6125,
58
, pp.
121
133
.
5.
van den Berg
,
J.
, and
van Manen
,
J.
, 1962, “
Graded Coagulation of Brain Tissue
,”
Acta Physiol. Pharmacol. Neerl
0001-6748,
10
, pp.
353
377
.
6.
Moringlane
,
J. R.
,
Koch
,
R.
,
Schäfer
,
H.
, and
Ostertag
,
C. B.
, 1989, “
Experimental Radio-frequency (RF) Coagulation with Computer-Based on Line Monitoring of Temperature and Power
,”
Acta Neurochir.
0001-6268,
96
, pp.
126
131
.
7.
Eriksson
,
O.
,
Wårdell
,
K.
,
Eriksson-Bylund
,
N.
,
Kullberg
,
G.
, and
Rehncrona
,
S.
, 1999, “
In Vitro Evaluation of Brain Lesioning Electrodes (Leksell®) Using a Computer-Assisted Video System
,”
Neurol. Res.
0160-6412,
21
, pp.
89
95
.
8.
Wren
,
J.
,
Eriksson
,
O.
,
Wårdell
,
K.
, and
Loyd
,
D.
, 2001, “
Analysis of Temperature Measurement for Monitoring Radio-Frequency Brain Lesioning
,”
Med. Biol. Eng. Comput.
0140-0118,
39
, pp.
255
262
.
9.
Wren
,
J.
, 2002, “
On Medical Thermal Treatment — Modelling, Simulation and Experiments
,” Ph.D. thesis, Linköpings Universitet, Linköping, Sweden.
10.
Christensen
,
D. A.
, and
Durney
,
C. H.
, 2000,
Basic Introduction to Bioelectromagnetics
,
CRC
, New York.
11.
Haines
,
D. E.
, and
Watson
,
D. D.
, 1989, “
Tissue Heating During Radio Frequency Catheter Ablation: A Thermodynamic Model and Observations in Isolated Perfused and Superfused Canine Ventricular Free Wall
,”
Pacing and Clinical Electro-physiology
,
12
, pp.
962
976
.
12.
Labonté
,
S.
, 1992, “
A Theoretical Study of Radio-Frequency Catheter Ablation
,” Ph.D. thesis, University of Ottawa/Ottawa–Carlton Institute for Electrical Engineering, Ottawa, Canada.
13.
Wonnell
,
T. L.
,
Stauffer
,
P. R.
, and
Langberg
,
J. J.
, 1992, “
Evaluation of Microwave and Radio Frequency Catheter Ablation in a Myocardial-Equivalent Phantom Model
,”
IEEE Trans. Biomed. Eng.
0018-9294,
39
, pp.
1086
1095
.
14.
Eriksson
,
O.
, 1999, “
Characterisation of Brain Lesioning Electrodes for Ablative Neurosurgery
,” Licentiate thesis, Linköping University, Linköping, Sweden.
15.
Goldstein
,
R. J.
, ed., 1996,
Fluid Mechanics Measurements
,
2nd ed.
,
Taylor and Francis
, Basingstoke, UK.
16.
Adrian
,
R. J.
, 1983, “
Laser Velocimetry
, in
Fluid Mechanics Measurements
,
R. J.
Goldstein
, ed.,
Springer
, Berlin, Chap. 5, pp.
155
240
.
17.
Karlsson
,
R. I.
,
Alavyoon
,
F.
, and
Eklund
,
A.
, 1990, “
LDV Measurements of Free Convection in Electrochemical Systems, in Laser Anemometry
,”
Proceedings of the 3rd International Conference
, Swansea, Wales, Sept. 26–29, 1989,
J. T.
Turner
, ed.,
Springer
, Berlin, pp.
329
337
.
18.
Tungjitkusolmun
,
S.
,
Woo
,
E. J.
,
Cao
,
H.
,
Tsai
,
J.-Z.
,
Vorperian
,
V. R.
, and
Webster
,
J. G.
, 2000, “
Thermal–Electrical Finite Element Modelling for Radio-Frequency Cardiac Ablation: Effects of Changes in Myocardial Properties
,”
Med. Biol. Eng. Comput.
0140-0118,
38
, pp.
562
568
.
19.
Eriksson
,
O.
,
Wren
,
J.
,
Loyd
,
D.
, and
Wårdell
,
K.
, 1999, “
A Comparison Between In Vitro Studies of Protein Lesions Generated by Brain Electrodes and FEM Simulations
,”
Med. Biol. Eng. Comput.
0140-0118,
37
, pp.
737
741
.
20.
Wren
,
J.
,
Karlsson
,
M.
, and
Loyd
,
D.
, 2001, “
A Hybrid Equation for Simulation of Perfused Tissue During Thermal Treatment
,”
Int. J. Hyperthermia
0265-6736,
17
, pp.
483
498
.
You do not currently have access to this content.