Experimental determination of the force required for insertion of a thermoseed into deep brain tissues

Abstract

Our laboratories are developing a new technique for delivering localized hyperthermia to deep-seated brain tumors. In this technique, a spherical thermoseed is stereotactically navigated through the brain and tumour tissues via the noncontact application of an external magnetic force. The force required to produce motion of a 3 mm diameter sphere through in vitro brain tissues was measured to be 0.07 +/- 0.03 N. This result was obtained from a series of experiments performed on whole brain specimens extracted from adult canines. Data were also taken with a 3 mm x 3 mm cylinder and a 5 mm sphere. An experimental procedure simulating physiological conditions was developed prior to testing. Evaluations of systematic effects included determinations of the calibration uncertainties, tests of the dependence of the measured force on temperature, and studies of the effects of method of storage of the tissue specimens. The results obtained are compared with (and confirmed by) two different series of experiments performed in vivo on adult canines and with another series of experiments using brain phantom gelatin.

Microrobots for Minimally Invasive Medicine

“…A great deal of research has dealt with wireless manipulation of magnetic seeds in the brain for the purpose of hyperthermia, and a number of prototype systems have been developed by a collaboration between the University of Virginia and the University of Washington (38)(39)(40)(41). This research was accompanied by an experimental investigation of the forces required to move the seed within the brain (42). Kósa et al propose a swimming microrobot for endoscopic procedures in the subarachnoid space of the spine (43).…”

Amorphous Silicon Carbide Platform for Next Generation Penetrating Neural Interface Designs

“…The critical buckling load is the maximum axial load a shank can experience that will not cause lateral deflections. For a microelectrode shank to successfully penetrate the pia mater of a rat brain it is generally expected that its critical buckling load to be larger than tissue insertion force estimated to be approximately 0.5 to 2 mN [ 50 , 51 , 52 , 53 , 54 ]. Since the moment of inertia of the cross-section, which influences critical buckling load, depends greatly on the thickness of the shank, COMSOL Multiphysics v. 5.2 (COMSOL AB, Stockholm, Sweden) finite element modeling was used to predict the critical buckling load of a 2 mm long shank when the a-SiC thickness is increased from 4 µm to 6 µm.…”

Magnetic insertion system for flexible electrode implantation

“…While studies have been performed to determine the force required to penetrate neural tissue (Howard et al, 1999;Howard et al, 1989;Molloy et al, 1990), the brain is a viscoelastic structure. Probe velocity and geometry will affect the required penetration force.…”