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Microwaves, metal pellets, and neurosurgery

Vincent A Mazzarella vamg6792 at uxa.cso.uiuc.edu
Fri Apr 26 10:44:05 EST 1991

I saw something about the following potential neurosurgical
technology in a magazine article recently. Does anyone know
anything more about it?

A patient with a cerebral cancer has an MRI done to image the
tumour. A neurosurgeon would then drill a dime-sized hole in the
skull and implant a BB-sized neodynium-boron-iron pellet in the
dura.  (Neodynium-boron-iron is the strongest usable, permanent
magnetic material.)

The patient would then put his or her head into a helmet made of
non-magnetic stainless steel which would house six superconducting
magnetic manipulation coils cooled by liquid helium. Two biplanar
fluroscopes would be attached to the sides of the helmet for
visualization during the procedure.

The coils would apply a 0.04 N magnetic force to pull the metal
pellet through the brain folds and around critical structures to
the tumour bed at a speed of 1 mm/sec.

The neurosurgeon would control the direction of the pellet's
movement using a joystick connected to the workstation controlling
the magnetic coils. The progress of the movement would be monitored
by two magnet-resistant, biplanar fluoroscopes taking an image 4
/second. Their output would be superimposed upon sagittal, coronal,
and transverse images from the original MRI and displayed on three

When the pellet is in place, e.g. at the site of the tumour, radio
waves (microwaves) would be directed at the pellet, causing it to
heat to 140 - 150 degrees F, killing surrounding cells within a few
mm radius.

A potential problem seems to be hemorrhage, from manouevering the
pellet's progress through the brain. The rounded shape of the
pellet might minimize this possibility.

A second problem is the problem of how to assure the margins of the
tumour have actually been killed by the hyperthermia from the

Research on this technique is being carried out at the University
of Virginia, Charlottesville, and the University of Washington,
Seattle.  I am interested in knowing the successes of these
procedures and how often they have been tried.


Vincent Mazzarella
College of Medicine, Neuroscience Program
University of Illinois, Urbana-Champaign
e-mail: mazz at vmd.cso.uiuc.edu

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