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Pate, Brad (ed.) / Wisconsin engineer
Volume 110, Number 3 (April 2006)

Hersch, A.; Kamenski, P.
Direct from the source: minimizing the negative effects of cancer treatment,   pp. 16-17 PDF (906.7 KB)

Page 16

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By Alauna Hersch and Paul Kamenski
A lbert Einstein once said, "The secret to
creativity is knowing how to hide
your sources." Little did he know that
his thoughts on plagiarism would be the key
to a newly optimized treatment for prostate
Douglass Henderson, professor of engineer-
ing physics, and Bruce Thomadsen, associate
professor of medical physics, collaborated to
come up with a new technique for treating
prostate cancer. This treatment will more
accurately and effectively radiate cancerous
tissue and, in the process, minimize damage to
Radioactive sources, no larger than a
grain of rice, are injected into the
prostate to treat cancerous tissue.
surrounding healthy tissue. Doctors insert
small radioactive sources into the prostate.
These sources are shielded on specific sides to
direct radiation toward cancerous regions.
Their new three-component approach com-
bines use of these sources with robotics and
optimization software to decrease the deleteri-
ous effects of radiation on healthy tissue.
Prostate cancer is treated through the implan-
tation of radioactive sources into the cancer-
ous region of the prostate. Currently, doctors
implant these radioactive sources by use of a
sieve-like grid with aid from an ultrasonic
view of the prostate. However, this grid limits
source placement options.
"We couldn't put sources where we wanted
them because there wasn't a hole there,"
Thomadsen says. This inaccuracy inevitably
results in uneven dose distributions and the
irradiation of healthy tissue.
Thomadsen began working on the robotics
part of the invention in 1991, with the goal of
increasing the accuracy of source placement.
Robots are typically used because they are, as
Thomadsen says, "very stable and precise."
The robot is able to align the radioactive
sources at different angles, which is not possi-
ble through the use of the grid template.
When Henderson entered the picture, he
helped improve this treatment method. He
came up with the idea of shielding the
sources. A thin gold strip is inserted into the
source in order to direct the radiation toward
cancerous tissue and away from healthy tis-
sue. This shielding significantly lowers radia-
tion to protect sensitive areas. This allows doc-
tors to, according to Thomadsen, "put sources
in the prostate right next to the urethra or on
the edge of the rectum." By strategically ori-
enting the sources, doctors can direct the radi-
ation toward cancerous areas. Their use of
these directional sources, in addition to tradi-
tional non-shielded sources, will help increase
treatment effectiveness.
Henderson also developed a new computer
optimization process to further improve the
precision and speed of the source placement.
Before implantation, software initially maps
out the calculated placement of all sources.
However, due to inaccuracies in the place-
ment procedure, sources do not always end
up exactly where they are supposed to be.
Older software did not adjust for this occur-
rence, but the new program recalculates
where to put subsequent radioactive sources
based on the actual location of previous
sources. The speed of this program will allow
patients to come for only one visit, compared
16   APRIL 2006

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