MD Anderson OncoLog, Volume 44, Number 10, October 1999 Page: 3
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Accuracy
Essential in
Stereotactic
Radiosurgery
Jim Lii holds a
imiiagnifying glass
in front of one eye
and stares intently at the
image of a laser beam that
appears to be exactly in
the center of a pair of
tiny lines engraved on a
target that is mounted
on top of a mechanical
isocenter stand in a
radiation therapy treat-
ment room. He is not
satisfied.
"You see how the laser
beam is touching the
line?" Lii asks. "It should
not be touching."
As Lii makes miniscule
adjustments to the wall-mounted laser by remote
control, fellow medical
physicist Jin-Song Ye
explains that the beam is
between 0.10 and 0.20
mm from the isocenter,
well within the allowable
accuracy of 0.25 mm.
"ButJim is trying
to be exact," Ye says.
The two medical
physicists are performing
a quality assurance check
in preparation for a
stereotactic radiosurgery
procedure at The Univer-
sity of Texas M. D. Ander-
son Cancer Center. They
have spent the morning
participating in the
acquisition of a patient's
computed tomographic
images, performing
treatment planning on a
computer, and transfer-ring the BRW coordinates
of the center of the
treatment target to a
metal frame known as
a rectilinear phantom
pointer (RLPP), which
serves as a model of the
patient's head. The RLPP
is attached to a laser
target localizer frame and
to the treatment couch of
the linear accelerator. A
tungsten ball is placed
within the RLPP in the
exact location of the
center of the treatment
target within the patient's
head, and film shots are
taken to verify its align-
ment. During SRS, all
the radiation beams will
crossfire through the
center of this point.
Lii and Ye spend
30-45 minutes applyingthe same sub-millimeter
precision to checking
and double-checking the
positions of the RLPP,
the laser target localized
frame, and the treat-
ment couch during the
patient's treatment. They
even make adjustments
to allow for the weight
of the machine's gantry
as it rotates around the
treatment couch, the
weight of the patient's
head, and the ever-so-
slight tilt of the treatment
couch.
"Everything we do
here is for one purpose,"
Ye says. "We want to place
the center of the treatment
target, the patient's tumor,
at the radiation isocenter
of the linear accelerator."PROTOCOLS
Patients aged 16-75 years with newly
diagnosed single brain metastases who
are candidates for both conventional
surgical resection and stereotactic
radiosurgery (SRS) will be randomly
chosen to undergo surgery or SRS.
After the initial procedure, patients will
return for follow-up once a month for
the first two months and then every two
months thereafter. Patients must have a
life expectancy of at least four months,
be able to care for themselves, have
adequate bone marrow and platelet
function, and have no active, uncon-
trolled infection. Patients who require
immediate treatment to prevent neuro-
logical deterioration are not eligible for
this study. Evidence of leptomeningeal
disease, prior radiation therapy to the
brain, prior radioiodine treatment, and a
primary tumor that is extremely radi-
osensitive are all criteria for exclusion.Patients who are pregnant or breast-
feeding are ineligible.
" A prospective randomized trial of
surgery with whole-brain radiation
therapy versus whole-brain radiation
therapy alone in the treatment of
multiple brain metastases (ID98-028).
Physician: Raymond Sawaya, M.D.
This phase III study includes both
inpatient and outpatient procedures for
patients with newly diagnosed multiple
brain metastases determined by MRI.
Patients will return for follow-up at one
month and two months after treatment
and every two months thereafter. To
participate, patients may have no more
than three lesions, and all lesions must
be resectable. A life expectancy of at
least four months is required, and
patients must be candidates for conven-
tional surgical resection. If a neurosur-geon and radiation oncologist determine
that all of a patient's brain tumors
necessitate surgical resection, the
patient is not eligible. Patients who have
an extremely radiosensitive primary
tumor, have received prior radiation
therapy to the brain or prior radioiodine,
have evidence of leptomeningeal
disease, or are pregnant or breast-
feeding are ineligible..
FOR MORE INFORMATION about these clinical
trials, physicians or patients may call
the M. D. Anderson Information Line.
Those within the United States should
call (800) 392-1611; those in Houston
or outside the United States should
call (713) 792-6161. Visit the M. D.
Anderson Cancer Center clinical trials
web site at http://www.clinicaltrials. org
for a broader listing of treatment research
Protocols.MD Anderson OncoLog / 3
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University of Texas M.D. Anderson Cancer Center. MD Anderson OncoLog, Volume 44, Number 10, October 1999, periodical, October 1999; Houston, Texas. (https://texashistory.unt.edu/ark:/67531/metapth903678/m1/3/: accessed April 25, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu; crediting UNT Libraries Government Documents Department.