File - Patty Sponseller, CMD

Report
Gynecological Treatment
Planning
Patty Sponseller, CMD
Cervical Cancer
Simulation
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Patient supine
Lower extremities
immobilized
indexed to table
Table indexing documented
on device
Simulation
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Radiopaque gold seed markers at
cervix and distal vaginal DZ.
No standard EBRT fields.
Block based on 3D imaging
Treat AP/PA or 4 field pelvis
Patient simulated supine with CT
planning.
Rectal and vaginal marker
Field arrangement depends on body
habitus
Field Borders
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Superior = L4/5
Inferior = 3 cm below gold seed
most inferior involvement (often at
obturator foramen)
Lateral = 2 cm lateral to pelvic brim
Posterior = Include entire sacrum
Anterior = 1 cm anterior to sym
pubis
AP Pelvis
Lateral Pelvis
AP/PA DD
4 Field Pelvis
Tx inguinal nodes Stage IIIA
Increased
Lower
Border for flash
Common iliac nodes involved superior
border to L3-4
Increase sup
Border about 4cm
RT for para-aortic nodes
Superior border
T12-1
If conformal fields block kidneys
Laterally
encompass transverse
processes
IMRT for para-aortics better to spare
both kidneys and sm bowel
Purple is
50% isoline
Doses
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Doses vary with staging
From IA post hysterectomy with
Brachytherapy
To IIIB-IVA WP (50-54Gy) Brachy
boost and Para-aortic LN IMRT (4560 Gy)
Midline Block
When midline block used
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If 4 fld pt TX with AP/PA
Avoids excess dose to areas
adjacent to implant
Reduces dose to bladder and
rectum
After 54Gy boost to 60 Gy
Dose
What is the dose
under the 5%
transmission
block?
Calculate
dose
here
Dose to point under block
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Primary transmission through the
block is only 5%
Dose under the block is about 20%
of the dose in the open portion
Due to the internal scatter from the
open field areas
Endometrical Cancers
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Uterine Carcinomas
Leimyosarcoma, Endometrial
Stromal Sarcomas
Adenosarcoma
Uterine Sarcoma
Simulation
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Patient supine with lower
extremities immobilized
Empty rectum and full bladder
Whole Pelvis RT Borders
Superior = L5-S1
 Inferior = below obturator canal
and including upper 1/2 -2.3 vagina
 Lateral = 2 cm lat pelvic brim
 Posterior = split sacrum to S3
 Anterior = pubic symphysis
*Consider IMRT with careful target
delineation
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Dose Prescriptions
Post-op WP 1.8 Gy 45-50.4 Gy
followed with VC (vaginal cuff) boost
Pre-op WP 1.8 Gy to 45 Gy with T&O
Paraaortic to 45-50 Gy with
enlarged unresect LN boost to 60
Gy (IMRT)
Ovarian Cancer Simulation
Supine, lower extremity immobilization
 Image entire peritoneal cavity
 Treat open field AP/PA
 Borders (historical) sup = above
diaphragm
Inf = below obturator foramen
Lat = outside peritoneum
RT primarily reserved for palliative DZ
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Brachytherapy
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Teletherapy (linear accelerator RT) is
treatment at a distance 100 cm
Brachytherapy comes from the Greek
word brachy which means short
Radiation is placed near to in the tumor
High dose of radiation delivered with rapid
fall off
Radiation used is an Isotope
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Atoms having
nuclei with the
same # of protons
and different # of
neutrons
Atom decays
giving off radiation
Brachytherapy HDR
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Uses a 10 Curie
source of Iriduim 192
HL = 74.22 days
Complicated gamma
spectrum ave energy
.38 MeV high activity
Deliver dose in
temporary placed
catheters, applicators
or needles placed in a
patient
Source embedded in a wire
http://www.varian.com/us/oncology/brachytherapy/hdr_brachytherapy.html
HDR Treatment Unit Robot
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Catheter is attached
to applicator then to
channel on the unit
Wire with source goes
to preplanned
positions in the
applicator “dwell
positions” to deliver
correct amount of
radiation
Units are made by
different vendors
Nucletron
Applicator placement
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Placed with or without sedation
Depending on type of applicator
Patient then imaged on Simulator or
CT sim
Plan created on TPS
Before TX applicator position then
verified with conebeam or portal
imaging
Gynecological cancers
2 basic types of HDR implants
Tandem and Ring
Miami vaginal cylinder
Tandem and Oviods (shielded colpostats)
Vaginal Cylinder
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Deliver dose to the
vaginal cuff or
vaginal wall
Dose is calculated
at a distance from
the surface of the
applicator
Not much dose to
the rectum or
bladder
6 Gy line
GOG Definitiion
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Points A
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Points B Point B is 5 cm
represent medial
parametrium/lateral cervix,
the approximate point at
which the ureter and uterine
artery cross.
lateral to the center of the
pelvis at the same level
as point A and
approximates the region
of the obturator nodes or
lateral parametrium
http://imaging.ubmmedica.com/cancernetwork/cmhb11/11_20
_Fig_2.gif
ICRU report #38
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Rectum- 5mm posterior to posterior
vaginal wall (as identified by vaginal
packing) and bisecting ovoids
superiorly and inferiorly
Bladder- Posterior most point of a
7cc Foley balloon (with contrast) on
lateral film and bisecting on AP film
T&R or T&O
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Dose calculated to
Points “A” 2cmsup and
lat to the cervical os
(vaginal fornices)
Point B 3cm lateral to
A approx 1/3-1/4
dose to A
Calc bladder and
rectal doses or DVH
Radiopaque packing to
minimize dose to
bladder and rectum
Dwell positons
Lateral T & O
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Bladder and rectal
Dose
Characteristic Dose Distribution
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“Pear” shaped
dose distribution
Middle portion of
implant DD from
tandem
Inferior DD round
out to treat
cervical fornices
Verification
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Before treatment room survey
Verify correct channel to applicator
Verify CORRECT catheter length
Patient identity by 2 means
After delivery first person to enter
the room carries the survey meter!
Before TX “Dry Run”
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Before the Ir
source leaves the
robot housing a
dummy source is
sent through the
applicators
This checks for
any errors and
patency with the
catheters and
verify positions
http://chapter.aapm.org/GLC/media/2011/tollenaar.pdf
Verify your activity!
A=
Aoe-( 0.693t/T1/2 )
t = days since calibration of
initial activity
T ½ = Half life of isotope
Ao = Initial activity
A = Activity on you plan
Safety when working with
Radionuclides
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Keep time spent as short as
possible
Increase distance away from the
source (not a good idea to use the
HDR delivery robot as an arm rest)
Shielding- the safest place working
around the HDR unit is behind the
source!
Reportable Errors and Medical Events
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Wrong dose of
more than 10%
with a radioactive
source
Wrong patient
Wrong source
Leaking source or
non-removed
source
National Regulatory Commission
(NRC) or Agreement State
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NRC sub-division of Dept of Energy
Regulates radioactive material and establishes
reporting procedures
NRC and state agree to transfer authority of
radioactive materials to the state called and
“agreement state”
NRC then regulates only federal facilities
State regulates PET scanners, Linacs, and naturally
producing and cyclotron produced radionuclides
States that are not agreement states
Montana, Idaho,
Wyoming, South
Dakota, Missouri,
West Virginia,
Virginia, Pennsylvania,
Delaware, New Jersey,
Rhode Island,
Vermont, Michigan,
Indiana, District of
Columbia, Alaska,
Hawaii
Indiana Incident
http://chapter.aapm.org/GLC/media/2
011/tollenaar.pdf

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