Radioactive Seed
Localization
Margarita Zuley, MD
Associate Professor of Radiology
University of Pittsburgh
Medical Director Breast Imaging
Magee Womens Hosp of UPMC
Thank you to Mike Sheetz
University of Pittsburgh RSO
Background
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Significantly decayed I-125 seeds used for
brachytherapy
Assayed activity approx 200 microcuries
Half-life of I-125 is 60 days
Can be placed into the breast like a biopsy clip
easily with ultrasound or mammography
guidance
Background
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Work pioneered by Mayo Clinic
Almost no contraindications to placement
Used to localize lesion in breast for surgical
excision
Emit a different frequency energy than Tc-99m
and so can be detected in the OR even with a
sentinel node injection of Tc-99m
Benefits
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Studies indicate reduced incidence of positive
margins compared to wire localization
Allows for improved surgical approach and
removal of lesion
Reduces scheduling conflicts between surgeon’s
and radiologist’s offices
Regulatory Oversight
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PA Department of Environmental Protection
Bureau of Radiation Protection regulates use of
radioactive material (RAM) in medicine
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Apply to DEP for a RAM license if not pre-existing
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RSL is an off-label use of a device
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Radiation Safety Office or Officer must be involved
from the very beginning
Coordinated Program
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Radiation Safety Office
 Oversees protocol of training/
implementation
 Develops policies for handling
 Develops policies for storage and transfer
 Develops policies for lost/ damaged seeds
Training Requirements
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Didactic training provided by RSO on RSL
policies and procedures
Supervised work experience
Radiologist – minimum of 2 cases
 Surgeon – minimum of 1 case
 Pathologist or PA – minimum of 1 case
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Specific medical staff privilege for radiologists
and surgeons
Annual refresher training
Radiation Safety Issues
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Personnel Exposure
Inventory
Source Leakage
Surveys
Security
Effective Dose per Individual
In the U.S. Population (mrem)
360
Early 1980’s 2006
620
Radiation Exposure to the Population of the
United States
Effective Dose per Individual
in the U.S. Population (mrem)
1980’s
360
2006
620
NCRP Report No. 160
Radiation Exposure Potential
Dose Rate from 200 uCi
I-125 seed
Medical Imaging Doses
Procedure
Effective Dose
(mrem)
Distance (cm)
mrem/min
1
20
Chest x-ray
2
10
0.2
Mammogram
40
100
0.002
Abdomen x-ray
150
NM Bone Scan
400
Abdomen CT
600
Coronary CTA
1000
Annual Occupational Exposure Limits:
Whole body – 5000 mrem
Extremity – 50,000 mrem
Mettler et al. Radiology 2008
Radiation Safety
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ALARA Philosophy (As Low As Reasonably
Achievable)
Radiation Protection Measures
Time (plan in advance)
 Distance (reverse action tweezers)
 Shielding (lead containers for transport and storage)
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Radiation dosimetry not required
Radiation Safety Issues
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Inventory - Constant tracking of seed with
computerized inventory system
Source Leakage – Radioactivity is sealed inside
titanium wall which is “soft” and can be easily cut
Surveys – Radiation monitoring is performed with
gamma probe or NaI meter to locate seed
Security – Seeds must be kept in secured area or be
under supervision of authorized individual
Coordinated Program
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Radiologist
Surgeon
Pathologist
Administrators
All clinicians must have initial training by
someone skilled in the procedure.
Can have a super user in each specialty that
trains peers
Form a team with the RSO to implement the
program
Consider seed movement
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Order and receipt in Nuclear Medicine
Storage in Breast Imaging
Placed under US or mammo guidance
Surgical removal in OR
Specimen radiography in breast imaging
Seed removed from specimen in pathology
Used seeds stored in breast imaging
RSO picks up spent seeds for disposal
I-125 Seed Ordering
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Order seeds separately and place them
into needles in radiology
Have to consider sterility
 Less expensive
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Order prepackaged seeds that are
already sterile
I-125 Seed Implant
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Prescription for implant completed and signed
by radiologist prior to implant
Seed implanted under radiographic or ultrasonic
guidance by authorized radiologist
Confirmatory mammogram taken to verify seed
placement
Survey of room performed to assure seed not
dropped or cut
I-125 Seed Implant
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Seed is positioned at the
center of the lesion
Seed cannot be repositioned
Rare incidence of seed
migration
Surgery to remove seed
must be scheduled within 1
half life (60 days)
Patient Instruction
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Patient provided written information on
radioactive seed localization option from
surgeon
No special instruction given to patient with
respect to radiation exposure to others
Emphasis that patient must return for scheduled
surgery to remove radioactive seed
Surgical Removal Of I-125 Seed
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Identification of
surgical patient
containing I-125 seed
Handheld gamma
probe is scanned across
breast
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Probe set at 27 keV to
detect gamma radiation
from I-125
Gamma Probe Spectrum for I-125 and Tc99m
Surgical Removal Of I-125 Seed
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Point of greatest
activity locates seed
and lesion
Surgical incision is
made over “hot spot”
Gamma probe is used
to guide the excision
of the lesion
Steps After Resection of Lesion
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Survey specimen with gamma probe to confirm
presence of radioactive seed
Survey surgical site to confirm absence of
radioactive seed
Place specimen in plastic container, label with
radiation sticker, transport to Breast Care Center
for radiograph
Surgical Concerns
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Cutting of radioactive seed
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No dissection with scissors
Suctioning of seed from surgical site
Misidentification of I-125 seed radiation from
Tc-99m sentinel node activity
Pathology
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Specimen transported from
BCC back to OR/Pathology
lab
Number of seeds in specimen
noted on container lid
Locate seed(s) in specimen
using radiograph and/or
gamma probe
Pathology
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Remove seed using scalpel
(no scissor dissection)
Place seed into plastic vial
with patient RX number using
reverse action tweezers,
secure cap, and put vial in
lead pig
Pathology
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Scan breast tissue specimen with gamma
probe before releasing for sectioning
Complete seed removal log sheet
Breast Care Center techs will pick-up
container with radioactive seed(s) at end of
day