1. Radioactive Seed Localization
Margarita Zuley, MD
Associate Professor of Radiology
University of Pittsburgh
Medical Director Breast Imaging
Magee Womens Hosp of UPMC

2. Thank you to Mike Sheetz University of Pittsburgh RSO

3. Background 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

4. Background 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

5. Benefits
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

6. Regulatory Oversight
PA Department of Environmental Protection Bureau of Radiation Protection regulates use of radioactive material (RAM) in medicine
Apply to DEP for a RAM license if not pre-existing
RSL is an off-label use of a device
Radiation Safety Office or Officer must be involved from the very beginning

7. Coordinated Program Radiation Safety Office
Oversees protocol of training/ implementation
Develops policies for handling
Develops policies for storage and transfer
Develops policies for lost/ damaged seeds

8. Training Requirements
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
Specific medical staff privilege for radiologists and surgeons
Annual refresher training

9. Radiation Safety Issues
Personnel Exposure
Inventory
Source Leakage
Surveys
Security

10. Radiation Exposure to the Population of the United States
Early 1980’s 2006
Effective Dose per Individual
In the U.S. Population (mrem)
Early 1980’s 2006
Effective Dose per Individual
In the U.S. Population (mrem)
Radiation Exposure to the Population of the United States
1980’s
Effective Dose per Individual
in the U.S. Population (mrem)
NCRP Report No. 160

11. Radiation Exposure Potential
Medical Imaging Doses
Dose Rate from 200 uCi
I-125 seed
Procedure
Effective Dose (mrem)
Chest x-ray 2
Mammogram 40
Abdomen x-ray
150
NM Bone Scan
400
Abdomen CT
600
Coronary CTA
1000
Distance (cm)
mrem/min 1 20 10
0.2
100
0.002
Annual Occupational Exposure Limits:
Whole body – 5000 mrem
Extremity – 50,000 mrem
Mettler et al. Radiology 2008

12. Radiation Safety 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)
Radiation dosimetry not required

13. Radiation Safety Issues
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

14. Coordinated Program 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

15. Consider seed movement
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

16. I-125 Seed Ordering
Order seeds separately and place them into needles in radiology
Have to consider sterility
Less expensive
Order prepackaged seeds that are already sterile

17. I-125 Seed Implant
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

18. I-125 Seed Implant 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)

19. Patient Instruction
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

20. Surgical Removal Of I-125 Seed
Identification of surgical patient containing I-125 seed
Handheld gamma probe is scanned across breast
Probe set at 27 keV to detect gamma radiation from I-125

21. Gamma Probe Spectrum for I-125 and Tc-99m

22. Surgical Removal Of I-125 Seed
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

23. Steps After Resection of Lesion
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

24. Surgical Concerns Cutting of radioactive seed
No dissection with scissors
Suctioning of seed from surgical site
Misidentification of I-125 seed radiation from Tc-99m sentinel node activity

25. Pathology 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

26. Pathology 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

27. Pathology
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