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Radioactive Seed Localization

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Presentation on theme: "Radioactive Seed Localization"— Presentation transcript:

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







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