Answer to Question #6159 Submitted to "Ask the Experts"

Thank you for your question. My full answer might be more than you're asking, but I've included some specifics anyway. Basically, the answer is that there is little risk and there are ways to minimize your exposure. Disposal of the tissues depends on the amount of activity left in the implant—if it is greater than two years since the implant, all the tissues can go in biohazard waste. If it is less than two years since the implant, the seeds should be retrieved and kept for radioactive decay. If we assume the patient was allowed to leave the hospital, technically, you don't have to store the seeds for decay, but it is the prudent thing to do. Also, staff would not need to wear a dosimeter.

Here's my full answer:
Radioactive bodies present two types of hazard: external exposure and radioactive contamination. The level of each of these is dependent upon the type and activity of radiation in the body, whether the body will be opened, days since administration of the radioactive material, and time to be spent in the vicinity of the body. External exposure is the primary concern if the body will not be opened. Individuals will rarely encounter high exposure rates around bodies of patients who were released from a hospital.

General Precautions
Reducing time, increasing distance, and using shielding are methods to decrease radiation exposure. Minimizing time will be the principal external exposure reduction method for individuals performing autopsies. Time is linear with exposure; decreasing time to perform a procedure by half will reduce exposure by half.

Extremity exposure can be reduced through the use of long-handled instruments because of the additional distance. Distance is inversely proportional to the square of the exposure; increasing distance by a factor of two will decrease exposure by a factor of four. Shielding, such as a radiology lead apron (0.5 mm lead equivalent thickness), will provide some protection for gamma radiation from ¹²⁵I.

Procedure-Specific Techniques
Radioactive implants will not be a contamination hazard unless a seed is accidentally severed. If the location of the implant is known and will not be disturbed during the autopsy, the decision whether to remove the sources will be based on expected external exposure to personnel. Removal of the sources may involve more radiation exposure than leaving them undisturbed and working quickly when near them. The table below shows unshielded and shielded (with body tissue) radiation exposure rates at chosen distances for implanted ¹²⁵I. The numbers represent possible hand exposures. Permanent implants of low-energy gamma emitters, for example, ¹²⁵I, do not normally present significant radiation hazards and therefore typically do not require removal for an autopsy to be performed (NCRP 1972).

If removal of sources or tissue containing the sources is deemed most practical, a radiograph of the area should be performed to show current location since the sources may have shifted since implant. After removal of the sources or tissue, a second radiograph or a survey with a portable radiation detection instrument will confirm removal of all sources. Source removal should be done rapidly and with long-handled instruments. If an entire organ or section of tissue can be removed with the sources intact, individuals performing the procedure would receive much less exposure. Laughlin, Vacirca, and Duplissey report that exposures to pathologists at an institution performing 16 procedures each year on cadavers with permanent implants remain below maximum permissible radiation limits for the general public (Laughlin et al. 1968).

If sources less than two years old (<2 y post-implant) are explanted, they should be placed together in a container and located in an area not frequented by personnel and not near areas where personnel may linger. Disposal of active sources should be by approved methods (U.S. NRC 1992, NCRP 1989). This can be accomplished by contacting and returning the sources to the institution where they were implanted, contacting a local institution licensed to receive and dispose of the radionuclide, or contacting the local regulatory radiation control department. If the sources are old (>2 y post-implant), they can be disposed with the tissue waste, presumably in a biohazard container.

Radioactive Tissues—Sectioning and Storage
Tissue removed from a radioactive cadaver may contain some of the radionuclide if it was not a seed implant. If the removed tissue was the location of a radionuclide implant, it likely will contain all of the radioactive material.

In the case of a radionuclide implant, only the tissue site of the implant will contain the radioactive material. Other tissues would contain no radiation and would have no handling restriction. If the implant site needed to be sectioned, removal of the implanted seeds from the tissue prior to sectioning is recommended even if it has been more than 10 half-lives of decay of the radionuclide since the implant date. Implanted seeds would likely be in a cadaver only if the individual had a permanent implant (for example, ¹²⁵I seeds for prostate cancer) and was released from the hospital.

If radioactive tissues will be stored, the type of container used for storage will depend on radioactivity levels in the tissue sample or organ. Most samples will be of little hazard although primary organs or primary organ tissue may need leaded containers available from a local radiation safety professional. Radioactivity will diminish with storage time, eventually eliminating the need for lead containers.

*tissue shielding assumes that the distance in column 1 is all body tissue 

References

• National Council on Radiation Protection and Measurements. Protection against radiation from brachytherapy sources. Bethesda, MD: NCRP; Report No. 40; 1972.
  
  
• Laughlin JS, Vacirca SJ, Duplissey JF. Exposure of embalmers and physicians by radioactive cadavers. Health Phys 15:451-455; 1968.
  
  
• U.S. Nuclear Regulatory Commission. Code of Federal Regulations, Title 10, Part 20. Washington, DC: U.S. Government Printing Office; 1992.
  
  
• National Council on Radiation Protection and Measurements. Radiation protection for medical and allied health personnel. Bethesda, MD: NCRP; Report No. 105; 1989.

Kelly Classic
Certified Medical Physicist