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Receiving, set-up, disposal of generator

Introduction

The methods to handle specific 99mTc generators, including elution instructions, will vary between different models and suppliers. Detailed handling information will usually be found in the package inserts that come with the generators. The procedures adopted during the set-up serve several important functions. These will include aspects of general safety and in particular radionuclide safety for the handlers as well as insuring that the quality of the product eluted from the generator is high and remains high during the full useful lifetime of the device. Generators retain residual radiation well past their useful lifetime and therefore a procedure for safe storage or return of the devices to the manufacturer should be in place.

99mTc generators are prepared under conditions that provide a sterile environment in the elution plumbing to allow direct use of the eluted activity in human studies. In addition to the sterile generator, packages may contain sodium chloride for elution of the 99mTc activity, sterile evacuated vials, sterile needles, elution vial shield, drug labels and package inserts. Each generator will be provided with an expiry date which will generally be 2 weeks or more from the time it was prepared. In practice the expiry is often dictated by the activity and the specific volume (activity/volume) that can be recovered from the generator after some time. The generator is designed to be operated and stored at normal room temperature (below 30°).

Issues of acceptance

Countries and regions will have their own specific guidelines related to handling of radioactive materials. Local regulations should be determined before working with these materials. According to the guidelines set by the Nuclear Regulatory Commission of the US:

Each receiver should monitor the radioactive contamination, radioactive levels and the integrity of the packaging. The monitoring should be done immediately upon the receipt of the package. If monitoring is required, it must be done within 3 hours if received during normal working hours, or within 18 hours if received after regular working hours.

For detail information about regulations for receiving and opening packages, please refer to the NRC website at: http://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1906.html

The radiopharmacies or facilities should have a designated area for accepting and delivering of radioactive materials. With radionuclide generators (99mTc generator) arrangement should be made between the delivering carriers and the receivers about the time and the number of generators that will be involved. The radiopharmaceutical supplier can only ship radioactive materials to licensed or authorized users with written documentation, which shows that those users are authorized to obtain the certain types and quantities of radioactive material requested.

Location

There should be a designated area for the receiving and delivery of radiopharmaceuticals; such area should only be used for radioactive substances. Upon receipt, packages of generators should be inspected for damage and leakage. They should be located in an isolated part of the workplace for survey of radiation levels and wipe test monitoring for external surface contamination before use.
Your local regulatory authorities set the limit for radiation levels present on the packages. A survey of each package with a survey meter is generally the first procedure.

Evaluation before use

Monitoring tests will generally include procedures to be performed on unopened packages:
  1. Measurement of the exposure rates on the package surface and at 3 feet from the package using a calibrated radiation monitoring device. This is done to detect if there is any radiation leakage or whether inadequate shielding is in place. Local acceptable radiation levels will be proscribed for these measurements.
  2. Performance of a wipe test on a substantial portion of the packaging surfaces for any removable contaminants. This is usually a very sensitive measure of radioactive contamination as the swipes can be counted in devices such as gamma counters that are able to detect even a few radioactive decays above background.
  3. If excessive radiation levels, surface contaminations, or shortages are noted, the final delivering carrier and your local regulatory authorities must be notified.

An example of a procedure for safely opening radioactive packages might be as outlined below. This procedure will be designed to minimize or prevent radioactive contamination and provide proper decontamination procedures should any radioactive leakage be present.


  1. Put on disposable gloves.
  2. Inspect for any visible evidence of damage to the packages.
  3. Once packages are monitored and surveyed, they can be opened. The quantities of radioactivity shown on the packing slip should match those received.
  4. Check the integrity of the final source container, looking for any sign of breakage, loss of liquid or discoloration of the liquid.
  5. Wipe the external surface of the final source container. Assay and decontaminate the surface if excessive removable contaminants are noted.
  6. Monitor the empty package and the materials with a Geiger-Műller survey instrument.
  7. Discard contaminated items as radioactive waste. Discard the non-radiation-contaminated items in regular trash after all the radiation labels are removed.
  8. Document the receipt of the package and subsequent inspection and tests. Record this information as well as lot numbers from the kit and pertechnetate, into the computer or logbook.
Verification of activity is often a required test for radionuclides that are shipped from suppliers and end up in the radiopharmacy. It will not be possible to take an external measurement that will verify that the generator contains the stated activity but the first elution of activity can be measured and used to confirm the activity of the generator.

Other Set-up issues
  1. Procedures vary widely but in many facilities the generators are placed behind additional shielding or in a dedicated shield built for the generator. This provides an added level of protection from the generator activity and the activity eluted from the generator.
  2. Generator designs include “wet” generators where there is a reservoir of sterile saline that remains attached to the inlet side of the generator. In the wet generator the pathway through the generator column remains filled with saline at all times after the first elution. “Dry” generators provide a vial of sterile saline for each elution and draw this volume through the column followed by some sterile air through a vent protected by a sterile filter. Thus although the surfaces remain dampened with saline they are regarded as dry. The dry generators will have a sterile needle onto which the saline vial is spiked. This will be protected by a needle guard.
  3. Once the issues discussed above have been addressed the generator is ready for the first and subsequent elutions. The process of elution is described in detail in Elution.

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Disposal

Manufacturers have return programs for used 99mTc generators. Often when the new generator is received, the old ones would be placed into the empty shipping box, sealed, surveyed and transported back to the manufacturers for credit. There are regulations that govern the whole process to make sure that the environment and personnel are protected from radiation exposure due to improper disposal. Requirements concerning recordkeeping about the type of waste materials to be disposed of, the total quantity, the way of disposal, the ultimate site of disposal etc. are to be followed.

Some radiopharmacies choose to let the generators decay to background levels of radioactivity, then the generators are surveyed, disassembled, and are disposed of in regular waste after all radiation labels are removed. After about10 half-lives of the parent (10 x 66 hours = 660 hours = 27.5 days) the activity of 99Mo in the generator will be 0.1% of its initial value. This still represents a fair amount of activity if we have started with a high activity generator but with patience and further decay the activity levels will become essentially background. At this point the generator can be disassembled and the column discarded as non-radioactive waste after monitoring. Local regulations will determine when materials are to be regarded as non-radioactive. This disposal option is complicated somewhat by the presence of traces of radionuclidic impurities in 99Mo that is obtained from fission of uranium. Some of these impurities will have considerably longer half-lives. These impurities are expected to be at very low concentrations but we must be aware of their presence and monitor columns carefully before disposal. The issue of impurities is addressed in Product issues with eluted 99mTc.

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