Personnel Radiation Monitoring Program for Medical Diagnostic Imaging
Measurement of radiation doses received by occupationally exposed persons is required by current radiation protection standards and applicable government regulations. Accurate and meaningful dose determinations are achieved only with the use of properly designed and utilized personnel monitoring devices. These devices must be properly managed by those persons responsible for the health and safety of the employees. Three major justifications exist for providing and properly managing these programs.
A. Employee Health
Accurate information on employee radiation doses is necessary to determine conformance with current radiation protection standards and also so that radiation doses may be maintained "As Low As Reasonably Achievable" (ALARA).
B. Regulatory Compliance
Most State and/or Federal regulations require that all individuals who are likely to exceed 10 percent of the applicable dose levels in the following table, be provided with properly managed personnel monitoring devices.
Groups of similar workers, (E.R., personnel, etc.) can be monitored for a reasonable period of time (i.e., one year). Spot checks would be performed for compliance with actual wearing of the dosimeters. If the resultant doses are mostly at the minimal level, a legal basis would be developed for removing the dosimeters from that group of workers. Alternately, an environmental dosimeter might be placed in a particular area for a prescribed period of time to determine exposure levels to a particular group of workers. However, some personnel by virtue of regulatory requirements or radioactive material license commitments must be provided with personnel dosimetry devices.
C. Legal Protection of Employer
In this era of increasing litigation, some facilities choose to provide dosimetry devices to all those workers who are expected to receive any significant exposure. There are many elements of a properly managed personnel dosimetry program and the benefits versus the cost and time should be evaluated.
Dosimeter Types
Any supplier of personnel dosimetry devices must be accredited by the National Voluntary Laboratory Accreditation Program (NVLAP).
Dosimetry devices come in various forms. The major sources of the actual dosimetry material are radiographic film, thermoluminescent material or other similar radiosensitive powders.
Additionally, there are whole body dosimeters and extremity dosimeters which are worn individually or in combination, depending upon the application.
Instructions to Workers
Once the determination has been made that the employee needs to be monitored, there are two very important things which must precede the actual monitoring.
Instructions concerning radiation exposure, risks, etc.
Acquisition of the employee's year-to-date exposure totals (required) as well as life-time totals (optional).
Nuclear Medicine Personnel Dosimetry
Occupational workers in the nuclear medicine department are divided into one of three groups, each having their specific personnel dosimetry monitoring needs and requirements.
Authorized Users- Some commitments made by a facility in their license application legally bind them to supply personnel dosimetry devices to all named Authorized Users on their license. If not, case by case studies can be made for each user taking into account their actual time and involvement in the nuclear medicine department. For small licensed programs with only a couple of Authorized Users, it is usually easier to have dosimetry available for each user.
Nuclear Medicine Technologist- License commitments may tie the facility to providing personnel dosimetry devices for the nuclear medicine technologist. In most cases, nuclear medicine technologist should be supplied, in any event, with a whole body personnel dosimetry device and extremity dosimetry device since they actually handle and inject radiopharmaceuticals. It is rare for an Authorized User to handle or inject radiopharmaceuticals so that extremity dosimetry devices are not normally indicated for them.
EKG Techs, Treadmill Techs, Radiology Nurses - A case-by-case study and evaluation is usually indicated for these individuals, but for small programs, it is advisable to usually monitor these individuals with personnel dosimetry device.
General Radiology Personnel Dosimetry
Most x-ray technologists by virtue of their work related duties may be likely to exceed 10 percent of the maximum permissible dose and are therefore monitored for radiation exposure. However, it should be noted that the average exposure for all medical workers in the United States is less than the threshold. For clinical staff performing tasks that do not require them to be near a patient undergoing common procedures (i.e., behind a shielded barrier), one personnel dosimeter worn on the trunk, as described above, is usually sufficient.
Ancillary Medical Personnel.
This group nurses providing care for diagnostic nuclear medicine patients on the floors as well as those providing care for therapeutic patients undergoing treatment with radiopharmaceuticals or sealed source radioactive seeds. It may also include personnel in the E.R., O.R., ICU, CCU, etc.
Nurses, who are providing care on the floor for patients who may have received diagnostic quantities of radiopharmaceuticals within the nuclear medicine department, do not normally need personnel monitoring devices. These patients have low radiation levels.Conversely, nurses providing care for therapeutic patients may need personnel dosimetry for two reasons.There may have been a commitment made in the radioactive material license stating that all nurses working with such patients will be provided personnel monitors.
Personnel within the E.R.. O.R., ICU, CCU, etc. would need to be evaluated on a case-by-case basis. It may be necessary to either badge personnel for a reasonable period of time, or to place some TLD environmental monitors in these areas to evaluate radiation levels present because of the use of portable x-ray units in these departments.
The Pregnant Occupational Worker
The pregnant occupational worker presents a particular challenge in the area of personnel monitoring. First of all, the worker is not considered pregnant, under current regulatory standards, until they provide the declaration of their pregnancy in writing to the employer along with providing the estimated date of conception. At this point, it is incumbent upon the employer to perform the following four functions: 1. Evaluate the potential for exposure of the fetus from the date of the written declaration back to the estimated date of conception. 2. Provide guidance on methods for reducing dose which may or may not include some work related restrictions on their daily duties. Particular attention should be paid for pregnant workers who are involved in therapeutic nuclear medicine studies or employees who are involved in cardiac cath work as primary personnel. 3. Provide additional monitors at the waist level which will be used to evaluate the fetal exposure. 4. Provide a termination report at the end of the pregnancy stating the legal limit as compared to the actual exposure received by the fetus.
It should be emphasized that under current regulatory standards, the worker must declare their pregnancy in writing until such time they are not to be considered as pregnant occupational workers. The legal limit for the gestational period is 500 millirem not to exceed a uniform exposure of 50 millirem per month. The reason for this exposure level is because the unborn child is considered to be a member of the general public. Therefore, the exposure is similar to the guidelines for those in the general public.
Management of Dosimeters and Reports
Each batch of dosimeters (whether they are film badges, extremity TLDs or some of the newer generation dosimeters) comes from the vendor with a control monitor. The purpose of this control monitor is to evaluate exposures to the individual dosimeters when they are not being worn by individuals, thus, it does not represent true radiation dose to the worker. For example, the control dosimeter will accompany the batch as it comes from the vendor and then as it is returned to the vendor. This control badge should be maintained in a non-radiation area (e.g., in the desk of a supervisor) away from any x-ray rooms or storage of radioactive material. This control badge will be stored with the individual monitors before they are exchanged and placed in individual holders.