Radiation Monitoring Chapter 5: Personnel Monitoring

Radiation Monitoring

• Personnel monitoring is required to ensure that occupational radiation exposure levels are kept well below annual effective dose (EfD) limits.
• It involves monitoring equivalent dose to any person occupationally exposed to ionizing radiation on a regular basis.

Personnel Monitoring Devices

• Required whenever radiation workers are likely to receive 10% or more of the annual occupational EfD limit of 50 mSv (5 rem) in any single year.
• The primary purpose of a personnel dosimeter is to provide an indication of the working habits and working conditions of diagnostic imaging personnel.
• It determines occupational exposure by detecting and measuring the quantity of ionizing radiation.

Placement of Personnel Dosimeter

• When a protective apron is not being worn, the primary personnel dosimeter should be attached to the clothing on the front of the body at collar level.
• When a protective apron is used, the dosimeter should be worn outside the apron at collar level on the anterior surface of the body.

Personnel Monitoring Devices Currently Available

• Nuc Med

Extremity Dosimeter

• A thermoluminescent dosimeter (TLD) ring badge is worn as a second monitor when performing radiographic procedures that require the hands to be near the primary x-ray beam.
• The purpose of the extremity dosimeter is to measure radiation exposure to the hands.

Record of Radiation Exposure

• The record of radiation exposure should be part of the employment record of all radiation workers.
• Values represent the average annual EfD to the whole body.

Characteristics of Personnel Dosimeters

• Personnel dosimeters are lightweight and easy to carry.
• They are made of materials durable enough to tolerate normal daily use.
• They can detect and record both small and large exposures in a consistent and reliable manner.
• Outside influences should not affect the performance of the instrument.
• They should be reasonably inexpensive to purchase and maintain.

Types of Personnel Dosimeters

• Optically Stimulated Luminescence Dosimeter (OSL)
• Direct Ion Storage (DIS)

Optically Stimulated Luminescence Dosimeter (OSL)

• The most common type of device used for monitoring of occupational exposure in diagnostic imaging and radiation therapy.
• Contains an aluminum oxide detector that glows when stimulated by light.
• Energy discrimination: filters made of aluminum, tin, and copper.
• Sensitivity: accurate reading as low as 10µSv.
• Control monitor: there is a permanent record.

Advantages and Disadvantages of OSL

• Advantages: lightweight, durable, easily worn, preloaded packet, allows for reanalysis.
• Disadvantages: occupational exposure is recorded only in the body area where the device is attached, exposure cannot be immediately determined.

Direct Ion Storage Dosimeters

• Small ionization gas-filled dosimeter connected to a solid-state device with electrically erasable programmable read-only memory (EEPROM, or E2PROMs).
• Radiation ionizes the gas in the chamber, and the electric charge will “read out” by introducing a signal.
• Read out through a physical connecting device.
• Advantages: instant access to data, lightweight and durable.
• Disadvantages: must be worn to be accurate.

Radiation Survey Instruments for Area Monitoring

• Three categories: those without a readout scale, those with a readout scale, and ionization-chamber based.
• Most common have a Geiger-Műller tube as their detector.
• The simplest form indicates presence of radiation above background level.
• Do not provide a cumulative exposure reading.

Types of Instruments

• Instruments respond to the charged particles that are produced by the radiation interacting with and ionizing the gas in the detector.
• Measure either the quantity of electrical charge resulting from the ionization of gas or the rate at which the electrical charge is produced.

Requirements for Radiation Survey Instruments

• Portable
• Durable
• Reliable
• Interacts with radiation as tissue does
• Detects all common types of ionizing radiation
• Energy of the radiation should not affect the response of the detector
• Cost-effective
• Calibrated annually to ensure accurate operation.

Gas-Filled Radiation Survey Instruments

• Ionization chamber-type survey meter (cutie pie)
• Proportional counter
• Geiger-Műller survey meter

Instruments Used to Measure X-ray Exposure in Radiology

• Ionization chambers can be used to measure the radiation output from both radiographic and fluoroscopic x-ray equipment.
• A “cutie pie” ionization chamber is also used for radiation protection surveys.
• Both the ionization chamber and the electrometer system must be calibrated periodically to meet state and federal requirements for patient dose evaluation.

Radiation Monitoring

• Personnel monitoring is required to ensure that occupational radiation exposure levels are kept well below annual effective dose (EfD) limits.
• The maximum permissible dose (MPD) was replaced by the effective dose (EfD) in 1991.

Personnel Monitoring

• Personnel dosimetry is the monitoring of equivalent dose to any person occupationally exposed to ionizing radiation.
• The purpose of personnel dosimetry is to create awareness of various radiation exposure monitoring devices and their functions.
• It is required whenever radiation workers are likely to receive 10% or more of the annual occupational EfD limit of 50 mSv (5 rem) in any single year.
• Dosimetry devices are issued when personnel could receive approximately 1% of their annual occupational EfD limit in any month, or approximately 0.05 mSv (50 mrem).

Purpose of Personnel Dosimeter

• Provides an indication of the working habits and working conditions of diagnostic imaging personnel.
• Determines occupational exposure by detecting and measuring the quantity of ionizing radiation.

Placement of Personnel Dosimeter

• During routine computed radiography, digital radiography, or conventional radiographic procedures.
• When a protective apron is not being worn, the primary personnel dosimeter should be attached to the clothing on the front of the body at collar level.
• When a protective apron is used, the dosimeter should be worn outside the apron at collar level on the anterior surface of the body.

Personnel Monitoring Devices Currently Available

• Nuclear medicine (Nuc Med) personnel dosimeters are available.

Placement of Personnel Dosimeter as a Second Monitor

• When a protective apron is worn, the first or primary dosimeter is worn outside the protective apparel at collar level.
• The second dosimeter should be worn beneath a wraparound-style lead apron at waist level.

Placement of a Personnel Dosimeter as a Monitor for the Embryo-Fetus

• For pregnant diagnostic imaging personnel, the primary dosimeter is worn at collar level.
• The second monitoring device is worn at abdominal level.

Extremity Dosimeter

• A thermoluminescent dosimeter (TLD) ring badge is worn as a second monitor when performing radiographic procedures that require the hands to be near the primary x-ray beam.
• The purpose of the extremity dosimeter is to detect and measure radiation exposure to the hands.

Record of Radiation Exposure

• Should be part of the employment record of all radiation workers.
• Values represent the average annual EfD to the whole body.

Characteristics of Personnel Dosimeters

• Lightweight and easy to carry.
• Made of materials durable enough to tolerate normal daily use.
• Able to detect and record both small and large exposures in a consistent and reliable manner.
• Outside influences should not affect the performance of the instrument.
• Should be reasonably inexpensive to purchase and maintain.

Types of Personnel Dosimeters

• Optically Stimulated Luminescence Dosimeter (OSL).
• Direct Ion Storage (DIS) dosimeter.

Optically Stimulated Luminescence Dosimeter (OSL)

• Most common type of device used for monitoring of occupational exposure in diagnostic imaging and radiation therapy.
• Contains an aluminum oxide detector.
• Energy discrimination: filters made of aluminum, tin, and copper.
• Sensitivity: accurate reading as low as 10µSv.
• Control monitor: provides a permanent record.

Advantages of Optically Stimulated Luminescence Dosimeter (OSL)

• Lightweight, durable, and easily worn.
• Preloaded packet.
• Allows for reanalysis.

Disadvantages of Optically Stimulated Luminescence Dosimeter (OSL)

• Occupational exposure is recorded only in the body area where the device is attached.
• Exposure cannot be immediately determined.

Radiation Survey Instruments for Area Monitoring

• Three categories: those without a readout scale, those with a readout scale, and ionization-chamber based.
• Most common have a Geiger-Műller tube as their detector.
• Simplest form indicates presence of radiation above background level.
• Do not provide a cumulative exposure reading.

Types of Instruments

• Instruments respond to the charged particles produced by the radiation interacting with and ionizing the gas in the detector.
• Measure either the quantity of electrical charge resulting from the ionization of gas or the rate at which the electrical charge is produced.

Gas-Filled Radiation Survey Instruments

• Ionization chamber-type survey meter (cutie pie).
• Proportional counter.
• Geiger-Műller survey meter.

Requirements for Radiation Survey Instruments

• Portable.
• Durable.
• Reliable.
• Interacts with radiation as tissue does.
• Detects all common types of ionizing radiation.
• Energy of the radiation should not affect the response of the detector.
• Cost-effective.
• Calibrated annually to ensure accurate operation.

Gas-Filled Radiation Survey Instruments

• Ionization chamber-type survey meter (cutie pie): sensitivity ranges and uses, advantages and disadvantages.
• Proportional counter.
• Geiger-Műller survey meter: sensitivity and use, components, disadvantages.

Instruments Used to Measure X-ray Exposure in Radiology

• Ionization chambers can be used to measure the radiation output from both radiographic and fluoroscopic x-ray equipment.
• A “cutie pie” ionization chamber is also used for radiation protection surveys.
• Both the ionization chamber and the electrometer system must be calibrated periodically to meet state and federal requirements for patient dose evaluation.

Medical Physicists' Use of Instruments

• Medical physicists use ionization chambers connected to electrometers to perform standard measurements required by state, federal, and health accreditation organizations for radiographic and fluoroscopic devices.

This quiz covers the basics of radiation monitoring, including the requirement for personnel monitoring and personnel dosimetry. It also discusses the maximum permissible dose and its replacement with EFD in 1991.