Month: April 2022

28 Apr 2022
Radiation Protection Survey of Package with Pancake Probe

A Beginner’s Guide to Radiation Protection Surveys

The purpose of a radiation protection survey is to identify higher-than-normal doses of radiation in medical environments, labs, and anywhere radiation-emitting machines or radioactive materials (RAM) are used. They are required by state and federal regulations to be performed regularly to ensure the safety of technicians, technologists, nurses, doctors, researchers, and patients.

In this brief guide we’ll talk about what a radiation protection survey is, why it is important, and the type of equipment required to perform a radiation protection survey.

What is a radiation protection survey?

Radiation protection surveys are a way to directly measure radiation levels and identify potential leakage through breaks or voids in shielding.

Surveys are performed on:

  • Diagnostic fluoroscopic and radiographic equipment
  • Non-medical industrial equipment such as those found in veterinary offices
  • CT and CBCT machines
  • Particle accelerators
  • Irradiators
  • Bone mineral densitometers
  • Cabinet x-ray machines
  • Areas that use sealed sources of RAM
  • Packages containing RAM

The Different Types of Radiation Surveys

Not all radiation surveys are created equal. Let’s talk about some of the different surveys you may encounter a need for in your radiation safety program.

Radiation Emitting Device Survey

X-ray machines and other radiation-emitting devices require regular surveys to be performed to confirm that the machine is operating as expected. Radiation producing machines are surveyed for:

  • Timer accuracy
  • Radiation output
  • Focal spot size
  • kVp and mA
  • Beam limitation accuracy
  • Filtration
  • Skin entrance exposure / rate of exposure
  • Scatter radiation measurements
  • Photo-timer operation
  • Proper signage, labels, and postings

If high or unexpected dose rates are measured during a survey, the machine should be turned off and undergo appropriate maintenance.

Area Survey

Area surveys are required anywhere a radiation device is in use and the potential for receiving a higher-than-normal radiation dose is present. These surveys are typically measured in milliRoentgen per hour (mR/hr). The Roentgen is a measure of the amount of ionization in the air from the radiation.

Anytime you have an area survey performed, you are required to keep the official records of the survey results for 3 years.

Contamination Wipe Test

A contamination wipe test, also known as an indirect or swipe survey, is used to identify radioactive material contamination on surfaces, equipment, and clothing such as those found in a lab. This type of survey can identify non-fixed radiation left behind from radioactive solids, liquids, or gasses.

Lab tech performing a wipe test

Wipe tests are recommended to be performed frequently, especially if you are a HAZMAT employee that receives or ships RAM packages. A wipe test involves wiping at least 300cm2 of the package’s surfaces using an absorbent material. Afterward, the activity on the swipe is measured assuming a removal efficiency of 0.1 unless the actual efficiency is known.

Users in lab settings typically survey their work areas after an experiment or when a minor spill is suspected.

Radioactive Sealed Source

A radioactive sealed source is a source of special form RAM that has been contained or encapsulated to prevent contamination. These sources can only be opened by destruction. Semi-annual surveys of these sources are required to check for leakage.

Bioassay Survey

Internal exposure monitoring, or a bioassay survey, is performed on individuals that use unsealed radioactive materials. The survey estimates the internal organ dose to determine if any RAM has entered the body. It can also help determine if RAM is present in the air.

Bioassay surveys are performed by analyzing blood, tissue, or urine samples or by carefully monitoring the presence and/or quality of isotopes present in the organ of concern.

How often do I need to have a survey performed?

The frequency of a radiation protection survey depends on several factors, most of which depend on different state and federal regulations.

  • When a new or used x-ray equipment is installed
  • When existing x-ray equipment has been moved
  • If shielding has been modified
  • After the equipment has undergone significant repairs
  • If a potential problem is indicated

Who performs these surveys?

In general, surveys on radiation-producing equipment are conducted by health physicists and medical physicists.

Is special equipment required for a survey?

Special equipment is required to detect ionizing radiation. Most equipment is hand-held measurement instruments called survey meters. This equipment is required to be calibrated annually to maintain accuracy and to ensure that reliable measurements are recorded.

Survey meters consist of:

  • A probe which produces electrical signals when it is exposed to radiation
  • A control panel readout with an electronic meter that gauges the amount of radiation exposure
  • A speaker which provides an audible indication of the radiation exposure

There are several different kinds of survey meters physicists use to perform radiation surveys.

Geiger-Mueller Pancake Probe

One of the more commonly used survey meters is the Geiger-Mueller Pancake Detector. Although there is no “universal” radiation detector, the G-M Pancake Probe comes pretty close. This is because the probe can detect alpha, beta, and gamma radiation, although they are generally used for detecting Beta Emitters. These probes come in a variety of models and configurations.

Surveying open package with pancake probe

The probe detects radiation by collecting counting gas within the tube. The counting gas is ionized when a photon or particle interacts with a released electron. When the voltage is high, radiation that interacts with the counting gas produces an electronic pulse that is measured with a separate counting instrument.

A pancake probe has a thin layer of mica on the active face of the detector, which allows most alpha and beta particles to interact with the counting gas inside the tube.

G-M Pancake Probes are frequently used to detect C-14, Ca-45, P-32, P-33, and S-35.

Scintillation Survey Meter

A scintillation survey meter is used to detect low-energy Gamma Emitters and x-rays. The scintillator, or sensor, is made of a transparent crystal or liquid which shines when it interacts with ionizing radiation. The scintillator is attached to a photosensor like a photomultiplier tube which detects the generated light.

This survey meter detects I-125 and Cr-51. They are an ideal equipment choice for surveying electron microscopes and x-ray diffractometers.

Diagnostic Physics Support and Radiation Surveys by Versant Physics

When it comes to hiring a consultant to perform radiation protection or QA surveys for your equipment, you want to make sure you’re working with the best. People who are experts in state and federal regulations regarding radiation machines and RAM, have access to top-of-the-line survey equipment and understand the importance of adhering to ALARA standards.

Versant Physics’ proactive and transparent diagnostic physics support process minimizes safety concerns and reduces the likelihood of compliance violations. We support our clients by sharing our knowledge of best practices in advanced technologies, and by utilizing a team-based approach we feel enables our clients to focus on maximizing the quality of patient care.

Contact our team for a free 30-minute consultation to learn more about our diagnostic physics and radiation survey expertise.


20 Apr 2022
nurse guiding patient entering mri scanner

The Basics of Radiation Shielding in Medicine

Basic radiation protection guidelines can be summed up in three simple concepts: time, distance, and shielding. While both limiting the time spent and increasing the proximity to an ionizing radiation source is something that lies within the power of the individual, shielding and X-ray room design require careful planning and execution by the facility or Radiation Safety Officer.

What is radiation shielding?

Radiation shielding is simply a barrier placed between a source of radiation and the area or person that needs to be protected. The purpose of radiation shielding is to limit, control, or modify the radiation exposure rate at a set point.

Shielding is based on attenuation or the gradual reduction in the intensity of energy through a specific medium. X-ray radiation that passes through certain materials decrease and are absorbed, thereby reducing the exposure to the other side of the barrier.

Without shielding, the public, radiation workers (including dentists and veterinarians), and even nearby office workers could be exposed to levels of radiation outside regulated exposure limits, which can potentially lead to negative health effects. Although it is impossible to completely avoid exposure to radiation, shielding is a critical consideration in any medical facility that greatly reduces unnecessary exposure.

Shielding Materials

There are several different materials that provide protection from penetrating radiation. Concrete, water, special plastic shields, air stops, and lead are all barriers that stop different types of rays and particles, reducing the overall dose a person receives.

In medical environments, the most common shielding materials used include lead, lead-free shielding, and lead composites.

Lead

Lead is one of the most used and most effective shielding materials. It is a highly dense material with a high atomic number and a high number of electrons which make it ideal for shielding in most medical radiation environments. This is because the type and energy of radiation in a medical environment that passes through lead are absorbed or scattered by the electrons present in the material.

Vet team wearing shielding garments during exam

Lead is also cheap and easy to process. It can be mixed with other materials like glass, or binders like vinyl, which allows it to be used as construction materials in X-ray rooms or worn as shielding garments.

Lead-Free Shielding

Technological advances have allowed for the creation of non-toxic, lead-free shielding materials as well. Other attenuating materials such as antimony (Sb), tungsten (W), and tin (Sn) are used in place of lead and combined with additives and binders to create wearable protective garments or materials. They offer equal protection from scatter radiation.

Lead-free shielding has several benefits, including being both recyclable and non-toxic. Lead-free shielding materials can also be lighter which makes them easier for personnel to wear during longer procedures.  

Lead Composite

Lead composite shielding is a long-lasting mixture of lead and lighter materials that attenuate radiation just as successfully as traditional lead shielding barriers.

Because of lead’s weight, it can be cumbersome to use and wear for long periods of time, limiting the efficacy of a radiation worker. Lead composites solve this problem. They are made with blends of tin, vinyl, and rubber and create a shielding barrier that can be up to 25% lighter than traditional shielding without sacrificing their ability to block penetrating radiation.

Shielding and Scatter Radiation

In some diagnostic X-ray procedures, medical personnel such as operators, radiologists, and technologists are required to remain in the room with the patient. This proximity frequently exposes them to something called scatter radiation or radiation that bounces off a patient’s body during a procedure.

To limit this exposure, some medical personnel are required to wear frontal or full wrap-around style lead aprons, thyroid shields, and lead glasses/gloves. These protective garments can attenuate roughly 93% of photons at typically scattered energies.

Lead apron and thyroid collar on hangar

Shielding Products and Design

There are several different ways radiation shielding can be applied or designed to protect healthcare workers.

Room Shielding

Shielding may be required in the floor, ceiling, doors, or any wall of any X-ray or radioactive material use room.  Shielding is used to protect workers, patients, or the public that may be in the adjacent areas/rooms.

During a room’s construction, special shielding materials are installed where their need has been determined. These materials can include lead-lined windows and doors, lead-lined drywall or plywood, lead sheets for floors and ceilings, pipe shielding, and more.

X-ray room shielding requirements vary from state to state. It is important to consult with a qualified expert familiar with these regulations as well as work with an architect experienced in constructing X-ray suites before building a new room.

Leaded Glass and Curtains

In some cases, it isn’t possible for a facility to build shielding into the physical structure of a building.

Leaded glass barriers are a barrier used by techs and doctors which allow them to safely view a patient during an imaging procedure. This type of glass is ideal for radiation-producing equipment in the 80-300 kV range thanks to its high lead content.

Lead curtains are also used to shield radiation workers, particularly in large animal hospitals or operating rooms. These curtains are leaded rubber or vinyl sheets that are ideal for protection against low-level or secondary radiation. They make for room-saving partitions that can be open or closed as needed and typically offer protection from 0.5mm to 2.00mm lead equivalency.

Mobile Shielding Barriers

In some cases, additional barriers are needed to protect doctors and techs during radiology, nuclear medicine, cath lab, or diagnostic imaging procedure. These barriers are lead-lined partitions on wheels, often with a protected window to allow for patient observation.

Mobile radiation barriers come in a variety of shapes, sizes, and lead equivalencies. They are ideal for maintaining flexibility and ease of movement in a procedure room while successfully minimizing the scattered radiation dose to workers in the room.

Versant Physics Shielding Services

Understanding the detailed shielding requirements for your state or facility can be a time-consuming challenge. If executed incorrectly, there can be serious consequences to the health and safety of radiation workers, patients, and building staff as well as potential regulatory compliance fines.

That’s why it is important to have a radiation safety consultant like Versant Physics on your side. Whether you’re constructing a new X-ray room, remodeling or repairing an existing shielding setup, or looking to upgrade your current shielding equipment, our team of expert health and medical physicists can assist.

We provide radiation shielding calculations, evaluation, and design for facilities of all kinds, including hospitals, clinics, dentist offices, chiropractor offices, and veterinary clinics. Our range of expertise includes:

  • Radiography
  • Fluoroscopy
  • Computed Tomography (CT)
  • Nuclear Medicine/PET
  • Mammography
  • Dental/Veterinary X-ray

Not sure what materials or type of shielding is right for your facility? Contact our regulatory experts for a free 30-minute consultation.