Tag: alara

21 Feb 2023
Medical CT or MRI or PET Scan Standing in the Modern Hospital Laboratory. Technologically Advanced and Functional Mediсal Equipment in a Clean White Room.
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4 Ways to Protect Healthcare Workers from Scatter Radiation

Patient safety is a major focus of radiation treatments and diagnostic imaging procedures. However, radiation workers in the healthcare field are also at risk for exposure to unsafe amounts of radiation—primarily scatter radiation—due to the nature of their work.

Protecting healthcare workers from scatter radiation is an important part of a successful radiation safety program. In today’s blog post, we discuss what scatter radiation is, effects on the human body, and four ways to help limit occupational exposures.

What is scatter radiation?

During typical diagnostic imaging procedures such as fluoroscopy, CT, or mammography exams, healthcare workers are exposed to scatter radiation.

X-ray machine for scatter radiation primary source example

Scatter radiation is a type of secondary radiation.1 It occurs when the primary beam from a source such as a CT Scanner, X-Ray, or Fluoroscopy unit interacts with matter. For scatter radiation, the “matter” that X-ray beams are most often interacting with is the patient in a procedure. As the primary beam intercepts the patient’s body tissues, some X-rays will bounce off those atoms to create secondary, specifically scatter, radiation.

Scatter radiation can be moderated through some machine positioning, like the C-Arm. The primary beam for a C-Arm is sent up through the table into a patient before being read by the other side of the machine. In this case, the back scattered radiation produced by the entrance beam below the table is mostly towards the floor and lower extremities of the radiation worker. Scatter coming out of the exit radiation from the patient is also present but reduced in intensity as compared with the entrance scatter below the table. Not all units are designed in this manner, however, and these scattered rays will be present in the imaging room until the diagnostic x-ray machine is turned off.2

What are the effects of scatter radiation on the human body?

Professionals performing diagnostic imaging procedures, such as radiologic technologists, are those most susceptible to scatter radiation emanating from a patient. Scatter radiation does not have as much energy as a primary X-ray beam does but over time it still can cause harm without technologists taking appropriate protective measures. This is a real risk for radiation workers, as they are potentially exposed to scatter radiation multiple times a day while running patients through their diagnostic imaging.

Without appropriate protection, radiation workers will begin to experience adverse health effects from prolonged scatter radiation exposure. This is because radiation has the potential to damage living tissue and organs.3 Severity of damage scope is dependent upon several factors:

  • the manner and length of time exposed
  • characteristics of the exposed person
  • the type of radiation
  • any involved radioactive isotopes
  • the sensitivity of affected tissue and/or organs

Since scatter radiation exposure is at lower energy and accumulated over longer periods of time (because technologists are performing X-ray procedures as a daily task), the risks of adverse effects are not as severe. However, radiation workers face an increased risk of cancer over a lifetime if protection is not made a priority in the workplace.4

Protection from your occupational exposure

Radiation worker protection should take as much priority as patient protection when it comes to radiation exposure. The ALARA principle is the standard for keeping radiation exposure “As Low As Reasonably Achievable”. As such, following these practices would be our top recommendation for limiting occupational exposure, with a couple additions. Here are the four ways to be best protected from scatter radiation:

Time

Limit the time that you spend near a radiation source while working. The more time that you are exposed to scatter radiation increases the possibility for a higher overall dose. If you must work near a source of radiation, work as quickly as possible and then leave the area to avoid spending more time around the source than necessary.

Distance

The second ALARA principle, distance, encourages distancing yourself from radiation sources. Radiation exposure decreases with distance, following an inverse square law for a point source. Doubling your distance will cause dose rate to go down by a factor of four. A “general rule of thumb” you can calculate is that any scatter radiation one meter from the side of the patient will be 0.1% of the primary x-ray beam intensity.5 This is helpful to keep in mind when considering how much distance you’re able to maintain during patient treatments.

Shielding

Shielding example for scatter radiation

Shielding is the well-known practice of placing a barrier between you and a radiation source for minimizing exposure. The material for these barriers normally depends on radiation source type. For any radiation, though, the shielding should be something that absorbs radiation such as lead, concrete, or water. The practice of shielding can also include personal protective equipment (PPE) directly worn by individuals, such as thyroid shields, radiation protection glasses, and lead vests. For scatter radiation, a combination of moveable shields either suspended from the ceiling or on rollers in addition to fixed table shields are ideal.6 In general, shields are placed close to the source as that allows for a greater solid angle to be covered.

Dosimetry Program

As medicine and medical technology advances, the use of radiation has become more ubiquitous; there is now a greater risk of ionizing radiation exposure for occupational workers. The need for effective radiation monitoring has become more crucial to account for these modern practices.

Radiation dosimeters worn on the body are able to provide a record of absorbed dose from ionizing radiation. Although the measurement of exposure so obtained is not direct protection, being able to track your absorbed dose is essential to the practice of radiation safety. Through regular dose readings, you can know if you’ve reached or are close to reaching the annual NRC occupational dose limits. In the long run, this is a great method for protection against scatter radiation; should you exceed dose limit, you can adjust your work for the rest of the year to avoid further exposure. Thanks to dosimetry programs, radiation workers can stay informed and avoid potential risks better than ever.

The Take-Away

Scatter radiation, even if not as potent as a primary radiation dose, can still have adverse effects over time. To avoid potential increases to your risk of cancer down the road, it’s essential to maintain protective habits when performing diagnostic imaging procedures. Following the ALARA principles and remembering the long-term value of a dosimetry program can keep exposure to scatter radiation and its negative health effects to a minimum.

Versant Physics’ dosimetry management services are available to help your company take that step further in scatter radiation protection. Learn more about our knowledgeable support team and the Instadose family of dosimeters today. For more information regarding shielding, scatter radiation, and applicable policies for a medical radiation safety officer, try our online MRSO or Medical X-Ray courses.

References

  1. What is primary radiation and secondary radiation? Reimagining Education. Published August 26, 2022. Accessed February 20, 2023. https://reimaginingeducation.org/what-is-primary-radiation-and-secondary-radiation/
  2. Lambert K. hps.org. Health Physics Society. Accessed February 20, 2023. https://hps.org/publicinformation/ate/q11396.html
  3. Radiation and health. Who.int. Accessed February 20, 2023. https://www.who.int/news-room/questions-and-answers/item/radiation-and-health
  4. Morgan WF, Sowa MB. Non-targeted effects induced by ionizing radiation: mechanisms and potential impact on radiation induced health effects. Cancer Lett. 2015;356(1):17-21. doi:10.1016/j.canlet.2013.09.009
  5. Lovins K. hps.org. Health Physics Society. Accessed February 20, 2023. https://hps.org/publicinformation/ate/q11780.html
  6. Klein LW. Proper Shielding Technique in Protecting Against Scatter Radiation. Vascular Disease Management. Published June 2021. Accessed February 20, 2023. https://www.hmpgloballearningnetwork.com/site/vdm/commentary/proper-shielding-technique-protecting-against-scatter-radiation

21 Apr 2021
ALARA, Health Effects, Ionizing Radiation, Radiation Safety Versant Physics 0 comment

Deterministic vs. Stochastic Effects: What Are the Differences?

Ionizing radiation is useful for diagnosing and treating a range of health conditions–broken bones, heart problems, and cancer, for example.  Medical imaging with x-rays, diagnostic radiopharmaceuticals, and radiation therapy are often life-saving procedures.

However, the accidental or misuse of medical radiation can sometimes cause unforeseen and unfortunate consequences.  Radiation protection guidelines and policies help to ensure the safe use of radiation in the medical setting for both patients and staff.

The health effects of ionizing radiation are usually classified into two categories: deterministic and stochastic.

Deterministic Effects


According to the International Atomic Energy Agency (IAEA), a health effect that requires a specific level of exposure to ionizing radiation before it can occur is called a deterministic effect. The severity of a deterministic effect increases as the dose of exposure increases and considers a minimum threshold, below which no detectable clinical effects occur. This type of effect is predictable and reproducible.  For example, localized doses to certain parts of the body at increasing levels will result in the same biological effects.

Deterministic effects are caused by severe cell damage or death. Individuals who experience the physical effects of this cell death do so when it is large enough to cause significant tissue or organ impairment.

Deterministic effects are short-term, adverse tissue reactions resulting from a dose that is significantly high enough to damage living tissues.  The severity of a deterministic effect increases with radiation dose above a threshold, below which the detectable tissue reactions are not observed. 

Deterministic effects are usually predictable and reproducible.  For example, localized doses to certain parts of the body at increasing levels will result in well-understood biological effects.

how to understand and communicate radiation risk diagram
Figure 1 Radiation – Deterministic and Stochastic Effects – Image Wisely, March 2017 “How to Understand and Communicate Radiation Risk”

Some examples of deterministic effects include:

  • Radiation-induced skin burns
  • Acute radiation syndrome
  • Radiation sickness
  • Cataracts
  • Sterility
  • Tumor Necrosis

Stochastic Effects


Stochastic effects are probabilistic effects that occur by chance.  An extremely rare stochastic effect is the development of cancer in an irradiated organ or tissue.  The probability of occurrence is typically proportional to the dose received. Stochastic effects after exposure to radiation occur many years later (the latent period).  The severity is independent of the dose originally received.

Since many agents in the environment are also known carcinogens, and since many cancers occur spontaneously, it is not possible in most cases to directly link radiation exposure to an observed cancer.  If a population group receives a dose of ionizing radiation at one time, it is therefore not possible to predict who in that group will develop cancer, if any, or to tell if the people who do develop cancer did so as a result of the dose of ionizing radiation or some other lifestyle factor, such as smoking.   

Examples of stochastic effects include:

  • Cancer
  • Heritable or genetic changes


Dose Limits and Radiation Protection


In our day-to-day lives, we are exposed to both background and man-made sources of radiation.  Everyone receives radiation exposure from natural cosmic and solar rays, and radionuclides in soil.  The benefits of diagnostic and therapeutic medical radiation far exceed the risks.  Fortunately, the health risks associated with natural background levels are small, and by regulations, we are protected from man-made radiation. 

The National Council on Radiation Protection and Measurements (NCRP) recommends dose limits for managing exposures to ionizing radiation and protecting humans from adverse effects.  Their purpose is to prevent acute and chronic radiation-induced tissue reactions (deterministic effects) and to reduce the probability of cancer (stochastic effect) while maintaining the benefits to people and society from activities that generate radiation exposures (NCRP Report No. 180, 2018).

Type of limit Radiation worker Public
Stochastic limits Effective dose, whole body (mSv/year) 50 1
Deterministic limits Tissue absorbed dose (mGy/year)
Lens of the eye 50 15
Skin 500 —
Extremities (hands and feet) 500 —

Figure 2.  Values from NCRP Report No. 180, Management of Exposure to Ionizing Radiation:  Radiation Protection Guidance for the United States (2018).

The concept of dose limits also takes into account the ideas that any use of radiation should do more good than harm, and that permissible exposure should be maintained “as low as reasonably achievable” (ALARA).   In line with this philosophy, medical professionals strive to minimize medical radiation exposures to patients without compromising imaging quality and therapy effectiveness. 

Conclusion


Adverse health effects can occur after exposure to ionizing radiation.  For radiation protection, scientific advisory organizations have recommended dose limits to prevent deterministic effects and reduce the probability of stochastic effects in radiation workers, medical professionals, patients, and other members of the general public. 

Versant Physics is a full-service medical physics and radiation safety consulting company based in Kalamazoo, MI. Contact us for all of your regulatory, radiation safety, and personnel dosimetry needs.

Sources:

  1. https://hps.org/publicinformation/ate/faqs/regdoselimits.html
  2. https://www.nrc.gov/reading-rm/basic-ref/glossary/non-stochastic-effect.html
  3. https://www.nrc.gov/about-nrc/radiation/around-us/uses-radiation.html
  4. https://www.radioactivity.eu.com/site/pages/Deterministic_Effects.htm
  5. https://www.imagewisely.org/Imaging-Modalities/Computed-Tomography/How-to-Understand-and-Communicate-Radiation-Risk
  6. https://www.radiation-dosimetry.org/what-is-dose-limit-radiation-definition/

08 Apr 2021
Radiation Worker Behind Shielding
ALARA, Radiation Safety, Radiation Safety Officer, Regulatory Versant Physics 0 comment

ALARA: The Gold Standard of Radiation Protection

The ALARA principle is a relatively simple safety protocol designed to limit ionizing radiation exposure to workers from external sources.

This principle was established by the National Council on Radiation Protection and Measurements (NCRP) in 1954 in response to the atomic bombings of Hiroshima and Nagasaki and the increased interest in nuclear energy and weaponry post-WWII. The philosophy has been refined over the years by different regulatory agencies such as the Atomic Energy Commission (AEC) and Nuclear Regulatory Commission (NRC) as more knowledge about radiation and its effects on living tissue has come to light. In its current form, ALARA stands for “as low as reasonably achievable” and is considered the gold standard for radiation protection.

ALARA is based on the idea that any amount of radiation exposure, big or small, can increase negative health effects, such as cancer, for an individual. It is also based on the principle that the probability of occurrence of negative effects of exposure increases with cumulative lifetime dose. As such, the ALARA principle is considered a regulatory requirement for all radiation programs licensed with the NRC and any activity that involves the use of radiation or radioactive materials.

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To successfully implement ALARA principles in your radiation safety program, “it is important that every reasonable effort be made to maintain exposures to radiation as far below the dose limits in this part as is practical consistent with the purpose for which the licensed activity is undertaken, taking into account the state of technology, the economics of improvements in relation to state of technology, the economics of improvements in relation to benefits to the public health and safety, and other societal and socioeconomic considerations, and in relation to utilization of nuclear energy and licensed materials in the public interest.” (10 CFR 20.1003)

Time, Distance, and Shielding


There are three factors to the ALARA philosophy which, when executed correctly, can reduce and even prevent unnecessary exposure: time, distance, and shielding.

Time

Limit the amount of time spent near a radiation source. If you must work near a radioactive source, you should work as quickly as possible and then leave the area to avoid spending more time around the source than necessary.

Distance

Increase the distance between yourself and a radiation dose. The farther away you are, the lower the dose you will receive. In many cases, the dose rate decreases as the inverse square of the distance – when the distance is doubled, the dose rate goes down by a factor of four.

Shielding

Put a barrier between you and the radiation source. The type of barrier will depend on what kind of radiation source is being emitted but should be made of a material that absorbs radiation such as lead, concrete, or water. This can also include PPE such as thyroid shields and lead vests.

medical professionals implementing time, distance, and shielding principles

Conclusion


The ALARA principle has successfully limited exposures to workers—and patients undergoing medical procedures involving radiation—for several decades. Adhering to this principle as well as your state’s radiation safety regulations will result in keeping workers healthy and protected.

Visit our website for more information on how Versant Physics’ board-certified health physicists, medical physicists, and radiation safety officers can help you implement safe practices in your radiation safety program.

Sources

  1. https://nucleus.iaea.org/sites/orpnet/resources/frquentlyaskedquestions/Shared%20Documents/faq-list-en.pdf
  2. https://hps.org/publicinformation/ate/q8375.html
  3. https://www.cdc.gov/nceh/radiation/alara.html#shielding
  4. https://www.nrc.gov/reading-rm/basic-ref/glossary/alara.html
  5. http://large.stanford.edu/courses/2015/ph241/baumer2/

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