You’ve never met ALARA, but she’s your best friend.
In the radiology world, ALARA stands for “as low as reasonably achievable.” The goal is to minimize radiation exposure by using any reasonable technique. Not only is it about protecting people (and patients), it is also a regulatory requirement at any veterinary practice in the nation.
There are four ways to decrease radiation exposure:
- Time Minimize. the time of exposure. Certainly, modern X-ray machines tend to make all the decisions these days, but it’s worth making sure that it is truly designed to minimize the time of exposure. The concept makes sense: The shorter the time of exposure, the smaller the radiation dose.
- Shielding. Leaded aprons, glasses, thyroid shields and gloves have only one purpose: to protect you and your team from X-rays. Interestingly, they’re not there for decoration purposes. It is important to remember that they do not protect from the primary beam, only scatter radiation.
- Distance. The farther a body part is from the source of radiation, the less the exposure. More specifically, if your free hand is twice as far from the source of X-rays, the radiation exposure decreases by a factor of 4. Even better, if the patient is sedated or anesthetized, try to avoid being in the X-ray room altogether. By using troughs, sand bags, tape, towels, special contraptions, a hint of common sense and a pinch of creativity, you can drastically reduce your radiation exposure.
- Amount. This is where common sense comes into play. By carefully planning each radiograph, we can reduce the number of exposures needed and, therefore, decrease the total quantity of radiation.
Another trick is to collimate to reduce the irradiated field. If you are taking a radiograph of the stifle, then only the stifle should be in the picture, to the exclusion of the hip, the tarsus, the abdomen and inches of empty space around the stifle. In addition, the primary beam should not exceed the size of the cassette.
These tips will decrease direct exposure, as well as scatter radiation. Think of scatter radiation as second-hand smoke. It doesn’t seem that bad, you can’t necessarily see it, it sounds futile to avoid it, but science tells us that is causes harm.
There are other reasons to collimate, besides personnel protection:
- It minimizes the amount of radiation to the patient.
- It provides better quality radiographs, better organ delineation and better contrast.
A storage rack hangs leaded gear neatly.
In the X-ray room, we hold these truths to be self-evident:
- No human body part should ever be in the primary beam—gloves or no gloves.
- Always wear your X-ray badge (aka dosimeter). It should be worn outside the lead apron. If you wear a ring badge, it should be worn on the hand that is closest to the radiation source.
What about those dosimetry reports that are sent monthly to your clinic?
In any given year, your total exposure should be less than 5,000 millirem (or 5 rem). Few people pay attention to these reports, yet our good friends at OSHA clearly state: “Employers shall maintain records of the radiation exposure of all employees for whom personnel monitoring is required (…) and advise each employee of his individual exposure at least yearly.”
How about pregnant staff members?
In any given month of pregnancy, the total exposure should be less than 55 millirem. The highest risk for a fetus is between months two and four. Regardless, any known pregnant employee should never be present while radiographs are being taken. In addition, pregnant employees have an obligation to notify their employers of their pregnancy.
How about clients who insist on holding their pets in the X-ray room?
This is one of the ultimate no-nos: Clients should simply never be allowed to restrain their pets in the X-ray room. You have too much at stake to gamble with this.
Hand exposed in the X-ray field (dog with hock subluxation).
How about team members who are not taking radiographs?
ALARA implies that only those who are taking radiographs should be present in the X-ray room. To prevent someone from accidentally walking in or walking by as you are taking an X-ray, simply close the door of the X-ray room. It’s a matter of respect.
I have heard (a few, so very few) technicians actually yell “SHOOTING!” a few seconds before they take an X-ray. The goal is to inform colleagues that X-rays are in progress and they shouldn’t walk in. But again, closing the door is ideal.
As a reminder, team members under 18 years of age (think externs, high school students and the neighbor’s son, the aspiring vet) are not allowed to be present during X-ray procedures.
Similarly, using leaded gear is just the beginning.
We also need to make sure it is effective. Aprons and gloves that are constantly mistreated or folded become less and less effective over time. It is well worth getting a storage rack to hang leaded gear neatly. It will help to take care of expensive equipment (your investment), and will help protect your team (and your liability).
Collimation reduces the irradiated field (Bichon with an ACL tear). Photos Courtesy of Dr. Phil Zeltzman
Why should we care about radiation exposure?
Because it causes ionization in our tissues.
This leads to the formation of free radicals, which can damage our DNA. When damaged DNA escapes the natural repair mechanisms, cancer and bone marrow suppression can develop. Genetic effects may lead to congenital defects in the employee’s children.
“Tumors include skin cancer (squamous cell carcinoma, basal cell tumors) and thyroid cancer if body parts are routinely exposed to the primary beam, as well as leukemias with chronic whole-body exposure,” explains Don Thrall, a board-certified radiologist and professor of radiology at North Carolina State University’s College of Veterinary Medicine.
One more reason to be mindful of radiation exposure we can control is that we are all exposed to sources we cannot do much about: inhalation of radon gas (the leading source of natural radiation exposure and the second leading cause of lung cancer), airplane flights, X-ray exposure (dental, CT scans, mammography), cosmic radiation (gamma rays) and more.
ALARA is a basic radiation safety principle. It is a mindset. It is also a regulatory requirement. Understanding, respecting and implementing ALARA principles should be part of the culture of any progressive veterinary hospital.