Radiation Safety Guidelines
Radiation safety is a very important part of our day to day operations at the VSCAN. Though potentially harmful if used incorrectly and often misunderstood, ionizing radiation provides us with an incredible tool for performing Diagnostic Radiography (x-ray), and Computed Tomography scanning (CT). Check out our diagnostic imaging page if you are interested in learning more about these modalities. For the purposes of this article we will just be focusing on what it takes to have a high level of radiation safety in a veterinary practice. We've also distilled this down into a sign that you can download at the bottom of this page and hang in your clinic.
Time, Distance, and Shielding. These are the three main concepts of radiation protection. Time in this case refers to the exposure time or how long the equipment is producing radiation. Distance is very important because the further away from the source you are the less scatter radiation you will be exposed to. Also in terms of the procedure; utilizing an optimal source to image distance, source to object distance, and object to image distance will reduce not only the amount of scatter radiation that is produced but will reduce the amount of radiation necessary for the exposure thus reducing the exposure to the patient. Shielding, as we will discuss further in a second, refers to the minimum acceptable amount of lead or lead equivalent included in the room construction, but personal radiation protection equipment such as lead aprons and shields.
The first step in radiation protection is the room construction. I'm not going to go into all of the lead or lead equivalent requirements for the walls, doors, and windows because it varies based on the laws and governing bodies of your area. Just know that it's important and that radiation equipment shouldn't be used unless in an approved space. Each room should have doors that close or a "maze" type entrance. Lastly, every room should have a lighted sign on the outside indicating that the x-ray equipment is in use. This light can be connected to the exposure button or manually turned on before the exposure.
Any time you are in the room during a radiographic procedure you must wear a proper lead apron as well as a thyroid shield. If your hands need to be close to the field of view to hold a patient you should also wear lead gloves to protect your hands from unnecessary exposure. Even in lead gloves your hands should never enter the field of view. Gloves are designed to protect against scatter radiation and not direct exposure of the x-ray beam. There are many other forms of standing shields that can be utilized providing they are used appropriately. Never turn your back towards the x-ray source during an exposure. If the lead apron is covering the front of your body then you need to face the radiation source in order for it to be effective. There are some forms of lead aprons that wrap entirely around your body to protect you from all sides though they are much more expensive and twice as heavy. Lead aprons are very delicate and must be hung properly when not in use in order to prevent weak spots or cracks in the lead. All lead aprons and shields should be radiographed routinely to check for cracks. If you see a crack on the image then the shield should be removed from use immediately until it can be repaired or replaced.
Radiation exposure monitoring is called dosimetry and is utilized to monitor personnel exposure as well as highlight malfunctioning equipment or radiation leaks. If you are working around ionizing radiation you must be provided with at least one "whole body" dosimetry badge. These badges are assigned to each employee and worn during every procedure. After a set period of time the badges are sent back to a company where the cumulative exposure is read and reported. Though radiation protection is not governed as well in veterinary medicine as in human medicine, it is still important to monitor personnel exposure and maintain an annual effective radiation dose less than 15 mSv (milli sievert), or 1.5 rem (radiation equivalent man). Dosimeter badges must always be worn outside of the lead apron, clipped to the bottom of the thyroid shield or apron pocket, and faced forward. Otherwise it will not provide an accurate reading of your cumulative exposure. There should be a set location for storage of dosimeter badges outside of the x-ray room with a "control" badge provided by the dosimetry company.
If you are pregnant or become pregnant, it is your choice and responsibility to notify your employer and consider removing yourself from the radiation areas in the clinic. After notifying your employer it is their responsibility to provide you with a second dosimeter if you are to continue working in the x-ray environment. This fetal dosimeter must be worn clipped to your waistband and underneath the lead apron to provide the most accurate fetal exposure reading.
Improper techniques and repeat radiographs are the two main causes of unnecessary radiation exposure. To reduce the need for repeat radiographs make sure that your patient is going to cooperate with the test. If they are nervous or "uncooperative" it may be necessary to use medications to sedate or anesthetize the patient. Utilizing positioning aids such as cushions, troughs, sandbags, or restraints will help to ensure that the patient remains in the proper position for the exposure and allow you to stay as far from the radiation source as is safe and reasonable. It should be obvious but I'll say it just to keep from getting in trouble, NEVER LEAVE A PATIENT UNSECURED OR UNATTENDED ON THE X-RAY TABLE!
Proper technique is summed up by the ALARA concept or the idea of keeping the exposures "as low as reasonably achievable". Overexposure and underexposure can necessitate a repeat of a radiograph so it is important to set the technique correctly for your patient and procedure. Every radiography suite should have a technique chart designed specifically for that piece of equipment. If you don't have one get one. To use the technique chart first measure the body part being radiographed as the radiation will be passing through it. Correlate that measurement with the technique chart and find the appropriate kVp (kilovolt power), mA (milliamps) , and S (time in seconds); or kVp and mAs (milliampere seconds).
Collimation is the use of adjustable lead plates in the x-ray tube housing which restrict the x-ray beam and thus the size of the field of view (exposure area). Collimating as small as possible to the area of interest will reduce the exposure to the patient as well as reduce the production of scatter radiation that can expose personnel or overexpose the image.
Another reason for repeat radiographs is poor timing. Not the exposure time but if you are performing radiographs of the thorax it is important to create the exposure during peak inspiration. And not like your waiting for your radiographic muse to artistically inspire you but at the moment the patient has taken a breath in and the lungs are fully expanded. The x-ray system is equipped with a two stage exposure button or pedal to help with this. Pressing the first stage warms the tube and prepares it for exposure at the exact moment the second stage is engaged. Learning the exposure timing of your system is very important in catching the patient at peak inspiration.
The last part of radiation safety is taking care of the equipment. Preventative maintenance and quality assurance testing should be performed regularly in order to keep the equipment functioning properly. These checks and tests will also allow you to catch any potential issues early which is great if the equipment will need repairs requiring downtime. Make sure you respect the equipment and clean it after every use to keep dust, dirt, and hair from collecting in the system. Always make sure to report broken equipment immediately to your radiation safety officer or the person in charge of maintaining and repairing the equipment.
Making each of these tips a part of your routine will ensure the highest level of safety for you, your co-workers, and your patients.