How to decrease or eliminate radiation exposure in medical imaging

As a radiologist we have a guiding principle that is almost a mantra, an amendment to the Hippocratic oath, ALARA. Radiologists are trained to keep radiation exposure As Low As Reasonably Achievable (ALARA). To achieve ALARA a radiologist must always be cognizant of time, distance, and shielding. The goal being to minimize exposure time, maximize distance between the radiation source and humans, and create barriers with lead aprons, thyroid shields, and lined walls in X-ray rooms, etc. In very simplistic terms X-ray beams can be controlled by adjusting the mA and kV. High mA is higher dose with crisp images. Low mA is lower dose with grainy images. High kV allows better penetration through soft tissues, but can decrease the image contrast. Low kV has less dose and more contrast, which is not a problem unless the patient is overweight, muscular, broad shouldered, or “big-boned.” The easiest way to explain how to reduce radiation exposure in medical imaging is by talking about each imaging modality.

Let’s begin with X-ray, the founding modality of my specialty. Most X-ray equipment have automatic sensors to detect the patient size and adjust the mA and kV settings accordingly. These work okay, but radiology is an art from taking the picture to analyzing the image. Many times, technologists select their own settings obtaining better quality images than the automated software. Aside from these settings, the best way to limit X-ray exposure is by reducing radiation dose. I only see the images sent to me. A good technologist can get a great image the first time. Additional X-rays add exposure, so getting the picture right the first time counts. Again, image count adds dose. If a clinical question can be answered with 2 or 3 views of the lumbar spine, then a 5 or 7 view series is not necessary. I’m sorry but I’m going to lump mammography in here. It is specialized X-ray and federally regulated. Mammography will be tackled in a future multi-part series.

Fluoroscopy is basically low dose real-time X-ray. This modality is used for dynamic imaging. Diagnostic radiologists perform barium exams (esophagram, Upper GI series, Barium enema),joint injections for MR arthrograms, and lumbar punctures most commonly. A good radiologist can perform their exams quickly and efficiently. By far, the vast majority of my time in the fluoroscopy suite is spent first introducing myself to the patient, explaining the procedure, drawing up any necessary medication, and making any adjustments I need to adequately position myself and the patient for a successful procedure. Preparation is key and will decrease procedure time and consequently dose. There is a setting for a radiologist to control dose by adjusting the frame rate, usually anywhere between 1 and 8 frames per second (time). When a patient is on the fluoroscopy table the source is under the table with the movable part on top called the tower containing an image intensifier that is the receiver. The closer the receiver is to the patient, the better the image. The further away the more the machine will try to compensate by increasing radiation dose (distance). Lastly, the machine has lead panels that can come in from the tops and sides to crop the image into portrait, landscape, or a smaller square providing a barrier (shielding).

Computed Tomography (CT) scan is super X-ray. It is like taking an X-ray through a single slice in your body and stacking them all up together to make a 3D image of your body. In fact, it used to be called CAT scan with the ‘A’ standing for axial. Axial is just a plane of viewing. An axial section is best described with Star Wars. When Darth Maul was cut in half, he was sliced axially. Now imagine if he was cut into another couple hundred of those slices. That is how a radiologist looks at someone’s body, laying flat on their back cut into a bunch of slices. The scanners are now much better and images can be reconstructed into any plane (axial – cut separates top from bottom; sagittal separates left from right; and coronal separates front from back). CT dose reduction has been radically improved over the past decade with software enhancements from the manufacturers. The machines can not only assess patient body habitus to modify dose, but can do it on a slice by slice basis using more radiation to get through the shoulder area where there is more bone and soft tissues and less at the abdominal level. CT has come a really long way providing less dose in combination with better imaging.

Nuclear medicine is a totally different game. The others we talked about were all external sources of radiation. In nuclear medicine, we administer radiation directly into your body. It is most commonly injected for heart scans, bone scans, thyroid scans, kidney scans, and liver/gallbladder scans. It could also be added to food (commonly scrambled eggs) and ingested. The great thing about nuclear medicine is that it is physiologic imaging. All the other studies in radiology are anatomic, but this is about function. Often the images seem to be of poor quality, but they provide important clinical information and can be used to assess for metastatic disease and organ function. Sorry, there is really no way to reduce dose here, but for bonus dose go for a PET-CT scan. Positron Emission Tomography in combination with CT scan combines anatomy with physiology. It is used most commonly in cancer imaging. Frankly, if you’ve got cancer decreasing radiation exposure is probably not your major concern. More importantly, your PET-CT results can be a strong indicator of response to treatment and is routinely utilized in cancer staging. So suck it up buttercup. This ones worth the extra dose.

Now I want to shift gears. The best way to reduce radiation exposure in medical imaging is to eliminate it. Ultrasound (US) and Magnetic Resonance Imaging (MRI) are two modalities with NO RADIATION. There are times when either of these modalities might provide the clinical information being sought. Just today I reviewed a CT of the brain of a very young child with the clinical indication of large head/macrocephaly. Thankfully it was normal, but the patient could have gotten the same diagnosis without the radiation exposure. In infants with an open fontanelle, US is hands down the preferred modality. Otherwise, I would suggest a rapid MRI scan. These are exams tailored for kids with fast scanning to reduce motion artifact. Now the images aren’t great, but they tell me everything I need to make a diagnosis and that is all that counts in my book.

So, assuming you’ve read this far, if your a patient hopefully that answered some questions, and if you are a referrer I hope you’ve learned about the importance of the radiologist. If you don’t know your radiologist(s), then meet them. It is their job to educate patients and healthcare providers to the risk, benefits, and alternatives in medical imaging. If you can’t find a nice, helpful one, then reach out to me. I’ll be glad to help. My Rad was designed for you.

Please comment below and let me know what you think!

Thanks,

Ron

 

 

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I am an American Board of Radiology certified Diagnostic Radiologist with a certificate of additional qualification in Neuroradiology. I absolutely love my job. I have learned a tremendous amount about the human body, including its’ expected complications given our extraordinary complexity, and get to use that knowledge to help people. I personally have experienced emotional devastation and loss, which has made me compassionate and empathetic. I really care about people, and I hope I can use this site to help you. I graduated medical school in 2004 from New York Medical College. My wife and I had our first son in NY where we bought our 900 sf two bedroom one bath starter home. I stayed at Westchester Medical Center for radiology residency, where we had our second son. I obtained a neuroradiology fellowship position at Yale New Haven Medical Center commuting about an hour and a half each way for a year while we had our third boy. Upon graduation I was fortunate to return to Westchester Medical Center to work in Neuroradiology, Body Imaging, and Women’s Imaging departments, a rarity in academic medicine. Almost a decade later and I am living in a larger home in Reno working in a private practice community based outpatient radiology group which contracts with a rural hospital in Elko, Nevada. My wife and I now have four boys and gave up on the girl. We also have a male Bernese mountain Dog named Helmut and female Newfoundland named Lucy. Despite all its hardships and tremendous struggles, I have an absolutely amazing life, which is a gift I cherish. It’s down to my philosophy. I am a firm believer in teamwork. So much comes down to communication. When healthcare providers talk to each other one-on-one, the patient care is always improved, every time! We might not find an answer to your problem, but our collective knowledge sure can help improve your chances. At Yale the best conference I ever regularly attended was a head and neck tumor board. The head and neck surgeon (otolaryngologist = ENT) presented the patient’s clinical history, the radiologist showed the images, the oncologist discussed the tumor and chemotherapy options, and the patient came to the conference and we all did a physical exam looking into their mouth to directly visualize a tumor. It was incredible! Patients came from far and wide to see this highly trained, world-renowned, humble, Japanese, gentleman surgeon. It was also an epiphany. I found that when I see the patient, talk to them, listen to their story, examine them and discuss the patient with my colleagues, the patient felt better and I had a lot of fun. It’s weird but reminds me of seeing a comedy where it is always funnier in a packed theater with everyone laughing. Knowledge and compassion are both infectious and contagious. My greatest days are helping patients deal with some of their most difficult days, and I am good at it.

2 thoughts on “How to decrease or eliminate radiation exposure in medical imaging

  1. This is a very informative article. Thank you Dr. Swanger for helping to clarify the importance of what radiologists do and the need for radiation safety and education. Keep up the good work!

    Like

  2. This article is so well explained and the epic analogy very much helps people understand axial slices in MR! It is always the hardest to explain, so i may have to borrow your wording…
    Also- thanks for explaining the PET-CT uses and why it is important !

    Like

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