Radiology Alphabet Soup
In the spirit of teaching old dogs new tricks, I’ve learned how to take X-rays recently. I mean, not INTERPRET X-rays: I’ve been working on that for over 15 years. In that department I’m always trying to sharpen my skills and letmetellya I’m thankful for my colleagues in pediatric radiology! Anywho- over the past year or so I’ve been working on acquiring the skill of shooting X-rays myself, as in take-the-picture. It’s kind of fun: you work swell machinery and position the body part of interest just-so in several different ways to get a few pertinent views of the bones and parts inside. So since I’m feeling a bit ON A ROLL I thought it might be helpful to jot down a few sentences about what I think you should know about various types of radiology—X-rays (fondly known as “plain films,”) CT scans, Ultrasound and MRI. We’ll stick to the basics so that it stays digestible.
First, regular ol’ X-rays are what everyone typically thinks of when they see a black and white skeletal image.
And plain films are good at exactly that- getting a nice two dimensional image of bones and big structures. They are by far the image of choice when trying to determine if a fracture (break) is present in a bone. X-ray machines are handy in that some of them are portable so they can come TO the patient, instead of the patient going to another location to get the study done. As you can imagine, in a critically ill person, this can be tremendously helpful diagnostically. It’s important to note that X-rays do emit some radiation, which is why the parts of the body that are NOT being X-rayed are covered with lead to protect the rest of the body from the radiation. The dose is small, but a link has been established between the cumulative dose of radiation over a lifetime and the risk of cancer, so we are careful about:
- Getting an X-ray in the first place, and
- Covering up the rest of the body, especially the thyroid gland in the neck, and the reproductive organs during the filming.
X-rays are also useful when trying to identify if a pneumonia is present in the lungs, or when assessing the overall size of the heart. A variety of uses, really, and fast. It’s like taking a picture with a camera: that quick, which means holding still for a long time isn’t necessary (things we think about in pediatrics).
Another form of radiology that also emits radiation (more radiation, in fact, than a regular X-ray) is the CT (computed tomography) scan. This scan produces 3-D images and is helpful for getting a more in-depth look at the soft body parts and hollow organs. It can be done *relatively* quickly and so younger kids can sometimes hold still and don’t need to be sedated for this study, either. Most commonly CT scans are done in the setting of head trauma to look for signs of intra-cranial (inside the head) bleeding, or abdominal CTs to look for masses or damage to the viscera in the setting of trauma, or even searching for kidney stones. In some situations contrast is given to enhance the picture. This can be done orally, intravenously, or (wait for it—) rectally. Or one, two or all three of those. The contrast is given as a dye that gets picked up during the scan and can give the physician reading the film a more detailed image of the target area. CT scans take a little bit longer to obtain than an x-ray because multiple “pictures” have to be taken to make up the entire image series. The CT image is obtained by lying down on the scanner table while the machine moves and adjusts to capture the various images.
Similarly, MRI or magnetic resonance imaging, is another radiology test that obtains multiple pictures or “slices” of the body part of interest. What’s different about MRI is that it uses NO radiation and instead is a study that uses a magnetic field and radio waves to create the image. The physics of how this actually works is far beyond my comprehension (which comes to a full stop at F= MA [force equals mass times acceleration]), but- MRI produces amazingly detailed high resolution images of organs, tissues and bones. The tricky business with MRI and kids is that MRIs can take up to 45 minutes to actually obtain the study— so it means lying still in a small tubular space for about 44 and a half more minutes than most kids can conceivably do. Common areas of interest for MRI imaging are the brain, spinal column, and joints. The MRI machine itself takes up a lot of space and is expensive to make and operate, and this is one of the many reasons that there are fewer of these around. The technology continues to improve, however, and MRI is available at most hospitals, even small community ones.
The last big category that I want to highlight today is ultrasound.
This modality uses sound waves to capture images by measuring the depth of those sound waves across various tissue densities, ultimately generating an image that looks vaguely like bad static on a television when you turn the channel to 4 and it’s supposed to be on 3 to align with the cable box. I’m here to tell you that there are people in this world who can interpret that static beautifully, and in no time can indicate whether or not someone has appendicitis or an ovarian cyst. Ultrasound is used to look at the heart function as well. This is known as echocardiography, and echo machines are mostly all on wheels so that they can travel to wherever the sickest patients are if necessary. Based on the echo readings clinicians can determine the actual blood pressures in the various individual heart chambers as well as assess the integrity of the heart valves and the heart muscle itself. Pretty cool.
When it comes to radiology images for your child, make sure you know these details:
- How long will the study take?
- Does my child need to have an empty stomach before the test?
- Will this require an IV and contrast?
- Will my child need to be sedated for the study?
What I hope comes across here is that not one of these imaging modalities is necessarily better than another; they’re just different and serve different purposes depending on the clinical scenario. Some people seem to think that if they can get an MRI then that’s better than a CT, and that’s just plain not always true. All of these tests have their pros and cons, and it’s important to be familiar with them just a little bit so that if you or your child needs one of these someday, you’ll ask the key question: “is this the right test for this situation?” and you’ll understand the answer that you’re given.
I’ll keep you posted on how I’m doing in the “taking X-rays” department: awhile ago I X-rayed a plastic cup filled with pretzels and it made for quite a pretty picture. The ankle I did the other day turned out ok too. Negative for fracture!