Most of you reading this have had a medical imaging scan of some type before. I cannot remember a single day of practice during which I have not ordered one. Scans can give us a ton of information, but they can be costly and potentially can cause harm. You may be exposed to intravenous contrast (aka dye), or exposed to radiation. Frequently we find benign lesions called incidentalomas, which are benign lumps. These never would have caused you any harm, but now we have to get multiple scans in order to ensure that it’s not cancerous.   As a Wise Patient, you should know the basics about the imaging scans that your doctor may order for you. 

X-ray

Everyone has had an x-ray, right? They were initially developed by German scientist Wilhelm Roentgen in 1895. Initially x-rays were called Roentgenograms, thankfully someone changed the name. X-rays are great at evaluating bones, the spaces between them, and lungs. Occasionally we will use them to look for air or stool in the abdomen and to look for kidney stones. X-rays involve just a quick photo shoot and you’re done. 

CT Scan

Computed Tomography is also called a CAT scan. These scans may be used with or without contrast. Contrast is an injection of iodine containing substance through an intravenous line (IV) placed in your arm. The contrast will light up certain structures and give the radiologist more information. CT scans emit radiation in order to create an image. Getting a CT scan done involves a quick ride through what appears to be a long donut. You lay on a flat table that moves you through a circular scanner only 1-2 feet thick. Its open on both sides so most patients with claustrophobia have no trouble with this. CT scans are used to evaluate the abdomen (appendicitis, diverticulitis, kidney stones etc), the chest (blood clots, lung nodules, lymph nodes) and a quick scan of the brain to look for bleeding. CT scans are versatile and can be used in many situations. 

Ultrasound 

An ultrasound is a simple and safe test. Of all the scans, this may be the one that brings people the most joy – seeing their child for the first time. It involves having a technologist rub jelly on your skin and they will use a small probe the size of a TV remote to go over the area that the doctor wants to evaluate. This probe emits sound waves that bounce off your organs and bones and fluids to give the radiologist a picture. This scan can take 15-30 minutes depending on what is being evaluated. Ultrasound is great at looking at the heart (also called an echocardiogram), looking at reproductive organs, the thyroid, the liver and the gallbladder. 

MRI

Magnetic resonance imaging is one of the most sensitive imaging modalities, meaning it can see details that other scans cannot. It uses magnets to create a detailed picture of a very specific and localized area. It uses no radiation. We will sometimes use contrast to give us a better picture. Unlike the CT scan, an MRI uses a different kind of contrast based on a substance called gadolinium. MRIs are not quick nor easy. Each scan can take 30-45 minutes. During that time you may be in a closed tunnel, which causes some people to feel claustrophobic. If you have issues with claustrophobia, it may be a good idea to ask your doctor about taking a medication to calm you prior to these scans. MRIs are usually used to evaluate your brain and spine, joints, and men’s prostates. 

Radiation

CT scans and x-rays both use radiation to give us an image. Enough radiation can cause cancer over time. Radiation is measured in units called millisieverts (mSv). We are all typically exposed to 3 mSv per year just from the radiation in our environments and the sun. If you live in Colorado, like I do, then we are probably exposed to 4.5 mSv per year due to our altitude. There is a great chart comparing the amount of radiation that we are exposed to from different scans:

https://www.radiologyinfo.org/en/info.cfm?pg=safety-xray

Contrast

Iodine contrast, used in CT scans, can cause acute kidney injury. This is a temporary dysfunction in the filtering function of the kidney that is usually resolved with IV fluids. Some medications, like metformin, can interact with the contrast to make kidney damage worse, so be sure to ask your doctor what to do if you are going to get contrast. If you are having a thyroid storm, or acute hyperthyroidism, this can be made worse by contrast. 

Incidentaloma

One of the most common issues with imaging is the incidentaloma. These are nodules that are incidentally found while scanning for something else. Common incidentalomas are liver lesions, lung nodules, adrenal nodules and kidney cysts. Imagine you went to the doctor with abdominal pain and your doctor was concerned that you had gallstones. He/she would order an ultrasound to evaluate for this. The good news is that you don’t have gallstones. The bad news is there is this small indeterminate lesion that the radiologist happened to see in your liver. S/he thinks it’s probably a blood vessel collection called a hemangioma, but can’t be sure. So he/she recommends a follow up CT scan. The CT scan shows that it is a small nodule, but it doesn’t look cancerous. Again we cannot be certain. So the radiologist recommends a repeat CT scan in 3 months. If its stable then you are good. You can see how this little lesion ended up causing a lot of anxiety, extra exposure to radiation, and extra cost to everyone. We have guidelines to minimize the repeat scanning that we do, however, we have to pursue these incidentalomas to ensure that they are not cancerous. 

So I hope this sheds some light on some of the basic radiology tests that we do. As I mentioned these tests can be quite helpful, but as with everything we do, they do not come without their own risks. In reading this I hope that you can help your doctor in making an informed decision if needed. 

If you would like to learn more about the sensitivity and specificity of medical imaging tests, read my article No Test is Perfect.