A chest x-ray is one of the quickest and most common imaging tests. The entire process, from walking into the room to walking out, takes just a few minutes. Here’s what happens at each step so you know exactly what to expect.
Before the X-Ray
There’s no special preparation needed. You don’t need to fast or stop taking medications. When you arrive, you’ll be asked to remove jewelry, watches, necklaces, eyeglasses, and any metal objects from your upper body. Metal blocks x-ray beams and creates bright white spots on the image that can hide important details. Depending on what you’re wearing, you may need to change into a hospital gown. A t-shirt without metal snaps or zippers is usually fine, but bras with underwire typically need to come off.
How You’ll Be Positioned
For the standard view, called a PA (posteroanterior) image, you’ll stand upright with the front of your chest pressed flat against a large, flat panel. This panel contains the image receptor that captures the x-ray. The technologist will then ask you to rotate your shoulders forward and place your arms at your sides or your hands on your hips. This movement pulls your shoulder blades out to the sides so they don’t overlap with your lungs on the image.
Many exams also include a lateral (side) view. For this, you’ll turn 90 degrees and stand with one side of your body against the panel, arms raised above your head. Between the two views, the technologist gets a front-to-back and a side-to-side picture of your chest.
The Actual Exposure
Once you’re positioned, the technologist will step behind a protective barrier and give you a specific breathing instruction: take a deep breath, exhale, then take another deep breath and hold it. The x-ray fires while you’re holding that second breath. You won’t feel anything. There’s no pain, no sensation at all.
Holding your breath matters because your lungs need to be fully expanded and completely still. Even slight movement from breathing blurs the image. A full, deep breath also spreads the lung tissue out, making it easier to spot abnormalities that might hide in collapsed or partially inflated lungs. The actual exposure lasts a fraction of a second.
If You Can’t Stand Up
For patients who are bedridden or in a wheelchair, a portable x-ray machine is brought to the bedside. If you can sit upright, a staff member positions the image receptor behind your back or you hold it against your chest. If you can’t sit up at all, you lie flat on your back with the receptor slid underneath you, and the x-ray beam shoots from front to back. This produces a slightly different view than the standard standing image, but it still gives doctors the information they need.
What the Image Shows
X-ray beams pass through your body and are absorbed differently depending on tissue density. Dense structures like bones and the spine absorb most of the radiation and appear white. Your heart, which is a thick muscle filled with blood, also appears as a lighter area. Air-filled lungs block very little radiation, so they show up as dark areas. Fat and muscle fall somewhere in between, appearing as shades of gray.
A radiologist reads the image looking for several things. The size and outline of your heart can reveal heart failure or fluid around the heart. The large blood vessels near the heart, including the aorta and pulmonary arteries, are visible enough to show aneurysms or other vascular problems. Lung tissue is checked for signs of infection like pneumonia, masses that could indicate cancer, or air collecting in the space around a lung. Rib and spine fractures show up clearly. Even calcium deposits in the heart or blood vessels can be detected, which may point to damage in coronary arteries or heart valves.
Radiation Exposure
A chest x-ray delivers about 0.1 millisieverts of radiation. To put that in perspective, the average person in the U.S. absorbs about 3.1 millisieverts per year just from natural background radiation (from the ground, the air, and cosmic rays). A single chest x-ray adds roughly the equivalent of one day’s worth of natural exposure. It is one of the lowest-dose imaging tests available.
You might expect to be draped with a lead apron, but current guidelines from the American Association of Physicists in Medicine, supported by the American College of Radiology and the Radiological Society of North America, recommend against routine shielding during diagnostic imaging. After decades of research, there’s no evidence that the radiation from standard x-rays damages reproductive organs or harms a fetus. Shielding can actually cause problems: if it covers an area the radiologist needs to see, the entire exam may need to be repeated, doubling your exposure. Modern x-ray equipment also uses significantly less radiation than older machines, with some newer devices reducing exposure to surrounding tissues by as much as 96 percent. That said, some states still require shielding by law, so practices in those areas will follow local regulations.
Getting Your Results
In an emergency setting, results are typically available within minutes to a few hours. For routine, non-emergency chest x-rays, expect results within one to two days. A radiologist reviews the images and sends a report to the doctor who ordered the test. If anything abnormal shows up, your doctor may recommend follow-up imaging, like a CT scan, for a more detailed look.