Chest radiographs, commonly referred to as “chest x-rays,” are one of the most commonly ordered radiology studies in the world. In fact, odds are you or someone you know has had at least one.
As with most things in medicine, it’s essential to know what the test you’re getting is, why you’re getting it, and what the results mean/how they impact your health.
So What Is a Chest X-ray?
A chest x-ray is an image (picture) of the chest created by passing a beam of x-rays (a form of energetic light that we can’t see) created by an x-ray machine through the chest to a detector. Think of this as a fancy camera that takes pictures of a special form of light normally invisible to us. While our eyes may not be able to see an x-ray, we have special cameras that can (similar to how night vision goggles can see better in the dark and infrared cameras can see heat signatures). This is literally x-ray vision.
As the x-rays pass through a person’s chest, many of the x-rays are absorbed by the structures inside the chest – the heart, bones, aorta and blood vessels, muscles, fat, etc. X-rays that are not absorbed will pass through a patient’s chest, hit the detector, and create a digital image.
This essentially creates a density map of the chest. Dense structures, like the bones, absorb most of the x-rays and appear “white” on the image. Low-density structures, like the lungs, allow x-rays to pass through the patient, hit the detector, and appear “black.”
A chest radiograph simply refers to taking an x-ray picture of the chest, but there are multiple different ways to take a chest x-ray, referred to as “views,” that include:
- Frontal View – This is a picture of a patient’s chest from front to back or back to front (both are processed to look the same on a computer screen). It gives the most information of all of the views (the bread and butter or meat and potatoes – choose your preferred food analogy 😉). Frontal views are taken with patients in an upright position (but can be taken with patients lying down or partially upright if the patient cannot be fully upright).
- It can be taken from behind (posterior) the patient with the patient’s chest against the detector (located anteriorly). This is referred to as a PA (posterior to anterior – the direction of the x-ray beam through the patient) view and is the preferred view.
- It can be taken from in front of (anterior to) the patient with the detector behind the patient (located posteriorly). This is referred to as an AP (anterior to posterior – the direction of the x-ray beam through the patient) view. This view can cause the heart to look larger than it actually is (the heart is further from the detector and casts a larger shadow on the detector).
- X-ray images are frequently labeled with either a PA or AP.
- Lateral View – An image taken from the side of the patient, 90 degrees/perpendicular from a frontal view, with the patient upright. This view helps determine where pathology is located (is it in the front, middle, or back of the chest?).
- Lateral Decubitus View – Similar to the standard lateral view, but with the patient lying on their side. This can be helpful to look for a pleural effusion (fluid between the lung and chest wall). The patient is placed with the side of the suspected pleural effusion on the table to make the pleural effusion more apparent.
- Apical Lordotic View – This is a fancy name for a picture of the upper portions of the lungs near the collar bones (the “apices” in medical jargon). The collar bones sit in front of the top of the lungs and can sometimes be hard to see behind. This view is taken with a slight upward angle that moves the collar bones out of the way, better showing the upper lungs. This view is performed on an “as needed” basis as a problem-solving measure (is there a real finding or is it artifactual and can be ignored?).
- Rib Views – Only the back portions of the ribs are well seen on a frontal chest x-ray and the ribs are not well seen on the lateral view. Rib x-rays are taken from angles to better see the side and front portions of the ribs and are necessary views to rule out rib fractures.
When and Why Are Chest X-rays Ordered?
Chest x-rays are ordered for a number of reasons. In the radiology report, this is known as the “indication,” “history,” or “clinical history” section. These are interchangeable and vary based on personal preference.
Every medical test, including every imaging study, should serve a purpose by answering a specific clinical question. We don’t expose patients to radiation unless necessary.
Some common reasons to order a chest X-ray include:
- To investigate symptoms:
- Chest pain, shortness of breath, cough, or fever may prompt a chest X-ray to see what’s going on. Is there evidence of pneumonia, a pleural effusion (fluid between the lung and chest wall, known as the pleural space), or congestive heart failure where heart disease can lead to fluid building up in the lungs referred to as pulmonary edema (fluid in the lungs)?
- To monitor:
- Chest x-rays may be used to monitor the lungs in patients with certain diseases that frequently affect the lungs (e.g., some autoimmune diseases), in patients taking medications that may cause lung toxicity, or to ensure a pneumonia resolves (goes away), particularly in patients with risk factors for lung cancer to make sure a lung cancer was hiding in or masquerading as a pneumonia.
- As part of a routine check-up:
- Sometimes, chest X-rays are part of pre-op (prior to surgery) or annual health checks in certain patients. They may also be performed as part of a pre-employment process in certain professions.
- In emergencies:
- Chest x-rays are often obtained in emergency rooms to assess patients in the setting of trauma.
- Chest x-rays can be quickly obtained to look for injuries requiring immediate intervention, such as a pneumothorax (which can result in a collapsed lung) or a widened mediastinum (which can be seen with injury to the aorta – the largest blood vessel in the body). These entities will generally lead to an emergent chest CT (computed tomography) to more fully evaluate the extent of the traumatic chest injury(ies).
- Dedicated rib radiographs (x-rays) are performed at several different angles to better see the ribs and look for rib fractures.
- Chest x-rays are often obtained in emergency rooms to assess patients in the setting of trauma.
Before Your Chest X-ray
Before your chest x-ray:
- You’ll typically be asked to wear a gown and remove any metal objects, like jewelry or clothing with metal fasteners. Metals are very dense and can hide pathology in front of or behind the metal. The bigger the metal object, the more information it obscures/hides.
- Tell your doctor if you’re pregnant or think you might be pregnant. While the amount of radiation a patient and fetus (developing unborn baby) receives from a single x-ray is essentially negligible, it’s not zero and the potential for harm likely increases with higher levels of radiation. Although the risk is extremely low for a single chest x-ray, your doctor may reconsider whether or not an x-ray is necessary or consider an alternative imaging option.
- If you require imaging while pregnant or have had an x-ray while pregnant, rest assured that the risk to you and your fetus is essentially zero. Even a single CT of the abdomen and pelvis, which has much higher radiation levels than an x-ray, is thought to have no adverse effect on a fetus. However, attempts should be made to limit your radiation exposure in the future.
- You’ll typically stand or sit in front of the x-ray machine with your chest to the machine.
Normal Chest X-ray Results
Radiology reports have a lot of variability, in both their structure and content, dependent on each individual radiologist’s preference. Radiologists often use templates for their reports. Many institutions have also been shifting to standardized reporting where all radiologists use the same report templates to increase consistency in reporting.
A normal chest x-ray shows:
- Clear lungs
- Normal-sized heart and mediastinal structures (often referred to as the “cardiomediastinal silhouette” since we’re looking at the shadow of the heart; the mediastinum is the space between the lungs, spine, and sternum, containing the heart, blood vessels, lymph nodes, and central airways)
- Intact bones (ribs, spine, imaged portions of the shoulders and collar bones)
The lungs should be black, with branching white lines, which are shadows from the blood vessels and walls of the airways. The diaphragm (the large dome-shaped muscle at the base of the lungs that helps with breathing) should be visible as a curved line at the base of each lung.
Remember, a normal chest x-ray can be reassuring, but a normal chest radiograph can sometimes miss a fair amount of abnormalities and is therefore not the end all be all. If you have persistent symptoms, your provider may recommend further evaluation, such as a chest CT, even with a normal result.
Some examples of normal chest x-ray results, typically under an “impression” or “conclusion” at the bottom of the report, include:
- Normal.
- Normal chest x-ray.
- No acute cardiopulmonary abnormality.
- No acute cardiopulmonary disease.
- Negative.
- No acute process.
Abnormal Chest X-ray Results
Abnormal chest X-rays show signs of disease or injury. Radiologists review chest X-rays for normal and abnormal findings to explain a patient’s symptoms as well as look for any important incidental findings. Radiologists closely review images and combine the abnormal imaging findings with clinical history to ensure accurate interpretation of each exam. I personally consider every chest x-ray to be abnormal until I can prove otherwise (and rule out common and uncommon abnormalities within the chest).
Radiologists will contact a patient’s ordering provider if there are radiographic findings that require immediate attention (such as a pneumothorax with a collapsed lung) or findings highly suspicious for cancer (such as lung cancer) to make sure patients get expedited care/don’t fall through the cracks.
Some common abnormalities are:
- Pneumonia: hazy or patchy opacities (cloudy areas) in the lungs (bacteria and pus are more dense than air; lungs filled with something other than air)
- Lung cancer: masses or nodules (typically round- or oval-shaped spots, sometimes with poorly defined margins) in the lungs
- Chronic obstructive pulmonary disease (COPD): hyperinflated lungs (larger and darker than normal)
- Pleural effusion: fluid in the pleural space (the area between the lungs and the chest wall)
- Pneumothorax: air in the pleural space which can cause the lung to collapse
- Fractures (ribs, spine, collar bones, shoulders)
- Enlarged heart or mediastinal structures (structures inside the chest between the lungs where the heart and big blood vessels are located)
- Enlarged lymph nodes
- Foreign body (swallowed, inhaled, or in the chest wall)
What Happens After a Chest X-ray?
After your chest X-ray:
- The technologist will complete your exam and it will be placed on a worklist for a radiologist to read (interpret).
- Your doctor will tell you the results and discuss any findings if necessary.
- If the x-ray is abnormal, you may need further imaging tests such as a CT scan (a more detailed x-ray) or MRI (which uses magnetic fields to create images).
- If the X-ray is normal but you have symptoms or risk factors for lung disease, you may still need further testing or treatment.
Note: We are currently experiencing a significant national radiologist (and healthcare worker in general) shortage in the United States. This, unfortunately, is resulting in a delay in interpretation of most exams at many practices at the time of this writing. We are doing our best to read exams in a timely fashion while maintaining a high standard of care. Your health matters and we are doing our best to keep up with the ever-increasing volumes.
Safety of Chest X-rays
Chest x-rays use a tiny amount of radiation and are generally considered safe as the benefits of accurate diagnosis and treatment usually outweigh the potential risks.
For perspective, a standard single chest x-ray radiation dose is estimated to increase your chances of developing a future fatal cancer by 0.0005% based on current conservative modeling. It’s not 0, but awfully close. Radiation risk is thought to be cumulative (add up over time), so it’s important to try and limit your lifetime radiation exposure to minimize any radiation-related risks.
Limitations of Chest X-rays
While chest x-rays can be very helpful, it’s important to understand their limitations.
Chest X-rays Don’t See Everything
Small abnormalities such as lung nodules, cancers, pneumonias, etc. may be difficult or impossible to see on x-ray.
Since a chest x-ray is a 2-dimensional image of a 3-dimensional object, structures can overlap. This can hide underlying pathology.
Dependent on Quality of Deep Breath:
An x-ray, just like a photograph, is a snapshot of a single moment in time. A good inspiration (taking a big breath in) is key to obtaining a high-quality chest x-ray. A poor inspiration can result in partial collapse of areas of the lungs, which can look like either infection or fluid in the lungs (pulmonary edema) when the lungs are actually normal.
X-Rays Only Detect Significant Differences in Density
Stark differences in density are easy to differentiate (bone vs. soft tissue vs. air) but a soft tissue abnormality in a background of soft tissue (e.g., a liver tumor in the liver) won’t be visible by x-ray alone. Think of it as looking for a specific piece of hay in a haystack (though x-ray would be excellent for detecting a metal needle in a haystack!).
This also means that a chest x-ray can assess the size of the heart, but that’s about it.
CT, which also uses x-rays to create images, offers much more anatomic detail and is better at distinguishing between structures that are closer in density compared to radiographs.
Chest X-Ray Findings are Often Nonspecific
X-rays will show differences in density, but a lot of things can look similar or the same. For example, when we see an “opacity” (a white spot) in the lungs, it simply means there’s something in the lung that shouldn’t be. Radiologists use clinical history and appearance to try and narrow down what the cause is but fluid, pus, blood, and tumor can all have a similar appearance on a chest x-ray.
Example: If the patient is coming in with a cough and fever, it’s probably pneumonia.
Clinical Correlation
Given that many diseases can have a lot of imaging overlap (look the same on chest x-ray and even chest CT), clinical correlation plays a crucial role in differentiating between different entities.
For example, pneumonia and pulmonary edema can both cause difficulty breathing but pneumonia may also present with a fever, runny nose, sick contacts, etc. while pulmonary edema patients generally have an underlying heart issue that causes the backup of fluid into the lungs.
Important Questions to Ask
In a sense, I like to think of a chest x-ray as a screening tool – “to CT or not to CT.” Can the x-ray on its own answer the question?
Is a negative/normal chest x-ray sufficient to alleviate concern?
Or is there sufficient concern to justify obtaining a chest CT if the chest x-ray is normal?
Because of the limitations above, your doctor may recommend further testing even if your chest X-ray is normal, especially if you have persistent symptoms. These could include:
- CT (Computed Tomography) – provide more detailed cross-sectional images that give a better, more complete look at what is going on
- PET (Positron Emission Tomography) – helps identify lung cancer and other cancers as well as the extent of cancer spread
- MRI (Magnetic Resonance Imaging) – good at imaging soft tissues, though less often used for imaging the chest as MRI has significant limitations evaluating the lungs
- Lung function tests, blood tests, or biopsies depending on your symptoms and concerns
Remember, a chest x-ray is often just the first step in diagnosing or ruling out conditions. Your doctor will consider your x-ray results along with your symptoms, medical history, and other tests to give you the most accurate assessment of your health.
Conclusion
A chest x-ray is a valuable diagnostic tool that can provide valuable information with regard to your lungs, heart, and in the setting of trauma. Understanding your x-ray results, whether they are normal or abnormal, helps you take control of your health.
If you have any questions or concerns about your x-ray results, don’t hesitate to discuss them with your doctor. You are your best advocate!
Enjoyed learning something new? Your support through Buy Me a Coffee helps me create more educational content like this! ☕✨