HRCT (High-Resolution Computed Tomography)

What is an HRCT (high-resolution computed tomography) scan?

An HRCT (high-resolution computed tomography) scan is an imaging procedure that healthcare providers use to get detailed pictures of the inside of your lungs. These pictures can show changes to the structures in your lungs; specifically, conditions that affect your small airways, air sacs (alveoli) and the tissues around them.

During the procedure, you lie still on a table while the CT scanner moves around you. It takes X-ray images — called slices — from many different angles. Then a computer combines them into three-dimensional (3D) images.

What is the difference between HRCT and CT scan?

HRCT scans are much clearer and more detailed than a standard chest CT scan. Think of it like a picture book with pages thin enough to see through. Take the pages out in stacks of equal thicknesses. A standard CT scan is like looking at one entire stack from the top and seeing all of the pictures on top of each other — the entire book is there, but you might not be able to see each picture as clearly as you’d like. HRCT is more like seeing each page individually.

During an HRCT, your provider can also get images in different positions (either lying on your stomach or your back) or while you inhale or exhale, which can change what the provider can see in the pictures.

What is the HRCT test used for?

Your provider can perform an HRCT to look for specific changes in your lungs. They might use it to monitor a known disease or in cases where you have symptoms but X-rays don’t show the issue. Providers can use it to evaluate:

• Bronchiolitis and other small airway diseases.
• Emphysema.
• Interstitial lung disease, including pulmonary fibrosis, nonspecific interstitial pneumonia, sarcoidosis and asbestosis.
• Lymphangioleiomyomatosis (LAM).
• Lymphangitic carcinomatosis.
• Pulmonary alveolar proteinosis.

How do I prepare for an HRCT scan?

You should wear comfortable clothing and limit jewelry on the day of your HRCT scan. Your provider will have you remove anything metal that could interfere with the images. Let your provider know if you:

• Are pregnant. Your provider can tell you if a CT scan is safe during pregnancy.
• Feel anxious in enclosed spaces.
• Don’t feel like you can lie still for the procedure.

What happens during an HRCT scan?

During an HRCT scan:

1. Your provider will help you lie on a table. They may position you on your back (supine) or belly (prone).
2. The bed will slide into a scanning machine that looks like a tube.
3. The scanner will rotate around you and the table might move forward and backward while the scanner takes pictures.
4. Your provider will tell you to either breathe in or breathe out and hold your breath at certain points during the scan. Follow their directions as closely as possible.
5. When the provider has all the images they need, the bed will slide out of the scanner so you can get up.

How long does an HRCT take?

The scan itself only takes five to 10 minutes. Including preparation, you can expect to spend 30 minutes to an hour getting an HRCT scan.

What happens after an HRCT scan?

After an HRCT, a radiologist and your provider will read the scan. This can take a few days, depending on how busy the providers are. Ask your provider when to expect the results and how they’ll contact you if they see anything they need to discuss.

What are the advantages of an HRCT?

The advantage of an HRCT is that it shows more detail than a standard CT scan, which is important in evaluating certain lung conditions. HRCTs are done without a contrast agent, which means there are no needle sticks or risk of allergic reactions.

What are the disadvantages of HRCT?

An HRCT scan takes longer than a standard CT. It also exposes you to ionizing radiation. Too much radiation can lead to health issues like cancer.

When should I call my healthcare provider?

Contact your healthcare provider if you have any questions about the HRCT scan or the results.

A note from Cleveland Clinic

To see a complete picture, we sometimes need to zoom in on its parts. Some people might use a microscope, magnifying glass or a telescope to see things more clearly. Radiologists and pulmonologists use HRCT to get a closer look at your lungs. This helps them understand changes in your small airways, alveoli and the tissues around them.

Some people feel nervous waiting for the results of imaging scans. It might be helpful to remember that getting more information about what’s going on inside your body can help you and your provider find a treatment plan that’s right for you.