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How to Read a CT Scan Report: Decoding Common Terminology

How to Read a CT Scan Report

Learn how to read a CT scan report and understand some common medical imaging terminology.

A CT scan creates detailed images of the internal structures and workings of your body using X-rays. A doctor might refer you for a CT scan to diagnose, identify or monitor the treatment of illnesses or injuries.

In Canada and the U.S., you have the right to access your health information contained in medical or health records. Having access to your medical records, including CT scan results, allows you to advocate for your own health and treatment, while also relieving ‘scanxiety’, the stress of waiting for medical results. A 2023 Leger study revealed more than half of patients experience ‘scanxiety’ when waiting on medical results.

With PocketHealth, you can get early access to your medical images and reports, often as soon as they’re released by the hospital imaging department or clinic. Access your records here.

But even when you have access to your health records, that doesn’t mean they’re simple to read or understand. Medical reports are still full of complex terminology. This article will clarify some of the medical terms and abbreviations you might encounter in your CT scan report so you’ll know where you stand and can be more prepared for conversations with your healthcare team.

What does CT stand for?

CT is short for computed tomography. Also known as a CAT scan, a CT scan uses a donut-shaped array to take multiple X-rays from many different angles, creating a 2D cross-sectional “slice” at one location within the body. These slices are then collected at multiple contiguous locations and combined digitally into a detailed 3D image.

A radiologist will interpret these images (sometimes hundreds or thousands of images in one exam) and create a detailed report. Most commonly, your referring physician will receive the radiology report and discuss the results with you at a follow-up appointment.

A CT scan provides much more detail than a single X-ray and can be used to locate clots and tumors, identify bone or muscle issues, examine organs, diagnose specific illnesses and monitor treatment.

How to read a CT scan

A CT scan report may seem complicated, but once you understand the main principles it will be much more comprehensible to read. Below we’ll explain planes, density, the Hounsfield scale and other important components you’ll find helpful in interpreting your CT scan report.

What are the coronal, sagittal and axial planes?

The term “plane” is used to describe the viewing angle of a patient in a CT scan image. Images are obtained in 1 plane and then reconstructed along 3 different planes to provide the radiologist with a 360° view of your body’s internal structures and organs:

  • Coronal: the frontal view, which presents images from the front to the back of your body.
  • Sagittal: a side view, which provides lateral images from the left to the right sides of the body.
  • Axial: also called the transverse view, this horizontal view creates images from the top to the bottom of your body.

What’s contrast?

Some CT scans require a contrast agent, a liquid composed of iodine that works by making structures with contrast appear more white (see “density” below). In a CT scan with contrast, an abnormality may become more obvious, either because it appears denser with contrast (enhancing/hyper-enhancing) or because the surrounding tissue becomes brighter, outlining the abnormality (hypodense).

Contrast for a CT scan is most commonly administered in 3 ways:

  1. An intravenous (IV) contrast agent is injected into your body to highlight areas of increased blood flow, like blood vessels or organs (e.g. liver, kidneys or spleen).
  2. An oral contrast agent is swallowed and helps CT scans better identify areas of the esophagus, stomach and intestines.
  3. A rectal contrast agent is inserted in the rectum to improve CT images in the large intestines and pelvic organs.

A CT scan with contrast might make use of the multiphase imaging technique, which takes images at specific points in time, for instance as the contrast reaches specific blood vessels or moves through specific organs.

How to read CT scan images?

CT scan images show up in shades of gray, from white to black. These shades measure the density (or lucency) of each of your internal structures compared to the next. As X-rays pass through a person they are absorbed in varying degrees (depending on the material of the bones, tissues or organs they encounter) before being captured digitally.

A way of quantifying the absorption of X-ray beams as seen on CT scans was first described by Sir Godfrey Hounsfield. Tissues that absorb X-rays are termed dense and appear white; conversely, tissues that do not absorb X-rays are termed lucent and appear black. Here’s a breakdown:

  • Dense structures appear lighter on CT scans. Bone and calcifications (like bladder or kidney stones) are all considered dense.
  • Lucent structures appear darker on CT scans. Air and fat are lucent, so areas like your lungs show up darker in a CT image.
  • Density can also be described relative to surrounding tissues:
    • Hypodense means an area is darker or less dense than the tissue or structure around it.
    • Hyperdense means an area is brighter or more dense than the tissue or structure surrounding it.

What’s the Hounsfield scale?

The Hounsfield scale measures tissue density and assigns a common scale to express how different tissues in your body absorb the radiation from the CT scan. This process of absorption is called attenuation.

Hounsfield units (HU) are standard numbers on the scale that express the radiodensity of different parts of the body, relative to water (assigned as zero). Your CT scan report may contain HU scale numbers when certain masses or cysts are reported.

The lower the number on the Hounsfield scale, the less dense the tissue is. The higher the number, the more dense the tissue is. For example:

  • Air: –1000 HU
  • Fat: –100 HU
  • Water: 0 HU
  • Soft tissue: 30 to 45 HU
  • Blood: 60 to 90 HU
  • Bone: 300 to 1000+ HU

What abnormalities can a CT scan detect?

Based on the radiologist’s review of the CT scan images, they’ll determine the presence of any abnormalities (often termed “findings” or “observations” in radiology lingo). Some descriptors of findings you may see in your radiology report to communicate these abnormalities include:

  • Lesion: informal term meaning imaging abnormality, which could be normal or concerning
  • Calcifications: tissue hardened by calcium
  • Cysts: fluid-filled sacs
  • Masses: unexpected volume or growth of tissue
  • Nodules: lumps of tissue distinct from their surroundings
  • Tumors: areas of abnormal cell growth

Depending on their source and composition, any of these findings can be benign (non-cancerous) or malignant (cancerous). Some imaging abnormalities can be diagnosed definitively with a CT scan, while other abnormalities would need to be proven using a tissue biopsy.

Is unremarkable good or bad?

When it comes to medical terminology the term “unremarkable” is actually a good thing! It means your CT scan has revealed no significant abnormal findings.

How PocketHealth can help you understand your CT scan report

With PocketHealth, you get fast and easy access to view, share and store your CT scan results, often before your follow-up appointment with your doctor.

If you are unfamiliar with certain medical terms, Report Reader will provide definitions to help make your report easier to understand. Report Reader also spotlights any follow-up recommendations, so you can keep tabs on your own health and always know what’s coming next. Access your records here.

“With Report Reader, I get explanations for words [in my report] that I don’t understand. I can now discuss my health with my family doctor with more confidence and have a better understanding of what is going on.”

– PocketHealth User

Stay on top of your health—and your CT scan results

The more you know about what’s going on in your body, the more informed your conversations will be about any potential diagnosis and ongoing health concerns. Having access to your health records, like your CT scan images and report, puts you in the driver’s seat.

PocketHealth makes that access easy and secure, so you can be confident and in control along every step of your healthcare journey.

How PocketHealth works

Learn more about how to use PocketHealth to securely access and share your CT scan results.

Medical content review provided by Ben Fine, MD. Any health-related information contained in this post is intended to provide general education only and is not medical advice. This should not be used as a substitute for the advice you receive from your healthcare provider.

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