How to Read a CT Scan Report: Decoding Common 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. As for CT scan results, medical reports are full of complex terminology that can be difficult to understand. This article will clarify some of the medical terms and abbreviations you might encounter in your CT scan report so you can be more prepared for conversations with your healthcare team.

While this guide provides helpful information, your doctor will give the official interpretation of your CT scan results during a follow-up appointment or phone call. However, if you’d like early access to your results, PocketHealth offers secure, instant access to your report when it is available. This allows you to review the findings prior to your follow-up appointment and prepare any questions for your follow-up appointment.

 

 

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 is 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:

• An intravenous (IV) contrast agent is injected into your body: This highlights areas of increased blood flow, like blood vessels or organs (e.g. liver, kidneys or spleen).
• An oral contrast agent is swallowed: This helps CT scans better identify areas of the esophagus, stomach and intestines.
• A rectal contrast agent is inserted in the rectum: This improves 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 include findings such as cysts, tumors or benign growths
• 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.

 

Other CT scan factors

Here are other aspects of the scan that are commonly reflected on the report:

• Technique: This is generally a description of how the scan was performed, such as whether contrast was used or not.
• Patient history: This could include the patient’s medical history, known conditions, symptoms and other relevant health information.
• Comparison: If previous CT scans were performed, the radiologist may compare any changes, if present.
• Findings: Descriptions such as normal/abnormal, details on irregularities or other relevant information will be shown here.
• Impressions: This is a general summary of the most important findings (if there are any). There may also be instructions for repeat imaging, additional testing or other recommendations.

 

Understanding your results

Turnaround times for results can vary widely depending on the facility and your doctor’s availability. Often, patients wait a week or more and receive their results during a follow-up appointment. With PocketHealth, you don’t have to wait as long—your results are available securely as soon as the report is written and uploaded, allowing you to review them often before your follow-up visit.

When you do receive your results, it’s common to find medical terminology somewhat confusing. Report Reader helps you to better understand your report by offering clear, straightforward definitions for medical terms—simply tap or click on any underlined words to reveal their meaning.

 

 

Frequently asked questions

Here are some common questions regarding CT scans.

What are some advantages of CT scans compared to other types of imaging?

One of the biggest strengths of CT scans is how fast they can be performed, making them ideal for emergency room settings. For example, if emergency surgery is needed, the surgeon can quickly obtain precise information about the region to be operated on. Outside of the ER, CT scans are particularly helpful for patients who have difficulty or discomfort holding still for long periods, such as during an MRI. CT scans are also a useful option for patients with metallic implants, who may not be ideal candidates for an MRI, as it uses magnetic waves.

Are there any risks to having a CT scan?

The risks of CT scans are minimal, and the benefits usually outweigh any potential negatives. However, it’s important to be aware of the following:

• Slight radiation exposure: This is generally considered within safe levels, especially if the imaging is needed only occasionally. Patients who require regular or repeated medical imaging are more likely to receive a different type of scan, such as an ultrasound or MRI, rather than repeated CT scans.
• Allergy to contrast agent: Although rare, some patients may experience an allergic reaction to the contrast agent. If a patient feels unwell after receiving it, they should inform the technician immediately. Fortunately, this is uncommon.
• Possible kidney issues: Since the contrast agent can affect the kidneys, patients with pre-existing kidney problems should inform their healthcare provider in advance. In these cases, the scan can be performed without the contrast dye.

Can CT scans detect a heart attack?

CT scans don’t directly detect a heart attack, but they provide insight into the overall health of the heart and surrounding arteries, including whether an artery is clogged or if there is buildup. This helps physicians assess a patient’s risk for a heart attack, allowing them to take preventive measures and provide appropriate treatments.

Can a CT scan detect cancer?

Most tumors and growths are benign, but CT scans are useful for detecting these abnormalities, including identifying masses that may be suspicious for cancer. However, an official cancer diagnosis typically requires a biopsy and pathology review of the tissue sample for confirmation. The scan can help guide the doctor during the biopsy by pinpointing the exact location of the growth.

 

Take control of your health journey

PocketHealth makes it simple to keep track of your CT scan reports and other medical results. All of your vital imaging is in one secure location and can be accessed online anytime. If needed, reports can also be easily shared with other physicians in your care team. When used in conjunction with your medical provider’s professional advice, it is a powerful tool for organizing and understanding your imaging results and your health. For Dave, a pancreatic cancer patient, having access to all his medical scans allowed him to see that his tumor was actually shrinking, providing him with peace of mind.

Another tool for your health is MyCare Navigator, which provides personalized insights to your health and identifies any recommended follow-up steps. This feature can also generate individualized questions to ask your doctor based on the findings in your report, ensuring you make the most of your consultation.

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.