Can a CT Scan Detect Lung Cancer?

Can a CT Scan Detect Lung Cancer? Discover the Facts Here

If you’re wondering, “can a CT scan detect lung cancer?”, the short answer is yes. A chest CT scan, alongside other diagnostic tests, is often used to diagnose lung cancer. Low dose CT scans of the chest are also used as part of lung cancer screening – which is available on the NHS – for those with a higher risk of developing lung cancer.

Here, we will explore how CT scans work, how to prepare for a one and how they compare to other imaging tests. We will also discuss how they’re used to diagnose lung cancer, as well as their limitations and risks.

How does a CT scan work?

A CT scan (computerised tomography) uses X-rays and a computer to create detailed 3D pictures of your chest and lungs.

A CT scanner has 3 main parts: a patient table, a gantry containing an X-ray generator and an X-ray detector, and a computer.

During your scan, you will lie on a bed that moves slowly through a ring-shaped scanner. The scanner takes multiple X-ray pictures from different angles to create detailed images of the inside of your body that are processed by a computer.

The computer will create a grayscale, 2D cross-section image of your body. As your body is moved up or down through the scanner, more 2D cross-sectional images will be created.

The computer will then pull these images together to form a highly detailed, 3D image of the inside of your body.

Bones appear white on a CT scan, air looks black, and other tissues show up as shades of grey.Areas filled with air, fat or fluid are less dense and absorb fewer X rays – this means that they appear black on CT imaging. Other tissues, such as organs, muscles, tendons and ligaments, appear in varying shades of grey.

CT scans allow your doctor to see changes inside and between tissues so they can identify any abnormal areas. As a result, CT imaging can be useful for diagnosing a variety of lung diseases, including lung cancer.

Lung cancer diagnosis: what to expect

If you have symptoms of lung cancer, it’s important to see your GP as soon as possible. Lung cancer symptoms include:

A persistent cough (ie a cough lasting for over 3 weeks) and/or a cough that continues to get worse
Breathlessness
Coughing up blood
Chest pain or an ache in your chest when breathing or coughing
Fatigue
Repeated chest infections

These symptoms alone do not provide a definitive diagnosis of lung cancer because some of these symptoms can also be caused by other lung conditions. That’s why it’s important to see your GP to find out the exact cause.

Your GP will ask you about your symptoms and medical history. They may also listen to your chest using a stethoscope and ask you to breathe in and out of an instrument called a spirometer. Depending on their findings, they may refer you for a blood test and an X-ray.

A chest X ray is usually recommended first to check lung tissues for growths. Depending on your results, you may then be referred to a respiratory specialist. They will refer you for further imaging tests, which may include a chest CT.

Understanding lung cancer detection with CT scans

A special dye called contrast is usually needed to detect lung cancer during a scan. Contrast medium (dye) improves the clarity of the images created during your scan.

CT scan contrast agents are iodine-based dyes. When used for a lung CTscan, the contrast medium is usually injected into a vein. It flows through blood vessels to organs and tissues. As iodine absorbs high levels of X-rays, any tissues or organs containing iodine appear brighter on a CT.

Lung cancer also appears brighter on a lung CT – a collection of lung cancer cells often appears as a white grey mass. Because chest CT images are higher resolution than chest X-ray images, smaller tumours can be detected more easily for an earlier diagnosis of lung cancer.

Different types of lung cancer can be detected using a chest CT scan. There are two main types of lung cancer: small cell lung cancer and non small cell lung cancer. Non small cell lung cancer is the most common. Your doctor will explain the type and stage if cancer is diagnosed, which helps guide treatment.

In every 100 cases of lung cancer, around 15 are small cell lung cancer and around 85 are non small cell lung cancer. The most common type of non small cell lung cancer is adenocarcinoma.

If your doctors diagnose lung cancer, they'll tell you what type of cancer you have and what stage the cancer has progressed to. The staging system for lung cancer is based on the size of your tumour and whether the cancer has spread to other areas of your body.

For example, if your cancer started in your lungs, it can spread to nearby lymph nodes and then to other organs such as the brain, bones, liver and adrenal glands.

Comparing CT scans to other diagnostic tools

CT vs MRI

MRI stands for magnetic resonance imaging. As with CT, it produces highly detailed 3D images of the inside of your body, but it doesn’t use ionising radiation. This means MRI is safe for pregnant women.

Instead, MRI uses powerful magnets and radiofrequency waves. The MRI machine has a patient table that slides into a tube structure. This tube contains:

Strong magnets that create a magnetic field around the person being scanned
Radiofrequency coils that produce radio waves
Gradient coils that regulate the magnetic field

During MRI scans, you will be asked to lie down on the patient table. The table will be slid into the tube of the machine. When the scan begins, you will hear knocking, clicking and buzzing noises – these are the normal sounds of the machine working. If you find these sounds make you feel anxious, you can listen to music during your scan using headphones provided by your care team.

A magnetic field will be created around you. The magnetic field affects small particles called protons in hydrogen atoms that make up the water molecules in your body. The protons all line up and point in the same direction.

Then, pulses of radio waves will pass painlessly through your body. This makes the protons wobble and go out of alignment. When the radio waves stop, the protons realign, which releases energy as radio signals.

The MRI machine detects these radio signals, which are then turned into 2D grayscale images. Lots of 2D grayscale images of sections of your body are created. These are then processed by a computer into a 3D image that shows tissues inside your body in great detail.

When compared to a CT scan image, MRI scans have higher contrast resolution. This means MRI scans can show the difference between different soft tissues – which appear in different shades of grey – better than CT scan images.

However, CT images have better spatial resolution. This means CT images can separate out 2 points that are very close together better than MRI images.Both MRI and CT scans can detect small tumours early, helping with timely diagnosis and treatment.

CT vs ultrasound

An ultrasound scan is a quicker, more cost-effective scan than a CT. It also doesn’t use ionising radiation and is safe for pregnant women.

An ultrasound scanner is a much smaller piece of equipment than a CT scanner. It includes a handheld ultrasound probe and a computer. The ultrasound probe is moved over the part of your body to be imaged and sends ultrasound waves into your body.

These sound waves are beyond the limit of human hearing. So your ultrasound scan will not make any sounds that you can hear. In just one second, over 1,000 ultrasound waves can be passed into your body and reflected off the tissues inside your body. These reflected sound waves are called echoes.

Ultrasound waves bounce back when they encounter a boundary between 2 tissues or 2 parts of a tissue that are of a different density. Tumours caused by lung cancer can be detected by these reflected sound waves.

The echoes are converted into electrical signals in real-time. They’re processed by a computer into live images of the inside of your body, whereas a CT produces static images of the inside of your body.

Sound waves can be distorted by bone and air, so to create the clearest possible images of the lungs sometimes the ultrasound probe is inserted into the windpipe (trachea). This is usually done under sedation so you are comfortable.

An endobrachial ultrasound scan uses an ultrasound probe attached to a bronchoscope. A bronchoscope is a flexible, thin tube with a camera and light on the end. This allows your doctor to see the inside of your trachea as the bronchoscope is passed down it.

Special instruments can be passed through the bronchoscope to collect a tissue biopsy, that is, a sample of the suspected cancerous cells. This biopsy sample can then be examined in a lab under a microscope to check whether they are normal cells or cancer cells.

CT vs X-ray

Both CT and X rays use ionising radiation. However, the amount of radiation used in an X-ray is much lower. For example, a chest CT uses 6.1 mSv of radiation, while a chest X ray uses 0.1 mSv of radiation. Both levels of radiation are considered low and safe to use.

A chest X ray is a faster imaging test than a CT. It involves standing in front of an X-ray detector, while an X-ray generator sends X rays through your chest area. Some of the X rays are absorbed by your body, while others pass through and are picked up by the X-ray detector.

As with a CT, less dense areas, such as those containing air, appear black as they absorb very low amounts of X rays. Meanwhile, dense tissues, such as bone, appear white as they absorb high amounts of X rays. A growth or tumour may appear as a white grey mass.

The image resolution of a chest X ray is lower than a chest CT image. Consequently, a chest X ray can detect abnormal areas of tissue but cannot determine if it is lung cancer or other lung conditions such as a lung abscess.

So although a chest X ray is often the first test used to investigate symptoms relating to your lung health, if abnormal tissue is found, further diagnostic tests will be needed.

Limitations and risks of CT scans for lung cancer

As with any imaging test, image results alone cannot provide a definitive diagnosis of lung cancer. So although lung CTs can suggest with a high probability whether or not lung cancer is present, tissue samples need to be collected to confirm the imaging results.

A very small number of people may have a mild reaction to the contrast dye, but you’ll be monitored and treated immediately if needed.

If you have a lung CT with a contrast medium, you will be asked to stay at the scanning facility for 30 minutes. You will be closely monitored during this time and if you develop an allergic reaction, you will be treated quickly.

How to prepare for a lung CT scan

If you are having a lung CT with contrast medium, your care team will tell you how long you need to fast in the run-up to your scan. This means not eating any food or drinking anything other than water. Your care team will also let you know if you need to temporarily stop taking certain medications.

Before you have your CT, you will be asked to change into a hospital gown, so it’s a good idea to wear loose, comfortable clothing that you can easily change out of.

If you are feeling anxious about having a CT, let your care team know in advance so they can better support you. You can also take a friend or family member along with you to your scan.

Next steps after a lung cancer CT scan: what to do

At Vista Health, we aim to deliver a detailed report of your chest CT scan results in 3 working days. Your imaging test results will be interpreted by one of our Consultant Radiologists.

Your results can be sent to your NHS GP or you can book a consultation with one of our experienced Vista Health GPs. They will discuss what your results mean and next steps, including specialist referrals, more tests you may need and treatment options.

If your scan shows anything unusual, your doctor may recommend further tests to confirm a diagnosis, which could include blood tests, tissue samples, or additional imaging.

At the point when you receive a definitive diagnosis of lung cancer, a doctor specialising in cancer treatment (an oncologist) will discuss your cancer treatment options in detail.

This may include treatment to remove lung cancer ie surgery, as well as radiation therapy, chemotherapy and targeted treatments (ie targeted therapy drugs).

Get clarity on your lung health today

If you are concerned about your lung health or have a family history of lung diseases, a private CT scan can give you clarity and peace of mind. At Vista Health, you can book a scan at one of our nationwide clinics and get expert results quickly.