Chest CT Scan

A CT scan may be contraindicated in certain conditions. You must inform the doctor beforehand if:

• You are or suspect that you may be pregnant as exposure to radiation can cause birth defects. A CT scan is generally avoided during pregnancy.
• You are breastfeeding. If you are being given contrast dye during the procedure, it may pass into breast milk.
• You have had an allergic reaction to contrast dye previously.
• You have kidney disease or any other health issues.

Children are more sensitive to radiation; therefore, a CT scan should be done on children only if it is absolutely necessary for diagnosis.

You may be asked to get a CT scan of the chest if the doctor wants to evaluate for any of the following:

• Infection or inflammation
• Unexplained chest pain
• Shortness of breath, cough and fever
• Blockages in chest
• Internal injuries or bleeding inside the chest
• Tumours and other lesions
• Planning radiation treatment or assessing response to treatment
• Diagnosing and evaluating lung disorders such as pneumonia

A chest CT scan may also be ordered if the doctor wants to examine any abnormalities detected during a normal chest x-ray more closely.

In a person diagnosed with a tumour, the test can help to check the spread of the tumour or its response to treatment.

It may also be used to evaluate any chest abnormalities found during examinations such as a fetal ultrasound.

A contrast CT scan of the chest is generally not needed except in cases where your doctor needs to evaluate some blood vessels in your chest or perform a CT angiogram. In this scan, an iodine-based contrast dye is injected into the vein before obtaining CT images.

You should inform the doctor about the following before your CT scan:

• Any previous allergic reactions to contrast dye
• Body piercings in the chest or abdominal region
• Allergy to iodine or shellfish
• Any medications that you take routinely

If the doctor feels it is necessary to perform the test using a contrast dye, the following precautions need to be taken:

• You will be asked to sign a consent form.
• You may also be asked to fast for a few hours before the test, your doctor will tell you the exact duration.
• If you take medicines such as metformin (for diabetes), you will be asked to stop taking it for 48 hours after receiving the contrast dye.
• If you are breastfeeding, the doctor may ask you to pump and save breast milk to be used after the exam.

The test will be done in the following manner:

• You will be asked to remove any clothing or jewellery to prevent them from interfering with the test and a technician will give you a hospital gown to wear.
• In case your doctor needs to use a contrast dye, they’ll attach an intravenous (IV) line to your arm.
• After this, you will be made to lie down on a scanning table with your arms positioned above your head. Pillows or straps may be used to help keep you in place for the duration of the scan.
• The table will move into a larger circular opening. You will be able to see the technologist through a window in the machine and communicate with them through a call button as needed. The technologist will be able to speak to you through a speaker in the machine.
• The x-rays will be absorbed by the body tissues and images will be produced on a screen via a computer.
• Usually, the first set of images are taken without the dye and for the second scan, your doctor will give you the contrast dye through the IV line in your arm or, in some cases, the dye is given orally as a liquid.
• Inform your doctor if you feel any discomfort or symptoms such as palpitations, breathing difficulties or sweating during the test.
• If an IV line is used, it will be removed after the scan.

The test is usually completed in 15 to 30 minutes.

While the test is non-invasive and painless, some may find it slightly uncomfortable to be inside the scanning machine as it will be an enclosed space. It is recommended to talk to your doctor if you feel nervous in enclosed spaces so they may make you more comfortable.

If you have been injected with a contrast dye you could experience:

• A salty or metallic taste in the mouth
• Headache
• Nausea or vomiting
• Flushing sensation
• Constipation or diarrhea
• Redness or itching at the site of needle insertion

However, these should subside quickly.

The images of your CT scan will be interpreted by the radiologist to obtain the results.

Abnormalities that can be detected during a CT scan of the chest include:

• Benign or malignant tumours
• Chronic lung disease
• Blockage
• Injuries or internal bleeding
• Infections such as tuberculosis
• Pneumonia
• Cystic fibrosis
• Inflammatory diseases of the pleura (the covering of the lungs)
• Congenital abnormalities

A CT scan has several benefits, such as:

• It is easily accessible and cost-effective.
• It is quick. It can show internal injuries and bleeding in emergency cases, thus allowing immediate treatment that can save a person’s life.
• It is non-invasive and painless.
• Images of the bones, soft tissues and blood vessels can be obtained all at the same time.
• It provides more detailed images as compared to traditional X-ray imaging.
• It can be used as a tool for some minor invasive procedures such as needle biopsy or aspiration necessary for an accurate diagnosis.

The risks associated with a chest CT scan include:

• Allergic reaction to the contrast dye
• Slight discomfort when the needle is being inserted

You may have to wait for a while after the test for the technician to ensure that the images obtained are clear. After that, you can return to your normal activities. 

If you have received a contrast dye for the test, you will be asked to drink 6 to 8 glasses of water to flush out the dye from your body.

Follow-up exams may be needed after a CT scan of the chest, in order to evaluate the status of the abnormality, if any. A follow-up may also be useful in determining if a particular treatment is working effectively.

Other tests that may be ordered along with a chest CT scan include:

• Lung biopsy
• Chest ultrasound
• Lung scan
• Pulmonary function tests
• Chest x-ray
• Positron emission tomography (PET) scan

In most cases, a non-contrast CT scan of the chest will do. However, a contrast CT scan of the chest may be ordered to look for issues in blood vessels or if the doctor needs to do an angiography of the chest.

Contrast CT scan of the chest is avoided in patients who are allergic to the contrast dye, though not many people are allergic to the dye. Also, if you are breastfeeding and have a contrast CT scan of the chest, you may be asked to avoid feeding your baby for a while after the test.

Doctors usually suggest fasting a few hours before a contrast CT scan of the chest while no fasting is required before a non-contrast chest CT scan.

When the contrast dye is injected, you may feel a metallic taste in your mouth and may feel lightheaded or nauseated. Also, some people get diarrhea or constipation due to the contrast dye.

After the test, you’ll have to drink at least 6 to 8  glasses of water a day to make sure the dye flushes out of your system, while nothing needs to be done after a normal CT scan of the chest.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.