Computerised Tomography (CT) – Low Dose

About the Examination

A Computerised Tomography (CT) scan, also known as a computerized axial tomography (CAT) scan uses a mixture of x-rays and computer systems to create virtual ‘slices’ of the body without the need for invasive surgery. CT scans produce more detailed images than traditional x-rays and can also be used to form three dimensional pictures of internal sections of the body.

What is a CT scan?

A CT scan involves the use of a large, circular scanner, which spins. The CT bed the patient is lying on moves in and out of the scanner, allowing the CT scanner to take multiple images of the patient’s internal organs and soft tissue.

What part of the Anatomy is examined by a CT scan?

A CT scan can be used to examine every part of the body from the head to the toes including:

Internal organs
Blood vessels
Bones and joints

What Conditions can be Diagnosed by a CT scan?

CT Scans can be used to diagnose of variety of conditions including:

Bone breakages and muscle disorders
Cancers
Blood clots
Heart disease
Infection
Kidney and bladder stones

In addition to diagnosis CT scans can also be used as a guide for tests and treatments as well as a method for monitoring existing conditions.

Why is a CT scan required?

CT scans can be used to diagnose and monitor a number of serious conditions. Doctors also use CT scans as a means to check the precise location of tumours, clots or soft tissue, before surgery or biopsies.

CT scans are also suitable for situations where internal images of the body are needed urgently. For example, to check for internal injuries after a traffic collision.

What are the Risks and Complications of a CT scan?

A CT scan is a relatively low risk procedure as it is non-invasive.

However, during a CT scan patients are exposed to more radiation than in a typical x-ray as multiple images are taken of the body. Although the lowest radiation doses possible are used, there is a risk that patients may develop cancer. The risk is slightly higher in patients under 40 years of age.

You can find out more about the levels and risks of x-rays from the Patient Dose Information Fact Sheet, published by Public Health England.

There is also very minor risk that patients may suffer from a severe reaction to the contrast medium. Most patients who have a reaction develop an itchy rash. Very rarely there can be a severe reaction with:

Low blood pressure
Anaphylactic shock
Cardiac Arrest

Allergic reactions to the x-ray dye are usually mild and can be treated with medication on site. If you have a known contrast reaction, it is important to let the staff know.

What consequences are there if the suspected condition is undiagnosed or untreated?

CT scans are used to detect and diagnose a number of severe conditions, which if left untreated can cause severe or fatal complications.

Early detection and treatment of these conditions can increase the chances of successful treatment and recovery.

About the Equipment

What are the equipment specifications for a CT scan

The following equipment is used during a cardiac CT procedure:

A high speed CT scanner
CT table
Intercom
Monitor
Contrast injector

What are the benefits of a CT scan?

A cardiac CT is a safe, non-invasive procedure with detailed results, which are produced quickly.

Are there alternatives to a CT scan?

Depending on the medical condition and history of the patient, doctors may suggest undergoing an ultrasound or MRI instead of a CT scan.

Preparation for a CT scan

What Special Diet is required Before a CT scan?

You may be instructed to fast for up to four hours before your procedure. Some scans require drinking some oral contrast in the hour before the scan to show up the bowel more clearly.

What should a Patient Tell the Radiographer Before a CT scan?

Patients should alert the radiographer if they are pregnant as there is a risk that the radiation from the CT scan could endanger the baby.

You should also tell the radiographer if you are asthmatic, suffer from kidney problems or have any allergies as these conditions increase the risk of a negative reaction to the contrast medium.

What to bring for a CT scan

Your doctor may ask you to bring any previous scans or x-rays to the procedure, along with any medications you’re currently taking.

What to wear for a CT scan

You will be asked to remove any metallic items, such as jewellery, watches, eyewear and belts, as these items can show up on the CT scans. You should also avoid clothes with zippers or metal buttons.

You may be asked to remove any clothing obstructing the area to be scanned and given a medical gown to wear instead, so you should try and wear something that is comfortable and easy to remove.

How Long will a CT scan take?

The CT scan procedure usually takes between 10-30 minutes to complete.

CT scan Procedure Description

What does a CT scan involve?

During a CT scan the patient will be asked to lay down on a CT table, and a contrast medium is injected into the bloodstream, usually via an intravenous (IV) line connected to your hand or arm.

Detail the specific steps during a CT scan

After being escorted to the procedure room, you will be asked to lie down on the CT table with your head towards the opening of the machine. The radiographer will typically inject the contrast medium, through the IV line, into the back of your hand, or the inside of your elbow.

If your stomach or intestines are being examined you may be required to either swallow or more rarely have the contrast medium inserted via an enema. Most patients find the taste unpleasant, and enemas can result in some discomfort and bloating.

You may also experience the following sensations as the contrast agent moves through the body:

Warmth
Mild burning
A metallic taste or smell
A temporary urge to pass urine

You may also be connected to an electrocardiogram (EKG) machine during the procedure, via small patches placed on your chest. These monitor and record your heart rate.

You will then be told to lie still while the CT scanner spins, moving up and down as it takes images of your body. It is normal for the machine to make a series of whirring and clicking noises as it works.

At various points the specialist may talk to you via an intercom, instructing you to hold your breath or keep still.

Post CT scan Instructions

What are the Recovery Details?

Your radiologist may ask you to stay in the hospital for up to an hour after the CT scan, to ensure that there are no side effects or reactions to the contrast medium.

After the procedure you will usually be able to resume normal activities immediately. The results of the scan will be sent to your doctor, who will discuss them with you during your next appointment.