CT scan, MRI scan, bone scan and biopsy - here we look at specific tests designed to tell whether or not a cancer is present and what happens during the procedures.

If your GP is concerned with any of the symptoms you have presented, he/she will refer you to hospital to have specific tests.  These are designed to tell whether or not a cancer is present and also to give the doctors as much information as possible.

This data will be useful in designing any subsequent treatment strategy that might be necessary. There are a number of tests that may be used and ultimately these will depend on the location of the suspected cancer.

CT or CAT Scan

What is a CT scan?

A CT (Computerised Tomography) or CAT (Computerised Axial Tomography) scan is a computerised X-ray that differs from an ordinary X-ray. Instead of having just one x-ray beam, several beams are used simultaneously from a number of different angles.  These pass through the body, and are then detected and their strength measured. Beams that have passed through dense organs such as bone are weaker, those that have passed through less dense tissue, stronger. This information is used to work out the relative density of the tissues examined and build up a three-dimensional picture of the inside of your body.

CT scans can also be used for other purposes where it is important to determine the exact location of a tumour. These include guiding biopsies and therapeutic pain procedures - and planning radiotherapy treatments.

Does it hurt?

Having a CT scan is painless and although it uses a small amount of radiation this is extremely unlikely to harm you and certainly not anyone you come into contact with.

What happens?

On the day you have the scan, you will be asked not to eat or drink for at least four hours beforehand. In some cases, you may be given a coloured drink or be injected with a dye. This is to allow particular areas to be seen more clearly on the scan. This may make you feel hot all over for a few minutes but it will soon pass.

The scan itself lasts from 10-30 minutes, depending on the number of pictures to be taken and the different angles required. During this time you will have to lie very still in a horizontal position.

Once the scan is over, you should be able to go home without delay.

MRI scan

What is an MRI scan?

A Magnetic Resonance Imaging scan is similar to a CT scan but uses magnetism instead of x-rays to build up a detailed picture of areas of your body. Radio waves much stronger than the magnetic field of the earth are sent through the body. These disturb the atoms making up the body, causing parts of them, the nuclei, to alter position. As they settle back, they send out radio signals of their own  which are detected and used to build up an image based on their location and strength.

An MRI scan can produce images containing detailed definition of all the tissues, normal and abnormal, in the body.  Pictures can be taken from multiple angles; this is not possible with a CT scan. 
 
Does it hurt?

Having an MRI scan is painless.  However, during the scan you will be spending some time in an enclosed space, so you may feel a little uncomfortable if you are claustrophobic. If this is the case, do let the medical team know beforehand.

What happens?

The scan entails lying very still on a couch inside a long cylinder-shaped chamber for about 30 minutes.  Be aware that the scanning process itself is noisy - but you will be given ear-plugs or head-phones and you can usually take someone into the room to keep you company.

As the chamber contains a powerful magnet, you will be asked to remove any metal belongings such as watches before you enter the room. This is why people who have metal inside their body such as a cardiac monitor, pacemaker or surgical clips cannot have a MRI scan.

Once the scan is over, you should be able to go home without delay.

Ultrasound

What is an ultrasound scan?

An ultrasound scan uses very high frequency sound waves not audible to the human ear.  These are passed through the body using a transmitter or scanner that is normally placed on the skin surface. The pattern of the reflected sound waves or echoes detected is used to create an outline of the organ in question, so is used for soft tissues rather than bony structures.

Ultrasound scans can also be used for other purposes following cancer diagnosis, where it is important to determine the exact location of a tumour. These include guiding biopsies and therapeutic pain procedures - and planning radiotherapy treatments.

Does it hurt?

Having an ultrasound scan is painless but may involve a little discomfort depending on the focus and purpose of the scan.  The scan will be performed by a radiographer with ultrasound experience: a sonographer.

What happens?

Preparations will vary according to the area to be scanned, and may include an enema.  In most cases, in order to obtain a clear image the transmitter must touch the bare skin surface directly, without any air in the way  so a gel is placed on the skin before scanning.  This can be cold, so be prepared!

Once the scan is over, you should be able to go home without delay.

Bone scan

What is a bone scan?

A bone scan uses a tiny amount of radioactive tracer to show up hot spots in bones.  This is an extremely sensitive test and can detect cancer cells before they show up on x-ray.

What happens?

A very small amount of a mildly radioactive liquid is injected into a vein, usually in your arm.  After the injection you will have to wait up to three hours before the scan can be taken so you may want to take a magazine or book with you or a friend to keep you company.

Abnormal bone absorbs more of the radioactive liquid than normal bone, so this shows up on the scan as highlighted areas. The radioactivity levels used in these scans are very low and disappear from the body within a few hours.

Biopsy

To make a conclusive diagnosis, doctors may need to take a number of cells from the problem area and examine them under a microscope. This is called a biopsy, which can be taken in a number of ways.

Fine needle aspiration

In this procedure, the area to be examined is first numbed.  A small piece of the suspected cancer is then removed or aspirated using a very fine needle and a syringe or a special pair of tweezers called biopsy forceps. This is called fine needle aspiration. Depending on the location of the suspected cancer, ultrasound or x-ray images may sometimes be used to guide the doctor accurately to the abnormal area. This procedure does not require stitches, though you are likely to feel a little bruised when it is all over.

Needle core biopsy

Whilst this can be done in the clinic using local anaesthetic, it may also be done while you are asleep under a general anaesthetic and this means you may need to stay overnight in hospital. This way allows time for a prolonged close examination of the area and also enables other biopsies to be taken from any other suspicious areas detected once the examination has begun. It also allows more tissue to be taken if necessary for more tests, by using a larger needle. This is called a needle core biopsy.

Surgical biopsy

Another possibility is that your medical team may decide to remove a larger sample for study.  This requires a small operation and a stay in hospital.

03/06/2009