A CT scan takes a series of x-rays which builds up a three-dimensional picture of the inside of the body. The scan is painless and takes from 10–30 minutes. CT scans use a small amount of radiation, which is very unlikely to harm you and won’t harm anyone you come into contact with.

You will be asked not to eat for at least four hours before the scan.

Before the CT scan you may be given a drink or injection of a dye (contrast) which helps the doctor to get clearer pictures from the scan. For a few minutes, the dye may make you feel warm all over. If you’re allergic to iodine or have asthma you could have a more serious reaction to the injection, so it’s important to let your doctor know beforehand. It is usually still possible to have the injection, but you will need to have steroid treatment on the day before, and the day of, the injection.

You may be asked to drink large amounts of water just before having the scan. This slightly stretches the stomach and gives a better picture of it. During the scan you may be asked to lie in different positions, such as on your back and front so that the doctor can see different views of your stomach.

You will probably be able to go home as soon as the scan is over.

This test may be used to measure the size and position of a tumour. It’s done in the hospital scanning department, is painless and only takes a few minutes.

Once you’re lying comfortably on your back, a gel is spread onto your tummy area (abdomen). A small device which produces sound waves is then passed over the area. The sound waves make up a picture of the stomach and liver, which can be seen on a computer screen.

This test may occasionally be used to check for signs that cancer has spread outside the stomach. A PET scan uses low-dose radioactive glucose (a type of sugar) to measure the activity of cells in different parts of the body. A very small amount of the mildly radioactive substance is injected into a vein, usually in your arm. Tumours normally absorb more of the glucose and the radioactivity shows up on the scan.

After the injection is given you may be asked to lie in a dark room with your eyes closed. You will then be taken to the scanning room and asked to lie on a couch with the scanning ring around you. The dose of radiation you receive is no more than a normal x-ray.

PET scans aren’t available in all hospitals, and you may have to travel to a hospital some distance away from your home to have it.

This test allows the doctor to look inside the upper part of the abdomen (tummy area). It’s used to help plan the type of stomach operation that is most suited to you. It involves a small operation done under a general anaesthetic and will mean a short stay in hospital.

The doctor makes a small cut (about 2cm) in the skin and muscle near the tummy button (navel) and carefully inserts a thin, flexible fibre-optic tube (laparoscope) into your abdomen. The laparascope allows the doctor to look at the outside of the stomach and at organs close by. They may take samples of tissue (biopsies) to be examined under the microscope.

After a laparoscopy you’ll have one or two stitches in your abdomen where the cut was made. You may feel sore for a few days afterwards but you should be able to get up as soon as the effects of the anaesthetic have worn off.

You may have blood samples taken to test for the levels of particular proteins in your blood. These proteins, called CEA and CA 19-9, are sometimes found at higher levels in the blood of people with stomach cancer. Because of this they are called cancer markers (or tumour markers).

If these tests show you have a raised level of a cancer marker in your blood the doctor may repeat them from time to time during and after your treatment. This might be done to check how well your treatment is working and as part of your follow up after treatment.