CT scanners use radiation to generate a very detailed three-dimensional picture to aid diagnosis and treatment. We are all exposed to natural background radiation every day of our lives. This comes from our environment, the air we breathe, the food we eat and even from outer space (cosmic rays).

Each scan obtained gives us a small additional dose of radiation; the level of dose varies with different types of examinations. Generally, the amount of radiation you will receive during your examination is the equivalent of between a few days and a few years of exposure to natural ‘background radiation’ that you would receive from the environment.

CT scans have doses that are slightly higher and can be equivalent to 1 to 5 years’ background radiation depending on what area of the body is being scanned.

All examination doses are kept as low as reasonably practicable to ensure that images of a high diagnostic quality are obtained without exceeding accepted dose levels.

Preparation instructions

You may be asked to change into a hospital gown depending on the CT examination being performed. The reason we ask this is to ensure no blood or other products stain your own clothes during your scan. We also need to ensure there is no metal present (zips, poppers or bra wires) on your clothes. If you would like to remain in your own clothes just speak with staff when attending for your appointment.

Please remove all jewellery (earrings, necklaces etc) prior to attending for your appointment.

Depending on the CT examination you will be provided with specific instructions if you need to follow a special diet, have a full bladder or to drink specialised drinks prior to your scan.

Unless otherwise stated by appointments or the information leaflet provided, please drink, eat and take medication as normal.

Prior to your appointment

Please contact Radiology Hub on 01324 566242 if you:

• Are pregnant or may be pregnant
• Have poorly controlled asthma
• Have issues with your liver or kidneys
• Have an untreated overactive thyroid
• Are diabetic on metformin
• Are taking metformin for Poly Cystic Ovaries or for weight loss
• Have any allergies or have had an allergic reaction to a dye called contrast medium which have required medical intervention
• If you have a PICC line in place

What will happen at my examination?

Depending on why you are having a CT scan, you may be given an iodine-based injection called contrast medium or “x-ray dye”. This injection is used to make the images clearer during the CT scan and aid with diagnosis.

The injection is not suitable for all patients, and the Radiographer and Radiologist will decide if it is appropriate for you. Please let us know if you have had a previous allergic reaction to a contrast agent.

When receiving contrast, it is very normal to feel:

• Hot and flushed
• Like you have a metallic taste in your mouth
• Like you are passing urine – you are not.

All these sensations usually pass quickly.

To allow us to administer the contrast injection we will place a cannula (soft, hollow, plastic tube) into a vein in your arm.

You will lie on the table as instructed by the Radiographer and be asked to remain still to ensure the images are not blurred. The CT scanner may give you instructions to breathe in, out or hold your breath during parts of the scan.

Side Effects from contrast medium

Allergic reactions to Iodine contrast agents are uncommon but do occur. Most occur during the injection or within the first 30 minutes following administration; however, some can occur up to several days after.

Most common side effects include:

Nausea, vomiting, headache, skin rashes or hives. These are all short acting and resolve quickly.

Serious allergic reactions have been rarely reported.

Please seek immediate medical attention if you have any of the following:

• Swelling of the face, mouth, hands, feet or throat
• Coughing, wheezing or sneezing
• Difficulty in breathing and/or swallowing

Rarely the contrast can cause problems with your kidneys. You can minimise this risk by drinking plenty of fluid (water or juice) following your scan – unless you have been told by your doctor to reduce your fluid intake. If you notice a reduction in your urine output over the days following your scan, please seek advice from your G.P

Contrast Extravasation

Occasionally the injection may leak out of from the vein to the tissues under the skin. This is called an extravasation.

If this has happened, you may experience a stinging sensation where the contrast has gone into the tissue and it can be painful.

Sometimes you may need a further injection of contrast, but this will be discussed with you.

The Radiographer will massage and elevate your arm and will apply a cold compress to the area.

Depending on the severity of the extravasation we may keep you up to an hour in the department to monitor the swelling.

Prior to you leaving the department you will be seen by either the Radiographer or Radiologist and be provided with a leaflet and G.P letter to inform them of this extravasation.

Any pain or swelling will generally resolve over the next day or so.

You must seek medical advice (via your G.P, NHS 111 or an Emergency Department) if any of the following occur:

• Pain persisting for more than 4 hours, or if the pain gets progressively worse
• Change in sensation or temperature lower down the affected limb ie numbness, tingling or coldness
• A skin blister or wound appearing

After the CT scan

If you received an injection of x-ray dye, you will be asked to remain in the department, with the cannula in your arm for either 15 or 30 minutes. This is to ensure you suffer no aftereffects from the contrast injection.

If you received an injection of Buscopan you are not allowed to drive one hour after injection. In the coming days (up to 48 hours post scan) if you develop eye pain, redness around the eye or vision loss you must seek advice from your G.P, NHS 11 or attend the Emergency Department and state you have had an intravenous injection of Buscopan.

If you are an outpatient, you will be able to go home after your scan.

Results

The images from your scan are sent to a Radiologist for reporting. Some scans may be reported by an external Radiology Reporting company. Your confidential information is kept secure.

Results are not usually provided on the day of your scan. The healthcare professional who referred you for the scan will be sent the results. Your G.P will also be provided with these results.

Sometimes you will need further imaging or tests depending on why you are getting a CT scan.