computed tomography (CT)

We offer the latest up-to-the-minute CT imaging for all body areas. Our high quality images provide the best possible means for our clinicians to reach a diagnosis, and to plan and to monitor a patient's treatment. Our commitment is to patient care. In 2006 a clinical audit of patient care revealed that over 95% of our patients were satisfied or very satisfied with our CT service.

Our latest CT scanner, a Siemens Somatom Sensation 16, is capable of high quality imaging at very short scanning times

Our CT scanner uses x-rays to create cross-sectional images through the body enabling structures inside the body to be shown up much more clearly than on conventional plain x-ray images.

 

How the abdomen appears during a CT scan in the coronal plane

The images can be displayed in multiple planes and can be combined to produce a 3 dimensional display. The scanner can image all parts of the body including the internal organs, bones, vascular structures, and brain. There are a huge range of potential uses such as diagnosis and staging of cancers, assessment of vascular diseases, and detection of a stroke or bleeding in the brain.

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3D image of a feet generated from the CT scan images

At the centre we have a Siemens Sensation 16 multi-slice scanner with up to date technology such as dose reduction software that allows us to image large areas of the body in just a few seconds at lower X-ray doses than previous CT scanners. We follow IRMER guidelines to ensure patient radiation doses are the lowest possible without compromising image quality.

This scanner allows us to perform a range of complex examinations, and we are able to offer a range of specialized imaging procedures for all clinical specialities. These include specialist gastrointestinal imaging such as CT virtual colonoscopy to detect polyps and tumours of the large bowel; specialist vascular imaging such as CT angiography e.g. to detect both narrowing and dilatation (aneurysms) of the arteries, and to detect clots in the lungs (pulmonary emboli); specialist orthopaedic imaging including 3D imaging for surgical planning; specialist ENT imaging for example for sinus disease; and dental imaging for planning dental treatment including implants.

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We provide imaging for patients with a variety of conditions including cancer patients at the Mount Vernon Cancer Centre, and undertake imaging for a large number of clinical drug trials. We have an active CT research programme and are one of the major institutions worldwide for CT perfusion imaging research. This CT technique allows us to measure the blood supply of tumours; this is used to assess tumour response to anti-cancer treatments for example.

Perfusion CT imaging: The blood flow of the liver is increased due to the presence of tumour deposits

We have installed the latest 64 detector CT scanner, reflecting the Centre's continuing commitment to providing state of the art imaging to patients

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Preparation for a CT scan and CT procedure

The instructions on how to prepare for the CT scan are clearly described in the appointment letter. There is a telephone number for any queries about the scan, scan preparation, cancellations and changes of appointment.

All medication can be taken as normal apart from metformin. Diabetic patients taking metformin have to stop the taking the tablets on the day of the scan and the day following. All diabetic patients are asked to contact the centre prior to the scan.

For some scans of the body, food must not be eaten for 4 hours prior to the scan Patient undergoing CT virtual colonoscopy (also known as CT pneumocolon or CT colonography) have a more complicated preparation. This involves following a special diet for 2 days prior to the procedure and taking a laxative.

For examinations of the abdomen and pelvis, patients will be asked to drink up to a litre of special CT contrast liquid or water during the hour prior to the scan. This helps to identify the stomach and bowel on the CT images.

Just before the scan removal of clothing may be necessary if metallic zips or fasteners are present as these can affect the quality of the scan images. Disposable dressing gowns are supplied by the centre. For examinations of the head earrings, hairclips, glasses etc need to be removed.

The total CT examination should take no more than 10-15 minutes. The radiographer will perform the procedure. A careful explanation of the procedure is always given. Patients are asked to lie down on the couch. The scanner gantry has a large opening (see picture). The patient passes through the opening as the scans are performed. Each scan lasts for only a few seconds.

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Risks from a CT scan

CT is considered a safe examination however there are small risks from radiation and from the use of intravenous contrast media.

Radiation Dose

CT scanning does involve X-rays, and so has the usual risks associated with ionising radiation. Female patients who are or might be pregnant must inform a member of staff in advance. The amount of radiation is more than is used for an ordinary X-ray of the chest or body, and is equal to the natural radiation we all receive from the atmosphere over a period of approximately 3 years. This adds very slightly to the risk of, for example, developing a cancer. However, as one in three of us will develop a cancer at some stage during our lives, the added risk is very small, and also the risks from missing a serious disorder by not having a CT scan are considerably greater.

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Pregnancy

All women of childbearing age should only have a CT scan of the abdomen and pelvis during the first 10 days of their menstrual cycle. Pregnant women should not have a CT scan especially during the first trimester (first 3 months of pregnancy). Sometimes a CT scan is absolutely necessary and then we take additional protective measures. There are imaging techniques that can be useful as an alternative to CT for pregnant women.

Intravenous contrast media

In some cases CT contrast media, containing iodine may be injected into a vein in the arm or hand. It is used to make specific organs, blood vessels or tissue types show up more clearly on the CT images. During the injection common side effects may occur such as a warm flushed feeling over the body or a metallic taste in the mouth. These sensations last for less than a minute.

Mild reactions such as nausea, vomiting or hives may also occur, but serious allergic reactions are very rare. Staff working in the centre are trained to manage any allergic reactions to contrast media if they arise. Patients are asked if they have a history of asthma, allergies, diabetes, heart or kidney problems prior to being given intra-venous contrast media.

For useful patient information guides on CT scanning try the following links
The Royal College of Radiologists
Impact - the UK's CT scanner evaluation centre