High Resolution Computerised Tomography Scanning (CT / HRCT Scanning)

CT (computerised tomography) scans are far more detailed than ordinary X-rays. A CT scanner is a special kind of X-ray machine. Instead of sending out a single X-ray through the body as with ordinary X-rays, several beams are sent simultaneously from different angles PIC9. This means the HRCT scan provides far better visualisation of the lungs than standard chest X-rays.

The X-rays from the beams are detected after they have passed through the body and their strength is measured. A computer can use this information to work out the relative density of the tissues examined.

Each set of measurements made by the scanner is, in effect, a cross-section through the body. The computer processes the results, displaying them as a two-dimensional picture shown on a monitor. HRCT images are useful for excluding some very common lung diseases which can cause excessive breathlessness, such as emphysema.

The scanner looks like a large doughnut. During the scan the patient lies on a bed, with the part of the body under examination placed in the opening of the scanner. The bed then moves slowly backwards and forwards to allow the scanner to take pictures of the body, although it does not touch the patient. Sometimes a dye (often referred to as a “contrast medium”) may be injected into the bloodstream prior to the scan. The dye makes certain abnormalities more apparent when the test results are read.

The time the test takes depends on the number of pictures and the different angles taken. The examination does not hurt but as there is little room inside the tunnel, people who suffer from severe claustrophobia sometimes have problems with CT scans. People worried about this should let the doctors and radiographers know. Other people get slightly nervous because of the whirring noise the machine makes while working.

The radiologist looks for any abnormal patterns in lung tissue. If intravenous dye is used, he/she also looks for abnormal filling of the lung vessels, which may help indicate blood clots in the lungs.

As far more X-rays are involved in a CT scan than in ordinary X-rays, doctors do not recommend CT scans without a good medical reason.