To examine disorders of the organs in the chest – the lungs, pleural membrane, limitedly the heart, the larger veins and oesophagus. CT is used to show diffused or circumscribed inflammatory pulmonary diseases, tumors, pulmonary embolism, fluid buildup in the thoracic cavity and lymph nodes. The CT may also be used for lung screening in which case, no contrast is used and the dosage is lower.
No special preparation is required, only that you must come on an empty stomach on the day of your CT scan. If intravenous contrast material is to be administered, certain diabetes medicines should not be taken, thus, it is important that you consult with your doctor beforehand. In any event, it is best to come prepared for contrast material.
A CT series of images is prepared one with and one without contrast material, while you are holding your breath according to various protocols.
If you cannot hold your breath for 20-30 seconds, then such artefacts will appear on the image that will cause evaluation to be impossible. Allergy to contrast material precludes such imaging in certain instances (i.e., embolia), but, we can gain much information even then, without contrast.