A CT scan uses a narrow X-ray beam operating at a high energy level to capture cross-sectional images of inside organs from many different angles and create a detailed 3D images with advanced computer technology.
While CT provides superior image resolution of bony structures, capturing images of soft tissues requires the use of contrast agents for better visualisation. Taking abdominal examination as an example, contrast agent, which blocks X-ray penetration via soft tissues, can highlight the structural organisation of the intestine.
It is generally used to assess head, neck, breast, abdominal and pelvic regions. With regards to the surveillance of cancer, CT is commonly applicable for monitoring the lesions in thorax, abdominal and pelvic regions.
Below is the information regarding the uses, safety issues, concerns of undergoing a CT examination and its advantages and limitations in comparison with other types of imaging modalities.
CT scan has been used in a wide variety of areas, notably for disease detection including cancer, brain lesions such as stroke and abscess, calculi and inflammation, acute bone injury, cardiovascular disease, as well as lung infection and tuberculosis. Also, it is frequently used to guide biopsy, monitor treatment progress and do planning for surgery or radiation therapy.
Despite the much higher radiation exposure in undergoing a CT examination compared to general X-ray, the risk of developing cancer from radiation is less than one per 2,000 patients with reference to the information provided by NHS. Reducing radiation exposure without comprising the diagnostic quality of images has been made possible with the team’s effort at our centre.
While the impact of radiation emitted from a CT scan on pregnancy might not be significant, doctors may still suggest having other radiation-free imaging examinations such as Ultrasound or MRI if possible. Female patients should check with their doctor before scheduling the examination if they are pregnant or breastfeeding.
Less than 1% of patients who are allergic to the contrast agents might experience mild side effects such as itchy skin, nausea, pain over site of injection, shivering and warm sensation. In severe cases, there might be breathing difficulty and hypotension. For patients with severe kidney failure or undergoing hemodialysis, it is possible to develop nephrogenic systemic fibrosis as an adverse reaction to the contrast agents. Death, which might also occur in serious case, is rarely seen. Patients are advised to drink a large amount of water to allow rapid and efficient excretion of the remaining contrast agents out of the body.
Food intake is not allowed for at least 4 hours and only water is allowed before the procedure for some CT examinations.
Patients should inform us of any diseases such as renal insufficiency, current medications, history of drug allergy or other health conditions such as pregnancy. For patients having seafood or contrast allergy, premedication should be taken at 12 hours and 2 hours before the procedure.
Patients should inform us of the use of Biguanides, and in case of taking metformin or other medication of the same drug class, patients should not take it on the examination day and within 48 hours after contrast injection. Other medications can be taken as usual.
Should there be any issues, radiographers are there to provide as much assistance as possible.
Common tests for diagnosing cancer includes blood test, urine test, imaging test, biopsy and genetic test. Apart from diagnosing cancer, these investigations can also localise the primary site, differentiate the specific cancer cell type, perform cancer staging, identify whether there is metastasis, formulate treatment plan, monitor disease progression and detect recurrence. Below is the information regarding different tests.
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