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Evidence‐based approaches

Rationale

Multi‐slice CT has an excellent image resolution and is used for diagnosis, staging and monitoring treatment as well as being a research tool. The scan produces detailed images of the structures within the body. Soft tissues, bone and other anatomy (such as the lungs) are all seen well on CT scans. Patients can be given an intravenous iodine‐containing contrast medium, which perfuses the body tissues and enhances the images (Husband and Reznek [102], Pagana and Pagana [177]).
A CT scan uses radiation, but protocols are optimized to give the best image with the lowest dose. Additionally, the number of body areas scanned and the intervals between scans are closely monitored in accordance with IR(ME)R ([107]) regulations.

Indications

CT can image all parts of the body and is used for:
  • diagnosis
  • pre‐treatment cancer staging
  • interval scans to monitor treatment
  • follow‐up post‐treatment
  • diagnosis and assessment of complications:
    • bowel obstructions and perforation
    • pulmonary embolism
    • stroke and cerebral bleeds
  • perfusion CT
  • guidance during procedures such as biopsies (Chernecky and Berger [32], Keogh [114]).
CT scans (Table 13.14) can also be used to identify and quantify various conditions.
Table 13.14  Common CT scans
Scan areaPotential findings
Brain/head
Tumours
Infarction
Bleeding
Haematoma
Degenerative abnormalities such as multiple sclerosis and Alzheimer's disease
Chest
Chest wall: fracture of ribs or thoracic spine, tumour
Diaphragm: hernia
Heart: pericarditis, pericardial effusion
Lungs: tumours, pneumonia, pleural effusion, tuberculosis
Mediastinum: enlarged lymph nodes
Abdomen and pelvis
Adrenal gland: cancer, adenoma, haemorrhage
Gallbladder and biliary system: gallstones, tumours
Gastrointestinal system: appendicitis, inflammatory bowel disease, perforation, tumours, diverticulitis
Kidneys: calculi, cysts, obstruction, tumours
Liver: abscess, bile duct dilation, tumours
Pancreas: bleeding, inflammation, tumours, pseudocysts
Peritoneum: abscess, ascites
Prostate: tumours
Retroperitoneum: lymphadenopathy, abdominal aneurism, tumours
Spleen: laceration, haematoma, tumours, thrombus (venous)
Uterus, ovaries and fallopian tubes: cysts, fibroids, infection, tumours, abscess
Full body
All of the above
Obstructions
Tumours
Fluid collection
Bleeding
Foreign objects
Inflammation or infection
Source: Adapted from Keogh ([114]), Pagana and Pagana ([177]).

Contraindications

CT is contraindicated in the following circumstances:
  • pregnancy: CT is not recommended unless the clinical benefit outweighs the radiation risk
  • patient has poor renal function (or patients having iodine therapy may have CT without intravenous contrast)
  • patient is allergic to iodine or shellfish
  • patient had a previous CT within a short timeframe (unless the new CT is clinically urgent)
  • patient is unable to lie down in order to pass through the machine (Royal College of Radiologists [211]).
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