Computed tomography (CT-Scan) emits rotary X-rays around the patient while the table moves in the transmitter ring. The CT-Scan acquires several images and makes coronal and sagittal reconstructions, which add anatomical and diagnostic information. There are many indications for CT-Scan. This exam allows the investigation of the brain, lumbar spine, facial bones, sinus, neck / ENT, thorax, abdomen, pelvis, musculoskeletal, and circulatory system (angio-CT of carotids, the Circle of Willis, aneurysm, aorta and pulmonary angiography, and looking for pulmonary embolism). CT-scan also allows the evaluation of the maxillary prior to dental implants and allows virtual colonoscopy, indicated when looking for polyps and colorectal cancer screening.
Virtual colonoscopy by dedicated CT-scan study is a non-invasive exam (with prior digestive preparation), which allows colonic endoluminal polyps search, precursor of colorectal cancer. Its detection rate is equivalent to that of the optical colonoscopy, with a rate of sensitivity and specificity of approximately 92%. This is a screening test recommended for the general population beginning at the age of 50 years old, or 10 years prior to the age of colorectal cancer diagnosed in a first degree relative.
The great advantage of abdominal or abdominal-pelvic CT-Scan is its ability to assess simultaneously, in a single examination, all organs, including the digestive system, which is very useful in the investigation of an abdominal pain of unclear origin. For example, in a case of pain in the right iliac fossa, CT scans could identify appendicitis, ileitis, obstructive urolithiasis, mesenteric adenitis, or ovarian pathology. CT-Scan is also useful in staging of neoplasm and to assess metastatic damages (lymphadenopathy, carcinomatosis and visceral metastasis) in one examination.
Evaluation of hepatic, splenic, renal and pancreatic parenchyma requires iodinated contrast injection to optimize the detection of lesions or to characterize them in order to know their nature; abscesses, primary or secondary neoplasm, pancreatitis and its complications. Two contraindications must be excluded: allergy to iodine and a decrease of renal function. In the case of severe allergy to iodine, possible alternatives include ultrasound or magnetic resonance, depending on the risk / benefit. As for the abnormal renal function, iodine contrast will not be injected if the glomerular filtration rate (GFR) is <30 ml / min / 1.73m2. Between 40 and 55 ml / min, a hydration protocol before and after the examination will reduce the risks. The risk / benefit ratio must always be considered.