Preparation for CT
Before you go in for a CT scan, it’s important to be sure that a CT scan is the best test to confirm or rule out the condition you suspect. If you are not sure, contact a radiologist and ask for their advice, especially before ordering a CT scan in a child or young person because of their greater radiosensitivity. Other techniques may be more appropriate in these patients.
It is important to rule out early pregnancy in a woman of childbearing age, as this is usually an absolute contraindication for CT.
We recommend performing serum creatinine, to assess renal function, if the situation requires the administration of the contrast substance.
- People who have a history of allergy to iodinated contrast material
- Pregnant women
- Chronic renal failure
Cardiac CT angiography
It is an increasingly common medical imaging exam. This is primarily due to its excellent negative predictive value in ruling out coronary artery disease. However, the image resolution and therefore the diagnostic result is limited by the patient’s heart rate and rhythm. Adequate patient preparation is essential to obtain a diagnostic result.
Preparation for CT angio
Take all regular medications on the day of the exam, especially blood pressure medications, except for oral antidiabetics that must be stopped on the day of the exam or for another 24/48 hours after the investigation.
It is recommended that you do not consume caffeine-based products on the day of the exam, as they may interfere with efforts to lower your heart rate before the exam. These products would be: coffee, tea, energy drinks, energy pills and diet pills.
For CT angio investigation it is necessary to perform serum creatinine. It is also necessary for patients to consume fluids before and after administration of the contrast material for renal protection.
A target heart rate for CT angio is 65 bpm or less. Beta-blocker drugs are considered first-line for achieving short-term heart rate reduction. These drugs can be used orally, intravenously, or both. The most common approach uses oral metoprolol with doses based on resting heart rate, ranging from 25 mg to 50 mg, given 30 minutes/1 hour before the scan.
If premedication is considered safe (consult a cardiologist) then a possible regimen would be 50mg metoprolol by mouth 12 hours before the scan and another 25-50mg metoprolol by mouth 30 minutes/1 hour apart before conducting the investigation.
CT angio indications:
- non-invasive evaluation of abnormalities of the coronary arteries and other thoracic vessels
- symptomatic patients with low/moderate probability of coronary artery disease
- Normal or uninterpretable ECG
- Normal or equivocal cardiac biomarkers
- Non-acute symptomatic patients with moderate risk and no known cardiac disease
- Low-risk, non-acute symptomatic patients without known heart disease (if patient cannot exercise or stress test)
- evaluation of the patency of a coronary bypass graft
- new onset heart failure
- no history of coronary heart disease, low/intermediate probability
- decrease in ejection fraction
- preoperative evaluation of coronary arteries before non-coronary cardiac surgery
- Discordant ECGs
- new or worsening symptoms with past normal stress imaging studies
- preoperative assessment for transcatheter aortic valve implantation (TAVI/TAVR)
What regions can we evaluate at CT?
- Cerebral – evaluates the anatomy of the cerebral parenchyma, being used in headaches, dizziness, evaluation of the vascular system in case of ischemic vascular accidents, bleeding due to trauma or ruptured aneurysms, and in brain tumors.
- The neck (cervical region) – we can evaluate inflammatory or infectious processes, neoplasms at the level of the pharynx, larynx and esophagus; response and follow-up to oncological therapy, vascular malformations, thyroid pathology, congenital anomalies;
- Spine – for the evaluation of fractures, congenital anomalies, changes in vertebral statics (scoliosis), detection of tumors or metastases from different types of organs;
- Cardiac – cardiac or coronary anatomy, to detect or diagnose coronary artery disease, to assess the patency of coronary bypass grafts or implanted coronary stents, or to assess cardiac volume and function (including ejection fraction).
- Thorax – is used for the detection of lung infections, tumor formations (pulmonary, mediastinal, pleural), pleural or pericardial fluid, airways, rib cage and vascular anomalies;
- Abdomen and pelvis – infections such as appendicitis, pyelonephritis or infected fluid collections (abscesses), inflammatory bowel diseases (ulcerative colitis or Crohn’s disease), pancreatitis or liver cirrhosis, tumors in various organs (liver, kidney, pancreas, ovary, bladder, intestine ), stones (biliary, renal, urinary bladder), aneurysms (aortic, iliac, renal) and monitoring the treatment response of oncology patients;
- Angiography – evaluation of the vascular system from the level of the whole body, for the detection of atheroma plaques, the degree of stenosis, aneurysms and vascular malformations.
- Osteoarticular system – for the detection of fractures, tumor formations and joint inflammatory changes;