What Does a CT Scan Involve?
A CT (Computed Tomography) scan is an imaging technique that uses X-rays to create detailed cross-sectional images of the body, allowing visualization of internal structures based on tissue density differences. 1
Basic Procedure
- CT scanning involves the patient lying on a table that moves through a donut-shaped machine (CT scanner) while an X-ray tube rotates around the body, taking multiple images from different angles 1
- These images are processed by a computer to create cross-sectional pictures (slices) of the body's internal structures 1
- The entire procedure typically takes between 10-30 minutes depending on the area being scanned 1
- Most CT scans are painless, quick, and non-invasive 1
Types of CT Scans
- Standard CT: Creates basic cross-sectional images without contrast material 1
- CT with contrast: Involves injection of iodinated contrast material to enhance visualization of blood vessels, organs, and tissues 1
- CT Angiography (CTA): Specifically designed to evaluate blood vessels using contrast material 1
- Whole-body CT (WBCT): Comprehensive scan of multiple body regions, often used in trauma cases 1
- High-resolution CT: Provides more detailed images, particularly useful for lung diseases 1
Contrast Material
- Many CT scans use intravenous (IV) contrast agents to improve visualization of blood vessels and organs 1
- Contrast is typically an iodine-based solution injected through a vein in the arm 1
- Some patients may require oral contrast for abdominal/pelvic imaging 1
- Patients with kidney problems or contrast allergies may require special preparation or alternative imaging 1
Radiation Exposure
- CT scans use ionizing radiation to create images, which carries a small theoretical risk of cancer 2
- The radiation dose varies depending on the type of scan and body part examined 2
- Modern CT scanners use dose-reduction techniques to minimize radiation exposure while maintaining image quality 2
- For perspective, a typical CT scan of the head and trunk delivers approximately 20 millisievert, corresponding to an additional lifetime cancer mortality risk of approximately 0.1% 2
Specialized CT Applications
- Cardiac CT: Evaluates coronary arteries, heart structure, and function 3
- CT Urography (CTU): Specialized protocol for detailed imaging of the urinary tract 1
- Dual-energy CT: Uses two different energy levels to better characterize tissues and reduce artifacts 1
- CT Perfusion: Measures blood flow through tissues, particularly useful in stroke evaluation 4
- 3D Reconstructions: Advanced processing creates three-dimensional models useful for surgical planning 5
Preparation for a CT Scan
- Patients may need to fast for several hours before certain types of CT scans, especially those using contrast 1
- Metal objects, jewelry, and certain clothing items must be removed as they can interfere with the images 1
- Patients should inform their doctor about any medications, allergies, or medical conditions before the scan 1
- Women should inform their doctor if there is any possibility of pregnancy due to radiation concerns 2
Common Uses of CT Scans
- Diagnosing and staging cancer 1
- Evaluating trauma patients for internal injuries 1
- Detecting vascular diseases like aneurysms or blood clots 1
- Diagnosing lung diseases and pulmonary hypertension 1
- Evaluating complex bone fractures 1
- Guiding procedures such as biopsies and minimally invasive treatments 1
Advantages and Limitations
Advantages:
- Fast acquisition time compared to MRI 1
- Excellent for visualizing bone details 5
- Widely available in most hospitals 1
- Can be performed with cardiac pacemakers or other implanted devices that might be contraindicated for MRI 1