Untitled Quiz

Computed Tomography (CT)

• CT uses a computer to create cross-sectional images of the human body using X-rays.
• The Greek word "tomos" means "slice" and "graphy" means "write". A tomogram is a two-dimensional image of a slice or section through a 3D object.

History of CT

• Sir Godfrey Hounsfield invented the first commercial CT scanner in 1971 at EMI Central Research Laboratories in the UK.
• The first EMI-Scanner was installed in Atkinson Morley Hospital in Wimbledon, England.
• The first patient brain scan was performed on October 1, 1971.
• Early scanners were limited to brain scans only.

Nobel Prize

• Hounsfield and Allan McLeod Cormack received the 1979 Nobel Prize for their work on CT.
• Cormack's theoretical calculations were used by Hounsfield.

CT Scanning Machine Parts

• Gantry: The scanner system.
• Patient table: The surface which the patient sits on.
• Computer (operation control): Controls the scanning process.
• Scanner system sub-components:
  • X-ray tube: Generates X-ray beams.
  • Detectors: Detect the X-rays passing through the body.
  • Collimators: Narrow the X-ray beams.
  • Filters: Filter out harmful X-rays.

Types of CT Scans

• Conventional: The scan is taken slice by slice; the scan stops each time. Patients need to hold their breath.
• Spiral (or helical): The scan is continuous, in a spiral pattern. This is faster.

CT Scan Principle

• X-rays pass through the body. Some are absorbed and some penetrate.
• Detectors measure the amount of X-rays that penetrate.
• A computer processes this information to create cross-sectional images.

CT Number (Hounsfield Unit)

• A scale used to display CT images on a screen.
• A linear transformation that referenced distilled water (0), and ranges from −1000 (air) to +1000 (bone). The Hounsfield Unit is the unit of measurement.
• Shows the radiodensity of different tissues. A table showing tissue types and corresponding Hounsfield Units is provided.

CT Scan of the Brain

• Reveals abnormalities like tumors, blood clots, hemorrhages, and other anatomical issues.
• Used to diagnose acute cranial facial trauma, stroke, and potential intracranial hemorrhage.
• Assess development of the head and neck; evaluate tumors and clots.
• Scan parameters include a certain scan range (starting at the base and ending at the vertex of the skull), shallow breathing, positioning (supine), and immobilized head and arms along the sides.

CT Scan of the Neck

• Used for evaluating the spine, airway, carotid vessels, salivary and thyroid glands.
• Identifying lesions in submandibular glands or infections
• Examining head and neck-associated diseases, foreign bodies lodged in the neck/upper airway, Tumors and Infections of pharynx vocal cords.

CT Scan of the Chest (Lungs)

• Evaluates the size, shape, and position of lungs and other chest structures.
• Helps determine causes of symptoms like shortness of breath or chest pain.
• Diagnose lung diseases (tumors, excess fluid, pulmonary embolism), as well as tuberculosis, emphysema, and pneumonia.

CT Scan of Abdomen

• Used for testing abdominal pain or swelling.
• Evaluates the presence of masses, tumors (including cancer), injury, infections, kidney stones, appendicitis, alcoholic liver disease, cancers (pancreas, colon, renal pelvis), and peritoneal fibrosis.

CT Scan of Bone

• Identifies spine abnormalities, such as spinal stenosis (which may cause back pain) and tumors/tumors in soft tissue surrounding bones.
• Diagnoses osteoporosis, fractures, and unusual bone formations, abnormalities.

CT Scan Advantages

• Quick and painless
• Can diagnose and guide treatment for a wider range of conditions compared to plain X-rays.
• No overlap of images.

CT Scan Disadvantages

• Small risk of cancer in the future (especially in children).
• Higher radiation dose compared to other imaging techniques.
• Some procedures require anesthesia, needing breath holding that some patients find hard to manage.
• Risk to nearby bone, and possible cause of childhood cancer and leukemia.