Podcast
Questions and Answers
What does the term 'tomography' derive from?
What does the term 'tomography' derive from?
What was the first commercially available CT scanner invented by?
What was the first commercially available CT scanner invented by?
Which part of the CT scanner generates the x-ray beams?
Which part of the CT scanner generates the x-ray beams?
What is the primary function of the detector in a CT scanner?
What is the primary function of the detector in a CT scanner?
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What key contribution did Allan McLeod Cormack make in the development of CT?
What key contribution did Allan McLeod Cormack make in the development of CT?
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When was the first patient brain-scan performed using an EMI scanner?
When was the first patient brain-scan performed using an EMI scanner?
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Which component of the CT scanner serves to narrow the x-ray beams?
Which component of the CT scanner serves to narrow the x-ray beams?
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Who were the recipients of the Nobel Prize in 1979 for their contributions to CT?
Who were the recipients of the Nobel Prize in 1979 for their contributions to CT?
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What is a key characteristic of a conventional scan compared to a spiral scan?
What is a key characteristic of a conventional scan compared to a spiral scan?
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What device in CAT scanning is responsible for measuring the penetrated X-ray amounts?
What device in CAT scanning is responsible for measuring the penetrated X-ray amounts?
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Which statement accurately describes the Hounsfield scale?
Which statement accurately describes the Hounsfield scale?
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What type of abnormalities can be revealed by CAT scanning of the brain?
What type of abnormalities can be revealed by CAT scanning of the brain?
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What is one purpose of evaluating acute cranial-facial trauma?
What is one purpose of evaluating acute cranial-facial trauma?
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What is the purpose of reconstructing multiple two-dimensional images in CAT scanning?
What is the purpose of reconstructing multiple two-dimensional images in CAT scanning?
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In which position should a patient be placed for cranial scans?
In which position should a patient be placed for cranial scans?
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What do the numbers on the Hounsfield scale represent?
What do the numbers on the Hounsfield scale represent?
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What is the recommended fasting period before a specific examination?
What is the recommended fasting period before a specific examination?
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During a conventional scan, why is it important for the patient to hold their breath?
During a conventional scan, why is it important for the patient to hold their breath?
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Which imaging technique is specifically noted for its ability to reveal abnormalities in the brain?
Which imaging technique is specifically noted for its ability to reveal abnormalities in the brain?
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Which of the following is NOT included in the evaluation of the neck and upper airway?
Which of the following is NOT included in the evaluation of the neck and upper airway?
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What is one reason for imaging to assess lung conditions?
What is one reason for imaging to assess lung conditions?
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What technique should be followed during an imaging examination for optimal results?
What technique should be followed during an imaging examination for optimal results?
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Which condition is evaluated when imaging the chest area?
Which condition is evaluated when imaging the chest area?
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Which anatomical structures are assessed for abnormalities during head and neck imaging?
Which anatomical structures are assessed for abnormalities during head and neck imaging?
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What condition is NOT indicated for testing according to the content provided?
What condition is NOT indicated for testing according to the content provided?
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Which of the following is a purpose of the Bone CT scan?
Which of the following is a purpose of the Bone CT scan?
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What is one benefit of using a Bone CT scan over a plain X-ray?
What is one benefit of using a Bone CT scan over a plain X-ray?
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Which of the following statements about the risks of X-rays is true?
Which of the following statements about the risks of X-rays is true?
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What condition is specifically associated with women after menopause and may also occur in men?
What condition is specifically associated with women after menopause and may also occur in men?
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Which of the following is NOT a reason for conducting a test for abdominal pain or swelling?
Which of the following is NOT a reason for conducting a test for abdominal pain or swelling?
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What is a potential outcome of undergoing a Bone CT scan?
What is a potential outcome of undergoing a Bone CT scan?
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For which condition might a CT scan be used to check if a previously treated disease has recurred?
For which condition might a CT scan be used to check if a previously treated disease has recurred?
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Study Notes
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.
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