Podcast
Questions and Answers
What type of injuries can computed tomography (CT) of the head help assess?
What type of injuries can computed tomography (CT) of the head help assess?
Which of the following is NOT a reason for performing a CT scan of the head?
Which of the following is NOT a reason for performing a CT scan of the head?
How do the images produced by a CT scan differ from traditional x-ray images?
How do the images produced by a CT scan differ from traditional x-ray images?
What should you remove before undergoing a CT scan of the head?
What should you remove before undergoing a CT scan of the head?
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Which condition is indicated for a CT scan of the head because of sudden severe headaches?
Which condition is indicated for a CT scan of the head because of sudden severe headaches?
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What preparation might be required before a CT scan of the head?
What preparation might be required before a CT scan of the head?
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In what way can CT scan images be utilized after their generation?
In what way can CT scan images be utilized after their generation?
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Which of the following is NOT a use of head CT scans?
Which of the following is NOT a use of head CT scans?
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What is the recommended waiting period for breastfeeding after an IV contrast material is given?
What is the recommended waiting period for breastfeeding after an IV contrast material is given?
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What is stated about the risk of serious allergic reactions to iodine-based contrast materials?
What is stated about the risk of serious allergic reactions to iodine-based contrast materials?
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What is the primary reason children should only undergo CT exams when essential?
What is the primary reason children should only undergo CT exams when essential?
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What is one of the primary uses of CT scanning in facial trauma cases?
What is one of the primary uses of CT scanning in facial trauma cases?
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Which of the following is a benefit of CT scanning compared to conventional x-rays?
Which of the following is a benefit of CT scanning compared to conventional x-rays?
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Which direction should the patient's head be positioned for a brain CT exam?
Which direction should the patient's head be positioned for a brain CT exam?
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What should the table height be centered on during patient positioning?
What should the table height be centered on during patient positioning?
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What is a potential risk associated with CT scanning?
What is a potential risk associated with CT scanning?
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What is the typical amount of injected intravenous contrast media for brain imaging?
What is the typical amount of injected intravenous contrast media for brain imaging?
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Why might CT scanning be preferred over MRI for certain patients?
Why might CT scanning be preferred over MRI for certain patients?
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How long is the typical delay between contrast injection and the start of scanning?
How long is the typical delay between contrast injection and the start of scanning?
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How does CT scanning assist in diagnosing diseases of the temporal bone?
How does CT scanning assist in diagnosing diseases of the temporal bone?
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What practice is suggested for reducing ocular lens exposure during a CT scan?
What practice is suggested for reducing ocular lens exposure during a CT scan?
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What should women inform their doctor before undergoing a CT scan?
What should women inform their doctor before undergoing a CT scan?
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In what situation is CT scanning generally not recommended?
In what situation is CT scanning generally not recommended?
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What does CT angiography assess in patients?
What does CT angiography assess in patients?
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Which factors should influence the decision to use axial or helical scan modes for a head CT exam?
Which factors should influence the decision to use axial or helical scan modes for a head CT exam?
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What is the recommended scan coverage for routine head CT exams?
What is the recommended scan coverage for routine head CT exams?
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What is the appropriate slice thickness for CT scan reconstructions?
What is the appropriate slice thickness for CT scan reconstructions?
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What volume of contrast agent is typically used in a head CT post-contrast acquisition?
What volume of contrast agent is typically used in a head CT post-contrast acquisition?
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What is the recommended delayed acquisition time post-contrast injection for a head CT exam?
What is the recommended delayed acquisition time post-contrast injection for a head CT exam?
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Study Notes
Computed Tomography (CT)
- CT uses special X-ray equipment to assess head injuries, severe headaches, dizziness, aneurysms, bleeding, stroke, and brain tumors.
- CT aids in evaluating the face, sinuses, and skull, and in planning radiation therapy for brain cancer.
- CT helps diagnose internal injuries and bleeding quickly, saving lives in emergencies.
- CT, or CAT scan, is a diagnostic medical imaging technique.
- CT produces multiple images of the body's interior, akin to traditional X-rays.
CT Scanning of the Head
- CT images provide detailed views of internal organs, bones, soft tissue, and blood vessels, superior to traditional X-rays, particularly for soft tissues and blood vessels.
- CT scans offer more detailed information on head injuries, stroke, brain tumors, and other brain diseases compared to regular radiographs (X-rays).
CT Scan Preparation
- Wear comfortable, loose-fitting clothing and a gown may be required.
- Remove metal objects (jewelry, eyeglasses, dentures, hairpins) as they may affect CT images.
- Patients might be asked to remove hearing aids and removable dental work.
- Women may need to remove bras containing metal underwire.
- Any piercings may also need to be removed.
Common Uses of CT Head Scans
- Detect bleeding, brain injuries, and skull fractures.
- Diagnose bleeding caused by a ruptured or leaking aneurysm (in cases of sudden severe headaches).
- Identify blood clots or brain bleeding after stroke symptoms.
- Identify brain tumors.
- Detect enlarged brain cavities (ventricles) in cases of hydrocephalus.
- Diagnose diseases or malformations of the skull.
Additional CT Applications
- Evaluate the extent of bone and soft tissue damage in patients with facial trauma, aiding in surgical planning and reconstruction.
- Diagnose temporal bone diseases that may cause hearing problems.
- Identify inflammation or changes in paranasal sinuses.
- Plan radiation therapy for brain or other tissues.
- Guide needle insertions for tissue sampling (biopsy) from the brain.
- Assess aneurysms, arteriovenous malformations, and blood vessels via CT angiography.
Benefits of CT Scans
- CT is painless, noninvasive, and accurate.
- CT images simultaneously visualize bone, soft tissue, and blood vessels.
- Images are highly detailed, covering many tissue types, including lungs, bones, and blood vessels—exceeding the detail of standard X-rays.
- CT exams are fast and efficient, especially critical in emergency situations, enabling rapid identification of internal injuries and bleeding, potentially saving lives.
- CT may be a cost-effective diagnostic imaging tool for numerous medical issues.
- CT is less sensitive to patient movement than MRI.
- CT can be performed on patients with implanted medical devices, unlike MRI.
- A diagnosis and treatment plan determined by CT scanning may obviate the need for surgical procedures like exploratory surgery and biopsies.
Risks of CT Scans
- Excessive radiation exposure slightly increases the risk of cancer; however, the benefit of an accurate diagnosis typically outweighs this risk.
- The effective radiation dose varies. Consult the relevant radiation dose information.
- Consult the radiology or medical team for specific advice concerning pregnancy and X-rays, especially concerning the safety of administering X-rays, if pregnant.
- IV contrast materials can cause allergic reactions, although the risk is extremely uncommon. Radiology departments are fully prepared to address such reactions.
- Children's greater sensitivity to radiation necessitates careful consideration.
- CT scans should only be administered when absolutely essential and should use lower radiation doses where possible.
Patient Positioning for CT Scans
- The patient is placed supine (lying on their back) with their head securely positioned in the headholder of the CT scanner.
- The scanner's table is adjusted to center the external auditory meatus (EAM) in the gantry axis to minimize ocular lens exposure.
- The scan angle should align with the line from the supraorbital ridge and the inner aspect of the posterior foramen magnum margin to minimize exposure to the eyes.
- Additional positioning adjustments (like chin tucks and gantry tilts) are made to ensure precise alignment and optimized image quality.
Contrast Media (CT)
- Some CT brain scans require injecting contrast media for optimal visualization.
- Contrast administration should occur as directed by a radiologist using standardized protocols.
- The contrast media are typically in intravenous formulations. The radiologist will inform of the appropriate procedure. A standard procedure usually includes a delay of 4 minutes between injecting the contrast media and commencing the scan.
Axial vs. Helical CT Scans
- Both axial and helical CT scan modalities have advantages and disadvantages for routine head examinations.
- The optimal choice should depend on the patient's condition, the available imaging equipment, and desired qualities of the generated images. Consult relevant specialists for the most appropriate modality.
CT Scan Protocols
- Scan coverage usually starts just below the foramen magnum through the vertex and may additionally encompass the anterior aspect of the C1 arch ( in instances of trauma).
- For head scanning, imaging planes should generally be stacked along the axial plane, parallel to a line from the external auditory meatus to orbital roof.
- Scan parameters vary but usually include slice thicknesses ranging from 3-5 mm. The use of lower reconstruction thresholds is common in certain cases.
- Data acquisition procedures for head CT might involve KVP, mA, and rotation time adjustments. These values may differ depending on the clinical situation, and these adjustments are made by the radiologist.
- Contrast-enhanced protocols often include using soft-tissue algorithms, with specific window/level settings for maximizing the visualization.
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