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Questions and Answers
What should influence the decision to use axial or helical scans in head CT exams?
What should influence the decision to use axial or helical scans in head CT exams?
What is the recommended scan slice thickness for head CT scans?
What is the recommended scan slice thickness for head CT scans?
Which injection protocol is appropriate for a contrast study after a non-contrast study?
Which injection protocol is appropriate for a contrast study after a non-contrast study?
What is the kVp setting recommended for routine head CT scans?
What is the kVp setting recommended for routine head CT scans?
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What scan coverage is specified for head CT exams?
What scan coverage is specified for head CT exams?
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What does the most recent American College of Radiology (ACR) Manual on Contrast Media state regarding breastfeeding after administration of IV contrast?
What does the most recent American College of Radiology (ACR) Manual on Contrast Media state regarding breastfeeding after administration of IV contrast?
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Why is it recommended to use low-dose techniques during CT scans in children?
Why is it recommended to use low-dose techniques during CT scans in children?
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When positioning a patient for a CT brain scan, what is a critical consideration for reducing ocular lens exposure?
When positioning a patient for a CT brain scan, what is a critical consideration for reducing ocular lens exposure?
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What is the typical amount of intravenous contrast administered for brain imaging?
What is the typical amount of intravenous contrast administered for brain imaging?
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What are the preferred head positioning techniques to avoid ocular lens exposure?
What are the preferred head positioning techniques to avoid ocular lens exposure?
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What is the risk level associated with allergic reactions to iodine-based contrast materials?
What is the risk level associated with allergic reactions to iodine-based contrast materials?
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What is the typical waiting period before starting a CT scan after intravenous contrast administration?
What is the typical waiting period before starting a CT scan after intravenous contrast administration?
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What guideline should be followed for intravenous contrast administration during imaging?
What guideline should be followed for intravenous contrast administration during imaging?
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What is one of the primary uses of CT scanning in patients with facial trauma?
What is one of the primary uses of CT scanning in patients with facial trauma?
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What is a significant advantage of CT scans compared to conventional x-rays?
What is a significant advantage of CT scans compared to conventional x-rays?
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Which of the following is a benefit of CT scans?
Which of the following is a benefit of CT scans?
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What should women do before undergoing a CT scan if there is a possibility they are pregnant?
What should women do before undergoing a CT scan if there is a possibility they are pregnant?
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What is a risk associated with CT scans?
What is a risk associated with CT scans?
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Which condition can be assessed using CT angiography?
Which condition can be assessed using CT angiography?
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Why is CT scanning preferred when imaging patients with implanted medical devices?
Why is CT scanning preferred when imaging patients with implanted medical devices?
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Which of the following statements about CT scanning is true?
Which of the following statements about CT scanning is true?
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What primary symptoms can be assessed using CT scans of the head?
What primary symptoms can be assessed using CT scans of the head?
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What is a significant advantage of CT images over traditional x-rays?
What is a significant advantage of CT images over traditional x-rays?
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What preparations are advised for a patient before undergoing a CT scan of the head?
What preparations are advised for a patient before undergoing a CT scan of the head?
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Which condition can a CT scan of the head help to detect?
Which condition can a CT scan of the head help to detect?
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How can CT scan images be utilized after they are captured?
How can CT scan images be utilized after they are captured?
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Which patient scenario is a CT scan most likely to be urgently required?
Which patient scenario is a CT scan most likely to be urgently required?
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What is one of the main uses of CT scanning concerning brain tumors?
What is one of the main uses of CT scanning concerning brain tumors?
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Which of the following statements about hydrocephalus and CT scans is true?
Which of the following statements about hydrocephalus and CT scans is true?
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Study Notes
Computed Tomography (CT)
- CT is a diagnostic medical imaging technique using X-rays
- It creates multiple images (or pictures) of the inside of the body
- It uses special X-ray equipment to assess head injuries, severe headaches, dizziness, and other symptoms of aneurysm, bleeding, stroke, and brain tumors.
- Images of internal organs, bones, soft tissue, and blood vessels are much more detailed than standard X-rays using contrast to show soft tissues and blood vessels well
- CT helps to evaluate the face, sinuses, skull and can plan radiation therapy for brain cancer.
- In emergencies, it reveals internal injuries and bleeding quickly, potentially saving lives.
CT Scanning of the Head
- CT scanning of the head can detect bleeding, brain injuries, and skull fractures.
- It can also pinpoint bleeding from a ruptured aneurysm.
- It is used to identify blood clots or bleeding in the brain after a stroke.
- CT scans can identify brain tumours.
- It is used to evaluate enlarged brain cavities (ventricles) that can indicate hydrocephalus.
- It can be used to diagnose diseases or malformations of the skull.
CT Scanning Uses
- Helps assess the extent of bone and soft tissue damage in facial trauma, planning reconstructive surgery
- Identifying temporal bone diseases which may cause hearing problems.
- Determining if inflammation is present in the paranasal sinuses.
- Planning radiation therapy for brain or other tissue cancers.
- Guiding needles for biopsies of the brain
- Assessing aneurysms, arteriovenous malformations, and blood vessels through a technique called CT angiography
Benefits of CT Scans
- CT scanning is painless, non-invasive and accurate.
- It allows viewing bones, soft tissues, and blood vessels simultaneously.
- CT scans provide highly detailed images of many tissues, including the lungs, bones, and blood vessels.
- CT scans are rapid and can quickly assess internal injury and bleeding in emergency situations.
- CT is shown to be a cost-effective imaging tool for a wide range of clinical problems.
- CT is less sensitive to patient movement than MRI.
- CT can be performed with implanted medical devices unlike MRI.
- Diagnosis determined by CT can remove the need for exploratory and surgical biopsies
Risks of CT Scans
- There is a slight chance of cancer from excessive radiation exposure. However, a precise diagnosis often outweighs the potential risk.
- Effective radiation dose varies; see the relevant procedures page
- Pregnant women should inform their doctor or X-ray/CT technician if they are pregnant.
- IV contrast manufacturers recommend not breastfeeding infants for 24-48 hours after administering contrast material. However, absorbed amounts during breastfeeding are extremely minimal.
- Radiology departments are well-equipped to manage rare potential allergic reactions related to iodine-containing contrast.
- Children's sensitivity to radiation means CT scans should only be performed if essential for diagnosis and not repeated unnecessarily. Low-dose techniques are always preferred with children
Preparation for CT Scan
- Wear comfortable, loose-fitting clothing. A gown may be required.
- Remove metal objects (jewelry, eyeglasses, dentures, hairpins).
- Remove hearing aids and removable dental work.
- Women should remove bras containing metal underwire.
- Remove any piercings if possible.
Patient Positioning for Adult Head CT Scan (Brain)
- Patient should be supine (lying on their back).
- Head first into the gantry and secured in the head-holder whenever possible.
- Centre the table such that the external auditory meatus (EAM) is at the centre of the gantry.
- To minimise eye exposure, the scan angle should be parallel to a line from the supraorbital ridge to the posterior margin of the foramen magnum. This can be achieved by tilting the patient's chin towards the chest or tilting the gantry itself.
Contrast in CT Scans
- Oral contrast is not usually used for brain CT.
- Injected contrast media is used in some situations.
- Administer intravenous contrast as directed by the supervising radiologist following appropriate injection protocols and guidelines (e.g. use of Intravascular Contrast Media).
- A typical amount is 100 cc of 300 mg/cc strength, injected at 1 cc/sec.
- A 4-minute delay between contrast injection and scan start is typical.
Axial Versus Helical Scan Mode
- Both axial and helical scan modes have advantages and disadvantages for routine head CT scans.
- Relevant factors include patient indication, scanner capabilities, and image quality requirements.
- Consult both the manufacturer and a medical physicist to determine the most suitable mode for the individual patient case
CT Scan Protocols (with/without contrast)
- Scan coverage goes from just below the foramen magnum to the vertex, adjusting for trauma below the anterior arch of C1.
- Scan plane is stacked axial, paralleling a line from the orbital roof to the external auditory meatus.
- Slice thickness: 5-3 mm, reconstruction: 1 mm
- kVp, mA, Rotation Time for Non-contrast : [specific values].
- For Contrast: 50 cc Omnipaque 300IV, soft tissue algorithm; soft tissue window: WC:40, WW:80
- Contrast injection protocol: non-contrast first, then delayed contrast aquisition
- Delay time (>5 min) after contrast injection.
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Description
This quiz explores the fundamentals of Computed Tomography (CT), a key diagnostic imaging technique that utilizes X-rays to produce detailed images of the body's internal structures. It highlights the applications of CT scanning in evaluating head injuries, detecting brain tumors, and diagnosing various medical conditions. Test your knowledge on how CT scans assist in emergency situations and regular assessments.
