CT and dual energy CT - System and acquisition
8 important questions on CT and dual energy CT - System and acquisition
What is a beam, and what kind of beam exist?
- Parallel beam: detector is in a straight line with the source (so only shots a thin slice per session). You have to take multiple 'pictures' (+1000). It also goes around the body, but always in straight lines.
- Fan beam: The X-ray tube and detector arrays rotate together in a fixed geometrical orientation. It pictures a wide portion of the patient simultaneously. It also goes around the body.
Why prefer a fan beam about a parallel beam
- Reduce motion artifacts
- Shorter scan time
- Higher signal intensity
- Higher spatial resolutions
How tick are the slices and how long does one rotation take?
- 8-10 mm
- 4 minutes per rotation
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What is a spiral CT?
- Focus of x-ray tube has a spiral path relative to the patient
- Faster than slice-for-slice
What is multi slice CT? What are advantages (3)?
Advantages:
- Reduced scan time
- Reduced motion artifacts
- 4D volume scanning
In dynamic CT scanning you want to measure changes in one organ. What do you need?
- Usually a contrast is used to see difference over time
- You want to cover the organ in 1 rotation
- You need high spatial resolution
- Because you scan the organ in 1 rotation you can just use axial/sequential scanning.
- You use a multi slice scanner with very much and very thin slices. (about 16 cm: 320 x 0.6 mm)
Name three applications of dynamic CT.
- Myocardial perfusion
- Brain perfusion
- 4D kinematics of joints
How can you minimize the patient dose (3)?
- Decrease scan range
- Lower kVP
- Apply tube filtering
The question on the page originate from the summary of the following study material:
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- Never study anything twice again
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- 100% sure, 100% understanding
