4. Medical Imaging Systems Flashcards
(20 cards)
Wavelength of X-rays
0.01-10nm
How does X-rays work?
- X rays are absorbed differently by tissues.
- Attenuation creates contrast
3 Uses of X-ray?
dental cavities, fluid in lungs, breast cancer
What is projectional radiography?
3D body mapped to a 2D shadw image.
Limitation of an X-ray
Poor soft tissue contrast.
How does CT work?
Multiple X-rays at various angles. Reconstruct the 3D body as 2D cross sections.
What are CTs used for?
Detailed imaging of the brain, lungs …
What advantage does CT have over x-rays?
Better for soft tissues, overlapping structures detected.
What is the nature of an ultrasound wave?
mechanical longitudinal waves (2-13 MHz)
How does ultrasound work?
Echoes at different times based on tissue depth.
distance = vt/2
Pros of ultrasound.
Safe (no ionizing radiation)
Real-time imaging (used in fetal images)
Uses of ultrasound
Soft tissue, heart, kidney, live motion
How do MRI scans work?
- MRI produce powerful magnetic fields
- protons align with that field
- radio waves pulsed through, causing protons to spin
- Emitted signals are detected and processed by a computer.
why are MRIs great?
High detail imaging of soft tissues
3 advantages of mRIs over Cts
- no radiation
- better soft tissue contrast
- slower and costlier
What is nuclear medicine?
Internal radiation via pharmaceuticals
How does PET scan work?
- uses positron emitting tracers
- Highlights deacing activity
How does SPECT work?
- Uses gamma-emitting isotopes
- good for bones
What is a unique function of nuclear imaging?
Shows function not just structure
Why is nuclear imaging good?
detects diseases earlier
