P3.1 Medical Applications of Physics Flashcards
How do X-ray’s affect photographic film?
The same way as light (they turn it black)
X-rays are —- by healthy tissue and —- by denser material e.g teeth and bones.
1) transmitted
2) absorbed
Name 2 uses of X-rays.
- Diagnoses bone fractures
- Diagnoses dental problems.
What do CCDs do?
Form X-rays electronically.
How do CCDs form X-rays electronically?
Small silicon chips divided into millions of identical pixels in a grid detect the X-Ray waves and produce electronic signals used to form high resolution images (same technology used camera)
What are CT scans used for?
They use X-rays to produce high resolution images of soft and hard tissue.
How do CT scans take place?
- The patient is put inside a cylindrical scanner and an X-Ray beam is fired through the body from an X-day tube and picked up by detectors on the opposite side.
- X-ray tube and detector are rotated during the scan.
- Computer interprets scan to form a 3D image from 2D slices.
How are X-rays used to kill cancer cells?
- X-rays focused on rumour using wide beam.
- Beam is rotated around the patient with the tumour at the centre.
- This minimises normal cell exposure to radiation.
- X-rays are at just the right dosage to kill all cancer cells and do minimal damage to normal cells
Name 3 properties that X-rays have.
- Electromagnetic transverse wave.
- Short wavelength (diameter of an atom)
- High frequency.
What precautions do radiographers take to stay safe in X-rays?
- Wear lead aprons
- Stand behind a lead screen
- Leave room while scans take place
What precautions are taken for a patient having an X-ray to be as safe as possible?
- Lead is used to shield areas of the patients body not being scanned
- Minimum exposure time
What are ultrasound waves?
Higher frequency waves than the range of human hearing (+ 20,000 Hz)
How does ultrasound work?
- When the ultrasound wave passes from one medium to another, some of the waves are reflected off the boundary and some are refracted.
- The amount of time it takes for the reflections to reach a detector = how far away the boundary is.
Name 2 uses of ultrasound.
- Breaking down of kidney stones
- Pre-natal foetus scanning
Give the one advantage and one disadvantage of ultrasound.
Advantage = non ionising, safe Disadvantage = images usually fuzzy so it's hard to diagnose illness.
Give the one advantage and two disadvantages of X-rays.
Advantage = clear images of bone and metal Disadvantage = Ionising, causes cancer, not safe for babies Disadvantage = doesn't produce images except of bone and metal
Give the two advantages and one disadvantage of CT scans.
Advantage = produces detailed images with high resolution for easy diagnosis. Advantage = produces high quality 3D images useful for planning complicated surgery. Disadvantage = more x-radiation than standard X-ray photographs so more ionisation.
What is refraction?
When waves change direction after entering a new medium.
How does refraction happen?
- When light slows down it bends towards the normal
- When light enters a new medium density changes so light slows down
When does a light wave not refract?
If it hits a 90 degree boundary it will slow down but not change direction.
What do convex lenses do?
- Converge light
- Bulge outwards
- For longsightedness
What type of image do convex lenses produce between F - 2F?
- Real
- Inverted
- Magnified
What type of image do convex lenses produce when the object is closer than F?
- Magnified
- Virtual
- Upright
- Same side of lens
What type of image do concave lens produce?
- Smaller
- Virtual
- Same side of lens
- Upright