Fast moving electrons are decelerated by interaction with atoms of a metal suchas tungsten
1 of 29
Why is the X-ray tube evacuated
So the electrons pass through the tube without interacting with gas atoms
2 of 29
What is the anode made from in an X-ray tube
Metal
3 of 29
What is the equation for the shortest wavelength (of the X-ray photon)
λ=hc/eV ( V for p.d.)
4 of 29
What does increasing the tube current do
It increases the intensity of the X-rays
5 of 29
Define attenuation
The decrease in the intensity of an electromagnetic radiation as it passes through matter
6 of 29
Name the four types of attenuation mechanisms
Simple scatter, photoelectric effect,Compton scattering,pair production
7 of 29
Describe the simple scatter mechanism
The X-ray photon intersects with an electron in the atom but has less energy than the energy required to remove the electron so the X-ray photon simply bounces or without any change to its kinetic energy
8 of 29
Describe the Compton scattering mechanism
The incoming X-ray photon interacts with an electron within the atom. The electron is ejected from the atom and the X-ray photon is scattered with reduced energy
9 of 29
Describe the pair production mechanism
An X-ray photon interacts with the nucleus of the atom, it disappears and the electromagnetic energy of the photon is used to create an electron and its anti particle the positron
10 of 29
What are the two most common contrast medium and why are they used for humans
Iodine and barium compounds because they're relatively harmless to humans
11 of 29
What does a CAT scanner do
It records a large number of X-ray images from different angles and assembles them into a 3D image with the help of sophisticated software
12 of 29
What is brachytherapy
Tumours being targeted by gamma radiation or high energy x rays from outside the patient or by by implanting a radioactive source next to or inside the tumour
13 of 29
What does the gamma camera detect
The gamma photons emitted from the radioactive nuclei injected into the patient
14 of 29
What does a gama camera show
It shows a high quality image that shows the concentrations of the medical tracer within the patients body
15 of 29
What is the difference between gama camera and x -ray imaging
X-ray produces an image of the anatomy of thof body whereas a gamma camera produces an image of the function and process ofnth body
16 of 29
What is then difference from between a PET scan and a CAT scan
PET scan uses gamma radiation instead of x-rays
17 of 29
What are the two main medical tracers used in a PET scan
Flurodeoxyglucose and carbon monoxide
18 of 29
What is a scintillator made of
Sodium iodide
19 of 29
What's the advantage of using flurodeoxyglucose
Our bodies treat it like glucose
20 of 29
Hats the advantage of using carbon monoxide
It's good at clinging to haemoglobin molecules in red blood cells so it can be transported through the body
21 of 29
What are Ultrasounds
It's longitudinal sound waves with frequency above 20KHz
22 of 29
What's the advantages of ultrasound
It's harmless to humans and is quick
23 of 29
What's an ultrasound transducer
A device used both to generate and to receive ultrasound. It changes electrical energy to sound and sound to electrical energy, by the piezoelectric effect
24 of 29
What is the piezoelectric effect
When an external p.d is applied across the opposite faces of the crystal the electric field can either compress or stretch the crystal
25 of 29
What do u have to do to generate an ultrasound in a ultrasound transducer
Use a high frequency alternating p.d. which you apply across opposite faces of a crystal
26 of 29
What impact would applying an alternating p.d. Have on the crystals
It would repeatedly expand and compress
27 of 29
What do you do to produce an intense ultrasound in the ultrasound transducer
Choose a frequency the same as the natural frequency of oscillation of the crystal
28 of 29
What happens when a transducer sends ultrasound pulses into the body of the patient
Each pulse of ultrasound will be partly reflected and partly transmitted at the boundary between any two different tissues
29 of 29
Other cards in this set
Card 2
Front
Why is the X-ray tube evacuated
Back
So the electrons pass through the tube without interacting with gas atoms
Card 3
Front
What is the anode made from in an X-ray tube
Back
Card 4
Front
What is the equation for the shortest wavelength (of the X-ray photon)
Comments
No comments have yet been made