Positron Tomography Flashcards
What is the wave equation?
Velocity = Wavelength x Frequency
How are ultrasound waves produced?
The vibration of quartz crystal using AC current in a process known as piezoelectric effect
How are ultrasound waves picked up?
By using the piezoelectric effect to measure the reflected pulse as reflected ultrasound waves vibrate the quartz crystals and create a small electric current
How is the penetration of waves determined?
Based on acoustic impedance (z) where:
z = p x v Where p: Density, v: Velocity
What is the velocity of ultrasound waves based off?
The medium the wave travels through
What is the fate of ultrasound waves?
The majority of the waves are absorbed by heat by others are reflected
How is the percentage of reflected ultrasound wave determined when moving between two mediums
= (Z2-Z1)^2/(Z2+Z1)^2
What is used in order to transfer transducer produced waves into the patient’s body?
An ultrasound gel
How can bone density be measured using a transducer?
By using two transducers as distance, frequency and wavelengths are known
How can blood flow be measured
Using the doppler effect
What type of rays are x-rays?
Electromagnetic waves
Characteristics of x-rays?
high frequency, a short wavelength that can ionise tissue
What process is used to produced X-rays
Thermonic emission
Describe thermionic emission
A beam of electrons from high voltage head filament into a cooled target metal that mostly turns into heat but also X-rays
What determines the amount of X-ray absorbed?
Density. This explains why bone mostly shows up as it absorbs large portions of the x-rays
Describe the two ways electrons and the target metal interact to produce X-rays
1) The braking/slowing of electrons produce slow amounts of X-rays
2) At certain frequencies, the electron beam knock out electrons from the inner shell and the energy left over from the movement of an electron from the higher to lower energy level to replace the loss electron is converted into X-ray spikes.
How are X-rays detected?
By photographic film or image intensitifier
Define CT scans
Slices of many X-rays to produce 3D images by spinning a X-ray ring at a high angular velocity
What is alpha Radiation?
Low penetrating 4Helium2
What is beta radiation?
Positron or electron emission
How is a positron formed?
The decay of a proton into a neutron and a positron
What is sort of characteristics are wanted when using a radioactive medicine?
The medicine tends to be gamma producing, a half life long enough for target organ examination and low dosage
How are gamma rays detected?
They are detected by gamma cameras that sodium use iodide crystals to respond to gamma rays, which is picked up by light detectors, which are amplified and then transformed into electrical signals.
When is a radiopharmeceutical formed?
Once a radioisotope is combined with a compound of interest to the target organ
How is diseased tissued analysed using radioactive medicine?
Diseased tissue has a greater metabolism, therefore will eat a greater portion of radiopharmaceutical and emits a higher level of a gamma radiation from the area
How does PET scans work?
The injection of a radioactive medicine that produces positrons, a form of beta radiation, which collides with an electron causing total pair annihilation that produces two gamma rays. These gamma rays are then picked up by a ring of gamma sensors, which measure the strength and angle and using known attenuation coefficients, an image can be constructed
PET scans in regard to the brain
PET scan molecule beta D-glucose is one of the few molecules able to pass the blood brain barrier
In endoscopes, what are Non-coherent fibre optic cables used for?
These are used for transmitting light to see
In endoscopes, what are coherent fibre optical cables used for?
These acts as cameras
