Particles and Medical Physics Flashcards
What is Capacitance and its equation?
Capacitance is defined as the charge stored per unit potential difference across it.
= charge
Potential difference
Two or more capacitors in series rules
Capacitance = 1 = 1 + 1
C C1 C2
Charge stored by each capacitor is the same
Potential difference = V= V1 + V2
Two or more capacitors in parallel
Capacitance= C= C1 + C2
The potential difference across each is the same
Charge Q= Q1 +Q2
What is the area under a p.d. Charge graph
Energy stored
Energy stored by capacitor 3 equations
W=0.5 x QV
W= 0.5 x Q^2
C
W= 0.5 xV^2 xC
What is Exponential decay
Exponential decay is a constant-ratio process in which a quantity decreases by the same factor in equal time intervals
What is electric field strength
Electric field strength is the force experienced per unit positive charge at that point
Electric field strength equation
E=F
Q
Coulomb’s law
Any two point charges exert an electrostatic (electrical) force on each other that is directly proportional to the product of their charges and inversely proportional to the square of their separation.
electrostatic force equation for the force between two point charges
F= Qq
4πε0r^2
What is the value of epsilon-nought ε0
8.85x10^-12
X-ray
This is a short wavelength and high frequency electromagnetic wave (10^-8m to 10^-13m), which can be used in medical imaging
Thermionic emission
This is the emission of electrons from the surface of a heated piece of metal or a hot metal wire
Attenuation
This is the decrease in the intensity of electromagnetic radiation as it passes through matter and /or space. Bone attenuates x-rays more than soft tissues
Simple Scatter description
The x-ray photon is scattered elastically by an electron 1-20 keV
Photoelectric effect
The x-ray photon disappears and removes an electron from the atom. <100keV
Compton effect
The x-ray photon is scattered by an electron, it’s energy is reduced, and the electron is ejected from the atom. 0.5-5.0 MeV
Pair production
The x-ray photon disappears to produce an electron-positron pair >1.02MeV
Basic structure of an X-ray tube components
Heater (cathode), target metal (anode), high voltage power supply,
What is a medical tracer
This is a radiopharmaceutical that is a compound labelled with a radioisotope that can be traced inside the body using a gamma camera
Ultrasound
This is a longitudinal wave with frequency greater than 20kHz
Ultrasound transducer
This is a device that emits and receives ultrasound
Piezoelectric effect
The production of an electromotive force by some crystals, such as quartz, when they are compressed stretched, twisted or distorted
Acoustic independence
This is defined as the product of the density of a substance and the speed of ultrasound in that substance