That energy can neither be created or destroyed. It can only be coneverted from one form of energy to another .
Are members of the same element with:
-same number of protons
-different number of neutrons
-different mass numbers
Acceleration = change of velocity over change of time
Velocity = distance over time
1- An object will not change its motion unless a force acts upon the object.
2- The force acting on an object is equal to the mass of that object times its acceleration F=ma
3- For every action, there is an equal and opposite force
Only transverse waves
-when a wave travels from one medium to another, part of the energy is passed on and part is reflected.
The angle of incidence is = to the angle of reflection
-When a transmitted wave is deviated from the direction of the incident wave
-The change of direction is called refraction
-the intesity of radiation is inversely porportional to the square of the distance
-the more distance is increased, the intesity of the radiation will decrease porportionally to the square of the distance increased.
The average energy flowing through a unit area per unit time
E = hf
photon energy = (Planck's constant) x (frequency)
-Sound of frequency above the threshold of human hearing (20kHz)
-Scans density of materials and the speed of sound in that material
Energy in transit in the form of high speed particles or electromagnetic waves
-breaks chemical bonds in the body, leading to damage to DNA
Can interact with atoms or molecules in the cell to produce highly reactive free radicals, this diffuses and causes damage to DNA
-can cause mutations in DNA, causing problems later
-daughter cells may reproduce in a uncontrolled way and lead to cancer later in life
Biological effects in any tissue are proportional to the amount of energy absorbed per unit mass of tissue
different radiation have different biological effects for the same amount of energy absorbed
Different organs of the body are assigned tissue weighting factors, to represent the different sensitivity of each organ to radiation damage
-heat disperses over a larger suface area (preserving the x-ray tube)
-higher heat cpacity
-can be used for longer exposure and larger body parts
-larger focal area
Not suitable for mobile x-rays
-too bulky, not simple or easy to move around
Reducing scatter and enhancing the contrast of the image
It will magnify the image and reduce scattering
2. air gap techinque
-reduces the tissue thickness
-reduces patient movement (reduces motion)
-makes tissue more evenly distributed
-evens the brightness of the image
The tissues inside the breast are very similar, adeqaute contrast allows us to distinguish the different tissues.
Thermistors are dependent of temperature. To change resistance with the changes of temperature.
-beam limitation device (collimation)
-air gap techinque
-air gap technique
-need to increase the exposure (because distance is increased)
- more radiation is emitted
-distortion of the image
-Limits the area exposed to x-ray photons
-Contains the filter which filters out low energy photons (which has no contribution to the image quality, but will increase patient dose)
Interaction between an incident x-ray of energy and an atom in the material
-no energy is lost in the process to an atom
-purely just scattering
-occurs at low energies (below 30kVp)
The interaction occuring is inversely proportional to the incident energy and proportional to the square of the atomic number
-the likely hood also depends on the energy of the incident x-ray and on the atomic number, Z (dependent on Z).
-the x-ray changes direction (is scattered) and has less energy than the incident x-ray, hence a longer wavelength.
by the conservation of energy:
the incident energy must be divided between kinetic energy of the recoil electron and the scattered x-ray
(E)incident = (E)scattered + (E) ecoil electron
-stores energy to use later, accumulates on one plate and relases on another plate
-smoothens the variation of the current
-maintains voltage at the same level
like a battery it stores energy. Although it can charge up quicker and release energy faster than a battery. Generally a capacitor has two plates, accumulating energy on one plate and releasing energy on another plate.
-electronic noise filtering
When the electron moves extremely close to the nucleus, decelerates and changes direction, converting kinetic energy into electromagnetic radiation.
when the incident electron stikes a atom bound electron, the bound electron is ejected from the inner shell of the atom. The incident electron is also deflected off an angle. A higher shell electron will replace this vacancy, and energy is released to compensate - this energy is called characteristic radiation.
The energy produced is dependent of the number of protons and the difference between binding energies- so the same atoms will have the same energies.