Term
| How do x-rays differ from gamma rays? |
|
Definition
| - only in how they're produced: x-rays are manmade, gamma rays are natural |
|
|
Term
| Alpha and beta radiation differ from gamma in that they are... |
|
Definition
| - particulate (have mass and can be weighed) |
|
|
Term
| Gamma radiation and x-rays differ from alpha and beta radiation in that they are... |
|
Definition
| - electromagnetic (non-particulate) |
|
|
Term
| Which type of radiation (alpha or beta) is more penetrative and more damaging? |
|
Definition
|
|
Term
Who discovered x-rays, and when were they discovered?
|
|
Definition
|
|
Term
| Who was the 1st American dentist to use x-rays? When? |
|
Definition
|
|
Term
| How fast do x-rays travel? |
|
Definition
| - 186,000 miles per second (the speed of light) |
|
|
Term
| Characteristics of x-rays |
|
Definition
- non-particulate (no weight, no mass)
- not affected by magnetic fields
- travel in straight lines
- travel as waves
- expose photographic plates
|
|
|
Term
| Describe the dual nature of x-rays. |
|
Definition
wave - can pass through solid objects
particle - have so much energy that they knock electrons out of the way (they do not have mass, but produce results as if they did) |
|
|
Term
| What causes damage from x-rays? |
|
Definition
| - ionization of water (x-ray photons interact w/ water molecules to form ions (H+ and OH-) and free radicals) |
|
|
Term
| An increase in amperage increases the __ of electrons. |
|
Definition
|
|
Term
| An increase in voltage increases the __ of electrons. |
|
Definition
| - force, speed or pressure |
|
|
Term
| How many times does current change direaction (alternate) in alternating current (AC)? |
|
Definition
|
|
Term
|
Definition
| - the production of ions by the removal of outer electrons |
|
|
Term
| What is the amperage used by the UAB SOD? |
|
Definition
|
|
Term
| What is the voltage used by the UAB SOD? |
|
Definition
- 70 kVp (70,000 volts)
- this is the peak voltage; electrons are moving at different speeds, but the fastest ones are at 70 kVp |
|
|
Term
| How any impulses or bursts of radiation occur every second? |
|
Definition
|
|
Term
| What percentage of electrons that hit the target produce x-rays? |
|
Definition
|
|
Term
| On which end of the cathode ray tube is the filament located? |
|
Definition
| - the cathode (negative end) |
|
|
Term
| On which end of the cathode ray tube is the target located? |
|
Definition
| - the anode (positive end) |
|
|
Term
| In a cathode ray tube, is the anode negative or positive? The cathode? |
|
Definition
- anode = positive
- cathode = negative |
|
|
Term
| What type of energy is created by the electrons that hit the target but do not create x-rays? |
|
Definition
|
|
Term
| What type of metal is the filament made out of? |
|
Definition
|
|
Term
| What does a transformer do? |
|
Definition
| - raises or lowers voltage from wall |
|
|
Term
| Which end of the cathode ray tube does the step-up transformer feed? |
|
Definition
|
|
Term
| Which end of the cathode ray tube does the step-down transformer feed? |
|
Definition
|
|
Term
| How many volts enter the cathode ray tube from the wall? |
|
Definition
|
|
Term
| What is the purpose of the aluminum disks covering the lead collimator? |
|
Definition
| - to harden the beam of the x-ray, removing soft x-rays that won't expose film but will needlessly expose patient |
|
|
Term
| How thick are the aluminum disks over the lead collimator? |
|
Definition
|
|
Term
| What device allows for aiming of the beam? |
|
Definition
| - the position indicating device (PID) |
|
|
Term
| What type of material is used to insulate the x-ray tube? |
|
Definition
|
|
Term
| What happens to the overall energy of the beam as it passes thru the aluminum disks? |
|
Definition
|
|
Term
| Trace the pathway of the beam as it leaves the target. |
|
Definition
- passes thru unleaded glass window of x-ray tube
- passes thru tubehead seal
- passes thru aluminum disks
- passes thru lead collimator
- passes thru PID
|
|
|
Term
| What determines the width of the beam? |
|
Definition
| - the diameter of the hole in the lead collimator |
|
|
Term
| What material is the target made out of? |
|
Definition
|
|
Term
| What are the requirements for a target material? |
|
Definition
- high atomic number
- high atomic weight
- high melting point
- low vaporization pressure
- good thermal conductor
|
|
|
Term
| Which of the requirements for a good target material is not met by tungsten, and how is this overcome? |
|
Definition
- it does not meet the requirement of being a good thermal conductor
- a copper stem is attached to funnel heat away from the target |
|
|
Term
| The __ the focal spot, the sharper the image. |
|
Definition
|
|
Term
| What are the dimensions of the actual focal spot? |
|
Definition
|
|
Term
| What are the dimensions of the effective focal spot? |
|
Definition
|
|
Term
| What principle allows for a reduction in size of focal spot (and thus a sharper image)? |
|
Definition
- the line-focus principle
- the target is angled so that the effective focal spot is smaller than the actual focal spot |
|
|
Term
|
Definition
| - area of unsharpness (want to keep it as small as possible) |
|
|
Term
| What helps to reduce the size of the penumbra? |
|
Definition
|
|
Term
| What is the relationship between object to film distance (OFD) and image quality? |
|
Definition
| - the shorter the OFD, the better the quality of the image (sharpness increases and magnification decreases as the distance between the tooth and the film gets shorter) |
|
|
Term
| What is the relationship between target to film distance (TFD) or source to film distance (SFD) and image quality? |
|
Definition
| - as SFD or TFD increases, image quality increases (as SFD or TFD increases, magnification decreases and sharpness increases) |
|
|
Term
| Why is it advisable to have a longer PID? |
|
Definition
| - to increase the TFD/SFD, thereby decreasing magnification and increasing sharpness |
|
|
Term
| What should be the relationship between the position of the film and the position of the tooth? Why? |
|
Definition
- the film and the long axis of the tooth should be parallel
- otherwise, the image will show a distortion of tooth length |
|
|
Term
| What is the unbreakable rule? Why? |
|
Definition
- the beam should be perpendicular to the long axis of the tooth
- otherwise, the tooth length will be distorted |
|
|
Term
| What are the shadowcasting rules? |
|
Definition
- small focal spot
- short OFD
- long TFD
- film and tooth parallel
- beam and film perpendicular
|
|
|
Term
|
Definition
| - "braking" of high speed electrons when they hit tungsten target |
|
|
Term
| How does bremsstrahlung create x-rays? |
|
Definition
- if a bombarded electron (from the filament) passes near the nucleus of a tungsten atom (in the target), it will slow down or stop
- the energy lost by the electron in slowing down is transferred to x-ray energy |
|
|
Term
| In bremsstrahlung, the greater the reduction in the speed of a bombarded electron, the __ the energy of the x-ray. |
|
Definition
| - greater (the complete stopping of a bombarded electron would yield the greatest x-ray energy) |
|
|
Term
| What causes characteristic radiation? |
|
Definition
- a bombarded electron collides with an electron in the K shell of a tungsten atom, ejecting it from orbit
- when electrons in outer orbits slow down to transfer to and occupy the empty K shell, they give off x-ray energy |
|
|
Term
| What is ALWAYS the voltage of x-rays created by characteristic radiation? |
|
Definition
|
|
Term
| What term is used to describe the uniformity of voltage created by characteristic radiation? |
|
Definition
|
|
Term
| To make x-rays from a tungsten target, what voltage should the x-ray machine be set on? Why? |
|
Definition
- 70 kVp (70,000 volts)
- that is how much energy is required to knock an tungsten electron out of its K shell |
|
|
Term
| What percentage of x-ray interaction with human tissue is Thompson/classic/coherent/elastic/unmodified scatter? |
|
Definition
|
|
Term
| How much absorption occurs in Thompson/classic/coherent/elastic/unmodified scatter? |
|
Definition
|
|
Term
| How much loss of energy in the x-ray photon occurs in Thompson scatter? |
|
Definition
|
|
Term
| What percentage of photon-tissue interactions result in compton scatter? |
|
Definition
|
|
Term
|
Definition
| - there is some scatter and some absorption of x-ray photon by human tissue |
|
|
Term
| What is a Compton electron? |
|
Definition
| - an electron from an atom in human tissue that is displaced by an x-ray photon |
|
|
Term
| What happens to the energy of the x-ray photon in Compton scatter? |
|
Definition
| - it loses some energy (but retains some, too) and continues on as a weakened photon |
|
|
Term
| Compton scatter only occurs when an electron is displaced from a(n) __ shell. |
|
Definition
|
|
Term
| What percentage of photon-tissue interactions result in the photoelectric effect? |
|
Definition
|
|
Term
| What causes a photoelectric effect? |
|
Definition
| - the direct hit of an inner shell electron by the x-ray photon |
|
|
Term
| What happens to the inner shell electron in the photoelectric effect? |
|
Definition
| - it is ejected and gives off light |
|
|
Term
| What happens to the x-ray photon in the photoelectric effect? |
|
Definition
| - it ceases to exist, having transferred all its energy to the ejected electron |
|
|
Term
| How much absorption occurs in the photoelectric effect? |
|
Definition
|
|
Term
| What two things can ionization produce? |
|
Definition
| - charged ion pairs or free radicals |
|
|
Term
| How many impulses of radiation are produced in 2/3 second? |
|
Definition
|
|
Term
| What is the difference between x-rays and the rest of the electromagnetic family? |
|
Definition
| - x-rays produce ionization |
|
|
Term
| What unit is used to describe the quantity of the beam? |
|
Definition
|
|
Term
| What unit is used to describe the quality of the beam? |
|
Definition
|
|
Term
| What effect does an increase in amperage (mA) have on an x-ray? |
|
Definition
| - it affects the quantity of the beam, increasing the number of photons |
|
|
Term
| What effect does an increase in exposure time have on an x-ray? |
|
Definition
| - it affects the quantity of the beam, increasing the number of photons |
|
|
Term
| What affect does an increase in voltage (kVp) have on an x-ray? |
|
Definition
- it affects both the quantity and quality of the beam, increasing the number of photons and decreasing their wavelengths
|
|
|
Term
| What effect does aluminum filtration have on an x-ray? |
|
Definition
| - it affects the quantity and quality of the beam, decreasing the number of photons and allowing only those with shorter wavelengths to pass thru |
|
|
Term
| What effect does distance have on an x-ray? |
|
Definition
| - it affects the quantity of the beam: greater distance means fewer photons reach target |
|
|
Term
| An increase in the number of photons results in a(n) __ in film density. |
|
Definition
|
|
Term
| Film density is affected by which variables? |
|
Definition
- all of them (since all of them affect the number of photons reaching the film)
- mA, exposure time, kVp, aluminum filtration, and TFD |
|
|
Term
| Which variables affect the quality of the beam? |
|
Definition
- kVp (directly proportional)
- aluminum filtration (inversely proportional) |
|
|
Term
| Is film density affected by the quality or quantity of the beam? |
|
Definition
- trick question, sucker. it's affected by both.
- increased quantity and increased quality both result in increased density (blackness) |
|
|
Term
| An increase in thickness of aluminum filtration results in __ density. |
|
Definition
- decreased
- even though it eliminates weaker photons, it reduces the total number of photons |
|
|
Term
| Which scale of contrast (long or short) do dentists want? |
|
Definition
| - short (i.e., very white enamel, very dark decay) |
|
|
Term
| Which scale of contrast (long or short) includes many shades of grey? |
|
Definition
|
|
Term
| Which variables affect film contrast? |
|
Definition
|
|
Term
| Low visual contrast is associated with which scale (long or short)? |
|
Definition
|
|
Term
| What effect does an increase in kVp have on contrast? |
|
Definition
| - it produces a long scale (many shades of grey, low visual contrast) |
|
|
Term
| What effect does an increase in aluminum filtration have on contrast? |
|
Definition
| - it produces a longer scale (many shades of grey, low visual contrast) |
|
|
