Download 2005Su Radiology Test 1 Review

Radiology Test 1 Review
1. Occurs when x-ray photon transfers its energy to an orbital electron …is?
Ionization
2. Number of proton is? Atomic #
3. Radioactivity?
Atoms exist in an abnormally excited state
Emits particle
Transform itself to another atom
4. Plank’s Quantum theory? Photons are created at a constant velocity or not at all
5. Photons or quantum?
Electromagnetic radiation exist as small fragments or
particles of energy
6. Wavelength? Distance from one peak to another, measured in cm or meters or
angstroms (A)
(W = velocity/frequency)
7. Frequency? # of alternations per second.
Frequency of X-ray = (10)19
Radio-ray = (10)8
8. Higher frequency or shorter wavelength------- higher energy
9. Inverse square law? Electromagnetic radiation decreases with the decrease
from the source.
I1/I2 = (d2)2/(d1)2
10. What is the most common way to evaluate the x-ray photons?
Is by the amount of the energy they possess.
11. X-ray unit? Is angstrom
12. What permits passage for X-ray? Radiolucent (dark area on radiograph)
13. What prohibits --------------------? Radiopaque (white areas----------------)
14. X-ray? Highly penetrating and invisible
Electrically and magnetically neutral
Heterogeneous or poly-energetic
Travel in straight lines and diverge from their sources
15. Types of X-ray?
Diffraction: 10 kev. Used for research and analysis
Grenz: 10-18
____________ dermatology
Diagnostic: 30-150 keV ________ image
Superficial: 50-100 kev _________ Therapy
Orthovoltage: 200-300 __________ therapy (not good)
Electricity: True/False and Mating
1. E-current? The Flow of e- through conductor
2. Conductor? (copper wire) allow e- flow easily
3. Insulator?
(Glass, Rubber) Inhibits the e-flow
4. Resistance? (measure in ohms) Atom’s tendency
V = IR
5. Voltage? The potential or “pressure”…
6. Anode? The + pole w/deficiency e7. Cathode? The – pole w/excess e8. How e- goes? From A --- C (- to +)
9. How can e- be boiled off of Cathode? By heating
10. Watt? E-power (1w = one amp)
11. Direct current (DC): True/false
E-flow 1 direction
Never down to (-)
Can be steady or fluctuate
12. Ripple free? = constant potential—no fluctuation
13. Alternating current (AC): = Household current
E-flow different direction
14. What is Heat Unit? Used to determine the heat generated by the anode of X-ray
15. E-magnetic field? Physical relationship between electricity and magnetism
16. Magnetic field exists without current flowing? NO
17. Solenoid? A coil of wire -- produce magnetic field
18. What law is applied to “An e- current will be induced to flow in a circuit if
some part…magnetic field”? Faraday’s law = 1st law of e-magnetic induction
19. Which of the following is not applied to magnitude of induced current?
Strength, velocity, angle of conductor and number of turns in conductor = All
20. What are the purposes of tube?
Boil e- from filament (mAs)
Accelerate e- from Cathode to Anode (kVp)
21. Rectifier? A divide that changes AC to DC
22. Transformer? A divide that increase or decrease voltage
23. Does filament circuit have high voltage and low current? Yes
24. Is there e- connected between 2 coils? No
25. Step up transformer: > 1
Increases V
Decreases Amp (current)
No change frequency
26. Step down transformer: < 1 Opposite
27. What are the functions of Autotransformer?
-
Provide V for the X-ray tube filament circuit
-
Primary of the high-voltage transformer
-
Suitable voltage for subsidiary circuit
-------------------------- Convenient location for kVp…
28. Rectification? Process of changing AC – DC
“All X-ray machines must rectify AC b/c X-ray tubes only operate on DC”
29. Diode? E- device that allow current flow in 1 direction
--- 2 types? Vacuum and solid state
30. Vacuum diodes? Has e- source (cathode) and target (anode)
31. Solid state diodes? Are made of silicon or germanium semiconductor
32. Self-rectification? Used no diodes
33. Is self-rec popular in the US? No
34. Half-wave rectification? Is placed in AC, (by eliminating ½ impulse, lose ½
energy of original AC current)
35. Full-wave rectification? Is installed to avoid loosing ½ of pulse
36. How can you prepare to prevent of losing ½ pulse? Install rectifier bridge
37. What is ripple factor? Variation in the voltage across the X-ray tube …
38. 3 phase Machines (triple phase)?
 to decrease the ripple factor
 short exposure time
 X-ray is produced a higher average energy & more uniform
 produced more heat in the tube, so high speed anodes must be used small
ripple
39. High frequency machines: good
---- uses single source
---- uses capacitors to store e---- generate pure DC
Almost no ripple
X-ray machines: test
1. Purpose? Converts potential energy  e-magnetic energy
2. Is there high electric potential (voltage) created between cathode and Anode? Yes
3. Free e- is produced by ---- at the anode? High amperage
4. What cause free e- to accelerate across the gap? High voltage
Anatomy of X-ray tube
1. Casing (tube housing): keeps scatter radiation from leaking out
2. Insulating oil: insulates e- and cool the tube
3. Glass envelope: to contain the vacuum
--- prevent air
--- prevent oxidation
4. Window: made of thinner glass than the rest of the tube
5. Cathode: Negative terminal
---- What are component of Cathode? Filament & focusing cup
6. Filament: source of e---- What is component of the Filament? Tungsten and 1%-2% thorium
7. What is focusing cup? Made up by Nickel, has strong negative charge
8. Anode? (Anti-cathode) positive terminal
9. What are functions of Anode?
--- Receive e-,
--- Is an e- conductor,
--- provides mechanical support and
--- emits X-rays
10. What are the types of anode? Stationary and rotating
11. What is a stationary anode?
--- consist of Copper cylinder
---- Target = Tungsten
12. How X-rays are produced?
--- E- from Cathode strike tungsten (target)
13. Why using tungsten as a target? b/c high atomic #  high melting point
14. Is stationary limited? Yes, b/c e- strikes only 1 area
15. Rotating Anode? Invented 1929 and made up of a disc of Molybdenum
16. What are advantages of rotating anode?
--- Greater capacity/ b/c it rotates around
--- The larger anode the greater heat capacity
X-ray circuit: primary and secondary
1. Primary? Is low voltage
- main switch: power is on and off
- fuses: are used to prevent equipment or tube damage
2. what is tube circuit?
--- provide the e- potential
3. Is high voltage low amperage, faster e-  higher energy X-ray photons
produced? Yes
Time and exposure switches (primary circuit)
1. What is the most common type of timer? E-timer (accurate)
2. Impulse timer? Measure impulse instead of time
3. mAs timer? E-measure
4. Automatic exposure control (AEC): 2 types
--- uses radiation detector  measure amount of radiation…
a. What is Ion chamber? Placed between grid & front of cassette, - radiolucent to xray
b. What is photo-detector? Either in front or behind cassette, - less expensive
5. What is the name to determine accuracy timer? Spinning Top Test
6. Filament circuit? Provides the thermal energy
--- low voltage, high amperage
--- more current go through filament  more e- boiled off  more X-ray are
produced
Secondary circuit: coil of the step-up transformer
1. What is milliampmeter? Used to measure tube current
2. Filament ampmeter? Used to measure filament circuit
3. mAs meter? Measures mAs values at short time intervals
Control of X-ray tube:
4. kVp? Control amount of kinetic energy --- quality of radiation
5. mA? Control amount of current
6. Exposure time? Control amount of time…
5+6 = mAs (b/c they affect the quantity of X-ray)
Bremsstrahlung:
1. what is bremsstrahlung? Brems, general, braking or white radiation
 higher atomic #  the higher energy of X-ray
2. How can you make X-ray more energetic? Frequency
Special effects in X-ray Tubes
1. Space charge effect? E-are emitted,
---- causes a decrease in amount X-ray being produced
2. Heel effect? Test
--- Cause by absorption of radiation in the heel of the anode & angle of anode
---- Smaller angle  more absorption (greater heel effect)
---- Shorter distance from tube – film  greater hell effect
 This effect can be eliminated by wedge filter
a. Heel effect creates what? Cathode side of the beam shows decrease image
clarity
3. Off-focus radiation? Caused by rebounding eCause very large low intensity X-ray source (patient dose ,
film fog)
4. Filtration? Removes soft or low energy X-ray
Heat generated at the Anode:
1. Convection? The oil around the tube being air cooled
2. Conduction? Heat at the anodes travels…
3. Radiation? Heat at the anode being emitted by infrared radiation
4. Ways to control heat?
 Use high kVp-low mAs
 Use tube rating chart
 Heat unit
 Use Anode cooling curve
 Use smaller anode angle
 Use graphite backed anode
5. Heat unit? HU = kVp x mAs (Watts/sec)
X-ray tube failure
1. Filament evaporation? Most common cause of X-ray tube failure
-- Responsible for older tube “shoot lite”
-- Caused by an increased resistance…tungsten evaporation away
2. Spark over and puncture of glass envelope? Caused by Tungsten coating
 more common at high kVp and mA exposure factor
2. Excessive anode temperature?
 Causes localized surface melting or pitting to occur
 Reduced radiation output
3. Rapid increase in anode temperature?
 Occurs in a single exposure when the anode is cold (w/high mA factor)
Bremstrahlung radiation
 Positive charge on nucleus – acts on negative charge of electron
 E- Is attracted toward nucleus – then deflected from its original direction
 Braking radiation results in a wide distribution in the energy of the radiation
Characteristic Radiation? Interaction between incident e- and inner shell e- of target
1. The incident e- impact on what? K-shell orbital
2. Orbital e- is ejected w/energy = to ----? of the incident e- energy from the binding
energy of the K-shell e-? the difference
3. What fills X-ray vacancy? Cascading L-shell
X-ray interaction with matter : Know this
1. Attenuation? Loss of X-ray photon as X-ray passes through matter
 Caused by : absorption , scatter, distance
2. What is classic scattering? Rayleigh scatter, Thomson or unmodified scatter
 Occurs when low energy X-ray strikes an orbital e- & causes it to vibrate
 No changed energy, frequency and wavelength
3. What is Photoelectric effect? Interaction between an incident e- or X-ray photon
and inner shell e- of target atom
 Is the basis for subject contrast?
 E-Is rejected from the Atom becomes a photoelectron
4. Subject Contrast:
 greater kVp – lower contrast
 greater atomic # -- greater absorption
 greater the tissue density – greater the differential absorption
5. What is Compton Scatting?
 Occurs when an incident X-ray strikes an outer shell…
 Loss energy (not useful for image)
 E- is ejected from the atom and becomes Recoil electron
- Almost all the scatter radiation in diagnosis radiology from Compton scattering
6. How the energy of the incident photon is distributed?
 part – recoil e rest – deflected photon
7. The incident photon must be much greater than the binding energy of e-? True
8. All e- in the soft tissues may be involved in Compton scattering? True
9. What is positron? + charged electron , form of antimatter, will exist until it meets
another form of matter
10. What is Annihilation reaction? Both particle mutually destroy each other
11. Why photoelectric effect is most important for diagnosis radiology?
 b/c it is responsible for differential absorption & subject contrast
12. Why Compton effect is important?
 b/c it is responsible for creating scatter radiation
13. What type of Scatter produces fog on a film if no filtration is used to remove low
energy?
 Coherent or unmodified scatter (Classis)
14. Pair production and photodisintegration are of no importance in diagnostic
radiography? True
Test 1 question:
1. Heel effect creates what…?
 Cathode side shows a Decrease in image clarity
2. Compton interaction occurs when?
 between X-ray photon
3. Most modern X-ray tubes utilize…which characteristic?
 Rotating anode
4. Which…represent an X-ray interact with matter?
 Thomson Scatter
5. Which of the following… represent electrons interaction with matter?
 Characteristic and Bremstrahlung
6. The probability of a photoelectric interaction increase when?
 Photoelectric and K-shell
7. Which of … changes energy?
 kVp
8. Which of … changes subject contrast?
 Photoelectric
9. A diode is used?
 Rectified
10. Transformers require…what?
 AC
11. The photoelectric interaction increase energy when?
 Photon energy = K-shell binding