Radiology Review

What does ALARA stand for?

As Low As Reasonably Achievable

Which extraoral image is best to evaluate facial growth / development, trauma and disease?

a. lateral cephalometric image

b. waters projection

c. reverse towne projection

d. submentovertex projection

a. lateral cephalometric image OR posteroanterior projection

Which extraoral imaging has the forehead and nose touch the receptor?

posteroanterior

An atom has a nucleus made up of?

protons and neutrons

Why does an atom have neutral charge?

it has an equal number of electrons (-) and protons (+)

Where are electrons located in an atom?

around the nucleus orbiting

When an atom gains or loses an electron, they are called?

Ions

The formation of ion pairs is known as?

ionization

What are the two types of ionizing radiation?

particulate and electromagnetic

Which type of ionizing radiation travels in straight lines at high speeds with mass?

a. particulate

b. electromagnetic

c. wavelength

d. Ion

a. particulate

Which type of ionizing radiation travels in wave like energy through space (no mass)?

a. particulate

b. electromagnetic

c. wavelength

d. Ion

electromagnetic

Which extraoral imaging is best to evaluate the maxillary sinus area?

a. lateral cephalometric image

b. waters projection

c. reverse towne projection

d. submentovertex projection

b. waters

Which extraoral imaging is best used to identify fractures of the condylar neck and ramus area?

a. lateral cephalometric image

b. waters projection

c. reverse towne projection

d. submentovertex projection

b. reverse towne projection

Which extraoral imaging is best used to identify the position of the condyles and evaluate fractures of zygomatic arch?

a. lateral cephalometric image

b. waters projection

c. reverse towne projection

d. submentovertex projection

d. submentovertex projection

What are the three characteristics of electromagnetic waves?

wavelength

frequency

velocity

The number of waves that pass at a given point time is known as?

a. wavelength

b. frequency

c. velocity

b. frequency

The distance between two adjacent wave crests is known as?

a. wavelength

b. frequency

c. velocity

a. wavelength

Which type of wavelength has stronger radiation?

a. long

b. short

short

Which is not a property of X-rays?

a. invisible

b. no mass

c. no charge

d. can be focused to a point

e. none of the above

d. can be focused to a point

What houses the x-ray tube?

a. tubehead seal

b. tubehead

c. transformers

d. position Indicating Device

b. tubehead

What controls the voltage of incoming electricity?

a. velocity

b. kVp

c. transformers

d. tubehead seal

transformers

What is the x-ray tube composed of?

a. leaded glass housing

b. insulating oil

c. lead collimator

d. transformer

leaded glass housing and has a nonlead window to allows xrays to exit

What does the cathode consist of? (2)

1. tungsten filament

2. molybdenum focusing cup

What supplies the electrons to produce xrays?

a. anode

b. cathode

cathode

What gets heated to produce electrons?

a. tungsten target

b. tungsten filament

c. molybdenum cup

d. copper stem

b. tungsten filament

What directs the electrons towards the target on the anode ?

a. tungsten target

b. tungsten filament

c. molybdenum cup

d. copper stem

molybdenum cup

What converts electrons into photons?

a. anode

b. cathode

anode (+)

What are two components of the anode?

The copper stem and tungsten target

What stops electrons so energy can be converted into xrays?

a. tungsten target

b. tungsten filament

c. molybdenum cup

d. copper stem

tungsten target

What dissipates heat away from target?

a. tungsten target

b. tungsten filament

c. molybdenum cup

d. copper stem

d. copper stem

What is needed to produce xrays?

electricity

What has low voltage to filament of x-ray tube and generates the source of electrons needed to produce x-rays?

a. filament circuit

b. high voltage circuit

c. transformer

d. velocity

a. filament circuit (3-5V)

What controls the filament circuit?

a. mA

b. kVp

c. exposure time

d. distance

mA

What accelerates the electrons from the cathode to the anode target?

a. filament circuit

b. high voltage circuit

c. transformer

d. exposure time

b. high voltage circuit (65,000-100,000 kVp)

What controls high voltage circuit?

a. mA

b. kVp

c. exposure time

d. distance

b. kVp

What is located in the tubehead to increase or decrease voltager?

transformer

Which transformer heats the tungsten filament to form electron cloud?

a. step down

b. step up

step down (brings from 110 o2 220 V to 3-5)

Which transformer in the x-ray machine is used to increase the voltage from the incoming 110- or 220-line voltage to the 65,000 to 100,000 volts required?

a. step up

b. step down

step up

Electrons that stay in the cloud around the filament until the button is pushed is known as?

thermionic emission

What type of voltage circuit is activated when the exposure button is turned on?

a. high

b. low

high voltage circuit

When the electrons strike the tungsten target, what is converted?

1% xrays

99% heat

What restricts the side of x-ray beam?

a. aluminum filter

b. lead collimator

c. copper stem

d. PID

b. lead collimator

Where do x-rays exit?

tubehead at opening PID

What are the different interaction of x-rays?

1. no interaction

2. coherent scatter

3. photoelectric effect

4. Compton effect

Which type of scatter is only 8% and goes in different direction than original?

a. no interaction

b. coherent

c. photoelectric effect

d. Compton

coherent

Which type interaction of xray is absorbed and vanishes?

a. no interaction

b. coherent

c. photoelectric effect

d. Compton

photoelectric effect (30%)

Which type of interaction accounts for most of the scatter radiation?

a. no interaction

b. coherent

c. photoelectric effect

d. Compton

Compton (62%)

What determines the quality of xrays? Select all that apply

a. kVp

b. exposure time

c. mA

d. distance

kVp

What determines the speed of electrons?

a. kVp

b. exposure time

c. mA

d. distance

kVp

A shorter wavelength has more penetrating power and a _________ quality beam.

higher

Dental radiography uses what range of kVp?

65-100 kV

What does kVp affect?

contrast and density

True or False: mA controls the penetrability of the beam.

false, kVp does

The overall darkness of an image is known as?

density

Increase kVp = _____ density

increase

A decrease in KVp = _____ density

decrease

The difference in dark and light areas is known as?

contrast

Low kVp (65-70) = _________ contrast

high

High kVp (>90) = __________ contrast

low

Which type of contrast is better for detecting periodontal disease due to long scale contrast?

low contrast **also periapical disease

Which type of contrast is better for detecting caries due to short scale?

high contrast

Low contrast has which type of scale?

long

High contrast has which type of scale?

short

If kVp is increased what should occur with the exposure time?

a. increased

b. decreased

c. no change

b. decreased

What determines the number of electrons passing through the cathode filament?

a. kVp

b. exposure time

c. mA

d. distance

c. mA

What affects the quantity of x-rays? Select all that apply

a. kVp

b. exposure time

c. mA

d. distance

ma and exposure time

Increased mA = _______ density

increased darker image

Decreased mA = ________ density

decreased lighter image

If mA increases, what should be done to exposure time?

a. increase

b. decrease

c. no change

decrease

If you have a higher kVp = __________ intensity of beam

increased

If you have higher mA = _______ intensity of beam

increased

If you increase exposure time = ________ intensity of beam

increased

If you increase distance = ________ intensity of beam

decreased (less intense on skin)

According to the inverse square law, when distance is doubled, the beam _______ as intense.

1/4

According to the inverse square law, when distance is halfed

, the beam _______ as intense.

4x more

The thickness of material that , when placed in the path of x-ray beam, reduces the exposure rate by one-half?

half value layer

Sharpness is influenced by which three factors?

focal spot

film composition

patient movement

Which size focal spot will produce more sharpness?

smaller

Which crystal size will produce more sharpness?

smaller

Magnification is increased by which two factors?

1. short PID

2. increased object to receptor distance

Variation from true size or shape of object being imaged is known as?

a. sharpness

b. distortion

c. magnification

d. movement

distortion

What influences distortion? (2)

-object-receptor alignment (must be parallel)

-x-ray beam angulation (must be perpendicular)

Which types of effect occurs by chance and has direct function of dose?

a. stochastic effect

b. indirect effect

c. nonstochastic effect

d. direct effect

a. stochastic effect

Which type of effect is where severity increases w dose rate ?

a. stochastic effect

b. indirect effect

c. nonstochastic effect

d. direct effect

nonstochastic

Which effects gives rise to skin erythema,, hair loss and cataract formation due to large dose in small amount of time?

a. stochastic effect

b. indirect effect

c. nonstochastic effect

d. direct effect

c. nonstochastic effect

What are the two types of radiation injury?

Ionization and free radical formation

When ionizing radiation directly hits a cell and happens infrequently it is known as?

a. stochastic effect

b. indirect effect

c. nonstochastic effect

d. direct effect

direct

When photons gets absorbed and ionize water forming toxins which damage the cells and occurs more frequently is known as?

a. stochastic effect

b. indirect effect

c. nonstochastic effect

d. direct effect

indirect effect

What is the most common type of cell damage in humans?

a. ionization

b. free radicals formation

b. free radicals formation

List radiosensitive cells (6)

1. blood cells

2. bone marrow

3. reproductive cells

4. skin

5. intestinal /oral mucosa

6. lens of eyes

list a radioresistant cell: (7)

1. mature bone

2. nerve

3. muscle

4. salivary glands

5. thyroid gland

6. kidney

7. liver

For an occupational worker, what is the maximum permissible dose?

5 rem/per (5000mrem) or 0.05 Sv/year (50mSv)

For a non-occupational worker, what is the maximum permissible dose?

0.5rem/yer (500mrem) or 0.005 Sv/yer ( 5mSv)

What restricts the size and shape of an xray?

collimator

What filters out long wavelengths?

aluminum disk placed between collimator and seal

How much aluminum filtration must be in the x-ray tube to meet government standards?

2.5mm

Which type of filtration is already in the machine ?

a. inherent

b. added

c. total

inherent

True or False: A long PID and rectangular shape will decrease radiation exposure.

True

Which type of imaging uses PSP plates?

a. direct digital imaging

b. indirect digital imaging

c. panoramic

d. occlusal

b. indirect

What is the vertical angulation for bitewings?

+10 degrees