National Board Review: Radiology

What are X-rays?

weightless bundles of energy (photons) with no charge

What is ionization?

the ejection of an electron from an atom

What is AC electricity?

the movement of electrons along a wire to a positive charge

What is MA?

describes the number of electrons flowing through the machine

If you increase the mA what else do you increase?

increases the number of photons and the density of the film

What is voltage?

describes the potential difference between the cathode and the anode, the speed of the electrons moving toward the anode

If you increase the KVP what else increases?

increase the number of photons generated, increase the density of the film, and will increase the penetration power

What is exposure time?

the interval of time during which X-rays are being produced

What happens if you increase the exposure?

it will increase the number of photons and will increase the density

One second equals how many impulses?

60

What is distance?

the X-ray beam spread as the distance from the unit increases

What happens if you increase the distance?

it will decrease the number of photons and the density of the film

What does filtration do?

it absorbs weak long wavelengths

What happens if you increase the filtration?

it will decrease the number of photons snd will also decrease the density of the film

What does filtration improve?

the quality of the and penetration of the X-rays

What is a cathode?

it is a negative electrode that supplies the electrons necessary to generate X-rays

What is the cathode made of?

made of tungsten filament and molybdenum cup

What are electrons?

tiny negatively charged particles with very little mass

How do electrons travel?

travel from the negative cathode to the positive anode

What is an anode?

positive electrode that converts electrons into X-ray photons

What is anode made of?

made of tungsten and copper stem

What is quantity affected by?

mA, kVp, time, distance, and filtration

What does quantity of the beam mean?

the humber of X-ray photons given off a period of time, how strong the beam is

What does quality of the beam mean?

the penetrating power of the X-rays

What is quality affected by?

kVp and filtration

What does density mean?

the overall blackness of a film

What is density affected by?

mA, kVp, exposure time, distance, and filtration

What does contrast mean?

how sharply the dark and light areas on a film are

What is contrast affected by?

kvp and filtration

A short scale of contrast means what?

mostly black and whites

A long scale of contrast means what?

many shades of gray

What is the slob rule?

lingual objects move in the same direction as the tube head but buccal objects move in the opposite direction of the tube head

What is the inverse square law?

the intensity of radiation is inversely proportional to the square of the distance from the source of the radiation

What is film emulsion?

silver halide bromide crystals on both side of the film

What is developer?

elon and hydroquinone, it turns only exposed crystals to metallic silver

What is fixer?

sodium thiosulfate, it removes undeveloped crystals

What causes discolored film?

exhausted fixer or poor replenishment, after time, problem is because of poor wash

What is hydrolysis?

water is broken into free radicals which are unstable and highly reactive

What type of tissues have increase sensitivity to radiation?

1. rapid turnover or mitosis rate of cells
2. undifferentiated ce;;s

Why are kids more sensitive to radiation?

because of rapid cell mitosis associated with growth

What is the latent period?

the time between the X-ray exposure and the appreciate of symptoms

What are somatic effects of radiation?

are only seen in a person irradiated- not passed to an offspring

What tissues have the highest sensitivity to radiation?

1. reproductive tissues is #1
2. lymphoid tissue
3. down marrow
4. intestines
5. mucous membranes

What tissues have the lowest sensitivity to radiation?

1. nerve tissue #1
2. skeletal muscle
3. optic lens
4. heart
5. mature bone and cartilage

What is the old unit of exposure in air?

roentgen

What is the SI unit of exposure in air?

coulomb/Kg

What is the old unit of absorbed dose?

Rad

What is the SI unit of absorbed dose?

Gray

What is the old unit of dose equivalent?

Rem

What is the new unit of dose equivalent?

Sievert

What is the maximum permissible of dose for occupational workers?

1. 5 rem/year
2. 0.05 Sv/ year

What is the maximum permissible dose of non occupation workers?

1. 0.1 rem/year
2. 0.001 Sv/year

How should you determine when one person needs X-rays?

radiographs should be ordered on an individual basis after historical and clinical examination of the patient

What is the most effective meths of radiation protection?

film speed

What is film speed?

each alphabetical film group if 2 times after than the previous film group and needs half as much radiation exposure

The dose of one panoramic X-ray is about the same as how many bitewings?

4 bitewings

What helps protect patients from radiation in a panoramic X-ray?

the intensifying screen

What does collimation do?

helps reduce the scatter

A beam size can be larger than what at a patients face?

2.75 inches

Is a rectangle collimator better than a circle collimator?

a rectangular collimation is better and reduces exposed about 60%

How far should the operator stand away from the scatter source?

6 feet

At what angle should the operator stand from the beam?

90-135 to the beam

How much beam does the lead apron absorb?

90%