RT 131 CH 4 + 7 Review Flashcards

What do xrays. gamma rays, visible light, and radiofrequency have in common?

They're all electromagnetic energy

The smallest quantity of any electromagnetic energy that has no mass or charge and travels at the speed of light is called ___.

photon

Photons travel through space at the speed of light in ____.

sine waves/sinusoidal fashion

Although all photons travel at the speed of light in sine waves, what makes each type of photon on the electromagnetic spectrum different from one another?

Frequency, wavelength, and energies

The velocity or “speed" of all electromagnetic energy is ___.

3 × 10^8 m/s or 186,000 mil/s

The height or vertical distance from the halfway point between crest and valley of a sine wave is known as ___.

Amplitude

The speed or how fast or slow a sine wave moves per second is known as ___.

Velocity

The # of wavelengths that pass a point of observation or rate of rise and fall of a sine wave per second is known as ___.

Frequency

The distance from one crest to another crest, or from valley to another valley, or any point on wave to another corresponding point is known as ____.

Wavelength

As the frequency of electromagnetic energy increases, the wavelength ____

decreases

As the wavelength of electromagnetic energy descreases, the frequency ____.

increases

What does the wave equation state?

Since velocity is constant amongst all electromagnetic energies, it depends on the fluncuations in frequency and wavelength

As the frequency of a sine wave increases, their energy level ___.

increases

As the frequency of a sine wave decreases, their energy levels ___.

decreases

Which regions in the electromagentic spectrum are important to radiology?

visible light, xray/gamma radiation, and radiofrequency

Which modality in radiology is not on the electromagnetic spectrum?

Diagnostic ultrasound

Which region on the electromagnetic spectrum has higher energy and frequency, but smaller wavelengths?

Gamma rays & xrays

Which region on the electromagnetic spectrum has relatively low energy and a long wavelength?

radiofrequency

Which portion on the electromagnetic spectrum are we able to sense directly?

visible light

Which portion of the electromagnetic spectrum is responsible for molecular interactions that cause sunburns?

ultraviolet light

Telephone communication, highway speed monitoring, and medical diathermy use ___.

microwaves

Define polyenergetic

Having wide range of energies

The intensity of the beam or # of photons is controlled by ____.

mAs

The quality of energy from the beam is controlled by ____.

kVp

Visible light is identified by its ___.

wavelength

T/F: Green has a longer wavelength than red

False

T/F: Visible light deviating from line of travel is known as refraction

True

T/F: Infrared has a higher frequency than visible light

False

Where does ultraviolet lie on the electromagnetic spectrum?

Above visible light

The only difference between xrays and gamma rays is their ___.

origin

Where do xrays come from?

Orbital shell of an unstable atom

Where do gamma rays come from?

The nucleus of an unstable atom

What is the main objective with the wave-particle duality?

Xrays and visible light exhibit behaviors of particles and waves

Although xrays and visible light are fundamentally the same, their different ___ and ___ results in differences in the way these photons interact with matter.

frequencies; energies

Anything above UV light on the electromagnetic spectrum behaves like ____.

particles

Anything below UV light behaves more like ____.

waves

T/F: Photons interact with matter most easily when the matter is approximately the same size as the photon wavelength

True

Define attenuation

Reduction in intensity/# of xrays resulting from scattering and absorption

What is the key idea with inverse square law?

The intensity of electromagnetic radiation is inversely related to the square of the distance from the source

According to inverse square law, the closer the source is to the beam, the intensity ____.

increases

What are three ways an object can attenuate?

Transmission (not at all), attenuation (partially), absorption (completely)

Structures that absorb xrays are called __.

Radiopaque

Radiopaque structures include ___.

Bones, metal, lead

Structures that trasmit xrays are known as ____.

radiolucent

Radiolucent structures include ___.

Air, soft tissue, lung tissue, muscles

According to Planck's quantum theory, the energy of a photon is _____ to its frequency.

directly proportional

What is Planck's quantum equation?

E = hf

What are the three external components of the xray tube?

Support system, protective housing, enclosure

What are the two internal components of the xray tube?

cathode and anode

What is the primary function of the protective housing?

Prevent leakage radiation

How does the protective housing prevent leakage radiation?

By blocking excess isotropically xrays from leaving lead-lined structure

What the oil in the protective housing do?

Dissipate heat from tube and insulates against electric shock

What is the protective housing protecting?

Cathode and anode enclosed in glass

Glass enclosures are made of ____ to withstand tremendous amounts of heat.

Pyrex

The glass enclosure maintains a vacuum seal to allow for what?

more efficient xray production and prolonged tube life

According to federal law, any leakage radiation must be less than ____ at 1 m.

1 mGya/hr

What is the most common cause of tube failure?

tungsten filament vaporizes and deposits inside of glass/metal enclosure

How much heat and xrays are generated in the glass enclosure?

99% heat, 1% xray

The cathode is ____ charged while the anode is ____ charged.

negatively; positively

What two components make up the cathode?

Filament and focusing cup

Describe the form and function of a filament

Coiled wire made of thoriated tungsten that boils off and emits electrons to anode

Describe form and function of the focusing cup

Negatively charged metal shroud made of either molybdenum or tungsten that houses the filaments and confines electron beam to small area of the anode

Define thermoionic emission

Outer shell electrons in filament are boiled off and ejected out

Why is the filament usually made of tungsten?

Tungsten has a higher melting point and doesn't vaporize quickly

Define space charge effect

After electrons are boiled off at the filament, they're momentarily held in a cloud or cluster in focusing cup before being propelled to anode

If the mAs is 400 or more, and the part is larger, the ___ filament is needed to withstand the heat to penetrate through.

larger

If the mAs is 300 or lower, and the part is small, the ____ filament is needed for spatial resolution on finer details.

smaller

Selecting a lower mA will propel the electrons to the smaller filament to hit a ____ focal spot.

small

Selecting a higher mA will propel the electrons to the large filament to hit a ___ focal spot.

bigger

The small actual focal spot measures about ____.

.1 mm to 1 mm

The large actual focal spot measures about ____.

.3 mm to 2 mm

What is the difference between actual and effective focal spots?

Actual focal spots are the physical area on the anode target where the electron beam hits

Effective focal spots are the projected onto the patient and image receptor

The positively charged portion of the xray tube is the _____.

anode

Do diagnostic xray tubes use stationary or rotating anodes? Why?

Rotating anodes are used to produce high-intensity beams in a short time

Name the 3 functions the anode serves in the tube

1. Electrical conductor - directs electrons emitted from cathode and conducts them through tube

2. Mechanical support for target

3. Thermal dissipator - dissipates heat

Which machines use stationary anodes?

Dental xray imaging systems

What materials make up the anode?

Target - tungsten

Base - graphite, molybdenum, copper

Why is the base of the anode made of graphite, molybdenum, or copper?

They have a lower mass density, which allows for better rotation

Why is the target of the anode made of tungsten?

Tungsten has a heavier mass density to withstand high-speed rotations and thermal changes

What is the target on the anode?

The area of the anode struck by the electron beam from cathode

How is he base of the anode able to rotate?

Through electromagnetic induction from induction motor

The induction motor consists of two parts: the series of electromagnets on the outside the enclosure called ____ and the ferromagnetic ___ inside the enclosure.

stator; rotor

How are the magnets on the stator arranged?

Equally spaced

How does the induction motor rotate the target?

Electromagnets on the stator induce a magnetic field around rotor. The magnets are charged sequentially so that the magnetic field interacts with the rotor, causing it to rotate

What is the line-focus principle?

By angling the target, the effective focal spot becomes smaller than the actual focal spot

When the target angle is smaller, the effective focal spot gets ____.

smaller

Diagnostic xray tubes have target angles that vary from __ to ___ degrees.

5 to 20

Greater target angles, making smaller focal spots, improves ___.

spatial resolution

What is the main consequence from the line-focus principle?

anode heel effect

What is the anode heel effect?

Radiation intensity is high on the cathode side of xray field than anode side because more photons are absorbed in anode heel

What usually causes the heel effect?

Small target angle