Intro to Radiography Ch. 1-2

kVp adjusts ______________

frequency

Scatter radiation is created how?

a portion of the xray photon's energy is absorbed

What is the primary source of exposure to techs?

scatter radiation

What does scatter radiation do to the image?

causes a "fog"

What are the four prime factors of radiographic exposure?

exposure time

mA

kVp

SID

The 4 prime factors of radiation exposure contribute to the _____________ and _____________ of radiation that strikes the IR. It affects the ???

quantity and quality

image quality

Exposure time

how long exposure continues

mA + exposure time determines the ____________ quantity of radiation that will be produced

total

If you want to change the quantity of radiation exposure, which factor do you vary?

exposure time

Patient dose is (directly/inversely) proportional to exposure time.

directly

Higher exposure time = more xrays = (darker/lighter) image?

darker

Lower exposure time = fewer xrays = (darker/lighter) image?

lighter

AEC does what?

terminates exposure when specific quantity of radiation reaches the IR

mA setting is the ?

amount of time needed to produce a given amount of xray exposure

Why do we use a higher mA?

to decrease exposure time when motion during a longer exposure would cause blurring

A higher mA = (larger/smaller) focal spot size

larger

Greater mAs = more xray ___________ = (darker/ligher) image

photons

darker

Changes in mA will affect the amount of _________ in amode during exposure

heat

kVp is the measure of potential _____________ across the x-ray tube and determines the speed of electrons

difference

x-ray photon energy is expressed by what?

photon wavelengths

Shorter wavelengths = ___________ energy

more

one kilovolt = ?

1000 v.

Changes in kVp cause ____________ of image to change

contrast

low kVp is for _________ body parts

high kVp is for __________ body parts

small

large

SID is the distance from the ? to the ?

x-ray tube (source) to IR

SID affects the x-ray beam ??? and beam ??? (size)

intensity

divergence

radiation intensity

# of photons/square inch striking IR

When were x-rays discovered?

Nov 8, 1895

Who discovered x-rays?

William Roentgen

What was the first device that produced x-rays?

Crookes Tube

Who developed interruptless transformers that provided the necessary electricity for x-ray production?

H.C. Snook

Who demonstrated radiographic use of fluorescent screens?

Michael Idvorsky Pupin

Who created the "hot cathode" x-ray tube which was a prototype for modern x-ray tubes?

William Coolidge

Who invented the first fluoroscope?

Thomas Edison

Who was Thomas Edison's assistant? (also was the first fatality from x-ray exposure)

Clarence Dally

Who invented the first x-ray film base in 1914?

George Eastman

What was the first anatomic radiograph of?

Roentgen's wife's hand

Photon

bundle of energy (visible light spectrum)

Differential absorption

some radiation stays (white)

some radiation goes thru (black/gray)

What are the 4 basic requirements for the production of x-rays?

vacuum

electron source

target for the electrons

high potential difference btwn electron source and target

What do each of these symbols mean?

C = λv

C = velocity = speed of light (constant)

λ = wavelength

v = frequency (Hz)

Are wavelength and frequency inversely or directly related?

inversely

Photon is the (smallest/largest) unit of electromagnetic energy

smallest

quanta

bundles of photons

x-rays can penetrate matter that is opaque to light. (T/F)

True

attenuation

change in x-ray beam after it passed through tissues and is differentially absorbed

remnant/exit radiation

x-ray beam after it has passed through the body

Do different types of tissue absorb different types of radiation?

Yes

X-rays are generated at the ______________ and sent to the _____________.

cathode

anode

What is the part of the x-ray tube containing tungsten?

filament of cathode and target of the anode

Imaginary line from center of focal spot, perpendicular to the long axis of the x-ray tube, is called the ?

central ray

The frequency of an electromagnetic sine wave is defined as?

The number of times per second that a crest passes a given point

Grids or buckys are generally used for body parts that measure greater than:

10-12 cm

The access point for the radiographer to determine the exposure factors and to initiate the exposure is called the?

control console

X-ray machine designed for direct viewing of the x-ray image is called a?

fluoroscope

A device that increases the voltage delivered from the power company to kilovoltage is called a?

transformer

The anode or positive end of the x-ray tube is the end that contains the:

target

Term defined as a measure of current flow rate in the x-ray tube circuit?

milliamperage

In order to increase penetration of x-ray beam, which factor should be increased?

kVp

Magnification is affected by?

OID and SID

Radiation exposure is directly proportional to

mAs

What is used to determine if the exposure factors were correct on a digital image?

exposure indicator number

Image detail is affected by ?

focal spot size and patient motion

What prevents scatter from reaching the IR?

buckys and grids

How do buckys prevent scatter from reaching the IR?

it reduces the affect of scatter radiation on image quality

What in fluoroscopy allows images to be viewed in light rather than in the dark?

image intensifier

Exposures made with the same mAs quantity will be _______________ in appearance, regardless of mA and time used

similar

SID affects 2 things

x-ray beam intensity and beam divergence (size)

The inverse square law states:

that intensity of the radiation is inversely proportional to the square of the distance

What is used to compensate for changes in SID according to an equation?

mAs

Intensifying screens do what to patient dose?

greatly reduces

What does PACS stand for?

picture archiving and communication system

4 factors of image quality

optical density

image contrast

image detail

distortion

Increased OD or radiographic density = _____________ image

Increased tissue density = _____________ image

darker

lighter

What causes a grainy image?

underexposure

The more kVp, more __________

gray

Lower kVp results in ___________ shades of gray

fewer

Radiographic contrast is influenced by

nature of subject

IR characteristics

amount of scatter radiation on IR

Increased SID = ____________ detail

higher

Increased OID = ___________ detail

lower

Increased motion = ___________ detail

lower

Small focal spot = __________ detail

higher

Shape distortions are caused by?

poor angling

International measurement system in radiology

SI

Effective dose

relative risk to humans of exposure to ionizing radiation

curie (ci)

becquerel (Bq)