Chapter 1-2 Study (BECKER)

Practice Questions as well as Key Learning Objectives. Key Terms will be in a separate cardset

What was the first device to produce x-ray beams?

Crooke’s Tube

What date did Roentgen accidentally discover x-rays?

November 8th, 1895

What did H.C. Snook develop?

Developed interrupter-less transformer which provided enough stable electricity for x-rays.

What did William Coolidge develop?

Designed the “Hot cathode” x-ray tube to work with Snook’s improved electrical supply.

• Coolidge Tube (introduced in 1910) became the prototype for modern x-ray tubes

What did Michael Idvorsky Pupin develop?

Demonstrated radiologic use of fluorescent screens

• Predecessor of intensifying screens

What did Thomas Edison develop?

Developed 1st fluoroscope (moving image) and discovered many fluorescent materials used in today's imaging

• Abandoned his research when his best friend and assistant, Clarence Dally, eventually succumbed to the effects of radiation from the experiments, becoming the first recorded x-ray death in the U.S. in 1904

What did George Eastman develop?

Invented first x-ray film base

What are the four essentials for the production of x-rays

• A vacuum (x-ray tube)

• Electron source (filament)

• Target for the electrons (anode)

• A high potential difference (voltage) between the electron source and the target (opposite charges attract)

What are some examples of electromagnetic wave radiation?

• Visible light

• Radiowaves

• Microwaves

• X-rays (ionizing)

  • Gamma rays (ionizing)

What are the main characteristics of x-rays?

• Travels in straight lines at the speed of light

• Affects photographic emulsions

• Affects biological tissues (ionizes atoms)

• Cannot be focused or refracted

• Cannot be detected by human senses

• X-rays cause certain crystals to fluoresce or give off light when

• exposed.

• X-rays can penetrate matter that is opaque to light

Attenuation

change in the x-ray beam after it passes through tissues and is differentially absorbed.

Sine Waves

Repeating sinusoidal waveforms created by changes in electromagnetic (EM) field

• Wavelength (λ): length between tops of waves

• Frequency (f): how many waves pass a point per second

• Velocity (v): the speed at which the wave crests move through a medium. It is measured in meters per second (m/s)

  • Amplitude: height of wave

Wavelength (λ)

length between tops of waves

Frequency (f)

how many waves pass a point per second

Velocity (v)

The speed at which the wave crests move through a medium. It is measured in meters per second (m/s)

Amplitude

Height of wave

What is the constant factor?

Velocity

What type of relationship does frequency and wavelength have?

An inverse relationship

Primary Radiation

X-ray beam that leaves the tube and is not attenuated, except by air

• Originates at the tube target and expands in a cone-shaped beam perpendicular to tube axis. Direction and location are predictable and controllable

• Energy controlled by kilovoltage setting

Scatter Radiation

Radiation scattered or created as a result of the attenuation of the primary x-ray beam by matter

• Travels in all directions from the scattering medium and is difficult to control

• Generally has less energy than primary beam

Remnant (exit) Radiation

What remains of the primary beam after it has been attenuated by matter

• Travel pattern is a continuation of the pattern of primary beam

• Because pattern of densities in the matter results in differential absorption, this pattern is inherent in remnant radiation. The pattern of intensity of remnant radiation creates the radiographic image

Parts of an x-ray tube?

• Cathode (filament):

  • Negative charge

  • Space charge

  • Dual-focus

  • Focusing cup

• Anode (target):

  • Positive charge

  • Spins to increase heat capacity

Cathode (filament)

• Negative charge

• Space charge

• Dual-focus

• Focusing cup

Anode (target)

• Positive charge

• Spins to increase heat capacity

X-ray tube housing

protective covering around the x-ray tube that supports components and shields from off-focus radiation

Collimator

Attached to tube housing and controls size of radiation field while providing centering lines to aid in IR alignment to patient

X-ray tube support

• Provides support and mobility for the tube with electronic locks keeping the tube in place.

  • Two Types:

    • Ceiling mount

    • Floor stand

Radiographic Table

Supports patient, omnidirectional with a moveable IR tray with grid under tabletop

Grids & Buckys

• Devices used to reduce the effect of scatter radiation on image quality

  • Prevents scatter from reaching IR

  • Generally used for body parts measuring greater than 10-12cm

Upright Image Receptor Unit

Hold the IR and/or a bucky(grid) in a vertical position

Transformer

provides high voltage necessary to produce xrays by increasing voltage provided by power/electric company. Connected to the tube via cables

Control Console

Input device for setting exposure factors, activating the exposure, and on/off powering of unit, located in a shielded control booth

When was the first anatomicc radiograph produced?

December 22, 1895, of his wife’s hand

When was the first documented medical use of x-rays in the United States

February 1896

• Exam of a boys fractured wrist

• Performed at Dartmouth College

How does the mathematical relationship between dose and time compare to the relationship between dose and distance?

Dose is linear with time but follows the inverse square law with distance

Which of the following is NOT an accurate statement regarding the characteristics of x-rays?

• They can penetrate matter that is impenetrable to light

• Can be refracted by a lens

• Cause certain crystals to fluoresce

• Cannot be detected by the human senses

Can be refracted by a lens

The purpose of rotating the x-ray tube target is to:

• Focus the electron stream on a small target area

• Create a space charge

• Increase heat capacity of the anode

• Remove long-wavelength photons from the x-ray beam

Increase heat capacity of the anode

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

• Central ray

• X-ray beam

• Electron stream

• Radiation field

Central ray

The frequency of an electromagnetic sine wave is defined as:

• Distance from one crest to the next

• Distance from trough to crest

• Velocity at which the wave travels through space

• Number of times per second that a crest passes a given point

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?

10-12cm

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

The control panel

An x-ray machine designed for direct viewing of the xray image is called a:

• Fluoroscope

• Transformer

• Control console

• Image Receptor

Fluoroscope

A device that increases the voltage delivered from the power company

Transformer

The anode or + end of the tube is the end that contains the:

• Target (anode disc)

• Focusing cup

• Space Charge

• Filament

Target (anode disc)

Which term is defined as a measure of current flow rate in the x-ray tube circuit:

• mAs (mA + time)

• Exposure time 

• Milliamperage (current)

• kVp (potential difference in charge between two ends of the circuit) (think how fast the electrons are pulled from cathode to anode)

Milliamperage (current)

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

• Kilovoltage (quality - strength) 

• Milliamperage

• Exposure Time

• mAs (quantity - )

Kilovoltage (quality - strength) 

Magnification is affected by:

• SID only

• OID only

• Both SID and OID

• Neither OID or SID

Both SID and OID

Radiation exposure is directly proportional to:

• OID

• SID

• kVp (primary control of the quality and energy of the beam. If you increase kVp, it doubles exposure making it hard to control the exposure due to its nature to make quantity jump significantly. Tiny kVp changes make massive dose spike)

• mAs (exposing the patient to an amount of radiation AKA quantity ;)

mAs (exposing the patient to an amount of radiation AKA quantity ;)

An image that is black in the darkest areas and white in the lightest areas is said to have

• High contrast

• Poor detail

• Low contrast

• Sharp detail

High contrast

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

• Exposure indicator number

• Visual clues

• Technique chart

• Optical density number

Exposure indicator number

Image detail is affected by:

• Focal spot size and patient motion

• Focal spot size and mAs

• kVp and SID

• mAs and SID

Focal spot size and patient motion

What kind of relationship does kVp and contrast have?

Inverse

• Higher kVp: lower contrast (more shades of gray)

• Lower kVp: higher contrast (fewer shades of gray)

Who invented the hot cathode x-ray tube?

William Coolidge

Where are the majority of radiography programs based in

Colleges

A cassette containing a photostimulable phosphor plate is one form of

Image receptor

Which of the following is NOT a basic requirement for the production of x-rays:

• vacuum

• source of electrons

• photostimulable phosphor

• target

A photostimulable phosphor

When fast moving electrons collide with the target of an xray tube, the kinetic energy of their motion is converted into xrays and?

heat

What EM energy has the shortest wavelength?

Gamma Rays

Can xrays be refracted by a lens?

No

What characteristic is most often used to describe the energy of an xray beam?

Wavelenth

What is an xray beam attenuated by matter called?

Scatter radiation

What is the name of the device used to indicate the location of the radiation field and control its size?

Collimator

An xray machine that permits viewing of the xray image in motion in real time is a?

Fluoroscope

What imaging system provides an instantaneous digital image on a monitor?

Digital radiography

What computer hardware is used for managing digital images?

PACS

The inverse-square law states that radiation intensity is inversely proportional to the square of the ___

SID

A variation in the size or shape of the image in comparison to the object it represents is ________?

Distortion

What is the primary factor for controlling contrast?

kVp

(also by subject and amount of scatter)

What is milliamperage and how does it affect radiographic exposure?

mA is an indication of the number of x-ray photons produced per second. Thus the mA setting will determine how much time is needed to produce a given amount of x-ray exposure 

Explain the significance of exposure time with respect to optical density.

Exposure Time measures how long the exposure continues, and with mA, determines the total quantity of radiation produced. In relation to OD, longer exposure time lets in more light which creates a higher density (darker image) and vice versa. Once again, it’s an inverse relationship

Explain the significance of mAs with respect to image quality.

mAs is the product of mA x time. It’s directly proportional to radiation exposure. Greater mAs = more xray photons = darker image

Describe the effects of an increase in kVp with respect to both the x-ray beam and the radiographic image.

kVp determines the speed of the electrons and provides them the kinetic energy they have when colliding with the target which determines x-ray photon energy.

• Shorter wavelengths = more energy and greater penetration of tissues

• Higher kVp = more penetrating xray beam = darker image

State the content and purpose of an x-ray technique Chart.

A technique chart provides recommended exposure factors for various exams and patient sizes

Define OID and state its significance regarding radiographic quality

Object-image distance is the distance between the object and the IR. Increasing OID decreases detail

Explain the effect of an increase in source-image distance on both optical density and image detail.

An increase in SID increases image detail while decreasing the optical density. This happens because of the Inverse Square Law meaning that the intensity of the x-ray beam drops rapidly as distance increases. Fewer photons strike the image receptor, resulting in a lighter image (decreased optical density)

List three types of image receptor systems and describe each.

CR and DR automatically adjust visual quality of image

• Computed Radiography (CR)

  • Uses imaging plate containing photostimulable phosphor

  • Exposed plate inserted into reader

• Digital Radiography (DR)

  • No cassettes, nor separate reader

  • Instantaneous 

• Film:

  • Composed of a polyester base coated on both sides with emulsion

  • Stored in area protected from radiation and chemical processing fumes

  • Needs to be developed

List the two types of image distortion and state the cause of each.

• Shape

  • Result of unequal magnification of various parts of the subject

  • Part parallel with the IR = less distortion

  • Central ray perpendicular to the part = less distortion

• Size

  • Always magnification affected by SID and OID

  • Shorter SID causes defining rays to diverge at a greater angle, increasing mag. Same thing happens when OID increases

Shape Distortion

• Result of unequal magnification of various parts of the subject

• Part parallel with the IR = less distortion

• Central ray perpendicular to the part = less distortion

Size Distortion

• Always magnification affected by SID and OID

• Shorter SID causes defining rays to diverge at a greater angle, increasing mag. Same thing happens when OID increases

What is the prime factor of exposure?

The SID

Factors that influence image contrast

• kVp

  • Higher kvp = lower contrast (more shades of gray)

  • Lower kVp = higher contrast (fewer shades of gray)

• Computer processing

List possible causes of poor image detail

• SID too far, lower detail

• OID too high, lower detail

• Too much motion

• Too large of a focal spot

• Size of pixels in digital systems

List three digital pitfalls and explain how they should be avoided. 

• Brightness and contrast should not be used to pass an image when it’s not of diagnostic quality

• Annotations should never replace the use of physical lead markers, even if markers weren’t placed. It could be illegal

• Shuttering, cropping, and masking should never be used to substitute poor collimation rather to improve quality of displayed image