Radiography Notes

Radiograph Production

Job Skills for X-Ray Technologist

  • Photographer
  • Knowledge of Physics
  • Mathematics
  • Anatomy
  • Physiology
  • Computer Skills
  • People Skills
  • Problem Solver
  • Doctor's Assistant: The doctor is only as good as the images you produce.

Career Opportunities in Radiography

  • Computed Tomography (CT)
  • Magnetic Resonance Imaging (MRI)
  • Nuclear Medicine
  • Ultrasound
  • Radiation Therapy
  • Positron Emission Tomography
  • Cath Lab Tech
  • Specials Tech
  • Registered Radiology Assistant
  • Quality Management
  • Bone Densitometry (DEXA)
  • Sales, Teaching

Tips for Success

  • Fast-paced environment.
  • Stay ahead:
    • Read before class.
    • Expect frequent tests.
    • Form study groups.
    • Retain 90% of the information.
  • Make new friends for support.

Study Habits

  • READ before class!!!
  • Outline chapters.
  • Use note cards.
  • Form study groups.
  • Answer all homework questions.
  • Know all vocabulary.
  • Understand labs.
  • Take responsibility for learning; the instructor is an aid.

Seeking Help

  • Find outside sources (books, 2nd-year students).
  • Join study groups.
  • Schedule time with the instructor.

Syllabus

  • Know how to use it.
  • Assignments include:
    • Reading
    • Assignments
    • Discussions
    • Non-graded homework
    • Questions
    • Vocabulary
  • Required materials: books/workbooks, calculator.
  • Calculator skills:
    • Addition, subtraction, multiplication, division with fractions and decimals.
    • Converting between percentages, decimals, and fractions.
  • Clinicals are a year-long job interview!

Grades

  • Tests/Quizzes:
    • Lectures
    • Lab
    • Reading
  • Cheating: Talking during tests results in a zero.
  • Discussions/Worksheets
  • Labs:
    • Lab Practical
    • Absences: 2 tardies = 1 absence; instructor meeting required after 2 absences.

History of X-Ray

  • Copyright © 2013, 2009, 2004, 1999, 1993, 1989, 1985, 1981 by Mosby, Inc., an affiliate of Elsevier Inc.
  • November 8, 1895: X-ray discovered by German scientist Wilhelm Conrad Roentgen.
  • Roentgen discovered X-rays by accident.
  • Identified all the properties of x-rays.
  • More interested in the characteristics as a form of energy than practical use.
  • 1901: Roentgen received the first Nobel Prize in Physics.
  • X-rays were initially called Roentgen Rays.

Discovery Details

  • Crookes tube: first device to produce x-rays.
  • Research experiments in the 1870s and 1880s did not discover x-rays.

Early Radiographers

  • Roentgen created the first anatomic radiograph: an image of his wife's hand.
  • February 1896: first documented medical use of x-ray in the U.S. at Dartmouth College.
    • Exam of a boy's fractured wrist.
  • The first radiographers were physicists familiar with the Crookes tube.
  • Physicians followed and trained their assistants.
    • They also developed the first x-ray procedures to demonstrate anatomic structures.
  • Assistants skilled in radiography were called "x-ray technicians".

Radiography Education

  • On-the-job training evolved into hospital-based education.
  • 1950s: radiation therapy education separated from radiography.
  • Community colleges and four-year universities now offer education.

Overview of Radiographic Procedure

  • The radiographer:
    • Positions the patient's anatomy over the image receptor (IR).
    • Aligns the x-ray tube (beam or central ray) to the IR.
    • Sets exposure factors.
    • Activates the exposure switch.
  • There are many types of IRs.

Image Formation

  • X-ray photons pass through the patient, interacting with tissues.
  • Photons exiting the patient strike the IR to create a latent (invisible) image.
  • The manifest (visible) image is obtained depending on the IR type and viewed on a monitor.

X-Ray Production Requirements

  • Four basic requirements for producing x-rays:
    • A vacuum (x-ray tube)
    • Electron source (filament)
    • A target for the electrons (anode)
    • A high potential difference (voltage) between the electron source (cathode) and the target (anode).
      • Opposite charges attract.

Electromagnetic Energy

  • Sine waves: repeating sinusoidal waveforms created by changes in the electromagnetic (EM) field.
  • Key properties:
    • Amplitude
    • Wavelength
    • Frequency
  • Photon: smallest unit of EM energy.
  • Quanta: bundles of photons.

Electromagnetic Spectrum

  • X-rays are a man-made form of electromagnetic energy with both electrical and magnetic properties.
  • Energies are classified by wavelength.

Waveforms

  • X-rays travel through matter in a wave-like fashion (sine wave).
  • Wavelength: distance from crest to crest.
  • As energy of x-ray photons increases, the crests of the waves get closer together.
  • Frequency: number of crests that pass a point per unit time.

X-ray Energy and Penetration

  • As energy of x-ray photons increases the crests of the waves get closer together
  • What happens to frequency?

Properties of X-Rays

  • X-ray photons cannot be focused by a lens.
  • X-ray photons travel in straight lines and diverge from the point of origin.
  • X-ray photons cannot be deflected by mirrors.
  • X-ray photons cause changes in sensitive film emulsion (like light).
  • X-ray photons cause certain substances to fluoresce (emit visible light after absorbing radiation).
    • This is also called luminescence (giving off light).
  • X-radiation interacting with matter produces secondary radiation and scatter.
  • Can cause biological changes/harm: ionizes tissue.
  • X-rays cannot be detected by human senses.

The Primary X-Ray Beam

  • Focal spot
  • Primary x-ray beam
  • Radiation field
  • Central ray
  • Collimator

Scatter Radiation

  • Definition: When an x-ray photon hits something and changes direction.
  • Created when a portion of an x-ray photon’s energy is absorbed.
  • Primary source of occupational exposure.

Radiographic Equipment

  • The X-Ray Tube
    • Cathode = filament
      • Dual-focus
      • Focusing cup
    • Anode = target
  • The X-Ray Tube Housing
    • Protective covering around the x-ray tube
    • Functions
      • Protects and supports components
      • Shields from off-focus radiation
  • X-Ray Tube Support
    • Provides support and mobility for the tube
    • Two types
      • Ceiling-mount (photo)
      • Floor-stand
    • Electronic locks keep tube in place
  • Collimator
    • Attached to tube housing
    • Controls size of radiation field
    • Light provides centering lines to aid in alignment of IR to patient
  • Radiographic Table
    • Specialized unit that supports the patient
    • Most move in several directions
    • Moveable IR tray with a grid located under top
  • Grids and Bucky's
    • Devices used to reduce the effect of scatter radiation on image quality
      • Decreases scatter from reaching the IR
  • Bucky=IR holder with a grid
  • Upright Image Receptor Units
    • A device that holds the IR and/or a Bucky (grid) in a vertical position
  • Transformer
    • Provides the high voltage necessary to produce x-rays
    • Connected to the x-ray tube via cables
  • Control Console
    • Located in shielded control booth
    • Input device for setting exposure factors, activating the exposure, and on/off powering of the unit

Obtaining a Radiograph

  • X-rays exit the x-ray tube and enter the patient.
  • Tissues have varying degrees of ease or difficulty for x-rays to move through them.
  • Some tissues absorb more x-ray than others (attenuation).
  • X-rays exiting the patient interact with an Image Receptor (IR) to form the radiograph.

Radiopaque vs. Radiolucent

  • Opaque: does not allow light to pass.
  • Radiopaque: does not allow x-rays to pass.
  • Radiolucent: allows x-rays to pass.

Object Density vs. Radiographic Density

  • Object Density: How close or compact the molecules are in matter/tissue.
    • More compact – the object density increases
    • The heavier the object is
    • Harder to penetrate
  • Radiographic Density: How black the image/radiograph is.
    • More radiographic density - the blacker the image

Shades of Gray

  • Due to varying object densities, radiographs range from white to shades of gray to black.
  • Radiographic density is necessary to make the image visible.
  • Tissues with greater object density, such as bone, require more x-ray exposure.

Basic X-ray/Tissue Densities

  • Gas-air (lung)
  • Fat
  • Water (muscle)
  • Bone
  • Teeth (enamel)
  • Metal
  • Dark
  • Intermediate-dark
  • Intermediate-light
  • Light white
  • White
  • Solid white

Exposure Terminology:

  • Exposure: X-rays come out of the tube and interacts with the patient and the image receptor.
  • Non-exposure: when X-ray does not come out of the x-ray tube
  • Overexposure: too much blackening on the image receptor.
  • Under-exposed: not enough blackening on the image receptor to show contrast.

Primary Radiation

  • Primary Radiation- x-ray that is made in the tube

Attenuation

  • Weakening of the x-ray beam by number of x-rays
    • Does not change strength of x-ray
  • As x-rays travel through body, they are attenuated (absorbed and scattered) by tissue

3 Ways to Attenuate the X-Ray Beam

  • Inverse Square Law
    • As beam diverges, you always get less X-ray
  • Absorption
    • Some X-rays are absorbed by the body and don’t ever exit
  • Scatter
    • X-ray that hits something and changes direction

Scatter

  • When x-ray strikes an object and changes direction.
  • Scatter may or may not hit the image receptor(IR)
  • Scatter increases radiographic density/IR darker
  • Increases technologist dose

What Comes Out of the Patient

  • Exit Radiation
  • Remnant Radiation
  • Transmitted
  • Scatter
  • This is what remains after the primary beam is attenuated

Contrast

  • A substance given to enhance or visualize a structure.
  • Radiopaque Contrast (Positive Contrast): Iodine, Barium examples UGI, IVP
  • Radiolucent Contrast (Negative Contrast): Air, Gas, CO2 examples BE with air, UGI

ALARA: As Low As Reasonably Achievable

  • Reduce Patient Exposure: Cardinal Rule: Time, Distance, Shielding
    • Optimum Techniques
    • No REPEATS!!!!
    • Close Collimation
    • Filtration
  • Reduce your exposure
    • Time, Distance, and Shielding

How Can I Reduce Radiation Exposure to the Patient?

  • Good Technique- NO Repeats!
  • Collimation
  • Gonadal Shielding
  • Patient Positioned Properly

How Can I Reduce Radiation Exposure to Myself?

  • Time
    • Shortest time possible
  • Distance
    • Longest distance possible from x-ray source(6Ft +)
  • Shielding
    • Stand behind a shield or wear lead
  • Good Technique
  • Collimation-Less x-rays

Terms

  1. Radiographer
  2. Radiologist
  3. Diagnostic
  4. Therapeutic
  5. Photon