Ch. 1-3 Vet 280
Introduction to Radiology & Safety: Chapters 1-3
Objectives - Chapter 1
Discuss the basics of Radiologic science.
Describe how x-rays are produced.
Describe the elements of the electromagnetic spectrum.
Explain the relationship between energy, frequency, and wavelength.
Explain 12 properties of x-rays.
Describe the function and location of the components of an x-ray machine.
Describe the use and components of the image logbook.
Electromagnetic Spectrum and Basic Components of Energy
Forms of Energy:
Electrical, chemical, mechanical, thermal, nuclear, and electromagnetic.
For radiographs and x-ray production, electrical energy is most important.
Components of the Electromagnetic Spectrum:
Energy (eV), Frequency (Hz), and Wavelength.
Wavelength: X-rays have between 0.03-3 nanometer wavelengths. No visible waves exist.
Frequency and Wavelength Relationship
Frequency: Number of waveforms striking an object during a given time period, measured in Hertz (Hz).
Wavelength: Comprises frequency and amplitude.
Height of the wavelength = amplitude.
Distance between crests = frequency.
Characteristics of Wavelengths:
Long wavelengths: low frequency, weak, associated with microwaves and radio frequency.
Short wavelengths: high frequency, powerful, and associated with gamma rays.
Short wavelengths require less time to produce and have greater penetration power.
X-ray Properties
Definition: X-rays are non-luminous electromagnetic radiation.
Safety Precautions: It’s crucial to ensure the safety of patients and staff during imaging procedures (gowns, gloves, thyroid collars, dosimetry badges).
Discovery: Professor Wilhelm Rontgen credited with discovery through scientific method.
12 Properties of X-rays
Highly penetrating, invisible rays, a form of electromagnetic radiation.
Electrically neutral - unaffected by electric or magnetic fields.
Produced across a variety of energies and wavelengths (polyenergetic & heterogeneous).
Release small amounts of heat when passing through matter.
Travel in straight lines.
Speed of light: 3 imes 10^8 meters/second in a vacuum.
Capable of ionizing matter.
Cause fluorescence in certain crystals.
Cannot be focused by a lens.
Affect photographic film.
Cause chemical and biological changes in matter via ionization and excitation.
Produce secondary and scatter radiation.
X-ray Tube Anatomy
Mechanism: X-rays result from high-impact of heated negatively charged electrons on a target (anode).
Components: Includes x-ray tube head, control center, tabletop, bucky tray, transformer, generator.
X-ray Tube Head: Contains anode, cathode, glass enclosure, and window.
Anode:
Types: stationary and rotating.
Most common: rotating anodes, which rotate at 3200 - 3600 revolutions per minute, providing better heat resistance and electrical conduction.
Cathode:
Consists of filaments made of thoriated tungsten. High melting point (6170°F).
Electrons released upon filament excitation, directed towards the anode.
X-ray Tube Components
Glass Enclosure: Houses anode and cathode, provides vacuum for operation.
Beryllium Window: Allows x-rays to pass with minimal absorption.
Collimating Device: Restricts the x-ray beam size.
Bucky Tray: Holds x-ray cassette beneath tabletop during exposure.
Controls: ON/OFF, kVp selector, mAs selector, time selector, x-ray prep, exposure button.
Transformer Functions:
Raises voltage from 220 volts to approximately 125,000 volts.
Step-down transformer adjusts voltage to technician's settings.
Record Keeping in Radiology
Radiographs are part of patient records and must be filed for easy retrieval; views of one study placed in a single folder with patient and date information.
Radiology Log: For tracking studies includes information on patient name, body part, position, settings used, technician’s initials.
Original radiographs owned by clinic; digital images formatted as DICOM.
Key Points from Chapter 1
X-rays between gamma and ultraviolet ranges (0.03-3 nanometers).
X-ray machine principal components: tube head, control center, tabletop, bucky tray, transformer, generator.
Anode types: rotating vs stationary; stationary units have more heat concerns.
Radiology logs essential for tracking studies; digital systems integrate with electronic medical records.
Radiographic Equipment: Chapter 2
Objectives - Chapter 2
Describe the purpose of grids and their effect on radiograph quality.
List parts and function of intensifying screens.
Compare types of intensifying screens with pros and cons.
Explain effects of milliamperage and kilovoltage on contrast and density.
Describe differences between standard radiography and fluoroscopy.
Introduction to Radiographic Units
Types of x-ray Units: Portable (non-rotating anode) vs stationary (rotating anode).
Units for clinics based on volume: Low-volume may use larger animal extremities occasionally; medium-volume needs varied capabilities, while high-volume likely needs stationary units.
Milliamperage and Kilovoltage Effects
Milliamperage (mA): Relates to exposure and image sharpness.
Kilovoltage (kVp): Higher kVp for soft tissues, lower for extremities to discriminate structures with fewer shades of gray.
Time: Duration of anode's positive charge; affects electron production.
mAs (milliampere-seconds) is the product of mA and time.
Cassettes: Protect film from light; constructed to withstand weight. Criteria include sturdiness, weather resistance, no bending, secure latches, and radiolucent cover with lead foil backing.
Intensifying Screens
Located in cassettes, made of crystals that fluoresce upon exposure to x-rays, increasing image quality with lower exposure radiation needs.
Lifespan: Most fail after 10-15 years of regular use with care.
Screen Speed and Types
Screens classified by speed affecting exposure needed: ranges include fast, regular, medium, par, and detailed in veterinary settings.
Rare earth phosphors are more efficient, reducing exposure time, motion artifacts, and improving contrast while increasing tube life and reducing patient exposure.
Grids Function
Grids reduce scatter radiation and enhance contrast in radiographs, requiring increased time due to absorption.
Used when thickness exceeds 10 cm, consists of alternating strips.
Grid ratios indicate quality with higher ratios needing increased mAs; ideal veterinary ratio is 8:1.
Types of Grids
Parallel Grids: Lead strips perpendicular to surface.
Disadvantages: Divergence leads to grid cutoff.
Focused Grids: Lead strips angled to match x-ray beam divergence, require specific focal distances (34-44 in, or 86-112 cm).
Other Options: Linear grids, crossed grids, movable Potter-Bucky grids, air gap techniques.
Additional Measurement Tools
Calipers: Measure radiography areas ensuring accurate diagnostics.
Film Identification: Must label with veterinary practice, date, patient and owner's names. Can use lead letters, graphite tape, or imprinters.
Key Points from Chapter 2
Milliamperage, kilovoltage, and time settings maximize x-ray quality.
Cassettes protect film and contain screens that fluoresce.
Grids decrease scatter radiation while enhancing contrast; parallel vs focused grids vary in effectiveness.
Use calipers for precise measurements in radiography planning and ensure proper labeling for legal records.
Radiation Safety: Chapter 3
Objectives - Chapter 3
Identify the organs most affected by radiation.
Describe radiation effects on the human body.
List methods to minimize radiation exposure.
Identify devices for monitoring exposure.
Discuss equipment used for staff protection during radiation exposure.
Importance of Radiation Safety
Radiation exposure effects may not be visible but cumulative over time; proper protective equipment is mandatory in veterinary clinics to ensure safety.
Warning Signs: Indicate radiation areas (e.g., "CAUTION: X-RAYS. DO NOT ENTER WHEN DOOR IS CLOSED").
Radiation Hazards
Four potential effects of radiation on living cells:
Pass through cells with no effect.
Damage to cells, repairable at some degree.
Permanent damage, not repairable.
Cell death.
Genetic damage possible for future generations; sensitive areas include skin, lymphatics, thyroid, hematopoietic tissue, breast, eyes, gonads, bone growth centers.
Radiation Exposure Tracking
Measurement Units:
Roentgen: Measures radiation exposure.
RAD: Absorbed dose of ionizing radiation.
REM/Sievert: Expresses equivalent dose from exposure.
Maximum permissible dose established by OSHA: 5 REMs per year, with accumulated dose formula N-18 with N as age in year.
Additional Tracking Systems
ALARA Principle: Stands for “as low as reasonably achievable.”
A radiation safety officer maintains equipment and monitors dosimetry readings.
Signs indicate potential ionizing radiation in areas; awareness increases safety practices.
Radiation Monitoring Devices
Dosimeters track radiation exposure; must not be exposed to heat or pressure.
Staff handling radiographs receives personalized dosimeter badges.
Badges ideally worn on collar outside the protective lead apron, or on a wristband.
Badge evaluation frequency varies with clinic workload, reported in millirems (A1mrem).
Radiation Exposure Reduction Strategies
Use time, distance, and shielding to minimize exposure:
Time: Conduct procedures efficiently to prevent repeat exposure.
Distance: Maintain as much distance as possible from primary beam.
Shielding: Wear lead aprons, gloves, thyroid collars, and implement patient sedation to minimize movement.
Personal Protective Equipment (PPE)
Essential PPE includes thyroid collars, gloves, aprons, and eye protection, with a minimum lead equivalency of 0.5mm.
Proper care extends the life of the protective gear:
Gowns/aprons should hang to prevent creasing; gloves should be stored open.
Routine checks of gloves and protective equipment ensure safety integrity.
Key Points from Chapter 3
Clinics must supply appropriate personal protective equipment to all staff.
Long-term radiation effects can be somatic or genetic.
Radiation exposure is measured in sieverts (1 Sv = 100 REM).
ALARA principle promotes minimal exposure practices.
Dosimeter badges are crucial for staff safety; everyone involved must have one.
Personal protective equipment minimizes the risk of radiation exposure in veterinary practice.