Quiz 1 Flashcards
Radiology
X-Ray
Photons
Branch of medicine aiding in visulizing interior of body
Electromagnetic Radiation
- Particles
- Waves
Bundles of energy in x-ray beam. Rides the wave. Has no mass or electrical charge
Electromagnetic spectrum
Radiowaves - Microwaves - Infrared - Visible Light - Ultraviolet - X-rays - Gamma rays
X-ray properties
- Invisble
- cannot be felt
- type of electromagnetic radiation
- interacts with electrons
- penetrates matter
- ionizes atoms
Wavelength vs Frequency
Wavelength: Distance from point A to point B
Frequency: cycles per second
Longer the wavelength = Frequency decreases
Shorter the wavelength = Frequency increases
X-ray tube
Anode:
- Positive
- (Tungsten target)
- Temp. can exceed 1000 C. Use of copper base and oil to conduct heat away
Types:
- Stationary: Low xray production, can’t take a lot of heat.
- Rotating: Disk shape
Cathode:
- Negative
- (Filament)
Cathode + Anode = 99% Heat & 1% X ray
** Cathode side x ray beam is more powerful. Place thicker body parts on cathode side.**
Waves
Absorption
Longer the wavelength = Frequency decreases = has less energy = travels shorter/does not penetrate well
Shorter the wavelength = Frequency increases = has more energy = travels further/penetrates deeper
Absorption varies on:
- Atomic number
- Density of the object
- Enerrgy of the x ray
Postive vs Negative
Positive
Invisible images that is made visible via chemical or digital processing
Negative
Damaging and altering living tissue via:
- Excitiation - Photon strikes and excites electron in orbit causing it to move to a higher orbit causing biological changes
- Ionization - Photon displaces an electron in orbit by striking it and also causing biological changes.
Wilhelm Conrad Roentgen
Credited in discovering X rays
Used vaccum tubes to pass electrons from cathode to anode
Milliamperage (mA)
Kilovoltage (KVP)
Santes’ rule
mA
- Milliamperes
- measures the circuit that heats up the filament
- measures electric current
mA x 1/sec = mAs (milliamperage-seconds)
increase in mA allows shorter exposure time
KVP
- Kilovoltage peak
- mA is boosted by KVP to produce enough speed
- Measures pressure
Santes’ Rule: used to estimate KVP
(2 x thickness cm) + 40 = KVP
**increase kVP by 10 allows you to half the mAs or maintain mA with half the exposure time**
Focal Spot
Hits the target area
Smaller the focal point = Sharper the picture
** too small and it can’t stand the heat**
Failures
Electrical Components
Failures
Cathode Failure
- Filament evaporates if exposed to too much heat and time of use
- Does not get hot until you hit “pre exposure” button
- Turn off machine if not using.
- mA meter doesn’t move = filament is gone
Anode Bearings
- holding “pre-exposure” button down to long can overheat bearings
- Unusual noise is a problem
- no noise is sign of failed bearings
Target Damage
- Use low mA settings and high KVP to keep heat low.
Glass Envelope
- If air gets into
Electrical Components
High Voltage Circuits
Provides High electrical potential to move electrons from cathode to anode
- Autotransformer
- Step up transformers
Low Voltage Circuits
Provides electricity to heat filament
- Step down transformers
Collimator
Prevents scatter radiation
Restricts beams
Retification
Changes alternating to Direct current
so that constant electron flow is maintained
Control Panel
- On/Off button
- Voltmeter
- Kilovolt selector
- Milliampere selector
- Timer
- Exposure button
Radiation Damages & Exposure
Somatic
Damges to body tissue within person’s lifetime
Genetic
Damage to reporductive cells via genetic mutation
Hereditary damages
MPD (Maximum Permissible Doses)
ALARA (As Low As Reasonably Achievable)
Measured in Grays. 1 Gys = 100 rads (Radiation absorbed doses)
Absorbed Dose X Quality factor = Sieverts (Sv)
- Occupational - 0.05 Sv/yr
- Non Occ. - 0.005 Sv/yr
Use Lead Apron: 0.5mm Lead
Use 2.5 mm aluminum filter b/t window and collimator
Vet Tech role
Knowledge of
- x ray machine
- film
- cassettes
- film processor
- Safety requirments
- Proper techniques for production of diagnostic radiograph
- Evaluation of diagnostic quality
Rapidly dividing cells
Reporductive cells
Epithelial cells
Lymphoid cells
Hemopoietic
Fetal tissues
Density vs Contrast
Density
- Degree of blackness
- # of x rays reaching the film
- penetrating power of radiation
- development time/temp
- High mAs = High density
- High kVP = High density
High tissue thickness = less xrays reaching film = less density
Too Dark:
Decrease mAs: 30%-50%
Decrease kVp: 10%-15%
Too Light:
Increase mAs: 30%-50%
Increase kVp: 10%-15%
Contrast
- Difference in brightness in 2 neighboring areas
- High contrast = Short scale
- Low contrast = Long scale = more grays
Grids
Absorbs scatter radiation
Placed b/t patient and film
Lead strips: absorbs xrays
Spacer material: allows primary x rays to reach film
Types
- Focused: lead strips are angled
- Unfocused: Lead strips are parallel
- Pseudofocused: a compromise
- Crossed or Linear
**Use bucky if patient measurement is greater than 10cm**
SID
Source Image Distance
Distance b/t x ray tube focal spot and image receptor (Film)
Closer the distance = higher the intensity
Use constant 40 inches
Limbs Position
Use Cranial & Cauldal
(Front & Back)
Use Dorsal & Palmar/Planter
(Top & Bottom)
Nose to Ears
Rostral (cranial)
towards ears (Caudal)
Frontal Plane
Sagittal Plane
Transverse Plane
Median Plane
Separates Dorsal/Ventral
Separates Lt/Rt sides
Separates Cranial/Caudal
Separates Lt/Rt Halves
Technique Chart
Provides following information
- X ray cassette
- Placement of cassettes
- mA, mAs, kVp setting
Based on tissue thickness
Anatomical part
Created by site via trial and error
5 charts
- Extremity/Skull
- Abdomen
- Thorax
- Pelvis/Spine
- Avian/exotics
Under Exposure vs Over Exposure
Under Exposure (Too Light) w. anatomic outlines (adequate)
Solution: Increase mAs 30-50%
Under Exposure (Too Light) w/o anatomic outlines (Inadequate)
Solution: Increase kVp 10-15%
Over Exposure (Too Dark) w. white bones (Adequate)
Solution: Decrease mAs 30-50%
Over Exposure (Too Dark) w. grey bones, low contrast b/t bone and tissue (Overpenetration)
Solution: Decrease kVp 10-15%
Abdomen
Reasons for abdominal xrays
- Trauma
- Vomitting
- Distention
- Urinary Obstruction
- Mass
- General wellness
Long Scale Contrast (Low contrast - grays):
High kvp and low mAs
Abdomen view
V/D views (Stomach side up)
- Diaphragm to Femoral head
- Expiratory phase
- Beam center and measure on 13th rib
- Use sandbags under thoracic & v-trough
Lateral views
- Diaphragm to Femoral head
- Expiratory phase
- Beam center and measure on 13th rib
- Use foam pads b/t femurs and under sternum
Scapula
Scapula Lateral View
- Beam center on middle of scapula
- Measure thickest area of scapula
Scapula caudocranial View
- Beam center on middle of scapula
- Measure thickest area of scapulohumeral joint
- VD position
- Extend limb cranially
- Rotate sternum away from scapula
Humerus
- Center beam on center of bone
- Measure thickest area over shoulder joint
- Lateral position, dorsal recumbency (caudocranial view), abduct limb away from midline
- Include joints
Elbow
Craniocaudal view
- Beam center over joint
- Measure thickest area
- Position sternal recumbancy, head tilted away
- Use foam pad under elbow
Lateral view
- Center beam over joint
- Measure distal humerus
- Position with rope. Caudally push opposite limb back.
- Use foam under metacarpal
*
Radius & Ulna
Lateral view
- Center beam on middle of bones
- Meausre over elbow
Craniocaudal view
- Center beam on middle of bones
- Measure at distal humerus
- Sternal recumbency
Carpus
Lateral view
- Center beam on distal carpal bones
- Measure on center of joint
Dorsopalmar
- Center beam at middle of distal carpals
- Measure at center of joint
Metacarpus/Phalanges
Dorsopalmar view
Center beam on middle of metacarpal bones
Measure on middle of metacarpal bones
Lateral view
Cetner beam on center of digits
Measure on middle of phalanx
Image receptor Parts
- Film
- Intensifying screens (Converts xrays into visible light)
- Cassette (Lead backing)
Screens
Pros
Lower radiation
Lower mAs
Less exposure to patient
Lower chance of motion
Cons
Causes slight blurring of image
Parts
- Base (support)
- Reflective layer
- Phosphor crystal layer
- Protective coat
Screen Speed
Affected by:
- Phospher type
- crystal size
- phospher layer thickness
- reflective layer efficiency
- Dyes in phosphor layer
Large crystals
Faster screens
Less detail
Grainy
greater light emission
Small Crystals
Slower screens
more detail
less grainy
larger amount of radiation used
Thick Phosphor Layer
Increases xray absorption
Increases light emission
Decreases detail
Reflective layer efficiency
Reflects light from phosphor layer to film
Slow speed
- Optimal detail
- Long exposure time
Medium speed
- Good Resolution
- Short exposure
Fast speed
- Emits more light = Reduce exposure time = less detail
- penetrates thick tissue
Film Properties
- Silver bromide or Halide - aborbs xrays and visible light to form image
- 2 sided
- Do not expose any side to light (foggy means it was exposed to light)
- Will turn metallic silver once exposed
- Will be clear if unexposed
- Conversion makes film blacker
Screen film vs Non screen film
Screen Film
- Regular film: Blue sensitive
- Rare Earth: Green sensitive
- Sensitive to fluorescent light
Non screen film
- Best for bones and teeth
- More details
- responds directly to xrays
- More exposure
Film Storage
Vertically
inside darkroom
in cool/dry place
store away from radiation or chemcial fumes
Use before expiration date
Screen Speed
Efficiency in converting xrays to light
Technique Charts
Help keep consistancy
Improves efficiency
Chart factor
Screen speed & film
Age of screen
SID
beam filtration
temp/time of film processing
grid type
mAs vs kVp
Increase mAs for more density
Increase kVp for short exposure time (10-15%)
Too light w. outlines - increase mAs 30-50%
Too light w/o outlines - increase kVp 10-15%]
Too much penetration: decrease kvp
Overexposure: decrease mAs
Film processing
Dry side vs wet side
Dry side
place to place and remove film from cassettes
Storage bin for film
Wet side
For chemcial processing
- Developer - Converts silver halide crystal to black metallic silver
- water - to rinse, stop developing process, contamination
- fixer - clears unexposed crystals
- Wash bath - manual processing of stirring. (20-30 min.)
Steps to film processing
Step 1
Preparation
- chemicals should be at 68 degree
- Dont use same paddle
- Turn on safety lights
Step 2
Unload Cassette
- Dont use fingernails
- Shake film out
- Hold film by edges
- close cassette while labeling film
Step 3
Loading film to hanger
- attach to clips
- don’t touch the center of film
Step 4
Developing
- Put film in developing tank
- agitate a couple of times
- close lid
- set timer
Step 5
Rinsing
- Remove film
- Put in the rinse bath for 30 sec
Step 6
Fix it
- Put in fix tank
- agitate and set timer
- fix for 10 mins.
Step 7
Washing
- Remove film
- Wash for 20-30 mins.
Step 8
Drying
- hang film
- cut edges of film
- prevent dust on films
