Diagnostic imaging Flashcards
four properties of x-rays which make the dangers
easily underestimated?
- They are invisible
- They are painless
- The effects can take years
- Effects are cumulative
most susceptible cells to ionising radiation?
gonads and young animals
Effects of Radiation?
- Generalised inflammation
- Blood disorders
- Death of tissues/necrosis
- Death/mutation of foetus
- Damage to gonads
Somatic Effects of radiation
Reddening of skin
Cracking of skin
Blood disorders
Cataracts
Digestive issues
Carcinogenic Effects
Tumours
Genetic Effects of radiation?
mutated chromosomes /inherited abnormalities
Ionising Radiation Regulations (IRR) 2017
Principles of radiation protection work
Radiography should only be
performed when…?
- Justifiable clinical reason
- Exposure is kept to a minimum
- Dose limits are not exceeded
What does the ‘Guidance Notes for the Safe
Use of Ionising Radiations in
Veterinary Practice’ cover?
Legislation specific
to veterinary covering premises, equipment, personnel
and procedures
3 main sources of radiation
- Leakage from tube head – faulty
equipment - Exposure to the primary beam
- Exposure to scattered radiation
How to check for Leakage From The Tube Head?
Tape a non screen film to the tube head, leave for a few
exposures and then process it; any cracks in the tube
head will cause black lines to appear on the film
How Can We Reduce Scattered Radiation? (6)
- Collimate
- Reduce KV
- Use lead backed cassettes
- Use lead topped tables
- Compress large areas of soft tissue
- Use grids.
Responsibility of Suppliers of X-ray machines safety?
- Legal: To ensure safe and correct functioning.
Responsibility of Veterinary practice of X-ray safety?
Legal responsibility: Annual service
* Individual staff
RADIATION PROTECTION SUPERVISOR Role?
appointed within the practice
* Responsible for radiography is carried out safely (local rules are obeyed)
* RPS does not need to be present
for every examination
RADIATION PROTECTION ADVISOR role
RPA is appointed outside of practice
* VS with Dip in Vet Radiography
and knowledge of radiation physics
* Medical physicist
* RPA gives advice on radiation protection, controlled areas and Local Rules.
what are local rules?
Set of instructions written by
Radiation Protection Advisor
(RPA)
The Controlled Area must have
- Warning sign
- Visible lights
- Warning buzzer
ALARP?
As Low As Reasonably Practicable
(The principle of keeping each individual’s dose)
Dose meter testing
Every 4 – 12 weeks
(Reports kept for at least 2 years)
Dosimeter Film Badge
Blue: contains small
pieces of x-ray film
Thermo-Luminescent Dosimeter Badge (TLDB)
Orange/Purple: contain
Lithium Fluoride crystals that
are radiation sensitive
Records of x-ray doses
- Date
- Patient details
- Region radiographed
- Exposure factors
- Staff
- Owner/case number
- Animals breed and weight
- Projection/view
- Image quality
Are protons positive or negative
Positive
electromagnetic spectrum
the shorter the wavelength, the higher the
frequency and the greater the energy
Are electrons positive or negative
negative
Structure of Atom
Nucleus: protons and neutrons
Orbiting: electrons
What is the atomic number
The number of protons or electrons is unique to the atoms of
each element.
Elements with a low atomic number are…?
radiolucent
Elements with a high atomic number are…?
radiopaque
polychromatic?
photons of varying energy
Milliamperage
quantity
Kilovoltage
quality
line focus principle
Anode slanted to:
1. Increase surface area
2. focus the beam for clearer image
Benefit of Small focal spot?
fine detail e.g. limbs
Benefit of Broad/Course focal spot
Areas that require a higher
exposure e.g. abdomen or chest
Rotating Anodes
Higher exposures
Dispersing heat more effectively
The target is always rotating
Molybdenum rod
Penumbra Effect
Partial shadow’
Line Voltage Compensator
Control voltage
Exposure Button
2 stage press
Half press- heats up filament
Full press- Applies kV
Light Beam Diaphragm
collimates the beam
Effect of kV
Higher the kV, the greater the
energy of the x-ray photons
produced
* Greater their penetrating
power
Effect of mA and Time
Higher the mA, the more x-ray
photons will be produced
* Increasing the beams intensity
The 10 kv rule
Increase kV by 10
Half the mAs
Decrease kV by 10
Doubling the mAs
Degree of X-ray absorption
depends on
- Tissue thickness
- Molecular density (atomic number)
Focal–Film Distance (FFD)
Distance between focal point and film
(Its intensity (mAs) falls as it moves
away from the tube, as it spreads
over a larger area. The opposite
happens if closer to the tube)
Increasing kV increases the
penetration and therefore
produces
darker film
Too low a kV will not penetrate
tissues, therefore appearing
white on film with black background
(high contrast film)
- Increasing the mAs produces more x-rays to blacken the film, but with
no more penetrating power
Overall picture will appear darker
- Metal
- Fat
- Soft tissue or fluid
- Bone
- Gas
-White
-nearly white
-mid grey
-grey
-Black
X-ray wavelengths are measured in units known as?
ANGSTROM
x-ray energy is called?
photons or quanta
The anode
Positively charged
The catode
Negatively Charged
Which electrode produces electrons
The cathode
THERMIONIC EMISSION?
A cloud of electrons
Filament facts
Is heated by the electric current.
made of tungsten
Can be coiled
Function of STEP-DOWN or filament transformer
Reduces mains current
STEP-UP or high tension transformer
creates a HIGH POTENTIAL DIFFERENCE
focusing cup is made of?
molybdenum
Purpose of glass envelope/vacuum
Stops electrons colliding with are and slowing speed
Purpose of aluminium filter?
Removes low energy photons
Film Focal Distance (FFD)
Distance between focal spot and X-ray
the two types of Digital Radiography
- Computed radiography (CR)
(uses imaging plate) - Direct digital radiography (DDR)
(goes straight to computer)
DICOM
Digital imaging and
communications in medicine
Benefits of DICOM
- Preventing tampering with
original image - Ensures consistency of file
type between all radiographic
systems
When to use a GRID
On the thicker parts of the patient such as CHEST (over 15cm) and
ABDOMEN (over 10cm)
What influences scatter
- Duration of x-ray production (s)
- Thickness of tissue
- Focus of the x-ray beam
How to reduce scatter
- Reduce the s and increase the mA (if possible)
- Accurately select exposure factors
- Collimate the primary beam
- Use a grid
Grid factor
2.5 - 3
Types of grids
Stationary Grids
* Parallel Grid
* Focussed Grid
* Pseudo-focussed Grid
* Crossed
Moving Grid
* Potter-Bucky diaphragm
features of Parallel grid?
features of Focused grid
- Must be central
- Can prevent grid cut off
- Lead strips angled
- Correct FFD must be used
- right way up
Features of Pseudo-focused grid
- Combination of focused and parallel grid
- Parallel strips get shorter towards the periphery
- Must be central
Crossed grid features
Only allow high energy x-rays through
equine
Moving Grids
- Built in to table
- Moves slightly during exposure
- Eliminates grid lines
- Grid factor = 4
Care Of Grids
- Careful handling
- Do not drop
- Clean regularly
- Correct storage
Information Needed On A BVA Hip And Elbow
Score Radiograph
- Date
- Kennel club number
- Left/Right marker
- Microchip number
Safe Lighting used for manual radiography
Low intensity lights (brown or red filters)
* Bulb <15W
1.2/4ft from the workbench?
Positive Contrast Media
Contain elements of high atomic number
radio-opaque/ Appear white
* Provide positive contrast in comparison to soft tissues
Negative Contrast Media
Gases (room air, N2O, O2, CO2)
* Low density
* radiolucent
* Appear black
* Used in bladder and gut
Double-Contrast Studies
positive and negative contrast media in hollow organs
to aid mucosal detail
Colon, bladder, stomach
Types of Positive Contrast Media
- Barium sulphate preparations
- Ionic water-soluble iodine preparations
- Non-ionic water-soluble iodine preparations
Barium Sulphate
White, chalky material
Used exclusively in the gut
* CONTRAINDICATED IF GUT PERFORATED
aspirated may cause pneumonia
sequence X-rays every 15-60mins
Ionic Water-Soluble Iodine Preparations
injected into bloodstream
* Anaphylaxis rare but a possibility
* Excreted by kidney
* Outline upper urinary tract
Ionic water-soluble iodine preparations
- Sodium Diatrizoate
- Sodium Iothalmate
- Sodium Ioxaglate
Non-Ionic Low Osmolar Water-Soluble Iodine Preparations
Myelography
IV studies
cisternal or lumbar puncture
Shows opacification of the CSF demonstrating the spinal cord
Barium liquid amount
5-50ml
Portal venography
Assess blood flow through liver
Dacryocystorhinography
Assess naso-lacrimal duct
patency
Angiography
Assess size and location of
arteries or veins
Bronchography
Assess the respiratory tree
Computed Tomography (CT Scanning)
detailed cross-sectional radiograph
banana shaped detector
1x360° lap =1,000 profiles
Measured in Hounsfield units
Nuclear Medicine
(Scintigraphy)
Administration of a radioactive
pharmaceutical = isotopes/ Gamma
Two Licenses must be obtained
from Environmental Agency for scintigraphy
Registration
(Keeping and using isotopes)
Authorisation
(Governing the accumulation and
disposal of radioactive waste)
Common sites Scintigraphy is used?
Bone Scintigraphy
Renal Scintigraphy
Thyroid Scintigraphy
Portal Scintigraphy
Magnetic Resonance Imaging
MRI
MRI create detailed images of the
body or brain by applying nuclear magnetic resonance
T1-weighted scan
- Fluid is dark
T2-weighted scan
Fluid is bright
Sound wve frequency of ultrasound
2.5-15 MHz
Transducer
Electric current causes crystals
to vibrate and change shape
- Piezoelectric effect
Ultrasound linear array
Piezoelectric crystals in line and
image is rectangular
sector scanner
Crystals closer together, small
patient contact area needed
Triangular image showing
deeper tissues more effectively
Echogenicity
differences in
overall brightness of tissue
Anechoic
black
Hypoechoic
Darker than normal
Hyperechoic
Brighter than normal
Endoscopy
Optical devices giving visual
access to inside the body
Rigid Endoscopes - Uses
- Otoscopy
- Rhinoscopy
- Tracheoscopy
- Colonoscopy
- Vaginoscopy and
urethrocystoscopy - Laparoscopy
- Thoracoscopy
- Arthroscopy
