Principles of radiography Flashcards
How far away from the primary beam should you be at exposure?
2m
When should you use a grid?
When the tissue depth of area we are radiographing is over 10cm
Why are grids beneficial?
They reduce amount of scatter radiation & improve contrast of image
What are the 2 types of grids?
Stationary
- placed on top of cassette on tabletop
Moving
- cassette is placed in bucky tray underneath in-built grid
Which positioning aid is radiopaque (would appear in an x-ray image?)
A. foam wedge
B. tape
C. Trough
D. sandbag
D. Sandbag
What should you do first?
A. Collimate beam to x-ray cassette
B. put grid in bucky tray
C. centre beam over area of interest
A. collimate beam to x-ray cassette
Why is it important to collimate as specifically as possible?
Reduce scatter
The area of interest should be … to the cassette
Parallel
True or false:
A L/R marker should be included on every radiograph
True
Altering the kV affects what?
Contrast
Why is correct X-ray exposure important?
Ensures better visualisation of anatomy by balancing contrast & density for optimal diagnostic image
What does mA (milliampere-second) control in radiography?
Controls no. of electrons crossing tube
Affects no. of X-rays produced
Does NOT affect contrast, but does affect radiographic density (degree of film blackening)
What does kV (kilovoltage) control in radiography?
Controls number & speed of electrons crossing tube
Affects X-ray penetration & image contrast
Higher kV = greater penetration & better contrast
If kV is too high, X-rays pass straight through patient, reducing contrast
How do over-exposure and under-exposure affect an X-ray image?
Over-exposure = Image appears too black (too many X-rays penetrate)
Under-exposure = Image appears too white (not enough X-rays penetrate)
Why is correct positioning important in radiography?
Ensures consistent diagnostic-quality images
Reduces repeat exposures, minimising radiation exposure
Saves time and resources in clinical practice
What does “Pink Camels Collect Extra Large Apples” stand for in radiography?
Pink – Positioning
Camels – Centring
Collect – Collimation
Extra – Exposure
Large – Labelling
Apples – Artefacts
How do you position a patient for an ML elbow radiograph?
Place in lateral recumbency (affected side down)
Retract contralateral limb dorsally to prevent superimposition
Ensure elbow is parallel to cassette
Centring: Over medial humeral epicondyle
Collimation: Include distal 1/3 humerus & proximal 1/3 radius/ulna
How do you position a patient for a CrCd elbow radiograph?
Place in sternal recumbency
Extend affected limb cranially
Elevate head with foam block to avoid interference
Ensure humerus, radius & ulna are in a straight line
Centring: Over humeral epicondyles
Collimation: Include distal 1/3 humerus & proximal 1/3 radius/ulna
How do you position a patient for a VD hip radiograph?
Dorsal recumbency, support with trough/sandbags
Extend & rotate hindlimbs medially, securing with tape
Ensure pelvis is straight (equal obturator foramina size)
Centring: Cranial edge of pubis
Collimation: Ilial wings → Mid-femur
How do you position a patient for a DV thoracic radiograph?
Sternal recumbency, elbows symmetrically positioned
Extend neck slightly, place on foam block
Centring: Slightly caudal to scapula (midline)
Collimation: Thoracic inlet → Diaphragm
Expose at peak inspiration
How do you position a patient for a right lateral thoracic radiograph?
Right lateral recumbency, extend forelimbs cranially
Place foam wedge under sternum for proper alignment
Centring: Caudal edge of scapula, halfway down thorax
Collimation: Thoracic inlet → Diaphragm
How do you position a patient for a VD abdominal radiograph?
Dorsal recumbency, support with trough
Ensure spine is straight, hindlimbs flexed
Centring: Midline, caudal edge of last rib
Collimation: Diaphragm (rib 7) → Femoral trochanters
Expose during expiratory pause
How do you position a patient for an ML stifle radiograph?
Lateral recumbency, affected stifle down
Retract contralateral limb dorsally
Centring: Medial femoral epicondyle
Collimation: Distal 1/3 femur → Proximal 1/3 tibia/fibula
What are the 2 standard views taken for a canine stifle radiograph?
Medio-lateral & caudo-cranial views
How is the dog positioned for a medio-lateral stifle projection, and what technical considerations apply?
Dog is in lateral recumbency with limb to be imaged against table, flexed at 90 degrees
Upper limb is moved out of way with rope tie or sandbag
Foam pad should be placed under hock to keep tibia parallel to table & sandbag is used to stabilise hock
Collimation should include 50% of femur & tibia/fibula, centered on stifle joint or slightly distal (tibial tuberosity)
L/R label should be used
How can you tell if a lateral view is well-positioned?
Femoral condyles should be superimposed without rotation
Label the stifle
How is the dog positioned for a caudo-cranial stifle view, and what are the key technical factors?
Dog is in ventral recumbency with affected limb extended caudally
Sandbag on pelvis helps maintain hip extension, while opposite hind limb is lifted laterally with sandbag to keep affected limb non-rotated
Limb should be rotated so patella is in midline
Collimation should be centered on middle of stifle joint, including 50% of femur & tibia/fibula, plus surrounding soft tissues
L/R label should be used.
How can you tell if a caudo-cranial view is well-positioned?
Femoral condyles should be of equal size & patella should be in midline, ensuring good visualisation of joint space
Label the stifle
Why is the cranio-caudal view less commonly used, and what adjustments are needed?
It can cause magnification distortion & is difficult to achieve without rotation
Femur needs to be rotated medially for proper positioning
What are the main categories of skeletal disease?
Skeletal diseases can be congenital, developmental, traumatic, infectious, neoplastic, metabolic, or degenerative
What is going on in these joints?
Normal joint vs Joint effusion (a sign of some diseases)
accumulation of excess fluid in joint
What is going on in these joints?
Cranial movement of tibia with cranial cruciate ligament rupture (progressive worsening from A to D) (i.e. traumatic)
What is going on in this joint?
Chronic stifle arthrosis (i.e. degenerative [could be secondary to traumatic])
Lots of new bone (osteophytes)
Joint effusion
Underlying cause often not evident
What is going on in this joint?
Osteochondrosis (i.e. developmental)
Radiolucent defect with surrounding sclerosis
Could be seen years later as chronic arthrosis
What are the 2 standard views taken for canine shoulder radiograph?
Medio-lateral and caudo-cranial
How is the dog positioned for a medio-lateral shoulder radiograph, and what technical considerations apply?
Dog is in lateral recumbency with limb to be imaged against table
Limb is pulled into extension using rope tie to separate shoulder from neck soft tissues
Upper limb is moved caudally with rope tie
Neck is flexed dorsally & secured with sandbag to move cervical spine away from shoulder joint
Foam pad is placed under chest to ensure parallel alignment & assist shoulder extension
Collimated to include distal 50% of scapula, proximal 50% of humerus & soft tissues cranial & caudal to shoulder
Centre of collimation should be shoulder joint (just distal to acromion)
Use L/R label
How can you tell if a lateral shoulder radiograph is well-positioned?
Joint space should be well visualised with no overlying tissue (e.g. opposite limb, neck tissue, trachea, cervical spine)
Some radiographers deliberately overlay trachea to increase contrast
Label the shoulder
How is the dog positioned for a caudo-cranial shoulder radiograph, and what are the key technical factors?
Dog is in dorsal recumbency with affected limb pulled cranially into extension & slightly away from midline
Sandbag may be used to push head & neck slightly away from limb
Scapula & humerus should be aligned along long axis
Centre at middle of shoulder joint (just distal to acromion)
Collimate to include distal 50% of scapula, proximal 50% of humerus & lateral & medial soft tissues
Use L/R label
How can you tell if a caudo-cranial shoulder radiograph is well-positioned?
Scapula & humerus should be in line with each other & proper centering on joint allows good visualisation of joint space
Label the shoulder
What is going on here?
Medial shoulder luxation
commonly traumatic & involves displacement of humeral head medially
What is going on here?
Osteochondrosis (i.e. developmental)
- Loss of rounded contour of caudal surface of humeral head
- Radiolucent defect
- May have surrounding sclerosis
- May have calcified free body in joint
What is going on here?
Chronic shoulder arthrosis
- Lots of new bone (osteophytes)
- Underlying cause often not evident
