L3: Radiology of the musculoskeletal system Flashcards
How do you produce X-rays?
Beam of electron
Through sample
Onto detector
In X-rays how does density have an impact?
Density affects amount of radiation absorbed
Denser material= more absorbed= less of detector= appears white
In X-rays what appears white and what appears black?
White = bone (dense materials) all radiation absorbed Black= air (less dense) radiation hits detector
What are the advantages of x-rays?
Inexpensive
Quick to obtain
Readily available
What are the disadvantages?
Uses ionising radiation
Poor soft tissue contrast resolutions
What are X-rays used to detect bones?
Fractures Dislocation Chronic bone or joint pathologies --> osteomyelitis Arthritis --> chronic and rheumatoid
What can you see on X-ray of long bones?
Periosteum
Cortex- thick diaphysis, thin epiphyses/ metaphyses
Medullary cavity
Articular cartilage- appears as joint space
What is a fracture?
Partial or complete break in continuity of a bone
What types of fractures are there?
Transverse- one side to other, right angle to axis
Linear- parallel with bone
Non displaced oblique- Diagonal break, bone stay alligned
Displace oblique- Diagonal break, bones don’t stay inline
Spiral- break goes around bone, start and finish not at same point
Compression- bone crumbles,
Greenstick- children mainly, incomplete fracture, bone bends and cracks
Epiphyseal separation- fracture extends through growth plate, separate epiphyses and diaphysis
What happens to bones as children grow up?
Birth- Long bone separate ossification centres
–> primary (diaphysis), secondary (epiphysis)
–> separated by growth plate–> less mineralised –> appear opaque on x-ray
Child grows –> growth plate thinner –> close
Bone gradually calcify
What influences proliferation and transformation of cell in growth plate? How can this be used?
Growth hormone- promotes
Thyroid deficiency inhibits
Bone age study –> determine MSK maturity
Significant difference between bone and actual age–> pathology (early or late puberty, thyroid deficiency etc…)
What are the 8 simplified steps of bone healing? (NOT body log version)
Haematoma formation
Tissue dies
Inflammation/ cellular proliferation
Angiogenesis/ Formation of granulation tissue/ Procallus
Soft (fibrocartilagenous) callus formation
Lamellar bone
Remodelling
What are the three phases in radiology? How long do they last?
Inflammatory phase–> hours to days
- haematoma formation
- tissue death
- inflammation/ cellular proliferation
Reparative phase –> days to weeks –> mineralisation seen, eventually trabecular seen
-angiogenesis/ formation of granulation tissue/ procallus
-Soft (fibrocartilagenous) callus formation
- Lamellar bone
Remodelling –> months to years –> fracture line obscured
How does CT scan differ from X-rays ?
Uses narrow X-rays
Images slices
Creates 2D or 3D image
What are the advantages of a CT scan?
Better soft tissue detail
Whole body- short period of time
Manipulation of image with computer software
Subtle fractures seen
What are the disadvantage of CT?
More ionising radiation
Motion artefact (move-blurs image)
Obese- cant fit in scanner
Poor soft tissue compared to MRI
How is the density of tissue measure in CT? How does this compare to whats seen on a scan?
Measured in Hounsfield units
Tissues <0HU dark –>air, water
Tissue 0-40 HU Grey –> soft tissue
Tissue >40HU white –> bone
What do ‘windows’ show?
CT scan manipulate grey scale
view tissue of interest
How does MRI work?
Uses magnetic to cause proton in H atoms to line up
Adds radiofrequency pulse
Causes unalligned (facing wrong direction) to flip
Remove Radiofrequency energy released
Signal detected
Creates image
What are the advantage of MRI?
Non ionising radiation
Better for imaging soft tissue
Image manipulated
What are the disadvantages of MRI?
Micro-architecture of bone poor
Takes longer
Claustrophobic
Electronic or metal devices must be removed
What the difference between T1 and T2 weighted images?
T1 weighted- Fat white
T2 weighted- Water and fat white
Injection of dye may also improve image (gadolinium)
What is STIR MRI?
Fluid senstive sequence, fat signal suppressed so fluid is seen better
How does ultrasound (ultrasonography) work?
High frequency sound waves
Tisses deflect wave back to transducer
Analysed–> creates image
What are the advantages of ultrasound?
Non ionising Non invasive Excellent soft tissue- superficial Tendons and peripheral nerves Fluid collection Superficial foreign bodies Dynamic imaging Image guided MSK intervention
What are the disadvantages of ultrasound?
Operate dependant
Limited bone and intra-articular imaging
Poor deep tissue resolution
What is nuclear medicine?
Uses radio-labelled isotopes
Attached to biologically active drugs
Assess metabolically active bone- diseased, healing, osteomyelitis
Why is ionising radiation bad? What precautions should be taken?
Deposit energy in any organ or tissue - DNA damage Rapidly dividing cells most susceptible Medical personal--> led aprons Minimise exposure--> films badges Low dose radiation Only when necessary
