1 Radiology Of MSK Flashcards
How do x rays work?
A beam of electrons are projected through an object onto an image detector
What are the 4 main densities?
Most dense - brightest
Bone
Soft tissue
Muscle/fat
Air
Least dense - darkest
Advantages of x rays
Quick
Readily available
Inexpensive
Can be portable
Disadvantages of x rays
Ionising radiation
Poor soft tissue contrast resolution
Roles of x ray in MSK imaging
- initial imaging for skeletal trauma (fracture), acute bone/joint injury (joint dislocation)
- initial evaluation of chronic bone or joint pathologies
What is chronic arthritis?
Loss of joint space due to wear and tear of cartilage
Fracture definition
Complete or incomplete break in the continuity of the bone
Name the 7 types of fractures
Linear
Transverse
Oblique non displaced
Oblique displaced
Spiral
Green stick
Comminuted
Transverse fracture
Crosses bone at right angle to long axis of bone <—>
Linear fracture
Parallel to long axis of bone ^
Oblique non displaced
Diagonal
Aligned edge of fracture
Oblique displaced
Diagonal
Non aligned edge
Greenstick fracture
One side of cortex broken, one side in tact
Who are greenstick fractures more common in?
Children
Comminuted fracture
More than one break
Multiple small fragments
What are the three phases of fracture healing?
Inflammatory phase
Reparative phase
Remodelling phase
Describe the inflammatory phase
Hours-days
No radiographic callus
Haematoma formation
Tissue death
Inflammation/cellular proliferation
Haematoma definition
Solid swelling of clotted blood
Callus defintion
Thickened/hard part of skin/soft tissue
Describe the reparative phase
Days-weeks
Callus on x ray
Angiogenesis
Soft (fibrocartilaginous) callus formation
Hard callus formation
Angiogenesis defintion
Development of new blood vessels
Describe the remodelling phase
Months - years
Fracture line becomes completely obscured
What does CT stand for?
Computed tomography
How does a CT scan work?
Uses radiation to build cross sectional images/slices which can be made into 3D images
How long do CT scans take?
A few minutes
What can CTs be used for?
Detailed images of bone structure and soft tissue
To guide infections, biopsies and aspiration in real time
Spiral fracture
Fracture line spirals round in multiple planes
Epiphyseal separation fracture
Fracture line extents through unfused growth plate
Who are epiphyseal separation fractures more common in?
Overweight young boys during rapid growth spurts
Disadvantages of CT
- Use radiation - more than x ray
- Motion artefact if patient moves so patient must remain still
- Poor soft tissue detail compare to MRI
Interpreting CT scans
Densities measured in Hounsfield units HU
< 0 HU dark e.g. air, fat
0 - 40 HU shades of grey e.g. soft tissue
> 100 HU white e.g bone
What appears white, shades of grey and dark on a CT scans?
White - bone
Shades of grey - soft tissue
Dark - air, fat
What can be used to see different structures clearer in CT?
CT windowing
What does MRI stand for?
Magnetic resonance imaging
How does an MRI work?
A strong magnet is used to generate a magnetic field which causes the protons in hydrogen atoms (body is mainly water) to line up.
Radio frequency signal pulses displace the alignment
Protons realign after pulses stop which emits a signal
Signal is made into image
What are MRIs used for in MSK medicine?
Define normal anatomy
Detect pathology
How will most MSK pathologies appear on fluid sensitive sequences?
Bright
How do fat and fluid look on T1 weighted images?
Fat bright
Fluid dark
How does fat and fluid appear on T2 weighted images?
Fat and fluid appear bright
Advantages for MRI
- excellent soft tissue (tendons, ligament, muscles imaging
- detailed anatomy of joints
- excellent bone marrow imaging
Disadvantages of MRI
Noisy
Claustrophobia
Takes a long time 40-60 mins patient must stay still
Doesn’t work with meal/electronics e.g. pacemakers
Questions of ask patient before MRI
Claustrophobia
Wearing any metal or pacemakers?
Advantages ultrasound
No radiation
No contraindications/side effects
Excellent superficial soft tissue resolution
Excellent for tendons and peripheral nerves
Dynamic imaging
Fluid collections
Superficial foreign bodies
Disadvantages of ultrasound
Operator dependent
Poor deep tissue resolution
Limited bone and intra-articular imaging
How does nuclear medicine work?
- radioactive material and carrier molecule injected into body and travels to intended part of body
- material decays via gamma radiation which is emitted and detected by gamma plates
- image is created
What is nuclear medicine used for?
To asses areas of metabolically active bone
- bone forming metastatic lesions
- healing fractures
- areas of osteomyelitis
