Lecture 2- MSK radiology Flashcards
How is an X-ray produced
a projectional image generated. by passage of x-rays through an object
the iamge is generated on a detector plate called an x-ray detector
when the x-ray hits the plarte, it turns black- the amount of blackned depends on the number of x-rays penetrating the object and hitting the plate
x-rays only travel in srraight lines- no deflection by bones or metalwork
X-ryas are absrbed by dense materials
if X-ray white
ense
◦X-rays are absorbed by dense materials - wont hit the plate ‣ Bones
‣ Metals
if x-ray dark
If darker
◦Less dense
‣ Adipose
‣ Air
advantage of x-ray
- quick
- Available
- Inexpensive
disadvantage of x-ray
involve radiation
Poor soft tissue contrast resolution
role of radiographs
- Initially imaging of choice for skeletal trauma/acute bone or joint injury:
- Fracture
- Joint dislocation
- Also used for initial evaluation of chronic bone or joint pathoglogies
- Chronic osteomyelitis
- Chronic arthritis e.g. osteoarthritis, rheumatoid arthritis
which x-ray view is normal
posterior anterior
medullary bone found
in the diaphysis centre
- less dense
cortex
made of cortical comapct bone
- thick and dense
outermost layer of bone
periosteum
undispalced fracture of the tibia
a fracture is
complete or incomplete break in the cortex or continuity if the bone
Sometimes nutrient vessels look like fracture
Displacement
- out of line slightly
cartilage is
radiolucent so appears as joint space
types of fractures (7)
- transverse
- linear
- oblique nondisplaced
- oblique displaced
- spiral
- greenstick
- comminuted
most fractures look like a
lucent line
fractur
always describe
which side you are looking at
draw transverse
draw linear
draw oblique nondisplaced
draw oblique discplaced
spiral
draw greenstick
like a twig being bent in half
draw comminuted
fracture displacement
compression fracture
if a fracture is hard to see, what may make it clearer
a CT
radiogrpahic changes seen during childhood
ossification
bone growth
calcification
deposition
normal paediatrics x-ray
what occurs to the bone during childhood to puberty
ossification of epiphysis
ossification of carpal bones
basic fracture healing process
1) haematoma formation
2) procallus formation
3) bony callus formation
4) bone remodelling
the inflammatory phases of fracture healing
- haematoma formation
- tissue death
- inflammation/ cellular proliferation
- hours to days
reperative phase of fracture healing
- angiogenesis/ granulation tissue/ procallus
- soft (fibrocartilaginous) callus formation
- consolidation/ hard callus formation
remodelling phase
duration- months to years
- remodelling of the callus so that the fracture line becomes completely obscured (radiographic union)
x-ray of bone repair
CT scans use
radiation to build cross sectional images of the body
- thin slices give detailed info about the bone structure and pathology
Soft tissue detail is better than plain X-ray
How long does a CT take
Whole body CT can be performed in a short time to look for bone or soft tissue injury
◦Slower than x ray
what type of fractures are better to view on a CT than x-ray
Subtitle in-displaced fractures are better visualised on CT scan than plain x-ray
Spinal fractures and other complex rate like pelvic fractures can be seen in great detail- aid pre-
operative planning
Slices can be reformatted to create multiple planar and 3D images
disadvantages of CT
- radiation higher than x-ray
- Motion artefact if patient moves - elderly confused
- Poor soft tissue detail compared with MRI (but better than x-ray)
in CT scans the density of body tissues is emasured in
hounsfield units (HU)
tissue <0 HU
appear dark
e.g. air, fat and water
tissue with 0- + 40 HU
shades of grey- soft tissue
tissue of >100 HU
appears white
- trabecular and cortical bone
CT great at looking at different tissues in different concentrations
window can be selected e.g. can see lungs or soft tissue
MRI
Utilises magnetic resonance of the hydrogen nuclei o produce high quality cross-sectional images of the body in any plane
no use of ionising radiation
Utilises radiofrequency pulses in presence of carefully- controlled magnetic field
musculoskeletal MRI fundamental objectives
◦Define normal anatomy
◦Detection of pathology
MRI is betetr than CT and X-ray at
assessing soft tissue
MRI can also be used in assessment of
MSK infection- osetomyelitits
MRi poor at showing
micro-architecture of the bone
two tyoes of sequences in MRI
T1 and T2
T1
Anatomy defining sequences
T2
fluid sensitive
- most MSK pathologies appear bright on fluid-sensitive sequences
advantages of MRI
- good detail: ligaments,tendons and muscle
- Excellent for bone marrow imaging
Disadvantages of MRI
scan are long time (45-60 mins)
Noisy
Claustrophobic
Non compatible with metallic/ electronic devices like pacemaker
advantages of ultrasound MSK imaging
- no radiation involved
- Excellent soft tissue resolution for superficial soft tissue
- Excellent imaging modality for assessment of tendons a nd peripheral nerves
- Fluid collection
- Superficial foreign bodies
- Dynamic imaging
- Excellent for image guided MSK intervention
disadvantages of ultrasound
- operator dependent
- Poor deep tissue resolution
- Limited bone and intra-articulation imaging
example of ultrasound
nuclear imaging
Radioisotope-labelled, biologically actve drugs that are administered to the patient to serve as a marker of biological activity
why is nuclear imagibng used
They are used to assess areas of metabolically active bone such as when trying to localise
◦Bone forming metastatic lesions
◦Healing fracture
◦Area of osteomyelitis
