MSK 3 - MSK Radiology Flashcards
How do X-rays/plain radiographs work?
What are the advantages + disadvantages?
- X-rays passed through an object, image generated on a detector plate. More dense materials (bone, metal) absorb more X-rays and appear whiter on image.
(+) Quick, readily available, inexpensive
(-) Uses ionising radiation (minimal compared to CT) + poor soft tissue contrast resolution.
What are the 2 main roles for radiographs/X-rays in MSK imaging?
What is disrupted when a fracture occurs?
1) Initial imagine of skeletal trauma/bone injury - e.g.: fractures and joint dislocations
2) Evaluation of chronic bone/joint pathologies, e.g.: chronic osteomyelitis and chronic arthritis
- The cortex of bone is disrupted in fractures
What is a fracture?
What types of fractures can be observed by imaging?
- A complete or incomplete break in the continuity of the bone
- Transverse, Linear, Oblique displaced/non-displaced, Spiral, Greenstick + Comminuted
What are the 3 phases of fracture healing and the associated changes that occur + changes seen on X-rays?
1) Inflammatory Phase - haematoma formation, death of tissue + inflammation (days to hours) - no callus formation on X-ray
2) Reparative phase - angiogenesis, accumulation of granulation tissue. Soft (fibrocartilaginous) callus formation, then consolidation into hard callus (days to weeks) - callus formation seen on X-ray
3) Remodelling phase - Remodelling of callus so fracture lines become obscured (months to years) - see union on X-ray.
NB: callus = connecting bridge across fracture during repair.
What is a CT scan?
What are its advantages + disadvantages?
What planes can CT scan in?
- Computed tomography - uses radiation to build cross-sectional images of the body.
(+) Soft tissue detail better than X-rays, whole body CT can be performed in minutes, subtle un-displaced fractures better visualised. Can create 3D images.
(-) Radiation dose higher than X-ray, motion artefact produced if patient moves, poor soft tissue detail compared to MRI (still better than X-ray).
- Primarily axial (transverse) but also sagittal and coronal (frontal)
How is density of body tissues measured in CT scans?
What colour do different densities show?
- In Hounsfield Units (HU) - water = 0HU
- <0 = dark/black (air + fat)
- 0 - 40 = grey (water + soft tissue)
- > 100 HU = white (bone)
How does MRI work?
Does it use ionising radiation?
- Utilises radio-frequency pulses to produce high quality cross-sectional images in any plane
- Does not use ionising radiation
What are the 2 objectives of MRI MSK scanning?
What are MSK MRI’s used for?
1) Definition of normal anatomy
2) Detection of pathology
- Assessment of bones, joints and associated soft tissues
- Assessment of MSK infection, e.g.: osteomyelitis
What are the 2 types of MRI sequences?
What colour does fluid + fat appear on them?
T1 = looks at fat + anatomy. Fat is white, fluid is dark grey T2 = looks at fluid. Fat is lighter grey, fluid is white
What are the advantages and disadvantages of MRI scans?
(+) Excellent soft tissue imaging (ligaments, tendons etc)
(+) Detailed anatomy of joints
(+) Excellent bone marrow imaging
(-) Scan is long 45-60 mins. Patient has to stay still
(-) Very noisy
(-) Difficult for claustrophobic patients
(-) Non-compatibility with metallic/electronic devices like pacemakers.
What are the advantages and disadvantages of ultrasound MSK scans?
(+) No radiation/adverse effects
(+) Excellent soft tissue imaging
(+) Dynamic imaging
(-) Operator dependent
(-) Poor deep tissue resolution
(-) Limited bone and intra-articular imaging
How does nuclear imaging work and what is it used to assess?
- Radioisotope-labelled, active drugs administered to serve as a marker of biological activity
- Assess area of metabolically active bone e.g.:
- bone-forming metastatic lesions, healing fractures, areas of osteomyelitis.
