15. Imaging in orthopedics Flashcards
What scans contain ionising radiation?
X-ray, CT, Radionuclide, bone scanning, DXA
What is the rule of two in orthopaedics?
Take 2 x-rays from different angles
What is an arthrogram?
Image of the inside of a joint
Uses contrast (air,iodine, gadolinium, aspiration) to see problem
Can combine it with therapeutic drugs
What is meant by a triple phase bone scan
1-2- show arterial flow or hypoperfusion
3-5 mins see blood pool or equilibrium images
4 hours- static or delayed image shows skeletal activity
What diseases are bone scans good for?
Occult bone pain Assessment of metastases Infection (bone) Trauma (stress fractures) Tumour evaluation (osteid osteoma, osteoblastoma) Paget's disease
Why is Fleurodeoxyglucose used in PET scans?
A good indicator of metabolic rate
Readily availale
Gets stuck in cells
Good for tumours, inflammation, infection
What does the DEXA in DEXA scan stand for?
Duel energy x-rayabsorpirometry
What are non-ionisng scans?
MRI
USS
How do MRI scans work?
Detect hydrogen ions in the form of water
Line up the ions using a mgnet
Hit it with radio signal- dsitort
When they relax then release an RF signal
What is meant by T1 and T2
T1- time taken for the nuclei to get back to longitudinal normal
T2- Time taken for the nuclei to get back to transverse normal
What two structures (relating to ortho) is there poor images from in an MRi
Cortical bone and tendinous structures
What do you see on a T1 and T2 image?
Fat bright- water dark-T1
Water bright- T2 (T2O)
When would you use CT vs MRI
MRI for soft tissue differentiation
CT for spatial resolution (small areas of bone e.g.)
MRI for multiple scans
CT for speed (e.g. trauma)
What ortho problems is an USS good for?
Erosions (10x superior to x-ray)
Just as good as MRI for synovitis, Rotator cuff, hind foot assessment
Suepriot to MRI for tendon and sheath
