Muscle L5/6: Musculoskeletal Imaging Flashcards
What are the 4 reasons for using imaging for MS conditions?
- Make an accurate tissue diagnosis
- e.g. acute fracture … not always appropriate (e.g. low back pain, knee pain)
- MRI in 2 different positions- give inaccurate conditions
- Rule out other pathology (red flags)
- e.g. tumour
- Refer to GP who would refer for appropriate imaging
- Determine prognosis or to track a disease
- e.g. osteoarthritis
- Can have a look @ what stage
- Indications for surgical intervention
- e.g. ACL rupture MRI; can pick up clinically (with subjective& physical)
- end-stage osteoarthritis x-ray (pain that can’t manage- knee replacement)
What are the 3 concepts of APA (Choosing widely)?
- Don’t request imaging for patients with non-specific lower back pai and no indicators of a serious cause for lower back pain
- Don’t request imaging on the cervical spine in trauma patients, unless indicated by a validated decision rule
- Don’t request imaging for acute ankle traumas unless indicated by the Ottawa Ankle Rules (localized bone tenderness or inability to weight bear as defined in the rules)
What are the 5 principles for using imaging for MS conditions?
- understand imaging results
- what radiologists send back
- only order imaging that will influence management
- ongoing pain to clear fracture (eg. talus)
- explain the imaging to the patient
- provide relevant clinical findings on the referral form
- don’t have to refer to GP, can refer straight to radiologist
- Need to say “suspected..etc”
- Eg. “suspected PFJ OA- add skyline view imaging”
- work with radiographers & radiologists
Radiography: How does it work?
- X-rays (electromagnetic radiation) in a fan beam are directed from a fixed tube through the body region of interest
- X-rays are absorbed, scattered or transmitted through different tissues at different rates
- Transmitted and scattered x-rays are detected by a detector device
X-rays (electromagnetic radiation) in a fan beam are directed from a _____ through the body region of interest
fixed tube
X-rays are _______, _______or ______through different tissues at different rates
absorbed; scattered; transmitted
Transmitted and scattered x-rays are detected by a _______.
detector device
Radiography: What tissues are imaged?
- Tissues containing calcium (e.g. bone) absorb more x-rays than soft tissue …produces high contrast on detector - appears brighter/white
- Bone – fractures, alignment, joint spacing, tumours, etc.
- Eg. calcification in tendon (will show up) Spacing – OA component (wear down)
Radiography: What are 2 advantages?
- Cheap and fast
- No appointment needed
- $50 (depends on area)
- Widely available
- Can be mobile
Radiography: What are 3 disadvantages?
- Uses ionizing radiation (low to medium dose)
- Cant differentiate soft tissue
- Only see bone (implying)
- 2D image of a 3D structure
- Can’t see rotation
Radiography: What are 2 contraindications?
- Pregnancy
- Breastfeeding
Radiography: When would radiography be used?
- Bony injury
- Eg. fracture; hairline; dislocation
- Good entry/starting point
Radiography: What are the 3 different types of x-ray view?
- Anteriorposterior
- Lateral
- Skyline
Radiography: Grade 0 of OA
No OA
Radiography: Grade 1 of OA
possible osteophytic lipping, doubtful JSN
Early OA
Radiography: Grade 2 of OA
definite osteophytes, possible JSN
Radiography: Grade 3 of OA
moderate multiple osteophytes, definite JSN, some sclerosis, possible bone contour deformity
Radiography: Grade 4 of OA
large osteophytes, marked JSN, severe sclerosis, definite bony contour deformity
CT scanning: How does it work?
Computerised x-ray procedure X-ray tube and detector rotate around the patient Narrow beam of x-rays is aimed at the target region and rotated quickly around the body Produces signals that are processed to generate crosssectional images
- can be viewed as slices
- reconstructed to produce 3D image = clear images (used for surgery)
CT scanning: What tissues are imaged?
Bone – fractures in small bones, anatomically complex regions
CT scanning: What are 4 advantages?
- Relatively cheap; fast; widely available
- Higher resolution than x-ray
- Defines bone detail and detects calcification better than MRI
- 3D data- geometrically accurate
CT scanning: What are 3 disadvantages?
- Using ionizing radiation (medium to high dose)
- Lower soft tissue contrast (vs. MRI)
- Often requires contrasts- risk Substance injected (intra-venous)
CT scanning: What are 3 contraindications?
- Pregnancy
- Breastfeeding
- Children
CT scanning: When would CT scanning be used?
- Complex fracture (small, difficult to see)
- Can’t be picked up on x-ray
- Complex orthopedic surgery
Bone scan: How does it work?
Scintigraphy
Intravenous administration of radioisotope (bisphosphonate) –> binds to hydroxyapatite at sites of osteogenesis (active bone formation)
Scan performed with gamma camera – detects gamma radiation emitted from radioisotopes
- 2D image (frontal plane; anterior or posterior)
- 3D image (single photon emission CT [SPECT]) – detectors rotate around body
Bone scan: What tissues are imaged?
Bone- stress fractures, tumour, etc.
Black areas= osteogenesis
Bone scan: What are 2 advantages?
- can be combined with CT – anatomy & function
- may detect earlier stages of bony injury
Bone scan: What are 4 disadvantages?
- relatively high radiation dose
- low resolution images (show uptake)
- slow (long period to keep still)
- reasonably expensive
Bone scan: What are 2 contraindications?
- pregnancy
- breastfeeding
Bone scan: When would bone scanning be used?
Osteogenesis occur- bone healing should have occurred
Ultrasound: How does it work?
Sound waves (1-18MHz) are produced by a piezoelectric transducer
Waves travel through the body tissues
- partially reflected anywhere there are acoustic impedence changes in the body (e.g. interface between different tissues)
- some reflections returned to transducer, sound waves converted to electrical pulses, transformed into digital image (time, strength of echo)
Need coupling gel between transducer and skin (water-based)
Ultrasound: What tissues are imaged?
Ligaments, tendons, muscle, nerves – not bone (bone = black void)
Ultrasound: What are 5 advantages?
- Cheap; fast; widely available; portable
- Able to image soft tissue; high resolution
- Can perform dynamic imaging (real-time)
- Can interact with patient to correlate symptoms & findings
- Safe (no ionizing radiation)
Ultrasound: What are 3 disadvantages?
- Small field of view; can can some image distortion
- Unable to penetrate bone & air
- Enough gel
- Image quality depends on skill of operator
Ultrasound: What are the contraindications?
N/A
Ultrasound: When should ultrasound be used?
- Hypoechoic region thickening: not penetrating completely
- Neovessels: body’s healing effect
MRI: How does it work?
- Magnets produce a strong magnetic field (3.0T) that forces the protons in water molecules in the body to align with that field
- Radiofrequency current is then pulsed through the body – stimulates the protons, which spin out of equilibrium against the pull of the magnetic field
- When the radiofrequency current is turned off, MRI sensors detect the energy released when the protons realign with the magnetic field
- Different tissues have different times for proton realignment, and different amounts of energy release – appear different on MR image
- Signal detected by coil close to target body region
MRI: What tissues are imaged?
All tissue
Can see everything (bone and tissue)
MRI: What are the 4 common MRI sequences?
- T-1 weighted
- Proton density- weighted
- T2-weighted
- STIR
MRI: What is a T1-weighted MRI?
- sharp anatomical detail
- shows bone marrow
- good for meniscal pathology
- lacks sensitivity to detect soft tissue injury
fat = bright
muscle = intermediate
water, tendons, fibrocartilage = dark
MRI: What is a proton density- weighted MRI?
• good for menisci and ligaments
fat = bright / intermediate
water = intermediate
calcium, tendons, fibrocartilage = dark
MRI: What is a T2-weighted MRI?
- highly sensitive for most soft tissue injuries, especially tendons (or muscular)
- Abnormal tendons have high signal intensity (bright) – contrasts with the black of normal tendon
water = bright
fat = intermediate
muscle, hyaline cartilage, fibrocartilage = dark
MRI: What is a STIR MRI?
- highlights excess water which may occur due to bone stress, bone marrow oedema, joint fluid and soft tissue pathology
- use for bone stress injuries or subtle fractures not detectable on x-ray better than T weighted
water = very bright
fat, muscle menisci = dark
MRI: What are 3 advantages?
- Excellent soft tissue contrast; geometrically accurate
- Non-invasive; no ionizing radiation
- Can scan in any plane; 3D image capability
MRI: What are 3 disadvantages?
- Bone resolution not as clear as CT
- Expensive; slow (keep still); low availability
- 10 mins- no movement at all
- Not-weighted bearing imaging (at present)
MRI: What are 3 contraindications?
- Any implanted metal
- Eg. placemaker, aneurysm clip
- Claustrophobia
- Small tunnel
- It’s a really, really big magnet
- Has to be declared MRI safe
MRI: When would MRI be used?
Any structures- if other imaging options don’t fix (make sure to weight up time and cost)
SUMMARY for x-ray, CT, bone scan, ultrasound, MRI
x-ray: bone CT: more bone detail (trabeculae) Bone scan: Osteogenesis (bony activity) Ultrasound: Soft tissue tendon, ligaments, muscle, nerves, not bone MRI: Everything can order multiple sequences (eg. STIR &T-1/T-2 weighted)
