L8 Imaging Fundamentals

Question 1

Order by increasing X-Ray densities:

soft tissue, bone, fat, air, metal

Answer 1

• air
• fat
• soft tissue
• bone
• metal

Question 2

radiolucent/radio opaque

Answer 2

• radiolucent: increased blackness
• radio opaque: increased whiteness

Question 3

MSK principles (musculoskeletal imaging)

Answer 3

• confirm identity of the patient
• at least two veiws (projections)
• alignment
• identify:
  
  • joint surfaces and joints
  • trabecular bones and lines: bone densities and normal shapes
  • bone outline
  • soft tissues: abscess and bruises
• growth plates: in children only
• invisible structures: need to infer info based on anatomical knowledge

Question 4

imaging modalities

Answer 4

• plain radiograph
• CT
• MRI
• ultrasound
• Nuclear scintigraphy

Question 5

X-Ray features

Answer 5

• good overview of bones and joints
• good for alignment
• some flexibility e.g. standing view, horizontal beam
• less contrast/spatial resolution than CT
• low radiation
• cheap and quick
• readily available

Question 6

MRI (Magnetic Resonance Imaging) features

Answer 6

• good spatial and contrast resolution
• great for soft tissue and bone marrow
• good for inside joints
• cross-sectional imaging
• imaging in multiple planes
• variable availabilty
• limited functional info
• contraindications (risks for patients w/ pacemaker, cochlear implant, aneurysm clips)
• more expensive
• long scan times

Question 7

difference between T1 weighted and T2 weighted MRI signal intensities

Answer 7

• corticol bone: both dark
• fluid: T1 = dark, T2 = bright
• muscle: intermediate
• fat: bright
• spinal cord: intermediate

Question 8

ultrasound features

Answer 8

• cross-sectional multi-planar images
• high frequency sound transmitted into body
• interacts with tissues: reflection, absorption, scatter
• reflection of sound when crosses between tissues of different acoustic densities
• images made up of sound waves reflected back from tissues
• operator dependent images: bad sonographer = bad image
• no radiaton
• good soft tissue contrast resolution (>MRI)
• best for superficial structures
• doesn’t see through bone
• clinical correlation at time of exm
• functional information
• low cost for MBS

Question 9

echotexture

Answer 9

brightness/darkness of the ultrasound

Question 10

echogenic/hyper-echoic

Answer 10

many reflectors: whiter and brighter e.g. fat

Question 11

echopoor/hypoechoic/anechoic

Answer 11

few reflectors, blacker image e.g. fluid

Question 12

CT features

Answer 12

• Uses X-Rays to form cross-sectional image
• CT image is tissue density map
• greater range of grey shades
• cortical or trabecular architecture of bone
• anatomy of complex joints
• fracture lines, small calcifications, calcified bondies, erosions, bone destructions
• good bony spatial and contrast resolution
• more radiation than plain films
• more expensive
• limited functional info

Question 13

features of bone scintigraphy

Answer 13

• injected technetium emits gamma rays - counted by scanner
• technetium taken up by osteoblasts
• bone scintigraphy assesses vascularity and osteoblastic activity
• sensitive but non-specific
• used to assess for metastases, infection, stress fractures, osteonecrosis, arthritis
• poor resolution though