Diagnostic Imaging

Question 1

Radiodensity

Answer 1

• Radiopacity
  
  • High density > absorb more xray > film less exposed > white
• Radiolucency
  
  • Low density > absorb less x-ray > film more exposed > darker
• Water density includes muscle, cartilage, tendon, blood, nerve, connective tissues

Question 2

Diagnostic Imaging Concepts

Answer 2

• Thicker material = more x-ray absorbed (less reaches film detector)
• Position depends on what want visualized
  
  • Closer to the film > lower magnification, higher resolution
• Need multiple images to determine 3D

Question 3

Different projections

Answer 3

Anterior Projection (PA)

• Patient anterior = film
• Patient posterior = xray

Posterior Projections (AP)

Left lateral Projections

• Patients left side faces film

Right lateral projection

Oblique (LAO, RAO, LPO, RPO)

• Can minimize superimposition by taking oblique image

Question 4

Computerized Tomography

Answer 4

Rotating x-rays -> sudoko > gradient > image

Axial images viewed as if feet pointed towards you

Question 5

Magnetic Resonance Imaging

(NMR)

Answer 5

• Nuclear magnetic resonance (NMR)
• Magnetic field and pulsed radio frequency waves > emitted energy from the body is collected/analyzed > image

Question 6

Echolocation

Answer 6

Ultrasound

• Sounds waves
• No radiation
• Uses:
  
  • Extension of physical exam
  • Diagnostic studies
  • Guiding needles and instruments for procedures

Echolocation

• Soundwaves > listen to return echo > locate objects
• Animals do this
• Pizielectric cystal vibrates > creates sound waves ~ 1-20 mhz

Question 7

Ultrasound Equipment

Answer 7

Equipment

• Machine
• Transducer
  
  • Different transcudvers > sound waves at different frequencies
  • Change in shape of the beam > how much can be seen
  • Increase frequency = decrease depth
  • Types
    
    • Linear
      
      • High frequency (10-18mhz)
      • Musculoskeletal / soft tissue
      • Cannot see joints well
      • Superficial
      • Up to 6cm deep
    • Curvilinear
      
      • Lower frequency
      • Abdomen and deep structures
      • Good penetration but low resolution
      • Wider field of view
    • Phased array
      
      • Lower frequency
      • Wide beam
      • Helps guide beam through hareas such as ribs
      • Good for cardiac imaging (echos)
• Gel
  
  • Clean sound wave transmittance

Question 8

Ultrasound Image

Answer 8

Image

• Computer creates a grey scale image based on how the sound wave moves through tissue and back to the transducer
• Color can be added to look at the flow of vessels
• Travel time of sound waves varies depending on the tissue
• Sound waves either:
  
  • Reflect
    
    • Bounce back to the transducer
  • Refract
    
    • Hit different objects
  • Scatter
  • Attenuate
    
    • Beam loses energy as tissue absorbs sound
    • Muscle and soft tissues attentuate
    • Lower frequency wave travel further and are less attenuated
      
      • Deep structures
      • Low resolution
    • Higher frequency waves are more attenuated (absorbed by soft tissue)
      
      • Superficial structures
      • Better resolution

Terms

• Hyperechoic
  
  • Bright
  • Bone/tendon because reflected
• Hypoechoic
  
  • Weak/low echo
  • Soft tissues (skin, fat)
  • Appear dark
• Anechoic
  
  • No echo (black)
• Isochoic
  
  • Equal echogenicity of 2 structures

Dynamic Imaging

• Allows to see test structures in motion
• Can correlate movements with pain and pathology of a structure
  
  • Impingement
    
    • Move arm and visualize
  • Joints
  • Ligaments
  • Subluxing tendons
  • Accentuates tears
  • Compressibility of structures (fluid/solid)

Question 9

Ultrasound Modes

Answer 9

• Doppler
  
  • Helpful in evaluating cardiovascular images
    
    • Regurgitation
  • Red = toward
  • Blue = away
  • White = sound waves bounce back
    
    • Bone
  • Black = sound waves bounce through
• Power Doppler
  
  • 5x more sensitive > used for low flow (shows small vascularity)
  • One direction
  • Evaluate tendons/tumors
    
    • Neovascularization

Question 10

Anistropy

Answer 10

• ~ artifact
• Change in echogenicity of a single structure dependent on the angle of the beam relative to the structure
• Solution!
  
  • 3-7 degree change in the probe may change echo
  • Tilt probe! To ensure accuracy and not anistropy
• Tendon (most effected) > ligament > nerve

Question 11

Ultrasound Buttons

Answer 11

• Frequency: depends on depth
• Depth
  
  • Curvalinar for superficial structures
• Focal zone
  
  • Maximizes resolution at area of interest
• Gain: controls brightness
  
  • Nerves are hypoechoic
  • Identify nerves by increasing gain (nerves remain dark)

Question 12

Muscle ultrasound

Answer 12

• Appearance of muscles
  
  • Sagittal (B)
    
    • Hypoechoic bundles of fibers with hyperechoic septae
    • Multipennate pattern: “feather” or “veins on leaf”
  • Transverse (A)
    
    • Hyperechoic septa and hypo-isoechoic muscle
    • “starry night”

Question 13

Tendon Ultrasound

Answer 13

• Appearance of tendon
  
  • Sagittal (A,C)
    
    • Hyperechoic and fibrillary
    • Non-branching, tightly packed
    • Non-compressible, non-vascular
  • Transverse (B,D)
    
    • Bristle pattern
  • A/B are normal images
  • C/D are abnormal images

Question 14

Bone Ultrasound

Answer 14

• Appearance of bone
  
  • Hyperechoic
  • Posterior shadows
    
    • Behind bone

Question 15

Cartilage Ultrasound

Answer 15

• Appearance of cartilage
  
  • Hyaline cartilage
    
    • Lines bone
    • Hypoechoic, non-compressible
  • Firbocartilage
    
    • Between bones
    • Hyperechoic or hypoechoic

Question 16

Nerve Ultrasound

Answer 16

• Appearance of nerve
  
  • Sagittal
    
    • Tram-track appeareance
  • Transverse
    
    • Follicular pattern
    • Honeycomb appearance

Question 17

Vessel Ultrasound

Answer 17

• Sagittal
  
  • Anechoic tubes
• Transverse
  
  • Round anechoic
• Veins
  
  • Compressible
• Arteries
  
  • Pulsatile and not compressible