FSP Class-5 - Sequences & Contrasts

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FSP Class-5 - Sequences & Contrasts
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2015-04-10 23:15:33
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FSP Class Sequences Contrasts
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FSP Class-5 - Sequences & Contrasts
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  1. PS
    • Pulse Sequence
    •   - to delay transverse (XY) magnetization as long as possible
    •   - identified by Flip Angle (FA) used
  2. Gold Standard of imaging
    Spin Echo Pulse Sequence
  3. Oldest and longest in scan timing
    Spin Echo Pulse Sequence
  4. Fills 1 K-Space line per TR
    Spin Echo Pulse Sequence
  5. SE Pulse Sequence
    • Spin Echo
    • - Gold Standard of imaging
    • - has 2 RF - starts w 90o, ends w 180o
    • - 90o - Stimulus (stimulate the P)
    • - 180o - Rephaser (correct inhomogeneities) at TE/2
    • - signal reading at TE
    • - oldest and longest in scan timing
    • - fills 1 K-Space line per TR
  6. Start w 90 followed by a train of 180
    FSE - Fast Spin Echo Sequence
  7. Causes blurring as MRI is a tradeoff b/w parameters
    FSE - Fast Spin Echo Sequence
  8. ETL
    Echo Train Length - # of 180 pulses after the 90 pulse in FSE Sequence
  9. Turbo Factor
    ETL (Turbo Factor) - Echo Train Length - # of 180 pulses after the 90 pulse
  10. Fills 2 K-Space per TR
    FSE - Fast Spin Echo Sequence
  11. Best for Pt w metal
    FSE - Fast Spin Echo Sequence
  12. FSE - Fast Spin Echo Sequence
  13. FSE Sequence
    • - Fast Spin Echo
    • - start w 90 followed by a train of 180 to fill the other k-space lines in the same slice
    • - each 180 is a k-space line in the same slice
    • - Difference - quicker scanning times
    • - causes blurring as MRI is a tradeoff b/w parameters
    • - blurriness is solved by keeping ETL as low as possible
    • - as more 180's - as faster T (T - blur)
    • - ETL (Turbo Factor) - Echo Train Length - # of 180 pulses after the 90 pulse
    • - fills 2 K-Space per TR
    • - best for Pt w metal
  14. Product of FID
    T2* SE Sequence
  15. FID
    Free Induction Decay due to induction current (Eddy Current)
  16. Good for Nerve roots
    T2* SE Sequence
  17. When FID reach X-Y plan, becomes ...
    T2* SE Sequence
  18. T2* SE Sequence
    • - product of FID
    • - when FID reach X-Y plan, becomes - T2*
    • FID - Free Induction Decay due to induction current (Eddy Current)
    •     - caused by dephasizing P and MF inhomogeneities  
    •     - occur before T1 and T2 (leakage current)
    •     - decays along transverse plan X-Y
    • Good for: Nerve roots
  19. Regrowth Process
    T1 SE Sequence
  20. Longitudinal Magnetization has returned to 63% of its final value (37% loss)
    T1 SE Sequence
  21. SE Sequence - TR↧-TE↧ (numbers)
    • T1 SE Sequence
    • 800 TR - 30 TE (Max)
  22. TR primarily controls the contrast
    T1 SE Sequence
  23. NMV in longitudinal (Z) direction
    T1 SE Sequence
  24. spin-lattice relaxation
    T1 SE Sequence
  25. Energy given to surrounding tissue
    T1 SE Sequence
  26. Shows anatomy (bone)
    T1 SE Sequence
  27. Fat is bright
    T1 SE Sequence
  28. Longer at higher field strengths
    T1 SE Sequence
  29. T1 SE Sequence
  30. T1 SE Sequence
       - ... Process
       - term
       - TR-TE (numbers)
       - ? controls contrast
       - NMV in...
       - ?-?
       - energy ...
       - shows ...
       - ... is bright
       - ... field strength
    • - Regrowth Process
    • - Longitudinal Magnetization has returned to 63% of its final value (37% loss)
    • - TR↧-TE↧
    •    800 TR - 30 TE (Max)
    • - TR primarily controls the contrast
    • - NMV in longitudinal (Z) direction
    • - spin-lattice relaxation
    • - energy given to surrounding tissue
    • - shows anatomy (bone)
    • - fat is bright
    • - longer at higher field strengths
  31. Decaying Process
    T2 SE Sequence
  32. Transverse Magnetization decay to 37% of its original value (63% loss)
    T2 SE Sequence
  33. SE Sequence - TR↥-TE↥ (numbers)
    • T2 SE Sequence
    • 3000 TR - 65 TE (and up)
  34. TE primarily controls the contrast
    Higher TE:
    • T2 SE Sequence
    •  - Higher TE:
    •       - T2-Weighted image
    •       - CSF bright (hypertense)
  35. NMV in transverse (X-Y) plane
    T2 SE Sequence
  36. Spin-spin interaction
    T2 SE Sequence
  37. Energy is exchanged to surrounding lattice
    T2 SE Sequence
  38. Shows pathology (fluid)
    T2 SE Sequence
  39. Fluid is bright
    T2 SE Sequence
  40. Unrelated to field strength
    T2 SE Sequence
  41. T2 SE Sequence
  42. T2 SE Sequence
       - ... Process
       - term
       - TR-TE (numbers)
       - ? controls contrast
       - NMV
       - ?-?
       - energy ...
       - shows ...
       - ... is bright
       - ... field strength
    • - Decaying Process
    • - Transverse Magnetization decay to 37% of its original value (63% loss)
    • - TR↥-TE↥
    •    3000 TR - 65 TE (and up)
    • - TE primarily controls the contrast
    • - NMV in transverse (X-Y) plane
    • - spin-spin interaction
    • - energy is exchanged to surrounding lattice
    • - shows pathology (fluid)
    • - fluid is bright
    • - unrelated to field strength
  43. Nyquist Theorem
    • Every sample can be sampled twice by applying 2 TE's
    • Weighted Images
    • Used in Fast spin echo
  44. Weighted Images Contraindication
    claustrophobic Pt (TE once)
  45. Weighted Images
  46. Weighted Images
    • Used in Fast spin echo
    • Nyquist Theorem: every sample can be sampled twice by applying 2 TE's
    • - Example:
    •             TR     TE  
    •    T2    3000     65  
    •    T2w  3000     62   30
    • - if T2 gives 20 slices, T2w gives 40 slices
    • - images are obtained with a different contrast
    • - typically obtained simultaneously PD- and T2-weighted images
    • Contraindication: claustrophobic Pt (TE once)
  47. Intermediate Pulse Sequence (grayer in appearance b/c 15% tissue differentiation)
    Proton Density - PD SE Sequence
  48. TR↥-TE↧ (numbers)
    • Proton Density - PD SE Sequence
    • 850-2300 TR - 30 TE Max
  49. spin-density
    Proton Density - PD SE Sequence
  50. Brightest signal in MRI
    Proton Density - PD SE Sequence
  51. Shows pathology and anatomy
    Proton Density - PD SE Sequence
  52. Good and best for Multiple Sclerosis
    • Proton Density - PD SE Sequence
    • FLAIR sequences - best
  53. PD SE Sequence
      - PD ?
      - another name
      - TR-TE (numbers)
      - ?-?
      - shows...
      - good for...
    • - Proton Density
    • - Intermediate Pulse Sequence (grayer in appearance b/c 15% tissue differentiation)
    • - TR↥-TE↧
    •   850-2300 TR - 30 TE Max
    • - spin-density
    • - shows anatomy (black) and pathology (white)
    • - Good for Multiple Sclerosis
    • - brightest signal in MRI
  54. Best use in conjunction w FAT-SAT
    PDw - Proton Density weighted
  55. PDw
    • - Proton Density weighted
    • - best use in conjunction w FAT-SAT
  56. Start w 180 followed by 90
    IR - Inversion Recovery Sequence
  57. TI controls contrast
    IR - Inversion Recovery Sequence
  58. Bone black - if white - pathology
    IR - Inversion Recovery Sequence
  59. To suppress fluid by inversion-recovery
    FLAIR
  60. To suppress fat by short TI - ?
    • STIR
    • TI = 140
  61. IR Sequence
    • Inversion Recovery
    • start w 180 followed by 90
    • 180° RF inversion wave
    •   -  flips longitudinal magnetization Mz in the opposite direction (negative)
    • 90° RF excitation wave
    •   - to obtain transverse magnetization
    • TI - Time to invert (delay between 180° and 90°)
    • TI controls contrast
    • Bone black - if white - pathology
    •     2 types of IR:
    • 1) FLAIR - Fluid Attenuated IR
    •   -  to suppress fluid by inversion-recovery
    • 2) STIR - Short TAU IR
    •   -  to suppress fat by short TI - 140
  62. The Flip Angle (FP) < 90°
    Gradient GRE Echo
  63. The absence of a 180° RF rephasing pulse
    • Gradient GRE Echo
    • GRE instead 180o
  64. NOT good for Pt w metal
    Gradient GRE Echo
  65. Gradient GRE Echo
  66. Gradient GRE Echo
    • - the Flip Angle (FP) < 90°
    • - the absence of a 180° RF rephasing pulse (GRE instead)
    • - MRA - Angiography
    • - Blood is bright
    • - NOT good for Pt w metal
  67. FA↥ (numbers)
    • T1 GRE
    • FA↥ = 45o-89o
  68. FA controls contrast
    • T1 GRE
    • T2 GRE
  69. FA↧ (numbres)
    • T2 GRE
    • FA↧ = 5o-25o (<90)
  70. T1 GRE
    • - T1 Grade and Echo
    • - TR­­↧-TE↧
    •    800 TR - 30 TE Max
    • - FA↥ = 45o-89o (<90)
    • - FA controls contrast
    • - MRA - Angiography
    • - Blood is bright
    • - NOT good for Pt w metal
  71. T2 GRE
    • - T2 Grade and Echo
    • TR↥-TE↥ 
    •    3000 TR - 65 TE and up
    • - FA↧ = 5o-25o (<90)
    • - FA controls contrast
    • - MRA - Angiography
    • - Blood is bright
    • - NOT good for Pt w metal
  72. TR↥-TE↥-TI↥
    FLAIR - Fluid Attenuated IR Sequences
  73. Sequence effect white matter only
    FLAIR - Fluid Attenuated IR Sequences
  74. Best for multiple sclerosis
    FLAIR - Fluid Attenuated IR Sequences
  75. Good for whenever CSF flows
    FLAIR - Fluid Attenuated IR Sequences
  76. Good for brain and C-T-spine
    FLAIR - Fluid Attenuated IR Sequences
  77. FLAIR sequences
      - to... 
      - TR-TE-TI - ⇅
      - effect...
      - good for
    • Fluid Attenuated IR 
    • - to suppress fluid by inversion-recovery
    •   - TR↥-TE↥-TI↥
    •   - effect white matter only
    • Good for:
    •   - best for multiple sclerosis   
    •   - whenever CSF flow (in brain and C-T-spine)
  78. TR↧-TE↧-TI↧
    STIR - Short TAU IR Sequence
  79. TAU
    The interpulse times (time between the 90° and 180° pulse, and between the 180° pulse and the echo) in STIR
  80. Best for Osteomyelitis
    STIR - Short TAU IR Sequence
  81. Good For Brest imaging
    STIR - Short TAU IR Sequence
  82. Good For Orbits
    STIR - Short TAU IR Sequence
  83. STIR
      - to...
      - TR-TE-TI -
      -
    good for
    • Short TAU IR 
    •   - to suppress fat by short TI - 140
    •   - TR↧-TE↧-TI↧
    •   - TAU - The interpulse times (time between the 90° and 180° pulse, and between the 180° pulse and the echo)
    •   - TI=TAU+TAU
    •   - Good For:
    •   1) Osteomyelitis
    •   2) Brest imaging
    •   3) Orbits
  84. Measuring the random motion of water molecules within a voxel of tissue
    Diffusion
  85. Uses B (blood) value of 1000 ←↨→
    DIFF - Diffusion GRE PS
  86. Good for infarct ONLY
    DIFF - Diffusion GRE PS
  87. Good for Hemi-Paresis
    DIFF - Diffusion GRE PS
  88. What makes Diff Diff?
    B-value 1000
  89. DIFF GRE PS
    • Diffusion GRE Pulse Sequence
    •   - measuring the random motion (freedom of movement) of water molecules within a voxel of tissue
    •   - uses B (blood) value of 1000 ←↨→
    •   - Good for: infarct ONLY (Hemi-Paresis)
    • QT: What makes Diff Diff? B-value 1000
  90. Loudest Sequence
    • EPi - Echo Planar Imaging
    • b/c more gradient stress
  91. Fastest sequence
    • EPi - Echo Planar Imaging
    • b/c Half Fourier Technique
  92. Good for stroke ONLY
    • EPi - Echo Planar Imaging
    • visualize infraction - dead blood
  93. T2*W
    • T2* weighting
    • single RF excitation pulse, with no preparation
    • Gradient Echo EPI
  94. GE-EPI
    • Gradient Echo EPI
    • single RF excitation pulse, with no preparation
    • T2* weighting
  95. T2W
    • T2 weighting
    • pair of 90° - 180° pulses (spin echo type)
    • Spin Echo EPI
  96. SE-EPI
    • Spin Echo EPI
    • pair of 90° - 180° pulses (spin echo type)
    • T2 weighting
  97. T1W
    • T1 weighting
    • 180° inversion pulse to prepare magnetization then RF excitation pulse
    • Inversion Recovery EPI
  98. IR-EPI
    • Inversion Recovery EPI
    • 180° inversion pulse to prepare magnetization then RF excitation pulse
    • T1 weighting
  99. DW-EPI
    preparatory pattern for diffusion weighting
  100. EPi
    • Echo Planar Imaging
    • - loudest b/c more gradient stress
    • - fastest b/c Half Fourier Technique  (100 ms / slice)
    • - limited spatial resolution
    • - Good for: stroke ONLY (visualize infraction - dead blood)
    • GE-EPI: single RF excitation pulse, with no preparation - T2* weighting
    • SE-EPI: pair of 90° - 180° pulses (spin echo type) - T2 weighting
    • IR-EPI: 180° inversion pulse to prepare magnetization then RF excitation pulse - T1 weighting
    • DW-EPI: preparatory pattern for diffusion weighting
  101. Main purpose of Calibration Scans
    reduce scan time
  102. Parallel Imaging
    • illuminate motion what is not parallel
    • used in Calibration Scans
  103. Asset
    • First quick scan, straight the lines and scan (can be used all the time)
    • Used in Calibration Scans
  104. NOT for redoing
    Calibration Scans
  105. Calibration Scans
    • Main purpose - reduce scan time
    • Parallel Imaging - illuminate motion what is not parallel.
    • Asset - first quick scan, straight the lines and scan (can be used all the time)
    • NOT for redoing
  106. Fat Suppression
    • - suppressing all signals from fat
    • - applied by SE PS
  107. SSFP
    • Steady-state free precession is a type of gradient echo MRI pulse sequence in which transverse magnetization (Mxy) is maintained between successive cycles
    • Used in FIESTA
  108. Best imaging you can do - one of the time
    FIESTA
  109. T2: TR↥-TE↥, FA↧ 5-25o
    FIESTA
  110. T1: TR↧-TE↧, FA↥ 89o
    FIESTA
  111. TR-TE-FA lower than normally used
    FIESTA
  112. FIESTA
    • Fast Imaging Employing Steady-state Acquisition
    • - is a name for a balanced steady-state gradient echo sequence
    • - SSFP - Steady-state free precession is a type of gradient echo MRI pulse sequence in which transverse magnetization (Mxy) is maintained between successive cycles
    • - TR-TE-FA lower than normally used
    • - T1: TR↧-TE↧, FA↥ 89o
    • - T2: TR↥-TE↥, FA↧ 5-25
    • - best imaging you can do - one of the time
  113. ♢ - ONLY for chest (↥ contrast)
    EFF - Effective TE
  114. Middle value of the center of the a K-space
    EFF - Effective TE
  115. EFF TE
    • Effective TE
    • middle value of the center of a K-space
    • the echoes corresponding to the central k-space lines
    • controls contrast
    • ♢ - ONLY for chest (↥ contrast)
  116. MRI Contrast (definition)
    - diagnostic agent w Pharmacokinetics Properties
  117. MRI Contrast (PP-property)
    • Pharmacokinetics Properties:
    • 1) Absorption - how well it absorbed in lesions, vessels, organs
    • 2) Duration - 3-6 hours
    • 3) Excretion - by kidneys
  118. MRI Contrast (used for)
    • 1) To see BBB
    • 2) Spinal operations - to see diff b/f scar tissue and disk space
    •    - start scan within 20 min
    •    - scar absorbs immediately
    •    - disk absorbs longer
    •    - to long - can see only disk
    • 3) Endocrine disorders
    • 4) All MRA studies
  119. MRI Contrast (contr/prec)
    • Contraindication - no known to date
    • Precautions:
    • 1) Multiple Myeloma
    •    - cancer that forms in a type of white blood cell called a plasma cell
    •    - blood thick, w contrast even thicker (worm)
    • 2) Past history of allergic reaction
    • 3) Abnormal GFR (Glomerulus Filtration Rate)
    •    - > 60 mg/dL - normal
    •    - 30-60 mg/dL - can be w contrast, but immediately to dialysis
    •    - < 20 mg/dL - Renal Failure - NO MRI
  120. Osmolarity
    # of particles in the solution (cannot be changed)
  121. Viscosity
    thickens (can be changed by warming)
  122. MRI Contrast (properties)
    • 1) Viscosity - thickens (can be changed by warming)
    • 2) Osmolarity - # of particles in the solution (cannot be changed)
  123. MRI Contrast (side effects)
    • 1) Headache - 98% - most common
    • 2) Nausea/Vomiting - 1-5%
  124. MRI Contrast (made off)
    • 7 unpaired electrons
    • composed of Chelate Ligand
    • do not bind to plasma
    • lites the protein - tumor, lesion
    • non-ionic b/c Ligand neutralize acidity in ions
  125. Oldest and thickest contrast
    Magnevist
  126. Most expensive contrast
    Magnevist
  127. Contrast which is best Macrocylic - compose lesion completely - all others just linear
    Magnevist
  128. Magnevist
    • MRI Contrast
    • oldest and thickest
    • most expensive
    • best Macrocylic - compose lesion completely - all others just linear
  129. Universal contrast
    Gadavist
  130. Gadavist
    • MRI Contrast
    • universal
    • cheaper
  131. Contrast for liver specifically
    Evolist
  132. T1 and T2 (all other MRI w contrast only T1)
    Contrast study for liver using Evolist
  133. Evolist
    • MRI Contrast
    • for liver specifically
    • b/c liver has dual blood supply (80% portal veins - 20% hepatic arteries) wait 20 min
    • T1 and T2 (all other MRI w contrast only T1)
  134. Contrast NOT good for children
    Optimark
  135. Optimark
    • inexpensive
    • NOT good for children
  136. Omnisean
    Prohance
    • less expen
    • thinner
  137. MRI contrast lethal dose
    • 10-20 mmol/kg
    •    - irritability
    •    - severe tremor
  138. MRI Contrast (amount)
    • depends on weight of Pt
    • 0.1 mmol/kg
    • 0.2 ml/kg
    • Lethal dose: 10-20 mmol/kg
    •    - irritability
    •    - severe tremor

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