Neurology advanced asl jy gauvrit

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Neurology advanced asl jy gauvrit

  1. 1. ARTERIAL  SPIN  LABELING   Jean-­‐Yves  Gauvrit,  Jean-­‐Christophe  Ferré     University  hospital  of  Rennes,  Department  of  radiology  and  medical   imaging   Unit/Project  VisAGeS  U746  INRIA/INSERM,  IRISA,  UMR  CNRS  6074   Plateforme  Neurinfo  
  2. 2. IntroducNon   2   IntroducNon   •  Arterial  Spin  Labeling  (ASL)   •  MRI  technique  for  assessing  cerebral  blood  flow  (Detre  et  al.  MRM   1992)     •  Non-­‐invasive   •  Non-­‐irradiaNng   •  No  exogenous  contrast  agent  injecNon   •  Quan8ta8ve     •  Cerebral  blood  flow  (CBS)   •  Reliable  and  reproducible   •  Main  disadvantage:  low  signal-­‐to-­‐noise  ra8o  (SNR)   •  Sequences  available  on  MRI  but  confidenNal  use  
  3. 3. IntroducNon   ASL  principles   •  Image  acquisiNon   1.  Arterial  spin  labeling  by  a  RF  pulse   2.  Inversion  Nme  TI:  Nme  needed  for  labeled  spins  to  reach  the  volume  of  interest   3.  AcquisiNon  of  the  volume  of  interest   A  second  acquisiNon  of  the  volume  of  interest  is  then  carried  out  without  labeling   3  
  4. 4. 4   IntroducNon   ASL  principles   •  Data  processing  and  quanNficaNon   QuanNficaNon  model   ↓ -­‐   Control  image   →   =   Tag  image   Perfusion  image   Cerebral  blood   flow  (CBF)  map  
  5. 5. IntroducNon   ASL  principles   •  ASL  is  a  reliable  technique  for  measuring  CBF   •  ASL  is  a  reproducible  technique  for  measuring  CBF   5  
  6. 6. IntroducNon   ASL  principles   AcquisiNon   • ASL  labeling   • Slice   acquisiNon   • MRI  hardware     6  
  7. 7. IntroducNon   ASL  principles   AcquisiNon   Processing   • ASL  labeling   • Slice   acquisiNon   • MRI  hardware   • Preprocessing   • CBF   quanNficaNon   7  
  8. 8. 8   IntroducNon   ASL  principles   AcquisiNon   Processing   • ASL  labeling   • Slice   acquisiNon   • MRI  hardware   • Preprocessing   • CBF   quanNficaNon   ApplicaNons   • ArNfacts   • Neuro   • Others  
  9. 9. IntroducNon   ASL  principles   AcquisiNon   • ASL  labeling   • Slice   acquisiNon   • MRI  hardware     9  
  10. 10. AcquisiNon   10   ConNnuous  ASL  (CASL)   •  Historical  method   •  ConNnuous  (2-­‐4s)  and  selecNve  labeling   of  protons  going  through  a  tagging  plane   with  an  equilibrium  state   •  Advantages   •  High    SNR   •  Reliable  CBF  quanNficaNon   •  But   •  High  SAR  and  magne8za8on  transfer  effects   (especially  at  3T)   •  Hardware  limitaNon  (no  mulN-­‐channel  coil)   Detre  et  al.  Magn  Reson  Med  1992  
  11. 11. AcquisiNon   Pulsed  ASL  (PASL)   •  Wide  but  short  RF  pulses     •  Upstream  of  the  region  of  interest  (box):    STAR,  QUIPPS,  Q2TIPS   •  Over  the  whole  region  of  interest:  FAIR   •  Advantages   •  Easy  implementaNon   •  MulN-­‐channel  coil   •  Parallel  imaging  possible   •  MulN-­‐TI  possible  (QUASAR:  arterial  transit  Nme)   •  SelecNve  vascular  labeling  possible   •  But   •  Arterial  transit  effects   •  Lower  SNR   Edelman  et  al.  Radiology  1994   Wong  et  al.  Magn  Reson  Med  1998   Petersen  et  al.  Magn  Reson  Med  2006   11  
  12. 12. AcquisiNon   Pseudo-­‐conNnuous  ASL  (pcASL)   •  “Hybrid”  method   •  MulNple  short  RF  over  an  extended   period   •  Advantages   •  High  SNR   •  Reproducibility  +++   •  Easy  implementaNon   •  But   •  No  ArterialTransitTime  determinaNon     Wu  et  al.  Magn  Reson  Med  2007   12  
  13. 13. AcquisiNon   ASL  principles   AcquisiNon   • ASL  labeling   • Slice   acquisiNon   • MRI  hardware     13  
  14. 14. AcquisiNon   14   Image  acquisiNon   •  Context:  low  SNR   Increase  the  number  of  acquisiNons  (labeled-­‐unlabeled  image   pairs)  but  increase  in  the  acquisiNon  Nme   -­‐>  “Clinical  ”  compromise  30  acquisiNons  (~  3min30)   •  2D  SS  EPI:  most  commonly  used  method   •  SaNsfactory  SNR  and  fast  acquisiNon   •  But  distorNons   •  3D  segmented  SE-­‐EG  (i.e.:  3D  GRASE)   •  Bemer  SNR,  less  distorNons  ,  and  bemer  coverage   •  With  suppression  of  the  staNc  Nssue  signal  (background   suppression)  
  15. 15. AcquisiNon   ASL  principles   AcquisiNon   • ASL  labeling   • Slice   acquisiNon   • MRI  hardware     15  
  16. 16. AcquisiNon   16   ASL:  low  SNR   •  Increase  the  magneNc  field   •  Intrinsic  increase  in  SNR   •  Bemer  suppression  of  surrounding  Nssue   •  Increase  in  the  labeling  duraNon  (by  lengthening  of  the  longitudinal   relaxaNon)   •  T1  blood:  1,5T  -­‐>1350  ms    3T-­‐>  1650ms   Wang  et  al.  Magn  Reson  Med  2002  
  17. 17. AcquisiNon   17   ASL:  low  SNR   •  Use  of  mulN-­‐channel  coils     •  Possible  with  PASL  and  pCASL   •  12  channels-­‐>  32  channels:  SNR  +39%   •  Parallel  imaging  possible   Ferré  et  al.  JMRI  2012  
  18. 18. Image  processing   ASL  principles   AcquisiNon   Processing  of   images   • Marquage  ASL   • AcquisiNon   des  coupes   • Matériel  IRM   • Preprocessing   • QuanNficaNon     18  
  19. 19. 19   Image  processing   Processing  of  ASL  images   CorrecNon  of   movements   SubtracNon   QuanNficaNon   Perfusion   image   ASL  images   Denoising   CBF   pvc-­‐CBF   RegistraNon  on  T1   CorrecNon  of  parNal   volume  effects  
  20. 20. 20   Image  processing   Processing  of  ASL  images   CorrecNon  of   movements   SubtracNon   QuanNficaNon   Perfusion   image   ASL  images   Denoising   CBF   pvc-­‐CBF   RegistraNon  on   T1   CorrecNon  of  parNal   volume  effects  
  21. 21. 21   ApplicaNons   ASL  principles   AcquisiNon   Processing   • ASL  labeling   • Slice   acquisiNon   • MRI  hardware   • Preprocessing   • CBF   quanNficaNon   ApplicaNons   • ArNfacts   • Neuro   • Others  
  22. 22. ApplicaNons   22   ASL  arNfacts     ASL-­‐specific  ar8facts   •  Vascular  arMfacts   •  PASL>CASL   •  Arterial  or  venous   •  Labeled  blood  in  the  vessels   •  Arteries:  related  to  arterial  transit  Nmes   TI  1200                        TI  1700     •  ReducNon  by  use  of  “crushers”     Without                        Crushers  
  23. 23. ApplicaNons   23   ASL  arNfacts     ASL-­‐specific  ar8facts   •  Vascular  arMfacts   •  Loss  of  signal  in  the  upper  slices   •  Related  to  the  relaxaNon  of  labeled  protons   •  Caudo-­‐cranial  2D,  especially  at  1.5T,  reduced  labeling  Nme   •  Parallel  imaging:  decrease  the  acquisiNon  Nme  of  slices  and  thus  the  Nme   between  slices  (Wang  et  al.  MRM  2005)     Deibler  et  al.  AJNR  2008  
  24. 24. ApplicaNons   ASL  arNfacts       ASL-­‐specific  ar8facts   •  Vascular  arMfacts   •  Loss  of  signal  in  the  upper  slices   •  Physiological  hyperperfusion  /  hypoperfusion   Physiological  changes  in  perfusion,  parNcularly  visible  with  PASL   •  Hyperperfusion  areas  (Mamo  et  al.  Arch  Neurol  1983)   •  Hypoperfusion  areas  (Hendrikse  et  al.  Radiology  2008):  related  to  aTT       24  
  25. 25. 25   ApplicaNons   ASL  arNfacts       Non-­‐specific  ar8facts   •  Movement  arMfacts   •  MagneMc  suscepMbility  arMfacts   •  Related  to  SS-­‐EG-­‐EPI  acquisiNon   •  Focal  “hypoperfusion”   •  Decreased  by  non  EPI  imaging  and  parallel  imaging  (decrease  of  TE)       Without  parallel  imaging                with  GRAPPA  2 Ferré  et  al.  JMRI  2012  
  26. 26. 26   ApplicaNons   ApplicaNons  of  ASL   •  Cerebral  perfusion  assessment   •  Research  –  Neurosciences   •  Psychiatric  disease   •  Depression  (Duhameau  et  al.  Psychiatry  Research  2010)     •  Neurovascular  disease   •  In  acute  phase  (Wang  et  al.  Stroke  2012)   •  In  chronic  phase   MTT TTM                ASL                  ASL   rCBV   rCBV (DSC)        ASL             ASL
  27. 27. 27   ApplicaNons   ApplicaNons  of  ASL   •  Tumor   •  Tumor  characterizaNon  (Wolf  et  al.  JMRI  2005)   •  Post-­‐treatment  follow-­‐up  (Weber  et  al.  Invest  Radiol  2004)   rCBV      A rCBV  (DSC)          A  SL SL         rCBV   rCBV (DSC)        ASL             ASL
  28. 28. 28   ApplicaNons   ApplicaNons  of  ASL   •  Cerebral  perfusion  assessment   •  Demen8a   FDG  PET                      ASL   •  Value  +++   •  Reveals  hypoperfusion  in  AD,  FTD…    (Du  et  al.  Neurology  2006,  Hu  et  al.  Neurology  2010)   Esquevin  et    al.  JFR  2012   •  European  COST  AcNon  Arterial  Spin  Labeling  in  DemenMa   •  X  Golay  UCL  -­‐  15  countries   •  ObjecNves   •  Standardizing  and  comparing  ASL  techniques   •  Developing  image  processing  sovware   •  ValidaNng  ASL  as  biomarker  of  the  disease  and  its  progression  
  29. 29. ApplicaNons   ApplicaNons  of  ASL   •  ASL  and  funcNonal  MRI  acNvaNon     •  ASL  allows  neural  acNvaNon  mapping  (ASLf)   •  Motor,  somestheNc,  speech  funcNons…   •  ASLf  vs  IRMf  BOLD,  seems  (Raoult  et  al.  Neuroimage  2011)   •  +  inter  and  intra  individually  reproducible   •  +  spaNally  specific   •  Bemer  Nme  resoluNon   •  Clinical  applicaNon  not  validated  yet   29  
  30. 30. 30   ApplicaNons   ApplicaNons  of  ASL   •  Extra-­‐cerebral  applicaNons   •  Renal  perfusion   •  Mainly  FAIR  techniques   Lanzmann  et  al.  Radiology  2012   •  Measurements  correlated  with  PET    (even  with  renal  artery  stenosis)   •  Good  intra-­‐  and  inter-­‐session  reproducibility   •  Renal  tumor  characterizaNon  (de  Bazelaire  et  al.  Acad  Radiol  2005;  Lanzmann  et  al.   Radiology  2012)   •  In  experimental  condiNons,  perfusion  of   •  Diseased  bone   •  Pancreas   •  Uterus  and  placenta   •  Prostate  
  31. 31. 31   Main  advantages  and  disadvantages  of  ASL   Advantages   -­‐  No  irradiaNon   Disadvantages   -­‐  Low  signal-­‐to-­‐noise  raNo:   -­‐  No  exogenous  contrast  agent  injecNon   Minimal  acquisiNon  Nme  of  3  min   -­‐  Absolute  quanNficaNon  of  Nssue  blood  flow   Limited  spaNal  resoluNon   and  Nssue  transit  Nme  possible   -­‐  QuanNficaNon  of  Nssue  blood  volume   -­‐  Repeated  measurements  possible   impossible  (i.e.:  cerebral  blood  volume)   -­‐  Reproducibility   -­‐  No  standardizaNon  of  techniques  (type  of       labeling,  image  acquisiNon,  post-­‐processing)       among  manufacturers   -­‐  OpNmizaNon,  automaNon  and  standardizaNon   of  post-­‐processing  are  sNll  being  developed  
  32. 32. 32   Remember   •  ASL:  MRI  method  for  perfusion  assessment     •  Non-­‐irradiaNng   •  No  exogenous  contrast  agent   •  QuanNtaNve  and  reproducible   •  Numerous  techniques,  characterized  by   •  Labeling  type  (PASL  or  pcASL)   •  Image  acquisiNon  mode  (2D  or  3D  /  EPI…)   •  Image  processing:  important  step   •  There  are  ASL-­‐specific  ar8facts   •  Close  to  clinical  use  

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