Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Neurology advanced asl jy gauvrit

1,071 views

Published on

Published in: Health & Medicine, Technology

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  

×