Diffusion by pengxuebo

VIEWS: 7 PAGES: 16

									       Navigated Steady-State
Diffusion Imaging of Knee Cartilage

   Karla L. Miller, Garry E. Gold† and John M. Pauly

           Department of Electrical Engineering
  †Department of Radiology and Palo Alto VA Medical Center


  Magnetic Resonance Systems Research Laboratory
                Stanford University
DWI of cartilage
• in vitro studies
                 Burstein 1993, Henkelman 1994, Xia 1994,
                    Torzilli 1998, Frank 1999, Knauss 1999
• in vivo studies
                                 Gold 1998, Eustace 2000


• evidence for correlation to damage
                                     Xia 1995, Frank 1999
DWI of cartilage: challenges
• large gradient area

• small motions cause severe artifacts

• short T2 necessitates short TE
Navigated Steady-State DWI
• large gradient area
       strong diffusion weighting per unit area
• small motions cause severe artifacts
       navigated motion correction
• short T2 necessitates short TE
       short TE, TR
Outline
• Navigated SS-DWI
• In Vivo Results
• Discussion
Diffusion weighted imaging
       (1)       (2)
90°
                                     ACQ


                               (3)

         (1) encode position
         (2) spins diffuse
         (3) decode position
SS-DWI diffusion sensitivity

                          

                 …
SS-DWI diffusion sensitivity

                           

                 …
      90º                 90º
                 …
SS-DWI diffusion sensitivity

                                      

                   …

                   …

                 D = nTR

                           n=1,2,3 …
Steady-state diffusion
                         TR < T1,T2
Navigated steady-state diffusion
                          TR < T1,T2
Navigated phase correction

                        kx                kx




              ky                   ky
      high resolution         navigator

 • navigator measures motion-induced phase
 • phase-correct high resolution data
                                   (Poster #1112)
In vivo experiments
•   5 subjects
•   FOV = 18 cm, 0.75 x 0.75 mm2, 5 mm thick
•   TR = 25 ms, = 25, nex = 64
•   G = {1, 2.75, 4} G/cm, t = 5 ms


             beff = 40, 275, 500 s/mm2
              imaging time: 7 minutes
In vivo results




 40 s/mm2    275 s/mm2   500 s/mm2
Navigator correction




                    navigator
      uncorrected   corrected
Conclusions
• diffusion has potential as contrast
  mechanism in cartilage
• SS-DWI enables in vivo knee cartilage
  diffusion imaging
• navigated motion-correction allows high
  resolution

								
To top