Gradient echo法の基礎 - kanamri.umin.ne.jp

1 Gradient echo Kitasato University HospitalGRE Kitasato University Hospital GRE GRE Kitasato University HospitalGRE T2* inflow effect TR,TE Kitasato University Hospital GsGpGread GRE PSD(Pulse Sequencediagram)TRTERFFID FID Kitasato University Hospital90 GsGpGread90 SE PSD TRTERF180 MRI GRE PSD SE PSD 180 FID Kitasato University Hospital TR : repetition time T1 TR 100ms TR 50msTE : echo time T2 TE15 25ms TE5 10msFA : flip angle FA70 110 FA5 20 GRE TR TE FA MRI Catherine Westbrock Kitasato University HospitalTR TE FA GRE (FA= )SGRE =1-exp(-TR/T1) exp(-TE/T2*)K f(v) sin 1-cos exp(-TR/T1) M0 Mxy=M0 sin Mz=M0 cos T1 T2* T1 Mz Mxy sin K f(v) Kitasato University HospitalTR TE FA FA ( 90 )SGRE =1-exp(-TR/T1) exp(-TE/T2*) sin 1-cos exp(-TR/T1)cos 0 sin 1 SE T2 T2* SSE =K f(v) 1-exp(-TR/T1) exp(-TE/T2)TR TE T2* TR TE T1 TR TE FA ( 90 )GRE (FA=90 )SGRE =K f(v) 1-exp(-TR/T1) exp(-TE/T2*)TR TE FA Kitasato University HospitalK f(v)

2 Kitasato University HospitalTR TE FA FA ( 20 )SGRE =1-exp(-TR/T1) exp(-TE/T2*) sin 1-cos exp(-TR/T1)cos 1 TE T2* TE Kitasato University Hospital ? TR TR RF 90 RF Mzt90 RF Kitasato University Hospital FA RF ( : FA30 )Mzt30 RF RF ? TR T1 FA Kitasato University HospitalErnst( ) ex)Gd RF FA T1 TR cos =exp(-TR/T1) Ernst (TR:100ms) University Hospital ? TR MxyRF RF FID GRE PSD Kitasato University HospitalTR MxyRF RF : HE(Hahn echo): STE(Stimulated echo) TR FID HE STE steady state free precession:SSFP ?

3 Kitasato University Hospital Spoiled GRE(incoherent GRE) Coherent GRE Gradient spoiling RF spoiling SSFP-FID SSFP-SE SSFP balanced SSFP ex)FLASH ex)SPGR ex)FISP, GRASS, FFEK itasato University HospitalSpoiled GRE ( Gradient spoiling) GsGpGread TRTERFFLASH band RewinderMRI Kitasato University HospitalSpoiled GRE (RF spoiling) GsGpGread TRTERFFLASH band RF RewinderMRI Kitasato University HospitalCoherent GRE SSFP-FID GsGpGread TRTERFFLASH band FID HE,STE RewinderMRI Kitasato University Hospital GRE GRE Kitasato University HospitalTR TE FA TR40ms5ms20msTEaba FA20 b FA90 GRASS(Coherent GRE SSFP-FID)100 500msKitasato University HospitalTR TE FA TR40ms500ms5ms20msTEaba FA20 b FA90 100 SPGR(Spoiled GRE.

4 RF spoiling)Kitasato University HospitalSPGR vs GRASSFA 20 ,TE 20ms 40ms100 500msTRSPGRGRASST2* TR SPGR GRASS Kitasato University HospitalSPGR vs GRASSFA 90 ,TE 5ms 40ms100 500msTRSPGRGRASST1 GRASS SPGR Kitasato University Hospital GRE GRE ( )Kitasato University Hospitalin phase , opposed phase ( 220Hz) 1/220Hz = phase opposed phase Kitasato University Hospitalin phase , opposed phase withGRASS GRASS : TR 500ms , FA 30 opposed phase T2* in phase TE TE= , in phase MRI Kitasato University Hospitalfast Spoiled GRE(fast SPGR) ex) Dyanamic study(LAVA : GE ) 3D fast SPGR TR(5ms ) FA(15 ) 3D Parallel imaging PreEarly(late A)PortalDelay Kitasato University HospitalTime of flight(TOF) (In flow effect)TRTRTRTR MzRF t3D Vasc TOF SPGR : TR TR.

5 TR (v)= (d)/TRKitasato University HospitalMulti echo GRE (MERGE) TE TE GRASSMERGEGRASS S/N T2* TE 12345020406080100 SNR(phantom)GRASSMERGE Kitasato University Hospital (SWI) 3D GRE (T2* ) SWIGRASSSWAN(GE )Akira Kunimatsu et Reson Med Sci,vol 11,No 3,205-211(2012)Kitasato University Hospital GRE TR TE FA .. GRE