「EPIシーケンスにおける歪み ... - nagano-mri.com

1 nagano Municipal HospitalDepartment of RadiologyNagano Municipal Hospital EPI ( ) MR II nagano Municipal HospitalDepartment of RadiologyNagano Municipal HospitalSingle shot SE-EPI diffusion SliceReadMPGEchoWrapSingle Shot SE-EPI DiffusionRF nagano Municipal HospitalDepartment of RadiologyNagano Municipal EPI Gradient Waveform of the EPI moduleEcho SpaceEReadoutCDABBlipEcho nagano Municipal HospitalDepartment of RadiologyNagano Municipal HospitalDABCEk-space trajectoryEReadoutCDABBlip nagano Municipal HospitalDepartment of

2 RadiologyNagano Municipal HospitalA1magnitude imageA2 A1k-space trajectoryA2 Spine Echo nagano Municipal HospitalDepartment of RadiologyNagano Municipal Hospitalmagnitude image Spine Echo nagano Municipal HospitalDepartment of RadiologyNagano Municipal Hospital A1B1k-space trajectoryA2B2A1A2B1B2 EPI nagano Municipal HospitalDepartment of RadiologyNagano Municipal Hospitalmagnitude image EPI nagano Municipal HospitalDepartment of RadiologyNagano Municipal Hospital A1B1k-space trajectoryA2B2A1A2B1B2 EPI nagano Municipal HospitalDepartment of RadiologyNagano Municipal Hospitalmagnitude image EPI nagano Municipal HospitalDepartment of RadiologyNagano Municipal EPI k-space a) Full scan, Half scan, Rectangular Pixel b) Parallel imaging, Multi Shots, Rectangular FOVDABCEA B k-space trajectory Parallel imaging (Reduction factor) Multi Shots Rectangular FOV (Phase FOV) Full scan Half scan (Fractional NEX)

3 Rectangular Pixel ab nagano Municipal HospitalDepartment of RadiologyNagano Municipal HospitalDABCEA B k-space trajectory Parallel imaging (Reduction factor) Multi Shots Rectangular FOV (Phase FOV) Full scan Half scan (Fractional NEX) Rectangular Pixel abmagnitude image nagano Municipal HospitalDepartment of RadiologyNagano Municipal Hospital Pixel Distortion = dFB(Hz) / pBW (Hz/pixel) .. dFB: difference in frequency band pBW: phase bandwidth 1pixel pBW (Hz/pixel) = bBW rFOVRf nShotbBW: Base bandwidth 1line Rf: Reduction factor (Parallel imaging)nShot: number of Shot (EPI shot )rFOV: rectangular FOV (phase FOV).

4 BBW (Hz/pixel) = 1 / ( ESP Phase matrix ) .. ESP: Echo Space nagano Municipal HospitalDepartment of RadiologyNagano Municipal HospitalDistortion (mm) = Pixel Distortion ( FOV / Phase matrix ) .. FOV ESP Phase matrix rFOVP hase matrix Rf nShot= dFB(Hz) rFOVRf nShot= dFB(Hz) FOV ESP .. Pixel Distortion = dFB(Hz) ESP Phase matrix rFOVRf EPI distortion Reduction factor FOV ESP rFOVRf nShot nagano Municipal HospitalDepartment of RadiologyNagano Municipal magnitude image (SE-EPI)FOV 350mm ESP 688 s F128 P128 Full ScanrFOV Rf 1 Frequency BW raw data imageabchemical shift image (SE-EPI)

5 FOV 350mm ESP 688 s F128 P128 Full ScanrFOV 1 Frequency BW raw data image abRectangular FOV nagano Municipal HospitalDepartment of RadiologyNagano Municipal Hospital nagano Municipal HospitalDepartment of RadiologyNagano Municipal HospitalFOV 350mm ESP 568 s F128 P128 Half ScanrFOV Rf 1 Frequency BW nagano Municipal HospitalDepartment of RadiologyNagano Municipal HospitalZ JIS Z4915 X 240mm acba) Reformat imageb) Reformat imagec) nagano Municipal HospitalDepartment of RadiologyNagano Municipal HospitalabPhase FSEEPI