TSE轮廓阶数与MSK图像质量.ppt

LinearSignal to Point Spread Function Fluid Cartilage Fat Phase encoding – signal Point Spread Function Phase encoding – time Phase encoding step Phase encoding step y (pixels) Time (ms) Signal Signal TSE 3 LinearCartilage PSF versus TSE Factor, fixed TE TSE 3 TSE 5 TSE 5 TSE 9 TSE 9 Phase encoding step Phase encoding step y (pixels) Time (ms) Signal Signal Linear, constant TE (30 ms): TSE Factor does not influence blurring TSE 5 TSE 9 TSE 3 LinearCartilage PSF versus TE/Shotlength Phase encoding step Phase encoding step y (pixels) Time (ms) Signal Signal TSE 11 TSE 21 TSE 5 Linear, constant ES (10 ms): TSE factor changes contrast, blurring LinearSummary Shotlength ? 2 TE Echo Spacing = 2 TE / (TSE+1) Sequence is completely fixed by TE and TSE factor Pro: Very robust against blurring For PD contrast no blurring of cartilage TE the same, blurring the same Con: Low SNR Empty sequence Limited to low turbofactors for low TE Longer acquisition times Linear HalfscanCartilage PSF Phase encoding step Phase encoding step y (pixels) Time (ms) Signal Signal TSE 10 Echo Spacing 10 ms TE 30 ms Linear HalfscanCartilage PSF Phase encoding step Phase encoding step y (pixels) Time (ms) Signal Signal Linear 5 Mirrored Zerofilled Linear Halfscan: conjugate reconstruction improves PSF TSE 10 Echo Spacing 10 ms TE 30 ms Linear HalfscanHalfscan factor, Fixed TE Signal (a.u.) Phase encoding step Phase encoding step y (pixels) Time (ms) Signal Signal TSE 10 TE 30 ms Linear 5 Halfscan 0.65 Halfscan 0.58 Halfscan 0.90 Linear Halfscan: reducing halfscan factor increases echo spacing and shotlength, and increases blurring Linear HalfscanHalfscan factor, Fixed TE Like here… Linear HalfscanTE, fixed Halfscan factor Signal (a.u.) Phase encoding step Phase encoding step y (pixels) Time (ms) Signal Signal Linear 5 TE 20 TE 30 TE 15 TSE 10 Halfscan 0.6 Linear Halfscan: increasing TE directly increases echo spacing and shotlength, and increases blurring Linear HalfscanSummary Shotl