Myocardial perfusion sequences

Myocardial Perfusion Sequences Dynamic First-Pass Perfusion Image Acquisition • ECG triggering: repeats same few slices every heartbeat   Post injection Baseline equilibrium Contrast Bolus injection Image acquisition Dynamic First-Pass Perfusion • Each slice consists of a magnetization prep and a data collection R R ECG Slice # Prepare Magnetization T1 Sensitivity (90o SR prep) Acquire Image (slice) Dynamic First-Pass Perfusion • Two possible types of magnetization preparation • Inversion Recovery (180o pulse) – Very strong T1 contrast – Multi-slice imaging not feasible – Sensitive to arrhythmia • Saturation Recovery (90o pulse) – Weaker T1 contrast – Multi-slice imaging capable – Insensitive to arrhythmia Most commonly used Dynamic First-Pass Perfusion Saturation Recovery (90) Preparation R ECG Trigger Mz 0,80 TI 90° N ||||||||||||||||||| Non-Ischemic Myocardium (short T1) evolution period 0,60 acquisition period 0,40 Ischemic Myocardium (long T1) 0,20 0,00 100 200 300 400 500 time / msec • T1 contrast weaker than IR • Insensitivity to Arrhythmia • Multi-slice capabilities • CNR & SNR depend on TI Dynamic First-Pass Perfusion Adjusting the TI R R ECG Trigger Acquisition Window 90°    | | | | | | | | | | | | | | | TI (> minimum) The shortest possible TI (zero Use Extra Evolution Time evolution period) reduces the total time to acquire the slice, 90° but reduces the CNR & SNR    | | | | | | | | | | | | | | | TI (= minimum) Dynamic First-Pass Perfusion • acquires a few slices every heartbeat R R ECG Trigger Acquisition Window 90°  slice | | | | | TI 90°  slice | | | | | TI Echo-Spacing 90°  slice | | | | | TI Trig Delay (typically zero) TR TR Ti Dynamic First-Pass Perfusion Pulse Sequences • TurboFLASH – – – – Inherent T1-weighting Insensitive to off-resonance As short as msec per line Low SNR due to high BW and short TR • TrueFISP – – – – Most commonly used Inherent T1/T2 weighting Sensitive to off-resonance As short as 2.2 msec per line High SNR due to steady-state signal contribution TurboFLASH  vs TrueFISP   TR TR Gslice Gslice Gread Gread Gphase Gphase Spoiler Pulse + Unbalanced Gradients: Insensitive to Field Inhomogeneity Artifacts Lower SNR  Steady State + Balanced Gradients: Plagued by Field Inhomogeneity Artifacts Higher SNR Dynamic First-Pass Perfusion Pulse Sequences TurboFLASH Spoiler Pulse + Unbalanced Gradients: Insensitive to Field Inhomogeneity Artifacts Lower SNR TrueFISP Steady State + Balanced Gradients: Plagued by Field Inhomogeneity Artifacts Higher SNR Dynamic First-Pass Perfusion Option 1: Using iPAT alone has advantages, but disadvantage R R ECG Trigger Acquisition Window 90°    No iPAT | | | | | | | | | | | | | | | TR Evolution + Longer evolution time = better CNR 90°    ||||| | | Evolution + Shorter TR = more slices + Shorter data period = less motion sensitive TI With iPAT Using iPAT alone each slice has: | | - Fewer echoes = decreased SNR Note: TI is same in both, time to center of data TR Dynamic First-Pass Perfusion Option 2: Using iPAT with Lower Bandwidth has advantages, but disadvantage R R ECG Trigger Acquisition Window 90°    No iPAT | | | | | | | | | | | | | | | Using iPAT with Lower Bandwidth each slice has: TR Evolution + Decreased bandwidth = better SNR TI 90°    With iPAT | | | | | | Evolution + Wider echo spacing = better CNR | | | TR + Better SNR = allows higher matrix - Fewer echoes = decreased SNR Note: TI is same in both, time to center of data Dynamic First-Pass Perfusion Rest Rest 128 Matrix + no iPAT 192 Matrix + iPATx2 + Lower BW Stress Stress Dr Ching Hon Luk, Sir Run Run Shaw Heart Center, Hong Kong ... First-Pass Perfusion • Each slice consists of a magnetization prep and a data collection R R ECG Slice # Prepare Magnetization T1 Sensitivity (90o SR prep) Acquire Image (slice) Dynamic First-Pass Perfusion. ..  slice | | | | | TI Trig Delay (typically zero) TR TR Ti Dynamic First-Pass Perfusion Pulse Sequences • TurboFLASH – – – – Inherent T1-weighting Insensitive to off-resonance As short... Balanced Gradients: Plagued by Field Inhomogeneity Artifacts Higher SNR Dynamic First-Pass Perfusion Pulse Sequences TurboFLASH Spoiler Pulse + Unbalanced Gradients: Insensitive to Field Inhomogeneity