MRI Sequences

Key points

Type of sequence	Principles	Advantages	Disadvantages
Spin echo (SE)	simple, SE T₁, T₂, DP contrast	Contrast	Slow (especially in T₂)
Multiecho SE	SE several TE, several images	DP + T₂ images	Slow, even if acquisition of the 2nd image does not lengthen acquisition
Fast SE	SE, echo train effctive TE	Faster than simple SE simple ES contrast	Fat shown as a hypersignal
Ultrafast SE	SE, long echo train, half-Fourier	Even faster	Low signal to noise ratio
IR	RF 180°, TI + ES/ESR/EG	T₁ weighting Tissue suppression signal if TI is adapted to T₁	Longer TR / acquisition time
STIR	IR, short TI 150 ms	Fat suppression signal
FLAIR	IR, long TI 2200 ms	LCT suppression signal
Gradient echo (GE)	< 90° α and short TR No rephasing pulse	+ speed	T₂^* not T₂
GE with spoiled residual transverse magnetization	TR < T₂ Gradients / RF dephasers	T₁, DP weighting
Ultrafast GE	small α and very short TR Gradients / RF dephasers k-space optimization	++ speed cardiac perfusion	Poor T₁ weighting
Ultrafast GE with magnetization preparation	+ preparation pulse: - IR (T₁weighted) - T₂ sensibilization	++ speed AngioMRI Gado Cardiac perfusion / viability
Steady state GE	TR < T₂ Rephasing gradients FID	+ signal ++ speed	Complex contrast
Contrast enhanced steady state GE	Rephasing gradients Hahn echo ( trueT₂)	Not much signal T₂ weighted
Balanced steady state GE	Balanced gradients in all 3 directions T₂/T₁contrast	++ signal, ++ speed Flow correction
Echoplanar	Single GE or multi shot Preparation by SE (T₂), GE (T₂^*), IR (T₁), DW Exacting for gradients	++++ speed Perfusion MRIf BOLD Diffusion	Limited resolution Artifacts
Hybrid echo	Fast SE + intermediary GE	++ speed SAR reduction