Real-time cardiac cine imaging with SPIDER: steady-state projection imaging with dynamic echo-train readout

Steady-state projection imaging with dynamic echo-train readout (SPIDER) is a multiecho radial k-space trajectory TrueFISP sequence developed for real-time cine imaging of the heart. This new pulse sequence combines the superior SNR and blood-to-myocardium contrast of TrueFISP with the increased scan time efficiency of EPI and undersampled projection reconstruction. SPIDER sequence RF repetition time (TR) was minimized by limiting the echo-train to a length of three while acquiring the first and third echoes asymmetrically. A temporal resolution of 45 ms was achieved with TR/TE1/TE2/TE3 of 3.24/0.6/1.6/2.6 ms and a factor of 2 view sharing scheme. Phantom experiments showed little difference between the weighting of the signals acquired at each of the echo times but did show considerable off-resonance modulation between them. In vivo experiments demonstrated the feasibility of using the SPIDER sequence for real-time imaging in the cardiac short axis orientation.