DANTE gradient pulse

When implementing this sequence it may be necessary to add attenuation to the transmitter to increase the duration of each pulse so that the shorter elements do not demand very short (< 1 xs) pulses (note the similarity with the requirements for the DANTE hard-pulse selective excitation described above). The binomial sequences can be adjusted to provide an arbitrary overall tip angle by suitable adjustment of the tip angles for each element. For example, inversion of all off-resonance signals can be achieved by doubling all elements relative to the net 90 condition. Exactly this approach has been exploited in the gradient-echo methods described below. 

The excitation sculpting method was expended to the selective inversion of z-magnetisation. The method utilises DANTE train of hard pulses combined with gradient suppression of transverse magnetisation. Application of the selective inversion to z-magnetisation reduces relaxation loses and extends selective methods to larger molecule. Use of shaped pulses in DANTE train produces band-selective inversion. The proposed inversion method can be... 

The basic principle is depicted in Fig. 6.2.16(a) [Cho2]. The rf excitation is a train of small flip-angle pulses forming a DANTE sequence, i.e., the sum of flip angles is 90° (cf. Section 5.3.4). They are applied while the read gradient Gx is tuned on. The response to the DANTE excitation is refocused in a Hahn echo, which itself consists of a train of echoes. This echo train is detected in the presence of the read gradient Gx... 

Fig. 6.2.16 [Cho2] 2D DANTE-imaging. (a) Timing of signals. The rf excitation is a DANTE pulse train applied in a read gradient Gx- The Hahn echo of the response is detected while both the phase-encoding gradient Gy and the read gradient Gx are turned on. The slice-selection gradient is Gj. (b) Traces in k space.

Fig. 7.2.16 [Kos3] 2D tagging f liingitudinal magnetization, (a) Sequence of two DANTE pulses applied in orthogonal field gradients, (b) Spin-echo image of water at rest in a tube measured with a delay time of 64 ms between the tagging pul.ses and the start of data acquisition.

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