A Three-Dimensional NMR Imaging Scheme Utilizing Doubly Resonant Gradient Coils

Magic Echo Solid-State NMR Imaging without a Rapidly Switchable Field Gradient

“…This significantly relaxes the high-speed requirement on the gradient system. The utility of the sinusoidal gradient for solid-state imaging was also described in other imaging schemes (10,11).…”

Continuous-Wave Magnetic Resonance Imaging of Short T2 Materials

“…These fall into three main types: those that reduce the linewidth through manipulation of the sample, the gradients, or the RF pulses (1)(2)(3)(4)(5)(6), those that use large gradients to compensate for broad lines and minimize the period between pulse application and signal acquisition (7)(8)(9)(10)(11)(12)(13), and those that use pure phaseencoded acquisition with modest gradient strength (14 -17).…”

“…The three most widely used approaches are oscillating magnetic field gradient imaging (8), stray field imaging (STRAFI) (9 -13), and single-point ramped imaging with T 1 enhancement (SPRITE) (14 -17). The oscillating magnetic field gradient technique uses resonant gradient coil circuits to produce large, rapidly changing gradients.…”

Continuous wave MRI of heterogeneous materials

“…Strong relaxation effects due to dipolar interactions result in very short T 2 relaxation times, often much shorter than the dead-time of techniques employing conventional spin-echo methods. A number of approaches have been developed to overcome these problems, the most successful of which involve the use of large gradients to overcome the broad linewidths [5,6], or use pure phase-encoded acquisition with modest gradient strengths [7]. Techniques employing very strong magnetic field gradients include: stray field imaging (STRAFI), which uses the very large static magnetic field gradient present in the fringe field of a superconducting magnet, together with repeated acquisitions between which the sample is moved or the magnetic field or RF frequency is adjusted, to determine the spin density of successive slices through the sample [5,8]; and the oscillating gradient technique, which incorporates the gradient coils within a resonant circuit, so that modest gradient strengths can be obtained relatively easily [6,9,10].…”

“…A number of approaches have been developed to overcome these problems, the most successful of which involve the use of large gradients to overcome the broad linewidths [5,6], or use pure phase-encoded acquisition with modest gradient strengths [7]. Techniques employing very strong magnetic field gradients include: stray field imaging (STRAFI), which uses the very large static magnetic field gradient present in the fringe field of a superconducting magnet, together with repeated acquisitions between which the sample is moved or the magnetic field or RF frequency is adjusted, to determine the spin density of successive slices through the sample [5,8]; and the oscillating gradient technique, which incorporates the gradient coils within a resonant circuit, so that modest gradient strengths can be obtained relatively easily [6,9,10]. The single point imaging technique (SPI, or its variant SPRITE, single-point ramped imaging with T 1 enhancement) is a pure phase-encoding method, which acquires a single data sample at a fixed time after the application of an RF pulse, and repeats this as the gradient is incremented [7,11,12].…”