Table 1. Short and ultrashort echo time (TE) imaging techniques.
| Technique | Radiofrequency pulses and gradient | k-space trajectory |
| Single point [29] | Non-selective hard pulse with gradient applied | 3D point-by-point |
| Multipoint [30] | Hard pulse with gradient applied | 3D partial lines |
| Several points | ||
| UTE [31,159-161] | 2D two half pulses | Radial from centre out |
| BLAST [162] | 3D hard pulse | FID acquisition |
| PETRA [163] | No gradient applied during radiofrequency | |
| ZTE [164] | ||
| BLAST | ||
| PETRA | ||
| ZTE | ||
| WASPI [32] | 3D hard pulse with gradient on. Preparation pulses with water and fat signal suppression | Radial from centre out, FID acquisition |
| Gradient echo | 2D, 3D | Radial rephasing gradients |
| Cones [165] | 3D | Spiral, from centre out, FID data collection |
| Spiral [166] | ||
| Stack of spirals [33] | ||
| Echo planar imaging [167] | ||
| Twisted radial projection [168] | ||
| bSSFP [116,169] | ||
| bUTE [170] | ||
| VIPR-ATR [171] | ||
| bUTE | ||
| VIPR-ATR | ||
| SWIFT, SEA [34-37] | 3D radiofrequency sub-pulses | Radial, centre out |
3D, three-dimensional; 2D, two-dimensional; UTE, ultrashort TE; BLAST, back projection low angle shot; PETRA, pointwise encoding time reduction with radial acquisition; ZTE, zero TE; WASPI, water- and fat-suppressed proton projection imaging; FID, free induction decay; bSSFP, balanced steady-state free precession; bUTE, balanced UTE; VIPR-ATR, vastly undersampled isotropic projection reconstruction-alternating length repetition times; SWIFT, sweep imaging with Fourier transformation; SEA, simultaneous excitation and acquisition.