The time at which this echo is produced is the TE (time to echo). The thin bar denotes a 90° pulse, while the thick bar denotes a 180° pulse. The decay in the signal from the original 90° to the echo is due to the tissue characteristic T2 effect with the effect of magnetic field inhomogeneities minimised. The FSE/TSE pulse sequence superficially resembles a conventional spin-echo (CSE) sequence in that it uses a series of 180º-refocusing pulses after a single 90º-pulse to generate a train of echoes. A new approach is to insert a short frequency-selective saturation pulse before each spatially selective observation pulse in a standard, two-dimensional, gradient-echo pulse sequence. flip angle) ein weiterer Parameter. If a short TR is needed (for example, in T1 weighted scans), we need to cut down the scan time. A T 1-weighted imaging pulse sequence for contrast-based studies of myocardial perfusion is presented and evaluated in phantoms and in vivo. Beispiel: 2500-30-900 bedeutet TR von 2500 msek, TE von 30 msek und eine TI von 900 msek. In spin-echo pulse sequences, T2* dephasing is eliminated by the 180° RF rephasing pulse because magnetic field inhomogeneities are largely predictable. T2 decay is not affected by the 180° RF rephasing pulse because this is caused by spin–spin interactions, which randomly fluctuate [1]. INEPT is a common building block of NMR experiments to improve 15 N signal. Alle diese Parameter sind variierbar. Graphical representation of a pulse sequence for a homonuclear NOESY experiment. Spin echo and gradient echo pulse sequences follow similar contrast behaviour but there are some key differences. There are two ways of rephasing the magnetic moments of hydrogen nuclei to produce an echo – by using an additional 180° RF pulse or by using gradients. gradient echo pulse sequence: ( grā'dē-ĕnt ek'ō pŭls sē'kwĕns ) magnetic resonance imaging Modality that uses a gradient to regenerate an echo. SE-EPI sequence; HASTE sequence; Radial Gradient echo sequence; Create a 2D selective RF pulse; Spiral sequence; Trufi sequence; Turbo spin echo sequence; UTE sequence; UTE sequence with ramp sampling; Scanner implementations. Bei der Gradient-Echo-Sequenz ist zudem der Anregungswinkel (alpha, engl. This is done by removing the 180° refocusing pulse. Interleaved, multislice imaging is straightforward. This change will speed up our scan time. In the pulse sequence timing diagram, the basic gradient echo sequence is illustrated. An INEPT NMR pulse sequence for a heteronuclear experiment. Sequences that use a 180° RF rephasing pulse to generate an echo are called spin-echo pulse sequences; those that use a gradient are called gradient-echo pulse sequences (see Chapter 4). This is the overall gradient echo imaging sequence, so this prephase and frequency encoding gradient generate gradient echo. Being much less than T 1 apart, the saturation pulses have a cumulative effect. Currently, Pulseq sequences can be executed on the following platforms.