(DE FGRE, Dual/FFE, DE FFE) Simultaneously acquired in and out of phase TE gradient echo images. To quantitatively measure the signal intensity differences between out of phase and in phase images the parameters should be the same except for the TE.
The chemical shift artifact appearing on the out-of-phase image allows for the detection of lipids in the liver or adrenal gland, such as diffuse fatty infiltration, focal fatty infiltration, focal fatty sparing, benign adrenocortical masses and intracellular lipids within a hepatocellar neoplasm, where spin echo and fat suppression techniques are not as sensitive. Specific pathologies that have been reported include liver lipoma, angiomyolipoma, myelolipoma, metastatic liposarcoma, teratocarcinoma, melanoma, haemorrhagic neoplasm and metastatic choriocarcinoma.

(DE - dual / double echo) Dual echo sequences include images with different weightings and / or echo times and are used to obtain both, proton density and T2 weighted images or in phase and out of phase gradient echo images, simultaneously without increasing the measurement time.

(DESS) This sequence was originally known as FADE. It combines both the gradient echoes acquired in FISP and PSIF sequences in separate acquisition periods during a single interpulse interval. Phase encoding gradients are balanced to maintain the transverse steady state signals. The frequency encoding gradient is left on for the period of both the echoes, and is incompletely balanced to avoid dark banding artifacts otherwise associated with long TR fully balanced steady state sequences. The contrast of DESS is quite unique, true T2 or T1 contrast weighting is not possible. There is a strong fluid signal but fat is bright and other soft tissues appear similar to the short TR FISP image.
Used for, e.g. the joints, cartilage and the prostate.

See Steady State Free Precession and Dual Echo Sequence.

(Dual/FFE) A FFE technique with simultaneously acquired in and out of phase gradient echoes.

See Dual Echo Fast Gradient Echo.

Duty cycle is the time during which the gradient system can be run at maximum power. The duty cycle is based on the total time and includes the cool down phase. The duty cycle on the RF pulse during MRI is restricted based on the specific absorption rate (SAR) limit.
SAR limits restrict radio frequency heating effects. The specific absorption rate increases with field strength, radio frequency power and duty cycle, type of the transmitter coil and body size. The especially in high and ultrahigh magnetic fields, important SAR issue can be readily addressed by reducing the RF duty cycle due to longer repetition times (TR) and the use of parallel imaging techniques. A TR longer than the minimum needed provides time for the tissue to cool down, but for the cost of a longer scan time. A parallel imaging technique reduces the RF exposure and the scan time.

See also High Field MRI.