(SMASH) A very fast gradient echo sequence.

See Ultrafast Gradient Echo Sequence.

(TurboFLASH) This FLASH-based sequence use an inversion pulse followed by a low flip angle and short TR gradient echo train. This gradient echo technique forms complete images in times short compared to T1. Images obtained in this way have very little intrinsic contrast, maintaining adequate signal requires that losses (and therefore contrast).

See also Ultrafast Gradient Echo Sequence and Fast Low Angle Shot.

(HASTE) A pulse sequence with data acquisition after an initial preparation pulse for contrast enhancement with the use of a very long echo train (Single shot TSE), whereat each echo is individually phase encoded. This technique is a heavily T2 weighted, high speed sequence with partial Fourier technique, a great sensitivity for fluid detection and a fast acquisition time of about 1 sec per slice. This advantage makes it possible for using breath-hold with excellent motionless MRI, e.g. used for liver and lung imaging.

See also Segmented HASTE.

Lung imaging is furthermore a challenge in MRI because of the predominance of air within the lungs and associated susceptibility issues as well as low signal to noise of the inflated lung parenchyma. Cardiac and respiratory triggered or breath hold sequences allow diagnostic imaging, however a comparable image quality with computed tomography is still difficult to achieve.
Assumptions for lung MRI:
The current trends in MRI are the use of new imaging technologies and increasingly powerful magnetic fields. Among these technologies are parallel imaging techniques as well as ventilation agents like hyperpolarized helium for the use as an inert inhalational contrast agent to study lung ventilation properties. With hyperpolarized gases clear images of the lungs can be obtained without using a large magnetic field (see also back projection imaging). Single shot sequences (e.g. TSE or Half Fourier Acquisition Single Shot Turbo Spin Echo HASTE) used in lung MR imaging benefits from parallel imaging techniques due to reduced relaxation time effects during the echo train and therefore reduced image blurring as well as reduced motion artifacts.
In the future, more effective contrast agents may provide an alternative solution to the need for high field MRI. Dynamic contrast enhanced MRI perfusion has demonstrated a potential in the diagnosis of pulmonary embolism or to characterize lung cancer and mediastinal tumors. 3D contrast enhanced magnetic resonance angiography of the thoracic vessel.

See also the related poll result: 'MRI will have replaced 50% of x-ray exams by'

(EPI Factor) The imaging speed in Echo Planar Imaging (EPI) depends on many factors. Single shot EPI should provide images within 100 ms or less. Because of this limitations, a multi shot EPI approach is in most cases preferred. The parameter 'EPI Factor' is used to specify the number of k-space profiles collected per excitation.
The EPI factor 64 means a measurement time 64 times faster than a normal gradient echo sequence. See also Echo Planar Imaging.