spread MRI, the commonly used magnetic resonance imaging method, produces in vivo images of biological tissues weighted with local microstructural characteristics of water spread. In spread-weighted imaging, each image voxel has an image intensity that reflects a single best measurement of the rate of water spread at that location. This measurement is more sensitive to early changes after a stroke than other MRI measurement methods, such as: T1 or T2 relaxation rates.
High signal to noise ratio is very important in spread MRI imaging (DWI). This is typically attained by implementing stronger gradient performance to reduce the time required for spread- sensitization and signal acquisition, thereby shortening the minimum attainable time-to-echo (TE) of the DWI ordern. similar imaging can also be used to further reduce the time required for signal acquisition.
Higher gradient performance and similar imaging provide additional benefits to image quality, by reducing distortion and susceptibility artefacts.
DWI applications assistance from higher gradient performance, as DWI sequences tend to need the complete possible of gradient performance. However, gradient systems are only likely to enhance marginally in the future compared to the high- specification MRI systems currently obtainable, because of safety restrictions based upon physiological stimulation limits.
Overall image quality will additionally assistance from any measure to actively reduce the effect of eddy current-induced spatial distortions, such as: dedicated spread encoding schemes or optimized gradient wire design. In general, actions taken on the acquisition side are preferable, as compared to post-processing techniques.
A different approach to increasing the SNR of the DW image would be to perform DWI studies on an MRI system with a higher magnetic field. For example, the SNR is expected to increase twofold from 1.5 to a 3T system. DWI studies on 3T systems can consequently assistance from a more extensive image contrast range, than equivalent studies on 1.5T systems. However, with the increase of the magnetic field, image quality becomes more sensitive to susceptibility and distortion artefacts.
consequently, higher gradient specifications and similar imaging are more applicable and provide meaningful improvements to image quality in DWI studies on 3T RI systems.
spread MRI imaging is prone to signal misregistration from fat tissues. In order to minimize the fat signal, special fat-suppression techniques are used, whose effectiveness is likely to be dependent on main magnetic field homogeneity. DWI can be more sensitive to hardware defects than standard imaging applications. Degradation of image quality in DWI is typically associated with problems in the performance of gradient or shimming coils. DWI should, if possible, be included in a quality- control program, especially in situations of long- term, comparative or quantitative studies.
spread MRI imaging sequences last only a few seconds and can consequently be used as an adjunct to traditional MRI studies without meaningful increase in examine duration. DWI sequences are also simple to implement as the b-value is the main determinant of image contrast. In addition, there is no need for contrast agent injection or physiological monitoring. However, progressive DWI examination, for example: calculation of DTI, can assistance from electrocardiogram gating. Although the risks in this mode are reduced and scanning with DWI is extremely short, there is a small possibility of experiencing minor peripheral nerve stimulation. In addition, acoustic noise levels during DWI sequences tend to be higher than traditional MRI techniques and hearing protection should be provided to minimize patient discomfort and prevent permanent hearing loss.