This is for my MRI physics class. I need to discuss my topic which is “fast grad
This is for my MRI physics class. I need to discuss my topic which is “fast gradient echo sequence.” < It does not need to be a whole essay it can be a paragraph or two. < You can add pictures too < < I got this from the book. Don't copy it, turn it in your own words. < < Fast gradient echo Very fast pulse sequences have been developed that can acquire a volume in a single breath hold. These usually employ coherent or incoherent gradient echo sequences but the TE is significantly reduced. This is achieved by applying only a portion of the RF excitation pulse so that it takes much less time to apply and switch o?. Only a proportion of the echo is read (partial echo). These measures ensure that the TE is kept to a minimum so that the TR and therefore the scan time can be reduced accordingly. In addition, many fast sequences use extra pulses, applied before the pulse sequence begins, to pre-magnetize the issue. In this way, certain contrasts can be obtained. This pre-magnetization is achieved in the following two ways. < < A 180° pulse is applied before the pulse sequence begins. This inverts the NMV into full saturation, and at a speci?ed delay time, the pulse sequence itself begins. This can be used to enhance T1 contrast or to null signal from certain organs and tissues and is similar to inversion recovery. < < A 90°/180°/90° combination is applied before the pulse sequence begins. The ? rst 90° pulse produces transverse magne ti za ti on. The 180° pulse rephases this, and at a speci?ed time later the second 90° pulse is applied. This drives the coherent transverse magnetization into the longitudinal plane so that it is available to be ?ipped when the pulse sequence begins. This is used to produce T2 contrast and is sometimes known as driven equilibrium ( see also DRIVE which uses a similar principle). Fast gradient systems permit multi-slice gradient echo sequences with TEs as short as 0.7 ms. Multiple images can therefore be acquired in a single breath hold and are free from respiratory motion artefacts. In addition, fast gradient echo acquisitions are useful when temporal resolution is required. This is especially important after the administration of contrast when the selection of fast gradient echo permits dynamic imaging of an enhancing lesion. This important technique has applications in many areas, including the abdominal viscera and the breast.
