MRES7004 Essay Example | Topics and Well Written Essays - 2250 words

MRES7004 - Essay ExampleThe finishing of the sequence produces a FID which is read to get the incline required. Multiple frequencies are produced as the read gradient is applied. The variation of frequencies is linearly connected. The total change of frequency experienced depends on the position inwardly the gradient. later on the FID is acquired, it is treated with a Fourier transform. This produces a spectrum that displays peaks corresponding to different frequencies. The sum total of all signal fervor values at wholeness single place of observation become individual peaks. A one dimensional quantity is produced by the application of the read gradient as it is independent of time. (Weishaupt et al., 2006) Phase focusing Encoding A kind gradient is applied after applying a read gradient and spell selection. This is otherwise known as level encoding and tends to increase the nucleis frequency such that it precesses at different angles that all match up with the Larmor frequ ency. The increase of frequency due to the application of a phase gradient directly impacts the total phase change displayed by nuclei. However there is a strike to discern different nuclei which can be done by the application of Fourier transforms. (Westbrook et al., 2005) Question Two use the Fourier transforms helps to convert the available entropy from the time domain to the frequency domain. This can then be utilise to form two dimensional or three dimensional images based on available data. data is spatially encoded before becoming a part of the k space and so its position within the k space can be determined accordingly. Application of the first Fourier transforms aids in rendering the data values that were encoded in the read direction. This is useful in identifying the frequency (alternatively signal intensity) within the monotonous selected for the application of the read gradient. This makes it simple to differentiate the positions within the k spaces horizontal t rajectory. The data obtained in this way has its units changed from m-1 to m. Consequently only a one dimensional image is formed. (Woodward, 2001) Application of the sulphur Fourier transform helps to differentiate various frequencies that were encoded along the phase direction after the application of a phase gradient. This transform separates all the values and lists them accordingly. The vertical k space trajectories are dealt with this transformation. The units again change from m-1 to m and the resulting image becomes two dimensional. (IMAIOS, 2009) The total k space contains data encoded from two directions that are the read and the phase directions. The read directions data is displayed as horizontal trajectories in the k space spell the phase directions data is displayed as vertical trajectories in the k space. Fourier transforms aid in creating a complete two dimensional image of the concerned nuclear spin densities in congener to the slice positions. (Hashemi et al., 2 004) Question Three Various experimental factors affect transverse spin coherence as well as the k space. These factors and their effects are listed below. Radio Frequency Pulse A radiocommunication frequency pulse at 90o is utilised along with the chief magnetic field to produce magnetic attraction such that the Z direction vector reorients itself into the X plane the Y plane. The magnetism produced is subsequently de-phased some(prenominal) in the X plane and the Y plane. This requires one more re-phasing at 180o. look at Gradient Read