We use cookies to create the best experience for you. Keep on browsing if you are OK with that, or find out how to manage cookies.
Nobody downloaded yet

EPI7005_2 - Essay Example

Comments (0) Cite this document
Summary
EPI7005_2 By Course of Learning: Date: Magnetic Susceptibility Tissues adjacent to each other yet having different magnetic susceptibilities lead to the disruption of the local field. Examples of these tissues include the interfaces involving bones and tissues that are found in the sinus and in the lungs like the maxillary, mastoid, and the ethmoid sinuses…
Download full paperFile format: .doc, available for editing
Polish This Essay94% of users find it useful
EPI7005_2
Read TextPreview

Extract of sample
"EPI7005_2"

Download file to see previous pages Such inhomogeneties may be a result in some imperfection within the magnet or magnetic susceptibility spatial variation of the object that is being imaged (Christ, 2000, p. 78). The spatial variation is normally referred to as susceptibility artifacts. EPI applied in most of protocols used in diffusion weighted acquisition uses a homogenous static field. Such a field does not normally hold for MRI head. The distortion that comes out of this is significant enough to even exceed ten millimeters. Such artifacts come in the way of accurate diffusion images alignment with structural MRI and are considered obstacles to the head MRI joint analysis of structure and connectivity. Some of the methods used for correction of magnetic susceptibility distortions include the use of a filed map. However, such methods of applying field maps are not reliable and accurate; hence, they do not result in reliable EPI alignment with structural images that correspond to it. The T2-weighted structural image approach that relies on EPI baseline image and still gives account of the susceptibility artifacts is the recommended approach (Edelman and Schmitt, 1994, p. 610). How accurate the reconstruction of the image is depends on the spin’s resonance frequency (rf) which is formed normally through a spatial linear gradient superposition and an external filed that is homogenous and strong. The above conditions have to meet failure to which the anatomical structures relative positions will end up being misrepresented in the MRI image reconstruction. A good example of this is a case in which a spin is presented to a magnetic field that is not the same as the expected value resulting from the magnetic susceptibility. In this case, the geometric distortions process will be witnessed from the MRI image (Reinsberg, Doran, Charles-Edwards, and Leach, 2005). When the spin is increased, it leads to the production of MRI signals whose intensity is relatively low while areas having high magnetic susceptibility experiencing total signal loss (Zhou and Gullapalli, 2006). Question 1A Several parameters have to be reduced in order to optimize EPI image, and they include: A. Reducing the time of echo train length: the longer the length of the echo train, the more time is required by the spin to gather phase error and the greater the distortion witnessed. One of the ways of minimizing the total time of train length is by minimizing the echo spacing. The less the time is taken by the frequency gradient in sampling the signal, the less the distortion will be witnessed as shown in figure 1. The period for sampling is normally during the flat readout gradient portion unless there is ramp sampling. In FSE, the less the ESP or the echo spacing is, the less the blurring of the image gets. In EPI, minimizing the echo spacing also results in a reduction in the blurring and geometric distortion. Figure 2. The sampling time and the read encoding gradient during normal gradient performance (McMahon, 2012) As the segmentation degree increases, the echo number acquired per rf excitation decreases. This in turn minimizes the geometric distortion as the phase error time of accumulation is reduced. Figure 3 below demonstrates the reduction in ...Download file to see next pagesRead More
Cite this document
  • APA
  • MLA
  • CHICAGO
(“EPI7005_2 Essay Example | Topics and Well Written Essays - 2500 words”, n.d.)
EPI7005_2 Essay Example | Topics and Well Written Essays - 2500 words. Retrieved from https://studentshare.org/physics/1401013-epi70052
(EPI7005_2 Essay Example | Topics and Well Written Essays - 2500 Words)
EPI7005_2 Essay Example | Topics and Well Written Essays - 2500 Words. https://studentshare.org/physics/1401013-epi70052.
“EPI7005_2 Essay Example | Topics and Well Written Essays - 2500 Words”, n.d. https://studentshare.org/physics/1401013-epi70052.
  • Cited: 0 times
Comments (0)
Click to create a comment or rate a document
CHECK THESE SAMPLES - THEY ALSO FIT YOUR TOPIC
EPI7005
Any amount of water proton found in the inhomogeneity of the local field will result in off-resonance. The shift in frequency of such spins varies from one region to another, as well as from one patient to another. However, it will still behave like the off-resonance fat.
16 Pages(4000 words)Essay
Let us find you another Essay on topic EPI7005_2 for FREE!
Contact us:
+16312120006
Contact Us Now
FREE Mobile Apps:
  • About StudentShare
  • Testimonials
  • FAQ
  • Blog
  • Free Essays
  • New Essays
  • Essays
  • The Newest Essay Topics
  • Index samples by all dates
Join us:
Contact Us