Nobody downloaded yet

Factors affecting quality of MRI image.Benefits of circular or square spiral EPI methods - Essay Example

Comments (1) Cite this document
Accurate image reconstruction depends on resonance frequency (rf) of a spin,achieved by strong homogenous external field and superposition of a spatially linear gradient. If these conditions are not met, then the relative positions of anatomical structures will be misrepresented…
Download full paperFile format: .doc, available for editing
GRAB THE BEST PAPER96.7% of users find it useful
Factors affecting quality of MRI image.Benefits of circular or square spiral EPI methods
Read TextPreview

Extract of sample "Factors affecting quality of MRI image.Benefits of circular or square spiral EPI methods"

Download file to see previous pages For example, if a spin is exposed to a magnetic field different from the expected value due to magnetic susceptibility, geometric distortions will be seen from the MRI image (Reinsberg, Doran, Charles-Edwards, and Leach, 2005). In particular, an increased spin produces MRI signals of low intensity, while high magnetic susceptibility areas are seen as areas of total signal loss (Zhou and Gullapalli, 2006). Figure 1 shows an example of metallic susceptibility distortions in the presence of metallic implants. Magnetic susceptibility In magnetic resonance imaging, tissues are temporarily magnetized by the large magnetic field that the imaged subject is exposed to, with the extent of magnetization varying among tissues that differ in magnetic susceptibility. For example, relative to other tissues, air and bone are less susceptible to magnetization. On the other hand, metallic implants have high magnetic susceptibility as compared to the body tissues. These differences in magnetic susceptibility cause field inhomogeneity, especially in tissue boundaries, particularly air-tissue and bone-soft tissue boundaries (Zhou and Gullapalli, 2006). That is why magnetic susceptibility distortions are sometimes seen in such boundaries, like the sinuses (Reinsberg, Doran, Charles-Edwards, and Leach, 2005). 1. Discuss various methods to correct for magnetic susceptibility distortions, while maintaining a good EPI image. ...
a.) Parameters that can optimize EPI image ESP can be decreased through the use of powerful gradients, such as increased gradient slew rate (~20, 000 T/m/s), increased maximum amplitude (350 mT/m), increased rise time rate, increased accuracy, decreased eddy currents, increased voltage, and decreased field strength. In addition, these parameters decrease signal-to-noise ratio. Meanwhile, a decreased ESP results to a smaller total train length time. In fact, it has been estimated that decreasing ESP to 40 ms limits the distortion to only one pixel wide. Similarly, increased data gathering via decreased frequency- and phase encoding steps and ramp sampling, fast analogue to digital converters and large receiver bandwidth decrease the time in which phase errors can accumulate (McMahon, 2012). On the other hand, phase and read directions can be swapped, so that the phase encoding gradient is along the same axis as susceptibility gradients. Although this may not totally prevent distortion, it shows the image in a more presentable and understandable manner (McMahon, 2012; Zhou and Gullapalli, 2006). Figure 2 shows the decrease in magnetic susceptibility upon converting from left-right phase encoding to anterior-posterior phase encoding. Other ways to minimize magnetic susceptibility distortions include decreasing the resolution, use of SE sequence, increased acquisition matrix and proper shimming before image acquisition. It should be noted, however, that heating of nearby tissues can occur when using fast SE acquisition with a high bandwidth to decrease magnetic susceptibility distortions resulting from metallic implants (Zhou and Gullapalli, 2006). b) Chain of consequences after increasing the receiver bandwidth Receiver bandwidth is a ...Download file to see next pagesRead More
Cite this document
  • APA
  • MLA
(“Factors affecting quality of MRI image.Benefits of circular or square Essay”, n.d.)
Retrieved from
(Factors Affecting Quality of MRI image.Benefits of Circular or Square Essay)
“Factors Affecting Quality of MRI image.Benefits of Circular or Square Essay”, n.d.
  • Cited: 0 times
Comments (1)
Click to create a comment or rate a document
wilkinsonjamey added comment 9 months ago
Student rated this paper as
Good paper! Used it to finish an assignment for a physics course. It was easy as ABC, for the first time in my life.

CHECK THESE SAMPLES OF Factors affecting quality of MRI image.Benefits of circular or square spiral EPI methods

Echo Planar Imaging, or EPI, Fast Imaging Techniques (MRI)

...? Echo Planar Imaging, or EPI, Fast Imaging Techniques (MRI) Echo Planar Imaging, or EPI, Fast Imaging Techniques (MRI) Answer 1 The concept of EPI was first presented in 1977 by Mansfield. On the other hand, different technical issues related to EPI have been overcome in the last decade. EPI is a fast, flexible imaging method, with good contrast and resolution, and with many potential applications in clinical imaging, such as functional MRI and rapid entire brain...
15 Pages(3750 words)Essay

Echo Planar Imaging, or EPI, Fast Imaging Techniques (MRI)

...detection during the readout phase 2- What are the benefits of using circular spiral or square spiral EPI methods? (2 marks) Specific benefits come with the application of either the circular or the square spiral EPI’s. To start with, for the case of the square spiral EPI, the process of data collection begins from the middle and spirals in to a larger K as the time passes. This is majorly an advantage achieved through the use of different timing and amplitudes in the...
10 Pages(2500 words)Essay

Magnetic Resonance Image(MRI)

...are pulsed. These noises can be as loud as 125 decibels, similar to the noise of a door being slammed or a balloon being burst close to the ear. Efforts are being made to make the cylindrical opening larger and to dampen the noises (Steckner, 2006). The quality of the MRI image depends on “Signal to Noise Ratio” between the signals from the Hydrogen protons and the noise from other sources. Advanced signal filters and digital electronics technologies are being applied for MRI image processing. One significant problem that still remains is the need for accurate comparison of MRI scan images taken several weeks apart. It...
8 Pages(2000 words)Research Paper


...produce increased specificity of diagnosis. Use of GRAPPA There are also some situations when GRAPPA is more advantageous that SENSE. This means that GRAPPA will be preferred. Examples of applying GRAPPA in clinical application is the abdominal and lung MRI. GRAPPA is applied in these fields when it is difficult to achieve accurate coil sensitivity. Lungs and the abdomen have low spin density. However, determining spatial coil sensitivity is in the difficult. GRAPPA is preferred because good image quality is achieved because information sensitivity is obtained from the k-space. The lines that are used in the centre of the k-space ensure that good reconstruction quality...
10 Pages(2500 words)Assignment

Factors Affecting Marketing Strategy

...26,251,000 children, which is much lower than the current market size (Fields, 2004). The advertisement campaigns at that point of were less aggressive as the level of competition was less. Today, in order to place the non-branded products, a lot of promotion and advertisement is required to meet the growing demand of present and future. Moreover, with the growing trend of the prospects by 2025, the projected target market is expected to grow further to 114,052,000 (United States Census Bureau, 2012). The factors that affect the market segment of the cereal consumption include the price of the product which is strategized to meet the requirement. The quality of the product which is of...
6 Pages(1500 words)Essay

Factors Affecting Marketing Strategy

...for about 7.7% (United States Census Bureau, 2013). Moreover, the target segment would expand by another 8.9% in the coming ten years. Upon understanding the dynamics of soft drink industry in USA, it is found that the following three factors have an impact on the consumer behavior of this industry: 1. The top most influential factor in this regard is health concerns amongst consumer circles. Consumers perceive that carbonated or fizzy drinks have wrong affects on their health and thus avoid drinking soft drinks at all or usually purchase these drinks. 2. Size and design of the packaging also influences consumer behavior. If a soft drink is offered in a glass bottle, it is not possible...
5 Pages(1250 words)Term Paper

External Factors Affecting Recruitment

...External Factors Affecting Recruitment Factors affecting Recruitment and Retention of Entry-level Housing and Residential Life Staff Authors Onge, Steven St., Ellett, Thomas, & Nestor, Eric M. Name of Publication The Journal of College and University Student Housing Date of Publication October/November 2008. Summary of the Article The article is an attempt of a team of experts that have focused on the recruitment and retention practices of entry-level staff in residence life programs locally, as well as internationally. In specific, chief housing officers are the major stakeholders of this article who have provided their perspectives to identify issues in such processes...
2 Pages(500 words)Article


...the employment of a considerably higher frequency encoding gradient heft. Resultantly, the freedom to cut down the geometric distortion will have lengthened. Moreover, it is worth noting that an increased rBW allows a shorter echo-spacing in the turbo spin echo (TSE) echo train as well as a shorter minimum echo delay time (TE) (Ye et al, 1996, p.220). Benefits of circular spiral and/or square spiral EPI methods There are a number of alterations to the Echo Planar Imaging method. Some of these include constant phase encoding, circular square sampling and...
10 Pages(2500 words)Essay

Factors affecting the salary

...on the factors affecting the pay-setting procedure and the factors influencing it. There is a common belief that executives are in a powerful position thereby set their own salaries. Others view the increase in CEO compensation as a result of increased competition for the executive talent. The paper further describes the empirical evidence on the development in the executive compensation and on the link between the firms’ performance and compensation since the 1930s.The paper states that the competitive forces in the market and executives’ power are significant factors that impact on managerial compensation. The review concludes that competitive forces in the market and...
8 Pages(2000 words)Essay

Factors Affecting Customer Satisfaction

... Factos Affecting Customer Satisfaction Abstract Uber application allows commuters to place their services and to access their preferred services at a tap on their mobile phones. With quality measures, through interaction with customers in the social media, the application is gaining popularity despite concerns that some consumers have raised. Three models are proposed for significance of cost efficiency, use of credit and debit cards for payment, and value for social interactions in social media as factors to the growing popularity of the app. Using questionnaires to collect data on respondents’ factors to usage of the app, critical experiments are implemented,...
2 Pages(500 words)Research Paper
sponsored ads
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.

Let us find you another Essay on topic Factors affecting quality of MRI image.Benefits of circular or square spiral EPI methods for FREE!

Contact Us