EPI in MRI Essay Example | Topics and Well Written Essays - 2500 words

EPI in MRI - Essay Example Notably, the boundaries existing between fat and compact bone are affected by the rapid de-phasing of the transverse magnetic field as well as distorts the signal. Resultantly, this leads to the wrong positioning of the frequency in the phase direction. K-space line is another parameter that could be optimized so as to change the EPI. A shift in the k-space line from its normal line leads to geometric distortion (Amin & Afzal, 2009, p.232). Such a shift may be resulting from field in-homogeneities. However, this artefact is reduced by spin echo sequences, which do rephrase the spins each time a 180-degree pulse is applied. On the other hand, gradient echo structures of the refocusing of the artefact. Undeniably, EPI makes use of a gradient echo sequence, thus leading to the accumulation of the effect with no radiofrequency (RF) pulse to correct the same. It is worth noting that any accumulation of errors arising from phase encoding will be wrongly registered, thus exposing EPI to thi s artefact. In the event that the duration of the EPI trajectory if considerably long, the EPI itself gets to be affected even by small field in-homogeneities (Ye et al, 1996, p.219). Change in the parameter can be so achieved through increasing the bandwidth. Such an action will lead to a reduction in the echo time (TE). So as to realize more ramp sampling, the dwell time can be increased. In optimizing EPI, the frequency of the phase encoding can be increased using a zero filling. The end result of this is an increase in resolution. On the other hand, TE can be increased so as to increase the transverse magnetization, thus giving a greater T2 and T2*. Moreover, a gradient with a relatively high performance can be used in optimising EPI (Ye et al, 1996, p.220). Bandwidth represents the frequency range resulting from the already read gradient across the field-of-view (FOV). This measure is quite imperative in the determination the

Introduction to mass communication Essay Example | Topics and Well Written Essays - 1000 words

Introduction to mass communication - Essay Example The editor is another gatekeeper who decided which parts of the original report were to be retained and which parts were to be changed or removed from the report. B) This report is targeted towards the world in general. This is a news item about politics, and it cannot be denied that everybody who is even slightly conscious of the world around him must have at least some interest in politics, for, as Aristotle said, "Man is a political animal." This report is about one of the greatest incidents in world politics in the year 2009, and is targeted towards anybody who has an interest in politics, anybody who is literate and aware of the political situations in the world. CNN is one of the world's leading journalism media, and their reports are generally believed to be authentic and trustworthy; a lot of people depend on CNN for comprehensive reporting of different events. It is not possible for everybody to be present everywhere every time; and although television has made communication easier, the utility of print journalism remains. This report is targeted to all those people who were interested in Obama's swearing-in and wanted a first-hand account of the proceedings at the inauguration of USA's 44th President and the first Black President in the history of the country. C) This report describes the inauguration of Barack Obama as President of t... The United States is considered the most powerful country in the world. This greatness that America has achieved was not a given; according to Obama, "it must be earned". America has earned its greatness, and although it faces serious economic and international challenges, it has not ceased to be great. Obama showed his countrymen a ray of hope in saying that the challenges faced by USA will be met, although that may not be easy or quick. Joe Biden was sworn in as Vice-President before Barack Obama took his oath of office with his hand on the same Bible that was used in Abraham Lincoln's first inauguration. Obama took note of the fact that he was Black, and thanked those who sacrificed so much so that "a man whose father, less than 60 years ago, might not have been served at a local restaurant can now stand before you to take a most sacred oath." He promised to end petty squabbles on Capitol Hill, bring "old friends and former enemies" into the fold. He also vowed to leave Iraq to its people and to finish forging "a hard-earned peace" in Afghanistan. To Muslims, he promised "a new way forward, based on mutual interest," and to terrorists, he said, "You cannot outlast us, and we will defeat you." The report also shows what the reaction of people across America and the world were. While spectators at the National Mall were overwhelmed by Obama's speech, across the country, people gathered together to watch Obama deliver words of hope on television. Even the reactions of celebrities like Oprah Winfrey are documented in this report. It also mentions that world leaders like Nicholas Sarkozy, the French President, and Australian Prime Minister Kevin Rudd congratulated the new President on