Personal Soundtrack Essay

You're goanna miss this Word of God Speak Cartoon Song Friends Good Morning He Said Where were you when the world stopped turning Outline She's got it all My Life: In a Nutshell exactly we want to be in 5, 10, or even 20 years. However, most of the time, those 5,10, and 20 year plans do not work out as we expected.We go through triumphs and tragedies; we grow and learn; and we eventually realize that what we have planned s probably going to change because we have changed. Over the course of my life, I have changed in a variety of ways and have overcame a number of challenges. Vive made plans for my life and most of them did not work out, but looking back, I wouldn't change a thing. As a young child going through elementary school, I had a similar life to most of my friends. I spent most of my time at daycare, church, or with my family.I loved playing sports, watching TV and movies, and going to school. I remember going to church twice a week, for Sunday services and Wednesday night p rograms. I loved the music at church, whether it was in Sunday school, holiday programs or Just regular church worship. Some of my favorite songs growing up were Veggie Tales' Hairbrush Song (94-95), and Away in the Manger (96-97). I'd sing these songs with my family, my friends, or even by myself because I loved to sing. At school, I didn't always fit in.I didn't wear name brand clothes or pretty dresses, ND I didn't have the popular school supplies or toys. However, like most kids, I always wanted to fit in. I was good at sports, so I was often one of the first picked at recess for kickball. I also did what I could to learn who the popular music artists were and what songs they sang. One of the songs I learned to help fit it was Bye, Bye, Bye by NCSC (98-99). My parents didn't like us listening to pop music, but learning this song helped me feel like I somewhat fit in at school.

Decision making Essay

The first skill set is learning how to use the four primary ethical perspectives that are used in decision making. These perspectives are called the Four Ethical Lenses. The second skill is learning to use a practical and repeatable decision-making method called the Baird Decision Model. As we become adults, one of our primary responsibilities is to decide what values and ethical priorities are the most important to us. The ethical game simulation assist with that. Mysterious Blogger and Unveiled I. D. The ethical issues that were addressed in these simulations were religion and violation of company policies. In the mysterious blogger simulation an employee hacked another employee’s personal PC only to find that the other employee was blogging about the company. Which was in violation of the company’s policy. In the unveiled I. D simulation an employee, which is a woman has issues taking a photo for an ID because it is against her religion to show her face unless amongst other women only. The decisions making steps I took to resolve these dilemmas was the being reasonable lens trying to consider what is good, fair, true, and virtuous. I also used the responsible lens trying to make an ethical choice based on my analysis. The ethical perspectives that influenced my decision making was Being Attentive: Collect the facts and notice what’s being said. Being Intelligent: Find the underlying issue and determine who’s really involved. Being Reasonable: Use the lenses to consider what is good, what is true, what is fair, and what is virtuous. Being Responsible: Make an ethical choice based on your analysis. Being Reflective: Defend your choice with careful thought and observe the aftermath closely. The way these ethical perspectives influenced my decisions was through personal and community values. Trying to understand and asses the situations, while also being fair and unbiased, so that all can feel addressed and handled in the correct manner. The way concepts from the simulation relate to the workplace is very simple and straight forward. The concepts helps one to understand the situation by analyzing and placing it in a particular lens. By doing this one has a better grasp on how to handle and resolve the issues that may take place. When in the workplace there are different races, genders and religions and these simulations touch base on in-depth issues that has definitely arose in the business environment. Having a clear process in place for evaluating exceptions ensures that all are treated equally, including the least advantaged. Conclusion With time and practice, the conflicts inherent in moral dilemmas can become opportunities for developing your ethical self. When you come across difference, remember that we all have our chosen lens. â€Å"Arguments over the â€Å"right thing to do† often stem from differing definitions of what actions are ethical† (ethicsgame. 2013). Knowing your ethical lens and how it effects ones decision making only enhances an individual’s work ethic, morals and decision making in one’s personal life.

Catch

Heller’s novel was able to become so popular because readers use the characters as a comparison of how patriotism should be, and the attitudes of the soldiers during World War II illustrates how idealism needs to change. The attitudes of characters in Catch 22 are far from our normal perception of patriotic. For example, the main character, Yossarian fakes injuries in order to stay the in hospital, because he does not want to risk his life in battle. He complains saying things such as â€Å"I think it’s my appendix bothering me† (Heller 176) and â€Å" then I’ll just go back to the hospital† when he is soon to encounter another battle. Yossarian is so unpatriotic that he even â€Å" goes absent without official leave from Milo† (Heller 405). Many characters in Heller’s novel simply have no motivation to serve and protect their country. One soldier states, â€Å" there’s no patriotism, that’s what it is. And no matriotism, either† (Heller 123). Compared to the time period in which the novel was written, this mind set is unacceptable. Yossarian has such a negative attitude, it is even stated â€Å"morale was deteriorating and it was all Yossarian’s fault However, there are characters in the story that are used as comparison to Yossarian, and show the level of morality people would have expected during the time period in which the novel was published. Appleby is one of these soldiers, who seems to be the perfect soldier. He follows regulations without question and does everything he is supposed to do, managing to succeed with minimal effort at whatever he does. It is stated that â€Å"Appleby is a symbol of American Virtue† (Heller 18) Texan is also another comparison character. Texan is up beat, excited, and full of energy. He is proud to be serving his great nation. Heller writes, â€Å" Texan turned out to be good-natured, generous, and likable. In three days no one could stand him. † (Heller 9) This statement clearly explains the behavior of most soldiers in the novel. The importance of these characters is to portray to the reader how soldiers should have acted, and also provide evidence for the rise in levels of idealism and patriotism during this time period. It is easy to tell by the soldiers in Catch 22 that attitudes needed to change. The presidency of John F.

West High School in Denver, Colorado Essay Example | Topics and Well Written Essays - 1000 words

West High School in Denver, Colorado - Essay Example West High School or New Denver West High School Home of the Cowboys was pioneered by Owen J. Goldrick. His school opened in 1859 in a log cabin with 13 students. West High School was organized in 1883 and in January, 1884 moved to Colfax Ave.West High School in Denver, Colorado Abstract â€Å"We turn dreams into futures.† This is the motto of the Denver High School, the topic of my research. I went to Denver West High School and examined the school’s environment, teachers, students, and academic and extra-curricular flow of activities. I went to Mr. Jorge Loera, principal Denver West High School and asked permission to visit and observed at least three classes to feature in my essay. Mr. Loera gave me the class of Ms. Anderson, Mr. Clymo, and Ms. Headrick. West Denver High School was described in general and in three specific classes. The feature includes Denver West High School’s history, academic programs, the qualities of the teachers’ selected and clas s interaction, and the students’ viewpoint. The teacher-parent-students’ relationship were also discussed as West Denver High School includes parents in the child’s learning. Brief History West High School or New Denver West High School Home of the Cowboys was pioneered by Owen J. Goldrick. His school opened in 1859 in a log cabin with 13 students. West High School was organized in 1883 and in January, 1884 moved to a wonderful new building on Colfax Ave. and Mariposa St. called the Franklin School. For years, the name of Franklin School and West High School were synonymous. On June 13, 1884, at 2:00PM, Charles McDonough, Effie Hallam, Lelia Williams, Frances Brandt, Laura Duccy, and Morrison Stillwell became the first graduates of West High School. On a cold January morning in 1926, 1000 students and teachers said "goodbye" to their school of 33 years and marched from 5th and Fox to the new West High School at 9th and Elati. After 83 years, it is still the Home of the Cowboys. The Academic Program Denver’s West High School serves grades 9-12 in the Denver Country 1 School District. The school is dedicated to the academic success of the student. West High School creates partnership with parents in building the character and academic performance of the students. Math, Language Arts, Science, Social Studies, World Languages, Fine Arts, Music, Physical Education, and Career Technical Education are the subjects being taught in Denver West High School. The only teachers in Career Technical Education are Mr. Clayton, Ms. Pegues, and Mr. Mascarenas. Math subject focuses on Algebra, Geometry, Probability and Statistics, and Pre-calculus. English program entails American Hispanic, British, and World Literature, and College Preparation Reading and Writing. Science covers the topic related to Advance Placement Biology, Chemistry, Earth Science, and Physics. Social studies include topics such as Advance Placement Government and United States Hi story, Civics, Psychology, Geography, Hispanic History and Student Council. World Languages that are being taught by teachers are German, French, and Spanish. Fine Arts offered activities related to Band, Computer Arts, Video/Film Production, Chorus, Dance, Photography, Ceramics/Sculpture, Drawing/Painting, and Theater/Drama. Academic Calendar Plan for Music, Physical Education, and Career Technical Education are not yet available so related subjects/topics under this academic program were not yet posted. The extra-curricular activity that this school is best known for is Radio/Video/Multimedia. Extra-curricular activities are heavily encouraged by the school and most of the students are involved in the activity. West High School also offers programs for children with learning differences or disabilities. The administration, as well as the teachers makes sure that every student are aware of the academic program and calendar to inform the students and the parents about the subjects b eing taught everyday in the class. Based on GreatSchool’s Rating Criteria, Denver High School has 1 out of 10 rating criteria. The GreatSchool rating criteria is based on the comparison of test results in different states. The school also has an average Community Rating of 3 out of 5 stars, based on reviews from 20 school community members. The Teachers There is 1

Sexual Harassment & Organizational Behavior Essay

Sexual Harassment & Organizational Behavior - Essay Example A culture within an organization is developed that will determine its leadership methods, communication channels and group dynamics within a teamwork frame work through the formation of well structured elements. Creation of these elements depends on the organizational setting and the people involved in day to day running of the company. These people include; watchmen, secretaries, salesmen, supervisors, managers, firm owners, directors among others. All of them form the organizational structure and its behavior depends on their individual behaviors. The basis of this model is that it provides power and authority to the organizations’ management to punish errant members of its organization. Employees are inclined towards obedience and looking unto the boss for advice and direction. Any unwelcome conduct or contact that touches on sexual privacy is sexual harassment.3 It affects both men and women although the latter are frequent victims. The following are incidences considered to be sexual harassment. Not every employee in the organization smokes or rather take cigarette in their daily life as a form of pleasure. Smoking as is widely known is harmful to not only the healthy of the smoker but also the person inhaling the smoke from the cigarette. Honesty is very important in an organization not only to the managers but also to individual relationships. Cheating downgrades an individual’s character, integrity and the organizational performance. This group of people are demeaning and demanding in nature. They are not tactful in nature but they mean to offend anyone. They don’t give out important assignments but they earn respect and trust from the rest of the members. They normally have problems with rules, schedules and work hours. In most cases this group of people lose tract of what is going on with the organizations and they are likely to miss details of important duties.

Poetic Analysis Essay Example | Topics and Well Written Essays - 1250 words

Poetic Analysis - Essay Example And, there is a proportion among poets who bring these situations and incidents into a written form, using the realistic or fictionalized version of the real life happenings as the base. Beautifulness and tragedy in poem comes out in the words that are used, objects that are handled, concepts that are discussed, etc. Likewise, the English poets, Felicia Hemans and Lord Byron have penned poems bordering on both beautifulness and tragedy, particularly about human relationships influenced by the events they knew. So, this paper will contrast and compare the treatment of relations between men and women in Hemans’ â€Å"Indian Womans Death Song" and Byron’s â€Å"Don Juan†. Felicia Dorothea Hemans is the 19th century English poet, who wrote a lot of poems basing most of them on the travails of women. In her works, she brought out the different problems faced by the women of those times, both in their personal fronts and from the society. So, most of her works bordered on sentiments, with â€Å"Casabianca,† being the well known one. In her other famous work, â€Å"Indian Woman’s Death Song†, Hemans again focused on the tragic problems faced by a married Indian woman due to the extra martial relationship of her husband. Driven to despair because of husband’s abandonment, the woman with her child takes a deadly ride in a canoe down the Mississippi river. While rowing the canoe only, she sings a mournful death song. The death song gets overpowered by the river’s sound, as she gets drowned in the raising water. On the other hand, George Gordon Byron, the English poet, focused on the travails of a male protagonist. Lord Byr on in his poem â€Å"Don Juan† discusses the legend of Don Juan, but with a slightly different perspective. That is, he portrays Don Juan not as the stereotypical womaniser but as a gullible person, who can be easily seduced by women. That

WOMEN AND LAW Oral presentation Essay Example | Topics and Well Written Essays - 2500 words

WOMEN AND LAW Oral presentation - Essay Example wever, section 1(1) of the Street Offences Act, 1959 (as amended by Sexual Offences Act 2003, section 56, schedule 1, paragraph 2) states that â€Å"it shall be an offence for a common prostitute whether male or female to loiter or solicit in a street or public place for the purpose of prostitution†. To understand whether Topaz’s activities qualify as an offence under Section 1(1) of the Street Offences Act, 1959 it is first essential to analyse whether Topaz qualifies as a â€Å"common prostitute†. The term â€Å"common prostitute† has not been defined by statute though it has been part of statute law since 1824. The term â€Å"common† was criticised during the debates on the Street Offences Bill, which became the Street Offences Act 1959. The Criminal Law Revision Committee Working Paper on â€Å"Offences relating to Prostitution and allied offences† published in December 1982 stated, inter alia, â€Å"the word ‘common’ should be removed from the expression, ‘common prostitute’†. In R. v. De Munck (1918) 82 J.P.160 CCA, the Court held that, â€Å"the term ‘common prostitute’ is not limited so as to mean only one who permits acts of lewdness with all and sundry, or with such as have her, when such acts are in the nature of ordinary sexual connection. We are of the opinion that prostitution is proved if it is shown that a woman offers her body commonly for lewdness for payment in return.† The decision was cited with approval by the same court in R. v. Webb [1964] 1 QB 357 where the proprietor of a massage establishment was found guilty of procuring and attempting to procure masseuses to become common prostitutes. The court followed De Munck and dismissed a contention that the definition should be confined to cases where a woman takes a passive rather than an active role in the lewd activities. In R. v. Morris-Lowe [1985] 1 ALL.E.R. 400, the court held that a â€Å"common prostitute was any woman who offered herself commonly for lewdness for reward. The

What is a Mahdaviat Term Paper Example | Topics and Well Written Essays - 500 words

What is a Mahdaviat - Term Paper Example The Mahdaviats believe in the Mahdi. They believe that he is Islam’s primary expected savior. They believe that they are th descendants of Muhammad. They believe that the Mahdi shall be known after a time of pain and suffering in the world. They also believe that the Mahdi will bring about justice in the world. They believe that the Mahdi will be the leader of a revolution which will bring about the new world order. Nations that oppose the Mahdi will go to war against the Mahdi. They also believe that the Mahdi shall instigate a seven year peace treaty with a Jew of a priest lieneage. The Mahdaviats believe that ISLAM shall be the only religion on earth when the Mahdi is around. They also believe that the Mahdi shall rule for even years with Jerusalem as his centre. They also believe that Israel shall be conquered. Who is the Mahdi? The Mahdi in Arabic means the rightly guided one. He is a major figure in Islamic eschatology. He is the one who shall restore justice and religion and shall rule before the earth ends. The Mahdi concept began on the inception of Islam and is popularly identified with the Shiite branch. The Mahdi shall come to save the Mahdaviats. He will show up in Mecca and shall travel from Mecca to Kufa in Iraq. At the time of showing up, he shall be forty years old. He shall wear a ring that belonged to King Solomon. The Mahdi shall fulr for a period of seven years. He is a descendant of Muhammed. Finally, the Mahdi is a person who shall conquer his enemies will be led by the one – eyed antichrist.

Motion Sensors Research Paper Example | Topics and Well Written Essays - 2500 words

Motion Sensors - Research Paper Example Applications of this content distribution network are outlined, followed by a list of the benefits that are associated with use of this system, both on a performance perspective and on a business perspective. Every system has some flaws, and in light of this, the limitations of the system are also discussed. Finally, there is a discussion on the reasons for the success of the system, with an emphasis on the steps taken to improve the performance of the system and the business strategies that are employed to attract and maintain clients. This report aims to analyze the successful implementation of a database system by a major corporation. In this report, focus will be on the Akamai Content Distribution Network. It outlines how the system works, its uses, limitations, costs and profits. Finally, the business approaches used by the corporation responsible for the database system are discussed. Akamai Technologies is a company located in Massachusetts, United States of America. It provides cloud services such as content delivery, web performance solutions, cloud security services and cloud networking connectivity. The company was founded in 1998 by Dr. Tom Leighton, Daniel Lewin, Jonathan Seelig and Randall Kaplan (Akamai.com, 2015). Some of its clients include Facebook, Twitter, Yahoo! and Bing. Development of the company was motivated by a need to solve internet congestion problems which were common at the time. Creating a team of researchers, Dr. Leighton and Mr. Lewin managed to develop mathematical algorithms that could perform intelligent routing and replication of content over a large network of distributed servers. The founders obtained an MIT license for certain intellectual property and they started development in 1998. On April 1999, Akamai Technologies started offering commercial services (Akamai.com, 2015). Most of the company’s early employees were students at Massachusetts Institute of Technology (MIT). A

Facilitating the interview process Essay Example for Free

Facilitating the interview process Essay In this essay I will evaluate each document from Harrow College Application Pack, it will include information that applicants will need to know before they applied for the job. Inside the pack, it includes welcome letter from the principal, the curriculum of Harrow College, Organization chart, policy statement, travel policy, how to fill in an application form, job description, and person specification. In the application pack, a welcome letter from the principal of Harrow College will help recruitment because the letter is written by the principal it will set the standard and it attracts applicants and also it will make a good impression to applicants knowing the principal welcoming them to apply to Harrow College even though the principal is not saying it in person but it will make the applicant more welcoming and comfortable with the College. Secondly, the letter said â€Å"Harrow College now ranks as the top FE College in West London and Hertfordshire†, this will make applicants be more interested about the job role because they want to be part of Harrow College success and want to be part of that reputation. Harrow College can improve their welcoming letter by making the applicant feel more welcoming, instead of the principal saying thank you to applicant for applying, the principal should also include staff in Harrow College, that way applicants will feel the support of everyone in Harrow College. The letter also should include some background information of Harrow College and what kind of achievements Harrow College had to attract applicants. I think the letter from the principal is important because it will show a good sign that the college is welcoming and tells the applicant small information about Harrow College. The curriculum letter will help recruitment because it shows what subjects are majored in Harrow College; it will give a chance for applicants to see what other subjects they can apply for if in the future Harrow College have any vacancies. In the curriculum letter, it has background information about Harrow it will benefit the applicant because if the applicant doesn’t live local, they can find out about Harrow area. The organization chart will help recruitment because it will help applicants know who does what and who to report to, it shows Harrow College that they are a well-organized college, also it will allow the applicant to know there are people in different department doing different task. This document also helps me when I was recruiting in John Lewis because by knowing who is the CEO of the company and who is my manager in the organisation chart, it will help me in the future that if I have any problem I know who to report to. The equality and diversity policy statement will help recruitment because it will encourage applicants with different background to apply for the role, it will give a good impression to applicants that Harrow College don’t care where the applicants are from. Harrow College can improve their equality letter by showing figures of different background of staff in Harrow College because even though the letter tells applicants they accept anyone no matter where they from but some applicants would like to see the figures of different race and sex to know Harrow College is committed to equality and diversity. How to fill in an application form will help recruitment because is a step by step instructions of filling in an application form for applicants, that way applicants wouldn’t make any mistake or miss a section out, it will benefit for Harrow College because if the applicant make a mistake in the application form, employers from Harrow College can straight away not read the rest of the application form because employers might think if the applicant can’t follow simple instructions from the application pack then they can’t follow instructions when they are employed. Job description will help in recruitment because it sets out the main purpose of the job; it shows where the job is fitted in the organization structure, and the main responsible of the job and the type of task they will need to perform, putting the right information on job description is important because if Harrow College didn’t include detailed information on teaching and related activities and general duties, then when they have recruited the applicant, the applicant might not have any experience as a lecturer, they might not be flexible e.g.: travelling to two Harrow College Campuses, to act as a personal tutor to students. If those details weren’t included in job description, then the college would be hiring someone who have no qualifications and experience and that will cause Harrow College time and money because they would have to train the applicant or hire someone again. The changes that I would make is to improve their job description is to include how many hours the applicant will need to work, is important to put that information in the job description because applicant would want to know how many hours they need to work furthermore some applicant might have a family that they need to look after or pick up their children so if Harrow College would want the applicant work long hours during the week then some applicant can’t apply because of their personal problem. Person specification will help in recruitment because it gives information to the applicant what qualifications and experience is needed if they want to apply for the job, also Harrow College has designed well information of person specification, it included a lot if skills, different qualifications, and it specify on equality and diversity because selecting the right business lecturer is important for Harrow College, if they hire someone who hasn’t got any experience or the right qualifications then the lecturer won’t be teaching right to the students then it would mean Harrow College have to waste money again to recruit another lecturer again in addition to students would fail their exam which will cause Harrow College success’s rate to drop. The changes I would make to prove their person specification is to include the location of the job the reason for that is because applicant might want to know which campuses they will be teaching in and by putting the location applicant can decide whether they want to apply because if Harrow College would want the applicant to work in both campuses then applicant can’t apply because they might not want to travel to two campuses. Also Harrow College can include another column in the person specification e.g.: essential and desirable the reason for putting another column is because in the person specification it tells the applicant what skills are needed and what Harrow College is looking for but if they made it clear by putting skills into two column then it would made it more clear and organize for the applicant. The advantage of Harrow College using their own application forms instead accepting CV because in an application form Harrow College can set as many question as they like and what type of questions they would to like to know from the applicant also they have set a limited space in the form so they would expect applicant to write only important information instead of applicant writing unnecessary information in there which will make employers not bothered to read the rest of the application form because it will make employers feel that applicants didn’t follow the instructions by reading the questions and putting relevant answers in the form. Secondly, if Harrow College accept CV instead of application form, it will waste a lot of time and money for employers to read and compare each CV instead employers can use that time to do other things e.g.: mark students work and teach furthermore because each CV have different layouts with different information it will make employers much more harder to choose the right candidate that will be suitable for the job. Thirdly, employers can already tell if the applicants is a organize person or not by their writing and also their grammar, if the applicant grammar is poor which shows a really bad impression to the employers because the job role is lecturer and if their grammar is poor that will make employers in Harrow College consider that they can’t teach properly and if they hire that applicant then the applicant wouldn’t mark the student’s work properly. In my opinion, every document in the application pack is important. If one document is missing in the application pack, the company won’t hire the right applicant but overall I think the most important document is job advert and person specification because without job advert, no one would know about the job, applicant wouldn’t know how to apply for the job and what the job is about, also job adverts are very expensive whether the business is small or big. At the end of the day, the businesses still need to pay. Often job adverts are in short detail but the advert highlights the knowledge, skills and experience that each individuals are require within each advert. Job adverts would never change because of the job role because it would always tells the summary of the job, the location and how to apply so it wouldn’t make any difference with any job role but whereas person specification with different job role it would include different information depending how important the job role is e.g.: in the application pack, Harrow College is hiring Business Lecturer, therefore person specification would have a lot of information that they would require from a applicant but if Harrow College want to recruit a reprographics assistant, the person specification wouldn’t have much responsibilities as a business lecturer so when applicant read the person specification it won’t have a lot of requirements as the business lecturer person specification.

Uniformity of gamma camera images

Uniformity of gamma camera images Introduction In 1958, Hal Anger developed the first ?- camera and forever changed the area of nuclear medical imaging. Angers camera (also known as scintillation camera or gamma camera) used a 6 mm thick scintillation crystal (NaI) coupled to seven photomultiplier tubes (PMTs), each 3.5 cm diameter, arranged in a hexagonal shape. The crystal was used to convert the gamma rays into scintillation photos which would then be converted into electrical signals by the PMTs. The output of the PMTs in Angers camera was analogue and represented continuous values of gamma ray energy and the position of the event. The camera had a collimator mounted in front of the sodium iodine crystal, which was used to stop scattered gamma rays and essentially form the image. In the initial design of the gamma camera all the circuits were analogue and the camera is still known as an analogue camera. The images were displayed in cathode ray tubes (CRTs) or they were imprinted onto photographic films which were used as hard copies.   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Later on, with the development of electronics and computer technology, the analogue output of the photomultiplier tubes would be fed into a digital computer which would process the signals to form the clinical image. In order to achieve that, analogue to digital converters (ADCs) were incorporated into Angers design which would digitize the signals before feeding it to the processing unit. Gradually all the major electrical components of the gamma camera were replaced by digital electronics and in modern cameras the signals are digitized by ADCs installed individually in every PMT. The complete digitization of the gamma camera allowed for significant improvements of the prototype gamma camera. With the increased processing power available, modern gamma cameras can nowadays image at high count rates, can store digital images and display them directly onto computer screens. Furthermore, they can implement a range of corrections which have drastically imp roved the quality of the modern clinical images. Our objective in this essay is to describe the factors that affect the uniformity of gamma camera images, the technological advancements that have improved the cameras imaging quality and capability as well as the methods that are currently used to assess and correct a ? cameras uniformity. The basic components of a gamma camera and their function The general principles behind the function of a gamma camera are rather simple to understand. So, before we proceed onto discussing the uniformity of a ?-camera, we ought to mention its basic components and their function since they can affect image uniformity. The main components of a gamma camera are described below. The gantry of the gamma camera provides mechanical support to the detector head. The scintillation crystal [usually NaI (TI)], is maybe the most important component of gamma camera. Its function is to convert the incident gamma rays, originating from the patient, into scintillation photons. Between the crystal and the photomultiplier tubes, a transparent light guide is put in place to maximize the optical transmission of light from the crystal to the PMTs. Once the scintillation photons reach the photocathodes of the PMTs, they get converted into photoelectrons. The photoelectrons then, go through an amplification stage where their number is multiplied by a series of dynodes. Finally the electrons hit the PMTs anode and we get the output voltage that represents our signal. The photomultiplier tubes are connected to the pulse arithmetic circuits where the position and the energy of each event are determined. In addition, at the PMT output, gamma cameras incorporate a pulse height analyzer that determines which events get accepted based on their energy. This mechanism is put in place in an effort to reject signals arising from scattered photons that have managed to penetrate the collimator. The pulse height analyzer is also known as the energy window. The energy window is usually set to accept events with energies ranging from -10% to +10% of the peak energy. For example, when imaging with 99mTc (? emitter, 140 KeV, T1/2 = 6 h) the energ y window is set between 126 KeV and 154 KeV. The final component of the detector head of the gamma camera is the collimator. It is a lead plate with a large number of holes which is placed in front of the scintillation crystal. The main function of this component is to control which of the gamma rays pass through to the crystal and which ones are stopped. Gamma rays that travel parallel to the collimators holes (perpendicular to the crystal) are allowed through while oblique rays are attenuated. The role of the collimator is essential because it provides the PMTs with the ability to identify the location of each event and it stops scattered x-rays which spoil the contrast of the images. In addition, the collimator provides physical protection to the extremely sensitive and fragile scintillation crystal that lies beneath it. Camera Uniformity The term uniformity refers to the variations of intensity present in an image acquired using a uniform radioactive source. Factors that affect ? camera uniformity In the previous section of this essay we described briefly the function of the gamma camera. In reality however, things do not work perfectly. In fact there are numerous sources that can cause image imperfections and ruin the uniformity of our images. The most common sources and factors that affect image uniformity are: Collimator defects variations in hole size and angulation variations in septal thickness Crystal and light guide non uniformities in the crystals stopping power non uniformities in the number of scintillation photons emitted by the crystal non uniformities in the transmission of light through the light guide and the optical grease Photomultiplier Tubes variations in light collection efficiency with the events position in the crystal due to geometry variations in light collection efficiency with the depth of interaction in the crystal due to geometry variations in the quantum efficiency of the photocathode across the face of the photomultiplier tubes variations in PMT tuning gain differences between PMTs Count rate Energy of incident gamma rays To begin with, it is fairly obvious that a poorly constructed or damaged collimator will affect primarily the sensitivity of the gamma camera. The sensitivity variations arise from the fact that a defective collimator will attenuate gamma rays in a non uniform manner. That is to say, that the number of gamma rays which pass through the collimators holes will vary either due to differences in the septal thickness or due to differences in the angulation of the holes. So, the image will appear either hot or cold depending on the number of counts, thus ruining the uniformity of the image. The collimator, however, is not the only cause of imperfections. In an ideal world, the scintillation crystal would exhibit properties such as homogeneous stopping power, interaction with gamma rays only through photoelectric absorption, transparency towards scintillation photons and high conversion efficiency (gamma to scintillation photons). However, in reality, the crystal presents with variations in its stopping power which ultimately lead to sensitivity imperfections and the appearance of hot and cold spots on our images. As we mentioned above, this variation in counts is a manifestation of non uniformity. Furthermore, the scintillation crystals exhibit incongruities in their light output. This is attributed to variations in the doping of the crystal with the chemical which serves as the activation centre for the luminescence phenomenon. (In the NaI crystal the doping is performed using thallium). In addition real crystals exhibit non uniform transmission of light, in cases where the optical grease used to couple Crystal-PMTs is dried out, or if the crystal has been exposed to moisture in which case opacities (yellowing) are developed. Finally, non uniformities in the images also originate from variations in the fraction of light that the photomultipliers collect. Light is lost between the gaps of the PMTs array but also near the edges of each individual PMT due to reflection. The majority of scintillation photons are collected near the center of the PMT, where the collection efficiency is best. This causes the counts to appear as if they were pulled towards the centre of the PMT and results to non- linearities. Even, the smallest non linearities will result in large non uniformities in the images. Last but not least, we ought to mention non uniformities arising from variations in the function of the photomultiplier tubes. The photocathode of a PMT, in reality, does not convert photons into electrons uniformly. Its quantum efficiency is better near its center and deteriorates as we move toward the edges. In addition, different PMTs tend to exhibit slightly different gains which ultimately lead to non uniformities. For example, a PMT with a gain above/below the correct gain will result in fewer counts falling within the energy window, creating a cold area over the dysfunctional PMT. Drift in PMT gain is usually caused over time, due to ageing, exposure to magnetic fields (Earth, MRIs), temperature fluctuations or power supply instabilities. So far we have discussed how the function of the gamma camera components can affect uniformity in practice. For completeness, we ought to mention that gamma camera uniformity (specifically the intrinsic uniformity) can also be affected by other factors such as: the activity of the radionuclide used to image, the number of acquired counts, the source-camera distance and the source volume. According to Elkamhawy, Rothenbach, Damaraju and Badruddin the intrinsic uniformity of the gamma camera increases with the increase of the source activity. However the increase in activity must not exceed the count rate capabilities of the camera otherwise non uniformities may be caused. In addition, according to Elkamhawy et al., the intrinsic uniformity increases as the counts go up. This is something to be expected, considering the probabilistic nature of the phenomenon of radioactive decay. Poisson statistics teach us that as the counts become higher the relative standard deviation decreases. That is to say that the coefficient of variation is reduced as the number of counts goes up and the statistical noise decreases. Finally, there are reports of an inverse correlation between the source to camera distance and the intrinsic uniformity. As the distance increases the intrinsic uniformity is increased due to a more uniform attenuation of the gamma rays travelling towards the crystal. That is to say, when the source is close to the crystal the gamma rays have to travel longer to reach the edges of the crystal than the centre. (See figure 2). Therefore the gamma rays travelling towards B will suffer greater attenuation that gamma rays travelling to point A. This dif ference in attenuation will result in count differences thus increasing the intrinsic non uniformity. However, if we increase the source to crystal distance, the gamma rays will undergo more or less the same attenuation due to the inverse square law and the counts will be more uniform throughout the crystal. Developments in gamma camera technology that have contributed in uniformity improvements. In older, analogue gamma cameras, the only correction that could be performed was a sensitivity correction that dealt with sensitivity variations on the images. Following the technological developments, the high processing capabilities of modern microprocessors and the implementation of analog to digital converters into their design, modern gamma cameras have been equipped to deal with non uniformities through a series of corrections.   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Differences in photomultiplier gain used to be dealt with using the cosmetic approach which entailed the individual tuning of each PMT to match the other. Advances in microprocessors now allow for more advanced approaches. Maps containing the regional differences in pulse heights, as acquired from uniform flood sources, can be used to correct on an event to event basis (on the fly). As we mentioned earlier PMTs are affected by various external factors and they are caused to drift. Novel technologies have been introduced into gamma cameras which enables them to keep the gains stable in real time. For example, manufactures such as Toshiba, Elscint and IGE have implemented auto stabilization techniques where LEDs are used to tune the PMTs. The LEDs emit light which is detected by the tubes and the output voltage is then compared with a reference voltage and the gain is adjusted accordingly. With the increased processing power other corrections are current ly being used too. Linearity and energy corrections are common ways to improve the degree of uniformity in modern cameras. In the energy correction the most common practice is to expose the camera to a monochromatic gamma ray source (usually 99mTc) and acquire reading for the energy in various positions. Theoretically, the energy signal should remain constant independent of location on the crystal. However, as we have mentioned earlier there is always a small fraction of light which is lost. So, the readings are compared to the mean expected energy and a map of correction factors is stored in the gamma cameras memory which is used to rectify any errors in the energy signals. The linearity correction has a similar function. We would expect every events position coordinates to appear as a linear combination of the PMTs output voltages. , Y. But again due to light losses that is never true in practice. Fortunately, this is easily corrected through the linearity correction maps similar to those that we acquire for the energy correction. First of all, we remove the collimator and we introduce a lead plate with parallel holes throughout its extent. Then the system is exposed to a uniform point source. The image is processed and the positional errors are determined and stored as a separate correction map. The final correction to be applied on an image is the sensitivity correction, which has been used in the past as the only uniformity correction of analogue cameras. In modern cameras the technicians first stabilize the gains of the PMTs and then they proceed to apply the energy and linearity correction which have the greatest impact in the cameras uniformity. Then, and only then, they proceed with the sensitivity correction. The correction maps for the sensitivity are acquired by exposing the gamma camera (with the collimator mounted) to a uniform radioactive source. The counts are scaled up or down to eliminate any remaining cold or hot spots on the image. We should note that the individual correction maps should be acquired for each collimator since the sensitivity variations are primarily caused by collimator defects and other factors that we have already discussed. The scientific community has not stopped at the abovementioned corrections. Manufacturers and researchers have shifted their focus to new technologies hoping to replace components that contribute to bad uniformity but also to improve other gamma camera properties (resolution, count rate capability e.t.ch). For example, position sensitive photomultiplier tubes have been introduced (Hamamatsu, Photonis et. al.), which are capable of detecting the location of the event more accurately and efficiently that conventional PMTs. In addition to that, silicon photodiode arrays are being used coupled to the scintillation crystals for improved light sensitivity and quantum efficiency. Finally, there is a shift of interest towards replacing scintillation crystals with semiconducting materials. The combination of cadmium telluride with zinc makes for a great x ray and gamma ray detector. The main advantage of semiconductors over scintillation crystals is that the first converts photons directly in to electrical current. Contrary to the scintillation crystal that needs to use the photomultiplier tubes which are a significant source of non uniformities as we have mentioned. Quality Control: Measurement of non uniformity in gamma cameras Maintaining good uniformity in clinical images is extremely important. Even the smallest degree of non uniformity can cause artifacts which can prevent doctors from diagnosing the patient or lead them to the wrong diagnosis. The assessment of a gamma cameras uniformity is an integral part of its quality control and it is carried out in regular intervals (daily or weekly basis). These kind of investigations are carried out to ensure that there are no, non-uniform areas in the cameras field of view. The uniformity of a gamma camera can be measured either intrinsically or extrinsically. In the intrinsic setup, the collimator is removed and the naked crystal is exposed to a low activity uniform flood source. This setup has the advantage that the measurements are not affected by collimator induced non uniformities. In the extrinsic setup the system uniformity is assesses and the collimator is mounted onto the crystal. The advantage in this case is that the conditions of measurement are closer clinical parameters since in clinical acquisition the collimator is always in place. As far as the flood sources are concerned, 99mTc and 57Co are the most common choices. The technetium has the advantage of being readily available in hospitals and can be used as a mixture of radioactive material and water to create a uniform flood source. Also technetium is the most common radionuclide used in daily medical practices. Moreover, the presence of water presents a more realistic scatter source re sembling scattering conditions in patients. The main drawback of the technetium flood source is that it has a short half life and must be used soon after its creation. In addition, the construction method presents with the danger of spilling and contamination. An alternative to 99mTc is a 57Co source which has a convenient half life of 271 days. The peak energy of cobalt is close to that of technetium which is convenient in cases where the cameras performance is energy dependent. On the other hand, cobalt flood sources are quite costly and are usable only for about a year. Furthermore, cobalt sources often contain amounts of other cobalt isotopes Co60 and Co58 which emit higher energy gammas and may affect our measurements. A common testing protocol is the following. The radioactive source is placed at a distance approximately 4 times the field of view to ensure that the variation between the counts in the centre and the edge of the crystal is sufficiently small (as we have explained in figure 2) and can be ignored. The crystal is irradiated uniformly and a few million counts are acquired (approximately 1- 5 million counts). We need to acquire a statistically sufficient number of counts to ensure that the Poisson noise is minimal. We make sure that all the right corrections have been applied before we assess the images. A visual inspection of the images usually reveals gross deviations in performance. However, once the images have been acquired they are processed, using the cameras software, to yield values for common parameters such as the mean uniformity and the corrected uniformity which are used to quantify the quality of the camera. The mean uniformity informs us for the overall uniformity of the c amera throughout the FOV. The corrected uniformity is acquired by removing the Poisson noise from the mean uniformity. Those are not the only parameters that we can examine and other such as the integral uniformity and the differential uniformity are often assessed. Conclusion The uniformity of a gamma camera is maybe the most important parameter that expresses the quality of the cameras performance. Non uniform areas in the field of view can result in misdiagnosed patients and low quality of clinical services. Thus it is essential to perform regular checks to ensure optimal performance of the ? camera. Assessing the uniformity of a camera is not easy. As a parameter, uniformity is dependent on many factors and there are many things that can go wrong. Gamma cameras require regular testing, responsible operation and expert knowledge of its governing principles to make sure that its performance stays within clinically acceptable levels. References Professor Richard Lawson, The Gamma Camera , Lecture notes for the Nuclear Medicine Module of the University of Manchester MSc in Medical Physics, 2010. Peter F. Sharp, Howard G. Gemmell , Alison D. 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