Human Lymphocytes Exposed to Co Irradiations and I Decays

Human Lymphocytes Exposed to Co Irradiations and I Decays Chapter 1: Introduction 1.1. Microdosimetry Problem statement Nuclear medicine and molecular imaging use unsealed radionuclides for diagnostic or therapeutic purposes. In targeted radiotherapy, the aim is to address tumor cells using suitable radiopharmaceuticals and achieve a high dose deposition inside the target structures. â€Å"Macrodosimetry† generally entails estimating the dose effect in organs (or dimensions of at least some millimeters) and is outlined in detail by the Medical Internal Dose (MIRD) Committee, the U.S. Society of Nuclear Medicine and the International Commission of Radiological Protection (ICRP) [1]. Microdosimetry therefore entails estimating the dose absorbed in microscopic objects such as cells. Dose deposition in cells can originate from extracellular media, intracellular uptake in a single cell and from surrounding cells. As an alternative to characteristic photon emissions,radionuclides decaying by electron capture or internal conversionmay undergo a process known as the Auger effect. In the Auger effect, an electron from an outer shell fills the lower electron vacancy, but the energy released in the process is transferred to another orbital electron. This electron is then emitted from the atom instead of a characteristic X-ray [2]. The emitted electron is called an Auger electron,with ranges in tissue typically at the micro- or nanometer level [3].Their unique property of depositing significant amounts of energy in minute volumes around the decay site opens up the possibility of using them as microscopic probes to study fundamental questions regarding the interaction of radiation with cells. 123I is used mainly in nuclear medicine because of its ideal ÃŽ ³-ray energy (159 keV) and relatively short half-life (13.2 h). The decay of 123I is, however, also associated with the production of Auger electrons. These low energy particles (4]. Knowledge of the absorbed dose is required for evaluation of the observed biological effects and to predict or compare the effectiveness of different radiation modalities. However, direct dose measurements in cells are impossible due to the small cellular dimensions [5]. According to the stochastic character of all of the decay processes, a large number of pathways exist by means of which a radioactive particle can decay and the excited atom can de-excite, i.e. each initial inner shell vacancy may cause a different number of Auger electrons to be emitted resulting in a more or less broad distribution of differently charged ions. Because these electron transitions and particle interactions are random processes, the Monte Carlo technique is an appropriate tool for the simulation of Auger emissions and electron spectra, as well as a feasible method to obtain correct absorbed dose values under consideration of all irradiation aspects like geometry and activity distributions [5],[6], [7]. Bingham et al. found that the dose delivered to the cell nucleus is underestimated by a factor of 7.4 for 123I in cells with nuclear radius of 4 ÃŽ ¼m and cell radius of 12 ÃŽ ¼m when compared to conventional electron dosimetry, indicating the need of developing dosimetr ic calculations for electrons emission at a cellular level [8]. Geant4 is an open source Monte Carlo (MC) toolkit, based on object orientated programming rules using the C++ language, which provides functions for simulating the passage of particles through matter [9]. The code is freely downloadable from the Geant4 web site. Detailed descriptions of the toolkit design and the physical fundamentals may be found in the â€Å"Geant4 User’s Guide for Application Developers† and the â€Å"Physics Reference Manual† [10], [11]. Besides the fact that it is entirely open-source and freely available to all users, the main advantage of this toolkit is its openness to modification and extensions. Originally Geant4 comes from high-energy physics but it also provides low-energy physics processes necessary for medical applications. Users may construct stand-alone applications or applications built upon another object-oriented framework. In either case the toolkit offers support from the initial problem definition to the production of results and graphics for publication. At the heart of Geant4 is an abundant set of physics models to handle the interactions of particles with matter across a very wide energy range. Data and expertise have been drawn from many sources around the world,and in this respect Geant4 acts as a repository which incorporates a large part of all that is known about particle interactions[12]. All aspects of the simulation process have been included in the toolkit: the geometry of the system, the materials involved,the fundamental particles of interest, the generation of primary events, the tracking of particles through materials and electromagnetic fields, t he physics processes governing particle interactions, the response of sensitive detector components, the generation of event data,the storage of events and tracks, the visualization of the detector and particle trajectories, and the capture and analysis of simulation data at different levels of detail and refinement. 1.2. Objectives Aims The level of biological effects of certain radiations is not always directly proportional to the dose they impart. Since the delivered dose on a cellular level is not directly measurable using current instrumentation, scientists and physicians have developed correlations between the biological response and the exposed dose through experiment and theory of atomic physics. An alternative method of predicting the delivered dose in a cell is by using Monte Carlo simulations. These simulations however, have to describe the biological composition and geometries of the material as accurately as possible, as well as the interactions of different particles with the material and can therefore result in complex codes and extremely long computation times. In our study, the aim was to determine (through experiments and using Monte Carlo simulations) the relative biological effectiveness[1] (RBE) of isolated and stimulated human lymphocytes exposed to 60Co irradiations and 123I decays. The first phase of experiments was the exposure of 3 different types of cellsto a 60Co-teletherapy unit. The proposed cell lines were: human lymphocytes, rat brain endothelial cells(bEND5, a cell with high radiosensitivity) andChinese hamster ovarian cells (CHO-K1, a cell with low radiosensitivity). The cells were exposed to graded doses of 60Co ÃŽ ³-radiation, after which they were cultured and the micronuclei formations in binucleated cells were used to analyze the effects of ÃŽ ³-radiation on the cell types. The second phase of experiments was the exposure of a known number of isolated and stimulatedhuman lymphocytes to certain activities of 123I for a discrete amount of time. The thymidine analogue 5-[123I]-iodo-2-deoxyuridine (123IUdR) was prepared and used to incorporate123I into theDNA of human lymphocytes. This was done such that the radionuclide could be transported across the cell and nuclear membrane to permit the deposition of Auger and Coster-Kronigelectrons in close proximity to cellular DNA. After exposure, the samples werecultured to express residual radiation damage. The cellular damage was quantified by numerating the micronuclei (MNi) frequency in binucleated (BN) cells.The experiments were done at iThemba LABS under the supervision and guidance of Prof. Slabbert and Philip Beukes. The experimental work followed the same approach as that of Slabbert, et al[13]. In the study they focused on the targeting and accumulation of 123I in human lymphocytes and CHO-K1 (a Chinese hamster ovary cell line). They found that the combined effect of intracellular and extracellular disintegrations of 123I is about 3.7 times more potent to lymphocytes compared to when the disintegration of the radionuclide is restricted to only the extracellular medium, among other results. It was concluded that this enhancement is due to the short range Auger electrons emitted by the isotope. Next, we wished to recreate the above experiments through Monte Carlo simulations and thereby determine as accurately as possible the absorbed energy and dose due to the irradiations,specifically the energy and dose deposited by Auger electrons produced during the decay of 123I. We will make use of a Monte Carlo based simulation code Geant4. The code must be mastered and used to simulate the scenarios mentioned above. We attempted to simulate the above 60Co exposures. This simulation was an investigation into the irradiation of a macroscopic volume by a radioactive source. The geometry was set up to replicate the experimental setup with regards to the source location and type, collimation, build-up and backscatter, the Petri dish and cellular media. The individual cells were not used as detectors, only the effective volume in the Petri dish. The energy and the dose deposited by the 60Co source (ÃŽ ³-rays, primary and secondary electrons) was then quantified by the Monte Carlo simulation. Our main endeavor was to simulate the energy deposition from the decay of 123I within a cell using Geant4. Basically, a geometry representing a biologicalcell (with the same density, etc. as the proposed lymphocytes) was created as a detector to measure the dose, energy and particles traversing it due to a radionuclide prone to emit Auger electrons, i.e. 123I. A similar simulation was performed by Bousis, et al (2012), using their in-house Monte Carlo code [14]. More advanced simulations are the calculation of DNA strand breaks due to direct and indirect effects of Auger electrons as was demonstrated by Raisali, et al (2013), which werehowever not attempted in this investigation [15], [16], [17]. Furthermore, an empirical formula relating the activity(and consequently the absorbed dose) to the biological response was determined. The curveswere compared to other dose-response curves from literature, thereby indicating if the simulations are a viable option for predicting accurate dose depositions. We could then calculate the RBE values from our dose-response curves and compare them to values available in literature. Finally, we aimed to determine the accuracy and feasibility of Geant4 as a simulation toolkit for medical and radiobiological purposes. To this end we considered the practicality, effort and time spent using Geant4, as well as by the comparison of RBE values and dose-response curves. Geant4 is an advanced, extensive and comprehensive simulation toolkit. Its advantage over similar packages with regards to availability, artistic and geometric freedom, physics models and materials libraries and openness to modification are undeniable. It is a very powerful simulation toolkit and can be used in a large number of areas of expertise as is shown by the examples supplied alongside the toolkit. [1]RBE values indicate the effectiveness of two radiation qualities to produce a certain biological response.

Private Tuition Essay

It is now fashionable for many Malaysian students to go for private tuition. In fact, most students feel insecure if they do not have extra tuition after school. Isn’t that correct? Extra tuition may be necessary for some of you. For example, some of you are weak in mathematics. Without help, you may be left behind. Many of you are in classes which are large. Your teacher cannot give special attention to weak students but your private tutors can. Some teachers may seem unapproachable. Timid students feel afraid to ask questions. They do not want to look stupid. In a small tuition group such students may feel confident. Tutors can also afford to be more patient and allow students to take their time. They do not have to worry about completing the syllabus. Not all teachers are experts in their subjects. Unfortunately, you cannot choose your teachers. On the other hand, you can shop around for good tutors recommended by friends. You can also change tutors whom you find unsatisfactory. However, not all tutors either. Nowadays new graduates join tuition centres while waiting for other jobs. They are not trained teachers. They leave when they find something better to do. They are not bothered about completing the syllabus before the resign, so be careful. In addition, tuition centre exist to make a profit. Classes are often large; there may be as many as 20 to a class. This means you pay for individual attention but do not get it. They have also been cases of tuition centres closing after having collected fees in advance. Finally, extra tuition takes up too much of a student’s time. A lot of time is wasted on travelling to and from the tuition centre. Some of you treat tuition classes as social gatherings. You can actually use your time more profitably on hobbies or personal revision. After attending tuition classes, you may be too tired to do your homework or your school work. If you pay attention in class and do your revision regularly there is no need for extra tuition. The money you would save could be used to buy revision books or put a side for furthering your education in the future. Personally I feel private tuition is a waste of hard-earned money.

Portfolio Assignment Essay

1. â€Å"The assets of the three richest people in the world match the combined annual GDP’s of the 48 poorest countries.† My personal opinion on this statement is most closely described by: a. Good for them – they worked hard to get their wealth b. The only problem I have with this is that this money is in their bank account and not in mine c. No problem with this – many of these people give huge amounts to charities d. I think that it is morally wrong for anyone to have that much money e. I think that active steps should be taken to correct such immoral wealth imbalances Choice now: A: Good for them – they worked hard to get their wealth Choice in assignment 1: B: The only problem I have with this is that this money is in their bank account and not mine. Notes: I changed my option because I was not well conversant with the word ‘sustainability’. I have learned that Sustainability is about what we must want to achieve. These people achieved by working hard. We must not be greed. They worked hard to achieve their desires. We all have to work hard if we need to be successful in life. I know that some will say that there should be fair distribution of wealth and allocation of resources among diverse members of the community (distributive justice). In reality, you cannot sit and do nothing, at the end of the month you expect to be paid like all others who worked so hard. What we have to do as a nation, we have to create a conducive environment for everyone by creating jobs, health care centers, ensure that all children are educated for the benefit of their future, by this we would be creating a better future. Inequality could not be detrimental to the interests of the poorest of the poor (Permissible inequality) ‘John Raws’. John Raws indicated that the poor do not get opportunity to go to proper schools or even better education so that their future can at least be bright, if we ensure that there is proper education, it would be a good foundation for the kids and these would reduce poverty and no one will complain about the salary or wealth of others. 2. â€Å"Unless fossil-fuel use slows dramatically, the earth’s average temperature could rise by six degrees Celsius in the next 100 years.† My personal opinion on this statement is most closely described by: a. Who cares? b. I don’t believe this climate change nonsense c. Six degrees will make winters much more bearable to me personally d. I’m a bit concerned about this, but there is nothing that I can do about it e. I’m a bit concerned about this, but why should I invest my personal time, effort or money in solving a general social problem. f. I think that individually we can and should strive to solve this problem for the greater good Choice now: Choice in assignment 1: F: I think that individually we can and should strive to solve this problem for the greater good. Notes: I’m still picking option ‘F’ because I have learned that when the temperature rises, there is a higher chance of diseases being transmitted through insects. One disease that was spread throughout the United States and Canada because of heat increase was the West Nile virus. Other animals such as rats might change their habitats in hot weather and can cause the spread of diseases. This is how the disease Hantavirus is transmitted. Heat waves can cause droughts. As a result, water levels decrease, lowering water quality and increasing the opportunity for disease transmission. Heat waves also increase health problems in humans. Average surface temperature will increase. Sea level will rise from melting ice around the world. This could be as much as a meter, or much more if melting accelerates or destabilizes major ice sheets (there is unexpected and recent evidence of Greenland and West Antarctica becoming destabilized.) Melting or destabilization of either could rai se sea level world-wide by 25 feet. Deaths will increase as a result of heat waves, drought, and flooding. We have to begin to strive to solve this problem now as it takes time to lower concentrations of greenhouse gases in the atmosphere, individual and collective action – communities, states, nations, businesses and government are needed. We have to learn about our â€Å"carbon† footprint and how to reduce it by wasting less energy and pushing for solutions that would reduce carbon emissions per unit of energy used. The less fossil fuel’s used the better. Sources: Heat Waves and Unusually Warm Weather. 8/10/05. Union of Concerned Science. 12/23/05. http://www.ucsusa.org/global_warming/science/early-warning-signs-of-global-warming-heat-waves.html Consequences of Global Warming. 1/3/06. Natural Defense Resource Council. 12/23/05. http://www.nrdc.org/globalWarming/fcons.asp 3. â€Å"If the present growth trends in world population, industrialization, pollution, food production, and resource depletion continue unchanged, the limits to growth on this planet will be reached sometime within the next one hundred years. The most probable result will be a rather sudden and uncontrollable decline in both population and industrial capacity.† My personal opinion on this statement is most closely described by: a. I don’t believe this tale of doom. b. Yes we are consuming natural resources too fast, but I don’t think this is a problem as there is plenty of time to find technological solutions to problems that emerge c. Yes we are consuming natural resources too fast. The first priority in solving this is to put the brakes on human population growth. d. Yes we are consuming natural resources too fast. The first priority in solving this is for rich people to reduce their consumption significantly. e. Yes we are consuming natural resources too fast. And frankly I don’t see any solution because increasing consumption is the basis of our economic growth. Choice now: Choice in assignment 1: B: ‘Yes we are consuming natural resources too fast, but I do not think this is a problem as there is plenty of time to find technological solution to problems that emerge. Notes: I still chose option ‘B’ because I think as a human race we are up to the challenge. We have capable scientists who will come up with a solution to this problem. I think that a better world is possible, and that the acceptance of physical limits is the first step toward getting there. 4. â€Å"If arctic ice melting continues, we are likely to see the loss of two thirds of the world’s polar bear population within 50 years.† My personal opinion on this statement is most closely described by: a. Who cares? b. If it boils down choosing between driving a luxury SUV and worrying about  polar bears I’ll take the car any day. c. While this is sad, polar bears aren’t really very important to my personal welfare which is my primary concern. d. While this is sad, polar bears aren’t really very important to general human social welfare. e. I don’t think polar bears are all that important to human welfare. However, their plight is a symptom of climate change which is a big problem to future human welfare. f. I think this it is morally unacceptable for humans to put their interests ahead of the rights of other species like polar bears. Choice now: C: While this is sad, polar bears aren’t really very important to my personal welfare which is my primary concern’. Choice in assignment 1: F: I think this is morally unacceptable for humans to put their interests ahead of the rights of other species like polar bears. Notes: I don’t have to worry about Polar bears because they live In the Arctic in areas where they can hunt seals at openings in the sea ice called leads. There are five nations with polar bears: U.S. (Alaska), Canada, Russia, Greenland, and Norway. So, I really don’t think it is necessary for me

Media Influence Political System On The United States

Media influence Political System Media has influence the political system many different ways in the United States. Talking about politics, it is very complicated because there are so many public opinions. Not knowing which candidate is lying or passing a bill and not knowing what is on it. Because most Americans own a smartphone, social media is so enormous and having access to almost anything. While Americans are on the internet, watching television, and listening to the radio or even reading the newspaper, at some point the word politics comes around and we have our own public opinions. On the internet, when the politics news come around, people put their own opinion about campaigns, government and activism. Statistics show, that â€Å"66% of social media users (39% of American adults) have engaged in one of eight civic or political activities with social media: 38% of those who use social networking sites (SNS) or Twitter â€Å"like† or promote material related to politics or social issues that others have posted, 35% have used social networking sites to encourage people to vote, 34% have used the tools to post their own thoughts or comments on political and social issues, 33% have used the tools to repost content related to political or social issues that was originally posted by someone else, 31% have used the tools to encourage other people to take action on a political or social issue, 28% have used the tools to post links to political stories or articles for others to read,Show MoreRelatedUnderstanding the Convergence of Media Systems and Political Com munication in the U.S. and Western Europe1054 Words   |  5 Pagesthe Convergence of Media Systems and Political Communication in the U.S. and Western Europe A powerful trend is clearly underway in the direction of greater similarity in the way the public sphere is structured across the world. 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