As I grew up in an environment involved in medicine I became familiar with the importance of reading MRIs and bone scans as well as medical treatment through voluntary service in the nuclear medicine department at the Samsung Medical Center. I believe being able to read is so important in today's society, because we live in the era of rapidly increasing medical accidents. So I'm doing following in Health Science independent study:
1. Identify typical equipment used in medeical filed to diagnose cancer and other disease.
2. Learn about the mechanism of operation of the medical equipment especially, CT, MIR, and PET scane.
3. Discuss the principal of modern physics utilized in these apparatus.
4. Explore radioactivity, energy, and power.
One of popular health care products companies is Philips. They have been founded in Eindhoven, the Netherlands, since 1891. They began by making carbon-filament lamps which was one of the largest producer in Europ. In 1914, It established a research center to study physical and chemical phenomena and stimulate product innovation. In 1918, the company stated introducing a medical X-ray tube.
In 1925, Philips became involved in the first experiments in television in 1925 and, in 1927, began producing radios; by 1932, it had sold one million of them. A year later, it produced its 100-millionth radio valve and started production of medical X-ray equipment in the United States. By 1939, when it launched the first Philips electric shaver, the company employed 45,000 people worldwide. (Philips, 2008)
Tomography is derived from the Greek “tomos” means slice and “graphein” means write. It is imaging by sections or sectioning as well as it is formed by moving the X-ray source and detector during an exposure. A tomography of several sections of the body is known as polytomography. Different types of signal acquisition can be used in similar calculation algorithms in order to creat a tomographic image. These yield CT, SPECT, PET, MRI, ultrasonograpy, 3D TEM, and atom prob tomograms respectively. I've studied about CT, PET, and MRI. In United States, there are several Positron Emission Tomography Centers especially only one center in Minneapolis, Minnesota.
First, “Computed tomography (CT), was originally know as “EMI scan” as it was developed at a research branch of EMI, a company best know today for its music and recording business.” Now it is known as computed axial tomography (CAT or CT scan) and body section roentgenography. It is used to generate a three-dimensional image from a large series of two-dimensional X-ray images taken around a single axis of rotation (Brenner, & Hall, 2007).
Second, “Magnetic resonance imaging (MRI) is used in medical imagining visualizing the structure and function of the body in any place. Unlike CT it used no ionizing radiation.” The scanner creates a powerful magnetic field which aligns the magnetization of hydrogen atoms in the body. Radio waves are used to alter the alignment of this magnetization. This causes the hydrogen atoms to emit a weak radio signal which is amplified by the scanner. The scanners used in medicine have a typical magnetic field strength of 0.2 to 3 teslas. Construction costs approximately one million dollars per tesla and maintenance an additional several hundred thousand dollars per year. Research using MRI scanners operating at ultra high field strength, up to 21.1 tesla, can produce images of the mouse brain with a resolution of 18 micrometers (Hunold, Vogt, Schmermund, Debatin, Kerkhoff, Budde, Erbel, Ewen, & Barkhausen, 2003).
Both CT and MRI scanners can generate multiple two-dimensional cross-sections of tissues and three dimensional reconstruction. “Unlike CT, it uses only X-ray attenuation to generate image contrast MRI has a log list of properties that may be used to generate image contrast.” For purposes of tumor detection and identifications, MRI is generally superior. However, CT usually is more widely available, faster, much less expensive, and less likely to require the person to be sedated or anesthetized. MRI is also best for cases when a patient is to undergo the exam several times successively in the short term, because unlike CT, it doesn't expose the patient to the hazards of ionizing radiation. Indeed, unlike CT scanning MRI uses no ionizing radiation and is generally a very safe procedure (Wu, Chesler, Glimcher, Garrido, Wang, Jiang, & Ackerman, 1999, Mietchen, Aberhan, Manz, Hampe, Mohr, Neumann, and Volke, 2008, Colosimo, Celi, Settecasi, Tartaglione, Di Rocco, & Marano, 1995, Allen, Byrd, Darling, Tomita, Wilczynski, 1993, Deck, Henschke, Lee, Zimmerman, Hyman, Edwards, Saint Louis, Cahill, Stein,& Whalen, 1989).
Lastly, “Positron emission tomography (PET) is a nuclear medicine medical imagining technique which produces a three-dimensional image or map of functional processes in the body.” The system detects pairs of gamma rays emitted indirectly by a positron-emitting radioisotope, which is introduced into the body on a metabolically active molecule. Images of metabolic activity in space are then reconstructed by computer analysis, often in modern scanners aided by results from a CT X-ray scan performed on the patient at the same time, in the same machine (Phelps, Hoffman, Mullani, and Ter-Pogossian, 1974).
This image illustrates the processing principals of a positron emission tomography (PET) commonly used in cancer diagnostics. The photons are registered by the PET as soon as they arrive at the detector ring. After the registration, the data is forwarded to a procession unit which decides if two registered events are selected as so-called coincidence event. All coincidence are forwarded to the image procession unit where the final image data is produced via mathematical image reconstruction procedures (http://en.wikipedia.org/wiki/Image:PET-schema.png)
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The concept of emission and transmission tomography was introduced by David Kuhl and Roy Edwards in the late 1950s. Their work later led to the design and construction of several tomographic instruments at the University of Pennsylvania. Tomographic imaging techniques were further developed by Michel Ter-Pogossian, Michael E. Phelps and others at the Washington University School of Medicine.
“PET is a valuable technique for some diseases and disorders,” because it is possible to target the radio-chemicals used for particular bodily functions (Phelps, Hoffman, Mullani, and Ter-Pogossian, 1974):
1. Oncology: PET scanning with the tracer fluorine-18 (F-18) fluorodeoxyglucose (FDG), called FDG-PET, is widely used in clinical oncology. This tracer is a glucose analog that is taken up by glucose-using cells and phosphorylated by hexokinase (whose mitochondrial form is greatly elevated in rapidly-growing malignant tumours). A typical dose of FDG used in an oncological scan is 200-400 MBq for an adult human. Because the oxygen atom which is replaced by F-18 to generate FDG is required for the next step in glucose metabolism in all cells, no further reactions occur in FDG. Furthermore, most tissues (with the notable exception of liver and kidneys) cannot remove the phosphate added by hexokinase. This means that FDG is trapped in any cell which takes it up, until it decays, since phosphorylated sugars, due to their ionic charge, cannot exit from the cell. This results in intense radiolabeling of tissues with high glucose uptake, such as the brain, the liver, and most cancers. As a result, FDG-PET can be used for diagnosis, staging, and monitoring treatment of cancers, particularly in Hodgkin's disease, non Hodgkin's lymphoma, and lung cancer. Many other types of solid tumors will be found to be very highly labeled on a case-by-case basis-- a fact which becomes especially useful in searching for tumor metastasis, or for recurrence after a known highly-active primary tumor is removed. Because individual PET scans are more expensive than "conventional" imaging with computed tomography (CT) and magnetic resonance imaging (MRI), expansion of FDG-PET in cost-constrained health services will depend on proper health technology assessment; this problem is a difficult one because structural and functional imaging often cannot be directly compared, as they provide different information. Oncology scans using FDG make up over 90% of all PET scans in current practice.
2. Neurology: PET neuroimaging is based on an assumption that areas of high radioactivity are associated with brain activity. What is actually measured indirectly is the flow of blood to different parts of the brain, which is generally believed to be correlated, and has been measured using the tracer oxygen-15. However, because of its 2-minute half-life O-15 must be piped directly from a medical cyclotron for such uses, and this is difficult. In practice, since the brain is normally a rapid user of glucose, and since brain pathologies such as Alzheimer's disease greatly decrease brain metabolism of both glucose and oxygen in tandem, standard FDG-PET of the brain, which measures regional glucose use, may also be successfully used to differentiate Alzheimer's disease from other dementing processes, and also to make early diagnosis of Alzheimer's disease. The advantage of FDG-PET for these uses is its much wider availability. PET imaging with FDG can also be used for localization of seizure focus: A seizure focus will appear as hypometabolic during an interictal scan. Several radiotracers (i.e. radioligands) have been developed for PET that are ligands for specific neuroreceptor subtypes such as [11C] raclopride and [18F] fallypride for dopamine D2/D3 receptors, [11C]McN 5652 and [11C]DASB for serotonin transporters, or enzyme substrates (e.g. 6-FDOPA for the AADC enzyme). These agents permit the visualization of neuroreceptor pools in the context of a plurality of neuropsychiatric and neurologic illnesses. A novel probe developed at the University of Pittsburgh termed PIB (Pittsburgh Compound-B) permits the visualization of amyloid plaques in the brains of Alzheimer's patients. This technology could assist clinicians in making a positive clinical diagnosis of AD pre-mortem and aid in the development of novel anti-amyloid therapies.
3. Cardiology, atherosclerosis and vascular disease study: In clinical cardiology, FDG-PET can identify so-called "hibernating myocardium", but its cost-effectiveness in this role versus SPECT is unclear. Recently, a role has been suggested for FDG-PET imaging of atherosclerosis to detect patients at risk of stroke.
4. Neuropsychology / Cognitive neuroscience: To examine links between specific psychological processes or disorders and brain activity.
5. Psychiatry: Numerous compounds that bind selectively to neuroreceptors of interest in biological psychiatry have been radiolabeled with C-11 or F-18. Radioligands that bind to dopamine receptors (D1,D2, reuptake transporter), serotonin receptors (5HT1A, 5HT2A, reuptake transporter) opioid receptors (mu) and other sites have been used successfully in studies with human subjects. Studies have been performed examining the state of these receptors in patients compared to healthy controls in schizophrenia, substance abuse, mood disorders and other psychiatric conditions.
6. Pharmacology: In pre-clinical trials, it is possible to radiolabel a new drug and inject it into animals. The uptake of the drug, the tissues in which it concentrates, and its eventual elimination, can be monitored far more quickly and cost effectively than the older technique of killing and dissecting the animals to discover the same information. PET scanners for rats and non-human primates are marketed for this purpose. The technique is still generally too expensive for the veterinary medicine market, however, so very few pet PET scans are done. Drug occupancy at the purported site of action can also be inferred indirectly by competition studies between unlabeled drug and radio labeled compounds known apriority to bind with specificity to the site.
“Ionizing radiation is energetic particles or waves that have the potential to ionize an atom or molecule.” It is a function of the energy of the individual particles or waves, and not a function of the number of particles or waves present. There are some ionizing radiation level examples(Oak Ridge National Laboratory):
3 mSv USA average dose from all natural source
3.66mSv USA average from all sources; including medical diagnostic radiation doses
244 mrem Average dose from an upper gastrointestinal diagnostic X-ray series
10 rem Estimated level at which an acute dose would result in a lifetime excess risk of death form cancer 0.8%
50 to 600 rem Level at which doses received over a short period of time produce radiation sickness in varying degrees. At the lower end of this range, people are expected to recover completely, given proper medical attention. At the top of this rang, most people will die within 60 days.
Radiation identified that “radioactivity is the name given to the spontaneous emission of alpha, beta, and gamma rays by some elements.” (on the beauty of physics, p. 190)
When alpha, beta, and gamma rays were reviewed by first realizing that the alpha particle is an ionized Helium atom. Electromagnetic (EM) radiation, is a self-propagating wave disturbance in space which is the phenomenon perceived by the human eye as light. EM radiation has an electric and magnetic field component which oscillate in phase perpendicular to each other and to the direction of energy propagation. Electromagnetic radiation is classified into types according to the frequency of the wave, these types include (in order of increasing frequency): radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. Where radio waves have the longest wavelength and Gamma rays have the shortest. EM radiation carries energy and momentum, which may be imparted when it interacts with matter. Indeed, Beta, the electron and gamma-rays as highest energy light.
Craniopharyngioma is a type of tumor that constitutes 9% of all pediatric brain tumors. They usually occur in children between 5 and 10 years of age. It has a point prevalence of approximately 2/100,000. They are also known as Rathke pouch tumors, hypophyseal dct tumors, or adamantinomas.
The American Society of Radiologic Technologists (ASRT) is the world's largest and oldest membership association for medical imaging technologists and radiation therapists. It was founded in 1920, the ASRT has more than 128,000member and located in Albuquerque, New Mexcio. (ASRT history)
The ASRT surpassed the 125,000 members mark in 2007 and also today it has a fifteen million dollars annual operating budget and more than one hundred employees. The ASRT accomplishes its mission so far through the following (ASRT history):
Meetings. The ASRT conducts two national meetings annually. Each June, the ASRT Annual Conference offers educational courses in specialty areas of the profession. The Annual Conference also is where the ASRT House of Delegates meets to set direction for the Society and the profession. Each fall, ASRT conducts a Radiation Therapy Conference in conjunction with the annual meeting of the American Society for Therapeutic Radiology and Oncology. Educational courses at this conference focus on radiation therapy and medical dosimetry.
Publications. The ASRT publishes two peer-reviewed research journals. The award-winning bimonthly journal Radiologic Technology keeps readers informed about advances in technology and patient care. It also offers ASRT members the opportunity to earn continuing education credit through its Directed Reading program. Radiation Therapist, published twice a year, focuses on technical advances in radiation oncology. It, too, features a Directed Reading program. ASRT Scanner is the society's member magazine. Through its in-depth reporting, Scanner helps members stay up-to-date on the issues that affect them and their profession. In addition, the ASRT operates a Web site, www.asrt.org, which contains news, information about the profession, educational material for patients and a variety of professional resources for radiologic technologists.
Career Resources. The Society tracks members' CE credits and issues an annual report that can be submitted to a certification agency as proof of continuing education. It conducts regular salary surveys of the profession, providing valuable information about income levels and trends. It also operates an Internet-based employment service, the ASRT JobBank®, through which technologists can conduct nationwide job searches. And the ASRT provides radiologic technologists with top-quality educational materials covering every practice area, from pediatric radiography to cancer pain management.
Advocacy and Representation. The ASRT monitors and responds to all state and federal legislation that affects the profession. It is working with other radiologic science organizations to establish federal minimum standards to ensure that patients receive the best care possible. The ASRT also educates the public about the role of registered radiologic technologists in providing quality patient care, sponsoring National Radiologic Technology Week® each year to raise awareness about the profession.
Professional Issues. The ASRT works with the profession's accreditation and certification agencies to develop and revise educational curricula, implement entry-level standards for the profession and establish practice guidelines The ASRT also helps recruit students to careers in radiologic technology, works with equipment manufacturers to help implement technological change, and represents the profession in the governmental, educational and research arenas. The Society has been instrumental in the development of the radiologist assistant, a new career level for radiologic technologists. The first educational program for radiologist assistants opened in 2003 and the first graduates were certified as radiologist assistants in 2005.
There are historical highlights:
1920 American Association of Radiological Technicians formed in Chicago with 14 charter members.
1929 Organization begins publishing The X-Ray Technician.
1932 Organization changes its name to the American Society of X-Ray Technicians; membership reaches 400.
1948 Membership climbs to 2,500.
1952 ASXT writes its first radiography curriculum; membership at 4,000.
1964 Organization changes its name to the American Society of Radiologic Technologists and changes the name of its journal to Radiologic Technology.
1968 ASRT opens office in Chicago; membership at 14,000.
1975 ASRT launches voluntary continuing education program for R.T.s.
1981 Congress passes Consumer-Patient Radiation Health and Safety Act.
1983 ASRT relocates to Albuquerque, N.M.
1986 ASRT House of Delegates formed.
1994 Membership reaches 28,500.
1995 Continuing education becomes mandatory for technologists registered by the American Registry of Radiologic Technologists.
1996 Membership climbs to 56,000.
1998 ASRT launches its Web site, www.asrt.org.
1999 ASRT receives Piñon Quality Award.
2000 Consumer Assurance of Radiologic Excellence bill introduced in Congress; bill is reintroduced in 2001, 2003 and 2005.
2002 Membership reaches 100,000.
2004 ASRT completes a major renovation of its office in Albuquerque, N.M., that more than doubles the size of the facility.
2005 Online version of Radiologic Technology debuts. Membership reaches 120,000.
2007 The CARE bill is reintroduced in both houses of Congress with a new name: Consistency, Accuracy, Responsibility and Excellence in Medical Imaging and Radiation Therapy. Membership reaches 125,000.
There is information about radiation from the surface in certain places (Terrestrial sources of radiation.):
Guarapari Beach, Brazil 800 mSv/area
Ramsar, Iran 700 mSv/area
Kerala Beach, India 35mSv/area
City of Pripyat (near Chernobyl), Ukrain 5.0 mSv/area
Reference
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ASRT history. Retrieved April 29, 2008 from https://www.asrt.org/content/aboutasrt/history.aspx
On the beauty of physics, p. 190. Retreived February 19, 2008.
Brenner. D, & Hall. E (2007, November 29). Computed Tomography- An Increasint Source of Radiation Exposure. Retrieved January 25, 2008, from http://content.nejm.org/cgi/reprint/357/22/2277.pdf
Colosimo, C., Celi, G., Settecasi, C., Tartaglione, T., Di Rocco, C., & Marano, P. (1995, October) Magnetic resonance and computerized tomography of posterior cranial fossa tumors in childhood. Differential diagnosis and assessment of lesion extent. Retrieved April 14, 2008 from http://www.ncbi.nlm.nih.gov/pubmed/8552814
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Oak Ridge National Laboratory. Retreived May 1, 2008 from http://www.ornl.gov/sci/env_rpt/aser95/tb-a-2.pdf
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Phillips (2008) Retrieved January 27, 2008 from http://www.philips.com/about/index.page
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