Learn About Android

Learn About ANDROID


Introduction:  Android is a Linux-based mobile phone operating system developed by Google. Android is unique because Google is actively developing the platform but giving it away for free to hardware manufacturersand phone carriers who want to use Android on their devices.
Beyond the Phone:
A modified version of Android is used in the Google TV, the Barnes & Noble Nook eReader, the Samsung Galaxy Tab, and countless other devices. Parrot makes both a digital photo frame and a car stereo system powered by modified versions of Android.

Open Handset Alliance:
Google formed a group of hardware, software, and telecommunication companies called the Open Handset Alliance with the goal of contributing to Android development. Most members also have the goal of making money from Android, either by selling phones, phone service, or mobile applications.

Android Market:
Anyone can download the SDK (software development kit) and write applications for Android phones. Google doesn't screen developers or applications.
These apps can be downloaded from the Android Market. If the app costs money, you pay for it using Google Checkout. T-Mobile also has an agreement to allow their phone customers to purchase some apps and have the fee added to their monthly phone bill.

Some devices do not include support for the Android Market and may use an alternative market.
 
Service Providers:
The iPhone has been very popular for AT&T, but unless you void your warranty to unlock it, you can only use an iPhone with AT&T. Android is an open platform, so many carriers can potentially offer Android-powered phones. That doesn't mean individual carriers won't lock the specific phone they sell you to their service, but every major carrier in the US offers an Android phone. Android is currently the fastest growing phone platform in the world.

Data Plan:
To use Android on a phone, you need a data plan on top of your voice plan. You can't even activate an Android phone without a data plan enabled. Some networks in the US offered tiered data service, and some offer unlimited plans.

Google Services:
Because Google developed Android, it comes with a lot of Google services installed right out of the box. Gmail, Google Calendar, Google Maps, and Google Web search are all pre-installed, and Google is also the default Web page for the Web browser. However, because Android can be modified, carriers can choose to change this. Verizon Wireless, for instance, has modified some Android phones to use Bing as the default search engine.

Touchscreen:
Android supports a touch screen and is difficult to use without one. You can use a trackball for some navigation, but nearly everything is done through touch. Android also supports multi-touch gestures such as pinch-to-zoom in versions 2.1 (Eclair) and above.
Keyboard:
The initial release of Android required a separate keyboard. However, "Cupcake," (Android 1.5) and later editions have all supported an on-screen keyboard. That means you can use models like the Verizon Droid 2 that include a slide-out physical keyboard or the HTC EVO that rely entirely on the touch screen.

The Bottom Line:
Android is an exciting platform for consumers and developers. It is the philosophical opposite of the iPhone in many ways. Where the iPhone tries to create the best user experience by restricting hardware and software standards, Android tries to insure it by opening up as much of the operating system as possible.

This is both good and bad. Fragmented versions of Android may provide a unique user experience, but they also mean fewer users per 
variation. That means it's harder to support for app developers, accessory makers, and technology writers (ahem). Because each Android upgrade must be modified for the specific hardware and user interface upgrades of each device, that also means it takes longer for modified Android phones to receive updates.
Fragmentation issues aside, Android is a robust platform that boasts some of the fastest and most amazing phones and tablets on the market.


BC.. AD.. What does it Refers to...

What is BC and what is AC



It is commonly thought that BC stands for "before Christ" and AD stands for "after death." This is only half correct. How could the year 1 B.C. have been "before Christ" and 1 A.D. been "after death"? BC does stand for "before Christ." AD actually stands for the Latin phrase "anno domini" which means "in the year of our Lord." The B.C. / A.D. dating system is not taught in the Bible. It actually was not fully implemented and accepted until several centuries after Jesus' death.

It is interesting to note that the purpose of the BC / AD dating system was to make the birth of Jesus Christ the dividing point of world history. However, when the B.C. / A.D. system was being calculated, they actually made a mistake in pinpointing the year of Jesus' birth. Scholars later discovered that Jesus was actually born in around 4-6 BC, not 1 AD. That is not the crucial issue.

science facts


science facts



1. Every year over one million earthquakes shake the Earth.

2. It takes 8 minutes 17 seconds for light to travel from the Sun’s surface to the Earth.

3. In October 1999 the 6 billionth person was born.

4. 10 percent of all human beings ever born are alive at this very moment.

5. The Earth spins at 1,000 mph but it travels through space at an incredible 67,000 mph.

6. The speed of light is 186,000 miles per second.

7. The largest ever hailstone weighed over 1 kg and fell in Bangladesh in 1986.

8. Every second around 100 lightning bolts strike the Earth.

9. Every year lightning kills 1000 people.

10. In October 1999 an Iceberg the size of London broke free from the Antarctic ice shelf.

11. If you could drive your car straight up you would arrive in space in just over an hour.

12. All the hydrogen atoms in our bodies were created 12 billion years ago in the Big Bang.

13. The Earth is 4.56 billion years old…the same age as the Moon and the Sun.

14. The dinosaurs became extinct before the Rockies or the Alps were formed.

15. Female black widow spiders eat their males after mating.

16. When a flea jumps, the rate of acceleration is 20 times that of the space shuttle during launch.

17. The earliest wine makers lived in Egypt around 2300 BC.

18. If our Sun were just inch in diameter, the nearest star would be 445 miles away.

19. The Australian billy goat plum contains 100 times more vitamin Cthan an orange.

20. Astronauts cannot belch – there is no gravity to separate liquid from gas in their stomachs.

21. The air at the summit of Mount Everest, 29,029 feet is only a third as thick as the air at sea level.

22. One million, million, million, million, millionth of a second after the Big Bang the Universe was the size of a …pea.

23. DNA was first discovered in 1869 by Swiss Friedrich Mieschler.

24. The molecular structure of DNA was first determined by Watson and Crick in 1953.

25. The thermometer was invented in 1607 by Galileo.

26. Englishman Roger Bacon invented the magnifying glass in 1250.

27. Alfred Nobel invented dynamite in 1866.

28. Wilhelm Rontgen won the first Nobel Prize for physics for discovering X-rays in 1895.

29. The tallest tree ever was an Australian eucalyptus – In 1872 it was measured at 435 feet tall.

30. Christian Barnard performed the first heart transplant in 1967 – the patient lived for 18 days.

31. The wingspan of a Boeing 747 is longer than the Wright brother’s first flight.

32. An electric eel can produce a shock of up to 650 volts.

33. Human tapeworms can grow up to 22.9m.

34. Chimps can understand 300 different signs.

35. The Ebola virus kills 4 out of every 5 humans it infects.

36. In 5 billion years the Sun will run out of fuel and turn into a Red Giant.

37. Without its lining of mucus your stomach would digest itself.

38. Humans have 46 chromosomes, peas have 14 and crayfish have 200.

39. There are 60,000 miles of blood vessels in the human body.

40. An individual blood cell takes about 60 seconds to make a complete circuit of the body.

41. On the day that Alexander Graham Bell was buried the entire US telephone system was shut down for 1 minute in tribute.

42. The low frequency call of the humpback whale is the loudest noise made by a living creature.

43. The call of the humpback whale is louder than Concorde and can be heard from 500 miles away.

44. A quarter of the world’s plants are threatened with extinction by the year 2010.

45. Each person sheds 40lbs of skin in his or her lifetime.

46. At 15 inches the eyes of giant squids are the largest on the planet.

47. The largest galaxies contain a million, million stars.

48. The Universe contains over 100 billion galaxies.

49. Wounds infested with maggots heal quickly and without spread of gangrene or other infection.

50. More germs are transferred shaking hands than kissing.

51. The longest glacier in Antarctica, the Almbert glacier, is 250 miles long and 40 miles wide.

52. The fastest speed a falling raindrop can hit you is 18mph.

53. A salmon-rich, low cholesterol diet means that Inuits rarely suffer from heart disease.

54. Inbreeding causes 3 out of every 10 Dalmation dogs to suffer from hearing disability.

55. The world’s smallest winged insect, the Tanzanian parasitic wasp, is smaller than the eye of a housefly.

56. If the Sun were the size of a beach ball then Jupiter would be the size of a golf ball and the Earth would be as small as a pea.

57. It would take over an hour for a heavy object to sink 6.7 miles down to the deepest part of the ocean.

58. There are more living organisms on the skin of each human than there are humans on the surface of the earth.

59. The grey whale migrates 12,500 miles from the Artic to Mexico and back every year.

60. Quasars emit more energy than 100 giant galaxies.

61. Quasars are the most distant objects in the Universe.

62. The Saturn V rocket which carried man to the Moon develops power equivalent to fifty 747 jumbo jets.

63. Koalas sleep an average of 22 hours a day, two hours more than the sloth.

64. Light would take .13 seconds to travel around the Earth.


65. Neutron stars are so dense that a teaspoonful would weigh more than all the people on Earth.

66. One in every 2000 babies is born with a tooth.

67. Every hour the Universe expands by a billion miles in all directions.

68. Somewhere in the flicker of a badly tuned TV set is the background radiation from the Big Bang.

69. The temperature in Antarctica plummets as low as -35 degrees Celsius.

70. Space debris travels through space at over 18,000 mph.

71. The International Space Station weighs about 500 tons and is the same size as a football field.

72. Astronauts brought back about 800 pounds of lunar rock to Earth. Most of it has not been analyzed.

73. Tuberculosis is the biggest global killer of women.

74. Hummingbirds consume half of their body weight in food every day.

75. Some species of bamboo grow at a rate of 3ft per day.

76. Saturn would float if you could find an ocean big enough.

77. The highest recorded train speed is 320.2 mph by the TGV train in France.

78. The highest speed ever achieved on a bicycle is 166.94 mph by Fred Rompelburg.

79. The research spacecraft Helios B came within a record 27 million miles of the Sun.

80. 65 million years ago the impact of an asteroid is estimated to have had the power of 10 million H-Bombs.

81. The temperature at the centre of the Earth is estimated to be 5500 degrees Celsius.

82. Argentia in Newfoundland has an average 206 days of fog each year.

83. Mount Waiale’ale in Hawaii is the rainiest place in the world and has 335 rainy days a year.

84. 68% of all UFO sightings are by men.

85. 15% of the world’s fresh water flows down the Amazon.

86. A cat has 32 sets of muscles in each ear.

87. Over two-thirds of people admit to urinating while in public swimming pools.

88. More people die of heart attacks on Monday than on any other day of the week.

89. Beetles are the strongest animals on Earth relative to their size. A rhinoceros beetle can carry 850 times its own weight in its back.

90. In 1961 the Soviet Cosmonaut Yuri Gagarin became the first human in Space.

91. In 1876 Alexander Graham Bell invented the telephone.

92. In 1885 Karl Benz built the first car powered by an internal combustion engine.

93. Scotsman John Baird invented the Baird televisor (now the television) in 1925.

94. Io, one of Jupiter’s moons, is the most volcanically active place in the Solar System.

95. The Walkman was launched in Japan by Sony in 1979.

96. Traffic lights with red and green gas lights were first introduced in London in 1868. Unfortunately, they exploded and killed a policeman. The first successful system was installed in Cleveland, Ohio in 1914.

97. Ticks are second only to the mosquito as the most dangerous parasites to humans.

98. 3 billion of the world’s 6 billion population are under the age of 25.

99. Infant mortality in 1900 was 142 in 1000 births. By 2000 it had reduced to just 6 in every 1000.

100. In total there is said to be around 400 million dogs in the world

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Radiology Technician Schools



Radiology Technician School

For those of you who wish to take up a career as a radiology technician, you need to learn how to select a radiology technician school where you will be offered the best radiologic technologist program to get you through your training and educate you on your chosen subject.
Unlike several leading industries, the medical field does not appear to have been affected by economic problems and this is the reason why many people are opting for careers within this area. There is an endless amount of opportunities open to those wanting to venture into the medical industry and positions such as radiology employment, for example, are well paid and regularly sought after. A career as a radiology technologist can take the job holder anywhere and you could find yourself working in a small office, a clinic or a large hospital. However, when considering where to train you need to completely understand the skills required and the demands made as far as this kind of job is concerned and this will help you to select the right radiology tech school where your radiology technologist career goals can be achieved.
The job of radiologic technologist involves working with X-ray and ultrasound equipment in order to explain the process and techniques used and give the results of the diagnosis to the patient. The machines used also have to be maintained by the job holder. The average annual salary is in the region of $35,000 and $45,000, the exact amount being determined by where the work takes place. This could be in a clinic, a hospital, a nursing home or all manner of other health facility locations. It is useful to know which of these locations you would prefer to work in and what type of degree and training is needed prior to deciding which radiology school to attend.
The training provided at radiology schools has to be successfully completed in order to become a radiologist. The duration of the training is usually two years but there are four year courses on offer too. A radiologic technologist student can obtain a degree or a certificate. The latter is more often than not recommended for someone who is already trained and working in the medical field and looking for a change in career direction. A good program will be with an accredited college and hands on training using and maintaining the relevant equipment and dealing with patients will be part of the training program. When the program has been completed a person can then begin their career as a certified technician.
With so many options of different radiology education programs available, the one you choose all comes down to a matter of personal choice. Of course, personal needs also have to be taken into account when looking for a program to fit in with your schedule as it is necessary that you are able to attend class without disturbing or interfering with your other daily obligations.
It goes without saying that a good understanding of a career in this field is necessary before embarking on radiology training. If you are fully aware of the kind of skills you are required to have and the things you need to learn about, this will help you to choose the best school for you and by collecting together these details the program choosing task can be made so much easier. The radiology technician program you opt for should allow you to begin work in your new and interesting career as soon as the training is completed.



Drug Addicts-Rehab

                                  What is Drug Addiction - How to Rehab   
                   
Drug Addiction and substance abuse is a chronic, relapsing disease wherein the drug user compulsively spends time looking for and using an illegal drug. This form of addiction is characterized by neurochemical and molecular changes in the brain. Some of the common drugs used by drug addicts are heroin, cocaine, lysergic acid diethylamide (LSD), mandrax, barbiturates and a variety of opiates. Estimates indicate that there are around three million drug addicts in the world


Traditionally, drug addicts are usually the responsibility of the family or the social group to which they belong. In most cases, drug addicts are treated through general health services, on a voluntary basis. Now, State level hospitals also offer rehabilitation facilities for indoor treatment to hard-core addicts through their psychiatry departments. Besides State run treatment centres, there is a network of de-addiction centres run by voluntary organizations. Also, community based treatment programmes are operated in different regions of the country.


The main thrust of these programmes is to strengthen the ties of addicts to their family and community and get the community to cooperate in the rehabilitation process. The de-addiction centres run by non-governmental organizations employ various systems of medicine such as allopathy, homeopathy, ayurveda, naturopathy and yoga coupled with a range of psychotherapies to cure addicts.

If drug addicts are to be completely rehabilitated, it is necessary for the local community to be involved in the treatment and social integration of addicts. To promote such an initiative a number of de-addiction camps(External website that opens in a new window) are being regularly organized at the community level through voluntary organizations. These camps provide counselling, treatment and rehabilitation facilities to drug addicts in the localities they live in. Building awareness and creating therapeutic communities are other concepts that help in the rehabilitation of addicts. More on de-addiction camps(External website that opens in a new window).
Self-help techniques have proved to be quite useful in the treatment of different types of addictions. A popular group that offers such techniques is Narcotics Anonymous(External website that opens in a new window). This group conducts private meetings where addicts learn from other addicts how to remain drug free and recover from addiction. 


Drug Rehab Program:- How to ??

Selecting a drug rehab center is one of the most important Drug rehab Treatment Centers Drug addiction rehabilitation Programand difficult decisions you will make in your lifetime. Few of us know what to look for in a quality rehab program and not all drug rehabilitation centers are alike. Each drug rehab has its own program options, staff qualifications, credentials, cost, and effectiveness.
Asking appropriate questions when you call a drug rehab for information is important and you should expect to receive clear answers.
Before you make any decisions-ask questions and get the facts!

Does the drug rehab offer a variety of programs?

Alcohol and drug addiction are diseases that progress through predictable stages. It takes a trained health professional, often a doctor specializing in addiction medicine, to make an accurate diagnosis and prescribe the most appropriate treatment, whether it be outpatient counseling or an inpatient alchol and drug rehab.
A drug rehabilitation treatment center should offer a variety of treatment programs that meet individual needs. Programs may include inpatient, residential, outpatient, and/or short-stay options.
The difference between inpatient and a residential treatment center is that inpatient services are provided by a licensed hospital, while residential programs usually do not meet the same rigorous standards of medical care.
The length of stay depends on the severity and stage of the disease.

How much does a drug rehab center cost?

"How much does it cost?" is often one of the first questions asked when someone calls a drug rehab program.
The price tag for drug rehab treatment depends on the type of rehab you choose. You need to know what is included, what will be added to your bill as a fee-for-service program, and what services your health insurance will cover. This makes it extremely difficult to compare prices by simply asking the question - "What does rehab cost?" The best way to find out the range of costs for rehab is to talk to an intake advisor. You can discuss your insurance coverage or your financial concerns and they will help you narrow down your choices to what best meets your needs in the most affordable way.
If you are seeking the best value for your treatment dollar, remember: Price can be meaningful only in the context of quality and performance.
Also remember that the cost of drug addiction and alcoholism, if not treated, can far exceed the cost of treatment.

Is the drug rehab treatment program medically based?

There is an advantage to including on-site medical care in a Drug Rehab. Physicians and nurses provide 24-hour hospital services to monitor and ensure a safe withdrawal from alcohol and other drugs. In addition, a medical staff specializing in addiction medicine can oversee the progress of each individual and make necessary adjustments to the treatment plan.
Medical credentials and accreditation can also be important. For example, a chemical dependency Drug Rehab that earns JCAHO accreditation (Joint Commission on Accreditation of Healthcare Organizations) meets national standards for providing quality medical care. Appropriate state licensing is also an important consideration.
Be sure to ask which medical costs are included in the price of treatment at the drug rehab.

What is the degree of family involvement in a drug rehab program?

Drug abuse and alcoholism affects the entire family, not just the alcoholic/addict. Quite often family members do not realize how deeply they have been affected by chemical dependency. Family involvement is an important component of recovery.
Drug Rehabs vary in the degree and quality of family involvement opportunities. Some offer just a few lectures and others offer family therapy. Ask if there is any time devoted to family programs and if group therapy is included.

Does drug rehabilitation include a quality continuing care program?

There are no quick fixes for the diseases of drug abuse and alcoholism. Recovery is an ongoing process. The skills one learns during intensive rehabilitation treatment must be integrated into everyday life and this takes time.
Some drug addiction treatment programs will offer a follow-up program but only in one location which may make it difficult to use.
Drug rehabilitation treatment programs should include a quality, continuing care program that supports and monitors recovery.
The decision to enter a drug rehab program can be a very difficult and painstaking process. 

Picture archiving and communication system


Picture archiving and communication system (PACS)


picture archiving and communication system (PACS) is a medical imaging technology which provides economical storage of, and convenient access to, images from multiple modalities (source machine types). Electronic images and reports are transmitted digitally via PACS; this eliminates the need to manually file, retrieve, or transport film jackets. The universal format for PACS image storage and transfer is DICOM (Digital Imaging and Communications in Medicine).

Types of images

Most PACSs handle images from various medical imaging instruments, including ultrasound (US),magnetic resonance (MR), positron emission tomography (PET), computed tomography (CT), endoscopy (ENDO), mammograms (MG),Digital radiography (DR), computed radiography (CR) ophthalmology, etc. Additional types of image formats are always being added. Clinical areas beyond radiology; cardiology, oncology, gastroenterology and even the laboratory are creating medical images that can be incorporated into PACS. (see DICOM Application areas).
Uses

PACS is offered by virtually all the major medical imaging equipment manufacturers, medical IT companies and many independent software companies. Basic PACS software can be found free on the Internet.
Hard copy replacement: PACS replaces hard-copy based means of managing medical images, such as film archives. With the decreasing price of digital storage, PACSs provide a growing cost and space advantage over film archives in addition to the instant access to prior images at the same institution. Digital copies are referred to as Soft-copy.

  • Radiology Workflow Management: PACS is used by radiology personnel to manage the workflow of patient exams.
PACS is offered by virtually all the major medical imaging equipment manufacturers, medical IT companies and many independent software companies. Basic PACS software can be found free on the Internet.

Architecture


Querying & Image Retrieval

The communication with the PACS server is done through dicom objects that are similar to dicom images, but with different tags. A query typically looks as follows:
  • The client establishes the network connection to the PACS server.
  • The client prepares a query object which is an empty dicom dataset object.
  • The client fills in the query object with the keys that should be matched. E.g. to query for a patient ID, the patient ID tag is filled with the patient's ID.
  • The query object is sent to the server.
  • The server sends back to the client a list of response dicom objects.
  • The client extracts the tags that are of interest from the response dicom objects.

Image archival and backup

Digital medical images are typically stored locally on a PACS for retrieval. It is important (and required in the USA by the Security Rule's Administrative Safeguards section of HIPAA) that facilities have a means of recovering images in the event of an error or disaster. While each facility is different, the goal in image back-up is to make it automatic and as easy to administer as possible. The hope is that the copies won't ever be needed, but, as with other disaster recovery and business continuity planning, they need to be available if needed.

Integration


A chest image displayed via a PACS
A full PACS should provide a single point of access for images and their associated data. That is, it should support all digital modalities, in all departments, throughout the enterprise.
However, until PACS penetration is complete, individual islands of digital imaging not yet connected to a central PACS may exist. These may take the form of a localized, modality-specific network of modalities, workstations and storage (a so-called "mini-PACS"), or may consist of a small cluster of modalities directly connected to reading workstations without long term storage or management. Such systems are also often not connected to the departmental information system. Historically, Ultrasound, Nuclear Medicine and Cardiology Cath Labs are often departments that adopt such an approach.

Courtesy: en.wikipedis.org

Radiology Information System (RIS)

Radiology Information System (RIS)

A radiology information system (RIS) is a networked software suite for managing medical imagery and associated data. An RIS is especially useful for managing radiological records and associated data in a multiple locations and is often used in conjunction with a picture archiving and communication system (PACS) to manage work flow and billing.
An RIS has several basic functions:
Scheduling 
Appointments can be made for both in- and out-patients with specific radiology staff.  
Patient tracking
A patient’s entire radiology history can be tracked from admission to discharge.  The history can be coordinated with past, present and future appointments
This can be done as, first the patient order booking and the 0rder acceptance
Results reportingAn RIS can generate statistical reports for a single patient, group of patients or particular procedure. 
Film tracking
An RIS can track individual films and their associate data.  
Billing
An RIS facilitates detailed financial record-keeping, electronic payments and automated claims submission.





Radiology: The complete info

Radiology  what is it??
Radiology is the branch or specialty of medicine that deals with the study and application of imaging technology like x-ray and radiation to diagnosing and treating disease.


Radiologists direct an array of imaging technologies (such as ultrasound, computed tomography (CT), nuclear medicine, positron emission tomography (PET) and magnetic resonance imaging (MRI)) to diagnose or treat disease. Interventional radiology is the performance of (usually minimally invasive) medical procedures with the guidance of imaging technologies. The acquisition of medical imaging is usually carried out by the radiographer or radiologic technologist.


Radiology-Modalities
The following imaging modalities are used in the field of diagnostic radiology:


Projection (plain) radiography
Radiographs (or Roentgenographs, named after the discoverer of X-rays, Wilhelm Conrad Röntgen) are produced by the transmission of X-Rays through a patient to a capture device then converted into an image for diagnosis. The original and still common imaging produces silver impregnated films. In Film - Screen radiography an x-ray tube generates a beam of x-rays which is aimed at the patient. The x-rays which pass through the patient are filtered to reduce scatter and noise and then strike an undeveloped film, held tight to a screen of light emitting phosphors in a light-tight cassette. The film is then developed chemically and an image appears on the film. Now replacing Film-Screen radiography is Digital Radiography, DR, in which x-rays strike a plate of sensors which then converts the signals generated into digital information and an image on computer screen.


Plain radiography was the only imaging modality available during the first 50 years of radiology. It is still the first study ordered in evaluation of the lungs, heart and skeleton because of its wide availability, speed and relative low cost.


Fluoroscopy
Fluoroscopy and angiography are special applications of X-ray imaging, in which a fluorescent screen and image intensifier tube is connected to a closed-circuit television system. This allows real-time imaging of structures in motion or augmented with a radiocontrast agent. Radiocontrast agents are administered, often swallowed or injected into the body of the patient, to delineate anatomy and functioning of the blood vessels, the genitourinary system or the gastrointestinal tract. Two radiocontrasts are presently in use. Barium (as BaSO4) may be given orally or rectally for evaluation of the GI tract. Iodine, in multiple proprietary forms, may be given by oral, rectal, intraarterial or intravenous routes. These radiocontrast agents strongly absorb or scatter X-ray radiation, and in conjunction with the real-time imaging allows demonstration of dynamic processes, such as peristalsis in the digestive tract or blood flow in arteries and veins. Iodine contrast may also be concentrated in abnormal areas more or less than in normal tissues and make abnormalities (tumors, cysts, inflammation) more conspicuous. Additionally, in specific circumstances air can be used as a contrast agent for the gastrointestinal system and carbon dioxide can be used as a contrast agent in the venous system; in these cases, the contrast agent attenuates the X-ray radiation less than the surrounding tissues.


CT scanning
CT imaging uses X-rays in conjunction with computing algorithms to image the body. In CT, an X-ray generating tube opposite an X-ray detector (or detectors) in a ring shaped apparatus rotate around a patient producing a computer generated cross-sectional image (tomogram). CT is acquired in the axial plane, while coronal and sagittal images can be rendered by computer reconstruction. Radiocontrast agents are often used with CT for enhanced delineation of anatomy. Although radiographs provide higher spatial resolution, CT can detect more subtle variations in attenuation of X-rays. CT exposes the patient to more ionizing radiation than a radiograph. Spiral Multi-detector CT utilizes 8,16 or 64 detectors during continuous motion of the patient through the radiation beam to obtain much finer detail images in a shorter exam time. With rapid administration of IV contrast during the CT scan these fine detail images can be reconstructed into 3D images of carotid, cerebral and coronary arteries, CTA, CT angiography. CT scanning has become the test of choice in diagnosing some urgent and emergent conditions such as cerebral hemorrhage, pulmonary embolism (clots in the arteries of the lungs), aortic dissection (tearing of the aortic wall), appendicitis, diverticulitis, and obstructing kidney stones. Continuing improvements in CT technology including faster scanning times and improved resolution have dramatically increased the accuracy and usefulness of CT scanning and consequently increased utilization in medical diagnosis.


The first commercially viable CT scanner was invented by Sir Godfrey Hounsfield at EMI Central Research Labs, Great Britain in 1972. EMI owned the distribution rights to The Beatles music and it was their profits which funded the research. Sir Hounsfield and Alan McLeod McCormick shared the Nobel Prize for Medicine in 1979 for the invention of CT scanning. The first CT scanner in North America was installed at the Mayo Clinic in Rochester, MN in 1972.


Ultrasound
Medical ultrasonography uses ultrasound (high-frequency sound waves) to visualize soft tissue structures in the body in real time. No ionizing radiation is involved, but the quality of the images obtained using ultrasound is highly dependent on the skill of the person (ultrasonographer) performing the exam. Ultrasound is also limited by its inability to image through air (lungs, bowel loops) or bone. The use of ultrasound in medical imaging has developed mostly within the last 30 years. The first ultrasound images were static and two dimensional (2D), but with modern-day ultrasonography 3D reconstructions can be observed in real-time; effectively becoming 4D.


Because ultrasound does not utilize ionizing radiation, unlike radiography, CT scans, and nuclear medicine imaging techniques, it is generally considered safer. For this reason, this modality plays a vital role in obstetrical imaging. Fetal anatomic development can be thoroughly evaluated allowing early diagnosis of many fetal anomalies. Growth can be assessed over time, important in patients with chronic disease or gestation-induced disease, and in multiple gestations (twins, triplets etc.). Color-Flow Doppler Ultrasound measures the severity of peripheral vascular disease and is used by Cardiology for dynamic evaluation of the heart, heart valves and major vessels. Stenosis of the carotid arteries can presage cerebral infarcts (strokes). DVT in the legs can be found via ultrasound before it dislodges and travels to the lungs (pulmonary embolism), which can be fatal if left untreated. Ultrasound is useful for image-guided interventions like biopsies and drainages such as thoracentesis). Small portable ultrasound devices now replace peritoneal lavage in the triage of trauma victims by directly assessing for the presence of hemorrhage in the peritoneum and the integrity of the major viscera including the liver, spleen and kidneys. Extensive hemoperitoneum (bleeding inside the body cavity) or injury to the major organs may require emergent surgical exploration and repair.


MRI (Magnetic Resonance Imaging)
MRI uses strong magnetic fields to align atomic nuclei (usually hydrogen protons) within body tissues, then uses a radio signal to disturb the axis of rotation of these nuclei and observes the radio frequency signal generated as the nuclei return to their baseline states plus all surrounding areas. The radio signals are collected by small antennae, called coils, placed near the area of interest. An advantage of MRI is its ability to produce images in axial, coronal, sagittal and multiple oblique planes with equal ease. MRI scans give the best soft tissue contrast of all the imaging modalities. With advances in scanning speed and spatial resolution, and improvements in computer 3D algorithms and hardware, MRI has become a tool in musculoskeletal radiology and neuroradiology.


One disadvantage is that the patient has to hold still for long periods of time in a noisy, cramped space while the imaging is performed. Claustrophobia severe enough to terminate the MRI exam is reported in up to 5% of patients. Recent improvements in magnet design including stronger magnetic fields (3 teslas), shortening exam times, wider, shorter magnet bores and more open magnet designs, have brought some relief for claustrophobic patients. However, in magnets of equal field strength there is often a trade-off between image quality and open design. MRI has great benefit in imaging the brain, spine, and musculoskeletal system. The modality is currently contraindicated for patients with pacemakers, cochlear implants, some indwelling medication pumps, certain types of cerebral aneurysm clips, metal fragments in the eyes and some metallic hardware due to the powerful magnetic fields and strong fluctuating radio signals the body is exposed to. Areas of potential advancement include functional imaging, cardiovascular MRI, as well as MR image guided therapy.


Nuclear Medicine
Nuclear medicine imaging involves the administration into the patient of radiopharmaceuticals consisting of substances with affinity for certain body tissues labeled with radioactive tracer. The most commonly used tracers are Technetium-99m, Iodine-123, Iodine-131, Gallium-67 and Thallium-201. The heart, lungs, thyroid, liver, gallbladder, and bones are commonly evaluated for particular conditions using these techniques. While anatomical detail is limited in these studies, nuclear medicine is useful in displaying physiological function. The excretory function of the kidneys, iodine concentrating ability of the thyroid, blood flow to heart muscle, etc. can be measured. The principal imaging device is the gamma camera which detects the radiation emitted by the tracer in the body and displays it as an image. With computer processing, the information can be displayed as axial, coronal and sagittal images (SPECT images, single-photon emission computed tomography). In the most modern devices Nuclear Medicine images can be fused with a CT scan taken quasi-simultaneously so that the physiological information can be overlaid or co-registered with the anatomical structures to improve diagnostic accuracy.


PET,(positron emission tomography), scanning also falls under "nuclear medicine." In PET scanning, a radioactive biologically-active substance, most often Fluorine-18 Fluorodeoxyglucose, is injected into a patient and the radiation emitted by the patient is detected to produce multi-planar images of the body. Metabolically more active tissues, such as cancer, concentrate the active substance more than normal tissues. PET images can be combined with CT images to improve diagnostic accuracy.


The applications of nuclear medicine can include bone scanning which traditionally has had a strong role in the work-up/staging of cancers. Myocardial perfusion imaging is a sensitive and specific screening exam for reversible myocardial ischemia. Molecular Imaging is the new and exciting frontier in this field.