You might not often think about the amazing progress of imaging technology, but a crucial part of modern science is simply figuring out how to get a good look at things that we can't see under normal circumstances. What if I want to see the inside of my own body? The surface of a far-off planet? A scene that happened before I was born? Or the flagella of an organism too tiny to behold? Since prehistoric humans first discovered they could paint pictographs with the help of ochre and mineral pigments, we've been steadily learning new ways to see the unseeable, and picture what was previously unknown.
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If you've never thought of ink as an important technological development, it's worth a second look. Even before photographs, books and mass production of printed materials, inks and paints allowed humans to represent visually what people could never see firsthand. Above is the Adoration of the Magi by Albrecht Dürer, 1504. Artworks like these helped the mostly illiterate Christians of Europe visualize the stories of their holy books.
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So we all know there are millions of talented artists out there who can produce very lifelike drawings and paintings, but what if you really want to record an image -- quickly, objectively, mechanically, permanently? Enter the age of photography. Above is the daguerreotype camera, named after its inventor, the French painter and scientist Louis-Jacques-Mandé Daguerre. Click over to the next page to see what this machine could do.
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Daguerre unveiled his invention to the Académie des Sciences and the Académie des Beaux-Arts in 1839. At the time, people had never before seen chemically produced images of such clarity and detail. Over time, photography became more and more refined, as subsequent inventors developed shorter exposures, color film and eventually digital image processing. Next, you'll see the discoverer of a hitherto unknown form of radiation.
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The German physicist Wilhelm Röntgen discovered X-rays by accident in 1895. While working in his lab one night on a separate project, Röntgen noticed that if he darkened the room, his cathode ray tube emitted a beam of mysterious radiation that would illuminate a paper surface covered in barium platinocyanide. Click over to the next page to see how this was developed into an extremely useful imaging technology.
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Röntgen noticed that the rays streaming from his tube penetrated objects of different thickness and density with different levels of emerging luminosity. He tested the imaging potential of this new technology by creating a radiograph of his wife's hand, in which her bones and metal jewelry were very brightly visible, but her soft tissue only faintly so. The advantages of such a machine in the medical field were immediately obvious.
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"Röntgenograms" later became known as X-ray radiographs. Here you can see how X-rays, which are really just a high-frequency form of electromagnetic radiation, produce an image of the human body after passing through. Radiography of this kind is immensely useful in identifying skeletal fractures, foreign body ingestion and other internal injuries and masses.
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No, it's not Hewlett-Packard's new human fax machine. This is a fluoroscopy procedure. Fluoroscopy is an X-ray-based imaging technology that has been practiced by doctors for almost as long as standard X-rays. While standard radiographs provide still images of your bones and internal organs, fluoroscopy allows medical professionals to get a live, real-time video feed of what's going on in there. This is particularly useful in examining the workings of the gastrointestinal tract.
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This is a medical ultrasound machine -- an entirely different kind of internal imaging technology. The idea for sound-based imaging had been around since the late 19th century, but ultrasound wasn't used in a medical context until the 1920s, and it wasn't known for its diagnostic potential until the 1940s. To see an ultrasound image, head over to the next page.
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One of the most common uses of the medical ultrasound is in obstetrics -- the field of medical care having to do with pregnancy and childbirth. An ultrasound machine gathers data by emitting a high-frequency sound signal into your body and then listening for the sound to return as an echo. The machine interprets these echoes into a two-dimensional ultrasound image like the one above.
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Though we most often think of ultrasound as a procedure for expecting parents, it's useful for all kinds of diagnostic purposes. Above is an ultrasound image of a human thyroid. Next, you'll see a 3D ultrasound image.
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As image processing software improved, ultrasound machines became capable of producing 3D ultrasonography. The process is basically the same, except the machine uses multiple or moving sources of sound in order to collect data along multiple axes. The computers of today have no trouble turning this information into a textured 3D image.
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Transmission electron microscopes (TEMs), which create images of incredibly tiny structures and materials, have been around since the 1930s. TEMs work something like X-ray machines, in that they aim a beam of particles to pass through the subject, then the pattern of particles emerging on the other end produces the image. In this case, the machine shoots columns of electrons through subjects only a few angstroms in size. Next, you'll see an image from a more advanced form of electron microscope.
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This is about as close as anyone should want to get to a disease-transmitting bug. The scanning electron micgrograph (SEM) above shows an intensely magnified mosquito head. Compared to TEMs, SEMs offer a more textured, three-dimensional image of the subject. Though the technology to produce SEMs has been around almost as long as TEMs, it was not a preferred imaging method until much later. See more images from a scanning electron microscope by clicking ahead.
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This is an SEM of the human eye, viewed from the inside. Scanning electron microscopes can show incredible levels of texture on a scale we could never imagine viewing with our unaided biological eyes. You can almost imagine how these surfaces would feel to the touch -- if only your hands were small enough. Up next, see the true form of a familiar germ.
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Staphylococcus bacteria (the spheres) are responsible for many of the world's skin infections and instances of food poisoning. They lead to thousands of deaths every year, but under the SEM, they look downright cute. It's no wonder why the bacteria's name is based on the Greek word for a "bunch of grapes." Next, you'll see the massive machines that we use to create images of the outer universe.
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The word "telescope" usually conjures the idea of a straightforward light-magnifying apparatus that uses mirrors and lenses to make far objects visible. However, some of the most important modern astronomical observation is being done within other bands of the electromagnetic spectrum, through machines like the radio telescope antennas shown above.
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If this looks like the surface of a creepy alien planet, that's because it is. This is the rocky, toxic pressure cooker that we know as Venus, and this image of the surface of the inner-solar system planet was created with the help of synthetic-aperture radar. In the broadest sense, radar is the use of radio waves to gain physical information about distant objects. On the next page, you'll see a radio telescope's picture of our galaxy.
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In the early 1930s, a Bell Labs engineer named Karl Jansky discovered a constant stream of ambient radio interference that he couldn't trace to any source on Earth. Eventually, he discovered that the static he heard in repeating 24-hour patterns was electromagnetic radiation from space -- the Milky Way galaxy, specifically. Jansky announced his findings in 1933, and radio astronomy was born. This is a radio telescope interpretation of the spiraling white wheel we call our home galaxy. Next, you'll see a form of heat-based imaging.
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Infrared thermography -- it's not just for pit vipers and movie monsters (though an undeniably large source of public familiarity with thermal imaging is the 1987 action/horror film Predator, starring Arnold Schwarzenegger, in which a bloodthirsty alien hunter sees the world through heat signatures). In the real world, thermography can be used to detect everything from heat leaks in HVAC systems to fires in buildings.
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This picture was generated by the Thermal Emission Imaging System (THEMIS) -- an imaging tool carried aboard the 2001 Mars Odyssey orbiter. THEMIS used thermal imaging to collect data about the mineral makeup of the surface of Mars. Next, you'll see a medical imaging technology.
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Above is a gamma camera, also known as a scintillation camera. The gamma camera is a form of nuclear imaging that relies on the ingestion of a radioactive tracer substance, which can be swallowed, injected, inhaled or otherwise consumed, depending on which body system is being investigated. Next, you'll see one of the more recent popular imaging technologies in medicine.
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Like the gamma camera, a positron emission tomography (PET) scan uses radioactive tracers to map the interior functions of the body. While X-rays, CT scans and MRIs tend to focus on internal structure, locating tumors, fractures, lesions and other physical objects, the PET scan charts the function of internal organs -- not just what your internal organs look like, but what they are doing moment to moment. Next, you'll see a PET image of the brain.
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This is your brain on radioactive tracer. A doctor named Michael E. Phelps invented the PET camera in the early 1970s, completing the first working model in 1974. By the end of the 1990s, the device had become a popular tool for diagnostic imaging. Next, see a new spin on the penetrating power of X-rays.
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Medical X-rays have been used to scope out our insides ever since Wilhelm Röntgen stuck his wife's hand in front of a potentially dangerous beam of unknown radiation, but a more recent development has been the computed tomography (CT) scan, also known as the computed axial tomography (CAT) scan. These machines first appeared on the scene in the mid-1970s. See the output of one of these scans on the next page.
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Yes, this is a real diagnostic image for medical use, not a Halloween decoration. A standard X-ray radiograph snatches an image of the body in two dimensions, showing the composition of tissue along a single plane. CT scans, on the other hand, surround the body with X-ray transmissions, creating a digital model of the subject based on data from hundreds of angles. This data is processed by a powerful computer and turned into a comprehensive image like the one above.
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Though it looks like something from the set of Star Trek, most modern hospitals have one of these futuristic body tunnels. In reality, this is a magnetic resonance imaging (MRI) machine, which is a painless, noninvasive technology for scanning the inside of the body. First patented in 1974 by an American doctor named Raymond Damadian, the MRI machine has become a favored method of diagnosing brain tumors, strokes and other internal complications.
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MRIs return highly accurate readouts of internal body tissues without penetrating the skin or exposing the body to the potential dangers of ionizing radiation. Inside each MRI machine is a huge magnet -- usually a superconducting magnet, the titanic force of which makes it incredibly dangerous to, say, bring metal jewelry, pacemakers or belt buckles into the MRI room. This magnet creates the conditions for internal imaging by causing nearly all of the hydrogen atoms in the body to align in unison along with the magnet's polarity.
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One subsequent development in the field of MRI has been the growth of functional magnetic resonance imaging (fMRI), which traces oxygenated blood flow in the brain. This recent development has great potential for neurological research, as a comprehensive picture of this kind can tell us which parts of the brain are being used at any given time. This information can give us a concrete image of the anatomical nature of, for example, happiness, terror, or the impulse to tell a lie.
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In the post-9/11 world, almost everyone is serious about airport security. The U.S. Transportation Safety Authority has recently embraced the use of full-body security scanners as one of the primary ways of ensuring no one gets onto a plane carrying weapons or explosives. The particular scanner shown above is a backscatter X-ray, which is an extremely accurate new technology that produces an image based on the subject's material propensity to scatter beams of X-ray photons.
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Like backscatter X-ray machines, millimeter wave scanners produce detailed full-body images of passengers, but they do it with ultrahigh-frequency millimeter wave radiation rather than standard X-rays.
Now that you've seen our Imaging Technology Pictures, check out our Big Myths of Everyday Science Pictures!
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