Peeping into Human Body
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Our bodies communicate to us clearly and specifically, if we are willing to listen to them. - Shakti Gawain |
Introduction
Perhaps the greatest mystery of all is the human body. Its nearly 100 trillion cells coordinate their efforts to allow us to move, eat, think and feel.
The history of medical diagnosis began from the enlightened days of Hippocrates in ancient Greece but is far from perfect despite the enormous bounty of information made available by medical research including the sequencing of the human genome. The practice of diagnosis continued to be dominated by theories set down in the early 1900s.
Before a device made available to peep into the body, medical diagnosis, was more of an art, and of little science. The physician could measure body temperature, blood pressure, pulse rate, and a few simple chemical attributes of blood and urine, and used it for the diagnosis. Subtle aspects of a patient's appearance, physical and psychological behaviours commonly provided important clues. But a doctor often had no way to know what was going on within the body, unless the body is cut open. All of that changed overnight in November 8, 1895, when Roentgen began observing and documenting X-rays while experimenting with vacuum tubes.
G.C. Röntgen discovered mysterious rays capable of passing through the human body. Because of their unknown nature, he called them X-rays. Word of this wonder spread like wildfire, and the experiment was easy to reproduce. Within months, physicians throughout the world were using X-ray images to extract shrapnel and set broken bones.Roentgen had discovered "a new kind of ray, " as he described them, and in so doing he had created a splendid window for looking within the living body.
In 1953, the structure of DNA was solved by J. Watson, a biologist, and F. Crick, a physicist, thanks to the use of X-rays.
The name X-rays stuck, although (over Röntgen's great objections), many of his colleagues suggested calling them Röntgen rays.
The History
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My body is a bulletin board, transmitting my condition. ~Terri Guillemets
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Physicist Johann Hittorf (1824 - 1914) observed that the tubes with energy rays extending from a negative electrode. These rays produced a fluorescence when they hit the glass walls of the tubes. In 1876 the effect was named "cathode rays" by Eugen Goldstein. Later, English physicist William Crookes investigated the effects of energy discharges on rare gases, and constructed what is called the Crookes tube. It is a glass vacuum cylinder, containing electrodes for discharges of a high voltage electric current. He found, when he placed unexposed photographic plates near the tube, that some of them were flawed by shadows, though he did not investigate this effect.
In April 1887, Nikola Tesla began to investigate X-rays using high voltages and vacuum tubes of his own design, as well as Crookes tubes. The principle behind Tesla's device is nowadays called the Bremsstrahlung process, in which a high-energy secondary X-ray emission is produced when charged particles (such as electrons) pass through matter. By 1892, Tesla performed several such experiments, but he did not categorize the emissions as what were later called X-rays, instead generalizing the phenomenon as radiant energy. He did not publicly declare his findings nor did he make them widely known. His subsequent X-ray experimentation by vacuum high field emissions led him to alert the scientific community to the biological hazards associated with X-ray exposure.
In 1892, Heinrich Hertz began experimenting and demonstrated that cathode rays could penetrate very thin metal foil (such as aluminium). Philipp Lenard, a student of Heinrich Hertz, further researched this effect. He developed a version of the cathode tube and studied the penetration by X-rays of various materials. Philipp Lenard, though, did not realize that he was producing X-rays. Hermann von Helmholtz formulated mathematical equations for X-rays. He postulated a dispersion theory before Röntgen made his discovery and announcement. It was formed on the basis of the electromagnetic theory of light (Wiedmann's Annalen, Vol. XLVIII). However, he did not work with actual X-rays.
X-rays were discovered in 1895 by the German Physicist Wilhelm Roentgen. He was studying cathode rays produced by Crooke's tube when he noticed that a fluorescent screen across the room started to glow.X-rays are actually electromagnetic waves situated between ultraviolet light and gamma rays on the wavelength scale. Their wavelength is comparable to interatomic distances.Earlier that day, as the November dusk darkened the laboratory, he had noticed that whenever he made sparks in the tube, a fluorescent screen at the other end of the laboratory table glowed slightly. This was the signal that he had been looking for, the sign that invisible rays were being produced in the spark tube, crossing the room and striking the screen, producing the faint glimmer.To track the rays he had been putting pieces of card in their way, but the screen continued to glow whether the cards were there or not as if the rays were able to pass clean through them. He then tried to block the rays with metal but thin pieces of copper and aluminium were as transparent as the card had been.
He moved a piece of lead near to the screen, watching its shadow sharpen, and it was then that he dropped it in surprise: he had seen the dark skeletal pattern of the bones as his hand moved across the face of the screen. Still doubting what he saw he took out some photographic film for a permanent record. Röntgen had made one of the most monumental discoveries in the history of science: X-rays, and seen for the first time images that are today common in every hospital casualty department.
Six weeks later, on the Sunday before Christmas 1895, he invited his wife Bertha into the laboratory and took a shadow-graph of the bones of her hand with her wedding ring clearly visible. This is one of the most famous images in photographic history and propelled him within two more weeks into an international celebrity. The medical implications were immediately realised and the first images of fractured bones were being made by January 1896 even though none yet knew what the mystery rays were
With this discovery the peeping into body began.
The use of X-rays for medical purposes (to develop into the field of radiation therapy) was pioneered by Major John Hall-Edwards in Birmingham, England. In 1908, he had to have his left arm amputated owing to the spread of X-ray dermatitis. In the 1950s X-rays were first harnessed to produce an X-ray microscope.
Alternative Medical Imaging Techniques
There are many types of medical imaging techniques available to doctors and patients. Each techniques use slightly different technologies, allowing the doctor to focus on different aspects of the human body. The simplest and most common technique used to look into the human body is the X-Ray. X-Rays are high-powered beams of light that can pass through some parts of the human body, like skin, but are stopped by other parts, like bone. Using X-Rays to expose film (much the same way that visible light exposes film in a camera) allows doctors to examine the skeletal structure with ease.
X-Ray
Since Röntgen's discovery that X-rays can identify bony structures, X-rays have been developed for their use in medical imaging. Radiology is a specialised field of medicine that employs radiography and other techniques for diagnostic imaging. Indeed, this is probably the most common use of X-ray technology.
The use of X-rays are especially useful in the detection of pathology of the skeletal system, but are also useful for detecting some disease processes in soft tissue. Some notable examples are the very common chest X-ray, which can be used to identify lung diseases such as pneumonia, lung cancer or pulmonary oedema, and the abdominal X-ray, which can detect ileus (blockage of the intestine), free air (from visceral perforations) and free fluid (in ascites).
In some cases, the use of X-rays is debatable, such as gallstones (which are rarely radiopaque) or kidney stones (which are often visible, but not always). Also, Traditional plain X-rays pose very little use in the imaging of soft tissues such as the brain or muscle. Imaging alternatives for soft tissues are computed axial tomography (CAT or CT scanning), magnetic resonance imaging (MRI) or ultrasound.
X-rays are also used in "real-time" procedures such as angiography or contrast studies of the hollow organs (e.g. barium enema of the small or large intestine) using fluoroscopy. Angioplasty, medical interventions of the arterial system, rely heavily on X-ray-sensitive contrast to identify potentially treatable lesions.Radiotherapy, a curative medical intervention, now used almost exclusively for cancer, employs higher energies of radiation.
The basic production of X-rays is by accelerating electrons in order to collide with a metal target (tungsten usually). Here the electrons suddenly decelerate upon colliding with the metal target and if enough energy is contained within the electron it is able to knock out an electron from the inner shell of the metal atom and as a result electrons from higher energy levels then fill up the vacancy and X-ray photons are emitted. This causes the spectral line part of the wavelength distribution. There is also a continuum bremsstrahlung component given off by the electrons as they are scattered by the strong electric field near the high Z (proton number) nuclei.
X-rays with a wavelength approximately longer than 0.1 nm are called soft X-rays. At wavelengths shorter than this, they are called hard X-rays. Hard X-rays overlap the range of "long"-wavelength (lower energy) gamma rays, however the distinction between the two terms depends on the source of the radiation, not its wavelength: X-ray photons are generated by energetic electron processes, gamma rays by transitions within atomic nuclei.
The detection of X-rays is based on various methods. The most commonly known method are a photographic plate and a fluorescent screen.
The X-ray photographic plate is frequently used in hospitals to produce images of the internal organs and bones of a patient. The part of the patient to be X-rayed is placed between the X-ray source and the photgraphic plate to produce what is a shadow of all the internal structure of that particular part of the body being X-rayed. The X-rays are blocked by dense tissues such as bone and pass through soft tissues. where the X-rays strike the photographioc plate it turns black when it is developed. So where the X-rays go through "soft" parts of the body like organs and skin the plate turns black. Contrast compounds containing barium or iodinecan be injected in the artery of a particular organ. The contrast compounds strongly block the X-rays and hence the circulation of the organ can be more readily seen.
Another method of detecting X-rays is a fluorescent plate. In modern hospitals a special plastic sheet is used in place of the photographic plate. The plastic sheet is read by a scanning laser beam. The resultant image is then stored in a computer. The plastic sheet can be used over and over again.
Ultra Sonic
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The body says what words cannot. - Martha Graham |
Ultrasound imaging uses a completely different technology than X-Rays. An Ultrasound probe emits ultrasonic sound waves, sounds above the range of human hearing, into the body. While most of these ultrasonic sound waves travel straight through the body, a small amount reflect off the transition layers between different types of tissue. The echoes from these transmission layers are picked-up by the Ultrasound probe, fed into a computer and then rendered into a two-dimensional image. Ultrasound technology uses sound echoes to look into the human body much the same way bats and submarines use sound echoes to see.
Unlike the other imaging technologies we have discussed, ultrasonography does not involve electromagnetic radiation, such as gamma and X rays or light or radio waves. Ultrasound is a mechanical disturbance, rather, in which oscillations of 1 to 10 million hertz (Hz; cycles per second) travel through soft tissues and fluids. (Humans with excellent ears typically can hear in the range 20 to 20,000 Hz.) In ultrasound imaging, a narrow beam of pulses of very high-frequency sound energy is directed into the body and swept back and forth; pictures of organs, blood vessels, and other structures are created out of the waves reflected back
Ultraviolet Scanning
Ultraviolet, or UV light, is used for a variety of purposes from detecting flaws in materials to creating images of flowers, revealing patterns and contrasts that are only visible to the UV-sensitive eyes of insects. UV light is also used for medical diagnosis, and because the epidermal melanin selectively absorbs UV, an image can show the extent of Sun damage to the skin. The hottest and most active parts of the Sun radiate enormous amounts of UV light, creating dynamic portraits.
Thermal imaging
Using advanced data acquisition technology, the latest generation of infrared imager is ready to plug-and-play with a standard personal computer. Infrared imagers to the clinical and scientific field. With excellent spatial resolution, these imagers operate in the important 8-12 micron range. It is more reasonable in cost for the features and quality of images produced. Extensive image processing software routines are usally made available to provide a thorough analysis of the subject. The images are clean, clear and precise (They don't have the electronic noise or grainy appearance that occurs with many other infrared imagers). This means a better and more reliable signal. Each pixel is calculated specifically with a corresponding temperature value.
With the latest infrared thermal imager, it's very easy to evaluate the activities associated with heat emissions from a subject. This is an extremely important imaging process, and an objective, non-invasive physiological test. In a living subject such as a human being or animal, the changes in blood flow to an area result in a measureable thermal response (a local temperature difference). With a thermal image, this is observed in a color gradation (i.e. from darker to lighter, as the temperature increases).
Thermal imaging is a physiological test for the adjunctive evaluation of:
EEG (Electroencephalograph)
Although not a "brain scan" as the term is usually used, the EEG, or electroencephalograph, deserves mention as one of the first - and still very useful (without a physical peep), - ways of non-invasively observing human brain activity. An EEG is a recording of electrical signals from the brain made by hooking up electrodes to the subject's scalp. These electrodes pick up electric signals naturally produced by the brain and send them to galvanometers (instruments that detect and measure small electric currents) that are in turn hooked up to pens, under which graph paper moves continuously. The pens trace the signals onto the graph paper.
Endoscopy
Physicians had long used rigid tubes, mirrors, and candles or sunlight to peer down the throat and along other bodily passageways, but it was the introduction of fiber optics in the 1950s that transformed the endoscope into a powerful modern clinical tool for direct clinical inspection.
Light entering the tip of a flexible glass fiber, a tenth of a millimeter or so across, will reflect again and again off its interior surface, like a stone skipping on water, and can travel great distances with little loss of intensity. A bundle of thousands of fibers, with lenses at the two ends, can carry a clear and sharp optical image. A modern endoscope consists of such a bundle, along with another bunch of fibers that bring in bright light to illuminate the region being viewed. In addition, it may have channels to convey gases or liquids in or out, or perhaps even a mechanical device, such as a biopsy forceps, at its business end. Endoscopy can be employed wherever there is an opening into the body, whether naturally occurring or surgical, and the equipment has become highly specialized for various applications.
As will be apparent from the case studies in this book, endoscopy may pick up where other imaging techniques leave off. Fluoroscopy may indicate the presence of a tumor of the esophagus, for example, but an endoscope then obtains the biopsy needed for confirmation (figure 16). Likewise, after angiography reveals a partial blockage of a coronary artery, a high-power laser beam carried by a special fiber optic bundle of an endoscope may burn it away.
An area where endoscopy is receiving much attention is small-incision-hole surgery. The endoscope enters the body through a cut as little as one centimeter long, and it either brings in the necessary surgical instruments itself or guides their use. While such operations are much less traumatic to the patient and result in shorter hospital stays (both of which reduce cost), the procedures require additional training for the surgeon.
What is CT Scanning of the Body?
CT or CAT, Computerized Axial Tomography, scans also use X-rays but in a slightly more complicated way. A CAT scanner consists of a donut shaped ring containing numerous X-Ray tubes that shoot out beams of X-Rays. Patients slide through the donut hole while X-Ray detectors that are also around the donut ring record the X-Rays after they have traveled through the body. The computerized component of CAT scans involves interpreting all the X-Ray signals and combing them into a coherent image. Because CAT scanners only take X-Ray pictures of your body in thin slices, computers are needed to combine each thin slice into a comprehensive three-dimensional image. This technique of looking at the body in thin slices is called Tomography. CAT scans image the body in slices perpendicular to the axis stretching from the feet to the head. These slices fall in the axial plane of the body.
CT (computed tomography), sometimes called CAT scan, uses special x-ray equipment to obtain image data from different angles around the body and then uses computer processing of the information to show a cross-section of body tissues and organs.
CT imaging is particularly useful because it can show several types of tissue—lung, bone, soft tissue and blood vessels—with great clarity. Using specialized equipment and expertise to create and interpret CT scans of the body, radiologists can more easily diagnose problems such as cancers, cardiovascular disease, infectious disease, trauma and musculoskeletal disorders.
In many ways CT scanning works very much like other x-ray examinations. Very small, controlled amounts of x-ray radiation are passed through the body and different tissues absorb radiation at different rates. With plain radiology, an image of the inside of the body is captured when special film is exposed to the absorbed x-rays. With CT the film is replaced by an array of detectors that measure the x-ray profile.
Inside the CT scanner is a rotating gantry that has an x-ray tube mounted on one side and an arc-shaped detector mounted on the opposite side. An x-ray beam is emitted in a fan shape as the rotating frame spins the x-ray tube and detector around the patient. Each time the x-ray tube and detector make a 360-degree rotation and the x-ray passes through the patient's body, the image of a thin section is acquired. During each rotation the detector records about 1,000 images (profiles) of the expanded x-ray beam. Each profile is then reconstructed by a dedicated computer into a two-dimensional image of the section that was scanned. Multiple computers are typically used to control the entire CT system.
MRI Scan
MRI, or Magnetic Resonance Imaging, uses magnetic fields to peer into the human body. The MRI machine contains a very large magnet that surrounds the patient with an intense magnetic field. When patients are immersed inside this magnetic field all of the billions and billions of hydrogen atoms inside their body align with it. Inside the MRI machine, radio frequency pulses are applied to specific parts of the body to excite some of these hydrogen atoms. Images are created based on how the exited hydrogen atoms lose their energy. These images are fed into a computer to generate an incredibly detailed look inside the human body.
How does a patient obtain the results of the MRI scan?
After the MRI scanning is completed, the computer generates visual images of the area of the body that was scanned and these images are transferred to film (hard copy). This film is given to a radiologist, a physician who is specially trained to interpret images of the body reproduced on film. The interpretation is transmitted in the form of a report to the practitioner who requested the MRI scan. The practitioner can then discuss the results with the patient and/or family.
Magnetic resonance imaging (MRI) not only reveals the structural details of the various organs, as does CT, but it also provides information on their physiological status and pathologies, as does nuclear medicine. And with MRI, there is no radiation risk to the patient, since no X-ray or gamma-ray energy is involved. Instead, MRI uses magnetic fields and radio waves to probe the (nonradioactive) nuclei of hydrogen atoms occurring naturally in the water molecules within and around cells.
Imagine a compass needle (which itself is a tiny bar magnet) aligned comfortably along the Earth's magnetic field. Now, in your mind's eye, twist it through 180 degrees, so that it points south, and then release it. It will flop back over, oscillate a few times with diminishing swings, and eventually come to rest pointing north again (figure 14a). The amount of time this settling-down process takes is known as the relaxation time.
Future
Scientists are developing newer MRI scanners that are smaller, portable devices. These new scanners apparently can be most useful in detecting infections and tumors of the soft tissues of the hands, feet, elbows, and knees. The application of these scanners to medical practice is now being tested.
Advantages/Disadvantages
PET or Positron Emission Tomography
Nuclear medicine began in the late 1930s when radioactive iodine was employed to investigate thyroid disease, and now it can contribute valuable information on nearly every organ. It has also worked well in the imaging of some tumors, providing an especially sensitive test of the spread of cancer from one organ to another. For cardiac patients, it furnishes quantitative assessments of the heart's capacity to pump blood.One area where standard nuclear medicine has fallen largely out of favor (having been displaced by CT) is in brain imaging. Ironically, that's where posit ron emission tomography (PET) made its first important inroads.
PET or Positron Emission Tomography scans have become an important aspect of medical imaging and diagnoses, allowing doctors to look into the human body as never before. PET scans are different from other medical imaging techniques because they do not actually look at the body itself. Instead, PET scans look at bodily process by detecting the decay products from radioactive tracers injected into the body. Radioactive tracers are designed to mimic naturally occurring substances and tend to deliver less radiation than an X-Ray.
When the radioactive tracers decay inside the body, they release a positron, the antimatter equivalent of electrons. When the positron encounters one of the billions and billions of electrons inside your body, it annihilates in a flash of light called gamma rays-it is these gamma rays that are the positron emissions which PET scanners detect. The donut ring of the PET scanner is lined with gamma ray detectors.
How is PET different?
PET scans are different from all the other types of medical scans because they never actually look at the human body itself. Instead, PET scans use radioactive chemicals to look at different processes inside the human body. The actual PET scan machines are similar to CAT scan machines as they are both donut shaped and use axial tomography. But unlike CAT scanners, the donut ring of PET scanners is lined only with detectors. These detectors are used to pick up positron emissions.
But what on earth is a positron? The simplest answer is that a positron is an anti-electron. So what is an anti-electron? There are billions and billions of electrons in your body. They are the negatively charged parts of atoms which orbit the positively charged nucleus. Every one of your atoms has electrons and electrons are considered to be what physicists call matter. Positrons, or anti-electrons, are antimatter-having many of the same properties as matter but with opposite electric charges. An electron is negatively charged while the positron is positively charged (electrons are sometimes called negatrons to differentiate them from positrons). The important thing about positrons is that when they encounter electrons, they annihilate in bursts of light called gamma rays. These gamma rays are the positron emissions that the PET scanners detect.
Before undergoing a PET scan, patients are given radioactive tracers. When these radioactive tracers decay, they emit positrons that soon annihilate with one of the billions of electrons inside your body to produce gamma rays. These gamma rays are always emitted back-to-back, or in the opposite direction from each other. This allows PET scanners to extrapolate where in the body the gamma rays originated.
Radioactive Tracers and PET Scans
What makes PET scans so unique is that they can be used to look at a number of physiological processes taking place inside the human body. Specific radioactive tracers allow doctors to study different biological processes. The radioactive tracers that PET scans use are manufactured to mimic naturally occurring substances already used by the body. As the body incorporates the radioactive tracers into its systems, the PET scan can monitor their progress and examine the specific bodily processes that use the tracer. Radioactive tracers are designed to deliver a minimum amount of radiation to the patient, often less than would normally be received in an X-Ray.
High-resolution Ultrasonic Transmission Tomography (HUTT)
Vasilis Marmarelis, a professor of biomedical engineering at the Viterbi School, presented HUTT images of animal organ tissue(Sheep Kidney) in San Diego at the 28th International Acoustical Imaging Symposium on March 21st, 2005. According to Marmarelis, the key features distinguishing HUTT from all previous ultrasound imaging systems is the use of multi-band analysis with sub-millimetre ultrasonic transducers in transmission mode, rather than the commonly used echo mode, to create the 3D image.
High-resolution Ultrasonic Transmission Tomography (HUTT) is a novel 3D imaging technology being developed at the University of Southern California's Viterbi School of Engineering. The HUTT system employs extremely short ultrasonic wave pulses (about 250 nanosecond) of 4-12 megahertz frequency. Unlike regular ultrasound, the transmitted pulses come from a group of small ultrasonic transducers. Also unlike regular ultrasound, these pulses are picked up by a parallel array of receivers that is located on the opposite side of the tissue that is being visualised. This modality can produce "3D images" of soft tissue that are superior to those produced by existing commercial X-ray, ultrasound or MRI units.
According to Professor Marmarelis, HUTT offers nearly order-of-magnitude improvement in resolution of structures in soft tissue, i.e., 0.4 mm, compared to 2 mm for the best alternatives. Several other features promise to make the technology a scientific and clinical tool of great power. Robust algorithmic tools enable HUTT to differentiate separate types of tissue based on their distinctive "frequency-dependent attenuation" profiles, that should allow clinicians to distinguish malignant lesions from benign growths in a non-invasive and highly reliable manner.
Scans can be performed in a matter of a few minutes and because they are ultrasonic, they do not use potentially harmful ionizing radiation. The system requires a minimum of special pre-scan procedures and appears likely, in clinical use, to be more comfortable for patients than alternatives.
He explains that in traditional handheld ultrasound systems, sound waves are broadcast into the tissue and the echoes produce an image of the reflecting interfaces - that is, the sound transmitter and the receiver are both on the same side of the sample.
While conventional ultrasound works by recording echoes that bounce back from tissues HUTT works by recording the sound that passes all the way through tissue. Since 2000 times more sound passes through than echoes the amount of sound signal that can be recorded using HUTT is much greater.
However, only a tiny fraction of the transmitted sound comes back as echo on soft tissues, while a much larger fraction (about 2000 times bigger) is transmitted through the soft tissue. Using the sound transmitted through tissue allows the formation of better images with greater clarity and resolution.
A handheld apparatus cannot objectively locate objects in 3D space (in a fixed-coordinate system), but only allows the user to subjectively observe where an object is in relation to other observable structures. Therefore, it is operator-dependent.
The HUTT system transmits an extremely short ultrasonic pulse (about 250 nanoseconds) of 4-12 MHz and picks up the pulse on the other side after it has travelled through the imaged object.
The transmitted pulses come from an array of very small ultrasonic transducers of sub-millimetre dimensions. A parallel array of transducers on the other side receives the pulses after they travel through the imaged tissue.
A coding/decoding signal scheme recognises a small 'sweet spot' of the signal coming from the opposite transducer, and only that transducer, and ignores all other pulses transmitted by neighouring transducers.
The transducer can distinguish the right signal from the right transducer by using coding that is almost identical to that used by a mobile phone to detect signals sent to its number - and its number only - from the flood of electronic signals on the air at any given time.
When the transducer captures the signal, it is handled by signal processing algorithms, specially developed by Marmarelis' group, to form the multi-band images.
Different kinds of tissue allow slightly more, or slightly less of the pulse through - this attenuation varies according to the type of tissue and the frequency of the pulse.
The two arrays, transmitter and receiver, are mounted on opposite sides of a drum that spins as it rises around the object (which is suspended in water), creating a stack of tomographic image slices that visualisation algorithms turn into 3D images.
The nanosubmarine - Fiction
Fantastic Voyage by Isaac Asimov - Four men and a woman are reduced to a microscopic fraction of their original size, sent in a miniaturized atomic sub through a dying man's carotid artery to destroy a blood clot in his brain. If they fail, the entire world will be doomed.
A miniature submarine that could navigate inside a human body would be a wonderful device for studying how a body works and for making repairs. In this section, various nano-scale components that might be useful in a miniature submarine will be considered. One of the conclusions of this analysis is that the capabilities of a submarine that is small enough to travel anywhere in the body would be rather limited. The most complicated submarines would in many ways resemble the drug delivery systems now being developed.
The Nano Camera - Reality
A nanodevice that often appears in science fiction is a nanocamera. This is used to view the inside of the body or in other confined spaces where an ordinary camera would not fit. Unfortunately, it is not possible to make such a camera using conventional far field optics. Light sources and light detectors can be made very small; a single molecule is large enough to serve as a simple light source or light detector. However, the amplitude of a light wave does not change over a distance much shorter than the wavelength of the light. This means that if detectors are placed together spaced more closely than a wavelength, they will all measure the same light intensity and no image will be formed. The wavelength of visible light is about one half micron so the detectors that make up a camera should be spaced at least this far apart. For an image consisting of 1000 × 1000 pixels, the camera would have to be about one half a millimeter on a side. This is small but clearly visible to the naked eye. It is too large to pass through the smallest blood vessels in the body which have a diameter of 2-3 microns.
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The body is a marvelous machine...a chemical laboratory, a power-house. Every movement, voluntary or involuntary, full of secrets and marvels! Theodor Herzl (1860 - 1904) |
Using a camera of any size it is not possible to view something with the dimensions of a few nanometers using visible light. Since the amplitude of the light cannot change on a scale shorter than the wavelength, any nanoscale object viewed with visible light will be no more than a shadowy blur. One way to get around this problem is to use shorter wavelengths. X-rays have short enough wavelengths but are difficult to focus. An electron microscope can have a resolution of a few nanometers. However, there are no nanoversions of imaging systems that use these short wavelengths and x-ray photon or energetic electrons have enough energy to damage a nanoscale structure. Building a nanoscale camera that uses short wavelengths does not seem feasible.
In August last year, scientists from Osaka University unveiled the world’s tiniest sculptures, bulls the size of a single blood cell, made using lasers. That was a dramatic demonstration that techniques for miniaturising machines are feasible, perhaps ultimately, down to the size of molecules that could fit inside cells.
Researchers from universities of Glasgow, Edinburgh and Strathclyde are working on robots about the size of a pill, that, when swallowed could measure temperature, acidity and oxygen concentration in the stomach, and the signals transmitted to an external receiver. Other researchers have developed a minute camera in a pill that can transmit pictures of all parts of the gut. But these miniaturisations are still far from the molecular scale of nanometres (a billionth of a meter, and purists would not include those devices in the realm of nanotechnology. All the same, the possibilities seem endless. "There is plenty of room at the bottom," so said quantum physicist Richard Feynman in an after-dinner speech in 1959 that inaugurated the age of miniaturisation that leads ineluctably towards nanotechnology.The microbull-sculpting scientists in Osaka have also built the smallest micromechanical systemever, a spring whose arm is only 0.3microns wide, which would just quality as a nanodevice. (A micron is a millionth of a metre.)
Conclusion
The final peep?
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The human body is a machine which winds its own springs. ~Julien Offroy de la Mettrie, L'Homme Machine |
Among the greatest of its ancient writings is the Sushruta Samhita, which describes the tradition of surgery in Indian medicine. In the book’s 184 chapters, 1,120 conditions are listed, including injuries and illnesses relating to ageing and mental illness. For instance, there are accounts of 76 eye conditions, 51 of which were treated surgically. The book also describes 101 blunt and 20 sharp surgical instruments, many of which are surprisingly similar to instruments used today.
Hippocrates did not dissect the human body; the observations he made nearly five centuries before the birth of Christ were cursory and based almost solely on sight. Leonardo da Vinci and Michelangelo, not in the name of science, but in the name of Renaissance art, made their study by dissecting human body. They could accurately depict the physiology. By examining the human body to "advance the glory of God," da Vinci and Michelangelo became mankind's first great dissectors. The artists performed an estimated 500 to 600 dissections each. But when we explore health through a peep into the human body, it is important to know the correlation, to every minute detail. The very peep should not destroy the biology.
Vedic seer considers the human body to be an exact replica of the universe.
In The Upanishads, one of the great ancient yogic texts, we are reminded:
“As is the atom, so is the universe.
As is the human body, so is the cosmic body.
As is the human mind, so is the cosmic mind.
As is the microcosm, so is the macrocosm.”
From the atom to the cosmos, Nature’s laws and order are reflected. All of life is connected to this same order: the human body, our homes, and the cosmos.
The human intellect, the magnitude of which separates the human from all other animals, developed slowly over the entire four million years or more of the human development.To the human, however, in his need to establish his place and purpose in the universe, the most important material in observation is biological. It is only here that the human can learn to understand himself, an understanding that is vital to his survival.
