Ultrasonic energy was first applied to the human body for medical purposes by Dr. George Ludwig at the Naval Medical Research Institute, Bethesda, Maryland in the late 1940s. The first demonstration of color Doppler was by Geoff Stevenson, who was involved in the early developments and medical use of Doppler shifted ultrasonic energy.

This application is an ultrasonic based diagnostic imaging technique used to see muscles and internal organs, their size, structures, and possible pathologies or lesions. Diagnostic sonographic scanners usually operate in the frequency range of 2 to 18 megahertz, hundreds of times greater than the limit of human hearing. This frequency is a suitable choice because of a trade-off between spatial resolution of the image and imaging depth: lower frequency produce less resolution but image deeper into the body.

It is used to perform diagnosis or therapeutic procedures with the guidance of sonography. Sonographers use hand-held probe (called a transducer) that is placed directly on and moved over the patient. A water-based gel is used to couple the ultrasound between the transducer and patient. Soft tissues of the body can be imaged by sonography means. Frequency of (7-18 MHz) is used for superficial structures (muscles, tendons, testes, breast and the neonatal brain). Lower frequency (1-6 MHz) is used for deeper structures such as liver and kidney.

Medical sonography is used in:
• Cardiology
• Endocrinology
• Gastroenterology
• Gynaecology
• Obstetrics
• Ophthalmology
• Urology, to determine, for example, the amount of fluid retained in a patient's bladder.
• Musculoskeletal, tendons, muscles, nerves, and bone surfaces
• Intravascular ultrasound (e.g. ultrasound guided fluid aspiration, fine needle aspiration, guided injections)
• Intervenional; biopsy, emptying fluids, intrauterine transfusion (Hemolytic disease of the newborn)
• Contrast-enhanced ultrasound

Therapeutic applications use ultrasound to bring heat or agitation into the body. Uses higher energy than in diagnostic ultrasound and frequencies used are also very different.

• Clean teeth in dental hygiene
• Used to generate regional heating in biological tissue, e.g. in occupational therapy, physical therapy and cancer treatment.
• Focused ultrasound may be used to generate highly localized heating to treat cysts and tumors (benign or malignant). Can also be used to break up kidney stones by lithotripsy.
• Cataract treatment by phacoemulsification.
• Stimulate bone growth
• Potential to disrupt the blood-brain barrier for drug delivery.

In medicine, a prosthesis is an artificial extension that replaces a missing body part. Body parts such as legs, arms, hands, feet, and others can be replaced. Prostheses are typically used to replace parts lost by injury or missing from birth or to supplement defective body parts. In addition to the standard artificial limb for every day use, many amputees have special limbs and devices to aid in the participation of sports and recreational activities. The first experiment with a healthy individual appears to have been that by the British scientist Kevin Warwick. On 14/03/2002 an implant was interfaced directly into Warwick's nervous system. The electrode array contained around 100 electrodes, was placed in the median nerve. The signals produced were detailed enough that a robot arm was able to mimic the actions of Warwick's own arm and provide a form of touch feedback again via the implant.

In order for a robotic prosthetic limb to work, it must contain some components to integrate it into the body's function. Biosensors detect signals from the user's nervous or muscular systems. It then sends this information to the controller located inside the device, and processes feedback from the limb and actuator sends it to the controller. Examples include wires that detect electrical activity on the skin, needle electrodes implanted in muscle, or solid-state electrode arrays with nerves growing through them. Mechanical sensors process aspects affecting the device and relay this information to the biosensor or controller. Examples: force meters and accelerometers. The controller is connected to the user's nerve and muscular systems and in the device. It sends intention command from the user to the actuators of the device, and interprets feedback from the mechanical and biosensors to the user. The controller is responsible for the control of the movements of the device. An actuator mimics the actions of a muscle in producing force and movement. Examples include a motor that aids or replaces original muscle tissue.

An Artificial pacemaker is a medical device which uses electrical impulses contacting the heart muscles, to regulate the beating of the heart. Modern pacemakers usually have multiple functions. The most basic form monitors the heart's native electrical rhythm either because the heart's native pacemaker is not fast enough, or there is a block in the heart's electrical conduction system. Modern pacemakers are externally programmable and allow the cardiologist to select the optimum pacing modes for individual patients. In 1889 J A McWilliam reported in the British Medical Journal of his experiments in which application of an electrical impulse to the human heart in asystole caused a ventricular contraction and that a heart rhythm of 60-70 beats per minute could be evoked by impulses applied at spacings equal to 60-70/minute. Some combine a pacemaker and implantable defibrillator in a single implantable device. When the pacemaker doesn't sense a heartbeat within a normal beat-to-beat time period, it will stimulate the ventricle of the heart with a short low voltage pulse. This sensing and stimulating activity continues on a beat by beat basis.

There are four methods of pacing:

Percussive Pacing

Percussive Pacing is the use of the closed fist, usually on the left lower edge of the sternum over the right ventricle. It is also known as Transthoracic Mechanical Pacing. This is old method an old uses for a limited time until the patient receives an electrical pacemaker.

Transcutaneous pacing

Transcutaneous pacing for the initial stabilization of hemodynamically significant bradycardias of all types. It is also known as external pacing. It is an emergency procedure that acts as a bridge until transvenous pacing or other therapies can be applied as it is not reliable for a long period.

Transvenous pacing (temporary)

Transvenous pacing, when used for temporary pacing, is an alternative to transcutaneous pacing. It can be kept in place until a permanent pacemaker is implanted or until there is no longer a need for a pacemaker and then it is removed.

Permanent pacing

Permanent pacing with an implantable pacemaker involves transvenous placement of one or more pacing electrodes within a chamber, or chambers, of the heart .The pacemaker generator is an hermetically sealed device containing a power source, usually a lithium battery, a sensing amplifier which processes the electrical manifestation of naturally occurring heart beats as sensed by the heart electrodes, the computer logic for the pacemaker and the output circuitry which delivers the pacing impulse to the electrodes. Most commonly, the generator is placed below the subcutaneous fat of the chest wall, above the muscles and bones of the chest. However, the placement may vary on a case by case basis. The outer casing of pacemakers is so designed that it will rarely be rejected by the body's immune system. It is usually made of titanium, which is inert in the body.

Leksell Gamma Knife (or Gamma Knife). It is a neurosurgical device used to treat brain tumors with radiation therapy. Lars Leksell, a Swedish neurosurgeon, invent this device in 1967 at the Karolinska Institute in Sweden.

The device contains 201 cobalt-60 sources of approximately 30 curies (1.1 TBq) each, placed in a circular array in a heavily shielded assembly. It aims gamma radiation through a target point in the patient's brain. A specialized helmet is worn by the patient that is surgically fixed to their skull so that the brain tumor remains stationary at target point of the gamma rays. The device uses high doses of radiation to kill cancer cells and shrink tumors, delivered with surgical precision to avoid damaging healthy brain tissue. The ability to accurately focus many beams of high-intensity gamma radiation to converge on one or more tumors is the key to the success of Gamma Knife surgery.

Gamma Knife surgery has proved effective for thousands of patients with benign or malignant brain tumors, vascular malformations such as an arteriovenous malformation (AVM), pain or other functional problems. The procedure is less invasive than alternative surgeries. However, the risks of Gamma Knife are radiation necrosis, secondary malignancy caused by the radiation (ie: formation of new tumor), hemorrhage, infection from the placement of the stereotactic headframe, paralysis and death.

A heart rate monitor is a device that allows a user to determine and measure his or her heart rate in real time. A heart rate monitor device usually consists of two elements which are a chest strap transmitter and a wrist receiver. There are varieties of the receivers design with advanced features. The Polar Electro company's website states they invented the first accurate, wireless electrocardiogram heart rate monitor in 1977, to be used as a training tool for the Finnish National Cross Country Ski Team. Textronics Inc. introduced the first garment with integrated heart sensors in the form of a sports bra in December 2005.

Furthermore, strapless heart rate monitors are available too. However, they lack of some features of the original design. Besides that, the chest strap has electrodes in contact with the skin to monitor the electrical voltages in the heart.

Computed tomography (CT) is a medical imaging method employing tomography. Digital geometry processing is used to generate a three-dimensional image of the inside of an object from a large series of two-dimensional X-ray images taken around a single axis of rotation. Computed tomography was originally known as the "EMI scan" as it was developed at a research branch of EMI, a company best known today for its music and recording business. CT produces a volume of data which can be manipulated, through a process known as windowing, in order to demonstrate various structures based on their ability to block the X-ray beam. Modern scanners allow this volume of data to be reformatted in various planes or even as volumetric (3D) representations of structures.

A method to represent a single slice of the body on the radiographic film was proposed by Italian radiologist Alessandro Vallebona. The idea is based on simple principles of projective geometry: moving synchronously and in opposite directions the X-ray tube and the film, which are connected together by a rod whose pivot point is the focus; the image created by the points on the focal plane appears sharper, while the images of the other points annihilate as noise. This is only marginally effective, as blurring occurs only in the "x" plane. There are also more complex devices which can move in more than one plane and perform more effective blurring. Sir Godfrey Newbold Hounsfield in Hayes, United Kingdom invented the first commercially viable CT scanner at EMI Central Research Laboratories using X-rays. Allan McLeod Cormack of Tufts University, Massachusetts, USA independently invented a similar process, and both Hounsfield and Cormack shared the 1979 Nobel Prize in Medicine.

CT has become an important tool in medical imaging to supplement X-rays and medical ultrasonography. Although it is still quite expensive, it is the gold standard in the diagnosis of a large number of different disease entities. CT can also be used for preventive medicine or screening for disease. CT can detect chest problems, diagnose pulmonary embolism, detect cardiac problems, investigate acute abdominal pain and image complex fractures.

X-ray is a form of electromagnetic radiation. It has a wavelength in the range of 10 to 0.01 nanometers, corresponding to frequencies in the range 30 PHz to 30 EHz. The first person to record an experiment which produced X-rays was William Morgan (1750 - 1833) presenting in 1785 his paper Electrical Experiments Made in Order to Ascertain the Non-Conducting Power of a Perfect Vacuum.

X-ray is primarily used for diagnostic radiography and crystallography. X-rays can be dangerous as they are a form of ionizing radiation. Besides that, X-rays can be used to identify bony structures. Thus, X-rays are especially useful in the detection of pathology of the skeletal system. Furthermore, detecting some disease processes in soft tissue is also apart of its usage. Due to the X-rays usage in medical imaging, X-rays have been developed to a much advanced technology. X-ray crystallography in which the pattern produced by the diffraction of X-rays which can be seen used by Rosalind Franklin to discover the double helix structure of DNA. Other than that, X-ray astronomy, which is a branch of astronomy, which deals with the study of X-ray emission from celestial objects.

Besides that, X-ray microscopic analysis, which uses electromagnetic radiation in the soft X-ray band to produce images of very small objects. X-ray fluorescence is a technique in which X-rays are generated within a specimen and detected. The underdrawing and pentimenti or alterations in the course of painting are revealed when the paintings are often being X-rayed.

Magnetic resonance imaging (MRI) is mainly used in medical imaging to visualize the structure and function of the body. MRI provides detailed images of the body in any plane. Furthermore, MRI has much greater soft tissue contrast than computed tomography (CT). Thus, this make it especially useful in neurological, musculoskeletal, cardiovascular, and oncological imaging. Besides that, there are many specialized MRI scans.

This includes the magnetic resonance spectroscopy which is used to measure the levels of different metabolites in body tissues. Besides that, the diffusion MRI measures the diffusion of water molecules in biological tissues. Other than that, magnetic resonance angiography (MRA) is used to generate pictures of the arteries and often used to evaluate the arteries of the neck and brain, the thoracic and abdominal aorta, the renal arteries, and the legs. Functional MRI (fMRI) measures signal changes in the brain that are due to changing neural activity. MRI is suitable for interventional radiology, where images produced by a MRI scanner are used to guide minimally-invasive procedures because there are lacks of harmful effects on the patient. Due to MRI's superior imaging of soft tissues, it is now being specialized to locate tumors within the body in preparation for radiation therapy treatments. Furthermore, current density imaging (CDI) endeavors to use the phase information from images to reconstruct current densities within a subject.

Magnetic resonance guided focused ultrasound (MRgFUS) therapy which involves the ultrasound beams focusing on a tissue which is guided and controlled using MR thermal imaging will cause the temperature within the tissue to rise more than 65°C that will eventually destroy it. Multinuclear imaging is primarily a research technique at present. However, potential applications include functional imaging and imaging of organs poorly seen on H MRI (e.g. lungs and bones) or as alternative contrast agents. Besides that, Susceptibility Weighted Imaging (SWI), is a new type of contrast in MRI different from spin density, T1, or T2 imaging. This method exploits the susceptibility differences between tissues and uses a fully velocity compensated, three dimensional, rf spoiled, high-resolution, 3D gradient echo scan. Other than that, there are also some active research in several new MRI technologies like magnetization transfer MRI (MT-MRI), diffusion tensor MRI (DT-MRI), Susceptibility Weighted Imaging MRI (SWI), and proton MR spectroscopy. This includes the recent research in to Dendrimer-enhanced MRI as a diagnostic and prognostic biomarker of sepsis-induced acute renal failure. Furthermore, there is research on additional developments based on SWI as an imaging biomarker for tumors, neurological and neurovascular diseases. Moreover, portable magnetic resonance instruments are also available for use in education and field research.

An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length. Optical fibers are widely used in fiber-optic communication (which permits transmission over longer distances and at higher data rates than other forms of communications.), used to form sensors and in medical field like for colonoscopy. Optical Fibers was first demonstrated in Paris in the 1840s by Daniel Colladon and Jacques Babinet.

How it works :

Light is kept in the optic fiber by total internal reflection. Fibers which support many propagation paths or transverse modes are called multimode fibers (MMF). Fibers which support only a single mode are called singlemode fibers (SMF). Multimode fibers generally have a large-diameter core, and are used for short-distance communication links or for applications where high power must be transmitted. Single mode fibers are used for most communication links longer than 200 meters. Joining lengths of optical fiber is more complex than joining electrical wire or cable. The ends of the fibers must be carefully cleaved, and then spliced together either mechanically or by fusing them together with an electric arc. Special connectors are used to make removable connections.

Medical uses:

Optical fiber is used as imaging optics in medical. A coherent bundle of fibers is used, sometimes along with lenses, for a long, thin imaging device called an endoscope, which is used to view objects through a small hole. Medical endoscopes are used for minimally invasive exploratory or surgical procedures (endoscopy).

Hemodialysis (also haemodialysis) is a method for removing waste products that is not needed by our body such as potassium and urea, as well as free water from the blood .This happens because the kidneys are in renal failure (not functioning). Hemodialysis is one the methods to threat renal replacement therapies. First to present the principles of solute transport across a semi permeable membrane was Thomas Graham of Glasgow, in 1854.

Hemodialysis can be an outpatient or inpatient therapy. Routine hemodialysis is conducted in a dialysis outpatient facility either in a hospital or a clinic. Rarely hemodialysis is done at home. Dialysis treatments in a clinic are initiated and managed by specialized staff made up of nurses and technicians. Dialysis treatments at home can be self initiated and managed or done jointly with the assistance of a trained helper who is either a family member or a friend.

A prescription for dialysis by a nephrologist will specify various parameters for a dialysis treatment. These include number of dialysis in a week, length of each treatment, and the blood and dialysis solution flow rates, as well as the size of the dialyzer. The composition of the dialysis solution is also sometimes adjusted in terms of its sodium and potassium and bicarbonate levels.

Basically, the larger the body size of an individual, the more dialysis he will need. In the North America and UK, 3-4 hour treatments (sometimes up to 5 hours for larger patients) given 3 times a week are typical. Twice-a-week sessions are limited to patients who have a substantial residual kidney function. Four sessions per week are often prescribed for larger patients, as well as patients who have trouble with fluid overload. Finally, there is growing interest in short daily home hemodialysis, which is comprised of 1.5 - 4 hr sessions given 5-7 times per week, usually at home. There also is interest in nocturnal dialysis, which involves dialyzing a patient, usually at home, for 8-10 hours per night, 3-6 nights per week. Nocturnal in-center dialysis, 3-4 times per week is also offered at a handful of dialysis units in the United States.