Biomedical Instrumentation

Archive for the ‘Biomedical Engineering’ Category

Lungs is responsible of the respiratory system. The process of breathing inside is called as inspiration. The process of breathing outside is called as expiration. Generally the intake food is cut into smaller pieces and mixed with saliva in the mouth. Gullet carries the food from mouth to the stomach. The stomach wall contains various types of glandular cells that secrete hydrochloric acid, pepsin and muscus. Normally, it will take 5 hours for digestion. The intestine will digest the food further. Major constituents of food are carbohydrate, fat, proteins, minerals, vitamins and lipids. Get vent server details on the above link. Excretion is the process of elimination of water product from the body. The various excretory organs present in the human body are kidney, skin, lungs and large intestine. Kidneys – removes nitrogenous wastes and non – volatile substances. Skin – (sweat) removes salt + water. Lungs – removes CO2 which is volatile substances and large intestine – removes undigested food through anus. Regulatory system can be classified in to nervous system for rapid events regulation and endocrine system for regulation of slower metabolic process. Central nervous system (CNS) and peripheral nervous system (PNS) are the divisions of nervous systems. The sub divisions of PNS are afferent nervous system and autonomic nervous system. Autonomic nervous system consists of sympathetic system and Para sympathetic system.

The movements of various parts of body are caused by the muscles. Generally three types of muscles are present namely, voluntary muscles, involuntary muscles and cardiac muscles. Voluntary muscles will work at our will or wish. The muscle will work without the order of human. The muscles present in the food canal. The muscle will help in functioning of the heart and are working day and night without tired. In the muscular system, muscular contraction is the basic principle for generating the heat. There are two types of muscular contraction namely isotonic contraction and isometric contraction. The muscle is shortened under the constant load i.e. 20% of energy is converted to work and the remaining is converted to heat in isotonic contraction. The muscle contract without any physical shortening i.e. no work is obtained and almost all energy is converted into heat and energy.

Dear friends! I bring to your kind attention that a psychological response to a current applied to the surface of the heart that results in unwanted stimulation like muscle contractions or tissue injury is called micro shock. Micro shock occurs when currents in excess of limited flow through an insulated catheter to the heart. Many devices have a metal basis and cabinet that can be touched by the medical attendants and patients. If they are not grounded, then an insulation failure or short circuit results and lead to macro shock or micro shock. Hence the patients must be isolated or insulated from the electrical circuit.

Mathematical operation and pattern recognition: Many important physiological variables cannot be measured directly, but must be calculated from other variables that are accessible. If a digital computer is connected on-line with the measuring instruments, the calculated results can often be obtained while the patient is still connected to the instruments. To reduce certain types of physiological data into useful parameters, it is often necessary that important features of a physiological waveform or an image be identified. Digital computer programs are available to search the data representing the ECG signal for certain predetermined characteristics that identify each of the important peaks.

Limit detection and control function: In application involving monitoring and screening, it is often necessary to determine when a measured variable exceeds certain limits. By comparison of measured parameter with each limit of the range, the computer can indicate which parameters exceed the limit and the amount by which they deviate from normal. Digital computers are capable of providing output signals that can be used to control other devices. The computer can also be used to provide feedback to the source of its data.

Telemedicine is the application of telecommunications and computer technology to deliver health care from one location to another. In other words, telemedicine involves the use of modern information technology to deliver timely health services to those in need by the electronic transmission of the necessary expertise and information among geographically dispersed parties including physicians and patients, to result in improved patient care and management, resource distribution efficiency and potentially cost effectiveness. Advanced information technology and improved information infrastructure the world over have made telemedicine an increasingly viable health care service delivery alternative, measured in clinical, technical and economic terms. However, most existing telemedicine programs, at present, are operating in investigational settings. Issues such as telemedicine technology management and other barriers such as professional, legal and financial are still under debate.

From a technology stand point, the telemedicine technology includes hardware, software, medical equipment and communication link. The technology infrastructure is a telecommunication network with input and output devices at each connected location. Although telemedicine can potentially affect all medical specialties, the greatest current applications are found in radiology, pathology, cardiology and medical education.

Teleradiology and Telepathology: Radiological images such as X-ray, CT or MRI images can be transferred from one location to another location for expert interpretation and consultation. The process involves image acquisition and digitalization. To obtain an expert opinion on the microscopic images of pathology slides and biopsy reports from specialists. Telecardiology relates to the transmission of ECG, echocardiography, color Doppler, etc. In addition, telemedicine is being advantageously used for:

Tele-education and Tele-consultation: Delivery of medical education programmes to the physicians and paramedics located at smaller towns that are professionally isolated from major medical centers.Specialist doctors can be consulted either by a patient directly or by the local medical staff through telemedicine technology. In the latter case, the patient is substituted by his or her electronic patient record which has complete information on the physical and clinical aspects of the patient. Depending on the level of interaction required, the telecommunication infrastructure requirements also varies: from normal telephone, low-bit rate image transmission, real time video transfer to video conferencing.

The medical thermograph is a sensitive infrared camera which presents a video image of the temperature differences to be seen instantaneously, providing fairly good evidence of any abnormality. However, thermography still cannot be considered as a diagnostic technique comparable to radiography. Radiography provides essential information on anatomical structures and abnormalities while thermography indicates metabolic process and circulation changes, so the two techniques are complementary. The human body absorbs infrared radiation almost without reflection, and at the same time, emits part of its own thermal energy in the form of infrared radiation.

The intensity of this radiant energy corresponds to the temperature of the radiant surface. It is, therefore, possible to measure the varying intensity of radiation at a certain distance from the body and thus determine the surface temperature. In a normal healthy subject, the body temperature may vary considerably from time, but the skin temperature pattern generally demonstrates characteristic features, and a remarkably consistent bilateral symmetry. Thermography is the science of visualizing these patterns and determining any deviations from the normal brought about by pathological changes.

Thermography often facilitates detection of pathological changes before any other method of investigation and in some circumstances, is the only diagnostic aid available. Thermography has a number of distinct advantages over other imaging systems. It is completely non-invasive, there is no contact between the patient and system as with ultrasonography, and there are no radiation hazards as with X-rays. In addition, thermography is a real time system.

The examination of the female breast as a reliable aid for diagnosing breast cancer is probably the best known application of thermography. The mammary glands were the first organs that thermography was clinically applied to. It is assumed that since cancer tissue metabolizes more actively than other tissues and thus has a higher temperature, the heat produced is conveyed to the skin surface resulting in a higher temperature in the skin directly over the malignancy than in other regions.

Feedback is a common engineering term and refers to its function to control a process. When this concept is applied to biological processes within the body, it is known as biofeedback. Here again, biofeedback is a means for gaining control of the body processes to create a specially required psychological state so as to increase relaxation, relieve pain and develop healthier and more comfortable life patterns. The technique involves the measurement of a variable produced by the body process and compares it with a reference value. Based on the difference between the measured and reference value, action is taken to bring the variable to the reference value.

It may be noted that biofeedback is not a treatment. Rather, biofeedback is an educational process for learning specialized mind/body skills. Through practice, one learns to recognize physiological responses and to control them rather than having them controls us. The objective of biofeedback training is to gain self-regulatory skills which help to adjust the activity in various systems to optimal levels. Many different physiological processes have been evaluated for possible control by biofeedback methods. However, the following four neural functions are commonly employed:

• Emotions or electro dermal activity

• Muscle tension or electromyography measurements

• Temperature or sympathetic pattern

• Pulse

Electro dermal activity is measured in two ways: Basal Skin Response and Galvanic Skin Response is a measure of the average activity of the sweat glands and is a measure of the phasic activity of these glands.
BSR gives the baseline value of the skin resistance where as GSR is due to the activity of the sweat glands. The GSR is measured most conveniently at the palms of the hand, where the body has the highest concentration of sweat glands. The measurement is made using a dc source. Biofeedback instrumentation for the measurement of EMG, temperature and pulse or heart rate is not different from other instruments used for the measurement of physiological variables. Transducers and amplifiers are employed to measure the variable that is to be controlled by the feedback process. The magnitude of the measured variable or changes in the magnitude is converted into a suitable visual or auditory stimulus that is presented to the subject.

To operate effectively with or as a part of the medical instrumentation system, a computer or microprocessor must properly interface with the various devices comprising the rest of the system. Input data must be requested and are received in an acceptable form and output signals must be provided wherever control functions are required or where data must be transmitted to other equipment. Many biomedical instruments with which a computer may be interfaced generate analog data in the form of voltages proportional to the variables represented. For computer entry, these analog signals must be converted into digital form.

Interfacing a computer with other devices that handle data in digital form involves both hardware and software. The software is usually a part of the computer’s system software and is often an extension of the input-output package that controls the flow of information to and from such peripheral devices as disks and magnetic tape drives. Programs are included to monitor input lines, generate commands, identify the various sources of input data, accept each word of data as it arrives, and route it to the arithmetic unit or memory as appropriate.Interfacing hardware is required to format the data, provide buffer registers to temporarily hold each word until it can be dealt with, and where necessary, convert input or output signals from one system of logic to another.

Formatting is the arranging of data into a form that can be accepted and recognized by the computer or device receiving computer output. It involves such factors as the number of bits to be received or sent out at a time and the way in which the bits of a word are arranged among the input or output lines. Data may be received or sent out in either serial form or parallel form. When the digital medical devices with which the computer must be interface can be controlled so that transfer of data always occurs in time corresponding with computer’s internal clock, the I/O operation is said to be synchronous. I am sure this article will enhance your knowledge regarding interfacing techniques of computer with modern medical equipment.

Dear readers! The first biomedical instruments incorporating microprocessors began to appear on the market around 1975. While the first devices were mainly laboratory type instruments, microprocessors are the advance technology which is now used in all areas of biomedical instrumentation. Although microprocessors were originally advocated mainly as replacement for controllers using digital logic, it was soon found that the new technology could be extended much further. Following are some examples of the ways in which microprocessors are employed in contemporary medical instruments.

Calibration: Many instruments require zeroing and recalibration at certain time intervals, sometimes every few hours. A software or hardware timer in a microprocessor system can initiate a calibration cycle. As with manual calibration, this cycle requires the introduction of a blank and standard, each of which might be in the form of a voltage, gas or liquid. In manual calibration methods, zero and gain control potentiometers are normally adjusted until the readout indicates the proper values. Microprocessor equipped devices usually perform the calibration in digital form. During the calibration, offset and gain correction factors are determined and stored in memory to be applied to the measured data during the measurement.

Table lookup and averaging: In analog system, nonlinear functions are usually implemented by straight-line approximations. In microprocessor-equipped systems, table lookup with interpolation can be used. This procedure is less limited and more accurate and also permits the determination of parameters that are independent on more than one variable. Also microprocessors can easily average data overtime or over successive measurements and can thus decrease statistical variations.

Formatting and printout: Because medical equipment using microprocessors usually processes data in digital form, the microprocessors can be utilized to format the data, convert the raw data into physical units, and printout the results in a form that does not require further transcribing or processing. My dear friends! I am sure this article will enhance your knowledge regarding the usage of microprocessors in biomedical instrumentation.