Chapter 26 Biomedical technologies by TEACHING CARE online tuition and coaching classes

A modern hospital can make use of variety of sophisticated instruments and equipment of accurate diagnosis and treatment of diseases. Three main categories of instruments and equipment used are diagnostic, imaging, and therapeutic.

 Diagnostic Instruments.

(i) Sphygmomanometer

• Sphygmomanometer, commonly called P. Apparatus, is an instrument for measuring blood pressure.
• This instrument consists of a rubber cuff attached by a rubber tube to a compressible hand pump or
• Another tube attaches to the cuff and to a column of mercury or pressure dial marked off in
• Blood pressure is usually taken in the left brachial
• Blood pressure is recorded by giving the systolic pressure and diastolic pressure expressed as millimeters of mercury (mm Hg).
• A healthy young adult male has blood pressure reading of about 120/80 (e. 120 mm Hg systolic and 80

mm Hg diastolic).

• The difference between systolic and diastolic pressure is called Pulse
• Blood pressure often rises normally with age to about 130/90 at age 60.
• Abnormally high blood pressure is known medically as hypertension; abnormally low blood pressure is termed

(ii) Electrocardiograph

• The abbreviation ECG stands for electrocardiogram, a record of myoelectrical changes that immediately precede contraction of heart
• Electrocardiograph is the instrument used to record
• Leads from this instrument are attached to the chest, wrists and ankles using conducting
• The waves produced in ECG are known as P, Q, R, S and
• An ECG is helpful for diagnosing pathological disorders of the heart like coronary artery disease, coronary thrombosis, pericarditis, cardiomyopathy and
• Multi-channel monitors measure and display the ECG, blood pressure in various heart chambers and other physiological
• Echocardiography is a method of obtaining an image of the structure of heart using
• Doppler echocardiography is a technique which allows the indirect measurement of the flow of velocity as it passes through the

(iii) Electroencephalograph

• The electrical activity of the exposed animal brain was discovered by Satton in
• Hans Berger (1929) was the first to record Electro-Encephalo-Gram (EEG).
• Electroencephalography is done by attaching a number of small electrodes to the
• The electrodes are connected to an instrument that measures the brain’s impulses in microvolts and amplifies them for recording
• Electroencephalography is painless, produces no side-effects and to record it takes about 45
• An EEG records the minute electrical impulses produced by the activity of
• EEG is useful to find out whether the person is alert, awake or
• EEG can help in diagnosing certain conditions such as epilepsy, encephalitis, dementia and brain
• Electroencephalography can also be used to monitor the condition of patients during surgery and to assess the depth of
• EEG is also used as a test for brain
• The weaker magnetic fields from the brain can be studied with the help of SQUID (Super conducting Quantum Interference Device).
• Magnetoencephalography (MET) is useful for studying the disease associated with the brain and spinal

  Imaging Instruments.

Major advancements in the medical sciences have been the development of new imaging techniques that provide detailed pictures of internal organs.

(i) X-rays

• Following their discovery by Wilhelm Roentgen, a German physicist in 1895, X-ray became an important tool for medical
• X-ray are a form of electromagnetic radiation of extremely short
• When a beam of X-rays is directed at a part of the body such as chest, the rays are absorbed more by dense structures such as the ribs or heart muscles than by less dense structures such as the skin or
• This causes shadows of variable intensity to be cast on a photographic
• X-rays cause no sensation when passed through body
• Large or frequent radiation doses may damage the skin and internal organs and may cause cancer in later

life.

• The study of X-rays for detection and treatment of disease is called
• X-ray imaging in the simplest form is commonly employed for diagnosing diseases of the heart, lungs and

detection of bone and joint injuries.

• Nowadays, the risk involved in having X-rays is extremely small; radiation doses are kept to a

(ii) Computed Tomographic Scanning (CT)

• CT scanning was developed by Godfrey Hounsfield of Britain in 1968 (Nobel Prize in 1979).
• This technique combines the use of X-rays with computer technology to produce a two or three-dimensional clear cross-sectioned image of an
• Computed tomographic scanning is also known as CAT (Computed Axial Tomography).
• CT scanning provides clearer and more detailed information than X-rays.
• Another advantage of CT scanning is that it tends to minimize the amount of radiation
• CT scanning can be used to obtain images of any part of the
• CT scanning helps in the diagnosis of diseases of brain, spinal cord, chest and
• This technique is also extremely useful in detecting tumour and monitoring the extent of their spread to surrounding tissues and

(iii) Positron Emission Tomographic Scanning (PET)

• PET scanning was developed by Louis Sokoloff of USA in
• PET is a diagnostic technique based on detection of positrons (positively charged electrons) emitted by radio isotopes such as carbon ¹¹, nitrogen ¹³ or oxygen ¹⁵ generated by the
• These radio isotopes are then incorporated by chemical methods into biological molecules such as glucose, amino acids, carbon dioxide and
• These positron emitting compounds are injected into the blood-stream and are taken up in greater concentration by areas of tissues that are more metabolically
• PET scanning provides three- dimensional images that reflect the metabolic and chemical activity of tissues beings
• PET scanning is particularly valuable for measurement of regional cerebral blood volume, blood flow, metabolic rates of glucose and oxygen in
• PET scanning is used for detecting tumours, for locating the origin of epileptic activity within brain and for examining brain function in various mental
• Recently PET scanning has been used to locate colour-processing centers in human visual

(iv) Magnetic Resonance Imaging (MRI)

• MRI was originally discovered in 1946 independently by Felix Bloch and Purcell in
• MRI is a diagnostic technique that provides high-quality cross-sectioned or three-dimensional images of organs and structures without using X-rays or other
• This technique exploits the natural behaviour of the protons (nuclei) of hydrogen atoms when they are subjected to a very strong magnetic field and radio
• The most abundant source of protons in the body are hydrogen atoms in water
• An MRI scan reflects differences in the water content of
• A newer application of MRI known as Nuclear Magnetic Resonance spectroscopy (NMR) relies on the detection of other chemical elements such as phosphorus and
• The patient lies down surrounded by massive electromagnets and is exposed to short bursts of powerful magnetic field and
• The bursts stimulate protons (hydrogen nuclei) in the patient’s tissues to emit radio
• The signals are detected and analyzed by a computer to create an image of a “slice” of the patient’s
• In imaging NMR is superior to CT scanning; it generally gives much greater contrast between normal and abnormal tissues, it is free from radiation hazards and images can be obtained in any plane unlike CT, which is restricted to cross-sectional
• There are no known risks or side effects of
• MRI is a costly test that is not yet widely

• MRI is especially useful in studying brain and spinal It can clearly differentiate between white and gray matter.

(v) Ultrasound Scanning

• This is also known as echography or sonography and uses inaudible high-frequency sound waves in the range of 1-15 million
• Ultrasound waves are produced by the piezoelectric effect when an electric potential is applied to crystals of lead
• Ultrasound waves are emitted by a device called a transducer which is placed on the skin over the part of body to be
• The transducer contains the crystals of lead zirconate that converts an electric current into sound
• The transducer crystal is made to oscillate back and
• Some of the waves are reflected at tissue boundaries, so a series of echoes are
• The transducer also acts as a receiver, converting these echoes into electrical signals, which are processed and displayed on a screen of a monitor to give a two-dimensional
• Ultrasound imaging is useful in diagnosing the diseases of the brain, kidney stones, gallstones, cirrhosis, intestinal obstruction, fallopian tubes, uterus
• Ultrasound has wide applications in medicine and is especially useful in
• This technique offers no known risk to the baby and is often performed at about 16 to 18 weeks to reveal multiple pregnancy and foetal abnormalities like anencephaly and spina

 Therapeutic Instruments.

(i) Pacemakers

• Pacemaker is a device that supplies electrical impulses to the heart to maintain the heartbeat at a regular

rate.

• The artificial pacemaker was introduced by Chardack in
• Pacemakers are life saving when the normal heart rate 72-80 drops to abnormally low levels like 30-40 due

to diseases.

• Pacemaker consists of a pulse generator and an
• The pulse generator is hermetically sealed box; it contain lithium halide cells to provide power for over 10
• The electrode is a fine metallic spring ensheathed in a thin layer of biocompatible plastic; the special tip remains in contact with the interior of right
• An artificial pacemaker is implanted when a person’s sinu-atrial node is not functioning
• Two basic types of pacemakers are fixed-rate and demand
• Fixed-rate pacemaker discharges impulses at a steady rate, irrespective of the heart’s
• Demand pace maker discharges impulses only when the heart-rate slows or a beat is A normal heart-rate and beat suppresses the pacemaker.
• A pacemaker may be external (worn on belt) or internal (implanted in the chest).
• There are two main types of implantation, transvenous implantation and epicardial implantation.
• Modern pacemakers are comparatively insensitive to interference, but may be affected by powerful electromagnetic
• Anyone fitted with a pacemaker should avoid powerful radio or radar transmitters and should not pass through security screens at
• Pacemakers are likely to be influenced by microwave ovens, electric shavers, automobile ignition and cellular

 Devices.

Three types of medical devices used nowadays are implants, disposables and external prosthesis.

(i) Implants

• Implants are devices used for replacing a diseased organ or tissue within the
• Implants must be non-toxic and biocompatible and are used for replacing joint, arteries, heart valves, , and occasionally helpful in cosmetic surgery.

(a) Artificial Heart Valve

• Artificial heart valves may be either mechanical or made of human or animal
• Mechanical valves are made from special biocompatible plastics, metal alloys and
• Tissue valves are taken from cadavers of pigs or made from the pericardium of
• Mechanical valves develop tendency of clotting of blood, so the patient must have regular medication of
• Tissue valves do not require anticoagulants, but they tend to calcify, particularly in

(ii) Disposables

• Oxygenator
• The first open heart surgery was performed by Walton Lillehel (USA) in 1953 by meant of a procedure, called heart-lung
• Oxygenator is used in open-heart surgery to oxygenate the blood passing through the heart-lung machine.
• Oxygenator can be called as an artificial Two common types of oxygenators currently used are bubble oxygenator and membrane oxygenator.
• Bubble oxygenators are used for shorter operation whereas membrane oxygenators are more suitable for longer operations and for operation of

Landmarks in Medicine : Diagnosis and Surgery

• Blood Bag

• Blood transfusion is required during surgery, following delivery, for bleeding diseases and after
• Improper transfusion can cause reactions or transmit dangerous diseases such as hepatitis B and
• Disposable blood bags reduce chances of spreading
• Though not prescribed for general use, perfluorocarbons can be used as blood substitute; they dissolve and release

(c)          Blood Dialyser (Artificial Kidney)

• Kidney dialysis machine was invented by Willem Kolff, a dutch scientist in
• A person requires artificial kidney when both of his kidneys fail.
• An artificial kidney can only reproduce the passive filtration
• The blood of the patient is passed through the disposable dialyser and is then returned to the body by the intravenous
• Haemodialysis means a technique used to remove waste products from the
• The working of blood dialyser is based on the physical laws of diffusion and osmosis.