Author: John Mulindi
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Commonly used EEG Electrodes
The most commonly employed electrodes for recording electroencephalographic signals from the brain (EEG) are cup electrodes and subdermal needle electrodes. Cup electrodes are fabricated from platinum or tin approximately 5-10 mm in diameter. These cup electrodes are filled with a conducting electrolyte gel and can be attached to the scalp with adhesive tape. Recording of…
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What is Intraoperative Radiotherapy?
Intraoperative radiotherapy (IORT) is a method that combines radiation therapy with surgery to irradiate tumours in situ, without delivering a significant dose to surrounding normal, critical structures and is typically performed using electron beams from linear accelerators. This contrasts with external beam therapy using X-ray beams where the dose that can safely be delivered to…
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The Principles of Microbial Biosensors
Introduction The underlying basis of a microbial biosensor is the close proximity between an immobilized microorganism that serves as a specific recognition element and an electrochemical or optical sensing transducer that is used to convert the biochemical signal into an electronic signal that can be processed. The manufacture of a microbial biosensor requires the immobilization…
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Optical Tomographic Imaging
The optical properties of normal and diseased tissues are usually different despite the large variation of values in optical properties of the normal tissues alone. A case in point is the cancerous tissues that manifest significant architectural changes at the cellular and subcellular levels, and the cellular components that cause elastic scattering have dimensions typically…
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The Instrumentation for Recording ECG Signals
Since the electrical events in the normal heart precede its mechanical function, ECG signals play an important role in diagnosis and monitoring of a wide variety of cardiac abnormalities including myocardial infarction and chamber enlargements. Hence, ECG signal acquisition systems are extensively employed in cardiology, cardiac catheterization laboratories, intensive and cardiac care units, etc. The…
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What is Echocardiography?
Echocardiography is a diagnostic technique that employs ultrasound to produce an image of the beating heart in real time. A piezoelectric transducer element is used to emit short bursts of high frequency, low intensity sound through the chest wall to the heart and then detect the reflections of this sound as it returns from the…
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The Measurement of Tissue Optical Properties
The measurement of optical properties i.e. absorption coefficient (μa), scattering coefficient (μs), and scattering anisotropy (g) of biological tissues is a key challenge in the field of biomedical optics. Information about these parameters is essential in both therapeutic and diagnostic applications of light in medicine. Case in point, optical properties are needed to predict fluence…
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The Operation of Fiber-optic Based Blood Gas Sensors
To perform in vivo measurements and to steadfastly analyze blood gases, a small, stable, accurate and bio-compatible sensor is needed that can be inserted in the blood flow of an artery through an arterial cannula and remain in place for several days. Additional, it has to be low cost so that it could be used…
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The Principle of Surface Plasmon Resonance Sensors for Detection of Antibody & Antigen Interactions
When monochromatic polarized light for instance, from a laser source impinges on a transparent medium having a conducting metallized surface (e.g. Ag or Au), there is a charge density oscillation at the interface. When a light at an appropriate wavelength interacts with the dielectric-metal interface at a defined angle, called the resonance angle, there is…
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Key Properties of Bioelectrodes
To record biopotentials, an interface is required between the electron-conducting copper wires connected to signal conditioning amplifiers and the ion-conducting environment of living organisms. Electrodes form this interface. Some of the several kinds of electrodes are better than others in terms of low noise and ease of use. Initial ECG electrodes were non-disposable, nickel-silver plated…