Author: John Mulindi
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Principle of Working of a Demand Cardiac Pacemaker
A cardiac pacemaker is normally used to produce pulses that force the heart to beat at higher rate; this is particularly important when blockage occurs to the biological signals that stimulate the heart to beat. A demand pacemaker is specifically helpful to the patient with partial blockage, in which case an electric pulse to the…
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What is Electroporation?
Electroporation is a technique that utilizes intense pulses of electricity to ‘punch’ holes in cell membranes. These holes or pores last for a few of milliseconds and are approximately 40 nm in diameter. This size is sufficient to permit macromolecules such as genes, drugs, metabolites, antibodies or molecular probes to permeate the membrane. The typical…
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What is Single Photon Emission Tomography (SPECT)?
Single Photon Emission Tomography (SPECT) is a technique for producing 3D images from 2D images of injected radionuclide in the body. The 2D image is obtained by using a device such as a gamma camera. This comprises of a large (0.5 diameter) crystal of NAI, which emits flashes of light when γ-rays impinge on it.…
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Scintillation Counters: Operation & Application in Medical Imaging
Scintillation counters are basically made up of the following main components: a scintillation material (crystal), a photodetector (photomultiplier in this case) which is used to count flashes (scintillations) from the crystal and an electronic pulse forming and pulse height discriminating circuit. The scintillation crystal is typically sodium iodide. Operation of Scintillation Counter The energy from…
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Features of Modern MRI Scanners
Magnetic resonance imaging (MRI) is a medical imaging modality which employs magnetic fields and radio waves/radiofrequency (RF) energy to produces images of the body. This imaging technique is based on nuclear magnetic resonance (NMR), which is a quantum mechanical phenomenon exhibited by atoms having either an odd number of protons or neutrons. Such atoms have…
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What is Magnetoencephalography (MEG)?
Magnetoencephalography (MEG) is a form of neuroimaging that maps the tangential components of magnetic fields associated with scalp potentials produced by the brain. These potentials are similar to those that can be recorded as electroencephalograms (EEGs) however the dynamic magnetic components of these potentials contain different information with spatial sampling. Unlike fMRI or PET images…
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What is Functional MRI (fMRI)?
Functional MRI (fMRI) is the use of MRI to detect localized changes in brain activity, usually in the form of changes in cerebral metabolism, blood flow, volume, or oxygenation in response to task activation. In other words, Functional MRI provides images of brain activity in response to various stimuli. These changes are interrelated and may…
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Features of an ECG Wireless Telemetry System
The advancement in technology has made it possible where necessary to monitor subjects from some distance using wireless telemetry. The biological parameter commonly studied this way is the electrocardiogram. The display of ECG and cardiac rates gives enough information on the loading of the cardiovascular system of the active subjects. In this article, we discuss…