Chapter 6 Review
Chapter 6 Review BME440
Popular in Biomedical Measurements: Chapter 6
Popular in Biomedical Sciences
This 4 page Study Guide was uploaded by Joseph Ciaramella on Monday February 2, 2015. The Study Guide belongs to BME440 at University of Miami taught by Dr. Zhao in Fall. Since its upload, it has received 79 views. For similar materials see Biomedical Measurements: Chapter 6 in Biomedical Sciences at University of Miami.
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Date Created: 02/02/15
Chapter 6 BioelectricBiomagnetic and Radiation Measurement 1 Electrode theory 0 Bioelectric events very low signal intensity from uv to mv frequency varies o Electrode theory Liquid junction potentials surface junction potentials charge and potential generated at an electrodeelectrolyte interface are determined by the gradient andor distributions of cations and anions Clark Electrode measured the partial pressure of 02 02 dissolved in the blood diffuses through a permeable membrane with current potential to P02 The electrode at which the reductionoxidation redox reaction involving the molecule of interest occurs is referred to as the working electrode Cell reaction spontaneously proceeds to the right if potential of cell is greater than 0 Egt0 because 02 concentration greater than h20 2 Electrocardiogram ECG ECG is the recording on the body surface of the electrical activity generated by the heart 0 Differential recording system to measure electrical signal between two points on the body Each differential recording referred to as a lead ECG signals typically range mV require bandwith of 005 to 150hz Differential ampli er used to amplify ECG signals Pattern recognition technique approaches widely applied to ECG diagnosis 3 Electromyography EMG o EMG is the electrical signal in muscle 4 Radiation and Photon 0 Radiation Ionizing Radiation energetic electromagnetic particles or waves that have the potential to ionize an atom or molecule through atomic interactions 0 Photons a unit of electromagnetic energy EM Radiation such as xray is a kind of EM energy Photons have no electric charge and are generally regaurded as particles with zero mass 5 Ionization and Scintillation Ionization the process of formation of atoms with positive or negative charge ions Scintillation The emission of light energy by a photoluminescent material phosphor due to the incidence of ionizing radiation upon the material Photomultiplier MRI Radiation detection using scintillation Certain materials scintillators have the property to convert nuclear radiation EM energy into light with relatively high conversion ef ciency Such scintillator materials are used in conjunction with a photon detector in radiation detectors Photomultipliers are used for the detection of the photons produced in scintillator Hawaii atin L Liiht Fhatm ultip ier Tuba e gt Measuring 39 El evi e infill l iril 2 Swift r L Anode ltrate attic do t ptiigal Wintow NMR nuclear magnetic resonance Sequence of events during MR Magnetic eld Radiofrequency pulse Relaxation Patient placed in magnetic eld radio frequency pulse applied pulse is terminated allowing relaxation to occur received relaxation signal reconstructed into tomography image Magnetic eld A eld a region in space that if certain object placed within this region they will experience a force Can be considered a potential force A Magnetic Field A moving electrical charge induced MF Nuclear spin follows quantum physics rules 1 If the mass number A protons and neutrons is odd the nuclear spin is a multiple of 12 one unpaired nucleon 2 If the mass number A and the atomic number Z are both even I is 0 no unpaired nucleon 3 If the mass number A is even but the atomic number Z is odd I is an integer two or more unpaired nucleons Nuclear angular momentum the angular momentum of the nucleus is determined by the spin of unpaired particles and by the orbital angular momentum of neutron and protons 8 Magnetic Dipole Movement MDM If the element has nuclear spin each nucleus is associated with its own magnetic eld called MDM Hydrogen nuclei concerned with MRI Hydrogen nucleus is a spinning charged particle one positively charged proton MDM is property of magnet to indicate how quickly the magnet will align itself along a magnetic eld Magneton is unit of MDM Nuclei with no MDM will not be detectable by NMR Alignment of nuclear MDM in magnetic eld Nucleus with l12 has two orientations which have almost the same energy levels The vectorsum M called magnetization of the excess nuclei different between two energy levels behaves like a magnet vector 9 Precession 10 11 12 The motion of the spin axis about the direction perpendicular to the external magnetic eld is called precession Larmor Frequency The frequency of MDM precession de ned as revolutions per second Each type of nucleus will precess at a unique frequency Larmor in a given magnetic eld Radio frequency Pulse An electromagnetic wave that results from a brief application of an alternating electric current RF pulse in the direction perpendicular to zaxis and with Larmor frequency the one corresponding to hydrogen nucleus in that certain eld Secondary magnetic eld constant magnitude acting as gravity RF eld can be produced from an RF coil RF eld perpendicular to previous applied magnetic eld and spin in same frequency larmor as nucleus so the previously aligned nucleus will realign to the RF eld in Larmor freq when RF eld is on Relaxations 13 Process that occurs after terminating RF pulse in which physical changes caused by the RF pulse return to the state they were in prior to the pulse Two components of relaxation Free lnduction DecaySignal received in NMR When RF eld is off nuclei will precess back to the applied magnetic eld Magnetization M vector will sweep past the windings of RF coil a current will be induced in the coil This signal is called free induction decay FID
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