203 MDE xray1 lectuers

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    Medical EquipmentMedical Equipment

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    Required Text Books and ReferencesRequired Text Books and References

    Hand Book of Biomedical Instrumentation,R. S Khandpur

    Introduction to biomedical equipment technology,J. J. Carr; J. M. Brown

    Medical Instrumentation, J. G. Webster

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    IntroductionIntroduction

    1. What is a medical instrument2. Medical Instruments Classes

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    What is a Medical InstrumentWhat is a Medical Instrument

    A Medical Instrument is any instrument,apparatus, appliance, material or other article,whether used alone or in combination, includingthe software necessary for its proper application

    intended by the manufacturer to be used forhuman beings for the purpose of:diagnosis, prevention, monitoring, treatment or

    alleviation of disease,

    diagnosis, monitoring, treatment, alleviation of orcompensation for an injury or handicap,

    investigation, replacement or modification of the

    anatomy or of a physiological process,control of conception, and which does not achieve itsprincipal intended action in or on the human body bypharmacological, immunological or metabolic means,

    but which may be assisted in its function by suchmeans

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    Medical Instruments ClassesMedical Instruments Classes

    Class I: General Controls: devices present minimalpotential for harm to the user and are often simplerin design than Class II or Class III devices such:

    tongue depressors, bedpans, elastic bandages,examination gloves, and hand-held surgical instrumentsand other similar types of common equipment, ..etc

    Class II: General Controls with Special Controls :are those for which general controls alone areinsufficient to assure safety and effectiveness.

    They are typically non-invasive and include:x-ray machines, PACS, powered wheelchairs, infusion

    pumps, surgical drapes, surgical needles and suture

    material, and Acupuncture needles,etc

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    Medical Instruments Classes (cont.)Medical Instruments Classes (cont.)

    Class III: General Controls and PremarketApproval : device is one for which insufficientinformation exists to assure safety and

    effectiveness solely through the general or specialcontrols sufficient for Class I or Class II devices.Such a device needs premarket approval, a

    scientific review to ensure the device's safety andeffectiveness. They are life-supporting or life-sustaining devices such:

    replacement heart valves, silicone gel-filled breastimplants, implanted cerebral stimulators, Ventilators,bed side monitors, .etc

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    1.1. XX--Ray SystemsRay Systems

    1-1. Fundamentals of X-Ray Production of X-Rays

    Properties of X-Rays

    Units of X-Radiation1-2. X-Ray Machine

    X-Ray Generator:

    High Voltage generation

    High frequency generation

    Automatic Exposure Control

    X-Ray tube High tension cable

    Collimators and Grids

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    1. X1. X--Ray Systems (Cont.)Ray Systems (Cont.)

    1-3. Visualization of X-Rays

    X-Ray Films

    Fluorescent Screens

    X-Ray Image Intensifier Television System

    1-4. Examination Table

    1-5. Kinds of X-Ray Machines

    Mobile Unit

    Dental Unit

    Mammography Unit

    1-6. Digital Radiography

    Overview

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    11--1. Fundamentals of X1. Fundamentals of X--RayRay

    Production of X-Rays:

    X-rays (or Rntgen rays) are a form of electromagneticradiation with a wavelength in the range of 0.01 to 10nanometers, corresponding to frequencies in the range

    30 to 30 000 PHz (1 PHz = 1015 Hertz)

    X-rays are produced whenever electrons collide at veryhigh speed with matter and are thus stopped

    The energy possessed by the electrons appears aftercollision in two forms:

    99 % Heat

    1 % X-rays

    f

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    11--1. Fundamentals of X1. Fundamentals of X--Ray (con.)Ray (con.)

    Properties of XProperties of X--RaysRaysShort wavelength

    Extremely high energy

    Able to penetrate through materials

    Absorbed when passing through matter

    Extent of absorption depends upon the densityof matter

    Produce secondary radiation in all matterthrough which they pass

    1 F d l f X1 F d l f X R ( )R ( )

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    11--1. Fundamentals of X1. Fundamentals of X--Ray (con.)Ray (con.)

    Units of XUnits of X--RadiationRadiation The measure of the quantity of x-radiation is Rontgen (R)

    Rontgenis the ability of radiation to produce ionization

    One (R) is the amount of x-radiation which will produce2.08x109 ion pairs per cubic centimeters of air at standardtemperature (0oC) and pressure (760 mmHg) at sea level.

    The curie (Ci) is the old standard unit for measuring theactivity of a given radioactive sample.

    The Becquerels is the more recent SIunit for radioactive

    source activity (1 curie = 3.7 x 101 curie = 3.7 x 101010 Becquerel's)Becquerel's) Rad: Measurement unit of absorbed dose ( SI: Gray)

    rem: Measurement unit of the relative biological damage as

    results from the absorbed dose (SI: sieverts (Sv) )

    1 F d l f X1 F d l f X R ( )R ( )

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    11--1. Fundamentals of X1. Fundamentals of X--Ray (con.)Ray (con.)

    Units of XUnits of X--Radiation (cont.)Radiation (cont.)

    11 2 X2 X R M hiR M hi

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    11--2. X2. X--Ray MachineRay Machine

    Generate high-energy, high frequency electromagnetic

    waves (X-Rays) for use in diagnostic and treating disease Block diagram of an x-ray machine

    XX R G tiR G ti

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    XX--Ray GenerationRay Generation

    X-Ray GeneratorHigh voltage generator:

    modifies incoming voltage and

    current to provide an x-raytube with the power needed toproduce an x-ray beam of the

    desired peak kilovoltage (kVp)and current (mA) and duration(Time).

    Major components are:Control panel

    Transformer assemblyX-ray generator components

    XX R G tiRay Generation

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    XX--Ray GenerationRay Generation

    Control panel

    Permits the selection oftechnique factors andinitiation of radiographicexposures

    mA, kV, Time

    Transformer assembly:

    Transformer

    Rectifiers

    Three major circuits:

    High voltage circuit

    The filament circuit

    Timer circuit

    XX Ray GenerationRay Generation

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    XX--Ray GenerationRay Generation

    Transformer: Transformers modify the voltage ofincoming alternating-current (AC) electricalsignals to increase or decrease the voltage in acircuit.

    Step-up transformer supplies the high voltage to the

    x-ray tube (voltage increases and current decreases)Step-down transformer supplies power to heat the

    filament of the x-ray tube (voltage decreases andcurrent increases)

    Autotransformer: Supplies the voltage for the twocircuits and provide a location for the kVp meter(indicates the voltage applied across the x-ray tube)

    XX Ray GenerationRay Generation

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    XX--Ray GenerationRay Generation

    Rectifiers: convert AC into the direct current

    (DC) required by the x-ray tube.

    A rectifier restricts current flow in an x-ray tube

    to one direction (from cathode to anode),thereby preventing damage to the x-ray tubefilament.

    Two types:Half wave

    Full wave

    Voltage waveforms rectification

    XX Ray GenerationRay Generation

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    XX--Ray GenerationRay Generation

    Depending on the rectifiers and components

    included in the high-voltage circuit, the voltagewaveform presented to the x-ray tube can be:

    Ideal DC

    Single phase half wave

    Full-wave rectified

    Voltage x-ray tube waveforms(left) and radiation intensity

    waveform (right)

    XX Ray GenerationRay Generation

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    XX--Ray GenerationRay Generation

    3-phase, 6 pulses

    3-phase, 12 pulses

    High frequency

    Constant potential

    Voltage x-ray tube waveforms

    (left) and radiation intensitywaveform (right)

    XX-Ray GenerationRay Generation

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    XX--Ray GenerationRay Generation

    Single phase full waveform

    rectified circuit

    Three phase full wave rectifier