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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
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