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Dental X-ray Machine

118 Radiology

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• The Dental x-ray machine consists of 3 visible component parts:– The Control Panel

– The Extension Arm

– The Tubehead

Component Parts

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Control Panels

Older style Newer Design

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• The Control Panel contains:– On-off switch and an indicator light– The exposure button and an indicator light– Control devices to regulate the x-ray beam

• Time setting• kVp setting• mA setting

The Control Panel

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Miliamperage and Kilovoltage • Miliamperage = MA• controls number of electrons produced at tungsten filament quantity• 7-15 are average dental x-ray unit mA numbers

• Kilovoltage = kV• controls penetrating power of electrons and x-ray quality• how fast they travel from cathode to anode• creates contrast on resulting film image• usually 70 or 90 kVp kilovoltage power

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Extension Arm

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Extension Arm

• Hollow, holds electrical wires connecting tubehead with control panel

• Used to position tubehead

• Tubehead attached to arm by yoke, which can be moved 360 degrees horizontally

• Folds up when not in use

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Tubehead

• Houses the x-ray tube

• Made of metal; lined with lead to prevent radiation leakage

• Filled with oil to absorb heat which is generated during x-ray production

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X-ray Tube

• Made of glass• 6” long x 1 ½” diameter• Air is removed to create

vacuum to allow electrons to flow freely between cathode and anode

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Cathode

• Tungsten filament gets hot when electricity is sent to tube

• Creates electron cloud

• Focusing cup: Keeps electrons suspended at cathode

• When exposure button is pushed, electrons shoot across tube to anode

Negative end of tube

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Anode

Postive end of tube• Tunsten target• Electrons strike target and

product x-rays• 99% get absorbed by oil• 1% exits the tube at the area

towards the patient• Center of this beam of x-

rays is called the Central Ray

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PID

• Position indicating device• Lead lined• Aims x-ray beam at film in

pt mouth OR at extra oral cassette

• Open end placed against pt face

• 8,12,16 inches long

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Filter• Aluminum disc at port

where the PID is connected to the Tubehead

• Removes (absorbs) low-energy, long wavelength x-rays

• Only allows high energy, short wave length x-rays to pas through

• Both kinds of x-rays are absorbed by the pt’s tissues; only the short wave length , high energy x-rays create image on film

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Collimator

• Metal disc (lead) with small opening in center to control size and shape of x-ray beam

• Further reduces pt exposure• 2 ¾” diameter; round shape

and size• Also available in

rectangular shape which exactly fits #2 film size exposes over ½ less tissue with rectangular collimator