Presentation on theme: "UNIT 5A Introduction to Radiographic Equipment General Radiographic, Fluoroscopic Dedicated, Multipurpose & Mobile Conventional vs. Digital."— Presentation transcript:
UNIT 5A Introduction to Radiographic Equipment General Radiographic, Fluoroscopic Dedicated, Multipurpose & Mobile Conventional vs. Digital
General Radiographic Equipment Multi-purpose / general radiographic equipment - a wide range of procedures can be performed using this type of equipment It is used for general and/or routine radiography. Examples: orthopedic radiography, chest, podiatric, abdomen, spine and skull radiography
General Radiographic Equipment Multi-purpose general radiographic equipment –Stationary Conventional (cassette-based film) Digital (CR – cassette-based)
DR (Direct Digital) Radiographic Equipment Multipurpose –stationary IR integrated into the equipment (cassetteless)
Terminology Conventional - Uses film in cassettes (film holders) Digital - Filmless; image is viewed on monitor –CR – computed radiography – uses conventional equipment with cassettes –DR – Direct digital radiography – uses special equipment; cassetteless
Image Receptors Defined as the device that receives the energy of the x-ray beam and forms the image of the body part Four types –Cassette with film (conventional) –Image plate (IP – used in CR) –Direct radiography (detector) –Fluoroscopic screen
The X-ray Tube X-rays are produced in a cathode ray tube They are produced from a series of energy conversions
Requirements for the production of x-rays include: A source of electrons (the filament or cathode) A means to accelerate the electrons (kVp) A way to stop the electrons (the target or anode)
The x-ray tube Is an evacuated glass envelope Has a positive (anode) and negative (cathode) electrode. The cathode (filament) serves as the source of electrons High voltage is applied (kVp) to accelerate the electrons across the tube The anode (target) stops the electrons suddenly which results in the production of x-rays
X-ray production The energy conversion involves the conversion of –electrical energy to.. –heat energy to.. –kinetic energy to.. –x-ray energy and heat energy. >99% of the energy conversion results in heat <1% of the energy conversion results in x- rays
The x-ray tube Tube housing protects the patient and operator from radiation emanating in all directions. The collimator decreases or increases the size of the x- ray field (inc or dec pt. & operator exposure.) –PBL-positive beam limitation-automatic collimation – detects size of image receptor and automatically reduces/increases beam size to correspond.
Tube Stand The device that supports and permits the x-ray tube to be moved in different directions. Floor-mounted – runs along a track on the floor. Floor-to-ceiling or Floor-to-wall - has add’l tracks on wall or ceiling Ceiling-mounted – provides most flexibility
X-ray tube controls Longitudinal lock - locks tube into position along the length of the table Transverse lock- locks tube into position across the width of the table Vertical lock-locks tube vertically to set the SID* Collimator controls *SID is the distance between the source (anode) and the image receptor (IR)
X-ray tube controls Detent lock-locks the tube into the center of the bucky tray (where IR is) transversely. Tube angulation lock- allows angulation of the tube cephalad (towards the head) and caudad (towards the feet) Tube angle indicator- indicates the degrees of tube angulation
Radiographic Tables The table is designed to support the patient in a position that enhances the radiographic examination It is not designed for comfort!
Radiographic Tables The table must be uniformly radiolucent (allows x-rays to easily pass through) It must be easily cleaned. It must be hard to scratch. Some tables are stationary (ie. They don’t move)
Radiographic Tables Tables must have a space for a tray (Bucky tray) to hold image receptors (IR) and a radiographic grid IR Bucky Tray
Image Receptors Image receptors (IR) can either be film cassettes or CR (computerized radiography) imaging plates (IP).
Radiographic Table Accessories Grid –is installed over the tray & consists of Pb strips and is used to absorb scattered radiation which causes fog that degrades the visibility of image detail. –Some grids consist of a mechanism that automatically moves the grid during exposure (reciprocating grid). –Others use a stationary grid (one that does not move).
Radiographic Tables Tables can be “fixed” or “tilting” Fixed (stationary) tables do not permit tilting of patient’s head or feet Tilting tables are used mostly for radiographic/fluoroscopic applications Table height is typically 30-40” from the floor. –Some fixed tables have adjustable heights to assist patients on and off the table
Radiographic Tables Tabletops are usually movable –Some are motor-driven along their length –Some are “floating tops” which move along length and width simultaneously –Brakes can be controlled by hand, knee or foot. –Movable tables are an advantage in moving/positioning large patients!
Radiographic Table Accessories Footboards are an accessory used to support the patient in a standing position when tilting tables are employed. should be exercised to assure the footboard is attached correctly to prevent injury to the patient!
Wall-Mounted Bucky System and Cassette Holders Allows standing radiographs Cassette holder – adjustable; holds various size cassettes. Wall-Mounted Bucky – Cassette holder (tray) with grid. DR (Digital Radiography) does not use a bucky tray; image receptor does not have to be changed between exposures
Generator or Control panel KvP Selector mA Selector Exposure time Selector Table bucky vs upright Bucky switch On/Off switch Exposure switch
kVp Selector Selects the kilovoltage applied to the x-ray tube to produce x-rays Diagnostic Range 45kVp-150kVp Major/Minor (increments of 10 kV/1kV) KvP controls the penetrating power of the x- ray beam (and therefore the # of x-rays reaching the film) KvP controls the energy of the beam KvP affects density (darkness/brightness) and contrast of the image (more on this in a later lesson)
mA selector Selects the milliamperage (mA;x-ray tube current) Heats the filament; boils off electrons (thermionic emission) Controls the # of electrons flowing from cathode to anode (ie. Tube current) Controls the amount of x-rays produced Controls the amount of exposure delivered to the patient. Controls the density (darkness) or brightness of the image Range 25mA-1200mA (varies with equipment)
Exposure time selector Selects the length of the exposure Range from milliseconds to 6 seconds (varies with equipment) Controls the time electrons flow from cathode to anode Controls the amount of exposure Controls the density or brightness of the image
mAs mAs is the product of mA X exposure time It represents the quantity of radiation exposure delivered. Ex: 100 1/20 second = 5 mAs Ex: 500 second = 5 mAs
Table bucky vs upright Bucky switch Available when room has a table bucky and an upright bucky Activates the reciprocating bucky in table or upright.
Other controls On/Off switch - turns power to controls on or off Exposure switch - remote control switch which controls exposure –prep stage - heats cathode and rotates anode* –exposure stage - makes exposure(applies kV) –*Holding the “prep” or “rotor” down for an extended time decreases the life of the x- ray tube!
Other controls AEC - Automatic Exposure Control - Automatically terminates exposure when predetermined amount of exposure is reached. Determines the amount of exposure needed to produce a diagnostic image. Actually controls the exposure time. Operator selects kVp (and sometimes the mA) and appropriate cells (detectors)
AEC ( Automatic Exposure Control) Provides automatic control of x-ray exposure exposure automatically terminates when the film has received desired amount of film AEC
Radiographic/Fluoroscopic Equipment In addition to the components already discussed, fluoroscopic equipment has a movable fluoroscopic carriage which includes: –Image intensifier –An additional x-ray tube under the table
Radiographic/Fluoroscopic Equipment Spot film device – permits the radiologist to obtain static images during the fluoroscopic exam. –Uses various cassettes –Allows one or more exposures/image receptor. Digital fluoroscopy allows digital acquisition of spot films (cassetteless) –Stores static images on a computer.
Mobile Radiographic and Fluoroscopic Equipment Used for radiography: –At the patient’s bedside –In the surgical suite –In the emergency department Mobile equipment has similar controls to stationary equipment but no table.
Mobile Radiographic and Fluoroscopic Equipment A mobile fluoroscopic unit is sometimes called a “c-arm”
Introduction to the Darkroom Cassettes Radiographic Film Storage and Handling Essentials of the Darkroom Automatic Processor
Cassettes Cassettes are a light- tight film holder. They have a radiolucent (allows x- rays to pass through) front (tube side) The back side usually has Pb (lead) or Al (aluminum) to absorb back scatter. Cassettes come in a variety of standard sizes.
Standard Cassette Sizes English 14” X 17” 14” X 14” 11” X 14” 10” X 12” 9.5” X 9.5” 8” X 10” 7” X 17” Metric 35 X 43cm 35 X 35cm 28 X 35cm 24 X 30cm 24 X 24cm 20 X 25cm 18 X 43cm
Cassettes Most cassettes have intensifying screens mounted on the front and back inside surface. An Intensifying screen is a fluorescent material that converts x-ray energy to light energy which exposes the film. The purpose of intensifying screens is to reduce patient exposure. Some cassettes have a single intensifying screen; some have two intensifying screens.
Intensifying Screens An intensifying screen is composed of fluorescent phosphors which give off light when struck by x-rays. Different phosphors give off different colors (spectra) of light In radiography, most emit blue, blue/violet or green light. Radiography film is most sensitive to one of these spectrum.
Luminescence: Fluorescence vs. Phosphorescence Luminescence - emission of light Fluorescence - when a phosphor emits light upon being struck by x-rays, and light emission ceases when the x-ray source ceases. Phosphorescence - (aka “screen lag”) when a phosphor emits light upon being struck by x-rays, but the light continues to glow after the x-ray source ceases.
Radiographic Film Radiographic film is the primary medium of conventional radiography. It is composed of a polyester base which is tinted blue, And a coating of emulsion (the light & x-ray sensitive component of film) which is composed of AgBr crystals suspended in gelatin
Radiographic Film Film can either have emulsion coated on one side (single emulsion) or can be coated on both sides (duplitized). Single emulsion film is used with cassettes with single screens. Duplitized film is used with dual-screen cassettes.
Radiographic Film Classifications: Speed - reflects the sensitivity (response) of the emulsion to x-ray and light exposure. –ex: 100, 200, 400, 800 speed; the higher the number, the more sensitive the emulsion (requires less exposure) Contrast - how the film exhibits the relationships between blacks and whites. Resolution (detail) - how the film reproduces details of the subject.
Film Storage and Handling Ideal storage temperature - 68 o Ideal humidity % Stored film must be protected from: –radiation –light –age –pressure –high temperatures –too high/low humidity
Artifacts- foreign marks on the film Fog – gray/black appearance of film –Caused by: Exposure to radiation, light or age –Fog destroys visibility of details. Static-black “lightening”-like artifacts –Caused by: Static discharge in the darkroom due to low humidity & electrification by friction. Crescent (“crinkle”) marks- black moon- shaped artifact. –Caused by: Bent film (mishandling)
Darkroom Should be a safe environment for handling radiographic film. Safelight-allows visibility in the darkroom without fogging the film! –Maximum intensity of bulb- 15 watts –Safelight filters GBX - red light (for green or blue sensitive films Wratten 6B amber light for blue sensitive only (not used today) –Safelight can be direct or indirect.
Darkroom - film storage Film bins provide various sizes of film a light- tight & radiation proof storage. Films are stored largest film to smallest film (front to back) Boxes of film are stored on end to prevent pressure artifacts. The FIFO method (First in; first out) of film usage prevents film from being used after it’s expiration date. Expiration dates are stamped on each box
Darkroom – The Automatic Processor There are four racks in an automatic processor: Developer Fixer, Wash, Dryer Processing temperature is o F. Most processors process films in 90 seconds.
Automatic Processor Identify the following in the Darkroom: Main switch ( on wall) Power on/off (on processor) Film tray Water valve Replenishment tanks –One for developer; one for fixer –hoses
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