Presentation on theme: "UNIT 5A Introduction to Radiographic Equipment"— Presentation transcript:
1 UNIT 5A Introduction to Radiographic Equipment General Radiographic, FluoroscopicDedicated, Multipurpose & MobileConventional vs. Digital
2 General Radiographic Equipment Multi-purpose / general radiographic equipment - a wide range of procedures can be performed using this type of equipmentIt is used for general and/or routine radiography.Examples: orthopedic radiography, chest, podiatric, abdomen, spine and skull radiography
3 General Radiographic Equipment Multi-purpose general radiographic equipmentStationaryConventional (cassette-based film)Digital (CR – cassette-based)
4 DR (Direct Digital) Radiographic Equipment MultipurposestationaryIR integrated into the equipment (cassetteless)
5 Terminology Conventional - Uses film in cassettes (film holders) Digital - Filmless; image is viewed on monitorCR – computed radiography – uses conventional equipment with cassettesDR – Direct digital radiography – uses special equipment; cassetteless
6 Image ReceptorsDefined as the device that receives the energy of the x-ray beam and forms the image of the body partFour typesCassette with film (conventional)Image plate (IP – used in CR)Direct radiography (detector)Fluoroscopic screen
7 The X-ray Tube X-rays are produced in a cathode ray tube They are produced from a series of energy conversions
8 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)
9 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 electronsHigh voltage is applied (kVp) to accelerate the electrons across the tubeThe anode (target) stops the electrons suddenly which results in the production of x-rays
10 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
11 The x-ray tubeTube 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.
12 Tube StandThe 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 ceilingCeiling-mounted – provides most flexibility
13 X-ray tube controlsLongitudinal lock - locks tube into position along the length of the tableTransverse lock-locks tube into position across the width of the tableVertical lock-locks tube vertically to set the SID*Collimator controls*SID is the distance between the source (anode) and the image receptor (IR)
14 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 angulationX-ray tube controls
15 The table is designed to support the patient in a position that enhances the radiographic examinationIt is not designed for comfort!Radiographic Tables
16 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
17 Radiographic TablesTables must have a space for a tray (Bucky tray) to hold image receptors (IR) and a radiographic gridIRBucky Tray
18 Image Receptors Image receptors (IR) can either be film cassettes or CR (computerized radiography) imaging plates (IP).
20 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).
21 Radiographic Tables Tables can be “fixed” or “tilting” Fixed (stationary) tables do not permit tilting of patient’s head or feetTilting tables are used mostly for radiographic/fluoroscopic applicationsTable height is typically 30-40” from the floor.Some fixed tables have adjustable heights to assist patients on and off the table
22 Radiographic Tables Tabletops are usually movable Some are motor-driven along their lengthSome are “floating tops” which move along length and width simultaneouslyBrakes can be controlled by hand, knee or foot.Movable tables are an advantage in moving/positioning large patients!
23 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!
24 Wall-Mounted Bucky System and Cassette Holders Allows standing radiographsCassette 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
25 Generator or Control panel KvP SelectormA SelectorExposure time SelectorTable bucky vs upright Bucky switchOn/Off switchExposure switchGenerator or Control panel
26 kVp SelectorSelects the kilovoltage applied to the x-ray tube to produce x-raysDiagnostic Range 45kVp-150kVpMajor/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 beamKvP affects density (darkness/brightness) and contrast of the image (more on this in a later lesson)
27 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 producedControls the amount of exposure delivered to the patient.Controls the density (darkness) or brightness of the imageRange 25mA-1200mA (varies with equipment)
28 Exposure time selector Selects the length of the exposureRange from milliseconds to 6 seconds (varies with equipment)Controls the time electrons flow from cathode to anodeControls the amount of exposureControls the density or brightness of the image
29 mAs mAs is the product of mA X exposure time It represents the quantity of radiation exposure delivered.Ex: /20 second = 5 mAsEx: second = 5 mAs
30 Table bucky vs upright Bucky switch Available when room has a table bucky and an upright buckyActivates the reciprocating bucky in table or upright.
31 Other controls On/Off switch - turns power to controls on or off Exposure switch - remote control switch which controls exposureprep 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!
32 Other controlsAEC - 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)
33 AEC (Automatic Exposure Control) Provides automatic control of x-ray exposureexposure automatically terminates when the film has received desired amount of filmAEC
35 Radiographic/Fluoroscopic Equipment In addition to the components already discussed, fluoroscopic equipment has a movable fluoroscopic carriage which includes:Image intensifierAn additional x-ray tube under the table
36 Radiographic/Fluoroscopic Equipment Spot film device – permits the radiologist to obtain static images during the fluoroscopic exam.Uses various cassettesAllows one or more exposures/image receptor.Digital fluoroscopy allows digital acquisition of spot films (cassetteless)Stores static images on a computer.
37 Mobile Radiographic and Fluoroscopic Equipment Used for radiography:At the patient’s bedsideIn the surgical suiteIn the emergency departmentMobile equipment has similar controls to stationary equipment but no table.
38 Mobile Radiographic and Fluoroscopic Equipment A mobile fluoroscopic unit is sometimes called a “c-arm”
39 Introduction to the Darkroom CassettesRadiographic FilmStorage and HandlingEssentials of the DarkroomAutomatic Processor
40 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.Cassettes
41 Standard Cassette Sizes English14” X 17”14” X 14”11” X 14”10” X 12”9.5” X 9.5”8” X 10”7” X 17”Metric35 X 43cm35 X 35cm28 X 35cm24 X 30cm24 X 24cm20 X 25cm18 X 43cm
42 CassettesMost 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.
43 Intensifying ScreensAn intensifying screen is composed of fluorescent phosphors which give off light when struck by x-rays.Different phosphors give off different colors (spectra) of lightIn radiography, most emit blue, blue/violet or green light.Radiography film is most sensitive to one of these spectrum.
44 Luminescence: Fluorescence vs. Phosphorescence Luminescence - emission of lightFluorescence - 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.
45 Radiographic FilmRadiographic 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
46 Radiographic FilmFilm 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.
47 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.
48 Film Storage and Handling Ideal storage temperature - 68oIdeal humidity %Stored film must be protected from:radiationlightagepressurehigh temperaturestoo high/low humidity
49 Artifacts-foreign marks on the film Fog – gray/black appearance of filmCaused by: Exposure to radiation, light or ageFog destroys visibility of details.Static-black “lightening”-like artifactsCaused 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)
50 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 wattsSafelight filtersGBX - red light (for green or blue sensitive filmsWratten 6B amber light for blue sensitive only (not used today)Safelight can be direct or indirect .
51 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
52 Darkroom – The Automatic Processor There are four racks in an automatic processor: Developer Fixer, Wash, DryerProcessing temperature is 90-95o F.Most processors process films in 90 seconds.Darkroom – The Automatic Processor
53 Automatic Processor Identify the following in the Darkroom: Main switch ( on wall)Power on/off (on processor)Film trayWater valveReplenishment tanksOne for developer; one for fixerhoses
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