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IEM MIDTERM
X-RAY TUBE - correct answer -Electronic vacuum tube that contains two electrodes: the cathode and anode (a diode), which are necessary for the production of x-ray beam -the most important part of the x-ray, at the same time it is also the most vulnerable. cathode and anode - correct answer two electrodes Coolidge (Cathode ray) tube - correct answer - the first x-ray tube used 30 to 50 cm long and 20 cm in diameter - correct answer Modern x-ray tube measures around glass - correct answer The x-ray tube is usually made up of Ā· Tube housing Ā· Tube envelope Ā· Filter Ā·Collimator assembly - correct answer THE X-RAY TUBE HEAD ASSEMBLY Consists of: TUBE HOUSING - correct answer - is a lead-lined metal structure that houses the x- ray tube isotropically - correct answer - When x-rays are produced, individual photons are emitted ______, that is, in all directions. heavy metals ;lead. - correct answer The outside of the tube housing is made up of ____while the inside is made up of ____
protective housing - correct answer The tube housing can also be called electromagnetic lock - correct answer is an electromagnet that holds the x-ray tube assembly in place. -Steel Housing -High-voltage connector and insulator -Insulating oil -Expandable gasket/ bellow -Microswitch -Lead Lining -Tube Port -Cooling Fan - correct answer Parts of tube housing Steel Housing - correct answer -Serves as mechanical support for the x-ray tube -Made up of stainless steel High-voltage connector and insulator - correct answer Prevents electrocution Insulating oil - correct answer -Insulates the tube and dissipates the heat through convection
- will switch on the microswitch Expandable gasket/ bellow - correct answer -Attached to a microswitch -Allows for the expansion of oil due to heating -When fully expanded, it will switch on the microswitch Microswitch - correct answer -Prevents further exposure to be made when the tube reached its maximum capacity heating to prevent damage to the x-ray tube -Let the x-ray tube cool down before using again
Pyrex glass - correct answer Glass envelope is made of _____ that can withstand the tremendous heat generated inside tube Tube arcing - correct answer occurs when there is a short-circuit within the tube, typically from the cathode to the tube envelope Metal Envelopes - correct answer -maintain a constant electric potential between the electrons, the tube current and the enclosure
- tube will have longer life and are less likely to fail -Most modern high-capacity x-ray tubes are now made up of yhis -For interventional radiography, high powered x-ray X-ray Tube Window - correct answer - a thin area of the glass or metal envelope, approximately 5 cm2, through which the useful beam of x-rays is emitted
- allows maximum emission of x-ray photons with minimum absorption FILTER - correct answer - a thin sheet of aluminum that absorbs low energy x-rays, typically below 10 keV
- It is placed directly onto the path of the primary x-ray beam on the tube port in between the housing and collimator assembly Collimator - correct answer - a device that narrows the x-ray beam to desired size
- It limits the field of exposure to area of clinical interest and spare other organs or tissues from radiation exposure
- Beam limiting device Entrance Shutters Movable Lead Shutters Small Lamp and Mirror Collimator Knob - correct answer COLLIMATOR ASSEMBLY Parts
Entrance Shutters - correct answer Provide a fixed field size, usually corresponds to the biggest field of exposure (14 x 17 inches film) necessary for the shortest source- to-image receptor distance (SID). Movable Lead Shutters - correct answer Works in pairs and independently controlled, creating both square and rectangular field Trims field of exposure Used when needed a field size smaller than 14 x 17 field size at the shortest distance. Small Lamp and Mirror - correct answer Projects light that corresponds to the field of exposure. The light projected by the mirror should be the same as the area that will be struck by the x-ray beam. Collimator Knob - correct answer Allows the radiologic technologist to change the size and shape of the field of exposure. light field congruence test - correct answer A test that can be performed to determine this alignment. 36 inches - correct answer SID maximum distance 14x17 inches - correct answer largest film Engineer - correct answer _____adjusts the mirror RT - correct answer only takes image CATHODE - correct answer - The negative electrode of the x-ray tube high voltage circuit - correct answer Tube current completes the ______
Large Filament - correct answer It distributes heat to a larger focal area of the target but produces less sharp images than small focal spot 1.5 to 2 cm; .4 to 1.2 mm - correct answer The large filament is usually ____ times longer than small filament, which produces a focal spot of____ Large mA selection - correct answer the use of large filament require ____ Focusing Cup - correct answer - focuses the electrons into the target nickel, stainless steel or molybdenum - correct answer Focusing Cup is made from electrostatic repulsion - correct answer Focusing Cup serves its function through ANODE - correct answer - The positive electrode of the x-ray tube Ā· Stationary anode Ā· Rotating anode Ā· Target - correct answer Anode Configurations Stationary Anode - correct answer - the target does not move during exposure confining the heat produced during x-ray production to a very small area
- The problem with this design is that heat builds up rapidly and can damage the tube for low capacity x-ray machines such as dental x-ray units or small x-ray machines - correct answer stationary anode is only recommended to be used _____requiring very small exposure technique Tungsten Copper Rod
Copper - correct answer Parts of stationary anode Copper Rod - correct answer Acts as a mechanical support for the target and conducts heat away from the tungsten target Copper - correct answer An electrical conductor and conducts the high voltage back to the circuitry Rotating Anode - correct answer - rotates during exposure, providing a focal track instead of a focal spot focal tract - correct answer spreads the heat produced when the electrons bombard the target, thus, heating of the anode is distributed over a bigger area 3,600 revolutions per minute (rpm) to 10,000 rpm - correct answer Anode rotation can be from____ the greater the heat dissipation capacity of the tube - correct answer The faster the rotation speed ____ Molybdenum Disc Molybdenum Stem Induction Motor - correct answer Parts of rotating anode Molybdenum Disc - correct answer -Provides support for the target, poor thermal conductor 2,620oc - correct answer Molybdenum has high melting point ____, and can store 2x the amount of heat than tungsten Molybdenum Stem - correct answer -Connects the anode disc to the rotor assembly -It has low heat conductivity, which prevents the anode heat from reaching and damaging the rotor.
thicker part - correct answer The ____ of the wedge should be placed on the cathode side Heat Production - correct answer A major problem in the x-ray tube Rhenium - correct answer A small amount (5% - 10%) of _____ is added as a target material to increase tensile strength and avoid cracking at high temperature tungsten - correct answer materials with high melting point molybdenum - correct answer materials with high thermal conductivity Pyrex glass - correct answer materials with high thermal capacity Conduction - correct answer Transfer of heat from one solid object to another Convection - correct answer The transfer of heat due to movement of liquid Radiation - correct answer The transfer of heat by electromagnetic waves -Frequent use of very high or maximum exposure factors -Use of low mA factor but very long exposure time -Overloading the filament by prolonged excessive heating caused by prepping the rotor unnecessarily or pressing the rotor too long before exposure - correct answer major causes of tube failure Radiographic (Tube) Rating Charts - correct answer This chart conveys the technique factor combinations that are safe or unsafe for x-ray tube operation Anode Cooling Curves - correct answer - contain the thermal capacity of an anode and its heat dissipation characteristics
- It shows the time required for a heated anode to cool heat units (HU) or joules (J) - correct answer - The thermal capacity of an anode is measured in 1.35 to 1.4 - correct answer Using three-phase and high frequency equipment require a modification factor of_____ HU = 1.4 x kVp x mA x s HU = 1.35 x kVp x mA x s - correct answer - The formula in computing the HU for 3- phase high frequency equipment should therefore be: Housing Cooling Charts - correct answer - contain the heat capacity of the tube housing and the time that is required to cool the heated housing 1 to 2 hours - correct answer - Complete cooling after maximum heat capacity is usually achieved from_____ ready to take exposure - correct answer only press rotor when you are ______ -permanent-stationary radiographic unit -mobile radiographic unit -adiographic-fluoroscopic unit. - correct answer equipment that you will commonly see in a regular hospital, which represents the most basic radiology services a medical institution can offer., these include PERMANENT RADIOGRAPHIC UNIT - correct answer - is the most common machine that you will find in a radiology department
- This is the most basic machine and therefore all medical institutions, from clinics to big hospitals, will have at least one of this unit stationary x-ray machine or fixed x-ray equipment or simply the x-ray machine - correct answer permanent radiographic unit is also called
transverse - correct answer side to side (floating table) Vertical Cassette Holder (VCH) - correct answer - Where we put the image receptor for upright radiography such as chest x-ray Low Load Machines Medium Load Machines High Load Machine - correct answer TYPES ACCORDING TO LOAD Low Load Machines - correct answer Specially designed machines used for extremity examination and mammography where the part under examination is easily penetrated and requires low kVp technique Medium Load Machines - correct answer Those that are used for most general radiography High Load Machine - correct answer It is not commonly used in medical x-ray but is mostly used for industrial x-ray 25 to 40 kVp - correct answer Low Load Machines has kVp that ranges from _____ 40 to around 130 kVp - correct answer Medium Load Machines has kVp between_____ 125 to 150 kVp - correct answer High Load Machine Has kVp range from ____ X-RAY MOUNTING SYSTEM - correct answer - X-ray tube is mounted differently, and provides variety of ease of movement Ceiling Mounted - correct answer -This kind of mounting system is the most frequently used in modern radiographic equipment -consists of two perpendicular sets of ceiling-mounted rails that allow for both longitudinal and transverse travel of the x-ray tube
Floor-to-Ceiling mounted - correct answer -has a column which attaches the tube to two railings, one mounted on the floor and the other mounted on the ceiling, therefore providing a more stable attachment -moved longitudinally Floor Mounted - correct answer -It has a column which attaches the tube to a rail mounted on the floor -imilar to floor-to-ceiling mounted tube, it only allows movement of the x-ray tube across the long axis of the table, but offers less stability C-arm Mount - correct answer -This type of mount is very versatile, and allows for both linear and rotating motions for optimum positioning with respect to the patient -mostly used for digital radiograph -also used for radiographic-fluoroscopic units such as the ones used for interventional angiography MOBILE X-RAY UNITS - correct answer - an x-ray machine that can be moved from one place to another allowing x-ray procedure for patients who cannot be brought to the x-ray department Mobile Radiographic Unit - correct answer -the most common and is mainly used for bedside radiography -the same with the permanent radiographic unit but of lower capacity Mobile Fluoroscopic Unit - correct answer This mobile unit mostly provide fluoroscopic (real-time) imaging but is also capable of radiographic imaging Battery Powered - correct answer Uses 2 sets of lead-acid or nickel-cadmium batteries, with one set powering the motor driving the machine, and the other set providing power to the tube Capacitor Discharge - correct answer Uses capacitor that stores electrical charges and use it during operation
Photocathode - correct answer -It also acts as the negative electrode of the tube cesium and antimony compounds - correct answer Photocathode is made of photoemission - correct answer The photocathode converts light photons to electrons in a process called Electrostatic Focusing Lenses - correct answer These lenses are negative plates along the length of the image intensifier tube that repel the electron stream emitted by the photocathode Accelerating Anode - correct answer This is the positive electrode that attracts the electrons emitted by the photocathode 25 keV - correct answer Accelerating Anode maintains a constant potential of about ___ to attract the electrons, causing it to travel towards the output phosphor at a constant velocity Output Phosphor - correct answer It absorbs the electron stream and converts its energy back to light Silver-activated zinc cadmium sulfide - correct answer Output Phosphor is made up of Reversed (Upside-down) - correct answer The image emitted by the output phosophor is Brightness Gain - correct answer Refers to the ability of an image intensifier tube to convert x-ray energy into light energy and increase the brightness of the image in the process Flux Gain - correct answer Represents the tube's conversion efficiency by intensifying the light output.
59 to 75 times - correct answer Flux Gain intensifies the light photons ____ Minification Gain - correct answer Represents the increase in image brightness by making the output phosphor smaller than the input phosphor Conversion factor - correct answer An expression of the luminance at the output phosphor divided by the input exposure rate The International Commission on Radiation Units and Measurement (ICRU) - correct answer - recommends the use of conversion factor than brightness gain to quantify the increase in brightness created by an image intensifier Automatic Brightness Control (ABC) - correct answer is a function of the fluoroscopic unit that maintains the overall appearance of the fluoroscopic image by automatically adjusting the kVp or mA, or both Magnification Mode - correct answer - the voltage to the electrostatic lenses is increased, tightening the diameter of the electron stream and shifting the focal point away from the output phosphor Distortion - correct answer - Is the misrepresentation of the true size and shape of an object
- inaccurate control of focusing of electrons released at the periphery of the photocathode, resulting in unequal distortion with loss of brightness around the periphery.
- It is called "pincushion appearance" Image noise - correct answer - Is the grainy appearance of an image -It results when insufficient quantity of x-ray photons struck the input phosphor resulting in insufficient quantity of light to create an image Camera Tubes - correct answer Are diode tubes that convert the light image from the output phosphor of the image intensifier into an electrical signal that is sent to
Grid - correct answer Use of ____ will necessitate increase in exposure to compensate for the radiation that is absorbed by the grid
