The X-Ray imagination system has one map. and that is to supply a changeless flow of negatrons that are strong plenty to bring forth and x-ray beam to make an image. There are many different sizes and types of imaging systems but no affair what system you use every type will hold three chief subdivisions. Those subdivisions are the control console the high electromotive force generator and the x-ray tubing. The x-ray tubing is located in the test room the control console is located in an adjoining room that is separated from the test room by a lead wall to protect the radiographer from radiation exposure.
The wall will hold a window so that the patient can be viewed without holding to come in the radiation country. The high electromotive force subdivision will most probably be housed in an equipment cabinet along the wall near to the x-ray tubing nevertheless sometimes the exam room will hold false ceilings and the generators will be installed there to be hidden. There are two divisions to the chief x beam circuit those are the primary side and the secondary side and I will speak about both of those throughout this paper.
The Control Console is the subdivision of the imagination system that most Engineers are familiar with. It is the Primary side of the chief circuit and it includes the incoming current the exposure switch. the autotransformer and the primary twist for the measure up transformer. Through the Control Console the tech is able to command the x-ray tubing current and the electromotive for...
ce so that the utile x-ray beam that reaches the patient has the right measure or the strength of the beam and is expressed in mR/mAs and the right quality of x-ray beam which refers to the perviousness and is expressed in kVp.
There are four different things that need to be controlled by the control console the Line Compensation kVp. ma and exposure clip. Besides controlled by the control console are metres to supervise kVp. ma and exposure clip Some consoles will besides supply a metre for ma. All electric circuits that connect metres and controls on the operating console are at low electromotive force to minimise the possibility of risky daze. ( Bushongs ) Most operating consoles are now based on computing machine engineering and most things now are selected automatically.
The controls and metres are digital and the techniques can be selected with a touch screen every bit good as the numeral choice is besides sometimes replaced by icons bespeaking organic structure portion. size and form but the Techs must still cognize how to decently utilize the console. and cognize how to set the techniques manually ( Line Compensator ) Most imaging systems are designed to run on 220V although there are some that can run on 110V or 440V. However the power coming from the wall is non ever consistent because the power companies can non continuously provide 220v accurately.
Because of this and the fact that the infirmary is utilizing up a batch of the power being supplied the electromotive force that is being provided to the x-ray unit
can easy change every bit much as 5 %. That fluctuation in the electromotive force can ensue in a big fluctuation in the x-ray beam which makes accomplishing a high quality image inconsistent.
A line compensator measures the electromotive force provided and is designed to set the electromotive force coming in to a steady 220V so that high quality images are invariably produced. The older units required the techs to set the electromotive force while they looked at a line electromotive force metre but today in modern imaging systems the line compensator is wired to the autotransformer therefore there is automatic line compensation so a metre is non necessary.
( kVp Selection ) The power that is supplied to the x-ray machine has to travel through the autotransformer foremost. The autotransformer is a measure up transformer designed to provide electromotive force of different magnitudes to several different circuits of the x-ray machine including the fibril circuit every bit good as the high electromotive force circuits. An autotransformer merely has one twist and one Fe nucleus.
That one individual weaving Acts of the Apostless as both the primary and the secondary twist. It has a certain figure of connexions or electric lights-outs along its length on both sides where the connexions are made. Because the autotransformer has merely one twist and one nucleus it works on Self Induction which is where a magnetic field of a spiral induces a counter Electromotive Force. This ego induced electromotive force will oppose the applied current. The map of the autotransformer is to choose the kVp.
Most consoles will hold one or two bosss that will alter the lights-outs of the autotransformer which will set your major and minor kVp and modern units will hold an LED read-out of the kVp. A kVp metre is placed across the end product terminuss on the transformer and it is considered a pre-reading because it reads the existent electromotive force from the autotransformer non kVp. kVp is considered the quality of the x-ray beam or in other words the sum of incursion in the beam.
( mA Selection ) The tubing current or the figure of negatrons traversing from the cathode to the anode per second is measured in mAs (ma). A separate circuit called the Filament current. is measured in Amperes ( A ). Connections on the autotransformer provide electromotive force for the fibril circuit. The electromotive force is so delivered to the filament transformer which is a measure down transformer significance that the electromotive force supplied to the fibril is lower than the electromotive force applied to the filament transformer.
A little alteration in filament current produces a big alteration in the tubing current. ( 111 Handout ) The figure of negatrons emitted by the fibril is determined by the filament temperature and the filament temperature is controlled by the filament current which is measured in Amperes ( A ). More negatrons are released when the filament current additions doing the fibril to go hotter.
This is called Thermionic Emission. The tubing current is monitored with an ma metre and it is connected at the centre of the secondary twist of the measure
up transformer. Because of this. the metre is non in contact with high electromotive force which allows for the metre to be put on the console safely. When the tech is choosing the ma they are really make up one's minding how many x beams are to make the patient.
Preciseness resistances are used to cut down the electromotive force to a value that corresponds to the selected ma. ( Bushongs ) There are two types of resistances that I’m traveling to speak about in this paper they are Saturable reactors and Rheostats. A Saturable Reactor is what is used in modern equipment today. It is a signifier of inductance where the magnetic nucleus can be saturated by a direct electric current in the control twist. Because of the manner that the power twists the control twist and the nucleus are arranged the control twist is isolated from the AC power.
The power twists cancel out the AC electromotive forces that would be induced into the control weaving. They frequently have multiple lights-outs to let a little induction to be used with a big burden or a larger induction to be used with a smaller burden. This allows the current to stay changeless. no affair what the burden may be. A Rheostat is what controls the filament current or the ma which is measure or figure of x beams produced. It is a variable resistance that is used to change the sum of current flowing in a fibril circuit. It is made by weaving a really thinly insulated opposition wire around a barrel.
A metal skidder wears off a line of the insularity so it can do electrical contact with the metal underneath. The skidder is mounted on a thick metal saloon which makes up portion of the circuit. As the skidder moves along the metal saloon. it includes more of the opposition wire in the circuit. The longer the wire. the higher the opposition. As opposition is increased the current in the fibril circuit decreases. Rheostats operate on AC or DC and works on Ohm’s Law which states that the current through a music director between two points is straight relative to the possible difference across the two points.
( Timers ) The timer circuit consists basically of a timing device that can be varied. This device allows high tenseness electromotive force to be applied to the x beam tubing. There is a timing mechanism that automatically cuts off the current after a pre-set clip. X raies are merely produced when a current base on ballss through the timer circuit. The timer circuit is separate from the other chief circuits. It consists of electronic devices whose intent is to do or interrupt the high electromotive force across the tubing on the primary side of the high electromotive force subdivision.
Throughout the history of X raies there have been many types of timers but today all timers are electronic timers of different types. The timers I’m traveling to speak about are Mechanical Synchronous Impulse.
Electronic and Photo timers ( AEC ). The mechanical timers are an cheap and really simple timer that have a clock like
mechanism. The operator turns the dial to the desired exposure clip and as it unwinds the exposure is made. The minimal exposure clip for a individual stage machine is 8ms and the lower limit for a three stage machine is 1ms because they are really undependable.
Therefore these timers are merely used in portable ten beam machines or dental ten beam machines because they don’t require short. accurate exposures. The Synchronous timers are driven by a synchronal motor which run at approximately 60rps. The minimal exposure clip is 1/60 sec. It is non accurate below 1/20 sec. This timer can merely be used for a individual exposure because they have to be reset after each exposure.
The Impulse timer besides operates on a synchronal motor but at a much higher velocity. It provides shorter exposures every bit low as 1/120 of a 2nd to every bit high as 1/5 of a 2nd. This timer is much more accurate than the synchronal timer because it starts and stops the current at the zero point of the AC rhythm. The mAs timer is the lone timer that is located on the secondary side of the high electromotive force subdivision because it monitors the existent tubing current. It monitors the merchandise of the ma and clip and Michigans exposing when the desired ma has been reached.
It is designed to supply the shortest exposure and the highest safe tubing current. Electronic timers are used in modern equipment today. They are the most sophisticated the most complicated and the most accurate timer It consists of complex circuit based on the clip required to bear down a capacitance through a variable resistance. This timer allows for a broad scope of clip intervals that can be selected every bit little as 1ms.
The ground they are used so much today is because they can take rapid consecutive exposures. Phototimers besides known as Automatic Exposure Control ( AEC ). step the sum of radiation that reach the image receptor and stops exposing automatically when sufficient radiation needed to bring forth the right sum of denseness on the IR. With AEC the Tech can choose where to read the radiation the coveted denseness the kVp and the backup ma.
One advantage to the AEC is the backup timer it is a safety factor that will halt exposure if for some ground it doesn’t halt when it is supposed to. An AEC x-ray machine system must be calibrated when it is installed.
To make this. a apparition is used so that the AEC can be adjusted for the scope of strengths required for quality images. The standardization is normally done by the service applied scientist. Specific anatomy must be positioned above the appropriate chamber hence patient placement is the most of import facet when utilizing AEC. There are two types of exposure timers a photomultiplier and an Ion chamber. Phototimers consist of a fluorescent screen that convert x beams to visible radiation which is directed to the photomultiplier.
The photomultiplier converts light into negatrons and negatrons are so multiplied in the tubing. It is located behind the movie and the fluorescent screen and the phototube is
activated by visible radiation. Ionization Chamberss are the type of AEC that are used the most. The ionisation chamber contains a volume of air between two metal electrodes and it is level and radiolucent so that it will non interfere with the image.
It is located between the patient and the Image Receptor and measures the strengths of the radiation. Radiation is measured at either the centre of the movie or off to the sides. The centre cell is used for most images and the outside cells are used for thorax. venters and ribs.
( Spin Top Test ) Spin top trials are used to look into x-ray timers in individual stage machines merely. It is a level heavy metal disc with a hole in the margin. The disc is about 5cm-25cm in diameter. A individual stage x-ray machine emits X raies in pulsations. A half wave electromotive force produces 60 pulses/second and full moving ridge electromotive force produces 120 pulses/second. X raies are produced by each of these pulsings. The developed movie will demo a point for each pulsing that occurred during the exposure.
Three phase x-ray machines do non utilize pulsed radiation because the end product is changeless. To look into the timers on these machines a physicist will utilize a powered synchronal spin top that rotates at 1rps. This trial is measured in grades. A half 2nd peers a 180 degree image a one-fourth of a 2nd peers a 90 degree image and a 1 2nd peers a 360 degree image.
Flow of current through the console
The flow of current through the control console of an x-ray machine starts with the power coming in from the wall mercantile establishment which receives its electricity from a beginning outside the edifice. The current goes to primary side of the control console and so to the line compensator which maintains the electromotive force at a steady 220v. It is so supplied to the primary side of the autotransformer.
The autotransformer steps up the electromotive force by electrostatic ego initiation which makes the input twice the electromotive force value. The lights-outs on the secondary side of the autotransformer are what are used to choose the major and minor kVp they are pre-read by the kV metre on the secondary side. After the electricity leaves the autotransformer it is divided into two separate currents the tubing current and the filament current.
The electromotive force that is carried through the tubing current so goes to the measure up transformer on the primary side of the high electromotive force subdivision. The electromotive force that is carried through the filament current is carried to the ma picker which is a variable resistor that has a series of resistance spirals although today a saturable reactor is preferred. It has an Fe nucleus that is saturated with magnetic flux.
The current is so passed to the measure down transformer which is besides in the primary side of the high electromotive force subdivision. When the exposure switch is pressed. the current is passed to the high electromotive force subdivision. The exposure timer is what regulates how much of an exposure is made. Its intent is
to do or interrupt the high electromotive force across the ten beam tubing.
High Voltage Generators
When power is supplied to a edifice. it is normally supplied at 110v or 220v but that is non adequate power to run an x-ray machine. These machines need much higher electromotive forces of approximately 30. 000v to 150. 000v or 30kv-150kv in order to throw the negatrons across the tubing at the proper velocity. That is why a high electromotive force generator is a major constituent of the ten beam machine its chief intent is to change over the low supply electromotive force into the coveted kilovoltage.
The high electromotive force generator is non normally seen by the radiographer or the patient. They are kept in an electrical cabinet along the wall or if false ceilings are available they are sometimes put there so they are out of sight. The high electromotive force subdivision of the ten beam machine has three chief parts. Those are the high electromotive force measure up transformer the filament transformer ( step down transformer ) and rectifiers. All three of these constituents are immersed in oil for electrical insularity.
( Step up transformer ) The high electromotive force transformer is a measure up transformer which means that the secondary side. which is measured in kilovoltage is higher than the primary side which is measured in electromotive force because there are more twists on the secondary spiral than on the primary spiral so the map of the measure up transformer is to change over the entrance Vs on the primary side to kilovolts on the secondary side. The ratio of twists on the primary side and on the secondary side is called bends ratio.
The bends ratio for most ten beam high electromotive force transformers is between 500 and 1000 Transformers merely operate on jumping current ( AC ) and the wavelengths on both sides primary and secondary is sinusoidal and the lone difference between the two is their amplitude which is from the extremum to the vale. There are three parts to the high electromotive force measure up transformer: the primary spiral the secondary spiral and the Fe nucleus.
In transformers the primary spiral and the secondary spiral are wrapped around an Fe nucleus and unlike the autotransformer that operates on ego initiation step up/step down transformers operate on common initiation. Common initiation is the changing alternating current flow in the electromagnet crates a variable magnetic field so when it passes through the primary spiral an induced current will flux through the secondary spiral.
Alternating spiral flows through the primary spiral and sets up a magnetic field around the spiral. the altering magnetic flux cuts or links with the secondary spiral inducement in it an alternate EMF. ( 111 press releases ). The measure up transformer is located in the tubing current subdivision of the circuit where the kVp’s are selected and the strength or incursion of the beam is determined.
( Step Down Transformer ) In the measure down transformer the primary spiral will hold more twists than the secondary spiral which will ensue in lower Vs but more As. The measure down transformer is
located in the fibril circuit subdivision of the circuit after the ma has been selected which determines the figure of x beams to be emitted. The transformer jurisprudence describes how electric current and voltage alteration from the primary spiral to the secondary spiral. The expression for this jurisprudence is Vs/Vp = Np/Ns.
( Energy Losses ) In a perfect universe. transformers would be 100 % effectual but in world. they are merely 90 % -95 % effectual due to energy losingss. In most instances the power lost is normally in the signifier of heat. There are three types of losingss of power in transformers: Copper losingss. Eddy current losingss and Hysteresis losingss. Copper losingss are due to resistance in the spirals. Heat is produced by the electrical currents in the music directors of the twists. This type of loss can be reduced by utilizing Cu wire of equal diameter. A thicker wire creates less energy waste.
Eddy current losingss are twirling currents in the nucleus that are caused by jumping magnetic flux set up in the nucleus by jumping current which produces heat. Eddy current losingss can be reduced by doing the nucleus of a stack of laminated Si steel home bases. These home bases are electrically insulated from each other and increase electrical opposition of nucleus which reduces the size of the eddy currents. The 3rd type of loss is Hysteresis losingss. This loss is caused by changeless rearrangement of the magnetic Fieldss which produce heat in the nucleus. This can be reduced by utilizing a laminated Si steel nucleus.
( Types of Transformers ) A transformer is a device that changes an jumping current from low electromotive force to high electromotive force or from high to low. They transfer electrical energy from one circuit to another without utilizing any traveling parts or any electrical contact between the two circuits. They operate merely on an alternating current and work away of common initiation.
There are a assortment of different transformers that are made for different intents and even though the designs are different they all are similar in their intent. The transformers that I am traveling to speak about in this paper are:
- Closed nucleus
- Shell type and autotransformers.
Closed nucleus transformers have an Fe nucleus that is non a individual piece but made up of beds of laminated Fe. Layering helps cut down energy loss which consequences in greater efficiency. It is a closed ring with which two to a great extent insulated spirals are wrapped around it.
This provides a uninterrupted way for magnetic flux so merely a little fraction of power is lost by escape. Shell type transformers are the most advanced and the most used type of transformer. This type of transformer confines more of the magnetic field lines of the primary twist because the secondary twist is wrapped around it so it is technically two closed nucleuss which makes this type more efficient than the closed nucleus.
The autotransformer has one Fe nucleus and merely one twist of wire around it. This individual weaving serves as both the primary and the secondary twist. The autotransformer is the lone 1 that operates
on ego initiation which is where the magnetic field of a spiral induces a counter EMF in the spiral itself. This ego induced electromotive force will oppose the applied current.
( Rectifiers ) When there is a current coming in from the wall mercantile establishment it is coming in at 60 Hz of jumping current. That current will alter waies 120 times per second. The ten beam tubing nevertheless requires a direct current which means that negatrons merely flow in one way. X beams are produced by the acceleration of negatrons from the cathode to the anode and can non be produced in the opposite way. Because the cathode assembly is constructed so that it can non defy a batch of heat reversal of the flow of negatrons would be bad for the x beam tubing.
Electron flow should merely be in the cathode to anode way hence the secondary electromotive force of the high electromotive force transformer has to be rectified which means that the incoming alternating current must be converted to direct current. To make this. a device called a rectifier is needed. Rectification is accomplished with devices called rectifying tubes which is an electronic device that contains two electrodes.
These electrodes are located between the secondary spiral of the transformer and the x beam tubing and they merely allow the flow of negatrons in one way. Presently rectifiers are made of Si but they used to be vacuum tubings called valve tubings that were similar to the x beam tubing. The advantage of Si rectifiers over the valve tubings are its compact size there is no fibril. it lasts longer it has low contrary current and a low forward electromotive force bead. Conductors such as metal or H2O allow the free flow of negatrons and dielectrics such as plastic or gum elastic suppress the flow of negatrons.
Semiconductors such as Si are between the two in their ability to carry on electricity. Semiconductors are classed into two types: N-type and P-type. N-type semiconducting materials have slackly bound negatrons that are free to travel and P-type semiconducting materials have infinites called holes. where there are no negatrons. These holes are merely a infinite between two objects and can travel every bit easy as negatrons. A P-N junction is formed when a bantam crystal of N-type stuff is placed in contact with P-type stuff.
If a higher potency is placed on the p side of the junction the negatrons and holes will travel towards the junction and finally travel across it doing an electrical current. If a positive potency is placed on the n side of the junction the negatrons and the holes will be swept off from the junction which will ensue in no electrical current passing through the p-n junction. Because a solid province p-n junction will merely carry on electricity in one way this is called a solid province rectifying tube.
( Waveforms ) There are three types of rectifications: ego half moving ridge and full moving ridge. In Self rectification there are no rectifying tubes and the x beam tubing itself will work as the rectifier but when one or two
rectifying tubes are placed in the circuit that stops the negative flow of negatrons it is called Half wave rectification. During half wave rectification. the reverse electromotive force is removed from the supply to the tubing. The electromotive force is non allowed to swing negatively during the negative half of its rhythm ensuing in no electrical current.
However during the positive rhythm there is a current being passed through the x beam tubing. As a consequence of the half wave rhythm there are a series of positive pulsations separated by spreads when the negative current is non conducted. This is a rectified current because the negatrons are merely fluxing in one way. Half wave rectification produces 60 pulsations per second.
Because half wave rectification merely uses half of the power being supplied and besides requires twice the exposure it is non ideal. Therefore it is possible to hold a circuit that will rectify the full alternating wave form. This is called Full moving ridge rectification. Full moving ridge rectification is used in about all stationary x beam machines and contain at least 4 rectifying tubes. During this rectification the negative half rhythm is reversed so that the anode is ever positive.
There are no spreads in the end product wave form and the input wave form is rectified into useable end product. This consequences in throbing direct current. The advantage of utilizing full moving ridge rectification over half moving ridge is the exposure clip is cut in half which increases the tubing evaluation or heat burden capacity. Full wave rectification produces 120 pulsations per second and the minimal exposure clip is 8ms.
The ego half moving ridge and full moving ridge rectification wave forms that were antecedently discussed are all produced by individual stage which consequence in a pulsating ten beam beam. Single stage power uses merely one autotransformer and has one individual stage on the wave form that goes from zero to the maximal positive potency back to zero so to a maximal negative potency and back to nothing once more. Because the x beams produced during individual stage wave forms have low energy and small perviousness due to their close nothing values. they are of small diagnostic value.
One manner they have figured out how to acquire better consequences is to utilize three stage power. Three stage power generates three coincident electromotive force wave forms that are out of measure with one another this causes about changeless high electromotive force. Compared to the 2 pulsations of the individual stage power the three stage power has six pulsations per 1/60 seconds. There is one autotransformer for each stage. With the three stage three autotransformers ( one for each stage ) are needed for kV choice.
They are arranged in either star or delta constellation. A delta transformer twist is connected between stages of a three stage system. A star transformer connects each weaving from a stage wire to a common impersonal point. ( Wikipedia ) Three stage circuits have all delta wound primary spirals but differ in signifier of secondary. The evaluations of three stage power are 1600 ma. 150 kilovolt and the exposure clip
is every bit low as 1ms.
High frequence generators are increasing application in bring forthing high electromotive force for may imaging systems. One advantage to the high frequence generator is its size. They are much smaller than the 60 Hz generators and they produce a close changeless electromotive force wave form which improves the image quality and lowers patient dosage.
High frequence generators were foremost used in portable ten beam machines but now they are used in most modern equipment today. High frequence electromotive force generators us inverter circuits which are high velocity switches besides known as choppers. These convert direct current into a series of square pulsations.
( Voltage Ripple ) Another manner to qualify electromotive force wave forms is by Voltage Ripple. Voltage rippling is the little unwanted residuary periodic fluctuation of the direct current at the end product phase of a power supply. This is due to deficient suppression of the alternating wave forms with in the power supplies. ( Wikipedia ) A larger rippling means less effectual filtering and a smaller rippling means more effectual filtering. Single stage power has 100 % electromotive force rippling significance that the electromotive force varies from zero to its maximal value.
The three stage six pulse power which has 6 rectifying tubes and 1 star and 2 delta has a 14 % rippling so the electromotive force that is supplied ne'er falls below 86 % of the soap value. An betterment was made in the three stage power utilizing 12 pulsations alternatively of 6. The three stage 12 pulsation which has 12 rectifying tubes 1 star and 2 delta has merely a 4 % electromotive force rippling and so the electromotive force does non fall below 96 % of its soap value.
High frequence generators merely have a 1 % electromotive force rippling ensuing in better ten beam quality and measure which is the biggest advantage in the electromotive force with the least sum of rippling. When the electromotive force rippling is low it increases radiation quality because fewer negatrons are go throughing from the cathode to the anode bring forthing low energy x beams.
Flow of current through the High Voltage Generator
Once the electricity leaves the control console. in the tubing current portion. the current leaves the secondary side of the autotransformer and goes to the primary side of the high electromotive force transformer. It goes through the measure up transformer where the where the electromotive force is stepped up from Vs to kVs due to the fact that there are more twists on the secondary side than there are on the primary side. After the current leaves the measure up transformer it passes through the secondary side of the high electromotive force transformer to the rectifiers which change the jumping current to direct current that is needed in the tubing.
There are two types of solid province rectifying tubes P-type and N-type semiconducting materials that make the current flow in one way. On the secondary side of the rectifier is the ma metre which measures the amperage. After the current has been changed to direct current it goes to the cathode in the x beam
tubing. In the filament current portion. the jumping current goes through the ma picker in the control console and is so carried to the primary side of the filament transformer which besides works by electromagnetic common initiation.
In this circuit. the electromotive force goes through the measure down transformer intending that there are more twists on the primary side than there are on the secondary side where the electromotive force is stepped down to a lower electromotive force. From here it goes to the focal topographic point picker which picks the fibril to be used to boil off negatrons and the current is so sent to the cathode in the x beam tubing.
The X beam Tube
In 1895 Wilhelm Roentgen discovered x beams utilizing a Crookes Tube. However. in 1913 William Coolidge made betterments to the tubing so today we use a Coolidge tubing to bring forth x beams. The ten beam tubing is a portion of the imagination system that is non seen by the engineers. That is because it is contained within a protective lodging doing it unaccessible.
There are two chief parts to the x beam tubing. Those are the Cathode and the Anode. Each one of these is considered an electrode and because there are two electrodes in the Tube it makes it a rectifying tube. The exterior of the x beam tubing has three parts: the support construction the protective lodging and the glass or metal enclosure. The interior is where the Cathode and Anode are contained.
( Support System ) The first portion of the external constituents I want to discourse is the support system. There are three types of support systems for ten beam tubings: Ceiling support.
Floor to Ceiling support and C-arm support. Ceiling support is the most used support system out at that place. It consists of two perpendicular sets of ceiling mounted tracks leting a longitudinal and cross motion of the x beam tubing. The floor to ceiling support system has merely a individual column with rollers at the terminal.
These are attached to the ceiling mounted tracks and the floor mounted tracks leting the tubing to skid up and down as the column rotates. A different type of this support system has the column placed on a individual floor supported system with one or two floor mounted tracks. The C-arm support system gets at that place name because they are shaped like a “C” . These support systems are mounted to the ceiling and supply flexible tubing placement.
( Protective Housing ) The 2nd portion of the external constituents is the protective lodging. This protective lodging is what is around the x beam tubing. It is lead lined to forestall inordinate radiation escape. Escape radiation is considered the x rays that flight from the protective lodging ensuing in unneeded exposure to the patient but plays no portion in accomplishing diagnostic information. If the lodging is designed decently. it will cut down the escape radiation to less than 100 mR/hr at 1m when it is operated at maximal conditions. The ten beams that do accomplish diagnostic information are called the utile beam. These are the x rays
that are emitted through a window that is 5cm squared.
When ten beams are produced. they are emitted isotropically which means that they are emitted with equal strength in all waies. Another map of the lodging is to forestall electric daze to the patient and to the radiographer by being designed with high electromotive force receptacles. The protective lodging besides provides mechanical support for the x beam tubing protecting it from harm due to unsmooth handling. Some contain oil around the tubing that acts as an dielectric to forestall electric daze and besides as a thermic shock absorber to disperse the heat. Some besides contain a chilling fan to chill the machine or the tubing.
When the tubing is heated the oil expands but if there is excessively much enlargement it activates a microswitch which will forestall the tubing from being used once more until it is cooled.
( Envelope ) The ten beam tubing is an electronic vacuity that creates efficient ten beam production and longer tube life. The vacuity is an empty infinite that is air tight. leting negatrons to travel freely with in the tubing. There are two types of envelopes: a glass envelope and a metal envelope.
The glass envelope is made of Pyrex glass which allows it to be able to with stand the big sum of heat that is produced. This enclosure maintains a vacuity inside the tubing. If merely a small spot of gas gets in the enclosure. the negatron flow from the cathode to the anode is reduced which produces more heat and fewer x beams. As the glass enclosure ages. some of the wolfram vaporizes and coats the interior of the glass enclosure. When this happens. it can alter the belongingss of the tubing which will let the tubing current to roll and interact with the glass enclosure ensuing in curving and tube failure.
There has been an betterment in the tubing that is a metal envelope alternatively of glass. Almost all high capacity x beam tubings now use metal enclosure alternatively of glass. This is because the metal enclosure maintains a changeless electric potency between the negatrons of the tubing current and the enclosure which consequences in longer life of the tubing.
( Cathode ) The ten beam tubing contains two electrodes: the cathode and the anode. The cathode is on the right side and it is the negative side of the x beam tubing. It contains two chief parts. the fibril and a focusing cup.
The fibril is a spiral of wire that is about 2mm in diameter and 1 or 2 centimeter long. When the tubing fibril is heated. it emits negatrons. When the current through the fibril is high. the outer shell negatrons are boiled away and removed from the fibril. This “boiling off” is called Thermionic Emission. The fibril is made of tittering wolfram has an atomic figure of 74 which consequences in high efficiency production and high energy x beams and provides for a higher thermionic emanation than other metals. It has a runing point of 3410 grades Celsius so it will non fire out rapidly and it doesn’t vaporize rapidly.
% to 2 % of Th that is added to the tungsten fibril enhances the efficiency of thermionic emanation and gives it a longer life. Electrons carry a negative charge and which causes them to drive each other. Therefore when they are emitted from the fibril. the negatrons are in the locality of the fibril before they are accelerated to the anode doing a cloud of negatrons to organize around the fibril. This cloud is called a infinite charge. This infinite charge makes it hard for negatrons to be emitted by the fibril because of electrostatic repulsive force. this is called infinite charge consequence.
The focusing cup is a metal cup in which the fibril is imbedded. The negatrons that are thrown from the cathode to the anode are negatively charged and because of electrostatic repulsive force the negatron beam tends to distribute out some even losing the anode wholly. The focusing cup is besides negatively charged and it electrostatically confines the negatron beam to a little country of the anode. How effectual the focusing cup is determined by its size and form by its charge the filament size and form and the fibril in the focusing cup.
( Anode ) The anode is on the left side and it is the positive side of the tubing. This is the portion of the tubing where the accelerated negatrons move to after the kilovolt has been applied to the tubing. It has three chief maps in an ten beam tubing: it is an electrical music director. a thermic dissipater and mechanical support.
The anode serves as an electrical music director because it receives negatrons emitted by the cathode and conducts them through the tubing to the connecting overseas telegrams and back to the high electromotive force generator. It must be a good thermal dissipater because when the negatrons that are being thrown from the cathode to the anode 99 % of them are converted to heat which needs to be dissipated rapidly. The anode besides provides support for the mark. There are two types of Anodes: Rotating and Stationary
( Stationary and Rotating Anodes ) Stationary anodes were introduced in 1936. They have a lower heat capacity and are used when high tubing current and power are non required such as in dental ten beam imaging systems and some portable machines. All other ten beam machines use a rotating anode because they must be capable of bring forthing high strength x beam beams in a short sum of clip.
Revolving anodes allow the negatron beam to interact with a larger mark country so all of the warming of the anode is non merely in one little topographic point like it is in the stationary anode. A revolving anode is a disc with a diameter of about 3-5 inches the larger the disc the more of a work load there will be. Most revolving anodes rotate 3. 600 revolutions per minute and the high capacity tubings rotate at velocities up to 10. 000 revolutions per minute. The heat capacity can be increased with higher rotary motion velocities.
The root of the anode is normally made of Mo because
it is a hapless heat music director and it is narrow to cut down the thermic conduction. It is located between the anode and the rotor. When the rotor mechanism of a revolving anode fails it becomes over heated and cavities or clefts doing tube failure. A revolving anode is driven by an electromagnetic initiation motor. This motor consists of two chief parts: the stator and the rotor.
These two parts are separated from each other by the glass or metal enclosure. The portion that is outside the enclosure is called the stator which consists of a series of electromagnets that are every bit spaced around the cervix of the tubing. The portion inside the enclosure is the rotor. It is made up of bars of Cu and soft Fe fabricated into one mass. When the tech pushes the exposure button on the console there will be a short hold before the exposure is made. During this clip the rotor is accelerated to the appropriate revolutions per minute while the fibril is being heated.
After the exposure has been made. the rotor slows down and stops with in one minute because the initiation motor is put into contrary.
( Target ) The mark is country of the anode where the negatrons work stoppage after go forthing the cathode. In the stationary anode the mark is embedded in the Cu anode and does non travel. therefore the negatrons will strike the mark in the same topographic point over and over doing it to have on down rapidly. In revolving anode the full disc is the mark which gives the beam a larger mark country to interact with.
The stuff used in marks is Tungsten because of its high atomic figure of 74 and its high thaw point of 3. 400 grades Celsius. Adding Rhenium to the tungsten gives it added strength so that it can with stand the emphasiss of high velocity rotary motion and the effects of insistent enlargement and contraction. ( Line Focus Principal ) When ten beams are emitted. they strike the focal topographic point on the mark.
The focal topographic point is the existent x beam beginning. Smaller focal musca volitanss have better spacial declaration of the image but when the size of the focal topographic point decreases the heat of the mark is put onto a smaller country. A design to let a big country for heating while keeping a little focal point topographic point is called Line Focus Principal. By angling the mark it makes the effectual country of the mark much smaller than the existent country of negatron interaction. Actual focal topographic point size is the country of the mark that is being hit with negatrons from the fibril.
The effectual focal topographic point size is the fanciful line that can be drawn based on the existent focal topographic point size versus the angle of the anode. This is the portion that is projected onto the patient and the IR making an image. One advantage to angling the mark is that it helps disperse heat. while making better item. Diagnostic ten beam tubings have mark angles runing from 5 grades
to 20 grades. When the angle is made smaller the effectual focal topographic point size will besides be smaller.
Flow of current through the x beam tubing. When the radiologic engineer pushes the exposure button on the control console there is a short hold before the exposure is made. This hold is to let the rotor to accelerated to the desired RPM which will do the anode to whirl. In the tubing circuit the rotor is a shaft made of bars made of Cu and soft Fe and it is located on the interior of the enclosure of the tubing.
On the exterior of the exposure is the stator which consists of a series of electromagnets that are every bit spaced around the cervix of the tubing. The stator is what causes the rotor to whirl by the rule of electromagnetic initiation. In the fibril circuit during the spinning of the rotor and anode the fibrils on the cathode are heating up.
Once the fibrils are heated sufficiently the negatrons are boiled off by a procedure called Thermionic emanation. This causes a little rise in the filament current consequences in a big rise in the tubing current. After the negatrons have been boiled off of the cathode they continue to hang about. This cloud of negatrons is called a infinite charge. Those negatrons are negatively charged and because of this electrostatic repulsive force takes topographic point significance they are repelled by the cathode.
This procedure is known as a infinite charge consequence. When the kVp in the tubing circuit is applied to the tubing the negatrons in the infinite charge will be thrown across to the anode. The focusing cup which is what contains the fibril is besides negatively charged so it electrostatically confines the negatron beam to a little country of the anode. The anode is positively charged which attracts the negatrons to it. When the negatrons are thrown from the cathode to the anode they hit the mark.
The anode is angled which causes the mark to hold a larger country hence ensuing in a smaller effectual focal topographic point size. When the negatrons that are thrown to the anode hit the mark they are redirected down to the patient organizing an image on the IR. The country that reaches the patient called line focal point rule. After the current goes to the cathode because it is now direct current it is redirected back to the high electromotive force subdivision.
Summary of the flow of current through the X-ray Imaging System. The flow of current through the control console of an x-ray machine starts with the power coming in from the wall mercantile establishment which receives its electricity from a beginning outside the edifice. The current goes to primary side of the control console and so to the line compensator which maintains the electromotive force at a steady 220v. It is so supplied to the primary side of the autotransformer.
The autotransformer steps up the electromotive force by electrostatic ego initiation which makes the input twice the electromotive force value. The lights-outs on the secondary side of the autotransformer are what are used to choose
the major and minor kVp they are pre-read by the kV metre on the secondary side. After the electricity leaves the autotransformer it is divided into two separate currents the tubing current and the filament current. The electromotive force that is carried through the tubing current so goes to the measure up transformer on the primary side of the high electromotive force subdivision.
The electromotive force that is carried through the filament current is carried to the ma picker. which is a variable resistor that has a series of resistance spirals although today a saturable reactor is preferred. It has an Fe nucleus that is saturated with magnetic flux. The current is so passed to the measure down transformer which is besides in the primary side of the high electromotive force subdivision. When the exposure switch is pressed. the current is passed to the high electromotive force subdivision. The exposure timer is what regulates how much of an exposure is made. Its intent is to do or interrupt the high electromotive force across the ten beam tubing.
Once the electricity leaves the control console. in the tubing current portion the current leaves the secondary side of the autotransformer and goes to the primary side of the high electromotive force transformer.
It goes through the measure up transformer where the where the electromotive force is stepped up from Vs to kVs due to the fact that there are more twists on the secondary side than there are on the primary side. After the current leaves the measure up transformer it passes through the secondary side of the high electromotive force transformer to the rectifiers which change the jumping current to direct current that is needed in the tubing.
There are two types of solid province rectifying tubes. P-type and N-type semiconducting materials that make the current flow in one way. On the secondary side of the rectifier is the ma metre which measures the amperage. After the current has been changed to direct current it goes to the cathode in the x beam tubing. In the filament current portion the jumping current goes through the ma picker in the control console and is so carried to the primary side of the filament transformer which besides works by electromagnetic common initiation.
In this circuit. the electromotive force goes through the measure down transformer intending that there are more twists on the primary side than there are on the secondary side where the electromotive force is stepped down to a lower electromotive force. From here it goes to the focal topographic point picker which picks the fibril to be used to boil off negatrons and the current is so sent to the cathode in the x beam tubing subdivision.
When the radiologic engineer pushes the exposure button on the control console there is a short hold before the exposure is made. This hold is to let the rotor to accelerated to the desired RPM which will do the anode to whirl. In the tubing circuit the rotor is a shaft made of bars made of Cu and soft Fe and it is located on the interior of the enclosure
of the tubing.
On the exterior of the exposure is the stator. which consists of a series of electromagnets that are every bit spaced around the cervix of the tubing. The stator is what causes the rotor to whirl by the rule of electromagnetic initiation. In the fibril circuit during the spinning of the rotor and anode the fibrils on the cathode are heating up. Once the fibrils are heated sufficiently the negatrons are boiled off by a procedure called Thermionic emanation.
This causes a little rise in the filament current consequences in a big rise in the tubing current. After the negatrons have been boiled off of the cathode. they continue to hang about. This cloud of negatrons is called a infinite charge. Those negatrons are negatively charged and because of this electrostatic repulsive force takes topographic point significance they are repelled by the cathode.
This procedure is known as a infinite charge consequence. When the kVp in the tubing circuit is applied to the tubing the negatrons in the infinite charge will be thrown across to the anode. The focusing cup which is what contains the fibril is besides negatively charged so it electrostatically confines the negatron beam to a little country of the anode.
The anode is positively charged which attracts the negatrons to it. When the negatrons are thrown from the cathode to the anode they hit the mark. The anode is angled which causes the mark to hold a larger country hence ensuing in a smaller effectual focal topographic point size. When the negatrons that are thrown to the anode hit the mark they are redirected down to the patient organizing an image on the IR.
The country that reaches the patient called line focal point rule. After the current goes to the cathode. because it is now direct current and can merely travel one way it is redirected back to the high electromotive force subdivision.
- hypertext transfer protocol: //www. ndt-ed. org/EducationResources/CommunityCollege/Radiography/EquipmentMaterials/xrayGenerators. htm
- hypertext transfer protocol: //faculty. mwsu. edu/radsci/gary. morrison/RADS_1513/Chapters_5 & A ; 39/X-ray_Circuits_and_Equipment. pdf
- hypertext transfer protocol: //www. wikiradiography. com/page/Physics+of+the+X-Ray+Tube
- hypertext transfer protocol: //en. wikipedia. org/wiki/
- Sinclair Tousey. Medical electricity and Rontgen beams ( 3rd Edition ) W. B. Saunders Co. 1921
- Electric Current essays
- Energy essays
- Density essays
- Thermodynamics essays
- Motion essays
- Atom essays
- Sound essays
- Electricity essays
- Nuclear Power essays
- Temperature essays
- Physiology essays
- Light essays
- Force essays
- Heat essays
- Speed essays
- Big Bang Theory essays
- Energy Development essays
- Rubber essays
- The elements essays
- Voltage essays
- Solar Energy essays
- Nuclear Energy essays
- Alternative Energy essays
- Refraction essays
- Melting essays
- sound cards essays
- Nuclear Family essays
- Sensory System essays
- Agriculture essays
- Albert einstein essays
- Animals essays
- Archaeology essays
- Bear essays
- Biology essays
- Birds essays
- Butterfly essays
- Cat essays
- Charles Darwin essays
- Chemistry essays
- Dinosaur essays
- Discovery essays
- Dolphin essays
- Elephant essays
- Eli Whitney essays
- Environmental Science essays
- Evolution essays
- Excavation essays
- Fish essays
- Genetics essays
- Horse essays