C-arm and operation theater radiography

C-arm and operation theater radiography

Where operative procedure requires imaging control, the radiographer plays an important part in the form of the orthopaedic theater team. Fluoroscopy imaging is required during the Trauma Orthopaedic Procedure. But radiographer is also required during some Non-Trauma corrective orthopaedic procedure. However in both instances the radiographer is required to work primarily in an operation theater environment using a mobile C-Arm image intensifier

Non-Trauma corrective orthopaedic surgery

Nowadays, a large number of Non-Trauma corrective orthopaedic procedures are performed. In which there are a large number of joint replacements such as severe osteoarthritis (OA) of Hip joint is treated with prosthetic total hip joint replacement, which does not require imaging control (C-Arm) at all. Still, more complex pediatric operative procedures (e.g. osteotomies for joint alignment) require imaging control.

Trauma Orthopaedic Surgery

Most of the radiographer's work during the Orthopaedic Procedure focuses on the aid of the following Trauma Orthopaedic surgery - Successful reduction of fracture.  Implantation and removal of internal or external fixing devices.

K-wire insertion

K-wire insertion is mostly done for corrective simple fracture extrimity surgery of extrimity such as simple fracture of fingers, hands, wrists, elbow and feet. Imaging controls are required in these procedures. Before processing, it is ensured that the C-Arm is rotating up to 180 °. To reduce magnification and improve image quality, keep the affected area as close to the detector as possible.

Open Reduction and Internal Fixations

Open Reduction and Internal Fixations  are mostly done in situations where the fracture cannot be satisfactorily conducted by any other means. The mid shaft forearm fracture can be stabilized with compression plate and screws. In this situation, to reduce magnification and improve image quality, keep the affected area as close to the detector as possible.

This imaging control is mostly required at the beginning and end of the procedure. During the operation the surgeon can directly view the fracture site and the fixation device.

During the process, collimation should be used in the area of ​​interest, which reduces scatter radiaiton and improves image quality.

Intramedullary Nailing 

During intermittent imaging control is required during the entire procedure. This not only tells the surgeon what is the path of the nail in the medulla in the long bone but also helps in proximal and distal locking in the cortex by the nail screw.

Interventional Procedure

Imaging control is also required during this time. There are many procedures where the radiographer has to assist during the procedure like-

Retrograde pyelography

It is also called ascending pyelography. In this, organic iodinated contrast agents are mechanically filled with renal calyces and pelvis and seen with the help of C-Arm. For this, with the help of cystoscopy, a catheter is attached to locate the affected kidney. For this, a mobile C-Arm image intensifier / solid state detector and radiolucent theater table which are suitable for cystoscopy are used. The patient is made supine. The C-Arm is set for PA projection

Percutaneous Nephrolithotomy (PCNL) 

This is an interventional procedure in which the renal stone is removed with the help of a direct nephrotomy tract. For this, a mobile C-Arm image intensifier / solid state detector and radiolucent theater table which are suitable for cystoscopy are used. In this, large renal stone is damaged by electrohydraulic lithotripsy or ultrasound shock waves.

pelvis and hip all positions

pelvis and hip all positions

Pelvic with both hip -
Pelvis antero-posterior both hip is a common projection used for first evaluation of pelvis bone and hip joint. The positioning of the pelvis and both hip is the same, only the centering point of the x-ray beam is different. Comparative study of both hip joints can be done in AP image and fracture in pubic ramus is also covered.

Position -
pelvis ap with both hip position The patient puts the supine on the bucky table and keeps the median Sagittal Plane coincident of the perpendicular and midline of the cassette.  

Both anterior superior iliac spine are placed at the same distance from the table so that there is no rotation in the patient

 At this time the coronal plane is parallel to the image receptor, for this we have non-opaque pad under the buttock. For this, CR cassette (35 X 43) of sufficient length is used so that the entire bony pelvis is included in the radiyograph.

The limbs are slightly abducted and rotated internally so that the neck of the femer image is parallel to the receptor.

Direction and Location of X-ray beam Collimated vertical x ray beam centers between the anterior superior iliac spine and the line joining the upper border of the symphysis pubis. The top edge of the image receptor is placed 5cm above the upper border of the iliac crest so that the entire bony pelvis is included in the radiograph due to the divergent beam.

Image characteristics

Both hip chant should appear in both hip image and upper third femora image. In Pelvis view both iliac crest, proximal femora as well as lesser trochanter image should be visible correctly. To prove that there is no rotation in the image, the dimensions of both bones should be same and both obturator foramina should be of the same shape. Shenton's line should be visible correctly. It is the curve between the inferior aspect of the femoral neck and the inferior margin of the superior pubic remi. Any type of disruption in this curve indicates femoral neck fracture.

Hip joints frog leg projection

This projection is done for comparison of both hip joint with basic antero-posterior projection. This is done in children for osterochondritis of capital epiphysis (Perthe's disease) and slipped upper femoral epiphysis (SUFE). This position is called the frog position. According to departmental protocol, gonad protection device is used.

position
frog lateral radiograph for hip joint The patient puts the supine on the bucky table and keeps the median Sagittal Plane coincident of the perpendicular and midline of the cassette. Both anterior superior iliac spine are placed at the same distance from the table so that there is no rotation in

the patient. Flex both hips and knees of the patient and rotate both limbs to lateral 60 °. In this case, both the knees are separated from each other and the planter surface of both feet comes in contact with each other. For this, CR cassette (35 X 43) of sufficient length is used so that the entire bony pelvis is included in the radiyograph. Center the image receptor at the level of the femoral pulse.

Collimated vertical x ray beam centers between the line of the femoral pulse.

Hip joint ap view

Position -
The patient puts the supine on the bucky table and puts the median Sagittal Plane perpendicular to the cassette.

Both anterior superior iliac spine are placed at the same distance from the table so that there is no rotation in the patient.

At this time the coronal plane is parallel to the image receptor, for this we have non-opaque pad under the buttock. The hip joint is detected by palpate the femoral pulse and placing it in the center of the image receptor. The limbs are slightly abducted and rotated internally so that the neck of the femer image is parallel to the receptor.

The collimated vertical x ray beam centers vertically on the femoral pulse 2.5cm away from the line joining the anterior superior iliac spine and the upper border of the symphysis pubis. The primary beam collimates on the examination area and uses gonad protection.

The image should include the proximal 1/3 part of the femer and when X-ray arthroplasty is performed to check the positioning and integrity, the prosthesis and femer should be visible in full length in the radiograph.

chest x ray

CHEST X RAY

*         CHEST X RAY POSTERIOR ANTERIOR (PA VIEW) INTRODUCTION - In the chest x-ray, radio graphs of the organ located in the thoracic part of the body are taken. The thoracic cavity contains some of the main organs of its body, such as the heart, lungs, trachea, esophagus, aorta, etc. To protect all of this, thoracic cages are removed, in which anteriorly sternum, posteriorly vertebral column and lateral ribs are located.

·         THE CASES IN WHICH WE DO -Fever,chest pain,ribs broken,Heart Failure,lung cancer etc  

·         PREPARATION - If there is any surgical implanted device of the patient like pacemaker or heart valve, then the doctor should be told first. In this case, the doctor may consider any other alternative of chest x-ray such as CT Scan or Sonography etc. Before X-ray, the patient is asked to remove the clothes above his waist and wear a hospital gown.

·         CENTERING POINT - at the level of the 7th thoracic vertebrae,near the inferior angle of scapulae

·        COLLIMATION  - superiorly 5 cm above the shoulder joint to allow proper watching of upper airways

·         CASSETTE ORIENTATION - landscape or portrait  (depend upon patients)

·        CASSETTE SIZE - 35*43

·        EXPOSURE -  kv- 101-109 and mas - 4-5

·         CENTRAL RAY- perpendicular to cassette

·        FFD- 180 cm

·        grid - yes

·        RESPIRATION- suspended inspiration

FILM CONSTRUCTION

FILM CONSTRUCTION

This film basically has two parts -- the base and the emulsion Fig. 9.1). Most films have the emulsion coated on both side and therefore are called double-emulsion film. Between the emulsion and the base is a thin coating of material called the adhesive layer to ensure uniform adhesion of the emulsion to the base . The emulsion is enclosed by a protective covering of gelatin, called the super coating. This protects the emulsion from scratching, pressure, and contamination during use and processing and allows for relatively rough manipulation of X-ray film before exposure. The thickness  of the 5. sheet of radiographic film ranges form 200-300 um (about10.25 mm).

The double coating film helps in getting better density and contrast and also to reduce the exposure required. This also helps to avoid curling of the film.

The Base - The base is the foundation for radio graphic film and it provides a rigid structure into which the emulsion can be coated. It is flexible and unbreakable and allows easy handling of films. The base of radio graphic film maintains its size and shape during use and processing so that it does not contribute to image distortion. This property of the base is known as dimensional stability. The base is inert so that sensitometric property of the emulsion is not affected. The base is of uniform lucency for viewing the radio graphs clearly. During manufacture, dye is added to the base to slightly tint the film blue. Compared with untinted film, this coloring results in less eye strain and fatigue for the  radiologist.

Two types of bases are available-cellulose triacetate and polyester. Polyester is more resistant to wrapping with age and stronger than cellulose triacetate. Its dimensional stability is superior. Polyester bases are thinner than triacetate bases (approx. 160 um compared with 180 um respectively) but are just as strong. The polyester base is similar in composition to the polyester fibres in clothing

The Emulsion - The emulsion is the heart of the X-ray film. It is the material 2 which X-ray or light photons from screen interact and transfer information. The emulsion consists of a homogenous mixture of gelatin and silver halide crystals. Besides above, also contains various additives like chemical sensitizers, wetting agents antifoggants, hardeners, etc. which impart the required qualities to the film. Emulsion should be clear so at it transmits light and is sufficiently porous for the processing chemicals to penetrate to the crystals of silver halide during processing. its principal function is to provide mechanical support for the silver halide crystals by holding them uniformly dispersed.

HYSTERESIS LOOP

HYSTERESIS LOOP

The variation of flux density with magnetic field intensity is not linear. A graph plotted between B and Has shown in the Figure 2.13. is called B-H curve. From this graph, it is clear that the curve rises rapidly at first indicating big change in the value of B for a corresponding small change in H. The slope of this curve gradually decreases indicating a small change in 3 for increasingly larger values of H. A stage is reached when the slope of the curve becomes constant and this condition is known as saturation..

If we take ferromagnetic material in completely demagnetized state and make it to undergo through a cycle of magnetization in which H is increased from zero to a maximum, then decreases to zero, then reversed and again taken to-H max and finally brought back to zero. The variation of B with respect to H can be represented by a closed hysteresis loop shown in the figure.

A study of hysteresis loop of different magnetic materials helps us to know their magnetic properties. For example, the area of the hysteresis loop for soft iron is smaller than for  steel. Hence energy lost per cycle is correspondingly less. So soft iron is preferred steel for cores of dynamos, transformers, etc. which are subjected to a large number of  cycles so that the loss of energy may be minimum

ELECTROMAGNETIC RADIATION

ELECTROMAGNETIC RADIATION

Electromagnetic Radiation - An electric charge is surrounded by an electric field. If the charge moves, a magnetic field is produced. When the charge undergoes an acceleration or deceleration, the magnetic and the electric fields of the charge will vary. The combined variation of the electric and magnetic fields results in loss of energy. The charge radiates this energy in a form known as electromagnetic radiation. The electromagnetic radiation moves in the form of sinusoidal waves .

"The electromagnetic wave possess wavelength (a), frequency (v) and velocity (c). The distance between two consecutive positive peaks is known as wavelength. The number of cycles of the wave which pass a fixed point per second is known as the frequency of the wave. The velocity of the wave is the distance traveled per second by the wave. The relation between wavelength, frequency and velocity of the electromagnetic wave can be expressed as c - v. All electromagnetic waves, travel at the same velocity in a given medium. In vacuum the velocity is about 2.998 * 108 meter per second.

Moving Coil Galvanometer

Electrical Instruments Electrical instruments are of fundamental importance in the field of measurements. They are almost based on the magnetic effects associated with current. Some of the common electrical instruments are () moving coil galvanometer (ii) ammeter (iii) voltmeter, and (iv) the multimeter.

 Moving Coil Galvanometer

 Moving Coil Galvanometer - A galvanometer is a device used for indicating the flow of current in a circuit. There are two types of galvanometers namely (1) moving magnet, and (ii) moving coil type. The most commonly used galvanometer is the moving coil type.

The moving coil galvanometer was first devised by Lord Kelvin and later modified by D'Arsonval. The principle on which the galvanometer works is that when a conductor carrying current is placed in a magnetic field, experiences a mechanical force given by Fleming's left hand rule.

It consists of a rectangular coil of fine copper wire suspended by a thin phosphor bronze e P) Between the poles pieces of a horse-shoe magnet. P carries a small concave mirror (M) to measure small deflections of the coil with a lamp and scale arrangement (Fig. 2.18). The phosphor bronze wired provides the controlling couple for the moving coil. The current enters and leaves the coil via suitable terminals connected to P and the fine spring Q. The pole pieces of the horse shoe magnets are curved inside and a soft iron piece is placed inside the coil without touching it. This makes the lines of magnetic force to be concentric towards the center of the space between the poles and hence render radial magnetic field. When current (l) is passed through the coil, the coil gets deflected through an angle (0)

The relation between 1 and is given by 1 = Ge where G=C/nBA, which is known as galvanometer constant.

C - Is the torsional couple per unit twist

n - Is the number of turns in the coil

B - is the magnetic induction

A - is the area of the coil

from this it is clear that the defection of the coil is directly proportional to the current passing through the coil. The scale is calibrated and it can give directly the magnitude of current

Shunt Sometimes the galvanometer is connected in a circuit in which large current is flowing. If the whole current is allowed to pass through the galvanometer, it will spoil the coil. To avoid this, a' low resistance is connected in parallel with the galvanometer so as to bypass a major part of the total current through this resistance. As a result, only a very small fraction of total current passes through the galvanometer. This parallel low resistance is called a shunt

ELECTROSTATIC INDUCTION

ELECTROSTATIC INDUCTION

Electrostatic Induction - Electric induction is the phenomenon in which positive and negative charges are accumulated or separated in a substance, when a charged body is brought nearer to it. For example when a negatively charged body A is brought nearer to a conductor BC the near end B acquires positive charge and the far end C acquires negative charge (Fig. 2.4). That means the negative charges in A repelled the electrons in BC to the far end. The amount of  charge in A and in BC are equal in magnitude. If A is positively charged, BC will have the opposite effect. This method of charging a body is known as electrostatic induction and is used in electrostatic machines and capacitors. Electrophorus, lighting arrester and vandegraaff generator are few examples for electrostatic machines.This is known as electrostatic induction

TRANSFORMER LOSSES

In practice the output power is always lesser then the input power and hence the efficiency of the transformer is always less than 100 percent. this implies that some amount of energy is lost in the form of heat. The energy loss can be considered as copper losses, eddy current losses, hysteresis losses and flux leakage

Copper losses – when a current I flow through resistance R, an amount of power equal to i² R t watts is converted into heat. this arise in both copper coils and iron core. The copper coils possess resistance. When  current flow through this coil, electrical energy equal to i² R t is converted into heat. To reduce the loss, the current cannot be reduced because the normal operation of the transformer of the transformer will be affected. Instead the resistance of the coil must be minimized by using the wire of low resistivity wire. Therefore, thicker wire should be used as transformer coil. the optimum thickness will be decide by comparing the cost, space and saving of power. Copper is the best coil material available today and therefore is commonly used.

Eddy current losses – the iron core consisting of concentric layers of iron each acting as circuited single turn coil. hence, emf will be induced in the core. This emf will be produce currents called eddy currents. the eddy currents will give rise to i² R t losses. These eddy currents can be eliminated by making the iron core in the form of thin sheet of metal, and each sheet is insulted from its neighbor by thin layer of paper .this type of core is known as laminated core .the core is usually made up of stelloy ,an alloy of steel.

Hysteresis losses – the transformer core is the magnetic material. The core is magnetized twice in each cycle of the alternating voltage. when the direction of ac changes, the magnetization also gets reversed. During this reversal some energy is lost due to the molecular friction and the energy appears as heat. The loss of energy by molecular friction is called hysteresis loss. This can be reduced in practice by choosing a suitable magnetic material such as mumetal which has low hysteresis loss. mumetal is a ferromagnetic alloy containing 78 percent nickel,17% percent iron and 5% copper. its has high permeability.

Flux leakage  -  all the flux linked with the primary is not linked with the secondary due to leakage. this result in the loss of the energy. This can be minimized by using a shell type of core

FLUORESCENCE

FLUORESCENCE

When electromagnetic radiation falls on the certain crystalline substance, visible or ultraviolet light is emitted from the crystal. This phenomenon is called fluorescence. Fluorescent is a form of light emission within  10 ^-8 of x-ray exposure. If the emission of light delayed beyond   10 ^-8 is called phosphorescence .actually the crystal absorbs the radiation of shorter wavelength which produces excitation in the crystal.this is called FLUORESCENCE

CASSETTE

cassette

The caste is the rigid holder that contains the screens and film. the front surface, the side facing the tube , should be made of material with low atomic number, such ads plastic or cardboard or aluminum and should be thin yet sturdy. Attached to the inside of front cover is the front screen and attached to the back cover is the back screen. The radiographic film is loaded between these two screens. These days most cassettes are loaded with identical screen for front and back. Between each screen and the cassette cover will be compression device such as felt or rubber that maintains close screen film contact when the cassette is closed and latched. The back cover is usually made up of heavy metal such as lead to minimize backscatter. The x-rays pass through the film screen combination to back cover will be absorbed photoelectrically more readily in high z material then in low z material.this called cassette.

HOW X-RAY PRODUCTION TAKES PLACE?

SOURCE FOR XRAY PRODUCTION

The production of x-ray needs the following requirements

·         Electron source cathode

·         Target to stop the electron(anode)

·         High voltage power supply to accelerate electrons

·         Vacuum

·         And tube insert and housing.

·         Electrons can be produced by ionization in gas or by thermionic emission

·         The electron source act as cathode and target act as anode. The high voltage is applied between anode and cathode. this voltage  accelerate the electrons to a high velocity as a result the electron will possess a high kinetic energy, when the electrons are stopped by the target ,the electron kinetic energy is converted into x-rays energy thus x-rays are produced

·         A high vacuum is maintained between the anode and cathode. this is necessary

·         To avoid collision between the electrons and gas molecules and

·         To avoid oxidation of tungsten filament in the cathode they require vacuum is less than 10^-5mmhg

·         The housing absorbs the x-ray emerging in undesired direction.

·         Maintains the require vacuum

·         And act  as an electrical insulator

·         And also contain cooling system which remove the heat from the target the equipment having all above requirements is called an x-ray tube

CAPACITANCE OR CAPACITOR

CAPACITANCE OR CAPACITOR

CAPACITANCE

the property of a conductor to store electric charge is know as capacitance.it is defend as the ratio between the charge and its potential.if the q is the charge in a conductor of potential v then the capacitance c is given by:- c = q/v

the unit of capacitance is farad(F).one farad is the capacitance of a capacitor which require one coulomb electric charge to raise its potential by one volt, in practice, micro farad and pico farad is useds

1farad= 1 columb/volt

CAPACITOR

a capacitor is a device which increase the capacitance of the conductor.it usually consist of two conductors , one charged and other is earth connected.the space between the plate is filled with some insulating material called dielectric. 

the capacitance of capacitor depends on several factors such as

• area of over lap between the plates
• distance between the plates
• nature of dielectric medium

capacitor uses:

• used to store electric charge
• used to measure potential difference and small currents
• it is useful in reducing voltage fluctuation,generating oscillations,for providing time delay in various electric circuits
• with use of capacitor require electric field can be obtained

THERMIONIC EMISSION

THERMIONIC EMISSION

When a metal is heated, its molecules (Atom) take thermal energy. Some of its electrons take up so much energy that it can go away from the surface of the metal. These are called Thermions. Without this energy, electrons can only move inside the metal and cannot come out.

Thus, the arrival of electrons with thermal energy in this way is called Thermionic Emission. In this way, the accumulation of electron flakes on the metal surface in the form of electron clouds is called Edison Effect.

These negatively charged electrons come out of the metal to form a space charge. This space charge no longer allows other electrons to flow out of the metal surface until they are given enough thermal energy to On resistance to space charge. By this space charge, preventing other electrons from coming out of the metal surface is called Space Charge Effect.
When the electrons come out of the filament, the filament absorbs positive charge, so that the filament attracts some electrons again from this space charge. In this way, when the filament is heated to this Emission Temperature, a equilibrium is formed in which the number of electrons emitted from the filament is the same as the number of electrons absorbed by the filament. Due to which the number of electrons in the space charge is fixed, the number of  which depends on the temperature of the filament. Thus a very large number of electrons can be obtained by accelerating a large number of electrons from the cathode to the anode. These electrons can be obtained. Beams always flow in the same direction (from cathode to anode) in the x-ray tube. In this electron beam, the repulsion force acts due to the same charge between the electrons of the electrons, due to which the electron beam spreads in its width, as a result it collides on a very large part of the x-ray tube. The foxing cups are used to prevent this dispersion of the electron beam and to limit the collision area of ​​the electron beam at the anode. This forcing cup is given a minus potential equal to the filament| It is designed in such a way that it converts the electron beam to the desired shape and size on the target. This forcing cup is usually made of nickel. The x-ray tube usually has one filament and the modern x-ray tube has two filaments. Dual filament X-ray tubes have two filaments arranged in a Side by Side or One Above Other arrangement. They have one filament larger than the other. They are used to generate only one filament electron beam at a time. Large filament is for long exposure. You can see the filament by removing the filter from the beam exit port of the x-ray tube as the filter appears red after heating. The modern x-ray machine also has more than two (3) filaments and the filaments in the stereoscopic angiographic tube are in a different arrangement, in which two filaments are located at a distance of 4 cm, in which a stereoscopic film foot is removed from the exposure.

RECTIFIER,HALF WAVE RECTIFIER AND FULL WAVE RECTIFIER

RECTIFIER,HALF WAVE RECTIFIER AND FULL WAVE RECTIFIER

RECTIFIER

An electronic device that used to convert Alternative Currents to direct current . Rectifiers are used in many circuits. Wherever we have to change AC to DC voltage, we have to use rectifier. This rectifier uses diode to convert such supply to DC or you can say that diode is used to make rectifier.  And there are mainly 2 types of rectifiers:-

·         Half wave rectifier

·         Full wave rectifier

Half Wave Rectifier -This rectifier is able to rectify only half the cycle of AC supply. Step down transformers are used in this rectifier Which are connected to the diode. The circuit diagram of this Half Wave Rectifier is given below.
First the main supply voltage is given to the transformer from there, if the step down is used by the transformer, it will reduce the voltage and send it to the diode. In the photo given here, we have shown step down transformer because in general it is the transformer that reduces the voltage for the rectifier. Whether it's a simple battery charger or  if you want to run a device with it. This rectifier has only one diode which is connected in series above the secondary winding of the transformer. And this diode prevents the Reverse Bias Current. That is why it only allows Half Wave to pass , hence this rectifier is called Half Wave Rectifier.

Working Of  Half Wave Rectifier - When voltage is given by the transformer on the rectifier, it is both positive and negative cycle but it only allows the Positive Half Cycles to go forward due to the rectifier diode. And stops the negative Half  Cycles. Because the diode Half positive cycle coming in the rectifier will be in the Forward Bias position and will pass that cycle. But as soon as the Half Negative Cycle arrives on the diode, it will enter the Reverse Bias position and will not pass that Half Negative Cycle.

Full wave rectifier - Two diodes are used in this circuit. The anodes of both diodes are connected to both ends of the secondary winding of a middle end transformer. Each diode maintains a load current by working one diode. Because full-wave DC is used in this rectifier, this circuit is called full-wave rectifier.

In this, both diodes are connected to the secondary winding of the load resistor and the transformer in such a way that half of the secondary winding is connected in the circuit of each diode and the circuits of both diodes are completed by the common load resistor RL.

 In the first  positive half cycle, the anode of diode D1. Will be positive and the electrons flow in the circuit from the cathode of D1 to the upper part of the anode secondary winding And the load resistor will be from RL. At this time diode D2 will be inactive In negative half cycle, diode D1 will become inoperative but due to the bottom end of secondary winding being positive, the electron flow will start from diode D2. The electron current in the circuit will be at the bottom of the anode secondary winding of the cathode of D2 and the load resistor RL. It should be noted that the direction of current flow is opposite to that of electron flow.
Thus, due to alternating operation of both diodes, the output is obtained for each semi-cycle and the current flow in the output is constant. Due to two times the ripple frequency of this rectifier circuit, the output current remains constant, the efficiency of this circuit is high and the DC in the core works due to magnetic current saturation due to the current in opposite directions in the two sections of the secondary winding of the transformer.

TRANSFORMER AND PARTS OF TRANSFORMER AND ITS WORKING

TRANSFORMER

A trans former is an electrical device which can convert electrical energy from one coil to another coil.the transformer is working on the principle of mutual induction .the transformer basically consist of two coils called primary and secondary coil these coils are wound on iron core.the alternating voltage,which is to be transferred is applied in the primary coil.this produce changing magnetic flux in the iron core which produce an alternative e.m.f in the secondary coil.the induced e.m.f in the coil are directly proportional to the respective no of turn in the coil.

Transformer was invented by Michael Faraday and Joseph Henry showed it to the world in 1831. Transformers in Hindi are called transformers. It’s simple use is as the transformer reduces the voltage such that a device operates on a 12 volt direct current, then the transformer reduces the alternating current coming in our house to 220 volt to 12 volt. This is 12 volt of alternating current Let's use rectifier to convert it to dc It is called a stationary device because it does not have any moving part or no moving part. The transformer works on the principle of reciprocal induction and reciprocal induction is not possible in direct current, so the transformer cannot be used in direct current.

Working of transformer -
The transformer has three parts consisting of a metallic core and two winding's which are made of very good conductive metal such as copper, winding plays the main role in the transformer. When the alternating current is flowing in the primary coil in the transformer, the magnetic field is created in the core whose value varies, the secondary coil is wrapped in the same core, it also changes the magnetic flux passing through the secondary coil, which causes electrical changes The change in magnetic flux from the principle of magnetic induction results in a secondary coil Flow starts flowing.

1)The alternating current produced in the second coil is proportional to the magnitude flux.

2)The direction of current generated can be determined by the flue rule of the right hand.

3)The recurring current in the second coil will be similar to the current flowing in the first coil.

This reaction produces electromagnetic induction from the secondary coil in the secondary coil with an alternate voltage of the same frequency as the frequency we had applied to the primary winding.

Transformer parts

Core of transformer - The core in the transformer is in the middle. It is made of laminated steel plates which are of strip type. There is a minimum Air Gap between all these leaves. It reduces the currents. Winding is wrapped around the core
.

Winding - Winding The wires that are rotated are called winding. Single phase transformers have two winding, one is primary winding and the other is secondary winding and if the transformer is three phase then it has three primary winding and three secondary winding all from the insulated layer. Stays in contact with each other

Transformer Conservator  tank  - the Conservator tanks are used in high power transformers, they are small. You must have seen that this Conservator tank is upside down in the transformer, in which the hot transformer oil cools and goes back.

Breather in transformer - It is connected to the Conservator tank, it is used for breathing of the transformer. The air inside and outside the transformer goes through the breather.

Valves of transformers - Oil is poured into the transformer by valves and exhaled from the valve.
   

Steel tank of transformer - The core of the steel tank transformer is core, winding etc.. Everything is in it. This transformer is filled with oil, it is cylindrical or cubic. It depends on the inner vault of the transformer.

Cooling Tube - Cooling tube in which transformer oil flows, it acts like a radiator and cools the oil.

Thermometer - The thermometer measures the temperature of the transformer oil and winding in the transformer and the alarm rings when too large.

ELECTRIC CURRENT

ELECTRIC CURRENT

The rate or amount of charge flow is called electric current i.e. electric current in other words we can say that The continuous flow of electrons in a circuit or electric circuit is called electric current. The

electric current is denoted by I. According to  electron theory the current from positive end to negative end. Flows Benjamin Franklin first used the term Suppose in a circuit that Q charge is circulated for a period of time in a circuit, then electric current will be I. Then its formula is

Current I =Q/t

Current = charge/time

That is, the rate of charge flow is called electric current.

The S.I Unit of electric current is a unit ampere representing the ampere as A and the current from I is the measuring instrument A-meter with two ends that can measure the current. The current multi-meter is the best option for measurement.

COULOMB INVERSE SQUARE LAW AND OHM;S LOW

Coulomb inverse square law

The force between two charges is directly proportional to the multiplication of both charges, and is inversely proportional to the square of the distance between those two charges. Now that force can be attractive or repulsive.

Coulomb stated that this is an experimental rule And the force is central and protective force. The force follows Newton's third law of motion.

Suppose two point charges are q1 and q2 and then the distance between these two charges is r. Force of charge between two point charges first charge × second charge

F∝q1×q2

F∝1/r2

Then the combination of these two forms the formula of Coulomb’s law.

F∝q1×q2/r²

F=k×q1×q2/r²

Where k is a constant whose value is 1 / 4πε0

ohm's law

If no change is made in the physical conditions of the conductor i.e. length, temperature, pressure, etc., then the potential difference generated at the ends of the conductor is proportional to the current flowing in it.

If the applied voltage assumes V and the current flowing I assume then the relationship between Ohm's law-

V ∝ I

V=RI

Here R is a constant which is called Resistance.

                                                                  R=V/I

Increasing the value of voltage or differential  v also increases the value of current

AP KNEE , LATERAL KNEE AND SKYLINE(AXIAL PATELLA)

AP KNEE AND LATERAL KNEE

Ap knee – This position done to visualize Fractures, dislocations of the knee

Collimation- to include distal third of femur and proximal third of tibia and lateral and medial skin edge

Centering point – apex of patella

FFD- 100 cm  

Central ray – 5° -1°0 cranial angulation

Cassette orientation - portrait  or depend on patient

Protection – gonads shielding is advisable

Position of patient – the patient supine or seated on the table with leg staright and cassette placed under knee

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LATERAL KNEE

Lateral knee – This position done to visualize Fractures, dislocations of the knee

Collimation- to include distal third of femur and proximal third of tibia and anterior and posterior skin edge

Centering point – medial femoral condyle

FFD- 100 cm  

Central ray – 5° -10° cranial angulation

Cassette orientation -  portrait  or depend on patient

Protection – gonads shielding is advisable

Position of patient – the patient supine or seated on the table with leg straight and cassette placed under knee

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SKYLINE (AXIAL PATELLA) KNEE

Skyline(axial patella)  – This position done to visualize Fractures, dislocations of the knee

Collimation- to include mediiam side, lateral side and anterior skin edge and fibula head. Collimation needs to be as tight as possible as the primary beam is directed towards the patient’s body.

Centering point – apex of patella

FFD- 100cm  

Central ray – angled so that is is perpendicular to the patella femoral joint space

Cassette orientation - landscape or depend on patient

Protection – gonads shielding is advisable

Position of patient – the patient seated on the table with knee flexed 45°  and patient to hold the cassette perpendicular to table resting on the anterior aspect of the femur

TIBIA/FIBULA AP OR LATERAL

TIBIA FIBULA AP/LATERAL

TIBIA FIBULA AP

Ap tibia/fibula  – This position done to visualize Fractures, dislocations of the tibia and fibula

Collimation- to include both knee and ankle within field

Centering point – midshaft of tibia

FFD- 100cm  -150 cm depending on length of leg. Remember to adjust exposure according if you increase the FFD

Central ray – perpendicular to cassette

Cassette orientation - portrait  or depend on patient

Protection – gonads shielding is advisable

Position of patient – the patient supine or seated on the table with leg staright

Flex foot as far past 90 and cassette placed under leg

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TIBIA FIBULA LATERAL

Lateral  tibia/fibula  – This position done to visualize Fractures, dislocations of the tibia and fibula

Collimation- to include both knee and ankle within field

Centering point – mid shaft of tibia

FFD- 100 cm -150  cm depending on length of leg. Remember to adjust exposure according if you increase the FFD

Central ray – perpendicular to cassette

Cassette orientation - portrait  or depend on patient

Protection – gonads shielding is advisable

Position of patient – the patient to lay on side with lateral aspect of affected leg on  cassette and knee should be Flex at approx 45 or foot should be flexed at 90

CALCANEUS AXIAL AND LATERAL

AXIAL CALCANEUS 

Axial calcaneus  – This position done to visualize Fractures, dislocations of the tarsal bones and subtalar joint that make up the calcaneus. 

Collimation – lateral and posterior skin edge and to include baser of 5^th metatarsals bones.

Centering point – at the level of base of 5^th metatarsal in the midpoint of the foot

FFD- 100cm

Central ray – 30°- 50° cranial angulation, depending on tolerated foot flexion

Cassette orientation – landscape or depend on patient

Protection – gonads shielding is advisable

Position of patient – the patient supine or seated on the table with leg straight and toes pointed on the roof.

Flex foot as far past 90 as patients will tolerate. You may need to use a belt or something similar in order to achieve this. And cassette underneath

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LATERAL CALCANEUS 

Lateral calcaneus  – This position done to visualize Fractures, dislocations of the tarsal bones and subtalar joint that make up the calcaneus  

Collimation- posterior skin edge to base of the 5^th metatarsal and inferior skin edge to medial malleolus

Centering point – midpoint of the calcaneus

FFD- 100cm

Central ray – perpendicular to cassette

Cassette orientation – landscape or depend on patient

Protection – gonads shielding is advisable

Position of patient – the patient supine or seated on the table with leg  externally  rotated so that the lateral  side of the foot is resting on the cassette .

Flex foot as far past 90 and raise knee from the bed until planter surface of the foot is perpendicular to the cassette

DP FOOT,OBLIQUE,LATERAL

DP FOOT, OBLIQUE, LATERAL

DP FOOT –  This position done to visualize Fractures, dislocations of the phalanges, metatarsals and tarsal bones that make up the foot. 

Collimation – for foot to include entire foot and for toes include distal tip of toe and distal end of metatarsals bones.

Centering point – foot- mid foot

                             Toes – mtp (METATARSOPHALANGEAL)   joints 

        

FFD- 100cm

Central ray – 5° cranial angulation

Cassette orientation - portrait or depend on patient

Protection – gonads shielding is advisable

Position of patient – the patient supine or  seated on the table with knee bent and plantar aspect of foot placed on cassette.

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BLIQUE FOOT

BLIQUE FOOT –  This position done to visualize Fractures, dislocations of the phalanges, metatarsals and tarsal bones that make up the foot. 

Collimation – for foot to include entire foot and for toes include distal tip of toe and distal end of metatarsals bones.

Centering point – foot- mid foot

                             Toes – mtp (METATARSOPHALANGEAL)   joints  of affected toe

       

FFD- 100cm

Central ray – 5° cranial angulation

Cassette orientation - portrait or depend on patient

Protection – gonads shielding is advisable

Position of patient – the patient supine or seated on the table with knee bent and plantar aspect of foot placed on cassette and rotate internally 45°

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LATERAL FOOT

Lateral  FOOT –  This position done to visualize Fractures, dislocations of the phalanges, metatarsals and tarsal bones that make up the foot. 

Collimation – for foot to include entire foot and tibiotalar joint for toes include distal tip of toe and distal end of metatarsals bones. Separate toes using a tongue depressor or foam pad if required

Centering point – foot- mid foot

                             Toes – mtp (METATARSOPHALANGEAL)   joints  Of affected toe       

FFD- 100 cm

Central ray – perpendicular to cassette

Cassette orientation - portrait or depend on patient

Protection – gonads shielding is advisable

Position of patient – the patient supine or seated on the table with leg externally so that the lateral  aspect of foot is resting on the cassette

Foot should be flexed at 90°

Raise knee from bed until the planter surface of the foot is perpendicular to the cassette