Diagnostic X Ray

Diagnostic X-Ray

Diagnostic Equipment

History

• X-rays were discovered by Wilhelm Conrad Roentgen in 1895– Experiments on the

applications of High Voltages on Vacuum Tubes were being conducted in the late 1800’s.

History

• Roentgen was working with a certain vacuum tube through which a current under high voltage was being passed. – The tube was entirely

enclosed in black paper so as to exclude all the light emanating from it.

History

• Roentgen observed fluorescence of some barium platinocyanide crystals coating a piece of cardboard lying nearby. – This was a

phenomenon known to occur at the time.

History

• Roentgen upon seeing this thought that perhaps the fluorescence of the crystals was due to some type of ray that could pass through the black paper around the tube.

History

• Roentgen picked up the chemically coated cardboard, his fingers came between it and the tube, and he saw the bones of his hand.

History

• Roentgen realized that he had discovered the presence of a ray that would penetrate solid matter.

• Roentgen Noted that:

"If one holds hands between the discharge apparatus, one sees the darker shadows of the bones within the much fainter shadow picture of the hand itself."

History

• Later on Roentgen changed the chemically coated cardboard with photographic plate and had an x-ray picture of his wife’s, Bertha, hand taken.

History

• The existence of that sort of light ray that passed thru solid objects was not know at the time so Roentgen called it “X” rays.

Impact of X-rays

• Modern medical science has profited greatly as a result of this important discovery. – X-rays are utilized by the medical profession

to:• Diagnose illnesses• Study bone fractures• Locate foreign substances in the body

• Treat cancer / skin diseases.

Science of X-rays

• Before starting this section lets have a review of some concepts we need to better understand the science of x-rays.– Energy its conservation and transformation– Mass – Energy Relationship– Law of Conservation– Atomic Structure

Science of X-rays

• Energy – It is not a substance and does not occupy

space. – It is defined as the capacity to perform work /

move objects from one place to another.– Types of energy

• Potential – Stored Energy

• Kinetic – Energy in motion

Science of X-rays

• To do WORK we need to have ENERGY.

Science of X-rays

• Work in the slide shown before is the work done by Blue Catch Net.– Energy of the car is at first present in the

system in the form of PE– Energy of the car is transmitted from PE to KE

as the car moves forward.– Energy of the car begins to drop as it hits the

catch net and work done on the net increases.

Science of X-rays

– Forms of Energy• Light• Heat

• Sound

• Motion

• Chemical• Electrical

Science of X-rays

• We said earlier to do work requires energy such that in theory:

Work Done = Energy Spent

– Work is equal to the Force Exerted by or on an object and distance it travels.

Work = Force (distance)W(Joules) = F(Newtons) d(metres)

Science of X-rays

• Law of Conservation– Matter and energy can neither be created nor

destroyed, though they can be changed from one form to another.

– In all chemical and physical processes of everyday living, the mass of end products obtained is equal to the mass of starting materials used.

Science of X-rays

• Law of Conservation– Einstein gave an equation to quantify the law

of conservation:

E = mc2

E = Energy (ergs)m = mass (grams)c = constant speed of Light

Science of X-rays

The Law of Conservation tells us that:

• Matter may be changed into another form of matter.

• Energy may be changed into another form of energy.

• Matter may be changed into energy.

• Energy may be changed into matter.

Science of X-rays

• Atomic Structure– Throughout history a

lot of models for atoms have been proposed or improved.

– Today we usually see the model of an atom the way the Niels Bohr (1885-1962) proposed.

Science of X-rays

• Niels Bohr Model– Miniature Solar System– Divided into two parts

• Nucleus– Neutron

» Neutral– Proton

» Positively Charged• Electrons

» Negatively Charged

– The number of Protons equals the number of Electrons hence the atom is neutral.

Science of X-rays

• The balance of protons and electrons can be disrupted causing a phenomenon called ionization. – Negatively Ionized– Positively Ionized

Science of X-rays

• Atomic Model from Wave Theory– Research suggests that Bohr’s Model was

correct and incorrect.• Its components where correct but its orientation is

not a solar system.

• Wave mechanics gives us a picture of this newer view of an atom

Science of X-rays

• Wave Theory Atomic Model is best represented by an energy level diagram.– The atom absorbs

energy, the orbit of the electron increases because the atom is in an excited state. If it (atom) emits energy, the electron falls into a more stable orbit closer to the nucleus. The diagram can be constructed by representing various energy levels

Hydrogen Atom represented in an energy level diagram

Science of X-rays

• Nuclear Shells– Electrons occupy specific orbits around the

nucleus. But there is a natural system that regulates how many electrons can exist in an orbit.

– This system was called nuclear shells.

Science of X-rays

• Nuclear Shells• K = 2(12) = 2 e• L = 2(22) = 8 e

• N = 2(32) = 18 e

• N = 2(42) = 32 e

Science of X-rays

• The use of orbits and shells to describe electron position indicates the relationship of different electron-energy levels. – An atom will tend to react with other elements

more readily when its outer shell is not completely filled.

Science of X-rays

• Binding Energy of a shell– Pertains to the amount of energy required to

knock out one electron from its orbit.

• Potential Energy of a shell– Pertains to the amount of energy released by

the electron that is knocked out from its orbit.

Science of X-rays

• Binding Energy– A is the Greatest

since it has the least distance.

• Potential Energy– C is the greatest

since it has the largest distance to the floor when it drops.

A

B

C

Floor

Science of X-rays

• Binding Energy for tungsten shells are: – K--69.5 keV– L--12 keV– M-- 2 keV– N--0.8 keV

Science of X-rays

• Valence– Valence represents the capacity of an atom to

combine with other atoms to form molecules. – It is determined by the number of electrons in

the outer shell.

Science of X-rays

• Radioactivity– The spontaneous disintegration of radioactive

substances in which the atomic nuclei undergo partial breakdown and give off penetrating radiation at the same time

– It is a natural property of all existing elements with atomic numbers above 83.

Science of X-rays

Science of X-rays

• Radioactivity– A factor contributing to nuclear disintegration

in radio elements is the instability of their atomic nuclei.

– For these elements to reach a more stable or less energetic state, excess energy in the form of alpha, beta, or gamma radiation is released.

Science of X-rays

• Alpha Particle– Travels at speeds of 9,000 to 20,000 miles per second,

but it is slowed down rapidly in its passage through matter.

• Beta Particle– Has a smaller mass and travels at a much higher

speed than an alpha particle, almost as fast as light. • Gamma Particle

– It can be considered as bundles of pure energy (photons) generally expressed in keV or MeV.

– Gamma radiation wavelengths are extremely short, and the radiation is the most highly penetrating.

Science of X-rays

• X-radiation – Results from the conversion of either the

kinetic or potential energy of electrons into another form of energy.

– Produced by radiative interactions of electrons with matter and collisional interactions of electrons with matter.

Science of X-rays• Radiative Interaction

– When an electron (which is negatively charged) approaches the nucleus (which is positively charged), it may be deflected from its original direction by the attractive force of the nucleus.

– The change of direction causes deceleration of the electron or a loss of some of its kinetic energy.

– The energy lost by the electron is given off as an x- ray photon. This process is referred to as radioative interaction of an electron with matter.

Science of X-rays

• Radiative Interactions– The radiation produced by this

type of interaction is called bremsstrahlung (German for braking radiation), general radiation, or white radiation.

– The energy of the resultant photon depends upon:

(1) the original kinetic energy of the electron

(2) how close the electron comes to the nucleus

(3) the charge of the nucleus.

Science of X-rays

• Radiative Interaction– An electron, as well as being

decelerated near the nucleus, may occasionally collide with the nucleus.

• In this case, the electron loses all its energy in the collision and that energy is given off as a photon.

• The energy of the photon would be equal to that of the electron.

– If the electron shown possessed 100 keV of energy, the resultant photon would also have 100 keV of energy.

Science of X-rays

• Collisional Interactions– X-rays are also generated

when electrons interact with the tightly bound orbital electrons of a hard surface. This is called collisional interaction of an electron with matter and produces characteristic or line radiation.

Science of X-rays• Collisional Interaction

1. Electron enters the area near the atom2. Electron hits a electron say in the K-

shell3. Electron moves in another direction

K-shell electron also moves outside.4. Vacancy in the K-shell causes

electrons in higher shells (M,L or N) say L to move into the space left by the K-shell electron.

– This causes the electron to loose some of its binding energy. K(69.5 keV) – L(12 keV) = Photon (57.5 keV)

1. Vacancy in L shell causes electrons from M or N shells move into the spce left by the transition.

– This causes the electron to loose some of its binding energy. L(12 keV) – M(2 keV) = Photon (10 keV)

1 23

3

4

5

Science of X-rays

• Short wave lengths has higher energy, frequency and is more penetrating.

Science of X-rays

• X-rays are produced by using an X-ray Tube. The sequence is as follows:

1. Heat Filament and produce free electrons

2. Apply High Voltage to Cathode and Anode of the Tube this releases the electrons sends them shooting towards the Anode

3. Electrons hit the anode and thru interaction produces X-rays.

Science of X-rays

• Focusing Cup– Indentation on the Cathode

that focuses the free electrons on a particular spot.

• Actual Focal Spot– Area of the target bombarded

by the electrons

• Effective Focal Spot– It appears from directly

beneath the tube at right angles to the electron stream

– Determines the clarity of the picture made by the X-ray

Science of X-rays

• Line of Focus– X-rays should provide an

actual focal spot large enough to permit the necessary heatloading and an effective focal spot small enough to produce optimum detail

– The x-ray tube is designed so that the electrons bombard a rectangular area on the target surface.

Science of X-rays

• Anode Heel Effect– Because the anode is angled, the

intensity of the x-ray beam along the longitudinal axis of the tube varies. This variation in intensity results from absorption of some photons by the target itself.

– Consequently, the intensity of the x-ray beam is greater on the cathode side than on the anode side. This nonuniformity is known as anode heel effect.

X-ray System Components

• Generator

• Tube & Collimator

• Tube Stand

• Chest Stand

• Bucky Table

• Cassette

X-ray Machine Circuit

X-ray Machine Parts

• Major Operating Blocks

Line to Auto-TransformerX-ray Filament CurrentHigh Tension CircuitTimer or Control CircuitX-ray Tube

X-ray Machine Parts

Line to Auto transformer

Filament Circuit

Timer or Control Circuit

High Voltage Circuit

X-rayTube

X-ray Machine Parts


Line to Auto-TransformerThis section of the x-ray machine is

used to select the amount of Voltage that comes from the AC Outlet.

Controlled by a microprocessor and servo motor.

X-ray Machine Parts

• Major Operating BlocksHigh Tension Circuit– Provides the means of adjusting the potential

applied to the high-tension primary winding, thus varying the potential applied to the x-ray tube, a provision for closing and opening the PHT (T1 and T2 for the example circuit) circuit, and some means of predicting the potential to be produced across the x-ray tube.

X-ray Machine Parts


High Tension CircuitThe major and minor kilovoltage selectors are

rotary tap switches. Major kVp-selector usually adjusts in increments of 10

kVpMinor kVp-selector adjusts in increments of 1-2 kVp.

X-ray Machine Parts


RectificationRectification is essential, since x-ray tubes require

direct current for their operation. A Gretz or Bridge Rectifier provides DC voltage for the

production of X-rays

X-ray Machine Parts


X-ray FilamentUsed in medical radiography, must be heated until

incandescent. The hotter the filament, the larger the number of

electrons liberated. A relatively high current is required to produce the desired temperature.

X-ray Machine Parts


X-ray Filament Current• This section is used to set the x-ray tube current

that permits variations in the x-ray tube filament temperature.

• Adjustment is done thru a control knob called the filament control or choke coil

X-ray Machine Parts

• Major Operating BlocksX-ray Filament Current

• Filament limiter is an adjustable (strap-type) resistor, which is not available to the operator.

– Adjusting this resistor can limit the maximum tube current. This is needed to keep the x-ray tube within safe operating limits.

• Filament meter– X-ray tube filament temperature determines the x-ray tube

current. This temperature is a function of the voltage and current of the primary of the x-ray tube filament circuit.

– Either a voltmeter or an ammeter on the primary circuit can be used to predict, with accuracy, the x-ray tube current before high voltage is applied to the tube. Normally, only one of these meters would be needed.

– The use of a fixed resistance selector method eliminates the need for a filament ammeter.

X-ray Machine Parts• Major Operating Blocks

Timer or Control Circuit Hand or mechanical timer

Spring Wound Motor minimum accuracy of 1/8 of a second. Synchronous timer

Consists of a small synchronous motor, the revolutions of which are counted and used as the timing factor. Can time at the minimum 1/20 of a second

Impulse timer Can operate at time intervals from as short as 1/120 second to as long as about 1/5

second. Electronic timers

Uses electronic circuitry to count the alternating current pulsations, and they cover the entire range of times from milliseconds to several seconds more accurately and reliable than impulse timers.

Photoelectric Timer Uses of a photocell or photoelectric eye. A small fluorescent screen with a photocell is placed behind the cassette (a film

holder, having a back through which x-rays may penetrate). When a predetermined quantity of radiation has struck the fluorescent screen,

causing it to give off light that the phototube measures, a mechanism is activated which automatically stops the exposure at the correct time .

X-ray Machine Parts

• Major Operating BlocksX-ray Tube

Provides the facility for producing x-rays by addressing the following:

– A source of electrons (Filament)

– A means of accelerating the electrons. (Cathode)

– A hard, dense target in which the kinetic energy of the electrons is converted into x-rays. (Tungsten Anode)

X-ray Machine Parts


X-ray TubeRotating Anode

Provides better heat dissipation

By continuous spinning of the target, the focal spot presented to the electron stream is always changing. This spreads the electrons and, consequently, the heat over a larger area.

X-ray Machine Parts


Grid Controlled Tube Contactors arch due to

increasing energy applied to contact points.

To prevent this problem an x-ray exposure is normally synchronized to the line voltage so that it begins and ends when the sine wave is at zero value.

X-ray Machine Parts


Grid Controlled Tube Two conventional elements, the

cathode and anode, the grid-controlled tube has a third element or grid.

The grid, is a focusing cup, is electrically isolated from the filament. The grid is negative with

respect to the filament. A "negative electrostatic field” is set up which acts as a gate to stop electron flow by repelling the negatively charged electrons.

Mobile X-ray Machine• Mobile X-ray Machines work

thru the use of a battery bank (240 Vdc) and capacitors.– Capacitor(s) is/are charged at

low current and then discharged very quickly through the X-ray tube.

– Capacitor(s) is charged by high voltage (HV) transformer and single-phase rectifiers.

– A grid controlled X-ray tube is used so that tube current can be stopped by applying a negative voltage between cathode and grid.

– Timer stops exposure after preset time and controls the mAs.

Mobile X-ray Machine

• Advantages– Can be operated from a

normal mains power 10 Amp socket without drawing excess current.

– Cheap to purchase, very reliable, easily moved around hospital.

– Very good for chest and extremities (hands, feet, arms & legs).

• Disadvantages– Must not be used for abdomen

– they give excessive skin dose & poor images.

– The kVp drops rapidly as exposure proceeds, 1 µF drops 1 kV per mAs.

– PA chest requires 3 mAs at 120 kVp, i.e., 3 kV drop.

– AP abdomen requires 30 mAs at 70 kVp, i.e., 30 kV drop.

– Film exposure drops very rapidly as kVp drops.

– Increasing the mAs beyond 5 mAs gives virtually no more exposure to the film.

Safety Principles

• Risks when working on X-ray Machines– High Voltage Outputs

• Results in Electrocution (Macro shock) this will kill you if not respected

– Open and do resistance tests and removal of plugs only when the machine is unplugged or its battery has been removed.

– Never open up the case while the unit is operational unless you have to measure something.

» Be sure where you attach your measuring devices and that they can withstand the current and voltage outputs of those terminals.

– Ionizing Radiation • Can damage cells since x-rays deliver energy that

can affect cell structures such as chromosomes and cell membranes.

– Minimize Exposure Time– Maximize distance from exposure source.– Use lead aprons and shielding from radiation

sources.

Staff Checks Before Use

• Unit turns on

• All Lights and indicators correctly turn on.

• Moving parts can be adjusted without any problem and lock in place when needed.

• Warm up procedure is conducted correctly before use.

Common Problems

• No X-ray Beam– Check the following:

• Unit turned on?

• Fuses Blown?

• Interlocks not set?• Is your tube correct?

Common Problems

• No Light Beam– Unit turned on?

– Bulb faulty or incorrect?– Bulb holder faulty?

Common Problems

• Misalignment of Bucky with X-ray Beam– Check Bucky Movement and locks

– Take an exposure test with a coin aligned with Light Beam cross hairs and bucky.

• Adjust Bucky using this and expose again.

Inspection

• This section will cover the following components:– Generator and Control– Table– Tube– Bucky Units– Cassette Changers

• Standard Inspection Form should be used as a guide.– Include another list of the manufacturer

recommended checks that should be done. You can get this from the Service Manual.

Inspection• Generator and Control

– Examine fuses normally accessible to the user and ensure they are physically secure with no apparent signs of damage or apparent heat stress.

– Carry out a visual inspection of visible wiring, including high-tension (HT) cables, and stator cables and any visible connectors. Report any signs of discolouration, loose or detached cable supports and fixings.

– Examine cables to ensure there are none that can inadvertently be tripped over or walked on. Check the fixing security of all covers and guards and that they are in position.

– Examine the legibility of all scales and controls.– Check the operation of all illuminated controls and where possible

check the satisfactory operation of warning indicators.– Check the fixing security of all knobs, switches, push buttons, etc.– Check that interlock settings are functioning.

Inspection• Table

– The fixing security of all attachments– Accessible wire ropes must not present a hazard to clothing, should be clean and show

no obvious signs of stranding– All safety guards must be in position and securely fixed– Check that tilting safety stops and interlocks and the longitudinal and lateral roll of the

table top are operational.– Identify the serial changer, limit switches, interlocks and lateral and longitudinal stops

and check that they are operational.– Ensure that the compression device manual release and pressure cutout is operational.– Examine the Bucky tray to ensure the proper functioning of the cassette clamp and tray

catch and that the grid has unimpeded motion.– Check that tomographic interlocks, including movement, are operational.– Check stepping table tops for proper function of parking interlock, pallet stability and film

overlap.– Tube support system – Check all fixings for any sign of insecurity, e.g., loose nuts and bolts, excessive play on

slides at right angles to normal direction of travel, unexplained noises in movements.– Check all movement-locking devices for adequate operation with power on and off,

including longitudinal and lateral rotation and vertical movements.

Inspection• X-ray Tube

– Check HT cable runs for all positions to ensure freedom of movement, avoidance of strain and sharp bends and that there are no obvious signs of chafing.

– Examine visible suspension cables for signs of strands.– Check that demounting of the intensifier prevents exposure.– Examine light-beam diaphragm for stability and security of fixing.– Check that the light source “on-time” is satisfactory for normal use.– Examine the X-ray tube housing for adequate counterbalance (power

on and off) and freedom of movement with clamps released.– Note the X-ray exposure counter reading and ensure it is operational.

Listen to the tube rotation; evaluate bearing noise and anode braking.– Check that added filtration as labelled is present and secure.– Check that tomographic movements operate smoothly, the security of

attachment, and that overrun brakes are operational.

Inspection

• Bucky Unit– Check satisfactory operation of all movements.– Examine the suspension for stability (if free

standing) and integrity of electrical connection.

– Examine the cassette ledge and safety stop in the Bucky tray for free movements.

– Examine free operation of grid.

– Check fixings and satisfactory storage of accessories, e.g., headlamp, compression band cassette attachment.

Inspection

• Cassette Changers– Check that a series tube-rating chart is available and whether

maximum exposure times are stated.– Check that mains power supply plugs and sockets are

securely fixed and the insulation is in good condition.– Check whether the equipment is failing-load inhibited.– Check whether film numbering and patient identification is

satisfactory.– Check whether film movement during exposure can be

detected.– Check the security of the floor location plates.– Check whether table tilt is inhibited.– Check that satisfactory interconnection with the injector is

made.– Check that live and moving parts are inaccessible.

Inspection

• Other Items– All systems should be visually assessed for integrity

of cabling, connectors, switches and audible and visual “beam on” indicators.

– An examination of interlocks, electromechanical breaks and physical gantry stops should be performed.

– If the system has collision sensors these should be checked.

– All dials, switches and indicators on the control console should be performance tested.

– On radiographic units the light output from the light beam diaphragm should be checked.

Verification / Recalibration

• This section covers:– Materials for Verification / Recalibration

– X-ray Tube Overload Calibration– X-ray Tube Stand– X-ray Tube– Collimator – Bucky Table and Vertical Bucky Table


• Materials– Basic tool kit.– X-ray alignment template

– 24/30 cm cassette.

– Aerosol spray lubricant.

– Cleaning solvent.– Cloth, for cleaning.– Aluminum Top with Notch– Aluminum Step Wedge

– Two Pieces of Lead Rubber


• X-ray Tube Overload Calibration– Before removing any covers, ensure the generator

is switched off, and the room power-isolation switch is also turned off.

– Check all knobs and switches. Where knobs have a pointer attached, check that the pointer aligns correctly at all positions of the indicated scale.

• Tip. Check the pointer at full clockwise and counter clockwise positions of the knob. Look for possible loose knobs, or for push button switches that might tend to stick.

– If controls have had extra labels attached, are these labels still required? If so, are they in good condition?


• X-ray Tube Overload Calibration– Older X-ray controls often have analogue meters

instead of digital displays.1. With power switched off, the meter needle should be

pointing at the ‘zero’ calibration mark.

2. Most meters have a small adjustment screw for zero calibration. If adjusting, first tap gently in case the meter tends to ‘stick’.

Caution. Contact the service provider before adjusting. in some cases, the meter may be deliberately adjusted ‘off zero’, as an incorrect method of calibration.


• X-ray Tube Overload Calibration– Check all indicator lamps. If necessary, operate

different selection techniques to ensure all indicators operate correctly.

• Pay attention to the following. (Depending on make or model, some of these indicators may not be available).

– Small focus / broad focus selection indication.– mA selection– X-ray tube number, or position.

– X-ray tube overload protection. » Select high pre exposure factors» Check operation of the overload light

– Automatic Exposure Control (AEC), or Phototimer.– Illumination of kV, mA, and time selection


• X-ray Tube Overload Calibration– Maximum radiographic kV

1. Select a short exposure time, and a low mA station. Increase kV setting till the exposure prevention, or inhibit, light operates.

2. The maximum available kV should not exceed the specified kV for the particular X-ray tube.

3. In some cases, the available kV limit may be 10% less than the possible maximum. Forexample, a 150kVp tube may be limited to 140kVp.

» This is a safety precaution, as 150kV is the maximum limit only when the tube is in excellent condition.

Verification / Recalibration• X-ray Tube Overload Calibration

– Minimum radiographic kV. Often be set at 40kV.1. Select a low mA station and a short exposure time. Adjust kV towards the

minimum available value. An exposure inhibit should occur if kV is too low.2. Repeat this test for systems that have a removable filter in the collimator. In

this case, with the filter removed, an exposure inhibit should occur as kV is increased. (Depending on the system, this may be above 60kV.)

Note. Although the collimator will have the required minimum filtration for full operation, an additional filter, typically 0.5mm, may be inserted. This is an option, and does not require an interlock.

3. iv. On older generators, especially those with ‘stud’,or switch selection, and pre-reading kV meters, it may be possible to set kV below the safety requirement. Where this can occur, provide a warning notice, and contact the service provider in case an upgrade is available.


• X-ray Tube Overload Calibration– Minimum kV for filament over-heat protection.

• Check your machine chart for settings that should be avoided.1. Select the maximum available mA station and a short exposure time.

Reduce kV towards the minimum kV available. Either the kV will not be permitted to extend below the minimum specified value, or else should cause an exposure inhibit to operate.» As an example, the minimum kV with 500mA selected may be

55kV, while if 400mA is selected, the minimum kV might extend down to 45kV.

1. Repeat for both focal spots.

» Note. This protection may not be available on older X-ray controls. If a combination of high mA and low kV is possible, provide a warning notice. In some cases, an upgrade may be available from your service provider. In other cases, a re-allocation of available mA stations may be available.


• X-ray Tube Overload Calibration– Anode maximum heat load. This is the

maximum instantaneous heat input to the anode.

• Use only 70 to 80% of the actual setting when the tube has been used, since charts assume that x-ray tube has a cold anode.

Verification / Recalibration• X-ray Tube Overload Calibration

– Anode Maximum Heat Load1. Select the appropriate anode-rating chart for the X-ray tube in use. The anode speed is normally

controlled by the power frequency.2. Take care to select between 50 or 60 hz for lowspeed operation, or between 150 or 180 hz for high-

speed operation.3. In addition to anode speed, select either single or three phase operation, depending on the type of

generator.4. If you have a high frequency generator, select the three-phase chart. This will still apply if the

generator is supplied by single-phase mains5. power.

Note. The rating charts provide a family of curves. It is not required to use the same mA or kV for testing. For example, 0.1sec’, 125kV & 360mA is the same as 90 kV & 500mA.

1. On the rating charts, select suitable time periods. (For example. 0.02, 0.1, 0.3, 1.0, 5.0 seconds). At these time selections, determine a

2. suitable mA station, and the maximum kV that can be used with that mA selection. Adjust the kV towards this maximum value. The exposure

3. inhibit should occur before this value is reached. Repeat this test for each of the preselected time settings.

4. Repeat this test for each mA station; together with both fine and broad focus spot selection.5. Some X-ray controls may have provision for both high and low speed operation. In these cases, the

maximum load available for low speed operation, should not exceed 85~90% of the value indicated in the low speed chart.


• X-ray Tube Overload – mA calibration

• Things to keep in mind during this test:– mAs meters may be of two types. Type one is ‘ballistic’. With

this version, watch for the maximum reading on exposure, before the needle returns to zero.

– The other version is a true integrating mAs meter. This type will hold the reading for a period of time, often while the preparation button is kept pressed at the end of exposure. With this type of meter, ignore the peak needle deflection, and only record the steady reading.

– mAs meters may be dual function. In some controls, the meter will first indicate the % of anode load, and on preparation change over to the mAs function. Another type first indicates the preselected mAs, and on exposure indicates the actual mAs. Actual mAs remains displayed until preparation is released.

Verification / Recalibration• X-ray Overload Protection

– mAS Calibration1. When choosing an exposure time, avoid uneven times like 0.01, 0.03, etc.

This avoids timer problems that can exist on older units. Select an exposure time of 0.1 second for easy calculation.

2. Test mAs output using two kV positions.Values suggested are 60 kV and 90kV.Repeat this test for all mA stations and focal spots.

3. The test mAs output should be within 10% for older systems, and in modern equipment within 5%. Variations of mAs between adjacent mA stations should be less than 5%, including older designs.

4. When preparation is complete, allow another half to one second before exposing. This is toeliminate possible errors due to incorrect pre-heating of the filament.

5. To check for a possible filament pre-heating problem, select 60kV, and the largest mA station. Make an exposure immediately preparation is completed, and record the mAs output. Now make another exposure, but this time wait for about one second after preparation is completed, then make an exposure.

– If the difference between the two tests is more than 5%, contact the service provider for advice. The generator should have the filament pre-heating adjusted, or else a small increase in preparation time.


• X-ray Overload Protection– mAs Calibration using mA meter only

1. Select a low kV, between 60 and 70kV. 2. Make an assessment of tube loading with the selected mA station

by selecting an exposure time of two seconds.3. Assuming a two second time would permit an exposure; now select

a time of 0.8–1.0 second. This time allows the mA meter to reach a4. steady reading, during the exposure.5. When preparation is complete, allow another half to one second

before exposing. This is to eliminate possible errors due to incorrect pre-heating of the filament.

6. On exposing,watch the mA meter needle arrive at the expected value. Record the steady reading. (Ignore any bounce or overshoot.)

7. MA should be within 10% of the required value.


• X-ray Overload Protection– mAs Calibration using mA meter only continued

8. Repeat this test on both focal spots. Test only the mA stations that are well within the anode load safety limit, at the exposure times of 0.8–1.0 second.

9. Between test exposures, allow at least three to five minutes for anode cooling.

10. To check for a possible pre-heating problem, select 60 kV, and the largest mA station that was previously tested.Make an exposure immediately preparation is completed, and record the mA output. If the change in mA is more than 5%, contact the service provider for advice. The generator should have the pre-heating adjusted, or else a small increase in preparation time.


• X-ray Overload Protection– Radiation reproducibility tests, using a step-

wedge• This test should be carried out after the film

processor has received its general maintenance.



wedge (Part 1)1. Adjust the FFD to 100 cm.2. Place the stepwedge on a 24/30cm cassette.

– Several exposures can be made on the one piece of film.

1. Place two pieces of lead rubber on top of the cassette, positioned against either side of the stepwedge.– As the stepwedge is repositioned, the lead rubber

prevents unwanted radiation entering the cassette.


• X-ray Overload Protection– Radiation reproducibility tests, using a step-wedge

(Part 2)4. Select a suitable mAs and kV combination, and make a total

of four exposures.– Allow about 0.5–1.0 second delay after preparation is

completed, before making each exposure. This is to ensure the filament has reached a stable temperature.

5. After each exposure, reposition the stepwedge and lead rubber on the cassette.

6. Develop the film. As the exposure settings are the same for all exposures, the film should show very little variation.

7. If necessary, change kV or mAs so the film displays a good range of densities, then repeat this test.



wedge (Part 3)• Make another series of four exposures, using the

same settings as before (Part 1 and 2)

1. This time, do not delay the exposure, but expose immediately preparation is completed.

2. This is a test for filament pre-heating, or temperature stability.


• X-ray Overload Protection– Radiation reproducibility tests, using a step-wedge (Part 4)– Compare all eight exposures. If available, use a densitometer.

As the same output settings were used, the exposures should show very little variation.

1. If the second group is lighter, or darker, than the first group, the filament pre-heating or preparation time should be adjusted. Contact the service provider for advice.

2. In case there is a general variation of densities in either group, this may be due to power mains voltage fluctuations. If suspect, repeat this test at a later time when power is more stable.

3. Variable output can be caused by a poor connection to the X-ray tube filament. This is due to a problem with the cathode high-tension cable, where the cable-end plugs into the X-ray tube housing.



wedge (Part 5)A. Repeat the test (Parts 1 – 4) for each focal spot.

B. Record the settings used in the maintenance logbook for future use. Include which cassette used.

C. Retain the test films for comparison with future tests.


• X-ray Overload Protection– X-ray output linearity test, using a step-

wedge (Part 1)• This test will indicate variations in kV output as well as

mAs.1. Select an mAs value that can be repeated over a number

of mA stations by changing time factor only. (To avoid possible errors due to kV rise and fall time, avoid exposure times below 0.02 seconds.)

2. Set 80kV, and a FFD of 100 cm.3. Position the stepwedge on a 24/30cm cassette.

• Several exposures can be made on the one piece of film. 1. Place two pieces of lead rubber on top of the cassette,

positioned against either side of the stepwedge.


• X-ray Overload Protection

– X-ray output linearity test, using a step-wedge (Part 2)

5. Using the selected value of kV and mAs make a series of exposures. Change the mA station after each exposure, and adjust the time to obtain the same mAs.a. Allow about 0.5–1.0 second delay after preparation is

completed, before exposing. This is to ensure the filament has reached a stable temperature.

b. If the film is too light, increase the kV, and repeat the test.

c. If the film is too dark, add extra aluminium under the step wedge. Or, place a sheet of paper between one side of the film, and the intensifying screen in the cassette.


• X-ray Overload Protection– X-ray output linearity

test, using a step-wedge (Part 3 Test Results Interpretation)

• It may not be possible to obtain the same mAs value for all mA stations. In this case, select a different mAs value, but include one of the mA stations previously tested. Repeat the test with the new selection of mA values.

• If one of the mA stations shows a significant change in density, make another test with that mA station, this time change kV to obtain the required film density. (Part 4)


• X-ray Overload Protection– X-ray output linearity test, using a step-wedge (Part

4)1. Providing the required kV change is not more than 2~3%, the station is

within tolerance.2. If no more than 3~5% it is still within tolerance. However, make a note in the

maintenance record, and have the calibration checked next time the service provider pays a visit.

3. If greater than 5%, then that station is out of tolerance. This may be due to mA or kV calibration. If significant, then place that mA station‘out of operation’ and contact the service provider for advice.

4. An estimation of mA calibration error can be made by a comparison exposure, changing time only. This needs an initial time setting of 0.1 second or greater. For example, if the suspect mA station of 200 mA showed a low output, and on changing the exposure time to 0.11 second still showed a slightly low output, then the mA station is more than 10% out of calibration.

5. Besides a possible change of mA or kV calibration, the timer may not be accurate. Check its Timing Circuit for the exposure.


• X-ray Tube Stand (Part 1)1. Inspect for any loose panels or sections. Pay particular attention to

the collimator and the control panel.2. Check the tube-stand suspension, tracks and bearings.3. With the X-ray tube set to minimum height, check the vertical

suspension wire rope for broken strands.CAUTION, do not test with bare fingers.Test by rubbing the cables up and down with a piece of rag.

4. With the vertical lock released, the X-ray tube should balance in the vertical direction. It should need the same effort to move either up or down.

5. Check the action of the tube-stand bearings.– Are there any visible gaps between the bearings and the track surface?– Are there any ‘clunking’ noises or ‘jerking’ movements, when the X-ray

tube is positioned?– This can indicate damaged bearings.


• X-ray Tube Stand (Part 2)6. Check the vertical guide rails. Look for loose mounting

screws.7. Spray the tube stand vertical guides and bearings with a light

aerosol lubricant. Wipe down afterward, so only a thin oil film is left on the vertical guide rails.

8. Clean any accumulated dirt on and inside the floor track. Spray the track and tube-stand floor-bearings with a light aerosol lubricant.– Wipe off any excess lubricant.

9. Look for loose mounting screws along the floor rail.10.Observe the position of the bearings on the ceiling rail.

• These should be fully engaged along the full length of the rail. • Check the rail is properly fastened in place, and does not move.


• X-ray Tube Stand (Part 3)• Lateral centring over the Bucky table should be

checked in both directions. In some cases this may be accurate only when approached from one direction.


• X-ray Tube Stand (Part 3) Lateral Centring1. Tape a thin piece of wire, or a paper clip, to the centre of a

4/30cm cassette. Place the cassette in the Bucky.2. Position the X-ray tube to the lateral centre position.3. Adjust the table top also to the lateral centre position.4. Bring the collimator face to rest on the tabletop, and ensure it is

flat against the tabletop. Then riase to 100 cm S.I.D.5. As the collimator moves away from the tabletop, check that the

light beam remains central to the tabletop. If not, adjust the tube angle a small amount so the light beam remains in position.

6. If the tube-stand centre position appears incorrect,this may need adjustment. Before adjusting, continue with the rest of these checks.

7. Place the X-ray alignment template on the centre of the tabletop.8. Adjust the light beam to the template markers.9. Select a low kV and mAs, expose and develop the film.


• X-ray Tube Stand (Part 3 Test Results)– The radiation field should be centred to the

template markers. If not, the collimator requires adjustment.

• This should be corrected before any adjustment to the tube-stand centre.

• The position of the template marker is compared to the wire marker on the cassette. This checks the tabletop centre accuracy.


• X-ray Tube Stand (Part 4)– To be done if Tube Stand passes Part 3

1. Keep the X-ray tube rotation in the trunnionrings at the same setting for the Table Bucky.

2. Bring the collimator close to, or up against the wall Bucky. • The light field should be centred to the Bucky-centre

mark.

1. Move the tube stand away from the Bucky to the distance normally used. • The light beam should remain centred.


• X-ray Tube (Part 1)– Check rotation of the X-ray tube in the trunnion rings. The locking device should

hold the housing firmly in place, but allow free rotation on release.– Ensure no attachments, such as a command arm control panel, or collimator,

have become loose.– Examine electrical cables to the X-ray tube. Ensure they are securely clamped

into position, and not subject to being pulled. Where cables pass into the housing, they should be protected from sharp edges.

– Inspect the HT cables for any sign of damage to the safety earth shield, at the X-ray tube cable ends.

– Ensure the HT cable ends are firmly inserted into the X-ray tube, and the securing ring nut is not loose.

• In some systems there is a locking screw on the side of the ring nut. Undo this screw first, and then check the ring nut is fully tightened, then refasten the locking screw. This check is most important if the X-ray tube or cables have recently been replaced.

– Where there is evidence of twisting or pulling on the HT cables, particularly at the X-ray tube receptacle, investigate means of providing additional support.

– Examine the X-ray tube housing for any oil leaks.– At the generator, go into preparation, then release preparation without exposing.

Listen to the anode rotation for excessive noise.


• X-ray Tube (Part 1 Continued)– If a high-speed tube, check that the anode

brake cycle operates normally.1. Some systems use direct current (DC brake) to

bring the anode to rest.

2. Other use alternating current, to bring the speed down to 3000 rpm, after which the anode coasts to rest.


• X-ray Tube (Part 2)– X-ray tube seasoning

– This is also called ‘ageing’, and is a process to reduce residual gas in the X-ray tube. Seasoning improves the stability of the tube, when operated at high kV.

– Seasoning should always be performed if a new Xray tube is installed, or has not been used for more than one month. The same applies where the tube has not been used over 80~90kV for some time, and then it is desired to use 110 kV or higher.


• X-ray Tube (Part 2)– X-ray tube seasoning

• If using an X-ray tube of 125 kV capacity at 110kV or higher, seasoning should be performed each day prior to use. If the tube is rated at 150kV, the same applies if operating above 125kV.

• During seasoning, an X-ray tube may at first appear unstable. After two to three exposures,the tube should now be stable.


• X-ray Tube (Part 2)– X-ray seasoning

• Many manufacturers specify a seasoning procedure.

• This can be found in the X-ray tube operation or installation manual. Operation or installation manuals for mobile generators may include a seasoning procedure.

Verification / Recalibration• X-ray Tube (Part 2)

– X-ray Seasoning• Recommended output is 200 mA

and 0.1 sec for 20 mAs. For 10 mAs use 100 mA and 0.1 sec.

• Steps 1,2, and 3 are only required if the tube is just installed, or has not been in use for more than one month.

• If, for example, you never use above 125 kV, then ignore steps 11 and 12. iv. ** Although an X-ray tube is rated at 150 kV, this is the absolute maximum rating. This can reduce as the tube becomes worn, and especially as metal evaporation collects on the glass.

• Operation above 140 kV may result in premature failure.


• X-ray Collimator– Alignment Test (Part 1)

• Check the crosshair alignment of the front transparentcover.1. With the collimator blades almost closed, the crosshair

should be in the centre of the light field. Check at both horizontal and verticalsettings.

2. If adjustment is required, on most collimators, the cover may be moved after loosening the four retaining screws. (In some cases, the cover may at first stick in place.)



• Check the Bucky centre light, if fitted. • The collimator has a scale combined with the adjustment

knob to indicate the field size. The knob can slip on the shaft, or not be correctly positioned after replacing a collimator globe.



1. Place a 24/30cm film on the tabletop, and position the X-ray tube 100cm above the tabletop.

2. With the collimator light switched on, adjust the light field to the film size.

3. Check that the knob pointer indicates the correct position on the scale.

4. If necessary, reposition the knob on the shaft.5. Repeat this test for other films in use.6. If the scale is worn or not legible, contact the service provider and

obtain a new scale. In the meantime, use a marker pen to indicate positions for common cassettes in use.

7. Attention to the scale is important. The lamp might fail, and the spare globe has already been used.



• To test the alignment of the X-ray to the light beam;1. Place the X-ray alignment template on a 24/30cm cassette.

2. Collimate the light beam to the outer 20 by 26cm rectangle.

3. Make a low KV and mAs exposure.

4. Develop the film.

5. In many cases the collimator is enabled to rotate. Repeat the above test, with the collimator rotated 90 degrees clockwise, and then 90 degrees counter clockwise.

Verification / Recalibration• X-ray Collimator

– Alignment Test (Part 4)

1. Does the alignment meet the required compliance?2. Two versions are provided as an example only. The actual compliance requirement

will depend on individual country regulations.1. The X-ray field edges should not deviate by more than 2% of the distance between the plane of

the light field and the focal spot.[ a1 ] + [ a2 ] £ 0.02 ¥ S.[ b1 ] + [ b2 ] £ 0.02 ¥ S.

1. Where S is the distance from the focal spot, a1 and a2 are the two sides on one axis, and b1 and b2 are the two sides of the other axis.

– For example, at a FFD of 100 cm, if the two vertical edges of the light field were displaced by 1.0cm, this would be at the limit of acceptance.

– If only one edge was displaced, then 2.0cm is at the limit of acceptance.1. Another version has a different requirement. The total misalignment of any edge of the

light field with the respective edge of the irradiated field must not exceed 1% of the distance between the plane of the light field and the focal spot.

– For example, at a FFD of 100 cm, the maximum displacement of any edge should be less than 1.0cm

Verification / Recalibration• Bucky Table

– Examine the physical condition of the table. Clean the remains of adhesive tape etc from the table body.

• Car polish, designed to ‘rejuvenate’ faded and oxidised paint, can often improve the appearance of an older table. Silicon furniture polish can assist in removing scuffmarks and fingerprints etc.

– Check for loose screws on the tabletop profile rails.• The rails can become loose due to using a compression device.

– Examine the condition of the compression device.• Check for correct operation. Remove the band from the mechanism, and have it laundered.

– Check the operation of switches and indicator lamps.– With an elevating Bucky table, use a tape measure to check the table height at the centre stop

position.– Check the operation of the magnetic locks.

• Some movements may have two or more magnetic locks. Carefully observe these locks and ensure all locks are actually in operation. If adjustment is required.

– Check the operation of the tabletop lateral centre stop.– Where this is mechanical, the spring tension may need adjustment. In case of operation by the

magnetic locks, the stop position is normally controlled by a micro switch. Adjustment of this micro switch can control the width and position of the centre-stop operating position.

– Move the tabletop in all positions. • If there is scraping or binding in some positions, check the position of the locks. Look also for a faulty bearing.

– Spray the bearing tracks and bearings with a light aerosol lubricant, then clean the residue away from the tracks, so only a thin film is left.


• Potter Bucky (Part 1)1. Move the Bucky to both ends of the table. Check that the Bucky carriage

operates smoothly, and that the Bucky lock operates correctly in all positions across the table.

2. Electrical cables to the Bucky should be firmly attached at the Bucky, and no twisting or puling occurs on the cable, at any position of the Bucky.

3. Where there is a folding support arm for the connecting cable, look for possible binding or excessive ‘droop’. This can indicate loose mounting screws.

4. Spray the Bucky track with a light aerosol lubricant, and then wipe the residue from the track.

5. Remove the Bucky tray. With a torch, examine the Bucky interior for lost film markers.

6. Look for loose screws holding the tray handle. Take care not to over-tighten, as this might damage the thread.

7. Test the action of the Bucky tray cassette clamps. If they do not hold the cassette firmly, you have to correct the problem by readjusting them.

8. Spray the moving sections on the underside of the Bucky tray with a light aerosol lubricant. Take care that no residue appears on top of the tray.


• Potter Bucky (Part 2)– Test the grid oscillation.

1. At the generator, select the lowest mA station, 50kV, and exposure time of 1~2 seconds.

2. Ensure the collimator is closed, and the tube is positioned away from the Bucky. Then make an exposure with the Bucky selected.

3. During the exposure, check for smooth operation of the grid.

4. Watch for any shaking, or vibration of the Bucky, as the grid reverses its movement. Or else, just as the grid first starts to move.

5. Should shaking or vibration occur, this can cause reduced sharpness of the radiograph.

Verification / Recalibration• Vertical Bucky

– The vertical Bucky should be checked in the same manner as the table Bucky, but with the following provision for retrieving lost film markers. To inspect, it is necessary to remove the front cover.

1. With power off, ensure the vertical lock firmly holds the Bucky in place. If not, keep the Bucky in position by tying with a rope, or by adding extra weights.

2. Carefully examine the method of attaching the front cover. In most cases this is a series of screws around the front cover. Other systems may attach by screws on the top and bottom sides.

3. If separating profile rails from the front cover, make a small mark so they can be returned to the same position, including left and right, on

4. re-assembly.5. After removal of the front cover, look carefully for any film markers. A torch will help to

locate them.6. Re-assemble the front cover, taking care not to over-tighten any screws.7. Check operation of the vertical lock.8. Vertical movement. Check and lubricate the vertical track. Wipe off any excess.9. Check the rotation or tilt lock.

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Diagnostic X Ray

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