X-Ray Radiology was the first thing that was done during and after discovery. Truly it’s a revolution in the field of medicine and diagnosis.
During that period it was amazing for peoples to see broken leg x-ray or broken arm x ray or x-ray normal chest with their bare naked eyes.
Of course, they were not familiar with harmful side effects at that time.
At that time lots of generals and notes were published on x-ray but all were not based on scientific study. Many of them talk about the magical power of god thing.
But in short, this invention finds the attention of the majority population at that time.
Here going to explain probably every expects of the x-ray in detail, of course, a major part will be associate with medical x-Ray.
Although will try to cover other than that like how to change astronomy.
X Ray Radiology History Timeline
This section going to mention important events because most of the places in the name of x-ray will get a detailed history.
Also want to assure you won’t miss anything here.
The story starts around 1869 A.D. when researchers start experimenting with cathode rays and crooks tube introduce about 1875 A.D.
Crooks tube nothing but consists of two electrodes (anode and cathode) inside the glass at a distance and vacuum inside the glass tube.
Later Philip Lenard makes changes in crooks tube was that making a window on the anode side with covered thin aluminum foil.
Observed that cathode ray after the strike to anode passing in air and affecting photographic fluorescence plates.
Many other scientists including Tesla were experimenting.
In 1895 AD Wilhelm Röntgen submitted his paper “On a new kind of ray: A preliminary communication” to the Physical-Medical Society journal.
Based on Lenard and crooks tube experiments and predict unknown radiation which crosses the covered tube and affects photo film plate as named X-Ray.
In his experiments shows the unknown rays can be used for photography of human inner body parts.
Earlier all the tubes were cold cathode tubes which means there was not any electron emission filament.
In the year 1913 AD William David Coolidge introduce the hot filament cathode tube also known as thermionic emission tube. The same principle is used in vacuum tubes.
Still, the same method was used in tubes. Later in 1937 AD rotating anode come into the market and add graphite after that to increase heat dissipation.
Similarly, in 1948 AD Image Intensified Fluoroscopy was manufactured.
In 1971 AD Sir Godfrey Hounsfield invent CT Scan. Which was a great step in X-Ray Radiology.
What is X-Ray
Radiation(Ray) means a wave stream of photons (or quantum), which shows dual nature as a particle and like electromagnet waves.
The energy of photons represent by E = hv, where E is the energy of the photon, h is plank constant and v is the frequency of the photon.
Inside the x-ray tube when high-speed electrons hit the high melting point material anode target then electrons converted into photons with the energy range of x-ray.
It is a type of electromagnetic radiation similar to visible light but due to its shorter wavelength (1A), it can pass through matter with little attenuation where visible light absorbs or reflect from matter.
Also can remove or add electrons into atoms of matter that’s why called it Ionic radiation. The property is used for the formation of an image on photographic film.
Finally, this is the reason it can harm the living tissues of our body if over-exposed. Behave neutral, when applying an electrical or magnetic field across.
How are x ray produced
As shown in the below image is standard x-ray production tube design and going to explain in detail.
Remember here hot cathode (filament) consider as electron source because cold cathode has been stopped manufacturing long ago.
The tube is the core element of any x-ray based machine because for more than 100 years the method or device (tube) for x-ray production never changed. Although some improvements are made over a period of time.
But the core element could not be replaced, therefore the x-ray tube is a very less efficient system.
Only 1 percent of input power converted into x-ray. Almost 99 percent of input energy converted into heat for which cooling mechanism also makes complexity as we generate a higher amount of x-ray.
It is a Pyrex glass container with a strong vacuum and all the components ( filament, anode, cathode) reside inside of it.
Pyrex glass is also used in cookware because of its stability against high temperatures and pressure (vacuum).
X Ray Tube
Here in the image cross-section view of various components of the tube are present. Those components going to explain one by one.
Casing or Housing and it’s components
Tube housing is made of lightweight and good thermal conducting material like aluminum with an inner layer of paint coating of lead.
Keeps all the components airtight from an outer atmosphere like pressure, humidity, etc.
Firstly need to know lead is the metal witch block the radiation and never allow it to pass through it. Therefore it is used in those devices or places where need protection from harmful radiation. Like lead apron for X-Ray technician.
The gap between insert and housing filled with mineral oil which serves two purposes.
First, it works as an electric insulator, and second, it transfers the generated heat from insert to atmosphere through the casing.
For high capacity, x-ray tube oil flows from the tube casing to the external heat exchanger, and cooled oil flow back to the housing.
Now days almost all CT Scanner tube has external heat exchanger.
Made from flexible rubber so that if oil expands due to heating can provide space for expansion so that oil can not make pressure on vacuumed Pyrex glass insert.
When oil shrinks it does the opposite to the expansion of oil. But never allow atmospheric air to mix with oil.
Window or Focal Spot
It is the place where the X-ray comes out from the tube. A window is just placed down to the anode target and 90 degrees from the filament cathode cup.
Receptacles or High voltage connectors
Specially designed for carrying high voltage with proper insulation from the surrounding.
Designed to deliver up-to 140 KV DC to the tube.
X Ray Tube Insert
That is the main unit of any X-Ray tube. Apart from the insert rest of the things may or may not be present but the tube insert must be there.
Although in the high capacity tubes use Metal-Ceramic Insert instead of Pyrex glass. ceramic used for high voltage insulation and high-speed rotor support.
Metal-Ceramic Insert provides high life. Decrease off-centered radiation and avoid arching inside the insert due to filament vaporization because metal case makes it possible to make it ground.
The section of the insert where negative high voltage is applied. It consists of filament and focusing cup where negative high voltage is applied.
In general focusing cup and filament keep on the same negative high voltage. The X-Ray tube filament is similar to the filament of florescent tube light in our house.
Made from spiral coiled tungsten wire, when a current pass through it then the thermionic effect comes into the picture, and electron emission starts.
The amount of electron emission depends upon the amount of current supplied. Some of the X-Ray tubes have two filaments called small focus and large focus.
The small focus is used for high resolution and small areas, on the other hand, a large focus is used to scan large areas of the body.
Anode and Target
Those part of the insert where positive high voltage is applied and the target is the point on anode where electron beam strike and produce X-Ray.
The target angle kept 45 degrees from the direction of the electron beam so that it can go out from the window at 90 degrees from the beam direction.
Target or anode need a high melting point and good heat conductor for quick heat dissipation.
To make such an arrangement stationary anode x-ray tubes use tungsten plate as a front target because of high-temperature sustainability and back-side thick copper support for good thermal conduction.
Mammography uses molybdenum and another element as targets for produce low energy x-ray.
Mostly modern high energy x-ray tubes have rotating anode. Rotating RPM up to 15000 and maybe more.
Why need to rotate anode?
When need to produce high energy X-Ray then produce a high energy electron beam which strikes to target material and transfer its 99 percent of heat.
After sometime target element say tungsten can not withstand even provide copper cooling and target metal meltdown and form pits(small hole). So need heat dissipation fast.
The idea was behind the rotating anode to replace the target spot before it meltdown with a colder place of anode till then it goes cool down and ready again for beam strike.
For rotating anode inside the vacuum glass or metal insert without any physical contact implement the induction motor principle.
To do so anode extended from the backside center as cylinder shape of copper and iron to make rotor inductive. Also, provide bearing inside the insert to move the rotor freely.
When putting two-phase induction coil as stater on the neck of insert (where rotor arm placed inside) and energies coil. Then the rotor starts to rotate along with the anode.
Behind target, metal uses graphite to make anode lighter and efficient for heat dissipation.
Grid Controlled X Ray Tube
Generally, all x-ray tubes have anode and cathode, filament, and focusing cup have the same negative potential.
Grid controlled system introduces one more electrode which can be a more negative potential than filament and focusing cup.
This means the third electrode can act as a switch to turn off and on X-Ray quickly.
Cath lab having x ray tube with grid controlled system.
X Ray Machine
Every machine that uses x-ray has some common units called X-Ray Generator. Even their design may vary but the main function remains the same.
It provides the required electrical supply to X-Ray Tube for two purposes.
First filament needs current to emit electrons from it’s surface.
Secondly, anode and cathode need high voltage direct current(DC) to move electrons from cathode to anode target with very high velocity.
It may be a simple X-Ray machine as we see in hospitals or maybe part of the specific machines like C-Arm, CT Scan, Cath Lab etc.
The above image represents the block diagram of the X-Ray system and here going to explain one by one.
Nothing big deal but a transformer converts three-phase into a single-phase.
Below 5 KVA machine works well on single phase but medium to high power machines can not work on single-phase due to voltage drop during exposer.
Hence static balancer use, the input of the transformer is three-phase and the output is a single-phase. Which is fed to the generator and control system.
Console or Control Panel
The Control panel is the command center from where technicians decide and control all the factors like mA, KVp, and Sec for any exposure. Auto exposure is also controlled from here.
Almost every modern console based on micro-controllers.
HT (High Voltage Transformer)
The name explains itself there is a step-up transformer with a ratio of 1000:1, which indicates if apply one volt AC (alternating current) to the primary of the transformer will get a thousand volt AC from the secondary output.
Similar to HT transformer used earlier in CRT (cathode ray tube) for television. Function and working of both are the same but the capacity of x-ray generator HT is more.
High voltage (KV) can vary from console to vary does for a patient known as a factor.
Why Need High Voltage
Because produce x-ray from an electron beam needs high energy electrons.
When applied high voltage DC (in the rage of Kilo volts) across the electrodes the kinetic energy of the electron beam reach the range so that can produce X-Ray.
For glowing filament and produce free electrons never need high voltage. Generally, the voltage ranges around 15 volts and the current around 3 to 5 amperes.
Similar to KVp, the flow of current (mA) can be controlled or vary from the console during exposure called mA factor.
One more important task done by filament transformer is that it isolates high voltage DC cathode to the rest of the system or circuit.
The rectification is the process to convert alternating current (AC) into direct current (DC) and the device performs such a process called a rectifier.
Probably know direct current flow in a single direction and inside the tube also needs to flow current (flow of electrons) in a single direction.
Therefore after step up the alternating voltage using HT goes to the input of the rectifier and rectifier output connect to the anode and cathode respectively.
Light Beam Diaphragm (collimator) attached to the window of an x-Ray tube. The basic work is to regulate the shape and size of the beam.
The aperture diaphragm is made from lead and can control the output beam in x and y rectangular direction.
Helps to focus the beam on the region need to expose and can be adjusted if required. Cone and cylindrical size collimators also use in other kinds of applications.
Dose Measuring Sensor for Auto Exposure
Device used to control and monitor amount of x-ray and it’s time.
In the beginning, the ionization chamber was used, It consists of electrodes and gas inside the glass tube.
When x-ray passes through the chamber it ionizes the gas and electric conduction starts in the circuit.
With the help of such electric conduction control the exposure time parameter. Also, the strength of the current represents the intensity of the x-ray.
The later device used a fluorescent screen and photomultiplier for the same reason.
Here fluorescent screen converts x-ray into photons of visible light, picked by a photomultiplier for converting into electrical signals.
Now in modern days, solid-state photo-timers are in use because of convenience.
Grid and Bucky
The arrangement of lead strips is placed between patient and film introduce by Gustav Bucky in 1913.
The reason was to reduce the scattered radiation in the form of noise and thereby increase the image quality.
Scattered radiation is a noise factor that reduces the image quality by its fogging effect. Grids (lead strips) are specified in terms of their ratio and frequency.
The ratio of the height of the lead strips to the distance between each of them and grid frequency is the number of lead strips per inches.
Grids assembled with cassettes (film holder) or attached to it. For small capacity, mobile units use stationary grids.
To move grids set in oscillation during exposure arrangement called bucky.
Thus eliminates the grid lines of stationary grids, appearing in the X-ray film. Bucky is used in radiography of large, dense body parts.
Cassette and Radiographic Film or Detector
Most of the human body part consists of bone and tissues which have different density.
Due to variations in density, the x-ray can not pass through completely. Some of the x rays absorb, some reflect, and the remaining passes through.
All the above depends on the density of tissue or bone of the body. Denser means more absorption and reflection and less dense allow to pass maximum radiation.
These changes in contrast can be recorded on the radiographic film as an impression of the anatomy record of the body for comparison and study for abnormalities.
Similar to those photo films used in old days before digital camera taking pictures from the camera.
The difference is only that it uses for x-ray radiation image capture instead of visible light. Film material consists of three kinds of material Base, Emulsion, and Coating.
The base is made from cellulose or resin to spread the emulsion uni formally. An emulsion is a gelatin solution with suspended microscopic crystals of silver halide.
Above all, there is a protective coating on the film to protect the emulsion solution.
Now in modern time, the phosphor-based film is used to convert image directly into a digital form known as computed radiography (CR) the replacement of old films.
A silver emulsion is replaced by a phosphor screen for capturing the latent images. Later when scanned from fine laser beam emits blue light in the respective amount of absorbed x-ray.
Which is captured by a photomultiplier (PMT) for creating a digital version of the image.
A case that keeps the film inside during exposure, which protects the film from the outside light and physical damage. Also allows the film to be exposed to the X-ray beam.
It comes in different sizes for films are available, according to the body part that needs to be exposed in an x-ray.
The cassette consists of one more thing that is Intensifying screen.
It has microscopic crystals of phosphor (luminescent material ) dissolved with binding agents and form a layer on one side of the white reflecting base.
Phosphors are crystalline materials that emit visible light when struck by X-rays called luminescence. One X-ray photon converts into 300 light photons after striking a phosphor screen.
Intensifying screens produce visible light photons that reflect the variation in exposure across the X-ray beam.
An impression of light is printed on film that is sensitive to the wavelengths of the light emitted by the screen.
Hence the exposure required for a specific film blacking can be reduced by using the intensifying screens, thereby the patient x-ray dose can be reduced.
The device directly converts x-ray into an electric signal and later converted into a digital image. It replaces the cassette in the x-ray machine.
The most common detectors are flat panel detectors (FPD). Inside the flat panel detector, an x-ray is converted into electrical signals in various ways, and thus it is classified.
X Ray Generator
Group of units in any machine which controls the exposure techniques parameters like kV (High Voltage generator), mA (filament heating), and Time (direct or automatic exposure).
Thus generate required energy to generate x ray from tube.
Single Phase X Ray Generator
Low cost • 100 % ripple present • Also produce not required soft X-rays (absorbs but never helps to image formation) • kV control by steps (By using stepping transformer) • require high power mains outlet arrangement • Heavy Transformer
Three Phase X Ray Generator
Similar to the single-phase x-ray generator only uses three-phase so that can run high-energy x-ray machines.
High Frequency X Ray Generator
Very less soft X-rays (fast ramp-up) • Accurate and flexible kV adjustment • Small in size and lightweight • Still require high power mains outlet
Inside the HF (high frequency) generators convert a 60 Hz power supply to 6500 Hz through the chopper section before entering the HT (high voltage transformer).
The transformer core is made from ferrite core so that it can work on high frequency and the size of the transformer also small.
The ripple factor is very less and the voltage across the tube is almost constant.
Ripple Factor is the difference between the minimum and maximum voltages expressed as a percentage of the maximum voltage.
The ripple factor for various generators are :
single phase, 2pulse 100 %
Three Phase, 6 pulse 13 to 25 %
Three Phase, 12 pulse 3 to 12 %
High Frequency 1 to 12 %
DC output 0 to 4 %
Mobile X Ray Machine
Those x-ray units designed such a way to carry or pull on the field hospitals, accident site, war zone, or at least up to the patient’s bed.
Machines are low capacity and need very less power if I’m not wrong some are generator or battery operated.
The main utility is when a patient is not in the condition to move or mobilize then carry the machine to the patient and start further diagnosis/treatment.
Dental X Ray Machine
Dental radiography or radiology also part of x-ray radiology for study and diagnose malignant, infection, benign masses, dental structures, bone loss, or cavities inside teeth and gum.
There are two ways to do dental x ray.
Panoramic x-ray or OPG: In this method patients head fixed at a point between the x-ray source and detector or film. Also, the source and detector move around the patient’s head in a coaxial fashion.
Such a way to acquire the image of the whole mouth including jaw, gum, teeth, etc. on a single film or detector.
Now in the latest machines are available which can convert acquired 2D image into 3D.
In another way, the dental film or detector is placed on a specific part of the mouth where an x-ray needs to be done and exposed by placing the source from the opposite side.
Dental X Ray while pregnant
Even doctors never advise x-ray, ct scan, or other x-ray based diagnosis investigation during the pregnancy.
But according to the American college of radiology up-to second trimester of a pregnant lady dental x-ray is safe.
Because the whole dental x-ray uses a very small dose of around 0.150 mSV which is almost equivalent to the dose received during international air travel.
The process to view movements inside the body in real-time using x-ray. The history of fluoroscopy started when x-ray discovered.
When the x-rays passed through the patient’s body and fall on a fluorescent screen, the body can be viewed from inside through a lead glass, in a dark room.
But in this procedure has limitations. Further the image brightness and quality are not so good to diagnose.
Radiologists and technicians must be close to the x-ray source and will absorb more radiation as they have to have to spend more time to get accommodated to the darkness.
To overcome such problems such a problem device introduce system is known as image intensifier (IITV).
When the output of the fluorescent screen passed through a phosphor ( Cesium Iodide ) screen and converted into light photons.
These light photons are converted into electrons using the photocathode.
The photons strike across the tube, accelerated by the potential difference app. 25000 volts between anode and cathode.
At the anode end, the output phosphor converts the electrons into light photons.
The image received on the IITV system is a piece of analog information. To do the storage of the information, need to do either spot filming or Cine camera recording.
Nowadays Imaging equipment allows analog information to be digitized using Analog to Digital Converter.
That can be viewed on monitor at safe distance even in light.
X Ray Tech vs Radiology Tech
Although the working of X-Ray Tech vs Radiology Tech is quite similar the main difference is about their education levels.
The radiology technician has a complete four-year degree in radiology equipment operations and nursing related to patient handling during diagnosing.
They have wide and deep studies about MRI, Liniac, and other high ends sophisticated radiology/radiotherapy equipment.
Also, it makes big difference in their salary. Although experienced and good radiographers get a good salary in most countries.
More importantly they are still in demand.
Broken Arm X Ray
Broken Leg X Ray
X Ray Normal Chest
Dangers of X Ray
Now a day almost everybody knows the harmful side effect of X-ray but early in the time, it was used for shoe size and other fancy purposes.
Due to the harmful side effects observed in an earlier time, the regulatory body strictly controls and regulates the use and dose of x-ray.
Mostly used in x ray radiology for diagnosis and therapy purposes.
Especially diagnosis purposed the dose of an x-ray is very low like one chest x-ray is equivalent to 10 days outer natural atmosphere x-ray.
Dental x-ray dose is equivalent to only a one-day natural environment x-ray dose.
At the airport x-ray scanners uses fewer doses of x-ray radiation as compared to diagnosis medical purposes.
Because for medical purposes need more detailed contrast images of tissue and other body parts.
But still, ct scan or x-ray radiation increases the risk of cancer from 1 in 1,000 to 1 in 10,000.
Scientists and engineers continue experimenting on how to reduce the doses for diagnosis purposes without affecting the quality.
Application of X Ray Uses
As it discovered the application for medical purposes started, although other x-rays radiation-based products launched on time to time.
As awareness spread out about the harmful effects of radiation can be the cause of death the regulatory banned such products.
Now uses are under strict guidelines and limited.
Medical or healthcare
The first application of this discovery for medical purposes. The first picture was the palm of Mrs. roentgen. From that time lots of devices were developed.
Radiography or X Ray
The basic principle of radiography never changed although the devices were improved over a period of time.
Above in the article discussed a lot about it from the beginning.
Computed tomography (CT Scan)
Using x-ray shows the cross-section area of our body organs were developed around 1970. Now it is widely used for diagnostic purposes.
A written separate article on CT Scan if you wish to know more about it.
Present-day the digital fluoroscopy used for Angio, Cardiac, and R & F examinations.
The radiation beam directly focused on cancer tissues to stop their growth.
Also, a kind of 2D radiography (x-ray) machine is specially designed for the diagnosis of breast-related abnormalities.
Other X Ray Uses
As you see the X-Ray radiation is very useful in the medical field it does not mean its application stop here.
Other than the medical uses are also very specific for industries, transportation safety, and scientific study.
X Ray Microscope
Industrial Radiography and Computed tomography (CT Scan)
Used to view products from inside for any crack or any abnormality inside the product. The density and proper material composition of the finished goods.
The wavelength of an x-ray is so small that it can cross through the atom. such a small size can be used to study and visualize the matter crystals structure.
At the airports, the passenger’s baggies and their whole body scanned to verify whether they are carrying something illegal or not.
To verify the density of the material they come to know the material is illegal (like drugs) or not.
X Ray Astronomy
Around the cold war, the x-ray/gamma astronomy started accidentally not in a very planned manner.
During the cold war, America started spying on Russia to know it’s nuclear bomb testing.
Then one day their satellite receive a strong radiation signature and then started to find out the source of origin.
Then they come to know that the radiation does not originate from earth even that much strong radiation pulse is not possible to generate on earth.
After further investigation then they come to know that the source of radiation was in deep space and it was the strong gamma buzz.
Thus the astronomy started in the x-ray and gamma spectrum to know more about the sources of such strong radiations coming from deep space but still very strong.
Telescope and devices for observation
As you know observations could not be done from the ground because of most x-ray radiation filters out by the earth’s atmosphere.
In such a way it protects all the living creatures from harmful radiations. Hence observations are taken by balloons, rockets, or satellites.
Satellite x-ray telescopes like Chandra x-ray observatory really give us very useful information about the universe.
There were so many things, not able to see now is possible.
Study about stars just a small part of it. Now it was possible to see there where we thought it is an empty place.
About neutron stars, quasars, magnetar, and more above that black holes know so much because of x-ray astronomy.
Above all places are surrounded by hot gases and visible light can not pass through them but high energy radiation can cross everything so that we can see inside those things.
Here tried to explain about x-ray in a very simple way also try to cover maximum parts of the subject.
But still, things remain to explain like X-Ray Table, astronomy, applications, and more.
Still need to know can comment. wish to discuss a problem in detail write me on the forum. Register with all small letters then ask questions that even can create a topic.
What is X Ray used for?
Radiology (healthcare) and Security checks on the airports. These are two uses that almost everybody aware of because in the lifetime they go through it.
Even in healthcare lots of different machines are based on x-ray are used for different diagnoses or treatment purposes like C Arm, CT Scan, etc.
On the airport use also similar to healthcare to see inside of body or baggage for illegal kinds of stuff.
Apart from that uses in the microscope to the telescope (Chandra X ray). In the industries to check the quality of finished goods from inside without cutting it.
How are X Ray produced?
The way x ray produced is never changed since 1895.
when it was discovered although the modification and improvements are made over a period of time.
In a vacuum tube two electrodes anode, cathode, and one electron source as shown in the image.
When applying high DC voltage between anode and cathode the electrons strike on anode with high velocity and produce 1 % x ray of energy given.
Are X Ray harmful?
Of course, it is ionic radiation which means a high energy beam can remove electrons from atom thus it can damage our body tissues.
That could be the reason for cancer or abnormal development in babies or fetuses or adults also.
The uses of x ray are very strict guidelines of government and setup government regulation departments.
For diagnosis purpose or on the airport uses very small doses are not harmful until never expose so much.
What are the types of X Ray?
As per medical purposes, there are two types soft and hard. Soft x ray absorbed by the body and never useful to produce an image.
On the other hand hard types cross the body tissues and attenuate according to their density and make impression on film and produce an image.
To avoid such soft radiation use metal filters on the tube window to stop strike on body parts going to expose. Usually, the metal used for the filter is copper or aluminum plate.
Rest of the source body covered with lead coating or plate to block radiation inside the source (tube).
Secondary or scatter radiation also harmful and need to avoid while the body comes in contact with the radiation source.