Roentgenology X-ray

Roent Lec 1

Historical Background

- X-rays were discovered in Nov. 8, 1895 by William Konrad Roentgen (pronounced as “rentken”)

- He pioneered 3 keys areas of x-ray imaging:1. An x-ray photograph of his closed wooden box

of weights clearly revealed its contents, thus presaging the security application found at every airport check-in.

2. An x-ray image of his hunting rifle revealed a flaw inside the metal of the gun. This was the first time a hidden structural flaw had been exposed without destroying the object.

3.4. He took a permanent x-ray photograph of his

wife Bertha’s left hand, revealing the bones and the rings that she was wearing.

January 1896 by Roentgen)

-The hand of the cadaver, they injected mercury that reveals the architecture of the hand.

Amputated hand after exposure totoo muchradiation

for 5 years.-

- Roentgen was awarded the first Nobel Prize for Physics in 1901.

- Roentgen announced to the word the discovery of the new kind of ray in 1895; he called it the “X-ray” after the algebraic symbol for unknown.

- Otto Walkhoff, DDS, MD completed the first dental radiograph ever med in January 14, 1896.

- Dr. Otto Walkhoff- first dental radiograph 25 minute exposure (< 0.5 seconds today).

NATURE OF THE ATOM- Matter is a physical manifestation possessing mass

(occupies space and has weight) and having form or shape.

- Elements are simple substances that cannot be decomposed by ordinary means.

- There are 105 known elements at present.- The atom is the smallest particle of an element that

has characteristic properties of that element.- Each atom consists of a small nucleus, which has a

positive charge and a number of lighter particles with negative charges called electrons, which move around the nucleus in definite orbits.

- The atom is said to be neutral when the net number of positive charges of the nucleus (protons) equals the negative charges of the orbital electrons.

- The closer of the electrons to the nucleus, the higher energy level.

- The electrons are kept in their orbits by the balance between:1. The electrostatic attraction of unlike charges.2. The centrifugal forces of the fast moving

electrons.

ATOMIC NUMBER - The atomic number, or Z number, is the no. of

protons in the nucleus or the no. of electrons outside the nucleus.

- Z number range from 1 for the simplest atom (Hydrogen) to 105 for the most complex atom yet discovered (Hahnium).

Orbital Electrons- Electrons are very small particles carrying 1 unit of

negative charge.- They revolve around the nucleus in well-defined

shells that exist at varying distances from the nucleus.

- A maximum no. of seven potential electron- containing orbits or shells are designated as K,L,M,N,O,P and Q in order of increasing distance from the nucleus.

- Electrons in the most outermost shell are termed valence electrons and determine the chemical properties of the atom.

ELECTRON ORBITS OR SHELLS- The electrons in an atom do not spontaneously fly

off from the nucleus by centrifugal force or, on the other hand, drop into the nucleus by electrostatic attraction (unlike charges attract), because in the normal atom there is a balance between centrifugal and electrostatic force.

- This balance results in a definite electron path or orbit for each electron around the nucleus.

- Each shell has a different energy level which is dependent on the atomic no. of the atom and distances the electron from the nucleus.

- The attractions force is greater when the electron shell is nearer the nucleus.

- Thus, it would require more work (energy) to remove an electron from the K shell and out of range of the nuclear electric field than to remove an electron from one of the outer shells.

BINDING ENERGIES- The energy required to remove an electron from a

particular shell is designated as binding energy of that shell.

- The binding energy is characteristic of a given element and shell.

- This is the kinetic energy of an electron accelerated through a potential difference of 1 volt.

- Larger multiple units of the electron volt are frequently used: kcV for 1000 or kiloelectron volts, and McV for 1 million or megaelectron volts.

IONIZATION- Ionization is the process by which a neutral atom or

molecule acquires either a positive or a negative charge.

- When an atom losses or gains an electron, it is said to be ionized.

- An ionized atom (called an ion) is not electrically neutral but carries a charge equal to the difference between the number of protons and electrons.

- An atom that is not electrically balanced is called an ion.

- In any ionization process, ion pairs are formed; it is this process that elicits chemical changes in matter.

- When an x-ray transfers its energy to an orbital electron, it ejects it from the atom, and an ion pair is formed.

- The atom becomes a positive ion (=1 charges because it has lost an electron and the ejected electron has a negative charge (-1) thus, an ion pair has been formed.

IONIZING RADIATION

Types of Ionizing Radiation-Corpuscular or Particulate radiation- Electromagnetic radiation

PARTICULATE RADIATION - Particulate radiations are actually minute particles of

matter that travel in straight lines at high speeds from their sources.

- Although incredibly small, they possess mass.- All are charge electrically, except neutrons, and they

all move extremely fast- sometimes as fast as light.- Alpha Particles are composed of a combination of

two protons and two neutrons.- It is the helium nucleus without orbital electrons.- Alpha particles are emitted only from the nuclei of

heavy metals.- Compared with the other particles, the alpha particle

is enormous and exerts a large electrostatic attraction.

- They have little ability to penetrate tissues and give up their large energies within a very short distance in air (5cm) and in soft tissue (100 um).

- Beta Particles (Negatrons) are emitted from the nucleus of radioactive atoms and possess 1 unit of negative charge.

- They have very small atomic masses.- Beta particles more penetrating that alpha particles

and may penetrate 10- 100 cm of air and approximately 1-2 cm of the soft tissue.

- Cathode Rays (Electrons) are streams of electrons passing from the hot filament of the cathode to the target of the anode in an x-ray tube.

- Beta particles come from the nucleus of radioactive atoms, whereas the cathode rays originated from the orbital electrons of the atoms of the filament material for an x-ray tube.

- Protons are accelerated hydrogen nuclei.- Because protons are heavy, charged particles, the

lose kinetic energy as they penetrate matter.

- Neutrons carry no electron- charge and have nearly the same mass as a proton.

- The characteristic if being electrically neutral has proved of great importance in nuclear physics because such a particle can penetrate into the nucleus of an atom without being subjected to e enormous forces of a positively charged particle.

ELECTROMAGNETIC RADIATION- X-rays and gamma rays belong to a group of

radiation called electromagnetic radiations.- Electromagnetic radiation is the propagation of

energy through space accompanied by electric and magnetic force fields.

- X-rays and gamma rays belong to a group of radiation called electromagnetic radiation.

- X-rays are produced outside the nucleus in the electron orbital system.

- Gamma rays are emitted from the nucleus of a radionuclide.

PARTICULATE and ELECTROMAGNETIC RADIATION

NATURE OF X-RAYS - The wave concept of electromagnetic radiation

explains why it may be reflected, refracted, diffracted and polarized.

- The particle concept is used to describe the interaction between radiation and matter.

X-RAY PROPERTIES1. They are weightless packages of pure energy

(photons) without an electrical charge which travel in waves with specific frequency at speed of 186, 000 miles per second (speed of light).

2. Invisible, highly penetrating waves (electromagnetic waves).

3. Electrically neutral (cannot be deflected by electrical or magnetic fields).

4. Wide useful range of wavelengths in medicine and dentistry = 0.01 is equal to 1 billionth of a meter).

5. Most beams of x-rays are heterogeneous (consisting of rays of many different wavelengths).

6. They emerge from the tube in straight lines, diverging form the focus of the target of the anode.

7. They are capable of ionizing gases because of their ability to remove orbital electrons from atoms.

8. They travel as the same speed as light (1866, 000 miles per second in a vacuum).

9. They cause fluorescence of certain crystals.10. They affect photographic film (producing a latent

image which can be developed chemically).11. They produce chemical and biologic changes (this is

essential biologic cell damage and treatment of malignancies, these biologic changes depend o n ionizations).

WAVE CONCPET OF ELECTROMAGNETIC RADIATION

- Electromagnetic radiation is the propagation of wave-like energy through space or mass at the speed of light (186, 000 miles per second or 3 x 104 m/sec).

- It is called electromagnetic radiation because the energy that is radiated is accompanied by oscillating electric and magnetic fields.

EXAMPLES OF ELECTROMAGNETIC RADIATION

- The radio wave that we hear.- The light waves we see.- The infrared waves that can take pictures in the

dark.- The ultraviolet rays that cause sunburn.- The x-rays.- The gamma rays of the atomic bombs.- The cosmic rays that hinder travel in space. Electromagnetic waves need no such medium as

they can be propagated within and transmitted through a vacuum.

All waves have an associated wavelength and frequency.

The wavelength of a wave is the distance between two successive crests or valley, and is given the symbol λ (the Greek letter lambda, the symbol for length).

- The no.

of

waves passing a particular point during a specific period is called the frequency and I given the symbol

λ (the Greek letter nu, the symbol for number).- It is usually identified as oscillations per second or

cycles per second.- The unit of frequency measurement is the hertz (Hz).- One hertz equals 1 cycle/ sec and 80 Hz is the

standard 60 cycle/ sec.

THE ELECTROMAGNETIC SPECTRUM

What are electromagnetic waves?- All forms of electromagnetic radiation are grouped according to their wavelengths in what is called the electromagnetic spectrum.- All have no mass, no electrical charge and travel with wave motion.- Electricity can be static like what a balloon to the wall or makes your hair stand on end. Magnetism can also be static like a refrigerator magnet. But when they change or move together, they make waves electromagnetic waves.- Electromagnetic waves are formed when an electric field (blue arrows) couples with a magnetic field (red arrows). Magnetic and electric fields of an electromagnetic wave are perpendicular to each other and to the direction of the wave.

THE ELECTROMAGNETIC SPECTRUMRabbits RadioMate MicrowavesIn Infra-RedVery Visible lightUnusual Ultra-violeteXpensive X-raysGardens Gamma rays

RADIO WAVES- Radio waves are made by various types of

transmitter depending on the wavelength. They are also given off by stars sparks and lightning which is

why you hear interference on your radio in a thunderstorm.

- Objects in space, such as planets and comets, giant clouds of gas and dust, and stars and galaxies, emit light at many different wavelengths.

- Some of the light they emit has very large wavelengths (sometimes as long as a mile). These long waves are in the radio region of the electromagnetic spectrum.

Dangers:- Large doses of radio waves are believed to cause

cancer, leukaemia and other disorders.- Some people claim that the very low frequency field

from overhead power cables near their homes has affected their health.

MICROWAVES- Microwaves are basically extremely high frequency

radio waves, and are made by various types of transmitter in a mobile phone, they’re made by a transmitter chip and an antenna, in a microwave oven they’re made by a “magnetron”. Their wavelength is usually a couple of centimetres. Stars also give off microwaves.

Uses:

- Microwaves cause water and fat molecules to vibrate which makes the substances hot. Thus we can use microwaves to cook many types of food.

- Microwaves have wavelengths that can be measured in centimetres. The longer microwaves, those closer to a foot in length, are the waves which heat our food in a microwave oven.

- Microwaves are good for transmitting information from one place to another because microwave energy can penetrate haze, light rain and snow, clouds and smoke.

- Shorter microwaves are used in remote sensing. These microwaves are used for radar like the doppler radar used in weather forecasts.

- Microwaves, used for radar, are just a few inches long. This microwave tower can transmit information like telephone and computer data from one city to another.

- Because microwaves can penetrate haze, light rain, snow, clouds and smoke, these waves are good for viewing the earth from space.

- Mobile phones use microwaves as they can be generated by a small antenna which means that the phone doesn’t need to be very big. The drawback is

that, being small, they can’t put out much power and they also need a line of sight to the transmitter. Thus means that mobile phone companies need to have many …

Dangers:- Prolonged exposure to microwaves is known to

cause “cataracts” in your eyes which is a clouding of lens preventing you from seeing clearly (if at all!). So don’t make a habit of pressing your face against the microwave oven door to see if your food’s ready!

- People work on aircraft carnet decks wears special suits which reflect microwaves to avoid being “cooked” by the powerful radar units in modern military planes.

INFRA-RED- Infra-red waves are just below visible red light in the

electromagnetic spectrum (“intra” means “below”).- You probably think of infra-red waves as heat

because they’re given off by hot objects and you can feel them as warmth in your skin.

- Infra-red waves are also given off by stars, lamps, flames and anything else that’s warm- including you.

Uses: -Infra-red waves are called IR for short. They are used for many tasks, for example, remote controls for TVs, and video recorders and physiotherapists use heat lamps to help heal sports injuries.- Shorter, near infrared waves are not hot at all- in fact you cannot even feel them. These shorter wavelengths are the ones used in your TV’s remote control.

The warmer the object, the more infrared radiation it emits.

- Because every object gives off IR waves, we can use them “to see in the dark. Night sights for weapons sometimes use a sensitive IR detector.

- Gas infrared waves are thermal. In other words, we experience the type of infrared radiation every day in the form of heat! The heat that we feel from the sunlight, a fire, a warm sidewalk are infrared.

- You’ve probably seen TV programmes in which the police helicopter track criminals at night using cameras which can see in the dark. These cameras use IR instead of “ordinary light” which is why people look bright in pictures.

Dangers;

- The danger from too much infra-red radiation is very simple, overheating.

VISIBLE LIGHT

- Visible light waves are the only electromagnetic waves we can see.

- We see these waves as the colors of the rainbow.- Each color has a different wavelength.- Red has the longest wavelength and violet has the

shortest wavelength.- When all the waves are seen together they make

white light.- When the white light shines through a prism or

through water vapour like the rainbow, the white light is broken apart into the colors of the visible light spectrum.

- The light which our eyes can detect as part of the visible spectrum (small).

- There is a lot of radiation around us which is “invisible” in our eyes but can be detected by other remote sensing? instruments and used to our advantage.

- The visible wavelengths cover a range from approximately 0.4 to 0.77 mm (violet to red).

RADIATION

Dangers: - Too much light can damage the retina in your eye.- This can happen when you look at something very

bright, such as the sun.- Although the damage can heal, if it’s too bad, it’ll be

permanent.

ULTRAVIOLET

- Ultra-violet light is made by special lamps, for example, on sun beds.

- It is also given off by the sun in large quantities. - We call it UV.

Uses: - Sun tan- Detecting fake money- Light sure composite- UV in discos (glow in the dark)- Sterilization- Sunlight (vitamin D) The OZONE layer protects the earth from the heat of

the sun. Filters about 95% of heat. Only 5% heat UV reaches earth’s surface.

Dangers: - Sunburn- basal cell CA- Cataract- blindness

X-RAYSUses:

- MRI, CT-scan- Intra-oral x-rays- A drink of barium sulphate. This will absorb x-rays,

and so the patient’s intestines will show up clearly on an x-ray image

GAMMA RAYS- They have the smallest wavelengths and the most

energy of any other wave in the electromagnetic spectrum.

- These waves are generated by radioactive atoms and in nuclear explosions.

- Gamma-rays can kill living cells, a fact which medicine uses to its advantage using gamma rays to kills cancerous cells. Radioactivity is particularly damaging to rapidly

dividing cells, such as cancer cells. This also explains why damage is done by

radiotherapy to other rapidly dividing cells in the body such as the stomach lining (hence nausea), hair follicles (hair tends to fall out) and a growing fetus (not because of mutations, but simply major damage to the baby’s rapidly dividing cells).

Dangers:- Gamma rays cause cell damage and can cause a

variety of cancers.- Cause mutations in growing foetuses, so unborn

babies are especially vulnerable.

PARTICLE CONCEPT OF ELECTROMAGNETIC RADIATION

-Short electromagnetic waves, such as x-rays, may react with matter as if they were particles rather than waves.- These particles are actually discrete bundles of energy having no mass, and each of these bundles of energy is called quantum or photon.- These photon travel at the speed of light.- The amount of energy carried by each quantum photon

depends on the frequency of the radiation.- If the frequency (vibrations per second) is doubled, the

energy of the photon is doubled.- The unit used to measure the energy of photons is the

electron-volt (eV).

WHAT ARE X-RAYS?- X-rays are weightless packages of pure energy

(photon) that have no electrical charge and travel in waves with specific frequency at a speed of 3 x 108 m/sec.

- Their energies depend on the frequency of their wavelengths.

- The greater the frequency of their wavelength, the greater the energy of the photon.

- The greater the energy of the photon, the more readily it will penetrate matter.

PROPERTIES OF X-RAYS- X-rays are invisible and weightless; they cannot be

seen, felt or smelled.- X-rays travel in straight lines, they can be deflected

from their original direction but the new trajectory is linear.

- X-rays travel at the speed to light (3 x 108.? m/sec).- X-rays have a wide range of wavelengths, 0.01- 0.05

nm in length.- X-rays cannot be focused to a point over distance

the beam diverges much like a beam of light.- Because of their extremely hot wavelengths, they

are able to penetrate materials that absorb and reflect visible light.

- X-rays cause certain substances to fluoresce, that is to emit radiation of longer wavelength (it is this property that makes it possible to use intensifying screens in radiography.

- X-rays produce biological changes that are valuable in radiation therapy but necessitate caution when used for diagnostic purposes.

- X-rays can ionize gases that is remove electrons from atoms to form ions, which can be used for measuring the controlling exposure (ionization chambers).