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X-Ray Technology

X-Ray Technology. By: PROF. Dr. Moustafa Moustafa Mohamed Faculty of Allied Medical Science Pharos University in Alexandria. Introduction to Medical Imaging. NON Invasive. Uses of medical imaging Obtain information about internal body

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X-Ray Technology

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  1. X-Ray Technology By: PROF. Dr. MoustafaMoustafa Mohamed Faculty of Allied Medical Science Pharos University in Alexandria

  2. Introduction to Medical Imaging NON Invasive Uses of medical imaging Obtain information about internal body organs or the skeleton to determine a patient’s physical Imaging Modalities: * X-ray (plan , Dental, Panorama, Mammo, Angio, …) * C.T * Ultrasound * MRI * Gamma Camera * PET SPECT

  3. Medical Image • Generated by means of radiation • electromagnetic (EM) • ultrasound • electrons • Displayed for interpretation on • Film • photograph or • computer display monitor

  4. Types of image 1) Projections 2) Dimensional 3D & 4D

  5. 3) Slices • Trans axial - plane normal to a vector from head to toe. • Coronal - plane normal to a vector from front to back • Sagittal - plane normal to a vector from left to right. • Oblique - a slice that is not (at least approximately) one of the above.

  6. Inside the atom The NUCLEUS is made up of PROTONS and NEUTRONS PROTONS have a positive charge. NEUTRONS have no electrical charge.

  7. Inside the atom ELECTRONS have a negative charge. The number of electrons in an atom usually matches the number of protons, making the atom electrical neutral.

  8. Exactly what is an X – Ray? • An x – ray is a form of radiation, that is invisible • Electromagnetic waves of short wavelength with wavelengths between about 0.02 Å and 100 Å (1Å = 10‐10 meters). • Very high energy • Basically gives an “inside view”

  9. The energy of X‐rays, like all electromagnetic radiation, is inversely proportional to their wavelength as given by the Einstein equation: E = hν = hc/λ where E = energy h = Planck's constant, 6.62517 x 10‐27erg.sec ν = frequency c = velocity of light = 2.99793 x 1010 cm/sec λ = wavelength Since X‐rays have a smaller wavelength than visible light, they have higher energy.

  10. X‐rays can penetrate matter more easily than can visible light. • Their ability to penetrate matter depends on the density of the matter • X‐rays provide a powerful tool in medicine for mapping internal structures of the human body (bones have higher density than tissue, • and thus are harder for X‐rays to penetrate, fractures in bones have a different density than the bone, thus fractures can be seen in X‐ray pictures).

  11. History • In 1895 Wilhelm Roentgen, German Physicist, was studying high voltage discharges in vacuum tubes, then he noticed fluorescence of barium platinocyanide screen lying several feet from tube end. • These rays where named • X-rays--invisible penetrating radiation, • X represent unknown in mathematics

  12. William ConradRoentgen • Wilhelm Conrad Rontgen Won the first Nobel Peace Prize for physics in 1901

  13. Early X- Ray Images                                    In Right: Mrs. Röntgen's hand, the first X-ray X-ray of Bertha Roentgen's Hand

  14. Types and uses of X-ray

  15. Various uses of the X - Ray Detect malformations in bones • Treats disorders such as various cancers • Security purposes • Alternatives for cancer detection • Annual physical exams • Pre-surgery evaluations

  16. X-Ray Electromagnetic Spectrum

  17. Evacuated glass tube Target Filament Production of X-rays (1) • X-rays are produced when rapidly moving electrons that have been accelerated through a potential difference of order 1 kV to 1 MV strikes a metal target.

  18. Production of X-rays (2) • Electrons from a hot element are accelerated onto a target anode. • When the electrons are suddenly decelerated on impact, some of the kinetic energy is converted into EM energy, as X-rays. • Less than 1 % of the energy supplied is converted into X-radiation during this process. The rest is converted into the internal energy of the target.

  19. Properties of X-rays • X-rays travel in straight lines. • X-rays cannot be deflected by electric field or magnetic field. • X-rays have a high penetrating power. • Photographic film is blackened by X-rays. • Fluorescent materials glow when X-rays are directed at them. • Photoelectric emission can be produced by X-rays. • Ionization of a gas results when an X-ray beam is passed through it.

  20. X-ray Spectra (1) • Using crystal as a wavelength selector, the intensity of different wavelengths of X-rays can be measured.

  21. X-ray Spectra (2) • The graph shows the following features. • A continuous background of X-radiation in which the intensity varies smoothly with wavelength. The background intensity reaches a maximum value as the wavelength increases, then the intensity falls at greater wavelengths. • Minimum wavelength which depends on the tube voltage. The higher the voltage the smaller the value of the minimum wavelength. • Sharp peaks of intensity occur at wavelengths unaffected by change of tube voltage.

  22. Minimum wavelength in the X-ray Spectra • When an electron hits the target its entire kinetic energy is converted into a photon. • The work done on each electron when it is accelerated onto the anode is eV. • Hence hf = eV and the maximum frequency Therefore,

  23. Continuous (Bremsstrahlung) X-Ray Production

  24. Characteristic X-ray Spectra • Different target materials give different wavelengths for the peaks in the X-ray spectra. • The peaks are due to electrons knock out inner-shell electrons from target atoms. • When these inner-shell vacancies are refilled by free electrons, X-ray photons are emitted. • The peaks for any target element define its characteristic X-ray spectrum.

  25. Characteristic X-Ray Production

  26. Anode Heating • This occurs when projectile electrons excite an atoms outer shell electrons but do not eject them from the atom. • For most X-ray machines, about 99% of the projectile electrons lose energy this way. • Infrared EM radiation (observed as heat energy) is produced when the excited electrons relax and fall back into the original energy level • The amount of anode heating can be reduced by increasing the energy of the projectile electrons so that they cause more ionization rather than excitation.

  27. Uses of X-rays • In medicine To diagnose illness and for treatment. • In industry To locate cracks in metals. • X-ray crystallography To explore the structure of materials.

  28. Conditions for x ray production • Separation of electrons • Production of high speed electrons • Focusing of electrons • Sopping of high speed electrons in target

  29. COLD GAS CATHODE TUBE • glass tube with partial vacuum with small amount of gas, • two electrodes, one negative (cathode) • & another positive (Anode).

  30. Hot Cathode Diode tube • In 1913 W.D. Coolidge invented new type of tube on Edison principal called • Hot Cathode Diode tube. • It made possible the control of mA and kV independently and there by controlling the quantity and quality of x-rays.

  31. PARTS OF X RAY TUBE • Glass Tube • Cathode • Filament • Supporting wires • Focusing cup • Anode • Stationary • Rotating

  32. Main components of x-ray unit are: • ·        X-ray tube • ·        X-ray electrical power generator • ·        Control unit • ·        Film or digital system • In addition to: • ·        Table unit • ·        Bucky film tray and grid system • ·        Suspension system

  33. Introduction X-ray image is a shadow picture produced by x-rays emitted from a point source Image contrast is (((proportion with))) 1- Mass attenuation coefficient of the imaged part 2- Density 3- Thickness

  34. Principles of X-ray tube Battery

  35. Main components of a modern x-ray tube • A heated filament releases electrons that are accelerated across a high voltage onto a target. • The stream of accelerated electrons is referred to as the tube current. • X rays are produced as the electrons interact in the target. • The x rays emerge from the target in all directions but are restricted by collimators to form a useful beam of x rays. • A vacuum is maintained inside the glass envelope of the x-ray tube to prevent the electrons from interacting with gas molecules.

  36. X-Ray Tubes

  37. X‐ray Absorption • When the x‐rays hit a sample, the oscillating electric field of the electromagnetic radiation interacts with the electrons bound in an atom. • Either the radiation will be scattered by these electrons, or absorbed and excite the electrons. • A narrow parallel monochromatic x‐ray beam of intensity I0 passing through a sample of thickness x will get a reduced intensity I according to the expression: • I = I0 e‐μ x or Ln (I0 /I) = μ x • where μ is the linear absorption coefficient, which depends on the types of atoms and the density ρ of the material.

  38. How X‐ray Lose Energy within Matter? • • Photoelectric effect • X‐ray interacts with an electron by giving all its energy to the electron near the nucleus. • It is the most probable way of losing energy • X‐ray energy must be greater than or equal to the electron binding energy to the nucleus

  39. • Compton effect • X‐ray (of energy at least 511 KeV) colloids with a loosely bound outer electron. • The electron receive part of the energy and the rest goes in different direction as a scattered photon radiations each of 511 KeV

  40. Pair production • X‐ray (of energy at least 1.02 MeV) penetrates the intense electric field of nucleus. It is converted to an electron and a positron each of 511 KeV. • The positron will then colloids with one electron and results in the production of two annihilation

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