external beam therapy

Examples of external beam therapy in the following topics:

• Therapeutic Uses of Radiation

  • Radiation therapy uses ionizing radiation to treat conditions such as hyperthyroidism, cancer, and blood disorders.
  • It may also be used as part of curative therapy, to prevent tumor recurrence after surgery, or to remove a primary malignant tumor.
  • When external beam therapy is used, shaped radiation beams are aimed from several angles of exposure to intersect at the tumor, providing a much larger absorbed dose there than in the surrounding, healthy tissue .
  • Radiation therapy is in itself painless.
  • Radiation therapy of the pelvis.

• Medical Imaging and Diagnostics

  • Radiation therapy uses ionizing radiation to treat conditions such as hyperthyroidism, cancer, and blood disorders.
  • It may also be used as part of curative therapy, to prevent tumor recurrence after surgery, or to remove a primary malignant tumor.
  • When external beam therapy is used, shaped radiation beams are aimed from several angles of exposure to intersect at the tumor, providing a much larger absorbed dose there than in the surrounding, healthy tissue .
  • Radiation therapy is in itself painless.
  • Radiation therapy of the pelvis.

• Dosimetry

  • The equipment used in radiotherapy (a linear particle accelerator in external beam therapy) is routinely calibrated using ionization chambers or the new and more accurate diode technology.

• Examples and Applications

  • Cyclotrons accelerate charged particle beams using a high frequency alternating voltage which is applied between two "D"-shaped electrodes (also called "dees").
  • Their radius will increase until the particles hit a target at the perimeter of the vacuum chamber, or leave the cyclotron using a beam tube, enabling their use.
  • The particles accelerated by the cyclotron can be used in particle therapy to treat some types of cancer.
  • Additionally, cyclotrons are a good source of high-energy beams for nuclear physics experiments.
  • The magnetron is a self-oscillating device requiring no external elements other than a power supply.

• Holography

  • In addition, however, part of the light beam must be shone directly onto the recording medium - this second light beam is known as the reference beam (]).
  • To prevent external light from interfering, holograms are usually taken in darkness, or in low level light of a different color from the laser light used in making the hologram.
  • The first element is a beam splitter that divides the beam into two identical beams, each aimed in different directions:
  • One beam (known as the illumination or object beam) is spread using lenses and directed onto the scene using mirrors.
  • In addition, however, part of the light beam must be shone directly onto the recording medium - this second light beam is known as the reference beam.

• Center of Mass of the Human Body

  • First, let's take two scales and a wooden beam (H meter long), long enough to contain the entire body of the subject.
  • Put the scales H meters apart, and place the beam across the scales, as illustrated in .
  • Now, let the subject lie on the beam.
  • Make sure that his/her heels are aligned with one end of the beam.
  • The system (person+beam) has three external forces: gravity on the subject (FCM), and normal forces from the scales F1 and F2.

• Lasers

  • When a gain medium is placed in an optical cavity, a laser can then produce a coherent beam of photons.
  • It is excited by an external source of energy into an excited state (called "population inversion"), ready to be fired when a photon with the right frequency enters the medium.
  • Some of the light escapes through this mirror, producing a laser beam that is visible to the naked eye.

• Lasers

  • Laser is distinct from other light sources for its high degree of spatial and temporal coherence, which means that laser outputs a narrow beam that maintains its temporal-phase relationship.
  • When such an electron decays without external influence, it emits a photon; this process is called "spontaneous emission. " The phase associated with the emitted photon is random.
  • However, an external photon at a frequency associated with the atomic transition can affect the quantum mechanical state of the atom .

• Biological Effects of Radiation

  • In the case of external exposure, the radioactive source is outside (and remains outside) the exposed organism.
  • Examples of external exposure include a nuclear worker whose hands have been dirtied with radioactive dust or a person who places a sealed radioactive source in his pocket.
  • External exposure is relatively easy to estimate, and the irradiated organism does not become radioactive, except if the radiation is an intense neutron beam that causes activation.
  • When radioactive compounds enter the human body, the effects are different from those resulting from exposure to an external radiation source.

• X-Rays

  • The ionizing capability of X-rays can be utilized in cancer treatment to kill malignant cells using radiation therapy.
  • This is called hardening the beam since it shifts the center of the spectrum towards higher energy (or harder) X-rays.