W&L Flashcards
treatment with x-rays produced between 100-300 kV
orthovoltage
types of tumor commonly treated with orthovoltage
skin, mouth, rectal carcinoa
depth treated with an orthovoltage machine
2-3 cm
most skin lesions treated with orthovoltage are
squamous cell and basal cell
1—300 kv xray beam (orthovoltage) is more effective in treating superficial tumors like skin cancer because
it limits dose to normal tissue underneath
xray beams of 1 MV or greater can be classified as
megavoltage
example of a megavoltage machine
cobalt-60
what does linear accelerator mean
charged particles travel in a straight line while they gain energy from an alternating electromagnetic field
clystron
particles travel in a spiral pattern
betatron
particles travel in a circular pattern
accelerator structure
basic element of the linear accelerator
accelerating waveguide
allows electrons produced from a hot cathode to gain energy until they exit the far end of the hollow structure
bending magnet
used in high-energy linear accelerators to bend the electron stream at a variety of angles so that it is pointed at the target
form of radiowave amplifier that greatly multiplies the amount of introduced radiowaves
klystron
microwave frequency needed for linear accelerator operation are
approx. 3 billion cycles per second (300 MHz)^22
major difference between magnetron and klytron
klystron is a linear-beam microwave amplifier requiring an external oscillator or radiofrequency source; the magnetron IS an oscillator and amplifier
first linear accelerator was installed
1952 in Hammersmith Hospital in
London
radiation may only be delivered under the direct supervision of a
radiation oncologist
fractionisation
individual treatment dose
protraction
time period in which the treatment will be given
beam modifiers
devices that change the shape of the treatment field or distribution of the radiation at depth.
point of intersection of three axes of machine rotation (gantry, collimator, and base of couch) and treatment target volumes must be identified
isocenter
volume of tissue exposed to radiation from a single radiation beam
treatment field (also called a portal)
total time during which treatment is protracted
elapsed days
documentation of treatment through radiographic or electronic imaging devices
verification imaging
colonization
involves the reproduction of an infectious microorganism that would result in a detectable immune response
a person who colonizes but is not ill
carrier
pathogenicity
ability of an infectious agent to cause clinical disease
virulence
severity of a clinical disease and is typically expressed in terms of morbidity and mortality
time interval between exposure and the appearance of the first symptom
incubation
