MIDTERM PT. 1 (SIMULATORS) Flashcards
During ___, Px is positioned on the table w/ appropriate treatment accessory and the table is raised and rotated under the gantry.
simulation
The treatment are is determined based upon review of the ff: (simulation)
- any related diagnostic studies
- operative reports
- CT SCAN
- MRI
- isotope studies
- palpation of site
- tumor visualization
is a diagnostic X-ray machine mounted on a rotating gantry that provides geometries identical w/ those found on megavoltage machines
Simulator
can be used in either radiographic fluoroscopic mode to provide diagnostic quality images on film television monitor respectively
Simulator
measurements of absorbed dose resulting from interaction of ionizing radiation with matter
Radiation Dosimetry
The total number of particles/ photons per unit area of the interacting material
Fluence (w)
Absorbed Dose Measurement Methods are:
- Calorimetry
- Fricked Dosimetry
- Film Dosimetry
- Ionization Method
measurement of radiation based on the change in thermal energy per unit mass of the medium
Calorimetry
provide fluoroscopic image
KV
What are the fundamentals of Radiation Dosimetry:
- Radiation Dosimetry
- Fluence
For water, 1 Gy= temp rise of ___ which are measured with sensitive device called ___
2.4x10^ -4 Cal/g
thermistors
based on chemical changes caused by radiation. The chemical radiation dosimeter most commonly used is ____ in which is then oxidized by radiation to _____.
Fricked Dosimetry
- Ferrous Sulfate
- Ferric Sulfate
Ferric ion is measured by absorption dosimetry at ____
224nm-304nm
1Sv= ___ rem
100
1 Gy= ___ rad
100
IR= ___ C/kg (temp rise)
2.58x10 ^-4
1 rad= ____ Gy
10
1 J/kg= ___ 1Gy
1
higher dose received= ___ color
blacker
lower dose received= ____ color
white
measurement of radiation energy based on ion pairs produced in given mass of medium
ionization method
What are the 3 devices for ionization:
- Thimble chamber
- Farmer Chamber
- Markus Chamber
Chamber (s) used for photon beam
Thimble Chamber
Farmer Chamber
used for calibration
ionization devices
effect on a material exposed to radiation. E.G. 180cGy
Dose
radiation dose delivered per unit time. Ex. 180cGy/min for radioactive materials 180 MU/min
Dose Rate
unit used in linac to determine dose. Most are calibrated to 1 MU= 1cGy
Monitor unit
a point in space where the x, y and z intersects
Isocenter
where the LINAC is placed
bunker
a tissue-equivalent material that has: Electron Density, Physical Density, and Atomic Number similar to that of tissue or water.
Bolus
it increases the dose of the skin. Ex. Paraffin Wax, Gauze soaked in water, “Super-Slab”, Elastometric Polymer
Bolus
is intended to compensate for some topographical deficit
compensator
A ___ placed in the tissue deficit of the patient is the simplest way to compensate, but since it diminishes the skin sparing effect, ______ are usually employed
bolus
retracted tissue compensators
used to shield organs at risk, made of lead or Lipowit’s metal (cerrobend)
blocks
Lipowit’s metal (cerrobend) consists of: (elements)
Tin
Bismuth
Lead
Cadmium
Lipowit’s metal (cerroband) elements: (percentage)
Tin __ %
Bismuth __ %
Lead __ %
Cadmium __ %
13.3%
50%
26.7%
10%
the physical density of Lipowit’s metal at __ degrees Celsius is ____ /cm; compared with 11.3 g/cm
20 degrees
9.48/cm
What are the Field Arrangement in EBRT (External Beam Radiation Therapy)
- Single Field
- Parallel Opposed Field
- Multi-Field Arrangement
- Moving Field Technique
the simplest treatment and the dose distribution in tissue are represented in an isodose chart for the energy and field use
Single Field
what Field arrangement in EBRT:
-electron is usually the radiation used to treat shallow tumors, where a rapid drop in dose beyond the 57 depths of the tumor
Single Field
pair of fields directed along the same axis of opposite sides of the treatment volume. Relatively easy to set up and reproduce from day to day. Isodose line is within the entire treatment volume
Parallel Opposed Field
WHAT ARE THE ADVANTAGES OF PARALLEL OPPOSED FIELD?
ADVANTAGES:
-SIMPLICITY AND REPRODUCIBILITY
-HOMOGENOUS DOSE TO TUMOR
-LESS GEOMETRICAL MISS CHANCE
WHAT ARE THE DISADVANTAGES OF PARALLEL OPPOSED FIELD?
DISADVANTAGES:
-EXCESSIVE DOSE TO NORMAL TISSUE CRITICAL ORGANS ABOVE AND BELOW TUMORS
-directed at target volume requires that the beam entrance and exit of each field be aimed at different angles/ segments. Reducing dose to adjacent tissues
Multi-Field Arrangement
______ is the famous multi-field arrangement, often used in pelvic malignancies. Composed of opposed posterior and anterior fields, and opposed right lateral and left lateral fields.
box technique
technique in which the axis of the therapy machine’s rotation, the isocenter is in the center of the target volume
Moving Field Technique
is within the entire treatment volume
isodose line
is in the center of the target volume
isocenter
what field arrangement EBRT:
-Radiation source is moved around the Px through are, often in a complete circle. It yields a high dose in the target volume where the dose outside falls off rapidly
Moving Field Technique
what technique is used for pelvis: minimizes dose surrounding the tissue
box technique
