Advanced Dose Calculations Flashcards
What are the two components of radiation dose?
Primary Dose and Scatter Dose
Ratio of the scattered dose at a given point in a medium to the dose in air at the same point
Scatter-Air Ratio (SAR)
How can SAR be calculated?
using the difference between the TAR for the given field and TAR for 0x0cm field
___ - ____ = SAR
TAR(given fs) - TAR (0x0 fs) = SAR
What factors is SAR dependent on? Independent of?
Dependent on Depth, FS and BE and independent on SSD
What calculations can be used for irregular fields?
Clarkson Calculations
Scatter Calculations
Scatter= cGy/MU x SAR x MU x Attenuation Factors
Primary Dose Calculations
Primary= MU x cGy/MU x TAR0 x Attenuation Factor x OAR x Block Transmission Factor
Block transmission for 5 HVL block
3.125%
How would you calculation the dose outside the field?
Calculation the SAR intersection the fields, but divided by the total segments amount
ratio of dose at a depth, compared to the dose at Dmax, expressed in a percent
Percentage Depth Dose
PDD= ____ / ____
PDD at Depth / PDD at Dmax
Ratio of Dose in a phantom compared to dose in a free space at the same point
Tissue-Air Ratio
Ratio of dose at a given point inside a phantom, compared to dose at same point and distance at a reference depth
Tissue-Phantom Ratio
Ratio of dose at a given point in a phantom to the dose at Dmax (Special case of TPR, in which depth is at Dmax)
Tissue-Maximum Ratio
