Dose Course 2018_Flipping book
What’s the fuzz about dose to medium or dose to water? Macro and micro targets!
Issues
Macro scale: localized targets, geometrically formalized as GTV,CTV,ITV and PTV OAR identified for avoidance elemental compositions and densities assigned as averages over cm 3 scale Micro scale: the cell nucleus DNA is the primary site of radiation damage cell diameter varies 5-100 m m cell nucleus diameter 2-10 m m, DNA double helix 2 nm
elemental compositions and densities can vary a lot over nm to m m scales cavity theory can be used for dose ratios over short range media variations
The fuzz:
is water a good standard surrogate medium for cell nucleus? “wrong” cavity theory often used, depends on cavity size and radiation quality cell nucleus size confused with voxel size and/or detector size some common scaling “standards” proved to yield non-expected results no formalized recommendations to follow
A relief:
for MV photons large differences only occur for cell nuclei embedded in bone
From Anders Ahnesjö
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