algorithims Flashcards
algorithim for treatment planning is
modelling to see where the scatter is gonna go.
Pencil beam is used for treating
prostate tumours and centralized tumours, but not effectives for tumour close to the lung.
calculation of pencil beam
easy to calculate but may overestimate scatter in regions with air and underestimate it in real life.
pencil beam is made up of
very small dose kernals that are made up at each point
what is the mayneord factor
correction factor
used to account the variation of scatter+attenuation in different tissues.
used to calculate the am of dose delivered to the tumour and surrounding tissues
the problem with precomputed pencil beams
dont take into account the patients individual anatomy.
the scattering ray are computed with water around it , but sometimes the water doesnt exist.
the montecarlo algorithim
Tracks INDIVIDUAL PARTICLES and their dose deposition into voxels.
very accurate.
The gold standard
monte carlo limitations
-computationally intensive
-time consuming to run.
-tf often used in combination w other modeling techniques
AAA algorithim.
what is it made up of
- The beam is split into beamlets.
- Each component is modelled separately then combined later (side sctatter modelled and then added to pencil beam)
AAA algoritim beamlets are based on
-Monte -carlo scatter
-kernals for pencil beams in water
-the kernals are scaled according to a CT number
-they are then combined and converted to dose
AAA is considered more
accurate than pencil beam ((Particularly at in homogeneities)
limitaions of pencil beam
problems with inhomogeneities particularly at edge of the beam
