OAR Limits Flashcards
What are the main sources of data for OAR limits?
QUANTEC, Emami et al, Data from clinical trails
What data is given by Emami regarding OARs?
TD50/5 (dose that gives 50%NTCP in 5 years), TD5/5, volume dependences.
What is the advantage of using the recent 2013 Emami data over the original 1991 data?
The new data is more precise than the original; the endpoints are better specified.
What does QUANTEC stand for?
Quantitative Analysis of Normal Tissue Effects in the Clinic
What is the source of QUANTEC?
Int. J. Radiation Oncology Biol. Phys., Vol. 76, No. 3, Supplement
Name 4 of the organ specific QUANTEC papers.
Brain Optic Chiasm Brain stem Spinal cord Ear Parotid Larynx/Pharynx Lung Heart Esophagus Liver Stomach/small bowel Kidney Bladder Rectum Penile Bulb
What is the main outcome from the QUANTEC papers?
Toxicity scoring
What is the general principle of how single numbers are obtained from complicated data to get a toxicity outcome?
3D dose distribution > discard anatomical, physiological and spatial data > compute NTCP (or extract single point//global data)
What data is required to convert published dose limits into local dose limits?
Total dose to OAR
Number of fractions OAR dose is given in
Effective volume of OAR that receives that dose
The α/β ratio used in the analysis in the specific paper/information source being used for your calculation
What is the alpha/beta ratio for a tumour?
10
What is the alpha/beta ratio for an OAR?
3
If using the data in a given paper, what α/β ratio should be used when calculating the BED for your clinical situation when comparing with that paper?
The same as the paper.
What is the equation to calculate EQD2?
D * [ 1 + d / (α/β) ] / [ 1 + 2 / (α/β) ]
Simplified:
D * [ (α/β) + d ] / [ (α/β) + 2 ]
What is the equation for EQDX(α/β)?
D * [ 1 + d / (α/β) ] / [ 1 + X / (α/β) ]
where X is equivalent dose in X Gy per fraction
What is the special case for EQDX(α/β)?
EQD0: sub in 0 to get EQDx = BED
