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Table 2 Dose-volume constraints for PTVs and OARs used for optimization

From: Dosimetric comparison between helical tomotherapy and volumetric modulated arc-therapy for non-anaplastic thyroid cancer treatment

  VMAT Helical tomotherapy
Structures Optimization objectives Optimization priorities Optimization objectives Optimization priorities
PTV 63 Gy D50% = 63 Gy Very High Dmin = 63 Gy Very high
Dmin > 100% Dpresc HR Very High D50% = 63 Gy Very high
Dmax < 102% Dpresc HR Very High Dmax = 63 Gy Very high
PTV 54 Gy - - Dmin = 54 Gy High
D50% = 54 Gy High
Dmax = 54 Gy High
PTV 54 Gy – PTV 63 Gy Dmin > 100%Dpresc LR Very High - -
Dmax < 95% Dpresc HR High   
D5% < 105%Dpresc LR High   
PTV 54 Gy –(PTV 63 Gy +1 cm) Dmax < 95%Dpresc LR High - -
PRV medullary canal Dmax < 35Gy High Dmax < 30 Gy High
D2% < 33 Gy   D2% < 28Gy  
Ipsilateral parotid gland - PTVs V10Gy < 45% Medium V15Gy < 45% Medium
V25Gy < 30%   V30Gy < 30%  
V40Gy < 15%   V45Gy < 15%  
   Dmax < 50Gy  
Controlateral parotid gland - PTVs V10Gy < 45% High V15Gy < 45% High
V25Gy < 30%   V30Gy < 30%  
V40Gy < 15%   V45Gy < 15%  
   Dmax < 50Gy  
Mandible - PTVs D5% < 55Gy Medium Dmax < 65Gy Medium
D50% < 30Gy   D5% < 55Gy  
   D50% < 30Gy  
Larynx - PTVs Dmax < 55Gy Medium Dmax < 55Gy Medium
D50% < 30Gy   D50% < 30Gy  
D95% < 15Gy   D95% < 15Gy  
Oral cavity - PTVs Dmax < 55Gy Medium Dmax < 55Gy Medium
D50% < 30Gy   D50% < 30Gy  
D95% < 15Gy   D95% < 15Gy  
Ipsilateral sub-maxillary gland - PTVs D30% < 50Gy Medium Dmax < 55Gy Medium
D50% < 30Gy   D30% < 50Gy  
   D50% < 30Gy  
Controlateral sub-maxillary gland - PTVs D30% < 50Gy High Dmax < 55Gy High
D50% < 30Gy   D30% < 50Gy  
   D50% < 30Gy  
  1. Dx% = dose received by x% of structure volume; VxGy = percent structure volume of xGy.
  2. DprescHR = prescribed dose on high risk PTV = 63 Gy; Dpresc LR = prescribed dose on low risk PTV =54 Gy.