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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.