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Table 2 Lower neck target dose changes (cm3) due to important shifts.

From: Assessment of shoulder position variation and its impact on IMRT and VMAT doses for head and neck cancer

Shift

 

Patient 1

Patient 2

Patient 3

  

V100%

V98%

V95%

V100%

V98%

V95%

V100%

V98%

V95%

IMRT

          

3 mm superior

Target 1

-4

0

0

-4

0

0

0

0

0

 

Target 2

0

0

0

-1

0

0

-1

0

0

5 mm superior

Target 1

-19

-1

0

-14

-2

0

-2

0

0

 

Target 2

-3

0

0

-9

-1

0

-7

0

0

15 mm superior

Target 1

-132

-73

-9

-53

-31

-4

-58

-20

-2

 

Target 2

-29

-5

-1

-64

-35

-12

-77

-25

-7

15 mm posterior

Target 1

-12

0

0

-8

0

0

-4

-1

0

 

Target 2

-5

-1

0

-7

-2

-1

-25

-4

-1

VMAT

      

3 mm superior

Target 1

-4

0

0

-2

-2

0

0

0

0

 

Target 2

-2

0

0

0

0

0

-1

0

0

5 mm superior

Target 1

-24

-3

0

-7

-4

0

0

0

0

 

Target 2

-10

-1

0

-5

0

0

-6

-1

0

15 mm superior

Target 1

-152

-102

-41

-36

-13

-1

-49

-7

0

 

Target 2

-43

-22

-10

-36

-11

0

-65

-29

-7

15 mm posterior

Target 1

-1

0

0

-1

-1

0

0

0

0

 

Target 2

0

0

0

-1

-1

-1

-3

-2

-1

  1. Target 1 = higher dose clinical target volume (CTV); target 2 = lower dose CTV; V100%, V98% and V95% are the volumes covered by the 100%, 98%, and 95% isodose lines, respectively; 15 mm superior shifts show greatest loss of coverage for both IMRT and VMAT, and 15 mm posterior shifts show loss of coverage greater than 4 cm3 for IMRT plans only.