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Table 2 Observer variation for the various CTV to normal tissue interfaces and the two delineation phases.

From: Decreased 3D observer variation with matched CT-MRI, for target delineation in Nasopharynx cancer

Anatomical regions Phase 1 Phase 2
  SD (mm) Agreement (%) SD (mm) Agreement (%)
All regions 4.4 36 3.3 (p = 0.02) 64 (p = 0.003)
Anterior - Air 3.4 62 2.7 (p = 0.01) 79 (p = 0.02)
Dorsal - Bone 3.6 49 2.7 (p = 0.005) 84 (p = 0.005)
Contra lateral 4.2 16 3.5 (p = 0.05) 66 (p = 0.004)
Pterygoid M. 4.3 35 3.1 (p = 0.02) 61 (p = 0.03)
Parapharyngeal 4.4 31 3.3 (p = 0.007) 59 (p = 0.005)
Soft Palate 4.7 37 3.0 (p = 0.005) 67 (p = 0.01)
Sphenoid 5.0 28 4.2 (p = 0.03) 48 (p = 0.01)
Caudal side 7.7 5 3.3 (p = 0.001) 56 (p < 0.001)
  1. Overall observer variation in delineation of the CTV, quadratic mean of the SD of the distance of the delineation to the median surface as measured for each region. Agreement depicts the percentage of the surface for each region on the median surface, where the observers intended to delineate the same anatomical entity. Standard deviations are quadratic averages of patient specific standard deviations.