ESTRO 2021 Abstract Book

S796

ESTRO 2021

not clearly visible on the b500 image due to very small residual volume (<1ccm for GTV-P and GTV-N). These time points were therefor excluded from the analysis.

Table1: mean changes of volume and ADC for GTV-P and GTV-N from baseline to last week of therapy

GTV-P

GTV-N

Decrease of Volume [%]

Mean ADC change [%]

Decrease of Volume [%]

Mean ADC change [%]

pat#1 80.2

36.0

66.9

6.5

pat#2 60.4

44.3

34.8

20.3

pat#3 82.5

11.2

75.2

15.0

pat#4 70.5

60.5

57.3

5.9

pat#5 82.3

72.6

n.a.

n.a.

pat#6 79.3

69.5

75.7

25.1

media n

79.7

52.4

66.9

15.0

Conclusion This data shows early clinical experience to collect serial DWI for HNC patients treated on a 1.5 T MRL during the course of RT. Treatment response by means of ADC can be monitored and offers the potential for future biological response adaptive interventions. Voxel-based ADC-analysis and assessment of individual LN as well as expansion of the cohort are ongoing.