ESTRO 2022 - Abstract Book

S1552

Abstract book

ESTRO 2022

submandibular and parotid glands. Bland-Altman analysis with limits of agreement (LoA, ± 1.96 · standard deviation) was performed to investigate reproducibility.

Table 1: Details of imaging protocols

MRL

DS

TE/TR [ms]

68/4811

44/10800

Acquisition voxel size [mm ³ ] 3x3x4

3x3.3x5

Acquisition matrix

132x134x25

128x76x24

Flip angle

90°

90°

Bandwidth [Hz/px] 2298 b-values (averages) [s/mm ² ] 150 (5), 500 (8) 200 (6), 500 (7), 1000 (10) 1930

Results A total of 13 measurements were available for analysis. Mean average ADC values for GTV, submandibular and parotid glands for the MRL were 1251, 1114 and 789 · 10 -6 mm 2 /s and for the DS those were 1483, 1347 and 1038 · 10 -6 mm 2 /s. Figure 1 shows Bland-Altman plots for GTV, submandibular and parotid glands. Mean absolute ADC differences ± LoA for GTV, submandibular and parotid glands were 232±430, 234±351 and 249±302 · 10 -6 mm 2 /s. Accordingly, mean relative differences resulted in 15%, 17% and 24%, respectively

.

Conclusion This study showed good overall reproducibility of ADC measured at the MRL with respect to a DS. However, comparison of ADC values showed an underestimation of the ADC for the MRL. This shift must be considered when results from DS are translated to the MRL and vice versa. Further validation with more patients is necessary to confirm these results.

PO-1751 Integration of R2* mapping in daily prostate MR-Linac workflow for hypoxia characterisation

W. Bano 1 , K. Sritharan 2 , J. Chick 1 , G. Smith 3 , A. Tree 2 , U. Oelfke 4 , A. Wetscherek 4

1 The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, Joint Department of Physics, London, United Kingdom; 2 The Royal Marsden NHS Foundation Trust and The Institute of Cancer Research, Department of Radiotherapy, London, United Kingdom; 3 The Royal Marsden NHS Foundation Trust, Radiotherapy, London, United Kingdom; 4 The Institute of Cancer Research, and The Royal Marsden NHS Foundation Trust, Joint Department of Physics, London, United Kingdom

Purpose or Objective