ESTRO 2024 - Abstract Book

S3728

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2024

In contrast, for PTVs with more intricate shapes, where the clinical target volume (CTV) encompasses the pedicles and/or transverse processes, the coverage of PTV_Prescribe is markedly influenced by the collimator angle. Notably, variations as high as 15.2% were observed with different collimator angles, as illustrated in Table 1.

Table 1: Average, minimum and maximum value of V100% to PTV_Prescribe

V 100%

Case1

Case2

Case3

Case4

Case5

Case6

Case7

Case8

Case9

Case10

AVG

99.41

98.51

92.98

97.44

98.84

98.09

98.07

96.25

96.25

96.38

Min

98.96

97.62

82.09

95.30

96.40

95.44

93.05

93.96

93.96

88.54

Max

99.74

98.89

97.31

98.80

98.80

99.70

99.24

98.2

98.20

98.68

While we couldn't identify a single collimator angle that consistently provided optimal coverage for all plans due to the diversity in target volume shapes, it is evident that optimizing the collimator angle is crucial for achieving best balance between PTV coverage and number of MU.

Based on our findings, collimator angles that strike this balance best are 30°, 45°, and 60°. Although a 15° collimator angle presented the least variation in terms of V100%, it was associated with a higher number of MU.

Additional research is required to determine whether we can pinpoint the ideal collimator angle for targets with similar shapes and locations. In the meantime, we recommend considering collimator angles within the range of 30° to 60°, as this range consistently offered excellent PTV coverage with reduced variability.

Keywords: Spine SABR, Collimator angle, Dosimetric effects

References:

[1] Jaap D. Zindler, Charles R. Thomas, Stephen M. Hahn, Aswin L. Hoffmann, Esther G.C. Troost, Philippe Lambin, Increasing the Therapeutic Ratio of Stereotactic Ablative Radiotherapy by Individualized Isotoxic Dose Prescription, JNCI: Journal of the National Cancer Institute, Volume 108, Issue 2, February 2016, djv305, https://doi.org/10.1093/jnci/djv305 [2] Stereotactic Ablative Body Radiation Therapy (SABR): A Resource, version 6.1. UK SABR Consortium; 2019. [Available from: https://www.sabr.org.uk/wp-content/uploads/2019/04/SABRconsortium-guidelines-2019 v6.1.0.pdf]

3110

Mini-Oral

A randomized safety trial on motion sickness induced by dynamic table rotation in healthy volunteers

Paul-Henry Mackeprang 1 , Jenny Bertholet 1 , Claas Wessels 2 , Daniel M Aebersold 1 , Michael K Fix 1 , Peter Manser 1