ESTRO 2024 - Abstract Book

S4952

Physics - Quality assurance and auditing

ESTRO 2024

Dose distributions and clinically relevant DVH-derived parameters were computed for all treatment plans. Differences in DVH parameters calculated as the variation between plans with and without treatment delivery errors, were quantified.

Results:

Fallback plans with similar dosimetric characteristics were successfully created across the three platforms for the three head-and-neck plans. Differences in dose to 98 percent (D98) of the target volumes, and mean dose (Dmean) to organs at risk (OAR) are presented in Table 1.

Relative error [%]

Original plan

Fallback plan

Targets

D98 0.35 -0.57

OARs

Dmean

PTV1 PTV2

Brainstem

-2.10 -0.05

TrueBeam Millenium

Spinal cord

P1

(Versa

Synergy)

PTV1 PTV2

0.32

Brainstem

-3.47 -0.48

TrueBeam HD

-0.43

Spinal cord

PTV1 PTV2

-2.58 -3.58

Brainstem

-1.08 -4.52

TrueBeam Millenium

Spinal cord

P2 (TrueBeam HD)

PTV1 PTV2

-3.83 -4.53

Brainstem

-0.85

Versa Synergy

Spinal cord

1.35

PTV1 PTV2

-3.22 -2.12

Brainstem

-1.42 -0.65

TrueBeam Millenium

Spinal cord

P3 (TrueBeam HD)

PTV1 PTV2

-1.9

Brainstem

-1.93 -0.48

Versa Synergy

-0.46

Spinal cord

Fallback plans presented slightly less target conformality and similar protection for OARs compared to the original plans.

Visual inspection of DVHs revealed that target conformality was very consistent among fallback plans.

Introduced treatment delivery errors resulted in consistent differences in DVH parameters for all treatment machines for all patients (Figure 1).