ESTRO 2024 - Abstract Book

S3184

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

Results:

The ranges and mean of overall volumetric gamma indexes obtained:

• GP (Γ(2mm,3%))= [86.9% - 99.3%], mean = 96%. → merge: [94.4% - 99.7%], mean = 98%. • GP (Γ(3mm,2%))= [89.7% - 99.4%] , mean = 96%. → merge: [95.0% - 99.7%], mean = 98%.

Passing rates obtained according to relative dose levels are in Figure 2.

Figure 2.

Conclusion:

• When switching from gamma criterion Γ(2mm,3%) to Γ(3mm,2%), there is an appreciated improvement (p<0.001), especially at the relative high dose levels (80%-95%), which present the worse passing rates. • Using the merge function, the overall passing rates improve in both gamma index criteria by 2% on average. • The lowest passing rates correspond to dose levels between (80%-95%), which indicates that it is necessary a deeper analysis of the possible causes that might affect the higher doses. These levels are particularly improved by applying the merge tool. • The merge tool makes it possible to better discern which plans do or do not meet the gamma index criterion before clinical treatment by increasing the spatial resolution of a matrix detector, with the disadvantage that it takes twice as long. • The Γ(3mm,2%) criterion offers better results than the Γ(2mm,3%) criterion. The improvement is remarkable when narrowing in dose rather than in spatial resolution, limited by the own matrix1500 detector. • Correctly discerning whether a pre-treatment verification plan meets or not the quality criterion translates to a reduced workload and an improved treatment quality.