ESTRO 2024 - Abstract Book

S3582

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

ESTRO 2024

evaluated the dosimetric parameters between the plans, including the planning target volume (PTV) uniformity with the homogeneity index D5-95%, the median doses of OAR (rectum, bladder, femoral heads) and the spread of medium (V15Gy) and low (V5Gy) dose within body.

Results:

Results show that partial-arcs significantly (p<0.005 [paired-samples t-test]) reduced the mean treatment time by 46±5% (139±10 s vs 74±4 s) and decreased the monitor unit count by 14±11% (1003±114 MUs vs 854±40 MUs, [p<0.005]). Partial-arc plans had 56%±4% (685°±25° vs 299°±23°) shorter total arc length compared to full-arc plans. Partial-arc plans presented comparable PTV coverage (uniformity [D5%-95%]: 5.2%±0.9% vs 4.0%±1.0%, p<0.005) and OAR sparing – see Figure 1 for full results. Rectum and bladder median dose difference was on average 1.8±3.3 Gy (p=0.06) and 0.1±0.4 Gy (p=0.44) smaller in partial-arc plans, respectively. Femoral heads presented on average a minor increase in median dose: 0.6±1.9 Gy (p=0.12) higher dose in partial-arc plans. Partial-arc plans had in average a 20±13 % larger medium dose spread with V15Gy (7.6±1.6 % and 6.5±1.7 %, [p<0.005]) and moderately reduced spread of the small dose: V5Gy 2±3% (17±3 % and 18±3 % [p=0.02]) - see Figure 2.

Conclusion: