Effects of Geometrical Uncertainties on Whole Breast Radiotherapy: A Comparison of Four Different Techniques

다국어 초록 (Multilingual Abstract)

Purpose: The purpose of this study was to quantify the targetcoverage, homogeneity, and robustness of the dose distributionsagainst geometrical uncertainties associated with fourwhole breast radiotherapy techniques. Methods: The study wasbased on the planning-computed tomography-datasets of 20patients who underwent whole breast radiotherapy. A total offour treatment plans (wedge, field-in-field [FIF], hybrid intensitymodulatedradiotherapy [IMRT], and full IMRT) were created foreach patient. The hybrid IMRT plans comprised two opposedtangential open beams plus two IMRT beams. Setup errors weresimulated by moving the beam isocenters by 5 mm in the anterioror posterior direction. Results: With the original plan, thewedge technique yielded a high volume receiving ≥107% of theprescription dose (V107; 7.5%±4.2%), whereas the other threetechniques yielded excellent target coverage and homogeneity.
A 5 mm anterior displacement caused a large and significant increasein the V107 (+5.2%±4.1%, p<0.01) with the FIF plan, butnot with the hybrid IMRT (+0.4%±1.2%, p=0.11) or full IMRT(+0.7%±1.8%, p=0.10) plan. A 5-mm posterior displacementcaused a large decrease in the V95 with the hybrid IMRT (-2.5%±3.7%, p<0.01) and full IMRT (-4.3%±5.1%, p<0.01) plans, butnot with the FIF plan (+0.1%±0.7%, p=0.74). The decrease inV95 was significantly smaller with the hybrid IMRT plan than withthe full IMRT plan (p<0.01). Conclusion: The FIF, hybrid IMRT,and full IMRT plans offered excellent target coverage and homogeneity.
Hybrid IMRT provided better robustness against geometricaluncertainties than full IMRT, whereas FIF provided comparablerobustness to that of hybrid IMRT

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