Program Information
3D Dosimetric Evaluation of Breast Cancer Treatments Using 3D Conformational Technique, Direct IMRT and Inverse IMRT in the Presence of a Simulated Respiratory Movement
J Lizar1 , F Brandao2 , V Karina3 , G Flavio4 , O Baffa5 , J Pavoni6*, (1) University of Sao Paulo, Ribeirao Preto, Sao Paulo, (2) Centro de Radioterapia de Sao Carlos, Sao Carlos, Sao Paulo, (3) Centro de Radioterapia de Sao Carlos, Sao Carlos, Sao Paulo, (4) Centro de Radioterapia de Sao Carlos, Sao Carlos, Sao Paulo, (5) Universidade de Sao Paulo, Ribeirao Preto, SP, (6) University of Sao Paulo, Sao Paulo,
Presentations
TU-C1-GePD-T-4 (Tuesday, August 1, 2017) 9:30 AM - 10:00 AM Room: Therapy ePoster Lounge
Purpose: Evaluate the influence of respiration motion on breast cancer treatments tridimensional dose distributions.
Methods: The respiratory motion was simulated by a platform with oscillation amplitudes (0.34 cm, 0.88 cm, and 1.22 cm). Five breast phantoms filled with dosimetric gel (MAGIC-f) were prepared, the first one was used as a reference, the second was irradiated static and the others were irradiated using different amplitudes, calibration vials were also made. 3D-RT, direct IMRT, and inverse IMRT techniques were evaluated, all the treatment plannings were based on the CT of the static phantom filled with water. The phantoms and the calibration vials were irradiated, and the 3D dose distributions were obtained by the R2 relaxometry maps based on MRI acquired with MSE sequence. The respiratory motion influence was evaluated by comparing the relaxometry maps of the moving phantoms with the static one using a 3D gamma analyses (3%/3mm/15% threshold).
Results: For the 3D-RT irradiation the approval in the gamma analyses were 96.44%, 93.23%, and 91.65% respectively for the 0.34; 0.88 and 1.22 cm amplitudes. For the direct IMRT irradiation the approval in the gamma analyses were 98.42%, 95.66%, and 94.31% respectively for the 0.34; 0.88 and 1.22 cm amplitudes. Finally, for the inverse IMRT, the approval in the gamma analyses were 94.49%, 93.51%, and 86.62%.
Conclusion: A low-amplitude respiratory motion, for breast cancer treatments, is not a worrying factor for clinical routine, however, increasing the amplitude increases the dose inhomogeneity and it can affect the dosimetry parameters of the CTV. The dose distribution changes due to the respiratory motion for the inverse IMRT planning, oscillating with 1.22 cm of amplitude, affected the dose distribution in a significant way and less than 90% of points were approved in the gamma analyses.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by grant 2014/003370-6, Sao Paulo Research Foundation (FAPESP)
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