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A Comparative Dosimetric Study of High Definition (HD120) and Millennium (M120) Multi Leaf Collimators for Left-Sided Breast Cancer Using Four Different Radiotherapy Techniques

V Mhatre*, S Pilakkal , V Manik , P Chadha , K Talpatra , KOKILABEN DHIRUBHAI AMBANI HOSPITAL, Mumbai, Maharashtra


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: Normal tissue toxicity remains a major concern while treating left sided breast. In this study, we investigate the dosimetric outcome of four different radiotherapy techniques using Millennium MLC (M120) and High Definition MLC (HD120).

Methods: Eight patients with left sided breast cancer previously treated with 3DCRT with tangential wedge fields with 5 mm width Millennium 120 MLC (M120) were chosen for this planning study. The target volume was delineated as per RTOG consensus guidelines (RTOG1005) protocol. All the plans were created for M120 and HD120 with identical planning parameters. For each patients four different radiotherapy technique treatment plans, 1) conventional tangential wedge-based fields (TW); 2) field-in-field (FIF) technique; 3) tangential inverse IMRT (T-IMRT); 4) multi-field IMRT (M-IMRT) were created on Eclipse Planning System(v13.6) using anisotropic analytical algorithm(AAA) for 6 MV X-rays. The PTV dose was prescribed 50Gy and V47.5≥95%.Target coverage, conformity index, homogeneity index , and mean dose to heart, left lung, left anterior descending artery (LAD), contra lateral right breast and right lung were compared between the eight plans .Same dose constraint was used for all eight plans.

Results: Target coverage was adequate with both M120 and HD120. The HD120 showed a decreased Heart and LAD Mean dose compared to M120 for all the techniques

Conclusion: Data derived from the present comparative assessment suggest that dosimetric merit of 2.5mm over 5mmMLC system is minimal for target coverage but have a slight advantage in OAR doses. However, the clinical significance of these results warrants further investigation.


Breast, MLC


Not Applicable / None Entered.

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