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SU‐FF‐T‐396: Stereotactic Peripherial Brachytherapy and Image Guidance for the Breast
Author(s) -
Rivard MJ,
Bricault RJ,
Melhus CS,
Sioshansi P
Publication year - 2006
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2241315
Subject(s) - lumpectomy , brachytherapy , imaging phantom , dosimetry , radiation treatment planning , nuclear medicine , radiosurgery , medicine , pinnacle , breast cancer , radiation therapy , radiology , mastectomy , cancer
Purpose: Breast brachytherapy may be applied peripherally without piercing the skin as currently performed with interstitial and MammoSite applications. By virtue of being a protruding and deformable organ, the breast lends itself to peripheral brachytherapy by non‐invasive applicators. A delivery system was made (Advanced Radiation Therapy, Billerica, MA) to implement this developmental treatment modality using real‐time mammographic image guidance for stereotactic applicator positioning and CTV localization. In this design, therapeutic dose to the lumpectomy cavity is delivered by externally placing opposing plaque‐like applicators at multiple orientations to provide conformity while not exceeding the skin toxicity threshold. An initial assessment of this system was performed to determine clinical feasibility. Materials & Methods: The applicator geometry comprises two curved plates which slightly compress the breast to minimize slab thickness irradiated by the parallel‐opposed plaque. Within the applicator are a series of parallel catheters spaced 1 cm apart. For a thickness of 6 cm, the breast geometry and applicators were simulated using analytical (Pinnacle 3 treatment planning system) and Monte Carlo (MCNP v5) techniques. A breast phantom was used for CT‐based treatment planning; however, standard‐of‐care for brachytherapy dosimetry algorithms assume an infinite water phantom. CTV ellipsoids ranged from 2×4×4 cm 3 to 3×6×6 cm 3 . Sources were positioned within the catheters to create a circular loading region (5 to 9 cm diam.) towards providing uniform CTV coverage. Dose homogeneity index (DHI) was determined for the skin. Results & Discussion: Average ratio of skin‐to‐tumor dose was < 0.9. Pinnacle and MCNP results indicated that DHI ∼ unity for the CTVs studied. Dose to lungs, heart, and other critical organs was typically < 2%. These simulation results suggest that this technique may be an attractive APBI option. Conflict of Interest Statement: Advanced Radiation Therapy provided the applicator used in this study.