Dose modeling of noninvasive image-guided breast brachytherapy in comparison to electron beam boost and three-dimensional conformal accelerated partial breast irradiation.
OBJECTIVE
To perform dose modeling of a noninvasive image-guided breast brachytherapy (NIIGBB) for comparison to electrons and 3DCRT.


METHODS
The novel technology used in this study is a mammography-based, noninvasive breast brachytherapy system whereby the treatment applicators are centered on the planning target volume (PTV) to direct (192)Ir emissions along orthogonal axes. To date, three-dimensional dose modeling of NIIGBB has not been possible because of the limitations of conventional treatment planning systems (TPS) to model variable tissue deformation associated with breast compression. In this study, the TPS was adapted such that the NIIGBB dose distributions were modeled as a virtual point source. This dose calculation technique was applied to CT data from 8 patients imaged with the breast compressed between parallel plates in the cranial-caudal and medial-lateral axes. A dose-volume comparison was performed to simulated electron boost and 3DCRT APBI.


RESULTS
The NIIGBB PTV was significantly reduced as compared with both electrons and 3DCRT. Electron boost plans had a lower D(min) than the NIIGBB technique but higher V(100), D(90), and D(50). With regard to PTV coverage for APBI, the only significant differences were minimally higher D(90), D(100), V(80), and V(90), with 3DCRT and D(max) with NIIGBB. The NIIGBB technique, as compared with electrons and 3D-CRT, achieved a lower maximum dose to skin (60% and 10%, respectively) and chest wall/lung (70-90%).


CONCLUSIONS
NIIGBB achieves a PTV that is smaller than electron beam and 3DCRT techniques. This results in significant normal tissue sparing while maintaining dosimetric benchmarks to the target tissue.
Sioshansi
Shirin
S
Department of Radiation Oncology, Tufts Medical Center, Tufts University School of Medicine, Boston, MA 02111, USA. ssioshansi@tuftsmedicalcenter.org
Rivard
Mark J
MJ
Hiatt
Jessica R
JR
Hurley
Amanda A
AA
Lee
Yoojin
Y
Wazer
David E
DE
D000465:Algorithms; D001918:Brachytherapy / Q000379:methods*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D004583:Electrons / Q000627:therapeutic use; D005260:Female; D006801:Humans; D007496:Iridium Radioisotopes; D008327:Mammography / Q000295:instrumentation / Q000379:methods; D018579:Patient Selection; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods*; D047368:Tumor Burden
D007496:Iridium Radioisotopes