Surface optimization technique for MammoSite breast brachytherapy applicator.
OBJECTIVE
We present a technique to optimize the dwell times and positions of a high-dose-rate (192)Ir source using the MammoSite breast brachytherapy applicator. The surface optimization method used multiple dwell positions and optimization points to conform the 100% isodose line to the surface of the planning target volume (PTV).


METHODS
The study population consisted of 20 patients treated using the MammoSite device between October 2002 and February 2004. Treatment was delivered in 10 fractions of 3.4 Gy/fraction, twice daily, with a minimum of 6 h between fractions. The treatment of each patient was planned using three optimization techniques. The dosimetric characteristics of the single-point, six-point, and surface optimization techniques were compared.


RESULTS
The surface optimization technique increased the PTV coverage compared with the single- and six-point methods (mean percentage of PTV receiving 100% of the prescription dose was 94%, 85%, and 91%, respectively). The surface method, single-point, and six-point method had a mean dose homogeneity index of 0.62, 0.68, and 0.63 and a mean full width at half maximum value of 189, 190, and 192 cGy/fraction, respectively.


CONCLUSIONS
The surface technique provided greater coverage of the PTV than did the single- and six-point methods. Using the FWHM method, the surface, single-, and six-point techniques resulted in equivalent dose homogeneity.
Kirk
Michael
M
Department of Radiation Oncology, Rush University Medical Center, Chicago, IL 60612, USA. Michael_C_Kirk@rush.edu
Hsi
Wen Chien
WC
Dickler
Adam
A
Chu
James
J
Dowlatshahi
Kambiz
K
Francescatti
Darius
D
Nguyen
Cam
C
D001918:Brachytherapy / Q000295:instrumentation*; D001943:Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D005260:Female; D006801:Humans; D007496:Iridium Radioisotopes / Q000627:therapeutic use*; D015412:Mastectomy, Segmental; D011879:Radiotherapy Dosage
D007496:Iridium Radioisotopes