title: Study of the dosimetric differences between (192)Ir and (60)Co sources of high dose rate brachytherapy for breast interstitial implant.
abstract: OBJECTIVE
  The study intends to compare (192)Ir source against the (60)Co source for interstitial breast metal implant in high dose rate brachytherapy.
  
  
  BACKGROUND
  Few studies have been reported to compare (60)Co and (192)Ir on HDR brachytherapy in gynaecology and prostate cancer and very few with reference to breast cancer.
  
  
  METHODS
  Twenty patients who had undergone interstitial template guided breast implant were treated in HDR (192)Ir brachytherapy unit. Plans were generated substituting (60)Co source without changing the dwell positions and optimization. Cumulative dose volume histograms were compared.
  
  
  RESULTS
  The reference isodose line enclosing CTV (CTVref) and the 2.34% difference seen in the volume enclosed by the reference isodose line (V ref) between the two isotopes show small but statistically significant difference (p < 0.05). In DHI, no difference was observed in the relative dose between the two sources (p = 0.823). The over dose volume index showed 11% difference. The conformity index showed 2.32% difference compared to (192)Ir (p < 0.05). D mean (%) and D max (%) for the heart, ipsilateral lung, ipsilateral ribs, skin presented very small difference. V 5% and V 10% of the heart shows 25% and 32% difference in dose. D 2cc (%) and D 0.1cc (%) for the contralateral breast, contralateral lung and D 2cc (%) of the skin displayed significant difference (p < 0.05). However, D 0.1cc (%) of the skin indicated no noteworthy difference with p = 0.343.
  
  
  CONCLUSIONS
  Based on the 3D dosimetric analysis of patient plans considered in this study, most of the DVH parameters showed statistically significant differences which can be reduced by treatment planning optimization techniques. (60)Co isotope can be used as a viable alternative because of its long half-life, logistic advantages in procurement, infrequent need of source replacement and disposal of used source.
authors.affiliation: Department of Radiotherapy, Regional Cancer Centre, JIPMER, Puducherry, India.
authors.forename: Mourougan
authors.initials: M
authors.lastname: Sinnatamby
authors.affiliation: Department of Medical Physics, Cancer Institute, Adyar, Chennai, India.
authors.forename: Vivekanandan
authors.initials: V
authors.lastname: Nagarajan
authors.affiliation: Department of Radiotherapy, Regional Cancer Centre, JIPMER, Puducherry, India; Department of Oncology, Mahatma Gandhi Medical College and Research Institute, Puducherry, India.
authors.forename: Reddy
authors.initials: R
authors.lastname: Kanipakam Sathyanarayana
authors.affiliation: Department of Radiotherapy, Regional Cancer Centre, JIPMER, Puducherry, India.
authors.forename: Gunaseelan
authors.initials: G
authors.lastname: Karunanidhi
authors.affiliation: Department of Radiotherapy, Regional Cancer Centre, JIPMER, Puducherry, India.
authors.forename: Vivekanandam
authors.initials: V
authors.lastname: Singhavajala
keywords: 192Ir; 60Co; Breast; HDR; Interstitial implant