monte carlo dose calculation of 90 sr/ 90 y source in water phantom

introduction:  90 sr/ 90 y source  has  been  used  for  the  intravascular  brachytherapy  to  prevent  coronary  restenosis in the patients who have undergone angioplasty. the aim of this research is to determine the  dose distribution of  90 sr/ 90 y source in a water phantom.  materials  and  methods:  in  the  present  work,  mcnp  code  has  been  applied  to  calculate  the  dose  distribution around a 3 cm length of  90 sr/ 90 y source in a 30×30×30 cm 3 water phantom. also, the exact  geometry  of  the  source  has  been  used  in  this  simulation.  tally  *f8:e  which  is  suitable  for  beta  ray  dosimetry has been evaluated with less than %5 relative error in a sphere having 0.2 mm radius.  results:  the  isodose  curve  for  10,  20,  40,  and  90%  depth  dose  (pdd)  were  derived  based  on  the  calculated dose curves along the parallel and perpendicular axis to the source.  discussion  and  conclusion:  the  results  obtained  in  this  work  are  in  a  good  agreement  with  the  experimental  result  published  by  buckley  et  al.  and  the  international  atomic  energy  agency  (iaea)  report  in  a  water  phantom.    therefore,  the  result  of  this  research  can  be  used  in  the  intravascular  brachytherapy.