Determination of Interfraction Variation in Interstitial High dose Rate Brachytherapy

The positional stability of the catheters and the resultant dosimetric variation over a period of time is studied and presented. The ability of brachytherapy to deliver high radiation doses over a short time period means patients can complete treatment in days rather than weeks required for EBRT. Brachytherapy is generally well tolerated with a good toxicity profile for many of its applications, largely due to its tissue sparing approach. The remote after-loading HDR Brachytherapy treatment unit Gamma Med iX plus (Varian Medical Systems, Palo Alto, CA) or Microselectron HDRV3 (Nucletron, BV) using single sealed Iridium 192 radioactive source was used for treatment and for treatment planning, Eclipse (Varian Medical Systems, Palo Alto, CA) or Oncentra Master plan (Nucletron, BV) was used. Interfraction errors occur frequently in interstitial HDR brachytherapy. If no action is taken it will result in a significant risk of geometrical miss and overdose to the organs at risk. The effect of interfraction variation also depends on the fractionation schedule of the brachytherapy treatment. It is recommended to complete the treatment within 5 days. For cancer cervix (MUPIT) interstitial implant planning before each fraction is recommended.