Calculation of photoneutron contamination of Varian linac with new target in tissueequivalent phantom using Monte Carlo simulation

Introduction: in this research, a new material (ti2v0.7cu97.3)was proposed for the target of medical linear accelerators (linacs)to reduce the production of unwanted photoneutrons in theradiotherapy. so, the fluence, dose equivalent and kerma of thephotoneutrons were calculated in a soft tissue phantom.materials and methods: the medical linac was the varian 2100c/d 18 mv, which its tungsten target was replaced with a newmulti-metal target (ti2v0.7cu97.3). desired quantities werecomputed in a icru soft tissue phantom, using the monte carlocode mcnpx (v. 2.6).results: the ratio of the maximums of fluence, kerma, and doseequivalent of photoneutrons along the central axis of the icruphantom with new target rather than tungsten target were 72 %,59 % and 61 %, respectively. average of the ratio of fluence,kerma, and dose equivalent in inner area (distances less than 5cm from central axis) at different depths of the phantom with newtarget rather than tungsten target were 78 %, 70 % and 75 %,respectively. uncertainties at all points were less than 5 %(except for a few points which were less than 10 %).conclusion: this work showed that applying ti2v0.7cu97.3 alloyfor the target of linac, can reduce the produced photoneutrons upto 38 % by an applicable and inexpensive way.