Development of A Head Docking Device for Linac-based Stereotactic Radiosurgery System to be Installed on Neptun 10 PC Linac

Introduction:  Stereotactic  radiosurgery  is  a  technique  for  the  treatment  of  intracranial  lesions  with  highly  collimated  x-ray  beam.  Linac-based  radiosurgery  is  currently  performed  by  two  techniques:  couch or pedestal mounted. In the first technique, a device is required to affix patient's head to a couch  and  moreover  to  translate  it  accurately.  Structure  of  such  a  device  constructed  by  the  authors  in  addition to the acceptance test which was performed to evaluate the device has been described in this  article.  Materials and Methods:  A head docking device has been designed and constructed according to the  geometry of linac's couch and desired functions. The device is completely made from aluminum and  consists  of  four  major  components:  attachment  bar,  lower  structure  with  four  movements,  upper  structure with two movements equipped with a lock, two handles and a mounting ring for stereotactic  frame. Translating accuracy, mechanical stability and isocentric accuracy were assessed in the frame of  acceptance test.  Results:  Translating  accuracy,  mechanical  stability  and  isocentric  accuracy  within  95%  confidence  intervals were found to be 1, 1.64 and 3.2 mm, respectively.  Discussion and Conclusion: According to AAPM report no.54 recommendation head docking device  should translate head with accuracy of 1 mm, the property which was met by the constructed device.  Moreover  considering  the  measured  isocentric  accuracy,  encompassing  mechanical  stability,  constructed device can confidently be used in stereotactic treatment.