Stereotac(c  Radiosurgery  (Rota(on  #  9)  

Mentor:  Edward  C  Pennington  (01/19/2010  –  03/05/2010)  

By    

Vibha  Chaswal,  Ph.D.  

Contents  

Ac(vi(es    

•  Es(ma(on  of  mechanical  accuracy  of  the  floor-­‐stand  

•  End-­‐to-­‐end    process  tes(ng:  Absolute  phantom  based  QA:  Frame-­‐based  and  Frame-­‐less  SRS  

•  Small  field  dosimetry  measurements:  TMRs,  output  factors,  profiles,  off-­‐axis  factors  

•  CT  to  MRI    image  registra(on  •  SRS  treatment  planning  •  Pre-­‐treatment  SRS  floor-­‐stand  QA  •  Par(cipa(on  in  treatment  delivery    

Mechanical  QA:  Floor-­‐stand  

End-­‐to-­‐End:  CT-­‐Localiza1on  

(Frame-­‐based)  

TILT  and  SPIN  Adjusted  on  Frame.  CT-­‐Localiza(on  with  (lt  and  spin  correc(on  

Max  error:  Ax  (0.4  mm)  Lat  (0.3  mm)  A-­‐P  (0.5  mm)  3D  (0.6  mm)  

Frame-­‐based  End-­‐to-­‐End  tes(ng:  Floor-­‐stand    

isocentric  localiza(on    

Frame-­‐Less  SRS    End-­‐to-­‐End  isocentric  localiza(on  :  

SRS  Commissioning:  Small  field  dosimetry  TMR  and  Out-­‐put  measurement  set-­‐up  

NOT  A  TRIVIAL  AFFAIR  !!!!!!!!!  

~  3.5  %  lower  TMR  And  dmax  ~  1  cm  

Re-­‐measurement  of  TMRs    Stereotac1c    Chamber-­‐valida1on  

TMR’s  s(ll  off    but  d-­‐max  depth  =  1.5  cm  

OUT-­‐PUT  Factor  measurements  

Off-­‐Axis-­‐Factors  

Recommenda(on  of  independent  Physics  check  on  TMR  measurements  

of  small  fields.  

Iden(fied  pit-­‐falls:  SRS  stereotac(c  chamber  response  with  depth  L-­‐R  (lt  on  the  SRS  phantom  base  (resolved  with  a  (ssue  propped  at  led  side)  

Par(cipa(on  and  observa(on  in  SRS  work-­‐flow:  

Iden(fica(on  of  Physics  QA  at  all  steps  

ThankYou!!!!!