title: [Measurement of the imaging dose for head and neck cancer by different image-guided methods].
abstract: OBJECTIVE
  To measure the imaging dose in the head phantom by different image-guided methods.
  
  
  METHODS
  The imaging dose was measured in a cylindrical phantom on a Varian Clinac iX linear accelerator equipped with EPID, OBI, CBCT using a PTW 0.6 cc ion chamber with UNIDOS E dosimeter. 2D images were acquired by two perpendicular fields (0 degrees & 270 degrees), and the 3D images by CBCT.
  
  
  RESULTS
  The 2D imaging average dose for OBI (KV X-ray) was 0.74 mGy in the head phantom. It was significantly lower than 90.93 mGy for EPID (MV X-ray) and the image quality was better. For a standard CBCT (KV X-ray), the imaging average dose was 4.77 mGy. For a low dose mode, the imaging dose was 50% of the standard mode. Moreover, 3D images could match accurately.
  
  
  CONCLUSIONS
  For the OBI system, the imaging dose is lower and image quality is better than EPID. The 3D image-guided method for CBCT is better than 2D and is also safe for daily position verification. Therefore, during treatment positioning, the appropriate image-guide methods and scanning parameters can effectively reduce the additional dose to the patients.
authors.affiliation: Radiotherapy Dept., The PLA 309th Hospital, Beijing, 100091, China. zyh309@yahoo.com.cn
authors.forename: Yuhai
authors.initials: Y
authors.lastname: Zhang
authors.forename: Huosheng
authors.initials: H
authors.lastname: Xia
authors.forename: Yang
authors.initials: Y
authors.lastname: Gao
mesh_terms: D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*