title: Influence of intravenous contrast agent on dose calculations of intensity modulated radiation therapy plans for head and neck cancer.
abstract: OBJECTIVE
  To evaluate the effect of an intravenous contrast agent (CA) on dose calculations and its clinical significance in intensity modulated radiation therapy (IMRT) plans for head and neck cancer.
  
  
  METHODS
  Fifteen patients with head and neck cancer and involved neck nodes were enrolled. Each patient took two sets of computerized tomography (CT) in the same position before and after intravenous CA injections. Target volumes and organs at risk (OAR) were contoured on the enhanced CT, and then an IMRT plan of nine equiangular beams with a 6 MV X-ray was created. After the fusion of non-enhanced and enhanced CTs, the contours and the IMRT plan created from the enhanced CT were copied and placed to the non-enhanced CT. Doses were calculated again from the non-enhanced CT by the same IMRT plan. The radiation doses calculated from the two sets of CTs were compared with regard to planning target volumes (PTV) and the three OARs, both parotid glands and the spinal cord, by Wilcoxon's signed rank test.
  
  
  RESULTS
  The doses (maximum, mean, and the dose of 95% of PTV received (D95%)) of PTV70 and PTV59.4 calculated from the enhanced CTs were lower than those from the non-enhanced CTs (p < 0.05), but the dose differences were less than 1% compared to the doses calculated from the enhanced CTs. The doses of PTV50.4, parotid glands, and spinal cord were not significantly different between the non-enhanced and enhanced CTs.
  
  
  CONCLUSIONS
  The difference between the doses calculated from the CTs with and without CA enhancement was tolerably small, therefore using intravenous CA could be recommended for the planning CT of head and neck IMRT.
authors.affiliation: Department of Radiation Oncology, College of Medicine, Dong-A University Hospital, Sugu, Busan, South Korea. cymin00@yahoo.co.kr
authors.forename: Youngmin
authors.initials: Y
authors.lastname: Choi
authors.forename: Jeung-Kee
authors.initials: JK
authors.lastname: Kim
authors.forename: Hyung-Sik
authors.initials: HS
authors.lastname: Lee
authors.forename: Won-Joo
authors.initials: WJ
authors.lastname: Hur
authors.forename: Young-Seoub
authors.initials: YS
authors.lastname: Hong
authors.forename: Sungkwang
authors.initials: S
authors.lastname: Park
authors.forename: Kijung
authors.initials: K
authors.lastname: Ahn
authors.forename: Heunglae
authors.initials: H
authors.lastname: Cho
mesh_terms: D000328:Adult; D000368:Aged; D003287:Contrast Media / Q000008:administration & dosage*; D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media