title: The effect of a contrast agent on proton beam range in radiotherapy planning using computed tomography for patients with locoregionally advanced lung cancer.
abstract: OBJECTIVE
  We evaluated the effect of a contrast agent (CA) on proton beam range in a treatment planning system (TPS) for patients with locoregionally advanced lung cancer.
  
  
  METHODS
  Two sets of computed tomography (CT) images (with and without CA) were obtained from 20 patients with lung cancer. Because the increase in Hounsfield unit (∆HU) value of the heart and great vessels due to the effect of CA is most prominent among thoracic structures, to evaluate the effect of CA on proton beam range in the TPS, we compared the calculated distal ranges in the plan with CA-enhanced CT with those with corrected CT, in which the HU values of the heart and great vessels in the CA-enhanced CT were replaced by average HU values obtained from the unenhanced CT.
  
  
  RESULTS
  The mean ∆HU value and the longest length of the heart and great vessels within the proton beam path in the field that passed through these structures were 189 ± 29 HU (range, 110-250 HU) and 7.1 ± 1.1 cm (range, 2.6-11.2 cm), respectively. The mean distal range error in the TPS because of the presence of CA was 1.0 ± 0.7 cm (range, 0.2-2.6 cm).
  
  
  CONCLUSIONS
  If CA-enhanced CT images are used for radiotherapy planning using a proton beam for the treatment of lung cancer, our results suggest that the HU values of the heart and great vessels should be replaced by the average HU values of soft tissue to avoid discrepancies between planned and delivered doses.
authors.affiliation: Research Institute and Hospital, National Cancer Center, Goyang, Gyeonggi, Korea.
authors.forename: Ui-Jung
authors.initials: UJ
authors.lastname: Hwang
authors.forename: Dong Ho
authors.initials: DH
authors.lastname: Shin
authors.forename: Tae Hyun
authors.initials: TH
authors.lastname: Kim
authors.forename: Sung Ho
authors.initials: SH
authors.lastname: Moon
authors.forename: Young Kyung
authors.initials: YK
authors.lastname: Lim
authors.forename: Hojin
authors.initials: H
authors.lastname: Jeong
authors.forename: Jeong-Eun
authors.initials: JE
authors.lastname: Rah
authors.forename: Sang Soo
authors.initials: SS
authors.lastname: Kim
authors.forename: Joo-Young
authors.initials: JY
authors.lastname: Kim
authors.forename: Dae Yong
authors.initials: DY
authors.lastname: Kim
authors.forename: Sung Yong
authors.initials: SY
authors.lastname: Park
authors.forename: Kwan Ho
authors.initials: KH
authors.lastname: Cho
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001011:Aorta / Q000528:radiation effects; D001027:Aortography; D003287:Contrast Media / Q000494:pharmacology*; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging / Q000528:radiation effects; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000528:radiation effects; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D061766:Proton Therapy; D011651:Pulmonary Artery / Q000000981:diagnostic imaging / Q000528:radiation effects; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media