title: Impact of intravenous contrast used in computed tomography on radiation dose to carotid arteries and thyroid in intensity-modulated radiation therapy planning for nasopharyngeal carcinoma.
abstract: The aim of this study was to investigate if intravenous contrast injection affected the radiation doses to carotid arteries and thyroid during intensity-modulated radiation therapy (IMRT) planning for nasopharyngeal carcinoma (NPC). Thirty consecutive patients with NPC underwent plain computed tomography (CT) followed by repeated scanning after contrast injection. Carotid arteries (common, external, internal), thyroid, target volumes, and other organs-at-risk (OARs), as well as IMRT planning, were based on contrast-enhanced CT (CE-CT) images. All these structures and the IMRT plans were then copied and transferred to the non-contrast-enhanced CT (NCE-CT) images, and dose calculation without optimization was performed again. The radiation doses to the carotid arteries and the thyroid based on CE-CT and NCE-CT were then compared. Based on CE-CT, no statistical differences, despite minute numeric decreases, were noted in all dosimetric parameters (minimum, maximum, mean, median, D05, and D01) of the target volumes, the OARs, the carotid arteries, and the thyroid compared with NCE-CT. Our results suggested that compared with NCE-CT planning, CE-CT scanning should be performed during IMRT for better target and OAR delineation, without discernible change in radiation doses.
authors.affiliation: Department of Clinical Oncology, Queen Mary Hospital, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong. Electronic address: vhflee@hku.hk.
authors.forename: Victor Ho Fun
authors.initials: VHF
authors.lastname: Lee
authors.affiliation: Department of Clinical Oncology, Queen Mary Hospital, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong.
authors.forename: Sherry Chor Yi
authors.initials: SCY
authors.lastname: Ng
authors.affiliation: Department of Clinical Oncology, Queen Mary Hospital, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong.
authors.forename: Dora Lai Wan
authors.initials: DLW
authors.lastname: Kwong
authors.affiliation: Department of Clinical Oncology, Queen Mary Hospital, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong.
authors.forename: Ka On
authors.initials: KO
authors.lastname: Lam
authors.affiliation: Department of Clinical Oncology, Queen Mary Hospital, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong.
authors.forename: To Wai
authors.initials: TW
authors.lastname: Leung
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D002339:Carotid Arteries / Q000000981:diagnostic imaging / Q000187:drug effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D000069079:Radiation Exposure / Q000032:analysis*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013961:Thyroid Gland / Q000000981:diagnostic imaging / Q000187:drug effects*; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: CT contrast; Carotid arteries; Dose calculation; Intensity-modulated radiation therapy; Nasopharyngeal carcinoma; Thyroid