title: Set-up errors in head and neck cancer patients treated with intensity modulated radiation therapy: Quantitative comparison between three-dimensional cone-beam CT and two-dimensional kilovoltage images.
abstract: OBJECTIVE
  To compare the patient set-up error detection capabilities of three-dimensional cone beam computed tomography (3D-CBCT) and two-dimensional orthogonal kilovoltage (2D-kV) techniques.
  
  
  METHODS
  3D-CBCT and 2D-kV projections were acquired on 29 head-and-neck (H&N) patients undergoing Intensity Modulated Radiotherapy (IMRT) on the first day of treatment (time 0) and after the delivery of 40 Gy and 50 Gy. Set-up correction vectors were analyzed after fully automatic image registration as well as after revision by radiation oncologists. The dosimetric effects of the different sensitivities of the two image guidance techniques were assessed.
  
  
  RESULTS
  A statistically significant correlation among detected set-up deviations by the two techniques was found along anatomical axes (0.60 < ρ < 0.72, p < 0.0001); no correlation was found for table rotation (p = 0.41). No evidence of statistically significant differences between the indications provided along the course of the treatment was found; this was also the case when full automatic versus manually refined correction vectors were compared. The dosimetric effects analysis revealed slight statistically significant differences in the median values of the maximum relative dose to mandible, spinal cord and its 5 mm Planning Organ at Risk Volume (0.95%, 0.6% and 2.45%, respectively), with higher values (p < 0.01) observed when 2D-kV corrections were applied.
  
  
  CONCLUSIONS
  A similar sensitivity to linear set-up errors was observed for 2D-kV and 3D-CBCT image guidance techniques in our H&N patient cohort. Higher rotational deviations around the table vertical axis were detected by the 3D-CBCT with respect to the 2D-kV method, leading to a consistent better sparing of organs at risk.
authors.affiliation: Division of Radiation Oncology, European Institute of Oncology, via Ripamonti 435, Milano 20141, Italy. Electronic address: delia.ciardo@ieo.it.
authors.forename: Delia
authors.initials: D
authors.lastname: Ciardo
authors.affiliation: Division of Radiation Oncology, European Institute of Oncology, via Ripamonti 435, Milano 20141, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Alterio
authors.affiliation: Division of Radiation Oncology, European Institute of Oncology, via Ripamonti 435, Milano 20141, Italy; Department of Health Sciences, University of Milan, via Festa del Perdono 7, Milano 20122, Italy.
authors.forename: Barbara Alicja
authors.initials: BA
authors.lastname: Jereczek-Fossa
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria (DEIB), Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, Italy; Centro Nazionale di Adroterapia Oncologica (CNAO), Strada Campeggi 53, Pavia 27100, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Riboldi
authors.affiliation: Division of Radiation Oncology, European Institute of Oncology, via Ripamonti 435, Milano 20141, Italy.
authors.forename: Dario
authors.initials: D
authors.lastname: Zerini
authors.affiliation: Division of Epidemiology and Biostatistics, European Institute of Oncology, via Ripamonti 435, 20141 Milano, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Santoro
authors.affiliation: Division of Radiation Oncology, European Institute of Oncology, via Ripamonti 435, Milano 20141, Italy.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Preve
authors.affiliation: Unit of Medical Physics, European Institute of Oncology, via Ripamonti 435, 20141 Milano, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Rondi
authors.affiliation: Unit of Medical Physics, European Institute of Oncology, via Ripamonti 435, 20141 Milano, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Comi
authors.affiliation: Division of Radiation Oncology, European Institute of Oncology, via Ripamonti 435, Milano 20141, Italy.
authors.forename: Flavia
authors.initials: F
authors.lastname: Serafini
authors.affiliation: Division of Radiation Oncology, European Institute of Oncology, via Ripamonti 435, Milano 20141, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Laudati
authors.affiliation: Division of Head and Neck Surgery, European Institute of Oncology, via Ripamonti 435, 20141 Milano, Italy.
authors.forename: Mohssen
authors.initials: M
authors.lastname: Ansarin
authors.affiliation: Department of Radiology, European Institute of Oncology, via Ripamonti 435, 20141 Milano, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Preda
authors.affiliation: Dipartimento di Elettronica, Informazione e Bioingegneria (DEIB), Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano, Italy; Centro Nazionale di Adroterapia Oncologica (CNAO), Strada Campeggi 53, Pavia 27100, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Baroni
authors.affiliation: Division of Radiation Oncology, European Institute of Oncology, via Ripamonti 435, Milano 20141, Italy; Department of Health Sciences, University of Milan, via Festa del Perdono 7, Milano 20122, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Orecchia
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D011874:Radiometry; D061106:Radiotherapy Setup Errors; D050397:Radiotherapy, Intensity-Modulated; D013997:Time Factors; D055815:Young Adult
keywords: Dosimetry; Head and neck cancer; IGRT; Set-up verification