title: In phantom assessment of superficial doses under TomoTherapy irradiation.
abstract: OBJECTIVE
  Aim of this work is the assessment of build-up and superficial doses of different clinical Head&Neck plans delivered with Helical TomoTherapy (HT) (Accuray, Sunnyvale, CA). Depth dose profiles and superficial dose points were measured in order to evaluate the Treatment Planning System (TPS) capability of an accurate dose modeling in regions of disequilibrium. Geometries and scattering conditions were investigated, similar to the ones generally encountered in clinical treatments.
  
  
  METHODS
  Measurements were performed with two dosimeters: Gafchromic® EBT3 films (Ashland Inc., Wayne, NJ) and a synthetic single crystal diamond detector (PTW-Frieburg microDiamond, MD). A modified version of the Alderson RANDO phantom was employed to house the detectors. A comparison with TPS data was carried out in terms of dose difference (DD) and distance-to-agreement (DTA).
  
  
  RESULTS
  DD between calculated data and MD measurements are within 4% even in points with high spatial dose variation. For depth profiles, EBT3 data show a DDmax of 3.3% and DTAmax of 2.2mm, in low and high gradient regions, respectively, and compare well with MD data. EBT3 superficial points always results in measured doses lower than TPS evaluated ones, with a maximum DTA value of 1.5mm.
  
  
  CONCLUSIONS
  Doses measured with the two devices are in good agreement and compare well with calculated data. The deviations found in the present work are within the reference tolerance level, suggesting that the HT TPS is capable of a precise dose estimation both in superficial regions and in correspondence with interfaces between air and PMMA.
authors.affiliation: Dipartimento di Scienze Biomediche, Sperimentali e Cliniche, Università degli Studi di Firenze, Italy; Azienda Ospedaliero Universitaria Careggi, Firenze, Italy. Electronic address: marghezani@gmail.com.
authors.forename: Margherita
authors.initials: M
authors.lastname: Zani
authors.affiliation: Dipartimento di Scienze Biomediche, Sperimentali e Cliniche, Università degli Studi di Firenze, Italy; Azienda Ospedaliero Universitaria Careggi, Firenze, Italy.
authors.forename: Cinzia
authors.initials: C
authors.lastname: Talamonti
authors.affiliation: Dipartimento di Scienze Biomediche, Sperimentali e Cliniche, Università degli Studi di Firenze, Italy; Azienda Ospedaliero Universitaria Careggi, Firenze, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Bucciolini
authors.affiliation: INFN-Dipartimento di Ingegneria Industriale, Università di Roma "Tor Vergata", Roma, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Marinelli
authors.affiliation: INFN-Dipartimento di Ingegneria Industriale, Università di Roma "Tor Vergata", Roma, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Verona-Rinati
authors.affiliation: Azienda Ospedaliero Universitaria Careggi, Firenze, Italy.
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Bonomo
authors.affiliation: Azienda Ospedaliero Universitaria Careggi, Firenze, Italy.
authors.forename: Fabiola
authors.initials: F
authors.lastname: Paiar
authors.affiliation: Dipartimento di Scienze Biomediche, Sperimentali e Cliniche, Università degli Studi di Firenze, Italy; Azienda Ospedaliero Universitaria Careggi, Firenze, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Pallotta
mesh_terms: D000465:Algorithms; D055592:Biophysical Phenomena; D018130:Diamond; D005373:Film Dosimetry / Q000706:statistics & numerical data; D006258:Head and Neck Neoplasms / Q000532:radiotherapy; D006801:Humans; D019047:Phantoms, Imaging; D011874:Radiometry / Q000295:instrumentation / Q000706:statistics & numerical data; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000706:statistics & numerical data*; D050397:Radiotherapy, Intensity-Modulated / Q000706:statistics & numerical data*
chemical_list: D018130:Diamond
keywords: Diamond detector; Radiochromic films; Superficial dosimetry; TomoTherapy