title: In-vivo dosimetry with Gafchromic films for multi-isocentric VMAT irradiation of total marrow lymph-nodes: a feasibility study.
abstract: BACKGROUND
  Total marrow (lymph-nodes) irradiation (TMI-TMLI) by volumetric modulated arc therapy (VMAT) was shown to be feasible by dosimetric feasibility studies. It was demonstrated that several partially overlapping arcs with different isocenters are required to achieve the desired coverage of the hematopoietic or lymphoid tissues targets and to spare the neighbouring healthy tissues. The effect of isocenter shifts was investigated with the treatment planning system but an in- vivo verification of the procedure was not carried out. The objective of this study was the in-vivo verification of the consistency between the delivered and planned doses using bi-dimensional GafChromic EBT3 films.
  
  
  METHODS
  In a first phase a phantom study was carried out to quantify the uncertainties under controlled conditions. In a second phase three patients treated with TMLI were enrolled for in-vivo dosimetry. The dose prescription was 2Gy in single fraction. Ten arcs paired on 4-6 isocenters were used to cover the target. Cone Beam Computed Tomography (CBCT) was used to verify the patient positioning at each isocenter. GafChromic EBT3 films were placed below the patient on the top of a dedicated immobilization system specifically designed. The dose maps measured with the EBT3 films were compared with the corresponding calculations along the patient support couch. Gamma Agreement Index (GAI) with dose difference of 5% and distance to agreement of 5 mm was computed.
  
  
  RESULTS
  In the phantom study, optimal target coverage and healthy tissue sparing was observed. GAI(5%,5 mm) was 99.4%. For the patient-specific measurements, GAI(5%,5 mm) was greater than 95% and GAI (5%,3 mm) > 90% for all patients.
  
  
  CONCLUSIONS
  In vivo measurements demonstrated the delivered dose to be in good agreement with the planned one for the TMI-TMLI protocol where partially overlapping arcs with different isocenters are required.
authors.affiliation: Radiation Oncology Department, Humanitas Clinical and Research Center, Rozzano, Milan, Italy. pietro.mancosu@humanitas.it.
authors.forename: Pietro
authors.initials: P
authors.lastname: Mancosu
authors.affiliation: Radiation Oncology Department, Humanitas Clinical and Research Center, Rozzano, Milan, Italy. piera.navarria@humanitas.it.
authors.forename: Pierina
authors.initials: P
authors.lastname: Navarria
authors.affiliation: Radiation Oncology Department, Humanitas Clinical and Research Center, Rozzano, Milan, Italy. giacomo.reggiori@humanitas.it.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Reggiori
authors.affiliation: Radiation Oncology Department, Humanitas Clinical and Research Center, Rozzano, Milan, Italy. luca.cozzi@humanitas.it.
authors.forename: Luca
authors.initials: L
authors.lastname: Cozzi
authors.affiliation: Radiation Oncology Department, Humanitas Clinical and Research Center, Rozzano, Milan, Italy. antonella.fogliata@humanitas.it.
authors.forename: Antonella
authors.initials: A
authors.lastname: Fogliata
authors.affiliation: Radiation Oncology Department, Humanitas Clinical and Research Center, Rozzano, Milan, Italy. anna.gaudino@humanitas.it.
authors.forename: Anna
authors.initials: A
authors.lastname: Gaudino
authors.affiliation: Radiation Oncology Department, Humanitas Clinical and Research Center, Rozzano, Milan, Italy. francesca.lobefalo@humanitas.it.
authors.forename: Francesca
authors.initials: F
authors.lastname: Lobefalo
authors.affiliation: Radiation Oncology Department, Humanitas Clinical and Research Center, Rozzano, Milan, Italy. lucia.paganini@humanitas.it.
authors.forename: Lucia
authors.initials: L
authors.lastname: Paganini
authors.affiliation: Radiation Oncology Department, Humanitas Clinical and Research Center, Rozzano, Milan, Italy. valentina.palumbo@humanitas.it.
authors.forename: Valentina
authors.initials: V
authors.lastname: Palumbo
authors.affiliation: Bone Marrow Transplantation Unit, Humanitas Clinical and Research Center, Rozzano, Milan, Italy. barbara.sarina@humanitas.it.
authors.forename: Barbara
authors.initials: B
authors.lastname: Sarina
authors.affiliation: Radiation Oncology Department, Humanitas Clinical and Research Center, Rozzano, Milan, Italy. antonella.stravato@humanitas.it.
authors.forename: Antonella
authors.initials: A
authors.lastname: Stravato
authors.affiliation: Bone Marrow Transplantation Unit, Humanitas Clinical and Research Center, Rozzano, Milan, Italy. luca.castagna@humanitas.it.
authors.forename: Luca
authors.initials: L
authors.lastname: Castagna
authors.affiliation: Radiation Oncology Department, Humanitas Clinical and Research Center, Rozzano, Milan, Italy. stefano.tomatis@humanitas.it.
authors.forename: Stefano
authors.initials: S
authors.lastname: Tomatis
authors.affiliation: Radiation Oncology Department, Humanitas Clinical and Research Center, Rozzano, Milan, Italy. marta.scorsetti@humanitas.it.
authors.forename: Marta
authors.initials: M
authors.lastname: Scorsetti
mesh_terms: D001853:Bone Marrow / Q000528:radiation effects*; D005240:Feasibility Studies; D005373:Film Dosimetry / Q000379:methods*; D019337:Hematologic Neoplasms / Q000532:radiotherapy*; D006801:Humans; D008198:Lymph Nodes / Q000528:radiation effects*; D056888:Patient Positioning; D019047:Phantoms, Imaging; D011379:Prognosis; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D014057:Tomography, X-Ray Computed