title: Effects and consequences of Digisonic SP cochlear implant on radiotherapy planning.
abstract: The aim of this study was to assess dose attenuation by a Digisonic SP cochlear implant (CI) and evaluate its impact on treatment planning. The Digisonic CI was irradiated with 6 MV photons. Overall dose attenuation was assessed with MOSFET dosimeters and Gafchromic films. In addition, we evaluated the attenuation of separate CI components. Dose attenuation was also calculated using different radiation treatment planning systems (TPS) softwares and dose calculation algorithms. The CI was placed on a head phantom. Single-beam and multiple-beam plans were evaluated for dose attenuation using two radiation techniques (Conformal and Stereotactic radiotherapy) and four different algorithms (Clarkson, Point Kernel-Superposition, Ray Tracing and Monte Carlo). MOSFET and Gafchromics film showed maximal 6-7.5% radiation dose attenuation, at the center of the CI. Computerized TPS-based dose attenuation by the implant was 4-8.1%, using a single ipsilateral field. No clinically meaningful dose attenuation was found in multiple field plans owing to the contribution of various beam paths with only a couple going through the implant using either conventional conformal or stereotactic treatment plans. Dose attenuation induced by a Digisonic SP CI is about 6%, for single 6 MV photon field. This dose reduction is unlikely to be clinically significant, as single-field radiotherapy plans to this anatomic region are uncommon.
authors.affiliation: Department of Head and Neck Surgery, University Center-Institut Universitaire de la Face et du Cou, 33 Av. Valombrose, 06189, Nice Cedex 2, France, guevara.n@chu-nice.fr.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Guevara
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Atean
authors.forename: David
authors.initials: D
authors.lastname: Benoit
authors.forename: Yoann
authors.initials: Y
authors.lastname: Pointreau
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Angellier
authors.forename: Serge
authors.initials: S
authors.lastname: Marcie
authors.forename: Sonia
authors.initials: S
authors.lastname: Saaï
authors.forename: Dan
authors.initials: D
authors.lastname: Gnansia
authors.forename: Juliette
authors.initials: J
authors.lastname: Thariat
mesh_terms: D000465:Algorithms; D019929:Cochlear Implantation / Q000295:instrumentation / Q000379:methods; D003054:Cochlear Implants; D006801:Humans; D021621:Imaging, Three-Dimensional; D008953:Models, Anatomic; D009010:Monte Carlo Method; D010347:Patient Care Planning; D019047:Phantoms, Imaging; D011878:Radiotherapy / Q000379:methods / Q000592:standards; D011879:Radiotherapy Dosage / Q000592:standards*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*