title: Temperature simulations in hyperthermia treatment planning of the head and neck region: rigorous optimization of tissue properties.
abstract: OBJECTIVE
  Hyperthermia treatment planning (HTP) is used in the head and neck region (H&N) for pretreatment optimization, decision making, and real-time HTP-guided adaptive application of hyperthermia. In current clinical practice, HTP is based on power-absorption predictions, but thermal dose-effect relationships advocate its extension to temperature predictions. Exploitation of temperature simulations requires region- and temperature-specific thermal tissue properties due to the strong thermoregulatory response of H&N tissues. The purpose of our work was to develop a technique for patient group-specific optimization of thermal tissue properties based on invasively measured temperatures, and to evaluate the accuracy achievable.
  
  
  METHODS
  Data from 17 treated patients were used to optimize the perfusion and thermal conductivity values for the Pennes bioheat equation-based thermal model. A leave-one-out approach was applied to accurately assess the difference between measured and simulated temperature (∆T). The improvement in ∆T for optimized thermal property values was assessed by comparison with the ∆T for values from the literature, i.e., baseline and under thermal stress.
  
  
  RESULTS
  The optimized perfusion and conductivity values of tumor, muscle, and fat led to an improvement in simulation accuracy (∆T: 2.1 ± 1.2 °C) compared with the accuracy for baseline (∆T: 12.7 ± 11.1 °C) or thermal stress (∆T: 4.4 ± 3.5 °C) property values.
  
  
  CONCLUSIONS
  The presented technique leads to patient group-specific temperature property values that effectively improve simulation accuracy for the challenging H&N region, thereby making simulations an elegant addition to invasive measurements. The rigorous leave-one-out assessment indicates that improvements in accuracy are required to rely only on temperature-based HTP in the clinic.
authors.affiliation: Department of Radiation Oncology, Hyperthermia Unit, Erasmus MC—Cancer Institute, Groene Hilledijk 301, 3008 AE Rotterdam, the Netherlands. r.f.verhaart@erasmusmc.nl
authors.forename: René F
authors.initials: RF
authors.lastname: Verhaart
authors.forename: Zef
authors.initials: Z
authors.lastname: Rijnen
authors.forename: Valerio
authors.initials: V
authors.lastname: Fortunati
authors.forename: Gerda M
authors.initials: GM
authors.lastname: Verduijn
authors.forename: Theo
authors.initials: T
authors.lastname: van Walsum
authors.forename: Jifke F
authors.initials: JF
authors.lastname: Veenland
authors.forename: Margarethus M
authors.initials: MM
authors.lastname: Paulides
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D006258:Head and Neck Neoplasms / Q000503:physiopathology* / Q000628:therapy*; D006801:Humans; D006979:Hyperthermia, Induced / Q000379:methods*; D008954:Models, Biological; D066230:Patient-Specific Modeling; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013813:Therapy, Computer-Assisted / Q000379:methods*; D013814:Thermal Conductivity; D013817:Thermography / Q000379:methods*; D016896:Treatment Outcome