title: 3D versus 2D steering in patient anatomies: a comparison using hyperthermia treatment planning.
abstract: OBJECTIVE
  In this study hyperthermia treatment planning is used to investigate whether the target temperature during hyperthermia treatment can be increased using the 3D AMC-8 instead of the 2D AMC-4 system (AMC: Academic Medical Center).
  
  
  METHODS
  The heating ability of the AMC-4 and AMC-8 system was analysed for five patients with cervix uteri carcinoma. Dielectric and thermal models were generated, based on a hyperthermia planning computerised tomography (CT), at a resolution of 2.5 × 2.5 × 5.0 mm(3). Calculation of the electric fields with the finite-difference time-domain method was followed by SAR- and temperature-based optimisation. The ability to correct for axial shifts of the patient by phase/amplitude steering was investigated for both systems. Finally, it was investigated whether adjusting the ring-to-ring distance of the AMC-8 system can be used for further optimisation.
  
  
  RESULTS
  An average increase in T(90) of ∼0.5°C (0.2°-0.8°C) was found for the AMC-8 system compared to the AMC-4 system. The gain in T(50) and T(10) was also 0.5°C on average. The additional power required to achieve this gain was 36% to 71% of the power required for the AMC-4 system. The AMC-8 system has the capability of correcting changes in axial position (-8 cm, +8 cm), contrary to the AMC-4 system. For both systems the axial position should be known within 1-2 cm.
  
  
  CONCLUSIONS
  Hyperthermia treatment with the AMC-8 system can lead to a clinically relevant increase of the target temperature compared to treatment with the AMC-4 system. The AMC-8 system provides large freedom in the axial positioning of the patient.
authors.affiliation: Department of Radiation Oncology, Academic Medical Center, University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands. m.degreef@amc.uva.nl
authors.forename: M
authors.initials: M
authors.lastname: De Greef
authors.forename: H P
authors.initials: HP
authors.lastname: Kok
authors.forename: A
authors.initials: A
authors.lastname: Bel
authors.forename: J
authors.initials: J
authors.lastname: Crezee
mesh_terms: D003198:Computer Simulation; D005260:Female; D006801:Humans; D006979:Hyperthermia, Induced / Q000295:instrumentation / Q000379:methods*; D010347:Patient Care Planning; D002583:Uterine Cervical Neoplasms / Q000628:therapy*