Deep Hyperthermia Applicators: Σ-60 or Σ-Eye?

Abstract Aim: The goal of this study was functional evaluation of two deep hyperthermia (DHT) applicators to know whether we can replace Σ-60 with Σ-Eye (or vice versa). Methods: Data of all 48 patients with locally advanced cervical cancer who were treated within both applicators were analyzed. No performance of the longitudinal SAR-steering (SAR: specific absorption rate) option of Σ-Eye was done; thus, Σ-Eye was used as an Σ-60 with a modified water-bolus and shape. Temperature and RF-power (RF: radio frequency) indices were analyzed. Additionally a subgroup-analysis was applied for subgroups, categorized for the reasons of switching between the two applicators. Results: Analysis demonstrated a significant difference for power indices as applied to the two applicators; however, no difference was seen for temperature indices. The subgroup analyses revealed that when we applied Σ-Eye the power indices were mildly higher than those for the Σ-60. Contrarily, in majority of the patients applying Σ-Eye, number of off-switches and total switch-off time were lower than those for Σ-60. For the largest subgroup patients treated within the Σ-Eye, all temperature indices were slightly lower (ΔT=0.2–0.5°C) than those for the Σ-60 (p<0.028). Conclusion: In case of severe patients discomfort for DHT applicator, or when we are not satisfactory for the achieved temperatures, one can freely switch between the Σ-60 and Σ-Eye or vice versa during a DHT treatment series without loss in quality of treatment.