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*P. Togni, Z. Rijnen, W.C.M. Numan, R.F. Verhaart, J.F. Bakker, G.C. van Rhoon and M.M. Paulides

This study evaluates the quality improvements of a new antenna arrangement in a mechanically redesigned HYPERcollar applicator for deep local head-and-neck hyperthermia treatment. The research questions focus on treatment quality improvement potential using the new antenna arrangement in terms of hot spot reduction, target coverage, and heating capability. Various applicator models and clinical experiences are analyzed to optimize the system for maximum effectiveness.

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*P. Togni, Z. Rijnen, W.C.M. Numan, R.F. Verhaart, J.F. Bakker, G.C. van Rhoon and M.M. Paulides

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  1. Journal Club 08-04-2013 Grant DDHK2009-4270 Electromagnetic redesign of the HYPERcollarapplicator: towards improved deep localhead-and-neck hyperthermia *P. Togni, Z. Rijnen, W.C.M. Numan, R.F. Verhaart, J.F. Bakker, G.C. van Rhoon and M.M. Paulides • * p.togni@erasmusmc.nl • Department of Radiation Oncology, Erasmus MC-Daniel den Hoed Cancer Center, Rotterdam, The Netherlands Submitted to : Physics in Medicine and Biology

  2. Content • Introduction • Methods • Results • Discussion • Conclusion

  3. Introduction Research question: • Can we improve treatment quality with a new antenna arrangement? Goal: • Evaluate quality improvements using a new antenna arrangement implemented in a mechanically redesigned HYPERcollar: • hot-spot • target coverage • heating capability

  4. Methods: applicator models

  5. clinical experience Methods: applicator models

  6. 12 antennas • 2 rings • circular array arrangement • bulging WB clinical experience Methods: applicator models

  7. 12 antennas • 2 rings • circular array arrangement • bulging WB • 20 antennas • 3 rings • ‘horse-shoe’’ array arrangement • bulging WB clinical experience Methods: applicator models

  8. Methods: applicator models • 12 antennas • 2 rings • circular array arrangement • bulging WB • 20 antennas • 3 rings • ‘horse-shoe’’ array arrangement • bulging WB clinical experience • 20 antennas • 3 rings • ‘horse-shoe’’ array arrangement • reduced diameter • flat-end WB

  9. current study • 12 antennas • 2 rings • circular array arrangement • bulging WB • 20 antennas • 3 rings • ‘horse-shoe’’ array arrangement • bulging WB clinical experience • 20 antennas • 3 rings • ‘horse-shoe’’ array arrangement • reduced diameter • flat-end WB Methods: applicator models

  10. Methods: patient inclusion first 26 patient treatedwith HYPERcollar applicator

  11. Methods: optimization and evaluation parameters: • Hotspot importance: • Tumor coverage : • Target heating capability : • mean SAR in target • max theoretical system power (antenna use uniformity)

  12. Results: ‘horse-shoe’ array arrangement justification HYPERcollar model (I)

  13. Results: ‘horse-shoe’ array arrangement justification HYPERcollar model (I) • Limited contribution of dorsal antenna (< 0.16) • Indirect contribution via the head-rest  high sensitivity to slight off-sets •  dorsal antenna excluded from HYPERcollar (I) optimizations

  14. Results: hot-spot reduction (HTQ) tumor coverage (TC25)

  15. Results: hot-spot reduction (HTQ) tumor coverage (TC25) -27 % -32 % • ‘Horse-shoe’’ layout introduce a importance reduction

  16. Results: hot-spot reduction (HTQ) tumor coverage (TC25) +3 % +2 % -27 % -32 % • Limited improvement of coverage when used as optimization function

  17. Results: hot-spot reduction (HTQ) tumor coverage (TC25) 81% 73% -27 % -32 % 59 % • Coverage improvement for worst cases  “hard to heat” patients

  18. Results: mean SAR target (Pin = 1W)

  19. Results: mean SAR target (Pin = 1W) +170 % +53%

  20. Results: mean SAR target (Pin = 1W) +170 % +53% +34% +112 %

  21. Results: mean SAR target (Pin = 1W) +170 % +53% +34% +112 % • New desing over-perform modified HYPERcollar •  reduced back plane diameter (400 mm  320 mm)

  22. Results: maximum system power

  23. Results: maximum system power +62% +59%

  24. Results: maximum system power +37% +28% +62% +59%

  25. Results: maximum system power +37% +28% +62% +59% • Applicators with “horse-shoe’’ perform better •  more uniform contribute of antennas

  26. Discussion * Paulides et al. 2007 Int. J. Hyperthermia 23(1): 59–67 **Trefna et al. 2010 Int. J. Hyperthermia 26(2): 185–197. • new array arrangement alone substantially reduce hotspot importance  (HTQ -27% model II, HTQ -32% model III) • increased number of antennas produce a better power focusing  in agreement with *Paulides et al. 2007 and **Trefna et al. 2010 • possibility to choose 12 antennas out of 20 allow a more uniform antenna use  reduced probability of power to be treatment limiting • reduced ground plane diameter allowed better focus capability  in agreement with *Paulides et al. 2007

  27. Discussion • new design did not outperformed mod. HYPERcollar in TC25  bulging WB allow a better power deposition in targets extending outside applicator ground plane (6/8 ‘neck’ patients)  bulging WB has low reproducibility  increased treatment quality variation in clinic. • solution applicator tilted 30° for ‘neck’ patients  WB extensions in caudal direction to be investigated

  28. Discussion * Canters et al. 2009 , Phys Med Biol 54: 3923–3936. ** Myerson et al. 1990, Int J Radiat Oncol Biol Phys 18(5): 1123–1129 *** Lee et al. 1998, Int J Radiat Oncol Biol Phys 40(2): 365–375 • two SAR-based optimization function were used (HTQ + TC25) because a quality parameter predictive for H&N HT outcome was not established yet: • HTQ: best correlate with T50 in DHT (*Canters et al. 2009) • TC25: target totally cover by 25% iso-SAR best factor for prediction clinical outcome in recurrent breast carcinoma (**Myerson et al. 1990, ***Lee et al. 1998)  both are used to prove robustness of new design for H&N HT

  29. Discussion * Canters et al. 2009 , Phys Med Biol 54: 3923–3936. ** de Greef et al. 2010 Med Phys 37(9): 4540–4550. • uncertainties evaluation in HT simulation studies: • SAR patterns robustness to patient positioning variations in DHT (*Canters et al. 2009) • role dielectric and perfusion uncertainties on HTP (**de Greef et al. 2010) • In our case large number of patients (26) with targets in different locations represents an ‘anatomy-based’ uncertainties evaluation  more relevant to verify heating capability improvement and design robustness

  30. Conclusions • HYPERcollar array arrangement sub-optimaI limited contribution of dorsal antennas • “Horse-shoe” array arrangement integrated in mechanical redesign  hot-spot : – 32 % (HTQ)  target coverage : + 2 % (TC25)  focus capability : > + 112 % (mean SAR target [1W ])  max system power : 981 W (+49 %) • Substantial improvement theoretical H&N treatment quality • Combination with mechanical redesign improved reproducibility  expected strong improvement in clinical treatment quality

  31. Grant DDHK2009-4270 Thank you for you attentionquestions?

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