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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

Journal Club 08-04-2013. Grant DDHK2009-4270. Electromagnetic redesign of the HYPERcollar applicator: towards improved deep local head-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

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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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