gms | German Medical Science

70. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC)
Joint Meeting mit der Skandinavischen Gesellschaft für Neurochirurgie

Deutsche Gesellschaft für Neurochirurgie (DGNC) e. V.

12.05. - 15.05.2019, Würzburg

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Radiotherapy treatment planning with protons and photons – dosimetric impact of novel carbon-fibre reinforced PEEK compared to standard titanium spinal pedicle screw instrumentation

Bestrahlungsplanung mit Protonen und Photonen – dosimetrischer Impakt neuartiger spinaler Carbonfaser-verstärkter PEEK im Vergleich zu herkömmlichen Titan-Schrauben-Stab-Implantaten

Meeting Abstract

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  • presenting/speaker Yu-Mi Ryang - TU München, Neurochirurgie, München, Deutschland
  • Birgit S. Müller - TU München, RadioOnkologie und Strahlentherapie, München, Deutschland
  • Markus Oechsner - TU München, RadioOnkologie und Strahlentherapie und Strahlentherapie, München, Deutschland
  • Matthias Düsberg - TU München, RadioOnkologie und Strahlentherapie und Strahlentherapie, München, Deutschland
  • Ehab Shiban - TU München, Neurochirurgie, München, Deutschland
  • Bernhard Meyer - TU München, Neurochirurgie, München, Deutschland
  • Stephanie E. Combs - TU München, RadioOnkologie und Strahlentherapie und Strahlentherapie, München, Deutschland
  • Jan J. Wilkens - TU München, RadioOnkologie und Strahlentherapie und Strahlentherapie, München, Deutschland

Deutsche Gesellschaft für Neurochirurgie. 70. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), Joint Meeting mit der Skandinavischen Gesellschaft für Neurochirurgie. Würzburg, 12.-15.05.2019. Düsseldorf: German Medical Science GMS Publishing House; 2019. DocP182

doi: 10.3205/19dgnc518, urn:nbn:de:0183-19dgnc5188

Veröffentlicht: 8. Mai 2019

© 2019 Ryang et al.
Dieser Artikel ist ein Open-Access-Artikel und steht unter den Lizenzbedingungen der Creative Commons Attribution 4.0 License (Namensnennung). Lizenz-Angaben siehe http://creativecommons.org/licenses/by/4.0/.

Gliederung

Text

Objective: Novel radiolucent carbon-fibre PEEK reinforced (CFP) pedicle screw systems for instrumentation of spinal tumors were introduced to improve radiotherapy (RT) treatment planning accuracy and follow-up imaging. We compared the dosimetric impact of the novel CFP implants with the standard titanium alloy (Ti) implants for intensity modulated proton (IMPT) and volumetric arc photon therapy (VMAT), with focus on uncertainties in Hounsfield unit (HU) assignment.

Methods: CT-data of a total of ten patients were used to simulate treatment planning with titanium alloy (Ti) implants (5 patients) and with carbon-fibre PEEK reinforced (CFP) implants (5 patients). CFP systems comprised of radiolucent pedicle screws with titanium coated shanks and titanium tulips and titanium rods. One IMPT and one VMAT plan was generated for each patient with a nominal relative stopping power (SP) (IMPT) and electron density (ρ) (VMAT).Then plans were recalculated onto the identical CT with increased and decreased SP or ρ by ±6% for the titanium components.

Results: For photon therapy, the deviations of recalculated VMAT dose distributions from the nominal plans for both screw types were negligible (differences in dose volume histogram criteria <2%). For proton therapy, the IMPT plans resulted in more heterogeneous target coverage, measured by the standard deviation σ inside the target, which increased on average by 7.6±2.3% (Ti) vs. 3.4±1.2% (CFP). Larger SPs lead to lower target minimum doses, lower SPs to higher dose maxima for proton treatment, with a more pronounced effect for titanium screws.

Conclusion: While for photon therapy there was no relevant difference in dosimetric quality between CFP and Ti pedicle screw system in VMAT plans, we found a beneficial effect of CFP pedicle screws compared to titanium due to a smaller dosimetric impact of CT-value uncertainties in IMPT plans for proton therapy. Thus, a reduction or elimination of Ti alloy components in spinal implants would lead to an improved dose calculation accuracy, and reduce the risk for tumor underdosage especially in proton treatment planning.