Dose paintingDose painting with IMPT, helical tomotherapy and IMXT: A dosimetric comparison
Section snippets
Methods and materials
A treatment planning study was conducted on three HNC patients. Patient #1 (59 y, T2N3M0) and Patient #3 (48 y, T2N2cM0) had both oropharynx tumors, whereas Patient #2 (66 y, T4N2cM0) suffered from larynx cancer.
Results
In Fig. 1, the DPBN dose distributions for IMXT (A), HTT (B) and IMPT (C) are presented exemplarily for patient #2. The comparison of these three plans shows that with HTT, higher local DEs can be reached than with IMXT, whereas IMPT is able to deliver even steeper dose gradients. In this case the superimposed DE map demands a very focused spot of higher dose. Here, with IMXT a DE of 1.11 could be reached, whereas HTT and IMPT could escalate the dose by a factor of 1.23 and 1.26, respectively.
Discussion
The present study revealed that for the application of different DE strategies in HNC novel treatment techniques such as HTT and IMPT allow a better target coverage in the case of inhomogeneous dose prescriptions. Tomotherapy showed even slightly better coverage than IMPT. Furthermore, approximately equivalent levels of sparing OARs and unspecified normal tissues were obtained by HTT and IMXT. In contrast, IMPT has the potential to significantly reduce the dose to critical structures while
Conclusion
Even though only three patients were included into this planning study, all three treatment modalities IMPT, HTT and IMXT seem to be suitable for DP. Nevertheless, the observable differences in this study appear small in the light of the geometrical and biological uncertainties of such a treatment in practice. The main potential of IMPT lies in a significantly higher level of sparing distant parts of OARs. The dose to the PTV could theoretically be escalated by approximately 50% under
Acknowledgements
This project was financially supported by the German Research Foundation (DFG), Grant Nos. AL 877/1 and NU 33/8. The authors thank the Radiopharmacy Department, University Hospital Tübingen, for FMISO and FDG production, Dr. SM Eschmann for PET examinations and Dr. F Paulsen for patient recruitment.
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