Dosimetric effects of residual uncertainties in carbon ion treatment of head chordoma.

PURPOSE To investigate dose distribution variations due to setup errors and range uncertainties in image-guided carbon ion radiotherapy of head chordoma. MATERIALS AND METHODS Ten treatment plans were retrospectively tested with TRiP98 against ±1.0 mm and ±1.0° setup errors, as observed in clinical routine, and 2.6% range uncertainty when 2mm CTV-to-PTV margins were applied. Single-fraction simulations were compared with the total treatment dose in terms of DVH bands, conformity and inhomogeneity. The contribution of image processing artifacts on reported results was also discussed, as a function of the imaging dataset resolution. RESULTS Results showed that safety margins grant the conformal target coverage in presence of setup errors with D95(CTV) variations below 10% in 7 patients out of 10. Instead, the inclusion of range uncertainty yielded to appreciable dose degradation, reporting larger effects for CTV and dose conformity, whereas reduced impact is found on the organ-at-risk. The fractionation scheme positively affects dose conformity and inhomogeneity; conversely its influence on DVH bands is strongly related to the patient anatomy. CONCLUSION Besides safety margins, setup and range uncertainties lead to non-negligible combined contribution. Systematical treatment plan robustness assessment against expected uncertainties is thus encouraged, selecting beam settings and fractionation schemes where homogeneity is preserved.

[1]  M. Krämer,et al.  Ion beam transport calculations and treatment plans in particle therapy , 2010 .

[2]  I. Zuna,et al.  Evaluation of therapeutic potential of heavy ion therapy for patients with locally advanced prostate cancer. , 2004, International journal of radiation oncology, biology, physics.

[3]  A J Lomax,et al.  Experimental verification of IMPT treatment plans in an anthropomorphic phantom in the presence of delivery uncertainties , 2011, Physics in medicine and biology.

[4]  Kenny Q. Ye.  Orthogonal Column Latin Hypercubes and Their Application in Computer Experiments , 1998 .

[5]  Nobuyuki Kanematsu,et al.  A robust algorithm of intensity modulated proton therapy for critical tissue sparing and target coverage , 2011, Physics in medicine and biology.

[6]  M Scholz,et al.  Rapid calculation of biological effects in ion radiotherapy , 2006, Physics in medicine and biology.

[7]  A J Lomax,et al.  Intensity modulated proton therapy and its sensitivity to treatment uncertainties 2: the potential effects of inter-fraction and inter-field motions , 2008, Physics in medicine and biology.

[8]  Hanne M Kooy,et al.  Target volume dose considerations in proton beam treatment planning for lung tumors. , 2005, Medical physics.

[9]  Wei Liu,et al.  Statistical assessment of proton treatment plans under setup and range uncertainties. , 2013, International journal of radiation oncology, biology, physics.

[10]  E. Pedroni,et al.  The calibration of CT Hounsfield units for radiotherapy treatment planning. , 1996, Physics in medicine and biology.

[11]  O Jäkel,et al.  Three-dimensional accuracy and interfractional reproducibility of patient fixation and positioning using a stereotactic head mask system. , 2001, International journal of radiation oncology, biology, physics.

[12]  M. Herk.  Errors and margins in radiotherapy. , 2004 .

[13]  O Jäkel,et al.  Treatment planning for heavy-ion radiotherapy: physical beam model and dose optimization. , 2000, Physics in medicine and biology.

[14]  Thomas Bortfeld,et al.  Visualization of a variety of possible dosimetric outcomes in radiation therapy using dose-volume histogram bands. , 2012, Practical radiation oncology.

[15]  E Pedroni,et al.  The precision of proton range calculations in proton radiotherapy treatment planning: experimental verification of the relation between CT-HU and proton stopping power. , 1998, Physics in medicine and biology.

[16]  Alessandra Bolsi,et al.  Experiences at the Paul Scherrer Institute with a remote patient positioning procedure for high-throughput proton radiation therapy. , 2008, International journal of radiation oncology, biology, physics.

[17]  Marco Riboldi,et al.  A comparative study between the imaging system and the optical tracking system in proton therapy at CNAO , 2013, Journal of radiation research.

[18]  T. Tessonnier,et al.  Development and application of tools for Monte Carlo based simulations in a particle beam radiotherapy facility. , 2014, Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine.

[19]  Michael Gillin,et al.  Spot scanning proton beam therapy for prostate cancer: treatment planning technique and analysis of consequences of rotational and translational alignment errors. , 2010, International journal of radiation oncology, biology, physics.

[20]  R. Engenhart-Cabillic,et al.  Assessment of the Accuracy of a Conventional Simulation for Radiotherapy of Head and Skull Base Tumors , 2003, Technology in cancer research & treatment.

[21]  Jürgen Debus,et al.  Robotic-based carbon ion therapy and patient positioning in 6 degrees of freedom: setup accuracy of two standard immobilization devices used in carbon ion therapy and IMRT , 2012, Radiation Oncology.

[22]  Joao Seco,et al.  Treatment of non-small cell lung cancer patients with proton beam-based stereotactic body radiotherapy: dosimetric comparison with photon plans highlights importance of range uncertainty. , 2012, International journal of radiation oncology, biology, physics.

[23]  U. Jelen,et al.  Dosimetric consequences of pencil beam width variations in scanned beam particle therapy , 2013, Physics in medicine and biology.

[24]  A. Lomax,et al.  Intensity modulated proton therapy and its sensitivity to treatment uncertainties 1: the potential effects of calculational uncertainties , 2008, Physics in medicine and biology.

[25]  A. Lomax,et al.  Is it necessary to plan with safety margins for actively scanned proton therapy? , 2011, Physics in medicine and biology.

[26]  M. D. McKay,et al.  A comparison of three methods for selecting values of input variables in the analysis of output from a computer code , 2000 .

[27]  Oliver Jäkel,et al.  Accuracy of robotic patient positioners used in ion beam therapy , 2013, Radiation oncology.

[28]  U. Jelen,et al.  Robustness against interfraction prostate movement in scanned ion beam radiation therapy. , 2012, International journal of radiation oncology, biology, physics.

[29]  M Durante,et al.  Algorithms for the optimization of RBE-weighted dose in particle therapy , 2013, Physics in medicine and biology.

[30]  Stanley J. Rosenthal,et al.  Intra- and interfractional patient motion for a variety of immobilization devices. , 2005, Medical physics.

[31]  Filippo Ammazzalorso,et al.  Dosimetric consequences of intrafraction prostate motion in scanned ion beam radiotherapy. , 2014, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[32]  Thomas Haberer,et al.  Radiation Oncology BioMed Central , 2006 .

[33]  Oliver Jäkel,et al.  Dynamic Target Definition: a novel approach for PTV definition in ion beam therapy. , 2013, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.