Dosimetric impact of reduced nozzle-to-isocenter distance in intensity-modulated proton therapy of intracranial tumors in combined proton-carbon fixed-nozzle treatment facilities

Radiation Oncology

Andrea Wittig¹  Uli Weber²  Rita Engenhart-Cabillic¹  Filippo Ammazzalorso¹  Marta E Bubula¹  Urszula Jelen¹ 

[1] Department of Radiotherapy and Radiation Oncology, Philipps-University of Marburg, Marburg, Baldingerstrasse 35043, Germany;Particle Therapy Center, Rhön Klinikum AG, Marburg 35043, Germany

关键词: Treatment room geometry;    Normal tissue sparing;    Brain tumor;    Raster scanning;    Pencil beam;    Intensity-modulated proton therapy;   

Others  :  1152979
DOI  :  10.1186/1748-717X-8-218

 received in 2013-06-04, accepted in 2013-08-29,  发布年份 2013

【 摘 要 】

Background

In combined proton-carbon fixed-nozzle treatment facilities with raster scanning delivery, the scattering of proton pencil beams caused by nozzle elements and the relatively large nozzle-to-isocenter distance cause a beam broadening. This may pose limitations to the achievable dose conformity. One way to counteract this effect is by delivering the treatment in a position closer to the nozzle than the room isocenter. Purpose of this study was to assess the potential dosimetric benefit of such solution, in terms of dose conformity and normal tissue sparing, in intensity-modulated proton therapy (IMPT) of intracranial tumors.

Material and methods

For 12 patients with intracranial lesions, IMPT-plans were created at two treatment positions: nozzle-to-treatment-isocenter distance: 100 cm (room isocenter) and nozzle-to-treatment-isocenter distance: 60 cm. The resulting plans were compared in terms of dose distributions, dose-volume histograms and selected dosimetric indexes.

Results

With comparable target coverage, statistically significant normal tissue sparing was achieved through the reduction of the distance between nozzle and treatment isocenter. The decrease in mean dose (D_mean) was 12.5% to the whole brain, 16.2% to the brainstem, 9.7% and 15.4% to the temporal lobes, 10.0% and 12.9% to the hippocampi, 11.8% and 12.5% to the optic nerves and 0.2% to the chiasm. The volume receiving at least 10% of the prescribed dose (V_10%) was reduced by more than 10% for most organs at risk (OARs). The maximum dose (D_near-max) values to most OARs remained without significant difference.

Conclusion

A reduced distance between nozzle and treatment isocenter leads to steeper lateral dose gradients and significantly reduces the volume of OARs adjacent to the target, which receives low to intermediate doses. Technical solutions shifting the treatment isocenter closer to the nozzle should be considered in clinical situations, where critical OARs are adjacent to the beam channel and where the integral dose should be minimized.

【 授权许可】

   
2013 Jelen et al.; licensee BioMed Central Ltd.

【 图 表 】

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【 参考文献 】

• [1]Boehling NS, Grosshans DR, Bluett JB, Palmer MT, Song X, Amos RA, Sahoo N, Meyer JJ, Mahajan A, Woo SY: Dosimetric comparison of three-dimensional conformal proton radiotherapy, intensity-modulated proton therapy, and intensity-modulated radiotherapy for treatment of pediatric craniopharyngiomas. Int J Radiat Oncol Biol Phys 2012, 82:643-652.
• [2]Dennis ER, Bussiere MR, Niemierko A, Lu MW, Fullerton BC, Loeffler JS, Shih HA: A comparison of critical structure dose and toxicity risks in patients with Low grade gliomas treated with IMRT versus proton radiation therapy. Technol Cancer Res Treat 2012, 12(1):1-9.
• [3]MacDonald SM, Safai S, Trofimov A, Wolfgang J, Fullerton B, Yeap BY, Bortfeld T, Tarbell NJ, Yock T: Proton radiotherapy for childhood ependymoma: initial clinical outcomes and dose comparisons. Int J Radiat Oncol Biol Phys 2008, 71:979-986.
• [4]Weber DC, Schneider R, Goitein G, Koch T, Ares C, Geismar JH, Schertler A, Bolsi A, Hug EB: Spot scanning-based proton therapy for intracranial meningioma: long-term results from the Paul Scherrer Institute. Int J Radiat Oncol Biol Phys 2012, 83:865-871.
• [5]Kuhlthau KA, Pulsifer MB, Yeap BY, Rivera Morales D, Delahaye J, Hill KS, Ebb D, Abrams AN, Macdonald SM, Tarbell NJ, Yock TI: Prospective study of health-related quality of life for children with brain tumors treated with proton radiotherapy. J Clin Oncol 2012, 30:2079-2086.
• [6]Weber U, Kraft G: Comparison of carbon ions versus protons. Cancer J 2009, 15:325-332.
• [7]Suit H, DeLaney T, Goldberg S, Paganetti H, Clasie B, Gerweck L, Niemierko A, Hall E, Flanz J, Hallman J, Trofimov A: Proton vs carbon ion beams in the definitive radiation treatment of cancer patients. Radiother Oncol 2010, 95:3-22.
• [8]Schardt D, Elsässer T, Schultz-Ertner D: Heavy-ion tumor therapy: physical and radiobiological benefits. Rev Mod Phys 2010, 82:383-425.
• [9]Badura E, Brand H, Essel HG, Haberer T, Hardel H, Hoffmann J, Kurz N, Liebold P, Ott W, Poppensieker K, Richter M: Control system for cancer therapy with a heavy ion beam at GSI. IEEE Trans Nucl Sci 2000, 47:170-173.
• [10]Hamm K, Henzel M, Gross MW, Surber G, Kleinert G, Engenhart-Cabillic R: Radiosurgery/stereotactic radiotherapy in the therapeutical concept for skull base meningiomas. Zentralbl Neurochir 2008, 69:14-21.
• [11]Paganetti H, Niemierko A, Ancukiewicz M, Gerweck LE, Goitein M, Loeffler JS, Suit HD: Relative biological effectiveness (RBE) values for proton beam therapy. Int J Radiat Oncol Biol Phys 2002, 53:407-421.
• [12]Emami B, Lyman J, Brown A, Coia L, Goitein M, Munzenrider JE, Shank B, Solin LJ, Wesson M: Tolerance of normal tissue to therapeutic irradiation. Int J Radiat Oncol Biol Phys 1991, 21:109-122.
• [13]Krämer M, Jäkel O, Haberer T, Kraft G, Schardt D, Weber U: Treatment planning for heavy-ion radiotherapy: physical beam model and dose optimization. Phys Med Biol 2000, 45:3299-3317.
• [14]ICRU: Report 78 Prescribing, Recording, and Reporting Proton-Beam Therapy. Bethesda, Maryland, USA: International Commission on Radiation Units and Measurements; 2007.
• [15]Paddick I: A simple scoring ratio to index the conformity of radiosurgical treatment plans. J Neurosurg 2000, 93(Suppl 3):219-222.
• [16]R Core Team: A Language and Environment for Statistical Computing. 2012. http://www.R-project.org webcite
• [17]Mayo C, Martel MK, Marks LB, Flickinger J, Nam J, Kirkpatrick J: Radiation dose-volume effects of optic nerves and chiasm. Int J Radiat Oncol Biol Phys 2010, 76:S28-S35.
• [18]Mayo C, Yorke E, Merchant TE: Radiation associated brainstem injury. Int J Radiat Oncol Biol Phys 2010, 76:S36-S41.
• [19]Merchant TE, Hua CH, Shukla H, Ying X, Nill S, Oelfke U: Proton versus photon radiotherapy for common pediatric brain tumors: comparison of models of dose characteristics and their relationship to cognitive function. Pediatr Blood Cancer 2008, 51:110-117.
• [20]Gondi V, Tome WA, Mehta MP: Why avoid the hippocampus? A comprehensive review. Radiother Oncol 2010, 97:370-376.
• [21]Blomstrand M, Brodin NP, Munck Af Rosenschold P, Vogelius IR, Sanchez Merino G, Kiil-Berthlesen A, Blomgren K, Lannering B, Bentzen SM, Bjork-Eriksson T: Estimated clinical benefit of protecting neurogenesis in the developing brain during radiation therapy for pediatric medulloblastoma. Neuro Oncol 2012, 14:882-889.
• [22]Merchant TE, Kiehna EN, Li C, Shukla H, Sengupta S, Xiong X, Gajjar A, Mulhern RK: Modeling radiation dosimetry to predict cognitive outcomes in pediatric patients with CNS embryonal tumors including medulloblastoma. Int J Radiat Oncol Biol Phys 2006, 65:210-221.
• [23]Diallo I, Haddy N, Adjadj E, Samand A, Quiniou E, Chavaudra J, Alziar I, Perret N, Guerin S, Lefkopoulos D, de Vathaire F: Frequency distribution of second solid cancer locations in relation to the irradiated volume among 115 patients treated for childhood cancer. Int J Radiat Oncol Biol Phys 2009, 74:876-883.
• [24]Galloway TJ, Indelicato DJ, Amdur RJ, Swanson EL, Smith AA, Marcus RB Jr: Second tumors in pediatric patients treated with radiotherapy to the central nervous system. Am J Clin Oncol 2012, 35:279-283.
• [25]McGowan SE, Burnet NG, Lomax AJ: Treatment planning optimisation in proton therapy. Br J Radiol 2013, 86:20120288.