Dosimetric Comparison of The Effects of Different Treatment Plan Techniques on Reduction in Critical Organs in Whole Brain Radiotherapy Application

Öz

Different radiotherapy treatment techniques can be used in whole-brain radiotherapy (WBRT). This study aims to investigate the dosimetric advantages of the anterior isocenteric (AI) technique which is produced as an alternative to the central isocentric (CI) technique. 25 whole brain patients were included in this retrospective study. Plans were made with two treatment techniques for each patient. One central isocenter (CI) was made using a conventional helmet field (HF) to center the whole brain, which is the isocenter of the target volume. An automatic margin of 5 mm was given to the planning target volume (PTV) with multileaf collimators (MLC) for both plans. For CI and AI techniques, a total dose of 30 Gy was given in 10 fractions with 6 MV photon energy. The two planning techniques were compared dosimetrically. The dose homogeneity index (DHI) had lower values in the AI plan according to CI plans significantly (p=0.049). There was a 6,57% difference between CI and AI planning techniques for the maximum dose of the right lens. For the minimum dose and mean dose AI plans significantly had lower values according to the CI plan (p=0.001 and p=0.028 respectively). In this dosimetric study, we found that the AI treatment technique for WBRT was superior to the CI technique for DHI and organs at risk. We recommended to use the AI technique, especially to better protect organs at risk in WBRT.

Anahtar Kelimeler

• Anterior isocenter
• brain
• radiotherapy
• central isocenter

Kaynakça

1. 1]. Yu, J., S. Shiao, and J. Knisely, 2083: A Dosimetric Evaluation of Conventional Helmet Field Irradiation Versus Two Field Intensity Modulated Radiation Therapy Technique. International Journal of Radiation Oncology, Biology, Physics, 2006. 66(3): p. S255-S256.
2. [2]. Yu, J., S. Shiao, and J. Knisely, 2083: A Dosimetric Evaluation of Conventional Helmet Field Irradiation Versus Two Field Intensity Modulated Radiation Therapy Technique. International Journal of Radiation Oncology, Biology, Physics, 2006. 66(3): p. S255-S256.
3. [3]. Fujita, H., et al., Improvement of dose homogeneity with irregular surface compensator in whole brain radiotherapy. Journal of Radiotherapy in Practice, 2016. 15(3): p. 269-275.
4. [4]. Murray, K.J., et al., A randomized phase III study of accelerated hyperfractionation versus standard in patients with unresected brain metastases: a report of the Radiation Therapy Oncology Group (RTOG) 9104. International journal of radiation oncology, biology, physics, 1997. 39(3): p. 571-574.
5. [5]. Gul OV. Experimental evaluation of out-of-field dose for different high-energy electron beams and applicators used in external beam radiotherapy. Radiation Physics and Chemistry. 2024;215.
6. [6]. Gul OV, Duzova M. Effect of different CTV shrinkage and skin flash margins on skin dose for left chest wall IMRT: A dosimetric study. Radiation Physics and Chemistry. 2024;216.
7. [7]. Jones, D., ICRU report 50—prescribing, recording and reporting photon beam therapy. 1994, Wiley Online Library.
8. [8]. Kanyilmaz, G., Baş-boyun kanserlerinde radyoterapi planlamasinda 18f-fdg pet/bt kullanimi. Mevlana Tıp Bilimleri Dergisi, 2021. 1(3): p. 85-88.

9. [9]. Lerch, I.A. and J. Newall, Adjustable compensators for whole-brain irradiation. Radiology, 1979. 130(2): p. 529-532.
10. [10]. Keall, P., et al., The development and investigation of a prototype three-dimensional compensator for whole brain radiation therapy. Physics in Medicine & Biology, 2008. 53(9): p. 2267.
11. [11]. Goyal, S., et al., Improvement in dose homogeneity with electronic tissue compensation over IMRT and conventional RT in whole brain radiotherapy. Radiotherapy and Oncology, 2008. 88(2): p. 196-201.
12. [12]. Gondi, V., et al., Hippocampal-sparing whole-brain radiotherapy: a “how-to” technique using helical tomotherapy and linear accelerator–based intensity-modulated radiotherapy. International Journal of Radiation Oncology* Biology* Physics, 2010. 78(4): p. 1244-1252.
13. [13]. Marsh, J., et al., Sparing of the hippocampus and limbic circuit during whole brain radiation therapy: a dosimetric study using helical tomotherapy. Journal of Medical Imaging and Radiation Oncology, 2010. 54(4): p. 375-382.
14. [14]. van Kesteren, Z., et al., A practical technique to avoid the hippocampus in prophylactic cranial irradiation for lung cancer. Radiotherapy and Oncology, 2012. 102(2): p. 225-227.
15. [15]. Rong, Y., et al., Dosimetric evaluation of intensity-modulated radiotherapy, volumetric modulated arc therapy, and helical tomotherapy for hippocampal-avoidance whole brain radiotherapy. PloS one, 2015. 10(4): p. e0126222.
16. [16]. Kao, J., et al., Tumor directed, scalp sparing intensity modulated whole brain radiotherapy for brain metastases. Technology in cancer research & treatment, 2015. 14(5): p. 547-555.
17. [17]. Gong, Y., et al., Conventionally-fractionated image-guided intensity modulated radiotherapy (IG-IMRT): a safe and effective treatment for cancer spinal metastasis. Radiat Oncol, 2008. 3: p. 11.
18. [18]. Narita, Y. and S. Shibui, Strategy of surgery and radiation therapy for brain metastases. International Journal of Clinical Oncology, 2009. 14(4): p. 275-280.
19. [19]. DeAngelis, L.M., J.-Y. Delattre, and J.B. Posner, Radiation‐induced dementia in patients cured of brain metastases. Neurology, 1989. 39(6): p. 789-789.
20. [20]. Twijnstra, A., et al., Neurotoxicity of prophylactic cranial irradiation in patients with small cell carcinoma of the lung. European Journal of Cancer and Clinical Oncology, 1987. 23(7): p. 983-986.
21. [21]. Laukkanen, E., et al., The role of prophylactic brain irradiation in limited stage small cell lung cancer: clinical, neuropsychologic, and CT sequelae. International Journal of Radiation Oncology* Biology* Physics, 1988. 14(6): p. 1109-1117.
22. [22]. Yavaş, G., et al., Dosimetric comparison of two different whole brain radiotherapy techniques in patients with brain metastases: How to decrease lens dose? International Journal of Radiation Research, 2014.
23. [23]. Andic, F., et al., Dosimetric comparison of conventional helmet-field whole-brain irradiation with three-dimensional conformal radiotherapy: dose homogeneity and retro-orbital area coverage. The British Journal of Radiology, 2009. 82(974): p. 118-122.
24. [24]. Hall, E.J. and C.-S. Wuu, Radiation-induced second cancers: the impact of 3D-CRT and IMRT. International Journal of Radiation Oncology* Biology* Physics, 2003. 56(1): p. 83-88.
25. [25]. Hall, E.J., Intensity-modulated radiation therapy, protons, and the risk of second cancers. International Journal of Radiation Oncology* Biology* Physics, 2006. 65(1): p. 1-7.