Gamma Knife radiosurgery for vestibular schwannomas: Evaluation of planning using the sphericity degree of the target volume


Autoři: Crystian Wilian Chagas Saraiva aff001;  Simone Coutinho Cardoso aff003;  Daniela Piai Groppo aff004;  Antônio Afonso Ferreira De Salles aff002;  Luiz Fernando de Ávila aff005;  Luiz Antonio Ribeiro da Rosa aff001
Působiště autorů: Instituto de Radioproteção e Dosimetria / Comissão Nacional de Energia Nuclear–IRD / CNEN, Rio de Janeiro, Brazil aff001;  Associação do Sanatório Sírio—Hospital do Coração–HCor, São Paulo, Brazil aff002;  Universidade Federal do Rio de Janeiro–Instituto de Física–UFRJ, Rio de Janeiro, Brazil aff003;  Instituto de Pesquisa Energéticas e Nucleares–IPEN / CNEN, São Paulo, Brazil aff004;  Universidade Estadual de Campinas, Faculdade de Tecnologia–UNICAMP, Limeira, Brazil aff005
Vyšlo v časopise: PLoS ONE 15(1)
Kategorie: Research Article
prolekare.web.journal.doi_sk: https://doi.org/10.1371/journal.pone.0225638

Souhrn

Introduction

This study explores the possibility of a relationship between the sphericity degree of a target volume with the dose distribution. This relationship is evaluated based on the ratio isodose volume / target volume (IV/TV) and the metrics coverage, i.e., selectivity, gradient index, conformity index and mean dose when planning radiosurgery for vestibular schwannoma.

Methods

Sphericity degree (φ) was calculated for each target volume (TV) of 64 patients who underwent stereotactic radiosurgery (SRS) for vestibular schwannoma. The calculation of this parameter was developed using the theoretical definition for operational sphericity φ = VP/VCS. The values found are evaluated considering the following metrics:—Coverage (C), selectivity (S), gradient index (GI), Paddick conformity index (CIPaddick) and dose distribution (IV/TV). The planning was also carried out considering a spherical target volume defined in a spherical phantom. The spherical volume is the same as the target used in the treatment plan. The planning of the spherical target was considered as a reference plan to evaluate the dose distribution inside and outside the volume.

Results

It was possible to observe that the majority of target volumes has (ϕ) around 0,66–0,77, corresponding to 54,7% of the total. Considering the mean values for metrics, the results are: C = 0,98, S = 0,78, GI = 3,11 and CI = 0,81. The dose distribution was equivalent for treatment plans and reference plans. Quantitative analysis for IV/TV shows that these values are higher than 30% for treatment plans where shot density is large.

Conclusion

This study demonstrates that de sphericity degree (φ) can be related to the dose distribution (IV/TV). Therefore the sphericity degree is a good parameter to evaluate the dose distribution of a plan for vestibular schwannoma treatment, considering the reference plan as being a spherical target using a leksell gamma knife® perfexion (LGKP). This study shows that the sphericity degree offers important information of the dose distribution outside and inside the target volume. This is not evaluated by the other parameters already implemented as metric to analyzing the GKP plans.

Klíčová slova:

Cancer treatment – Equipment – Software tools – Quantitative analysis – Gamma Knife radiosurgery – Stereotactic radiosurgery – Radiosurgery – Physicists


Zdroje

1. Rykaczewski M, Zabek M. A meta-analysis of treatment of vestibular schwannoma using Gamma Knife radiosurgery. Contemp Oncol (Pozn). 2014; 18 (1): 60–66. doi: 10.5114/wo.2014.39840 24876823

2. Wu Q J, Jitprapaikulsarn S, Mathayomchan B, Einstein D, Maciunas R J, Pillai, et al. Clinical Evaluation of a Gamma Knife Inverse Planning System. Radiosurgery. Basel, Karger. 2004; (5): 260–266. doi: 10.1159/000078126

3. Shaw E, Kline R, Gillin M, Souhami L, Hirschfeld A, Dinapoli R, et al. Radiation Therapy Oncology Group: Radiosurgery quality assurance guidelines. Int J Radiat Oncol Biol Phys. 1993; (27): 1231–1239. doi: 10.1016/0360-3016(93)90548-a 8262852

4. Wu A. Physics and dosimetry of the gamma knife. Neurosurg Clin North Am. 1992; (3):35–50. doi: 10.1016/s1042-3680(18)30681-8

5. Padick I, Lippitz B. A simple dose gradient measurement tool to complement the conformity index. J Neurosurg (Suppl). 2006: (105):194–201. doi: 10.3171/sup.2006.105.7.194 18503356

6. Wadell H. Sphericity and roundness of rock particles. The Journal of Geology. 1932: 41(3):310–331. doi: 10.1086/623964

7. Inverse planning in Leksell GammaPlan® 10. Article no. 018880.02 september 2011 Elekta

8. A new TMR dose algorithm in Leksell GammaPlan®. Article no. 1021357.00 july 2011 Elekta

9. Padick I. A simple scoring ratio to index the conformity of radiosurgical treatment plans. J Neurosurg (Suppl3). 2000: (93):219–222. doi: 10.3171/jns.2000.93.supplement

10. Novotny J, Bhatnagar J P, Quader M A, Bednarz G, Lunsford L D, Huq M S. Measurement of relative output factors for the 8 and 4 mm collimators of Leksell Gamma Knife Perfexion by film dosimetry. Med. Phys. 2009: 36 (5): 1768–1774. doi: 10.1118/1.3113904 19544795

11. Liscak R, Josepf N Jr, Urgosik D, Vladyka V, Simonová G. Statistical Analysis of Risk Factors after Gamma Knife Radiosurgery of Acoustic Neurinomas. Radiosurgery. Basel, Karger. 2000; (3): 205–213. doi: 10.1159/000062315

12. Osmancikova P, Novotny J, Solc J, Pipek J. Comparison of the Convolution algorithm with TMR10 for Leksell Gamma knife and dosimetric verification with radiochromic gel dosimeter. J Appl Clin Med Phys. 2017; 25: 1–7. doi: 10.1002/acm2.12238 29226607

13. Nore´n G, Greitz D, Hirsch A, Lax I. Gamma knife surgery in acoustic tumours. Acta Neurochir (Wien). 1993; (58): 104–107. doi: 10.1007/978-3-7091-9297-9_24 8109269

14. Johnson P B, Monterroso M I, Yang F, Mellon E. Optimization of the prescription isodose line for Gamma Knife radiosurgery using the shot within shot technique. Radiation Oncology, 2017: 12(187) doi: 10.1186/s13014-017-0919-4 29178912


Článok vyšiel v časopise

PLOS One


2020 Číslo 1
Najčítanejšie tento týždeň
Najčítanejšie v tomto čísle
Kurzy

Zvýšte si kvalifikáciu online z pohodlia domova

Aktuální možnosti diagnostiky a léčby litiáz
nový kurz
Autori: MUDr. Tomáš Ürge, PhD.

Všetky kurzy
Prihlásenie
Zabudnuté heslo

Zadajte e-mailovú adresu, s ktorou ste vytvárali účet. Budú Vám na ňu zasielané informácie k nastaveniu nového hesla.

Prihlásenie

Nemáte účet?  Registrujte sa