Comparison and Evaluation of radiotherapy plans by multi leaf collimator types of Linear accelerator

선형가속기의 다엽콜리메이터 형태에 따른 치료계획 비교 평가

  • Lim, Ji Hye (Department of Radiation Oncology, Seoul National University Bundang Hospital) ;
  • Chang, Nam Joon (Department of Radiation Oncology, Seoul National University Bundang Hospital) ;
  • Seok, Jin Yong (Department of Radiation Oncology, Seoul National University Bundang Hospital) ;
  • Jung, Yun Ju (Department of Radiation Oncology, Seoul National University Bundang Hospital) ;
  • Won, Hui Su (Department of Radiation Oncology, Seoul National University Bundang Hospital) ;
  • Jung, Hae Youn (Department of Radiation Oncology, Seoul National University Bundang Hospital) ;
  • Choi, Byeong Don (Department of Radiation Oncology, Seoul National University Bundang Hospital)
  • 임지혜 (분당서울대학교병원 방사선종양학과) ;
  • 장남준 (분당서울대학교병원 방사선종양학과) ;
  • 석진용 (분당서울대학교병원 방사선종양학과) ;
  • 정윤주 (분당서울대학교병원 방사선종양학과) ;
  • 원희수 (분당서울대학교병원 방사선종양학과) ;
  • 정해윤 (분당서울대학교병원 방사선종양학과) ;
  • 최병돈 (분당서울대학교병원 방사선종양학과)
  • Published : 2018.12.29

Abstract

Purpose : An aim of this study was to compare the effect of multi leaf collimator(MLC) types for high dimension radiotherapy in treatment sites used clinically. Material and Method : 70 patients with lung cancer, spine cancer, prostate cancer, whole pelvis, head and neck, breast cancer were included in this study. High definition(HD) MLC of TrueBeam STx (Varian Medical system, Palo Alto, CA) and millenium(M) MLC of VitalBeam (Varian Medical system, Palo Alto, CA) were used. Radiotherapy plans were performed for each patient under same treatment goals with Eclipse (Version 13.7, Varian Palo Alto USA, CA). To compare the indicators of the radiotherapy plans, planning target volume(PTV) coverage, conformity index(CI), homogeneity index(HI), and clinical indicators for each treatment sites in normal tissues were evaluated. To evaluate low dose distribution, $V_{30%}$ values were compared according to MLC types. Additionally, length and volume of targets for each treatment sites were investigated. Result : In stereotatictic body radiotherapy(SBRT) plan for lung, the average value of PTV coverage was reduced by 0.52 % with HD MLC. With SBRT plan using HD MLC for spine, the average value of PTV coverage decreased by 0.63 % and maximum dose decreased by 1.13 %. In the test of CI and HI, the values in SBRT plan with HD MLC for spine were 1.144, 1.079 and the values using M MLC were 1.160, 1.092 in SBRT plan for lung, The dose evaluation of critical organ was reduced by 1.48 % in the ipsilateral lung mean dose with HD MLC. In prostate cancer volumetric modulated arc therapy(VMAT) with HD MLC, the mean dose and the $V_{30}$ of bladder and the mean dose and the $V_{25}$ of rectum were reduced by 0.53 %, 1.42 %, 0.97 %, and 0.69 %, respectively (p<0.05). The average value of heart mean dose was reduced by 0.83 % in breast cancer VMAT with M MLC. Other assessment indices for treatment sites showed no significant difference between treatment plans with two types of MLC. Conclusion : Using HD MLC had a positive impact on the PTV coverage and normal tissue sparing in usually short or small targets such as lung and spine SBRT and prostate VMAT. But, there was no significant difference in targets with long and large such as lung, head and neck, and whole pelvis for VMAT.

목 적 : 임상적으로 많이 시행하는 치료부위에 고차원 치료기법 적용 시 선형가속기에 장착된 다엽콜리메이터(Multi leaf collimator, MLC)의 형태가 치료계획에 미치는 영향을 연구해 보고자 한다. 대상 및 방법 : 본원에서 척추암, 폐암 정위적체부방사선치료(Stereotactic body radiation therapy, SBRT)를 받은 환자와 전립선암, 폐암, 두경부암, 전골반암, 유방암의 용적변조회전치료(Volumetric modulated arc therapy, VMAT)를 시행한 환자들을 부위별로 10명씩 총 70명 선정하였다. Truebeam STx(Varian Medical system, Palo Alto, CA)의 high definition MLC(HD MLC)와 Vitalbeam(Varian Medical system, Palo Alto, CA)에 장착된 millenium MLC(M MLC)를 사용하였고, 치료계획은 Eclipse(Version 13.7, Varian Palo Alto USA, CA)를 이용하여 동일한 조건으로 환자마다 각각 2개씩 수립하였다. MLC의 형태에 따른 치료계획을 평가하기 위해 PTV coverage, conformity index(CI), homogeneity index(HI)를 비교하였고, 정상조직은 각 부위별로 임상에서 사용하는 평가 지표를 분석하였으며, 정상조직에서 저 선량 영역을 비교하기 위하여 $V_{30%}$을 평가하였다. 추가적으로 각 부위별로 치료표적의 길이 및 체적을 조사하였다. 결 과 : PTV coverage는 HD MLC를 적용한 폐암 SBRT에서 평균선량이 0.52 %, 척추암 SBRT에서 평균 선량과 최대선량이 각각 0.68 %, 1.13 %로 M MLC에 비해 감소하였다. CI와 HI는 척추암 SBRT 치료계획에서 HD MLC가 1.144, 1.079로 M MLC의 1.160, 1.092 보다 낮은 수치를 나타냈다(p<0.05). 결정장기의 선량 평가는 폐암 SBRT 치료계획에서 치료받는 쪽 폐의 평균선량이 HD MLC에서 1.48 %로 낮아졌다. 전립선암 VMAT은 HD MLC를 적용한 치료계획에서 방광의 $V_{30}$과 평균선량이 0.53 %, 1.42 %, 직장의 $V_{25}$와 평균선량이 0.97 %, 0.69 %로 감소하였다(p<0.05). 유방암 VMAT은 오히려 HD MLC를 사용한 치료계획에서 심장의 평균선량이 0.83 %로 높아졌다. 다른 치료부위 평가지표들은 두 MLC를 적용한 치료계획 사이에 큰 차이를 보이지 않았다(p>0.05). 결 론 : 본 연구 결과 SBRT나 전립선암 VMAT과 같이 치료표적의 길이가 짧고 크기가 작은 경우 HD MLC를 사용하는 것이 PTV coverage 및 정상조직 보호 효과 면에서 다소 이점이 있는 것으로 나타났으나, 그 외 상대적으로 길고, 큰 폐암, 두경부암, 전골반암, 유방암 VMAT에서는 MLC의 형태가 치료계획에 미치는 영향은 크지 않았다.

Keywords

References

  1. Gupta, T., Agarwal, J., Jain, S., Phurailatpam, R., Kannan, S., Ghosh-Laskar, S., Prabhash, K. (2012). Three-dimensional conformal radiotherapy (3DCRT) versus intensity modulated radiation therapy (IMRT) in squamous cell carcinoma of the head and neck: a randomized controlled trial. Radiotherapy and Oncology, 104(3), 343-348 https://doi.org/10.1016/j.radonc.2012.07.001
  2. Park JM, Choi CH, Ha SW, Ye SJ.:(2011). The dosimetric effect of mixed-energy IMRT plans for prostate cancer. J Appl Clin Med Phys 12:35-63 https://doi.org/10.1120/jacmp.v12i1.3320
  3. Otto, K. (2008). Volumetric modulated arc therapy: IMRT in a single gantry arc. Medical physics, 35(1), 310-317
  4. Park, J. M., Park, S.-Y., Kim, J. H., Carlson, J., & Kim, J.-i. (2016). The effect of extremely narrow MLC leaf width on the plan quality of VMAT for prostate cancer. Radiation Oncology, 11(1), 85 https://doi.org/10.1186/s13014-016-0664-0
  5. Okunieff, P., Petersen, A. L., Philip, A., Milano, M. T., Katz, A. W., Boros, L., & Schell, M. C. (2006). Stereotactic body radiation therapy (SBRT) for lung metastases. Acta oncologica, 45(7), 808-817 https://doi.org/10.1080/02841860600908954
  6. Benedict SH, Yenice KM, Followill D, et al. Stereotactic body radiation therapy: the report of the AAPM Task Group 101. Med Phys. 2010;37(8):4078-101 https://doi.org/10.1118/1.3438081
  7. Lafond C, Chajon E, Devillers A, Louvel G, Toublanc S, Olivier M, et al. Impact of MLC leaf width on volumetric-modulated arc therapy planning for head and neck cancers. J Appl Clin Med Phys. 2013;14:4074
  8. Bergman, A. M., Gete, E., Duzenli, C., & Teke, T. (2014). Monte Carlo modeling of HD120 multileaf collimator on Varian TrueBeam linear accelerator for verification of 6X and 6X FFF VMAT SABR treatment plans. Journal of Applied Clinical Medical Physics, 15(3), 148-163 https://doi.org/10.1120/jacmp.v15i3.4686
  9. Ernst-Stecken A, Lambrecht U, Ganslandt O, Mueller R, Fahlbusch R, Sauer R, et al. Radiosurgery of small skull-baselesions, no advantage for intensity-modulated stereotactic radiosurgery versus conformal arc technique. Strahlenther Onkol 2005;181:336-44. https://doi.org/10.1007/s00066-005-1371-1
  10. D. S. Sharma, P. M. Dongre, V. Mhatre, and M. Heigrujam, "Physical and dosimetric characteristic of high-definition multileaf collimator (HDMLC) for SRS and IMRT," J. Appl. Clin. Med. Phys. 12, 142-160(2011) https://doi.org/10.1120/jacmp.v12i3.3475
  11. Younge, K. C., Kuchta, J. R., Mikell, J. K., Rosen, B., Bredfeldt, J. S., & Matuszak, M. M. (2017). The impact of a high-definition multileaf collimator for spine SBRT. Journal of Applied Clinical Medical Physics, 18(6), 97-103
  12. Wuu, C.-S., Kessel, J., & Xu, Y. (2009). 3-D dosimetric evaluation of 2.5 mm HD120(R) multileaf system for intensity modulated stereotactic radiosurgery using optical CT based polymer gel dosimetry. Paper presented at the Journal of Physics: Conference Series
  13. Van Kesteren, Z., Janssen, T., Damen, E., & van Vliet-Vroegindeweij, C. (2012). The dosimetric impact of leaf interdigitation and leaf width on VMAT treatment planning in Pinnacle: comparing Pareto fronts. Physics in Medicine & Biology, 57(10), 2943 https://doi.org/10.1088/0031-9155/57/10/2943
  14. Yang J, Tang G, Zhang P, Hunt M, Lim SB, LoSasso T, Mageras G. Dose calculation for hypofractionated volumetricmodulated arc therapy: approximating continuous arc delivery and tongue-andgroove modeling. J Appl Clin Med Phys. 2016 Mar 8;17(2):4989, Memorial Sloan Kettering Cancer Center, New York, NY
  15. French SB, Bhagroo S, Nazareth DP, Podgorsak MB. Adapting VMAT plans optimized for an HD120 MLC for delivery with a Millennium MLC. J Appl Clin Med Phys. 2017 Sep;18(5):143-151, Roswell Park Cancer Institute, Buffalo, NY https://doi.org/10.1002/acm2.12134
  16. Hong, C. S., Ju, S. G., Kim, M., Kim, J. i., Kim, J. M., Suh, T. S. Nam, H. (2014). Dosimetric effects of multileaf collimator leaf width on intensity-modulated radiotherapy for head and neck cancer. Medical physics, 41(2)
  17. Heath E and Seuntjens J. Development and validation of a BEAMnrc component module for accurate Monte Carlo modelling of the Varian dynamic Millennium multileaf collimator. Phys Med Biol. 2003;48(24):4045-63 https://doi.org/10.1088/0031-9155/48/24/004
  18. Borges C, Zarza-Moreno M, Heath E, Teixeira N, Vaz P. Monte Carlo modeling and simulations of the high definition (HD120) micro MLC and validation against measurements for a 6 MV beam. Med Phys. 2012;39(1):415-23
  19. Boyer A, Biggs P, Galvin J, et al. Basic applications of multileaf collimators: report of AAPM Task Group No 50. AAPM Report No. 72. Madison, WI: Medical Physics Publishing; 2001
  20. J. A. Tanyi, P. A. Summers, C. L. McCracken, Y. Chen, L. C. Ku, and M. Fuss, "Implications of a highdefinition multileaf collimator (HD-MLC) on treatment planning techniques for stereotactic body radiation therapy (SBRT): A planning study," Radiat. Oncol. 4, 22-28 (2009).10.1186/1748-717X-4-22
  21. Chae, S.-M., Lee, G. W., & Son, S. H. (2014). The effect of multileaf collimator leaf width on the radiosurgery planning for spine lesion treatment in terms of the modulated techniques and target complexity. Radiation Oncology, 9(1), 72 https://doi.org/10.1186/1748-717X-9-72