Prog Med Phys.  2022 Dec;33(4):150-157. 10.14316/pmp.2022.33.4.150.

Monte Carlo Algorithm-Based Dosimetric Comparison between Commissioning Beam Data across Two Elekta Linear Accelerators with Agility ^TM MLC System

• Yu GB
• Choi CH
• Kim Ji
• Cho JD
• Yoon E
• Choun HJ
• Choi J
• Kim S
• Kim Y
• Oh DH
• Lee H
• Yoo L
• Chun M

• KMID: 2537884
• DOI: http://doi.org/10.14316/pmp.2022.33.4.150

Abstract

Purpose
Elekta synergy ^® was commissioned in the Seoul National University Veterinary Medical Teaching Hospital. Recently, Chung-Ang University Gwang Myeong Hospital commissioned Elekta Versa HD TM . The beam characteristics of both machines are similar because of the same Agility TM MLC Model. We compared measured beam data calculated using the Elekta treatment planning system, Monaco ^® , for each institute.
Methods
Beam of the commissioning Elekta linear accelerator were measured in two independent institutes. After installing the beam model based on the measured beam data into the Monaco ^® , Monte Carlo (MC) simulation data were generated, mimicking the beam data in a virtual water phantom. Measured beam data were compared with the calculated data, and their similarity was quantitatively evaluated by the gamma analysis.
Results
We compared the percent depth dose (PDD) and off-axis profiles of 6 MV photon and 6 MeV electron beams with MC calculation. With a 3%/3 mm gamma criterion, the photon PDD and profiles showed 100% gamma passing rates except for one inplane profile at 10 cm depth from VMTH. Gamma analysis of the measured photon beam off-axis profiles between the two institutes showed 100% agreement. The electron beams also indicated 100% agreement in PDD distributions. However, the gamma passing rates of the off-axis profiles were 91%–100% with a 3%/3 mm gamma criterion.
Conclusions
The beam and their comparison with MC calculation for each institute showed good performance. Although the measuring tools were orthogonal, no significant difference was found.

Keyword

Agility multi-leaf collimator; Commissioning beam data; Profile measurement; Percent depth dose measurement; Monaco Monte Carlo algorithm

Figure

• 

  Fig. 1 Horizontal (left) and vertical (right) positioning of the ion chamber (PTW TRUFIX® Detector Positioning System).

• 

  Fig. 2 Photon beams (6 MV) with field size of 10×10 cm2. Measured distributions (green) were compared with the MC simulated distributions (blue) for each institute (CAUGH and VMTH) and the gamma index per point (red) was overlaid. From the top left, PDD of (a) CAUGH and (b) VMTH, inplane and crossplane profiles at a depth of Dmax of (c, e) CAUGH and (d, f) VMTH beam data, and those at 10 cm depth of (g, i) CAUGH and (h, j) VMTH beam data. CAUGH, Chung-Ang University Gwang Myeong Hospital; MC, Monte Carlo; PDD, percent depth dose; VMTH, Seoul National University Veterinary Medical Teaching Hospital.

• 

  Fig. 3 Electron beams (6 MeV) with a 10×10 cm2 applicator. Measured distributions (green) were compared with the MC simulated distributions (blue) for each institute (CAUGH and VMTH) and the gamma index per point (red) was overlaid. From the top left, PDD of (a) CAUGH and (b) VMTH, inplane and crossplane profiles at a depth of 1 cm of (c, e) CAUGH and (d, f) VMTH, respectively. CAUGH, Chung-Ang University Gwang Myeong Hospital; MC, Monte Carlo; VMTH, Seoul National University Veterinary Medical Teaching Hospital.

Reference

References

1. Meyers SM, Balderson MJ, Létourneau D. 2019; Evaluation of Elekta Agility multi-leaf collimator performance using statistical process control tools. J Appl Clin Med Phys. 20:100–108. DOI: 10.1002/acm2.12660. PMID: 31199568. PMCID: PMC6612682.

2. Kabat CN, Defoor DL, Myers P, Kirby N, Rasmussen K, Saenz DL, et al. 2019; Evaluation of the Elekta Agility MLC performance using high-resolution log files. Med Phys. 46:1397–1407. DOI: 10.1002/mp.13374. PMID: 30702748.

3. Gholampourkashi S, Cygler JE, Belec J, Vujicic M, Heath E. 2019; Monte Carlo and analytic modeling of an Elekta Infinity linac with Agility MLC: investigating the significance of accurate model parameters for small radiation fields. J Appl Clin Med Phys. 20:55–67. DOI: 10.1002/acm2.12485. PMID: 30408308. PMCID: PMC6333188.

4. Can S, Karaçetin D, Meriç N. 2022; Beam modeling and commissioning for Monte Carlo photon beam on an Elekta Versa HD LINAC. Appl Radiat Isot. 180:110054. DOI: 10.1016/j.apradiso.2021.110054. PMID: 34875475.

5. Paudel MR, Kim A, Sarfehnia A, Ahmad SB, Beachey DJ, Sahgal A, et al. 2016; Experimental evaluation of a GPU-based Monte Carlo dose calculation algorithm in the Monaco treatment planning system. J Appl Clin Med Phys. 17:230–241. DOI: 10.1120/jacmp.v17i6.6455. PMID: 27929496. PMCID: PMC5690498.

6. Narayanasamy G, Saenz D, Cruz W, Ha CS, Papanikolaou N, Stathakis S. 2016; Commissioning an Elekta Versa HD linear accelerator. J Appl Clin Med Phys. 17:179–191. DOI: 10.1120/jacmp.v17i1.5799. PMID: 26894351. PMCID: PMC5690217.

7. Kinoshita N, Oguchi H, Adachi T, Shioura H, Kimura H. 2018; Uncertainty in positioning ion chamber at reference depth for various water phantoms. Rep Pract Oncol Radiother. 23:199–206. DOI: 10.1016/j.rpor.2018.03.001. PMID: 29760594. PMCID: PMC5948320.

8. Tessier F, Kawrakow I. 2010; Effective point of measurement of thimble ion chambers in megavoltage photon beams. Med Phys. 37:96–107. DOI: 10.1118/1.3266750. PMID: 20175470.

9. Almond PR, Biggs PJ, Coursey BM, Hanson WF, Huq MS, Nath R, et al. 1999; AAPM's TG-51 protocol for clinical reference dosimetry of high-energy photon and electron beams. Med Phys. 26:1847–70. DOI: 10.1118/1.598691. PMID: 10505874.

10. Low DA, Harms WB, Mutic S, Purdy JA. 1998; A technique for the quantitative evaluation of dose distributions. Med Phys. 25:656–61. DOI: 10.1118/1.598248. PMID: 9608475.

11. Snyder JE, Hyer DE, Flynn RT, Boczkowski A, Wang D. 2019; The commissioning and validation of Monaco treatment planning system on an Elekta VersaHD linear accelerator. J Appl Clin Med Phys. 20:184–193. DOI: 10.1002/acm2.12507. PMID: 30525308. PMCID: PMC6333122.