skip to main content

Optimizing Dose Distribution with Direct Aperture Optimization: A MatRad-Based Analysis

*Fajar Miraz Fauzi orcid scopus  -  Nuclear Physics and Biophysics Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Bandung, Indonesia, Indonesia
Siti Mutmainnah orcid  -  Nuclear Physics and Biophysics Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Bandung, Indonesia, Indonesia
Rio Rizky Rahmadani  -  Nuclear Physics and Biophysics Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Bandung, Indonesia, Indonesia
Freddy Haryanto orcid scopus  -  Nuclear Physics and Biophysics Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Bandung, Indonesia, Indonesia
Received: 17 Nov 2025; Revised: 9 Aug 2026; Accepted: 10 Aug 2026; Available online: 31 Aug 2026; Published: 31 Aug 2026.

Citation Format:
Abstract

Advanced optimization algorithms like Direct Aperture Optimization (DAO) are integral to modern radiotherapy, yet research is often hindered by the limited accessibility of commercial Treatment Planning Systems. Open-source platforms like matRad provide a vital framework for such investigations. This study evaluates the dosimetric impact of DAO activation and its interplay with varying bixel resolutions (5×5 to 10×10 mm²) using matRad for a liver cancer case. Twelve treatment plans were generated and calculated using the ompMC Monte Carlo engine. Initial verification yielded a 3.14% mean relative statistical uncertainty, indicating that the stochastic uncertainty was relatively small compared with the dosimetric differences investigated. Twelve plans were assessed using Dose Volume Histograms (DVHs), Conformity Index (CI), and Homogeneity Index (HI). Results showed DAO significantly reduced stomach dose (e.g., 6.33% at 5×5 mm²; p=0.031). At 5×5 mm², heart and liver mean doses decreased by 7.15% and 1.83% respectively, though these changes were resolution-dependent and statistically non-significant. For targets, DAO at 5×5 mm² caused minor, non-significant mean dose increases for the GTV (1.3%), CTV (1.01%), and PTV (0.77%). Conversely, while maintaining target coverage, DAO activation produced a statistically significant degradation in dose conformity and homogeneity across all bixel sizes (p=0.031). These findings highlight an inherent optimization trade-off that DAO prioritizes steep dose gradients for maximal OAR protection at the expense of minor internal target dose heterogeneity. This study establishes matRad as an effective environment for elucidating optimization behaviors in radiotherapy planning.

Note: This article has supplementary file(s).

Fulltext View|Download |  Research Results
Result of DVH for All Models
Subject DVH
Type Research Results
  Download (807KB)    Indexing metadata
 Research Results
Result of Isodose for All Models
Subject Isodose
Type Research Results
  Download (2MB)    Indexing metadata
Email colleagues
Keywords: Bixel; Direct Aperture Optimization; Dosimetry; MatRad; Treatment Planning System

Article Metrics:

Article Info
Section: Articles
Language : EN
  1. D. Sanchez-Parcerisa and J. Udías, "Teaching treatment planning for protons with educational open-source software: Experience with FoCa and MatRad," J. Appl. Clin. Med. Phys., vol. 19, no. 4, pp. 302–306, 2018, doi: 10.1002/acm2.12326
  2. L. Fu, P. Liu, X. Yang, L. Xiao, C. Long, Q. Liao, C. Mei, and J. Liu, "Dosimetric comparison of three sequential intensity-modulated radiotherapy planning methods in the Monaco system for postoperative left-sided breast cancer: A planning study," J. Radiat. Res. Appl. Sci., vol. 19, no. 1, p. 102103, 2026, doi: 10.1016/j.jrras.2025.102103
  3. H. P. Wieser, N. Wahl, H. S. Gabryś, L. R. Müller, G. Pezzano, J. Winter, S. Ulrich, L. Burigo, O. Jäkel, and M. Bangert, “MatRad-an open-source treatment planning toolkit for educational purposes” Med. Phys. Int. J., vol. 6, no. 1, pp. 119-127, 2018. [Online]. Available: http://mpijournal.org/pdf/2018-01/mpi-2018-01-p119.pdf. Accessed: Nov. 17, 2025
  4. D. Wu, A. Eldib, L. Chen, and C. C. Ma, "MLC leaf adjustment for direct-aperture optimization treatment planning," Mathews J. Cancer Sci., vol. 10, no. 1, p. 50, 2025, doi: 10.30654/mjcs.10050
  5. Y. Zhang and M. Merritt, "Fluence map optimization in IMRT cancer treatment planning and a geometric approach," in Multiscale Optimization Methods and Applications, pp. 205–227, 2006, doi: 10.1007/0-387-29550-x_8
  6. M. P. Milette and K. Otto, "Maximizing the potential of direct aperture optimization through collimator rotation," Med. Phys., vol. 34, no. 4, pp. 1431–1438, 2007, doi: 10.1118/1.2712574
  7. X. Zhu, T. Cullip, G. Tracton, X. Tang, J. Lian, J. Dooley, and S. X. Chang, "Direct aperture optimization using an inverse form of back-projection," J. Appl. Clin. Med. Phys., vol. 15, no. 2, pp. 50–59, 2014, doi: 10.1120/jacmp.v15i2.4545
  8. D. L. Craft, T. F. Halabi, H. A. Shih, and T. R. Bortfeld, "Approximating convex pareto surfaces in multiobjective radiotherapy planning," Med. Phys., vol. 33, no. 9, pp. 3399–3407, 2006, doi: 10.1118/1.2335486
  9. J. Markman, D. A. Low, A. W. Beavis, and J. O. Deasy, "Beyond bixels: generalizing the optimization parameters for intensity modulated radiation therapy," Med. Phys., vol. 29, no. 10, pp. 2298–2304, 2002, doi: 10.1118/1.1508799
  10. G. Redler, E. Pearson, X. Liu, I. Gertsenshteyn, B. Epel, C. Pelizzari, B. Aydogan, R. Weichselbaum, H. J. Halpern, and R. D. Wiersma, "Small animal IMRT using 3D-printed compensators" Int. J. Radiat. Oncol. Biol. Phys., vol. 110, no. 2, pp. 551-565, 2021, doi: 10.1016/j.ijrobp.2020.12.028
  11. ESTRO, “Resource sharing: Open-source software & development in radiotherapy.” [Online]. Available: https://www.estro.org/Workshops/ESTRO-Physics-Workshop-2024/Resource-sharing-open-source-software-development. Accessed: Nov. 17, 2025
  12. N. Wahl, "Introduction to MatRad," presentation, 2022. [Online]. Available: https://indico.cern.ch/event/1161021/contributions/4876552/attachments/2475998/4249768/matRad_Introduction.pdf. Accessed: Nov. 17, 2025
  13. S. Wuyckens, D. Dasnoy, G. Janssens, V. Hamaide, M. Huet, E. L. Lo¨yen, G. Rotsart De Hertaing, B. Macq, E. Sterpin, J. Lee, K. Souris, and S. Deffet, "OpenTPS -- Open-source treatment planning system for research in proton therapy," arXiv preprint arXiv:2303.00365, 2023. [Online]. Available: https://arxiv.org/abs/2303.00365. Accessed: Nov. 17, 2025
  14. MathWorks, “Developing MatRad, an open-source dose calculation and optimization toolkit for radiation therapy planning.” [Online]. Available: https://uk.mathworks.com/company/technical-articles/developing-matrad-an-open-source-dose-calculation-and-optimization-toolkit-for-radiation-therapy-planning.html. Accessed: Nov. 17, 2025
  15. R. Michel, I. Françoise, P. Laure, M. Anouchka, P. Guillaume, and K. Sylvain, "Dose to organ at risk and dose prescription in liver SBRT," Rep. Pract. Oncol. Radiother., vol. 22, no. 2, pp. 96–102, 2017, doi: 10.1016/j.rpor.2017.03.001
  16. S. H. Kim, M. K. Kang, J. W. Yea, S. K. Kim, J. H. Choi, and S. A. Oh, "The impact of beam angle configuration of intensity-modulated radiotherapy in the hepatocellular carcinoma," Radiat. Oncol. J., vol. 30, no. 3, pp. 146-151, 2012, doi: 10.3857/roj.2012.30.3.146
  17. N. Khaledi, C. Hayes, L. Belshaw, M. Grattan, R. Khan, and J. L. Gräfe, "Treatment planning with a 2.5 MV photon beam for radiation therapy," J. Appl. Clin. Med. Phys., vol. 23, no. 12, p. e13811, 2022, doi: 10.1002/acm2.13811
  18. M. Wu, J. Jin, Z. Li, F. Kong, Y. He, L. Liu, W. Yang, and X. Xu, "Influence of beamlet width on dynamic IMRT plan quality in nasopharyngeal carcinoma," PeerJ, vol. 10, p. e13748, 2022, doi: 10.7717/peerj.13748
  19. L. B. Marks, E. D. Yorke, A. Jackson, R. K. Ten Haken, L. S. Constine, A. Eisbruch, S. M. Bentzen, J. Nam, and J. O. Deasy, "Use of normal tissue complication probability models in the clinic," Int. J. Radiat. Oncol. Biol. Phys., vol. 76, no. 3, suppl., pp. S10-S19, 2010, doi: 10.1016/j.ijrobp.2009.07.1754
  20. E. Y.-H. Chuang, C.-H. Hsieh, P.-W. Shueng, C.-X. Hsu, D.-Y. Kuo, Y.-F. Lu, H.-P. Yeh, and P.-Y. Hou, "Accelerated partial breast irradiation delivered with helical tomotherapy: Dosimetry and volumetric predictors of ipsilateral breast dose," Cancers, vol. 18, no. 13, p. 2122, 2026, doi: 10.3390/cancers18132122
  21. International Commission on Radiation Units and Measurements (ICRU), “ICRU report 62: prescribing, recording and reporting photon beam therapy (supplement to ICRU report 50).” 1999. [Online]. Available: https://www.icru.org/report/prescribing-recording-and-reporting-photon-beam-therapy-report-62. Accessed: Nov. 17, 2025
  22. W. Small, W. R. Bosch, M. M. Harkenrider, J. B. Strauss, N. Abu-Rustum, K. V. Albuquerque, S. Beriwal, C. L. Creutzberg, P. J. Eifel, B. A. Erickson, A. W. Fyles, C. L. Hentz, A. Jhingran, A. H. Klopp, C. A. Kunos, L. K. Mell, L. Portelance, M. E. Powell, A. N. Viswanathan, J. H. Yacoub, C. M. Yashar, K. A. Winter, and D. K. Gaffney, "NRG oncology/RTOG consensus guidelines for delineation of clinical target volume for intensity modulated pelvic radiation therapy in postoperative treatment of endometrial and cervical cancer: an update," Int. J. Radiat. Oncol. Biol. Phys., vol. 109, no. 2, pp. 413–424, 2021, doi: 10.1016/j.ijrobp.2020.08.061
  23. B. Goswami, R. K. Jain, S. Yadav, S. Kumar, S. Oommen, S. Manocha, and G. K. Jadhav, "A dosimetric study of volumetric arc modulation with rapidarc versus intensity-modulated radiotherapy in cervical cancer patients," Journal of Clinical And Diagnostic Research, vol. 15, no. 5, pp. XC01-XC05, 2021, doi: 10.7860/jcdr/2021/48635.14863
  24. T. Kataria, K. Sharma, V. Subramani, K. Karrthick, and S. Bisht, "Homogeneity index: An objective tool for assessment of conformal radiation treatments," J. Med. Phys., vol. 37, no. 4, pp. 207-213, 2012, doi: 10.4103/0971-6203.103606
  25. L. Feuvret, G. Noël, J.-J. Mazeron, and P. Bey, "Conformity index: A review," Int. J. Radiat. Oncol. Biol. Phys., vol. 64, no. 2, pp. 333–342, 2006, doi: 10.1016/j.ijrobp.2005.09.028
  26. E. Shaw, R. Kline, M. Gillin, L. Souhami, A. Hirschfeld, R. Dinapoli, and L. Martin, "Radiation therapy oncology group: Radiosurgery quality assurance guidelines," Int. J. Radiat. Oncol. Biol. Phys., vol. 27, no. 5, pp. 1231–1239, 1993, doi: 10.1016/0360-3016(93)90548-A
  27. S. Kwak, "Are only p-values less than 0.05 significant? A p-value greater than 0.05 is also significant!," J. Lipid Atheroscler., vol. 12, no. 2, pp. 89-95, 2023, doi: 10.12997/jla.2023.12.2.89
  28. J. Sundström, "Scenario dose calculation for robust optimization in proton therapy treatment planning," Master’s thesis, Lund University, Sweden, 2021, [Online]. Available: https://lup.lub.lu.se/student-papers/search/publication/9059444
  29. D. M. Shepard, M. A. Earl, X. A. Li, S. Naqvi, and C. Yu, "Direct aperture optimization: A turnkey solution for step‐and‐shoot IMRT," Med. Phys., vol. 29, no. 6, pp. 1007–1018, 2002, doi: 10.1118/1.1477415
  30. M. Broderick, M. Leech, and M. Coffey, "Direct aperture optimization as a means of reducing the complexity of intensity modulated radiation therapy plans," Radiation Oncology, vol. 4, p. 8, 2009, doi: 10.1186/1748-717x-4-8
  31. D. Nguyen, D. O’Connor, D. Ruan, and K. Sheng, "Deterministic direct aperture optimization using multiphase piecewise constant segmentation," Med. Phys., vol. 44, no. 11, pp. 5596–5609, 2017, doi: 10.1002/mp.12529
  32. I. Paddick, "A simple scoring ratio to index the conformity of radiosurgical treatment plans. Technical note," J. Neurosurg., vol. 93, suppl. 3, pp. 219–222, 2000, doi: 10.3171/jns.2000.93.supplement
  33. D. Craft, P. Süss, and T. Bortfeld, "The tradeoff between treatment plan quality and required number of monitor units in intensity-modulated radiotherapy," Int. J. Radiat. Oncol. Biol. Phys., vol. 67, no. 5, pp. 1596–1605, 2007, doi: 10.1016/j.ijrobp.2006.11.034

Last update:

No citation recorded.

Last update:

No citation recorded.