Dosimetric Study of Tissue Heterogeneity Correction for Breast Conformal Radiotherapy

Document Type : Original Paper


1 Specialist of Medical Physics (Radiotherapy Department)at Meet Ghammr Oncology Center,Ministry of Health.

2 Prof. of Medical physics ; Children’s Cancer Hospital&National Cancer Institute; Cairo University; Cairo Egypt.

3 Professor of Bio-Physics , Zagazig University, Egypt.

4 Consultant of Medical physics; children cancer Hospital, Egypt

5 Specialist of Medical Physics, National Cancer Institute (NCI),Cairo,Egypt.

6 Chief Executive Officer (CEO) of On-Medical Company.


Introduction: Heterogeneity correction is an important parameter in dose calculation for cancer patients where it may be cause inaccuracy in dose calculation as a result of different densities of patients. This study studied the impact of dose calculation of breast cancer patients with and without heterogeneity correction. Material and Methods: Twenty breast cancer patients were treated with Three-Dimensional Conformal Radiotherapy(3DCRT). Dose calculations were performed using two modes: Fast Photon mode for homogeneity and Fast Photon Effective Path length for heterogeneity with two photon energies. Monitor Units(MU), Modulation Factor, Dose Volume Histograms(DVH) and quality indices were used to evaluate the effect of heterogeneity correction on dose calculation and investigate the mechanism of this effect in the low and high energies.
Results: Heterogeneity correction compared to without it showed significant reduction in MU and modulation factor at 6MVand 10MV (p <0.05). Dosimetric parameters derived from DVH were significantly lower for Planning Target Volume (PTV) with homogeneity versus heterogeneity (p <0.05) as D95% (95.1%vs93.7%) and V95%(95.3%vs89%) for 6MV while max Dose and D2 increased. Also the dose for organs at risk exhibited an increase with heterogeneity correction. Quality indices were be worst with heterogeneity correction with a significant difference (p <0.05). The differences between the dose with heterogeneity correction and without it in 6MV and 10MV were as follows: ΔD95% (4.4%vs3.4%;P=0.001) and ΔV95%(4.76%vs4.5%;P=0.001).
Conclusion: non-use of the heterogeneity correction can be cause to deliver under or overdose dose to the target volume. Tissue heterogeneity correction had an impact on dose calculation for breast cancer patients and this impact was more effective for the low energy. 


Main Subjects

  1. References


    1. Podgorsak, Ervin B. "Radiation oncology physics." Vienna: International Atomic Energy Agency 2005; 123-271.
    2. Ahnesjo A, Aspradakis MM. “Dose calculations for external photon beams in radiotherapy.” Phys Med Biol 1999; 44: 99–155
    3. Thomas SJ. “A modified power-law formula for inhomogeneity corrections in beams of high-energy x rays.” Med Phys 1991; 18: 719 -723.
    4. Lu L. Dose calculation algorithms in external beam photon radiation therapy. Int J Cancer Ther Oncol 2013; 1: 01025.
    5. Knoos T, Wieslander E, Cozzi L, Brink C, Fogliata A, Albers D, et al. Comparison of dose calculation algorithms for treatment planning in external photon beam therapy for clinical situations. Phys Med Biol. 2006; 51: 5785–07.
    6. Borges, Cunha, Monteiro-Grillo, Vaz, Teixeira. “Comparison of different breast planning techniques and algorithms for radiation therapy treatment.” Phys Med. 2014;30(2):160-70.
    7. Nishioka S, Kim L, Goyal S, Khan A, Haffty B , Yue N. Dosimetric Impact of Whole Breast Treatment Planning with Tissue Heterogeneity Correction. Med. Phys. 2013; 40: 313 .
    8. Fdhila M, Gabelle-Flandin I, Balosso J, Chaikh A. Quantitative evaluation of the impact of heterogeneity correction on left breast cancer radiotherapy performed with respiratory gating. International Journal of Cancer Therapy and Oncology. 2016;4(1): 417.
    9. Basran PS, Zavgorodni S, Berrang T. “The impact of dose calculation algorithms on partial and whole breast radiation treatment plans.” Radiat Oncol. 2010; 5:120.
    10. Yoo S, Wu Q, O’Daniel J. “Comparison of 3D conformal breast radiation treatment plans using the anisotropic analytical algorithm and pencil beam convolution algorithm. Radiother Oncol.” 2012; 103:172-7.
    11. Task Group No. 65, The Radiation Therapy Committee of the American Association of Physicists in Medicine. Tissue inhomogeneity corrections for MV photon beams. Madison, WI: Medical Physics 2004.
    12. Steven J.Frank , Kenneth M.Forster , Craig W. Stevens. “Treatment Traditional Homogeneous Point- Dose prescription Compared with Heterogeneity-correction Dose- Volume Prescription.” .” Int. J. Radiat. Oncol. Biol. Phys.2003;56:1308-1318.
    13. Gray A, Oliver LD, Johnston PN. “The accuracy of the pencil beam convolution and anisotropic analytical algorithms in predicting the dose effects due to attenuation from immobilization devices and large air gaps.” Med Phys 2009; 36: 3181-91.
    14. Rana S, Pokharel S. “Verification of dose calculation algorithms in a multi-layer heterogeneous phantom using films.” Gulf J Oncolog 2013; 1:63-9.
    15. Chaikh A , Giraud JY, Balosso J. A method to quantify and assess the dosimetric and clinical impact resulting from the heterogeneity correction in radiotherapy for lung cancer. Int J Cancer Ther Oncol. 2014; 2(1):020110.
    16. Morgan AM, Knoos T, McNee SG, Evans CJ , Thwaites DI. Clinical Implications of the implementation of advanced treatment planning algorithms for thoracic treatments. Radiother Oncol. 2008;86(1):48-54.
    17. Fraass BA, Lichter AS, McShan DL, Yanke BR, Diaz RF, Yeakel KS, Van de Geinjn J. The influence of lung density corrections on treatment planning for primary breast cancer. International Journal of Radiation Oncology• Biology• Physics. 1988 Jan 1;14(1):179-90.
    18. Ellen MM, Hogstrom KR, Miller LA, Erice RC, Buchholz TA. A comparison of 18-MV and 6-MV treatment plans using 3D dose calculation with and without heterogeneity correction. Medical Dosimetry. 1999 Nov 1;24(4):287-94.
    19. ICRU Report No. 50. “Prescribing, Recording and Reporting Photon Beam Therapy.International Commission on Radiation Units and Measurements,” Bethesda, Maryland 1993.
    20. ICRU Report No. 62. “Prescribing, Recording and Reporting Photon Beam Therapy supplement to ICRU Report 50, International Commission on Radiation Units and Measurements,” Bethesda, Maryland 1999.
    21. Marks L B, Yorke ED, Jackson R . Use of normal tissue complication probability models in the clinic. International Journal of Radiation Oncology Biology Physics . 2010; 76(3): 10-9.
    22. Yavas G, Yavas C, Acar H. Dosimetric comparison of whole breast radiotherapy using field in field and conformal radiotherapy techniques in early stage breast cancer. International Journal of Radiation Research. 2012 Dec 1;10(3/4):131.
    23. Shaw E, Kline R, Gillin M, Souhami L, Hirschfeld A, Dinapoli R, Martin L. Radiation Therapy Oncology Group: radiosurgery quality assurance guidelines. International Journal of Radiation Oncology• Biology• Physics. 1993 Dec 1;27(5):1231-9.
    24. Wong JW, Purdy JA. “On methods of inhomogeneity corrections for photon transport.” Med Phys 1990;17: 807-14.