Estimation of Out-of-Field Dose Variation using Markus Ionization Chamber Detector

Ahmed M. Abdelaal, Ehab M. Attalla, Wael M. Elshemey


Objective: The aim of This work to provide evaluation  for the out-of-field dose with different plan parameters as field size and depth using Markus ionization chamber detector in the measurement that are frequently used in electron and superficial dosimetery, in radiotherapy. Methods: This is carried out through the application of these detector in estimation of the out-of-field dose with important dosimetric parameters such as field size (from 5×5 to 30×30 cm2) and depth (from 1.5 to 30 cm) at energy 6 MV and collimator angle 0° at SSD 100 cm. Results: Results show that, the Markus detector reported an increase in out-of-field dose with field size, depth in almost all measurements. For 6 MV and 0° collimator  angle, the out-of-field dose at field size of 5×5 cm2 (depth of 1.5 cm) is 1.1%  and at field size of  30×30 cm2 (depth of 1.5 cm) is 4.4% . The out-of-field dose for a depth of 1.5 cm (field size of 10×10 cm2) is 2.3% and for a depth of 30 cm (field size of 10×10 cm) is 5.5%. the measured out-of-field dose by Markus detector overestimated in the calculated at different field sizes (2.7% instead of 2.3% at field size of 10×10 cm2 and 5.2% instead of 4.4% at field size of 30×30 cm2) and different depths (2.7% instead of 1.1% at depth of 1.5 cm and 4.1% instead of 3.4% at depth of 30 cm). Analysis: The result reported an increase in mean out-of-field dose with field size, depth, energy and SSD. Markus ionization chamber detector show overestimation of the measured out-of-field dose in the calculated values at all field sizes and depths, this may be attributed to the poor detection of out-of-field dose by TPS.


Markus; Out-of-field dose; Dosimetry; Radiotherapy.


Jeraj, M. and Robar, V., 2004. Multileaf collimator in radiotherapy. Radiology and Oncology, 38(3):235-240+248.

Johns HE and Cunningham JR., 1983. The Physics of Radiology. Radiology, 152(1), pp.194-194.

Khan FM (2010). The physics of radiation therapy. 4th ed., Philadelphia: Lippincott Williams & Wilkins.

Wojcicka, J. B., Yankelevich, R., Werner, B. L., & Lasher, D. E. (2008). Technical Note: On Cerrobend shielding for 18-22MeV electron beams. Medical Physics, 35(10), 4625–4629. doi:10.1118/1.2977801.

Hogstrom, K. R., Boyd, R. A., Antolak, J. A., Svatos, M. M., Faddegon, B. A., & Rosenman, J. G. (2004). Dosimetry of a prototype retractable eMLC for fixed-beam electron therapy. Medical Physics, 31(3), 443–462. doi:10.1118/1.1644516.

Kry, S. F., Bednarz, B., Howell, R. M., Dauer, L., Followill, D., Klein, E., … George Xu, X. (2017). AAPM TG 158: Measurement and calculation of doses outside the treated volume from external-beam radiation therapy. Medical Physics, 44(10), e391–e429. doi:10.1002/mp.12462.

Dörr, W., & Herrmann, T. (2002). Cancer induction by radiotherapy: dose dependence and spatial relationship to irradiated volume. Journal of Radiological Protection, 22(3A), A117–A121. doi:10.1088/0952-4746/22/3a/321.

Pierce, D. A., & Preston, D. L. (2000). Radiation-related cancer risks at low doses among atomic bomb survivors. Radiation research, 154(2), 178-186. doi:10.1667/0033-7587(2000)154[0178:RRCRAL]2.0.CO;2.

Preston, D. L., Shimizu, Y., Pierce, D. A., Suyama, A., & Mabuchi, K. (2003). Studies of Mortality of Atomic Bomb Survivors. Report 13: Solid Cancer and Noncancer Disease Mortality: 1950–1997. Radiation Research, 160(4), 381–407. doi:10.1667/rr3049.

Chofor, N., Harder, D., Willborn, K. C., & Poppe, B. (2012). Internal scatter, the unavoidable major component of the peripheral dose in photon-beam radiotherapy. Physics in Medicine and Biology, 57(6), 1733–1743. doi:10.1088/0031-9155/57/6/1733.

Farhood, B., & Ghorbani, M. (2019). Dose calculation accuracy of radiotherapy treatment planning systems in out-of-field regions. Journal of Biomedical Physics & Engineering, 9(2), 133.

Harrison, R. (2017). Out-of-field doses in radiotherapy: Input to epidemiological studies and dose-risk models. Physica Medica, 42, 239–246. doi:10.1016/j.ejmp.2017.02.001.

Xu, X. G., Bednarz, B., & Paganetti, H. (2008). A review of dosimetry studies on external-beam radiation treatment with respect to second cancer induction. Physics in Medicine and Biology, 53(13), R193–R241. doi:10.1088/0031-9155/53/13/r01.

Lonski, P., Kron, T., Taylor, M., Phipps, A., Franich, R., & Chua, B. (2018). Assessment of leakage dose in vivo in patients undergoing radiotherapy for breast cancer. Physics and Imaging in Radiation Oncology, 5, 97–101. doi:10.1016/j.phro.2018.03.004.

Jang, S. Y., Liu, H. H., & Mohan, R. (2008). Underestimation of Low-Dose Radiation in Treatment Planning of Intensity-Modulated Radiotherapy. International Journal of Radiation Oncology*Biology*Physics, 71(5), 1537–1546. doi:10.1016/j.ijrobp.2008.04.014.

Kaderka, R., Schardt, D., Durante, M., Berger, T., Ramm, U., Licher, J., & Tessa, C. L. (2012). Out-of-field dose measurements in a water phantom using different radiotherapy modalities. Physics in Medicine and Biology, 57(16), 5059–5074. doi:10.1088/0031-9155/57/16/5059.

Vlachopoulou, V., Malatara, G., Delis, H., Theodorou, K., Kardamakis, D. and Panayiotakis, G., (2010). Peripheral dose measurement in high-energy photon radiotherapy with the implementation of MOSFET. World Journal of Radiology, 2(11), 434. doi:10.4329/wjr.v2.i11.434.

Taylor, M., & Kron, T. (2011). Consideration of the radiation dose delivered away from the treatment field to patients in radiotherapy. Journal of Medical Physics, 36(2), 59. doi:10.4103/0971-6203.79686.

Annamalai, G., & Velayudham, R. (2009). Comparison of peripheral dose measurements using Ionization chamber and MOSFET detector. Reports of Practical Oncology & Radiotherapy, 14(5), 176–183. doi:10.1016/s1507-1367(10)60033-8

Majer, M., Stolarczyk, L., De Saint-Hubert, M., Kabat, D., Knežević, Ž., Miljanić, S., … Harrison, R. (2017). Out-of-field Dose Measurements For 3D Conformal and Intensity Modulated Radiotherapy of a Paediatric Brain Tumour. Radiation Protection Dosimetry, 176(3), 331–340. doi:10.1093/rpd/ncx015.

Full Text: PDF

DOI: 10.28991/SciMedJ-2020-0201-2


  • There are currently no refbacks.

Copyright (c) 2020 ahmed Mousa abdelaal