Clinical and Dosimetric Implications of Air Gaps between Bolus and Skin Surface during Radiation Therapy


Purpose: The main objective of the study was to evaluate the effect of air gaps of 0 - 5.0 cm between bolus and skin for 1.0 cm Superflab bolus on surface dose (DSurf) and depth of maximum dose (dmax) in solid water and Rando? phantoms. Methods: In this work, the effects of bolus to surface distance on DSurf and variation in dmax were analyzed in a solid water phantom and in an anthropomorphic Rando? phantom for different field sizes, using Gafchromic? EBT films and farmer chamber. Results: For field sizes of 5 × 5 cm2 the DSurf is significantly affected by increasing air gaps greater than 5 mm. For field sizes larger than 10 × 10 cm2, DSurf is nearly the same for air gaps of 0 - 5.0 cm. For small fields and 6 MV photon beam, dmax increases with increasing air gap, while for 10 MV beam and smaller field sizes (i.e. 5 × 5 and 10 × 10 cm2) the dmax first decreases and then increases with the air gaps. For both 3DCRT and IMRT plans on Rando?, DSurf reduction is more prominent with increasing air gaps. Conclusion: For field sizes larger than 10 × 10 cm2 DSurf is largely unaffected by air gaps. However, smaller air gap results in shallower dmax for both 6 MV and 10 MV photon beams at all fields sizes. Special consideration should be taken to reduce air gaps between bolus and skin for field sizes smaller than 10 × 10 cm2 or when surface contour variations are greater or when the bolus covers small area and at the border of the field.

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Y. Khan, J. Villarreal-Barajas, M. Udowicz, R. Sinha, W. Muhammad, A. Abbasi and A. Hussain, "Clinical and Dosimetric Implications of Air Gaps between Bolus and Skin Surface during Radiation Therapy," Journal of Cancer Therapy, Vol. 4 No. 7, 2013, pp. 1251-1255. doi: 10.4236/jct.2013.47147.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] F. M. Khan, “The Physics of Radiation Therapy,” Lippincott Williams & Wilkins, Philadelphia, 2010, p. 144.
[2] M. Stroka, J. Regula and W. Lobodziec, “The Influence of the Bolus-Surface Distance on the Dose Distribution in the Build-Up Region,” Reports of Practical Oncology & Radiotherapy, Vol. 15, No. 6, 2010, pp. 161-164. doi:10.1016/j.rpor.2010.09.003
[3] K. I. Aneta, L. Wlodzimierz, D. Marcin, N. Dorota and I. Tomasz, “Dose Distribution Homogeneity in Two TBI Techniques—Analysis of 208 Irradiated Patients Conducted in Stanislaw Leszczynski Memorial Hospital, Katowice,” Reports of Practical Oncology & Radiotherapy, Vol. 17, No. 6, 2012, pp. 367-375. doi:10.1016/j.rpor.2012.07.013
[4] J. B. Martin, C. Tsang and Y. Peter, “Effects on Skin Dose from Unwanted Air Gaps under Bolus in Photon Beam Radiotherapy,” Radiation Measurements, Vol. 32, No. 3, 2000, pp. 201-204. doi:10.1016/S1350-4487(99)00276-0
[5] S. H. Hsu, R. Kulasekere and P. L. Roberson, “Analysis of Variation in Calibration Curves for Kodak XV Radiographic Film Using Model-Based Parameters,” Journal of Applied Clinical Medical Physics, Vol. 11, No. 4, 2010, pp. 222-237.
[6] K. Alireza, B. Peter, Y. Ellen, et al., “Beam Spoilers versus Bolus for 6 mv Photon Treatment of Head and Neck Cancers,” Medical Dosimetry, Vol. 25, No. 3, 2000, pp. 127-131. doi:10.1016/ S0958-3947(00)00038-8
[7] S. H. Hsu, P. L. Roberson, Y. Chen, et al., “Assessment of Skin Dose for Breast Chest Wall Radiotherapy as a Function of Bolus Material,” Physics in Medicine & Biology, Vol. 53, No. 10, 2008, pp. 2593-2606. doi:10.1088/0031-9155/53/10/010
[8] N. Lee, C. Chuang, J. M. Quivey, et al., “Skin Toxicity Due to IMRT for Head-and-Neck Carcinoma,” International Journal of Radiation Oncology Biology Physics, Vol. 53, No. 3, 2002, pp. 630-637. doi:10.1016/S0360-3016(02)02756-6
[9] P. D. Higgins, E. H. Han, J. L. Yuan and C. K. Lee, “Evaluation of Surface and Superficial Dose for Head and Neck Treatments Using Conventional or IMRT Techniques,” Physics in Medicine & Biology, Vol. 52, 2007, pp. 1135-46. doi:10.1088/0031-9155/52/4/018
[10] N. Dogan and Glasgow, “Surface and Build-Up Region Dosimetry for Obliquely Incident IMRT 6MV X Rays,” Medical Physics, Vol. 30, No. 12, pp. 3091-3096. doi:10.1118/1.1625116
[11] S. Yokoyama, P. L. Roberson, D. W. Litzenberg, et al., “Surface Buildup Dose Dependence on Photon Field Delivery Technique for IMRT,” Journal of Applied Clinical Medical Physics, Vol. 5, No. 2, 2004, pp. 71-81. doi:10.1120/jacmp.2020.21706
[12] A. Gray, L. D. Oliver and P. N. Johnston, “The Accuracy of the Pencil Beam Convolution and Anistropic Analytical Algorithms in Predicting the Dose Effects Due to Attenuation from Immobilization Devices and Large Air Gaps,” Medical Physics, Vol. 36, No. 7, 2009, pp. 3181-3191. doi:10.1118/1.3147204
[13] A. Kassaee, Y. Xiao, P. Bloch, et al., “Doses near the Surface during Total-Body Irradiation with 15 MV XRays,” International Journal of Cancer, Vol. 96, 2001, pp. 125-130. doi:10.1002/ ijc.10349

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