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

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DOI: 10.4236/jct.2013.47147    6,088 Downloads   8,677 Views   Citations


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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The authors declare no conflicts of interest.

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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.


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