Thursday, 26 May 2016

Bolus

It is a mass of scattering material, such as wax or paraffin, placed between the radiation source and the skin to achieve a precalculated isodose pattern in the tissue irradiated. It is a quantity of tissue-equivalent material placed in the radiation beam, over the surface of the irradiated region, to fill in irregular body surfaces, to improve dose distribution (homogenize or modulate the range of the dose from external beams of radiation [1]) and to increase the absorbed dose in the superficial tissues (increase the dose to the skin) [2]. It is a material of density nearly equivalent to tissue placed within the treatment beam to compensate for unevenness of body contour or to enhance the buildup of electrons on the surface of the skin [3]. It will reduce the penetration depth of the radiation beam, bringing it closer to the surface of the patient's skin [4]. It can be used for megavoltage (high energy) photon and electron radiation therapy. Materials used as bolus vary from simple water to metal and include various mixtures and compounds [5].
Bibliographic references:
[1] Wikipedia. (2016). Bolus (medicine). [online] Available at: https://en.wikipedia.org/wiki/Bolus_(medicine)  [Accessed 26 May 2016].
[2] TheFreeDictionary.com. (2016). bolus. [online] Available at: http://medical-dictionary.thefreedictionary.com/bolus [Accessed 26 May 2016].
[3] Kentuckyonehealth.org. (2016). Radiation Therapy Glossary Lexington, Kentucky (KY) - Saint Joseph Hospital. [online] Available at: http://www.kentuckyonehealth.org/hospital-cancer-center-radiation-oncology-therapy-glossary [Accessed 26 May 2016].
[4] Perelman School of Medicine, University of Pennsylvania, Department of Radiation Oncology. (n.d.). Glossary of Terms for Radiation Oncology. [online] Available at: http://www.xrt.upenn.edu/documents/RadOncGlossaryofTerms.pdf [Accessed 26 May 2016].
[5] Vyas V, Palmer L, Mudge R, Et al. On bolus for megavoltage photon and electron radiation therapy. Med Dosim. 2013 Autumn;38(3):268-73. Available at: http://dx.doi.org/10.1016/j.meddos.2013.02.007.