bolus
Pronunciation: BOH-lus
A tissue-equivalent material placed on the patient's skin surface to modify the dose distribution and bring the maximum dose closer to the surface.
Full Definition
In radiation therapy, bolus is a flexible, tissue-equivalent material (typically made of gel, wax, or special plastics) that is placed directly on the patient's skin during treatment. Its primary purpose is to eliminate the skin-sparing effect of megavoltage beams and ensure adequate dose delivery to superficial targets such as skin cancers or post-mastectomy chest walls. Bolus effectively moves the depth of maximum dose buildup closer to or at the skin surface, compensating for surface irregularities and air gaps.
Usage
Usage note: Not to be confused with compensators, which are used for beam intensity modification rather than surface dose enhancement.
In Context
- "A 1 cm bolus was applied to ensure adequate surface dose to the chest wall." — Treatment technique description
- "The radiation therapist verified proper bolus placement before each treatment fraction." — Treatment delivery protocol