Bolus Material Analysis

Comparison of three alternative bolus materials to Superflab in providing the maximum dose buildup (Dmax)
Many superficial tumors are treated using 6 Megavoltage (MV) photons, but often require a bolus to bring the depth of maximum dose closer to the skin surface. A bolus may also be used to compensate for uneven skin surfaces or irregular contours in the patient. The depth of maximum equilibrium describes the depth in which the maximum dose of the formulated radiation is deposited (Washington & Leaver, 2010). Bolus material should be flexible, pliable, and tissue-equivalent. There is no study that compares green Play-Doh, orange Play-Doh, water and uncooked rice to Superflab for providing maximum dose buildup, Dmax. Dmax describes the depth

This deposits the maximum dose below or on the skin surface. A bolus should be flexible and pliable so it can contour the skin surface without any air gaps. Paraffin wax, Vaseline gauze, wet gauze or towels, and water bags are noncommercial materials that can be used. Commercial materials have variable thicknesses or powder forms that can be mixed with water. Boluses may be applied on scars, superficial lymph nodes, or on uneven skin surfaces (McDermott & Orton, 2010). Superflab is a commonly used manufactured tissue-equivalent plastic bolus. It is also flexible and will not dry out. Superflab has a gravity of 1.02 g/cm3; similar to water, and includes materials approved by the FDA. It comes in different thicknesses to provide maximum dose buildup. Its elasticity allows it to uniformly conform to the patient’s contour. Using photons and electrons, Superflab was compared with polystyrene of various thicknesses to determine its dosimetric properties. The results showed Superflab to be more similar to water than polystyrene (Feaster,

Superflab bolus material with the dimensions 10 cm x 10 cm x 1.0 cm is placed flush on top of the solid water to obtain the Dmax. Subsequent measurements made with Play-Doh which placed on top of a clear thin plastic bag, as well as the rice in a sandwich bag having the same dimensions as Superflab. The same set of trials performed with the neon green Play-Doh and the orange Play-Doh. A Varian Clinac 6EX Linear Accelerator produced 6 MV photons and irradiated a field size of 10 cm x 10 cm for each dose. Two hundred monitor units (MU) administered during each trial on a clinically calibrated linear accelerator. Ionization Dmax made with each material using an Exradin A12 Farmer chamber and read by a Keithley 35614 digital dosimeter with no temperature or pressure corrections made. The current in the dosimeter set to +300. The dose on the electrometer measure the output of each trial in Coulombs x