Program Information
A Dosimetric Analysis of Various Clinically Used Bolus Materials
M Stowe*, C Yeager , F Zhou , C Hand , Albert Einstein Medical Center, Philadelphia, PA
Presentations
SU-E-T-9 Sunday 3:00PM - 6:00PM Room: Exhibit HallPurpose:
To evaluate the dosimetric effect of various clinically used bolus materials.
Methods:
Materials investigated include solid water, superflab, wet gauze, wet sheets, Play-Dohâ„¢, and gauze embedded with petroleum jelly. Each bolusing material was scanned in a Philips CT to determine the Hounsfield unit (HU) and to verify uniformity throughout the material. Using the corresponding HU, boluses of 0.5 cm and 1.0 cm thicknesses were created in the Eclipse treatment planning system (TPS) on a solid water phantom. Dose was calculated at various depths for beam energies 6 MV, 6 MeV, 9 MeV, and 12 MeV to determine the effects of each material on deposition of dose. In addition, linac-based measurements at these energies were made using a farmer chamber in solid water. Wet sheets and wet gauze were measured with various water content to quantify the effects on dose.
Results:
Preliminary CT scans find a range in HU of bolus materials from -120 to almost 300. There is a trend in the dose at depth based on the HU of the material; however inconsistencies are found when the bolus materials have a negative HU value. The measured data indicates that there is a linear relationship between the mass of water in a material and the dose reading, the slope of which is material dependent.
Conclusion:
Due to the variation in HU of the bolus materials studied, it is recommended that any new bolus be evaluated before clinical use to determine physical and dosimetric properties. If possible, patients should have bolus included in their CT scans; or if the bolus is created in the TPS, the HU should correspond to the material used. For water-soaked materials, once the bolus material is selected (gauze or sheet), the bolusing effect is only dependent on the amount of water applied to the material.
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