The many faces of bolus: Part 2

Previously I discussed the role of bolus material in radiation therapy and some of the forms it takes. This post shows a couple of other examples.

Pink bolus molded into shape.

Super Stuff bolus, also known generically as pink bolus, is a moldable bolus material with the consistency of gelatin. The material is described by the manufacturer as a "hydophilic organic polymer" and is sold in individual powder packets. Pink bolus is supposed to have a density of 1.02 g/cm³. To use the bolus, you add the necessary amount of water, allow the material to set, i.e. coming to its gelatin-like consistency, and then knead it into the shape you want. Over time pink bolus will lose its shape and must be re-shaped. Eventually it will lose some consistency due to moisture loss and a new batch must be made. Care must also be taken to remove as many air bubbles as possible.

A packet of pink bolus powder.

Recently in our clinic we treated a patient with classic (i.e. non-HIV related) Kaposi sarcoma of the leg with photons. For this we decided to use rice grains as the bolus material. As with all bolus, the idea of using rice is to simulate tissue and modify the dose distribution as desired. In this case, increase of skin dose is desired.

Rice bolus box for treating a patient's leg/foot.

For this patient we built a polystyrene foam box and filled it with loose rice grains. It took approximately 10 kg of dry parboiled rice to fill the box with the patient's leg. The patient plus rice box was then scanned with the CT and planned as normal.

Some leftover rice (not) used as bolus material.

The open access article linked below from Ahn et al. shows some dosimetric comparisons between the use of rice as a bolus and a water bolus for irradiating extremities. I will warn you that both methods create a mess at best :)

Further reading:

• Ahn SK, Kim YB, Lee IJ, Song TS, Son DM, Jang YJ, Cho JH, Kim JH, Kim DW, Cho JH, Suh CO.   Evaluation of a Water-based Bolus Device for Radiotherapy to the Extremities in Kaposi's Sarcoma Patients.   J Korean Soc Ther Radiol Oncol. 2008 Sep;26(3):189-194.   http://dx.doi.org/10.3857/jkstro.2008.26.3.189 (Open access. In Korean with abstract and figure captions in English.)