SU‐E‐T‐328: 3D Extrusion Based Printing of Custom Bolus Using a Non‐Invasive and Low Cost Method

Purpose: To create precise patient specific bolus for an irregular surface using a non‐invasive and low cost method of 3D printing. Methods: An infrared camera (Microsoft Kinect) is used to obtain a 3D model patients' face in real‐time (ReconstructMe). Image processing such as reorienting non‐manifold surfaces, smoothing, and filling holes is performed to refine the model using freely available software (Meshlab, Netfab). The bolus was constructed by two methods using a 3D Acrylonitrile Butadiene Styrene (ABS) extrusion based printer. The 1st method used was to print out a 1:1 scale model of the patient's nose, and construct the bolus using wax on face model. The 2nd method used was to create a digital model of the bolus material to the specifications of the physician (depth, size). This bolus can either be printed solid, or with a low infill percentage and filled with wax to save print time. Results: Average scan time to obtain face model is 5 minutes (+/−2 minutes). Image processing varies on model, around 30 minutes. Print time ranges from 1–4 hours. The physicist time requirement to manufacture bolus material is greatly reduced compared to producing a physical mold of patient's anatomy. Patient comfort is greatly increased. Both wax bolus and ABS bolus are highly conformal to patient's face. A CT is not necessary to create our bolus material, however a CT performed on the bolus alone demonstrated high HU homogeneity (HU range).Startup costs range from $1000–$3000 dollars, depending on model and capabilities of the extruder. Typical material cost is around $3–$10 per patient depending on bolus volume. Conclusion: Highly irregular surfaces can be digitally modeled with high precision. Patient specific bolus can be made quickly, inexpensively, and without complex imaging.