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. 2020 May 15;10(1):8016.
doi: 10.1038/s41598-020-64967-5.

Low-Cost iPhone-Assisted Processing to Obtain Radiotherapy Bolus Using Optical Surface Reconstruction and 3D-Printing

Dehua Kang  1   2 , Bin Wang  2 , Yinglin Peng  2 , Xiaowei Liu  3 , Xiaowu Deng  4
Affiliations

Low-Cost iPhone-Assisted Processing to Obtain Radiotherapy Bolus Using Optical Surface Reconstruction and 3D-Printing

Dehua Kang et al. Sci Rep. .

Abstract

Patient specific boluses can increase the skin dose distribution better for treating tumors located just beneath the skin with high-energy radiation than a flat bolus. We introduce a low-cost, 3D-printed, patient-specific bolus made of commonly available materials and easily produced using the "structure from motion" and a simple desktop 3D printing technique. Nine pictures were acquired with an iPhone camera around a head phantom. The 3D surface of the phantom was generated using these pictures and the "structure from motion" algorithm, with a scale factor calculated by a sphere fitting algorithm. A bolus for the requested position and shape based on the above generated surface was 3D-printed using ABS material. Two intensity modulated radiation therapy plans were designed to simulate clinical treatment for a tumor located under the skin surface with a flat bolus and a printed bolus, respectively. The planned parameters of dose volume histogram, conformity index (CI) and homogeneity index (HI) were compared. The printed bolus plan gave a dose coverage to the tumor with a CI of 0.817 compared to the CI of 0.697 for the plan with flat bolus. The HIs of the plan with printed bolus and flat bolus were 0.910 and 0.887, respectively.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Procedure of bolus reconstruction using the SFM method. (a) The acquired pictures were imported into SFM workspace and 3D reconstruction was run. (b) The surface of the head phantom and the sphere calibration model. (c) The surface of head phantom with a bolus region marker line. (d) The surface of the sphere calibration model. (e) The registration deviation between the two surfaces from the SFM and Marching Cube from CT images. (f) Bolus viewed in the STL format file. (g) The bolus printed using ABS material. (h) The bolus was put in the right place on the head phantom surface.
Figure 2
Figure 2
The left panel shows the dose distribution of the 5-beam IMRT plan without a piece of flat bolus. The right panel shows the dose distribution of the 5-beam IMRT plan with printed bolus. The minimum dose color wash was 4750 cGy. The bottom are the sagittal and coronal views according to the corresponding plans, respectively.
Figure 3
Figure 3
DVH of the two plans with printed bolus and a piece of flat bolus, respectively.
Figure 4
Figure 4
Details of the gap between the printed bolus and the head phantom surface.
See this image and copyright information in PMC

References

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