Evaluation of the Usefulness of Self-Made Filters Using 3D Printing Technology in Shoulder Superoinferior Axial Projection

Abstract

Purpose: The purpose of this study is to find out the adjacent organ shielding effect of self-made filters with 3D printing technology and to identify the thickness of the filter for shielding effects similar to bismuth during the shoulder superoinferior axial projection.

Materials and Methods: This study used a GC 85A (Samsung Electronics, Korea) X-ray equipment and was conducted on a phantom PBU-60 (Kyotokagaku, Japan) model. The filter production was modeled using the Autodesk fusion 360 program followed by 3D printing using an S3 (Ultimaker, Netherlands) 3D printer, with polylactic acid (Ultimaker, Netherlands) used as the raw material and printed using the fused filament fabrication method. For the shape of the filter, a base and six individual filters (Layer 1–6) that can be attached to the base were produced. The experimental method obtained an image by attaching the base part to the collimator and stacking individual filters up to six layers. Data were obtained 20 times for each group. The exposure parameters were fixed at a tube voltage of 68 ㎸p, a tube current of 16 ㎃s, an irradiation field of 8" × 10", and a source to image distance of 100 ㎝. In order to measure the entrance skin dose (ESD), the dosimeter element was attached to the breast and thyroid areas.

Results: As a result of measuring the average value of the ESD of the breast and thyroid gland according to the change in filter thickness, the non-filter status was 276.39 μ㏉ and 357.77 μ㏉, and 140.29 μ㏉ and 175.79 μ㏉, respectively, when bismuth was attached. ESD values measured in the base of the filter were 217.69 μ㏉ and  281.46 μ㏉, while Layer 1, Layer 2, Layer 3, Layer 4, Layer 5, and Layer 6 measured 180.71 μ㏉ and 233.74 μ㏉, 150.27 μ㏉ and 185.82 μ㏉, 127.37 μ㏉ and 166.72 μ㏉, 112.11 μ㏉ and 143.74 μ㏉, 94.63 μ㏉ and 121.89 μ㏉, and 84.72 μ㏉ and 106.71 μ㏉, respectively.

Conclusion: As a result of this study, the average value of ESD decreased by 49% and 50% in breast and thyroid, respectively, compared to the non-filter state. Dose reduction effect was similar to that of bismuth in Layer 2 (45% breast and 48% thyroid) and Layer 3 (53% breast and 53% thyroid). Therefore, a thickness ranging between the thickness of Layer 2 and 3 (3.5 ㎝ in the elbow area, 1.5 ㎝ in the axillary area and 2.5 ㎝ in the chest area) was considered optimal thickness of the 3D-printed filter for efficient shielding of the thyroid and breast.