Radiotherapy Department, Ninewells Hospital & Medical School, NHS Tayside, Dundee, UK.
Medical Physics Department, Ninewells Hospital & Medical School, Dundee, UK.
J Appl Clin Med Phys. 2021 Apr;22(4):26-33. doi: 10.1002/acm2.13147. Epub 2021 Mar 10.
When planning and delivering radiotherapy, ideally bolus should be in direct contact with the skin surface. Varying air gaps between the skin surface and bolus material can result in discrepancies between the intended and delivered dose. This study assessed a three-dimensional (3D) printed flexible bolus to determine whether it could improve conformity to the skin surface, reduce air gaps, and improve planning target volume coverage, compared to a commercial bolus material, Superflab.
An anthropomorphic head phantom was CT scanned to generate photon and electron treatment plans using virtual bolus. Two 3D printing companies used the material Ninjaflex to print bolus for the head phantom, which we designated Ninjaflex1 and Ninjaflex2. The phantom was scanned a further 15 more times with the different bolus materials in situ allowing plan comparison of the virtual to physical bolus in terms of planning target volume coverage, dose at the prescription point, skin dose, and air gap volumes.
Superflab produced a larger volume and a greater number of air gaps compared to both Ninjaflex1 and Ninjaflex2, with the largest air gap volume of 12.02 cm . Our study revealed that Ninjaflex1 produced the least variation from the virtual bolus clinical goal values for all modalities, while Superflab displayed the largest variances in conformity, positional accuracy, and clinical goal values. For PTV coverage Superflab produced significant percentage differences for the VMAT and Electron3 plans when compared to the virtual bolus plans. Superflab also generated a significant difference in prescription point dose for the 3D conformal plan.
Compared to Superflab, both Ninjaflex materials improved conformity and reduced the variance between the virtual and physical bolus clinical goal values. Results illustrate that custom-made Ninjaflex bolus could be useful clinically and may improve the accuracy of the delivered dose.
在规划和实施放疗时，理想情况下，填充物应与皮肤表面直接接触。皮肤表面与填充物之间的空气间隙变化可能导致计划剂量与实际剂量之间存在差异。本研究评估了一种三维（3D）打印的柔性填充物，以确定与商业填充物 Superflab 相比，它是否可以改善与皮肤表面的贴合度、减少空气间隙，并提高计划靶区覆盖度。
对人体头部体模进行 CT 扫描，使用虚拟填充物生成光子和电子治疗计划。两家 3D 打印公司使用 Ninjaflex 材料为头部体模打印填充物，我们将其分别命名为 Ninjaflex1 和 Ninjaflex2。进一步对体模进行了 15 次扫描，在体模上使用不同的填充物，以比较虚拟和物理填充物在计划靶区覆盖度、处方点剂量、皮肤剂量和空气间隙体积方面的差异。
Superflab 与 Ninjaflex1 和 Ninjaflex2 相比，产生的体积更大，空气间隙数量更多，最大空气间隙体积为 12.02cm。我们的研究表明，Ninjaflex1 在所有模式下与虚拟填充物临床目标值的差异最小，而 Superflab 在贴合度、位置准确性和临床目标值方面的变化最大。对于 PTV 覆盖度，与虚拟填充物计划相比，Superflab 为 VMAT 和电子 3 计划产生了显著的百分比差异。Superflab 还对 3D 适形计划的处方点剂量产生了显著差异。
与 Superflab 相比，两种 Ninjaflex 材料都提高了贴合度，减少了虚拟和物理填充物临床目标值之间的差异。结果表明，定制的 Ninjaflex 填充物在临床上可能是有用的，并可能提高实际剂量的准确性。
