Gear Jonathan I, Taprogge Jan, White Owen, Flux Glenn D
Joint Department of Physics, Royal Marsden NHSFT and Institute of Cancer Research, Downs Road, Sutton, SM2 5PT, UK.
EJNMMI Phys. 2019 Jan 7;6(1):1. doi: 10.1186/s40658-018-0238-3.
The aim of this work was to characterise the attenuation properties of 3D-printed tungsten and to assess the feasibility for its use in gamma camera collimator manufacture.
3D-printed tungsten disks were produced using selective laser melting (SLM). Measurements of attenuation were made through increasing numbers of disks for a Tc-99m (140 keV) and I-131 (364 keV) source. The technique was validated by repeating the measurements with lead samples. Resolution measurements were also made with a SLM tungsten collimator and compared to Monte Carlo simulations of the experimental setup. Different collimator parameters were simulated and compared against the physical measurements to investigate the effect on image quality.
The measured disk thicknesses were on average 20% above the specified disk thicknesses. The measured attenuation for the tungsten samples were lower than the theoretical value determined from the National Institute of Standards and Technology (NIST) cross-sectional database (Berger and Hubbell, XCOM: photon cross-sections on a personal computer, 1987). The laser scan strategy had a significant influence on material attenuation (up to 40% difference). Results of these attenuation measurements indicate that the density of the SLM material is lower than the raw tungsten density. However, an improved performance compared to a lead collimator was observed. The SLM tungsten collimator was adequately simulated as 80% density and 110% septal thickness. Scatter and septal penetration were 17% less than a similar lead collimator and 33% greater than tungsten at 100% density.
SLM manufacture of tungsten collimators is feasible. Attenuation properties of SLM tungsten are superior to the lead alternative and the opportunity for bespoke collimator design is appealing.
本研究旨在表征3D打印钨的衰减特性，并评估其在伽马相机准直器制造中的应用可行性。
采用选择性激光熔化（SLM）技术制作3D打印钨盘。针对99mTc（140keV）和131I（364keV）源，通过增加钨盘数量进行衰减测量。通过对铅样品重复测量来验证该技术。还使用SLM钨准直器进行分辨率测量，并与实验装置的蒙特卡罗模拟结果进行比较。模拟不同的准直器参数，并与物理测量结果进行对比，以研究其对图像质量的影响。
测量得到的钨盘厚度平均比规定厚度高20%。钨样品的测量衰减低于美国国家标准与技术研究院（NIST）截面数据库（Berger和Hubbell，《XCOM：个人计算机上的光子截面》，1987年）确定的理论值。激光扫描策略对材料衰减有显著影响（差异高达40%）。这些衰减测量结果表明，SLM材料的密度低于原始钨密度。然而，与铅准直器相比，观察到性能有所改善。SLM钨准直器在模拟时密度设为80%，隔板厚度设为110%较为合适。与类似的铅准直器相比，散射和隔板穿透减少了17%，与100%密度的钨相比则增加了33%。
SLM制造钨准直器是可行的。SLM钨的衰减特性优于铅准直器，且定制准直器设计的机会很有吸引力。
