Medical Imaging Research Center, Medical Physics and Quality Assessment, Katholieke Universiteit Leuven, 3000 Leuven, Belgium.
Phys Med Biol. 2019 Feb 5;64(4):045001. doi: 10.1088/1361-6560/aafd5c.
This work describes a new approach to automatic dose rate control (ADRC) for dynamic x-ray imaging, utilizing a spatial frequency weighted signal difference to noise ratio (SDNR(u)). Three aspects of ADRC programming using SDNR(u), which contains information on the target material, velocity and size, were examined. First, whether SDNR(u) can be held constant at the requested level over some patient thickness range for five materials relevant to interventional imaging (iron, gadolinium, platinum, bismuth, and tantalum). Second, the efficiency of the new ADRC was compared to the current settings using a figure of merit (FOM), defined as SDNR(u)/reference air kerma rate for iron and platinum, over a range of simulated patient thicknesses. Third, the ability of the new ADRC to optimize exposure parameters for iron, iodine, gadolinium, tantalum, platinum and bismuth was examined. A phantom of 20 mm PMMA and 2 mm Al sheets was used to simulate patient equivalent thicknesses between 25 mm to 375 mm. The relevant metal foil targets were placed at the phantom centre and imaged on a Siemens Artis Q cardio-angiography system. SDNR(u) and reference air kerma were measured, along with the FOM for the relevant conditions. The optimal exposure factor study was made for patient equivalent thicknesses of 100 mm, 200 mm and 300 mm. The new ADRC regulation held SDNR(u) constant versus phantom thickness within 5%, for the five materials studied. FOM increase compared to the current regulation used on the Artis Q ranged between 18% and 296% (averaged over all thicknesses), and depended on acquisition mode and material. Material optimization via the new ADRC increased FOM by 68%, 165%, 164% and 32% for gadolinium, tantalum, platinum and bismuth respectively, corresponding to potential dose savings of 40%, 62%, 62% and 24% for the same target SDNR(u). An SDNR(u) driven approach to the ADRC logic of dynamic imaging systems is a viable alternative to current programming, with a resulting improvement in imaging efficiency and corresponding dose reduction.
这项工作描述了一种用于动态 X 射线成像的自动剂量率控制（ADRC）新方法，利用空间频率加权信噪比（SDNR(u)）。研究了使用 SDNR(u)进行 ADRC 编程的三个方面，其中包含有关目标材料、速度和大小的信息。首先，对于与介入成像相关的五种材料（铁、钆、铂、铋和钽），SDNR(u)能否在一定的患者厚度范围内保持在请求的水平。其次，使用一个质量因数（FOM）比较了新 ADRC 的效率与当前设置，该因数定义为铁和铂的 SDNR(u)/参考空气比释动能率，模拟了一系列患者厚度。第三，检查了新 ADRC 优化铁、碘、钆、钽、铂和铋曝光参数的能力。使用 20mm PMMA 和 2mm Al 板的体模模拟了 25mm 至 375mm 之间的患者等效厚度。将相关的金属箔靶放在体模中心，并在西门子 Artis Q 心血管造影系统上进行成像。测量了 SDNR(u)和参考空气比释动能，以及相关条件下的 FOM。对于 100mm、200mm 和 300mm 的患者等效厚度进行了最佳曝光因子研究。新的 ADRC 调节在 5%的范围内使 SDNR(u)相对于体模厚度保持恒定，适用于五种研究材料。与 Artis Q 上使用的当前调节相比，FOM 增加了 18%至 296%（所有厚度的平均值），并取决于采集模式和材料。通过新的 ADRC 进行材料优化，钆、钽、铂和铋的 FOM 分别增加了 68%、165%、164%和 32%，相应的目标 SDNR(u)剂量节省分别为 40%、62%、62%和 24%。基于 SDNR(u)的动态成像系统 ADRC 逻辑方法是当前编程的可行替代方案，可提高成像效率并相应降低剂量。
