Bartolac S, Jaffray D
University of Toronto, Toronto, ON.
Princess Margaret Hospital, Toronto, ON.
Med Phys. 2012 Jun;39(6Part20):3857. doi: 10.1118/1.4735745.
Dose management in CT is a growing concern as the number of CT scans per capita rises. Fluence field modulated computed tomography (FFMCT) is a proposed approach for more optimal dose management, where the incident fluence pattern can change independently for each projection in order to minimize dose while meeting prescribed image quality metrics. This work studies the application of FFMCT for dose and noise management to a small cylindrical phantom.
Experiments were carried out on an experimental CT system using a small cylindrical phantom comprised of acrylic spheres, water and teflon rods as the object of interest. Modulation of the incident fluence was optimized using a simulated annealing algorithm that attempts to achieve user-prescribed, regionally varying SNR criteria while limiting dose. The modulated projections were synthesized from projection sets taken at various tube current settings. SNR patterns and predicted dose outcomes were compared to the prescribed values as well as against expected results using a bowtie filter.
FFMCT resulted in SNR outcomes with greater agreement to the prescribed regionally varying SNR criteria than achieved by the bowtie filter. Dose reductions were observed for the majority of the object, and reached as high as 60%. Limited regions, coinciding with lower noise, observed dose increases less than 20%. Integral dose reduction over the entire object was greater than 40% when compared to a bowtie filter with comparable image quality in the region of interest.
The results support the hypothesis that FFMCT has the potential to meet user-prescribed, regionally varying image quality objectives, while decreasing radiation dose to the patient. These results suggest that given a suitable collimator approach, fluence field modulated computed tomography could reap significant benefits in terms of reducing dose and optimizing image quality. NSERC.
随着人均CT扫描次数的增加，CT剂量管理日益受到关注。注量场调制计算机断层扫描（FFMCT）是一种用于更优化剂量管理的方法，其中每个投影的入射注量模式可以独立变化，以便在满足规定图像质量指标的同时将剂量降至最低。本研究探讨FFMCT在小型圆柱形体模中的剂量和噪声管理应用。
在一个实验性CT系统上进行实验，使用一个由丙烯酸球、水和聚四氟乙烯棒组成的小型圆柱形体模作为感兴趣的对象。使用模拟退火算法优化入射注量的调制，该算法试图在限制剂量的同时实现用户规定的、区域变化的信噪比标准。调制后的投影由在不同管电流设置下采集的投影集合成。将信噪比模式和预测的剂量结果与规定值以及使用蝴蝶结滤波器的预期结果进行比较。
与蝴蝶结滤波器相比，FFMCT产生的信噪比结果与规定的区域变化信噪比标准更吻合。在大多数对象中观察到剂量降低，高达60%。在与较低噪声一致的有限区域，观察到剂量增加小于20%。与感兴趣区域图像质量相当的蝴蝶结滤波器相比，整个对象的积分剂量降低超过40%。
结果支持以下假设，即FFMCT有潜力满足用户规定的、区域变化的图像质量目标，同时降低患者的辐射剂量。这些结果表明，给定合适的准直器方法，注量场调制计算机断层扫描在降低剂量和优化图像质量方面可能会带来显著益处。加拿大自然科学与工程研究理事会。
