Ding Huanjun, Gao Hao, Zhao Bo, Cho Hyo-Min, Molloi Sabee
Department of Radiological Sciences, University of California, Irvine, CA 92697, USA.
Phys Med Biol. 2014 Oct 21;59(20):6005-17. doi: 10.1088/0031-9155/59/20/6005. Epub 2014 Sep 17.
Both computer simulations and experimental phantom studies were carried out to investigate the radiation dose reduction with tensor framelet based iterative image reconstruction (TFIR) for a dedicated high-resolution spectral breast computed tomography (CT) based on a silicon strip photon-counting detector. The simulation was performed with a 10 cm-diameter water phantom including three contrast materials (polyethylene, 8 mg ml(-1) iodine and B-100 bone-equivalent plastic). In the experimental study, the data were acquired with a 1.3 cm-diameter polymethylmethacrylate (PMMA) phantom containing iodine in three concentrations (8, 16 and 32 mg ml(-1)) at various radiation doses (1.2, 2.4 and 3.6 mGy) and then CT images were reconstructed using the filtered-back-projection (FBP) technique and the TFIR technique, respectively. The image quality between these two techniques was evaluated by the quantitative analysis on contrast-to-noise ratio (CNR) and spatial resolution that was evaluated using the task-based modulation transfer function (MTF). Both the simulation and experimental results indicated that the task-based MTF obtained from TFIR reconstruction with one-third of the radiation dose was comparable to that from the FBP reconstruction for low contrast target. For high contrast target, the TFIR was substantially superior to the FBP reconstruction in terms of spatial resolution. In addition, TFIR was able to achieve a factor of 1.6-1.8 increase in CNR, depending on the target contrast level. This study demonstrates that the TFIR can reduce the required radiation dose by a factor of two-thirds for a CT image reconstruction compared to the FBP technique. It achieves much better CNR and spatial resolution for high contrast target in addition to retaining similar spatial resolution for low contrast target. This TFIR technique has been implemented with a graphic processing unit system and it takes approximately 10 s to reconstruct a single-slice CT image, which can potentially be used in a future multi-slit multi-slice spiral CT system.
为了研究基于张量小波的迭代图像重建（TFIR）对基于硅条光子计数探测器的专用高分辨率光谱乳腺计算机断层扫描（CT）的辐射剂量降低效果，进行了计算机模拟和实验体模研究。模拟使用直径为10厘米的水体模进行，该体模包含三种对比剂（聚乙烯、8毫克/毫升碘和B - 100骨等效塑料）。在实验研究中，使用直径为1.3厘米的聚甲基丙烯酸甲酯（PMMA）体模，其中含有三种浓度（8、16和32毫克/毫升）的碘，在不同辐射剂量（1.2、2.4和3.6毫戈瑞）下采集数据，然后分别使用滤波反投影（FBP）技术和TFIR技术重建CT图像。通过对对比度噪声比（CNR）的定量分析以及使用基于任务的调制传递函数（MTF）评估的空间分辨率，对这两种技术的图像质量进行了评估。模拟和实验结果均表明，对于低对比度目标，使用三分之一辐射剂量的TFIR重建获得的基于任务的MTF与FBP重建相当。对于高对比度目标，TFIR在空间分辨率方面明显优于FBP重建。此外，根据目标对比度水平，TFIR能够使CNR提高1.6至1.8倍。这项研究表明，与FBP技术相比，TFIR在CT图像重建中可将所需辐射剂量降低三分之二。除了对低对比度目标保持相似的空间分辨率外，它还为高对比度目标实现了更好的CNR和空间分辨率。这种TFIR技术已在图形处理单元系统上实现，重建一幅单层CT图像大约需要10秒，有望在未来的多狭缝多层螺旋CT系统中使用。
