基于FHT和MSBP的CT图像滤波反投影重建方法设计

滤波反投影算法（FBP）是商用CT系统中广泛使用的图像重建方法。在CT图像重建应用的场合，投影数据和目标函数都属于实数空间范畴。基于Fourier变换的重建方法涉及大量复数运算，是其在计算上的一个固有特点。与Fourier变换相比，Hartley变换以其实值变换的特点，在实数域能够替代Fourier变换，进行信号和图像的处理。MSBP方法是基于重建图像像素和投影射线之间在不同的投影方位上所存在的几何关系而提出的。将快速Hartley变换（FHT）算法和MSBP方法应用于CT图像的滤波反投影重建方法中，在保持精度不变的前提下，减少了所需的存储空间和计算量。     

Projections of the zona incerta in the cat, with stimulation controls.

In eight cats single electrolytic lesions were placed in the zona incerta, and resultant fiber degeneration studies were made. In seven additional cats, stimulating electrodes were chronically implanted bilaterally into the zona incerta, H₂ (lenticular fasciculus), or H (prerubral) fields of Forel. The animals were placed in a two-compartment shuttle box, and a routinely established procedure of subthalamic stimulation was instituted. When the sensory (nociceptive) or motor manifestations and reactions were established, small lesions were made through both poles of the electrodes. The brains were studied by silver techniques for degenerating axons and terminals. Findings in the latter group of animals with physiologic substrates, compared to those in the first group, indicated that the zona incerta contains at least two major physiologic-anatomic components with differential fiber projections. The first component is a medial zona incerta proper or caudalis, paleospinothalamic, nociceptive-conducting system which causes typical escape responses. Its unequivocal projections are to the nucleus of the H₁ field, posterior and dorsal hypothalamus, part of the intralaminar system, ventromedial and ventralis anterior nuclei, nucleus reuniens, reticular nucleus, pulvinar, posterior nucleus, central gray, red nucleus, and the central tegmental tract. The second constitutent concerns pyramidal-extrapyramidal motor type responses that arise with avoidance reactions from other portions of the zona incerta. In these cases there is heavy projection to the caudate, entopenduncular, globus pallidus, and putamen nuclei. In contrast, degeneration from the nociceptive part of the zona incerta or H₂ and H fields to these nuclei is minimal.