Brzeziński K, Oliver J F, Gillam J, Rafecas M
Instituto de Física Corpuscular (CSIC/Universitat de València), c/Catedrático José Beltrán, 2. E-46980 Paterna, Valencia, Spain.
Phys Med Biol. 2014 Oct 21;59(20):6117-40. doi: 10.1088/0031-9155/59/20/6117. Epub 2014 Sep 25.
A high-resolution silicon detector probe, in coincidence with a conventional PET scanner, is expected to provide images of higher quality than those achievable using the scanner alone. Spatial resolution should improve due to the finer pixelization of the probe detector, while increased sensitivity in the probe vicinity is expected to decrease noise. A PET-probe prototype is being developed utilizing this principle. The system includes a probe consisting of ten layers of silicon detectors, each a 80 × 52 array of 1 × 1 × 1 mm(3) pixels, to be operated in coincidence with a modern clinical PET scanner. Detailed simulation studies of this system have been performed to assess the effect of the additional probe information on the quality of the reconstructed images. A grid of point sources was simulated to study the contribution of the probe to the system resolution at different locations over the field of view (FOV). A resolution phantom was used to demonstrate the effect on image resolution for two probe positions. A homogeneous source distribution with hot and cold regions was used to demonstrate that the localized improvement in resolution does not come at the expense of the overall quality of the image. Since the improvement is constrained to an area close to the probe, breast imaging is proposed as a potential application for the novel geometry. In this sense, a simplified breast phantom, adjacent to heart and torso compartments, was simulated and the effect of the probe on lesion detectability, through measurements of the local contrast recovery coefficient-to-noise ratio (CNR), was observed. The list-mode ML-EM algorithm was used for image reconstruction in all cases. As expected, the point spread function of the PET-probe system was found to be non-isotropic and vary with position, offering improvement in specific regions. Increase in resolution, of factors of up to 2, was observed in the region close to the probe. Images of the resolution phantom showed visible improvement in resolution when including the probe in the simulations. The image quality study demonstrated that contrast and spill-over ratio in other areas of the FOV were not sacrificed for this enhancement. The CNR study performed on the breast phantom indicates increased lesion detectability provided by the probe.
一种高分辨率硅探测器探头，与传统正电子发射断层扫描（PET）扫描仪配合使用，有望提供比仅使用扫描仪所能获得的更高质量的图像。由于探头探测器的像素化更精细，空间分辨率应会提高，而探头附近灵敏度的增加预计会降低噪声。正在利用这一原理开发一种PET探头原型。该系统包括一个由十层硅探测器组成的探头，每层是一个80×52的1×1×1立方毫米像素阵列，将与现代临床PET扫描仪配合运行。已对该系统进行了详细的模拟研究，以评估额外的探头信息对重建图像质量的影响。模拟了一个点源网格，以研究探头在视野（FOV）不同位置对系统分辨率的贡献。使用分辨率体模来展示两个探头位置对图像分辨率的影响。使用具有热区和冷区的均匀源分布来证明分辨率的局部提高不会以牺牲图像的整体质量为代价。由于这种提高仅限于靠近探头的区域，因此提出将乳腺成像作为这种新型几何结构的潜在应用。从这个意义上说，模拟了一个与心脏和躯干部分相邻的简化乳腺体模，并通过测量局部对比度恢复系数与噪声比（CNR）来观察探头对病变可检测性的影响。在所有情况下都使用列表模式最大似然期望最大化（ML-EM）算法进行图像重建。正如预期的那样，发现PET探头系统的点扩散函数是非各向同性的，并且随位置变化，在特定区域有所改善。在靠近探头的区域观察到分辨率提高了多达2倍。当在模拟中包括探头时，分辨率体模的图像显示分辨率有明显提高。图像质量研究表明，在FOV的其他区域，对比度和溢出率并未因这种增强而牺牲。在乳腺体模上进行的CNR研究表明探头提供了更高的病变可检测性。
