Cruz-Bastida Juan P, Gomez-Cardona Daniel, Li Ke, Sun Heyi, Hsieh Jiang, Szczykutowicz Timothy P, Chen Guang-Hong
Department of Medical Physics, University of Wisconsin-Madison School of Medicine and Public Health, 1111 Highland Avenue, Madison, Wisconsin 53705.
Department of Medical Physics, University of Wisconsin-Madison School of Medicine and Public Health, 1111 Highland Avenue, Madison, Wisconsin 53705 and Department of Radiology, University of Wisconsin-Madison, 600 Highland Avenue, Madison, Wisconsin 53792.
Med Phys. 2016 May;43(5):2399. doi: 10.1118/1.4946816.
The introduction of a High-Resolution (Hi-Res) scan mode and another associated option that combines Hi-Res mode with the so-called High Definition (HD) reconstruction kernels (referred to as a Hi-Res/HD mode in this paper) in some multi-detector CT (MDCT) systems offers new opportunities to increase spatial resolution for some clinical applications that demand high spatial resolution. The purpose of this work was to quantify the in-plane spatial resolution along both the radial direction and tangential direction for the Hi-Res and Hi-Res/HD scan modes at different off-center positions.
A technique was introduced and validated to address the signal saturation problem encountered in the attempt to quantify spatial resolution for the Hi-Res and Hi-Res/HD scan modes. Using the proposed method, the modulation transfer functions (MTFs) of a 64-slice MDCT system (Discovery CT750 HD, GE Healthcare) equipped with both Hi-Res and Hi-Res/HD modes were measured using a metal bead at nine different off-centered positions (0-16 cm with a step size of 2 cm); at each position, both conventional scans and Hi-Res scans were performed. For each type of scan and position, 80 repeated acquisitions were performed to reduce noise induced uncertainties in the MTF measurements. A total of 15 reconstruction kernels, including eight conventional kernels and seven HD kernels, were used to reconstruct CT images of the bead. An ex vivo animal study consisting of a bone fracture model was performed to corroborate the MTF results, as the detection of this high-contrast and high frequency task is predominantly determined by spatial resolution. Images of this animal model generated by different scan modes and reconstruction kernels were qualitatively compared with the MTF results.
At the centered position, the use of Hi-Res mode resulted in a slight improvement in the MTF; each HD kernel generated higher spatial resolution than its counterpart conventional kernel. However, the MTF along the tangential direction of the scan field of view (SFOV) was significantly degraded at off-centered positions, yet the combined Hi-Res/HD mode reduced this azimuthal MTF degradation. Images of the animal bone fracture model confirmed the improved spatial resolution at the off-centered positions through the use of the Hi-Res mode and HD kernels.
The Hi-Res/HD scan improve spatial resolution of MDCT systems at both centered and off-centered positions.
在一些多探测器CT（MDCT）系统中引入高分辨率（Hi-Res）扫描模式以及另一种将Hi-Res模式与所谓的高清（HD）重建核相结合的相关选项（本文中称为Hi-Res/HD模式），为一些需要高空间分辨率的临床应用提供了提高空间分辨率的新机会。本研究的目的是量化Hi-Res和Hi-Res/HD扫描模式在不同偏心位置沿径向和切向的平面内空间分辨率。
引入并验证了一种技术，以解决在尝试量化Hi-Res和Hi-Res/HD扫描模式的空间分辨率时遇到的信号饱和问题。使用所提出的方法，在九个不同的偏心位置（0至16厘米，步长为2厘米）使用金属珠测量配备Hi-Res和Hi-Res/HD模式的64层MDCT系统（Discovery CT750 HD，GE医疗）的调制传递函数（MTF）；在每个位置，进行常规扫描和Hi-Res扫描。对于每种扫描类型和位置，进行80次重复采集以减少MTF测量中由噪声引起的不确定性。总共使用15种重建核，包括8种常规核和7种HD核，来重建珠子的CT图像。进行了一项包括骨折模型的离体动物研究，以证实MTF结果，因为这种高对比度和高频任务的检测主要由空间分辨率决定。将不同扫描模式和重建核生成的该动物模型图像与MTF结果进行定性比较。
在中心位置，使用Hi-Res模式导致MTF略有改善；每个HD核产生的空间分辨率高于其对应的常规核。然而，在偏心位置，沿扫描视野（SFOV）切向的MTF显著降低，但Hi-Res/HD组合模式减少了这种方位MTF降低。动物骨折模型的图像证实，通过使用Hi-Res模式和HD核，在偏心位置的空间分辨率得到了改善。
Hi-Res/HD扫描可提高MDCT系统在中心和偏心位置的空间分辨率。
