Synthetic aperture focusing (SAF) and coherence factor weighting (CFW) have been used to improve the lateral resolution of ultrasound images. Although the two methods are effective for array-based ultrasound imaging, many researchers have also employed the methods for single-element-based imaging including intravascular ultrasound (IVUS) imaging. For single-element-based imaging, CFW is generally calculated from the scanlines obtained by SAF and applied to the scanline obtained after coherent summation of the SAF delayed scanlines, which is called a SAF-CFW method. In the paper, a theoretical model was derived to explore the effectiveness of SAF and CFW for single-element-based imaging, and the model was used to explain that SAF is not effective for IVUS imaging in terms of enhancing the spatial resolution, although it has the advantage of improving a contrast-to-noise ratio (CNR). This means that the SAF-CFW method is not optimal for improving the spatial resolution of IVUS imaging. In contrast, it was found in simulations and experiments that applying CFW to the target scanline itself is beneficial for the spatial resolution rather than a coherent summed scanline for IVUS SAF imaging, but CNR was not as good as SAF and SAF-CFW. As a result of both simulation and experimentation, it could be concluded that focused IVUS transducers without the application of those methods may be more advantageous to improve the spatial and contrast resolution simultaneously, considering the system complexity in the implementation of such imaging methods.

合成孔径聚焦（SAF）和相干因子加权（CFW）已用于改善超声图像的横向分辨率。尽管这两种方法对于基于阵列的超声成像都是有效的，但许多研究人员还采用了基于单元素的成像方法，包括血管内超声（IVUS）成像。对于基于单元素的成像，通常根据SAF获得的扫描线计算CFW，并将CFW应用于SAF延迟扫描线的相干求和之后获得的扫描线，这称为SAF-CFW方法。在本文中，推导了一个理论模型来探索SAF和CFW在基于单元素的成像中的有效性，并且该模型用于解释SAF在增强空间分辨率方面对IVUS成像无效，尽管它具有改善对比度和噪声比（CNR）的优点。这意味着SAF-CFW方法对于提高IVUS成像的空间分辨率不是最佳的。相反，在模拟和实验中发现，将CFW应用于目标扫描线本身对IVUS SAF成像有利于空间分辨率，而不是相干的求和扫描线，但是CNR不如SAF和SAF-CFW好。作为仿真和实验的结果，可以得出结论，考虑到这种成像方法实施中的系统复杂性，不使用那些方法的聚焦IVUS换能器可能更有利于同时提高空间分辨率和对比度分辨率。这意味着SAF-CFW方法对于提高IVUS成像的空间分辨率不是最佳的。相反，在模拟和实验中发现，将CFW应用于目标扫描线本身对IVUS SAF成像有利于空间分辨率，而不是相干的求和扫描线，但是CNR不如SAF和SAF-CFW好。作为仿真和实验的结果，可以得出结论，考虑到这种成像方法实施中的系统复杂性，不使用那些方法的聚焦IVUS换能器可能更有利于同时提高空间分辨率和对比度分辨率。这意味着SAF-CFW方法对于提高IVUS成像的空间分辨率不是最佳的。相反，在模拟和实验中发现，将CFW应用于目标扫描线本身对IVUS SAF成像有利于空间分辨率，而不是相干的求和扫描线，但是CNR不如SAF和SAF-CFW好。作为仿真和实验的结果，可以得出结论，考虑到这种成像方法实施中的系统复杂性，不使用那些方法的聚焦IVUS换能器可能更有利于同时提高空间分辨率和对比度分辨率。在模拟和实验中发现，将CFW应用于目标扫描线本身对IVUS SAF成像有利于空间分辨率，而不是相干的求和扫描线，但是CNR不如SAF和SAF-CFW好。作为仿真和实验的结果，可以得出结论，考虑到这种成像方法实施中的系统复杂性，不使用那些方法的聚焦IVUS换能器可能更有利于同时提高空间分辨率和对比度分辨率。在模拟和实验中发现，将CFW应用于目标扫描线本身对IVUS SAF成像有利于空间分辨率，而不是相干的求和扫描线，但是CNR不如SAF和SAF-CFW好。作为仿真和实验的结果，可以得出结论，考虑到这种成像方法实施中的系统复杂性，不使用那些方法的聚焦IVUS换能器可能更有利于同时提高空间分辨率和对比度分辨率。