Lu Zenghai, Kasaragod Deepa K, Matcher Stephen J
Department of Materials Science and Engineering, the Kroto Research Institute, University of Sheffield, North Campus, Broad Lane, Sheffield, S3 7HQ, UK.
Biomed Opt Express. 2011 Mar 4;2(4):794-804. doi: 10.1364/BOE.2.000794.
Recently the effects of reduced bit-depth acquisition on swept-source optical coherence tomography (SS-OCT) image quality have been evaluated by using simulations and empirical studies, showing that image acquisition at 8-bit depth allows high system sensitivity with only a minimal drop in the signal-to-noise ratio compared to higher bit-depth systems. However, in these studies the 8-bit data is actually 12- or 14-bit ADC data numerically truncated to 8 bits. In practice, a native 8-bit ADC could actually possess a true bit resolution lower than this due to the electronic jitter in the converter etc. We compare true 8- and 14-bit-depth imaging of SS-OCT and polarization-sensitive SS-OCT (PS-SS-OCT) by using two hardware-synchronized high-speed data acquisition (DAQ) boards. The two DAQ boards read exactly the same imaging data for comparison. The measured system sensitivity at 8-bit depth is comparable to that for 14-bit acquisition when using the more sensitive of the available full analog input voltage ranges of the ADC. Ex-vivo structural and birefringence images of equine tendon indicate no significant differences between images acquired by the two DAQ boards suggesting that 8-bit DAQ boards can be employed to increase imaging speeds and reduce storage in clinical SS-OCT/PS-SS-OCT systems. One possible disadvantage is a reduced imaging dynamic range which can manifest itself as an increase in image artifacts due to strong Fresnel reflection.
最近，通过模拟和实证研究评估了降低比特深度采集对扫频源光学相干断层扫描（SS-OCT）图像质量的影响，结果表明，与更高比特深度的系统相比，8比特深度的图像采集能够实现高系统灵敏度，且信噪比仅有极小的下降。然而，在这些研究中，8比特数据实际上是将12比特或14比特的模数转换（ADC）数据进行数值截断得到的。在实际应用中，由于转换器中的电子抖动等因素，原生8比特ADC的实际比特分辨率可能会低于此。我们通过使用两个硬件同步的高速数据采集（DAQ）板，对SS-OCT和偏振敏感型SS-OCT（PS-SS-OCT）的真实8比特和14比特深度成像进行了比较。这两个DAQ板读取完全相同的成像数据以进行对比。当使用ADC可用的全模拟输入电压范围中更灵敏的范围时，8比特深度下测得的系统灵敏度与14比特采集时相当。马肌腱的离体结构和双折射图像表明，两个DAQ板采集的图像之间没有显著差异，这表明8比特DAQ板可用于提高临床SS-OCT/PS-SS-OCT系统的成像速度并减少存储量。一个可能的缺点是成像动态范围减小，这可能表现为由于强烈的菲涅尔反射导致图像伪影增加。
