Sanchez Jose R, Oelze Michael L
Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
IEEE Trans Ultrason Ferroelectr Freq Control. 2009 Jul;56(7):1327-39. doi: 10.1109/TUFFC.2009.1189.
A method for improving the contrast resolution of B-mode images is proposed by combining the speckle-reduction technique of frequency compounding (FC) and the coded excitation and pulse-compression technique called resolution enhancement compression (REC). FC suppresses speckle but at the expense of a reduction in axial resolution. Using REC, the axial resolution and bandwidth of the imaging system was doubled. Therefore, by combining REC with FC (REC-FC), the tradeoff between axial resolution and contrast enhancement was extended significantly. Simulations and experimental measurements were conducted with a single-element transducer (f/2.66) having a center frequency of 2.25 MHz and a -3-dB bandwidth of 50%. Simulations and measurements of hyperechoic (+6 dB) tissue-mimicking targets were imaged. Four FC cases were evaluated: full-, half-, third-, and fourth-width of the true impulse response bandwidth. The image quality metrics used to compare REC-FC to conventional pulsing (CP) and CP-FC were contrast-to-noise ratio (CNR), speckle signal-to-noise ratio, histogram pixel intensity, and lesion signal-to-noise ratio. Increases in CNR of 121%, 231%, 302%, and 391% were obtained in experiments when comparing REC-FC for the full-, half-, third-, and fourth-width cases to CP. Furthermore, smaller increases in CNR of 112%, 233%, and 309% were obtained in experiments when comparing CP-FC for the half-, third-, and fourth-width cases to CP. Improved lesion detectability was observed by using REC-FC.
本文提出了一种通过结合频率复合（FC）的散斑减少技术和称为分辨率增强压缩（REC）的编码激励与脉冲压缩技术来提高B模式图像对比度分辨率的方法。FC抑制了散斑，但以轴向分辨率降低为代价。使用REC，成像系统的轴向分辨率和带宽提高了一倍。因此，通过将REC与FC相结合（REC-FC），轴向分辨率和对比度增强之间的权衡得到了显著扩展。使用中心频率为2.25 MHz、-3 dB带宽为50%的单元素换能器（f/2.66）进行了模拟和实验测量。对高回声（+6 dB）组织模拟目标进行了模拟和测量成像。评估了四种FC情况：真实脉冲响应带宽的全宽、半宽、三分之一宽和四分之一宽。用于将REC-FC与传统脉冲（CP）和CP-FC进行比较的图像质量指标有对比度噪声比（CNR）、散斑信噪比、直方图像素强度和病变信噪比。在实验中，将全宽、半宽、三分之一宽和四分之一宽情况下的REC-FC与CP进行比较时，CNR分别提高了121%、231%、302%和391%。此外，在实验中，将半宽、三分之一宽和四分之一宽情况下的CP-FC与CP进行比较时，CNR分别有较小幅度的提高，为112%、233%和309%。使用REC-FC观察到病变可检测性得到了改善。
