选择准确、合适的成像信号是提高超声调制光学层析成像（UOT）灵敏度和对比度的关键。利用快速傅里叶变换(FFT)获得了超声调制信号的的频谱图像，其中零频强度I0代表着未被超声调制的光信号的谱强度，而在超声探头频率范围内（0.2~1.8 MHz）的谱强度之和表示受超声调制信号的谱强度If。与时域信号相比较，谱强度If对介质的光学性质有较高的灵敏度，但它容易受非靶组织（介质）的影响。而频谱信号的调制深度M2（M2=If/I0）不易受非靶组织（介质）的影响，有较强的抗干扰性，但它对靶组织（介质）的光学属性的灵敏度低。结果表明，采用超声调制光信号的频谱进行图像处理和重构并不比时域信号更具优势。

The choice of the accurate and proper signal is the key to enhance the sensitivity and contrast of ultrasound-modulated optical tomography（UOT）. Fast Fourier transform (FFT) is used in the digital frequency analysis of modulation signal. Spectral intensity of zero frequency (I0) represents the unmodulated light intensity, and the sum total of spectral intensity (If) from 0.2 MHz to 1.8 MHz depended on the frequency range of ultrasonic probe represents the ultrasound-modulated light intensity. Compared with the in-time signal, If has the higher sensitivity to optical properties of media, but it is easy to be influenced by the non-target media. The modulated depth of in-frequency signal (M2=If/I0) is not easy to be influenced by non-target media, but it has low sensitivity to optical properties of the target media. The results indicate that the result of in-frequency signal is not better than the in-time signal for image reconstruction and processing.