Abstracts Submitted: 510
Number of Users: 710
View Abstracts Submitted
Back to home Page
Abstract submited
Abstract :
Photoacoustic (PA) imaging is an emerging soft tissue imaging modality which can be efficiently used for tissue characterization. PA imaging is a hybrid between pure optical and US imaging. PA imaging can be used for efficient tissue characterization as it provides optical property based contrast and good spatial resolution at significant depth inside the soft tissue. Generally, PA signal recorded by a PA imaging system involves convolution with the system impulse response followed by addition of noise. For accurate tissue characterization we should have the knowledge of initial PA signal generated by PA absorber. This study aims at to first estimate transducer impulse response from the recorded PA signal using homomorphic filtering based on discrete wavelet transform followed by extraction of initial PA signal using Wiener filtering based deconvolution. In general, the impulse log magnitude spectrum is quiet smooth and having peaks around the center frequency of the transducer where as initial PA signal log magnitude spectrum is spiky and irregular. Thus, the separation of impulse spectrum from the signal spectrum can be performed by homomorphic signal processing, taking the advantage of the fact that the log spectrum of recorded PA signal is the sum of log spectrum of the impulse response and the log spectrum of the initial PA signal. The basic idea in homomorphic filtering theory is to use the mathematical concept of homomorphic mapping to transform the product of two original signals into the sum of two derived signals. If these two derived signals are located in different bands they can be separated by simple linear filtering. Each of the separate, original signals can then be retrieved by applying the inverse mapping. After extracting initial PA signal the next step is to quantitatively measure dimension [radius] of the regular shaped PA absorbers using the detail wavelet spectrum of the extracted PA signal. The simulation results show that the algorithm works well. We simulated practical PA signal generated by a cylindrical PA absorber of 0.7mm radius. The transducer impulse response was estimated from the simulated PA signal and applied to extract initial PA signal. The radius value computed from the detail spectrum of the recovered PA signal was found to be 0.75mm which is closed to the actual value (0.7mm).