不同图像重建算法对定量化光声重建效果的影响

Influence of Different Image Reconstruction Method on Quantitative Photoacoustic Tomography

光声成像结合了光学成像高光学对比度和超声成像高空间分辨率的优点。光声成像的原理是用光照射生物组织,生物组织吸收一部分能量并转化成热能,使生物组织的温度升高,引起热膨胀并产生超声波。生物组织吸收的能量正比于光子数密度和生物组织的吸收系数。光声重建的第一步是用采集到的超声波重建初始场强,第二步是分离出生物组织的光学系数(如光的吸收系数和散射系数)和声学系数(Grüneisen系数等),光声重建的第二步也称定量化光声重建。然而,定量化光声成像依然面临着很多困难,多光源光声成像已经被证明可以分离出光的吸收系数和散射系数。本文中,我们用多个点光源,从收集到的超声波中直接分离出了光的吸收系数和散射系数,并且对比了奇异值分解算法和代数迭代算法(Algebraic Reconstruction Technique,ART)两种重建算法对定量化光声成像效果的影响。结果表明,在加入噪声的情况下,ART的定量化光声成像效果更佳。

Photoacoustic tomography is a hybrid imaging that potentially takes advantage of high optical contrast brought by optical imaging and high spatial resolution brought by ultrasound imaging.The principle for photoacoustic tomography is illuminating biological tissue by optical energy,which will be absorbed by samples with a local absorbing optical contrast.Then the absorbed energy converts into heat and increase the object,causing thermal expansion to generate an acoustic pressure wave.The energy deposited is proportional to the fluence and the local absorption coefficient of the tissues.The first step of photoacousitc reconstruction is to reconstruct the initial pressure distribution from collected photoacousitc pressure;the second step is to reconstruct the optical and acoustical coefficient of the tissue,the second step is also called the quantitative photoacoustic tomography.However,the quantification in photoacoustic imaging is still challenging.Multiple optical illumination approach has been proved to achieve uncoupling of absorption and diffusion coefficient.In this paper,multiple optical illuminations were adopted and photoacoustic pressure was used directly for reconstruction.The influence of the reconstruction method singular value decomposition and algebraic reconstruction technique(ART)were tested.The results showed that ART behaved better in the reconstructions.