空间角度复合应变估计中的运动伪影产生因素研究
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摘要
颈动脉弹性成像可用于分析动脉内斑块的应变分布,并对其破裂风险(即易损性)进行有效评估。空间角度复合(Spatial Angular Compounding,SAC)方法已被提出来进一步改善其应变估计的性能。然而,在SAC各个角度的发射、接收过程中,斑块的运动和形变可能会导致运动伪影。因此,本研究的目的是通过仿真实验对基于SAC的应变估计中导致运动伪影产生的因素进行研究,包括脉冲重复频率(Pulse Repetition Frequency,PRF)和偏转角度数量(Number of Steering Angle,NSA)。在仿真实验中,物体被施加一个恒定速率为2s~(-1)的轴向压缩,来模拟理想情况和有运动伪影情况下的成像过程。本研究分析了PRF为200 Hz～10 kHz和NSA为1、3、5和7时的SAC应变估计性能,并通过信噪比(Signal-to-Noise Ratio,SNR)和对比度噪声比(Contrast-to-NoiseRatio,CNR)进行定量评估。结果表明,当PRF<4 kHz时,SNR和CNR会随PRF增加而增加,之后趋于平稳。对比不同角度SAC的结果发现,当PRF<1 kHz时,角度数越少,SNR和CNR越高;当PRF>4 kHz时,不同角度SAC的SNR和CNR皆比较接近。综上,本研究评估了PRF和NSA对SAC方法在应变估计中的影响。对于颈动脉弹性成像,基于PRF>4 kHz和NSA=3的SAC可以获得运动伪影较小的应变图像。
Carotid elastography can obtain the strain distribution of carotid atherosclerotic plaques and evaluate the vulnerability of plaques. Spatial angular compounding(SAC) has been proposed to improve the performance of strain estimation in carotid elastography. However, the motion and deformation of the plaque during multi-angle acquisitions may cause motion artifacts. In this study, the factors introducing motion artifacts in the strain estimation, including the pulse repetition frequency(PRF) and number of steering angle(NSA) were analyzed in the simulation experiments. In order to mimic the motion and deformation of the plaque, a constant axial compression at the strain rate of 2 s~(-1) was applied during the imaging process. The PRF was set from 0.2 kHz to 10 kHz and the NSA was set to 1, 3, 5 and 7. The elastographic signal-tonoise ratio(SNR) and contrast-to-noise ratio(CNR) were used to quantitatively evaluate the quality of strain estimation. The results showed that, the SNRs and CNRs increased with the PRF when PRF<4 kHz, and then remained constant. Comparing the performance of NSA=3, 5 and 7, the SNRs and CNRs were higher with a smaller NSA when PRF<1 kHz. When PRF exceeded4 kHz, the performance of SAC with different NSAs became similar in terms of SNRs and CNRs. In conclusion, this study has investigated the in?uence of the PRF and NSA on motion artifacts of strain imaging with SAC. In carotid elastography with SAC, the strain images with less motion artifacts are obtained when NSA is 3 and PRF>4 kHz.
Carotid elastography can obtain the strain distribution of carotid atherosclerotic plaques and evaluate the vulnerability of plaques. Spatial angular compounding(SAC) has been proposed to improve the performance of strain estimation in carotid elastography. However, the motion and deformation of the plaque during multi-angle acquisitions may cause motion artifacts. In this study, the factors introducing motion artifacts in the strain estimation, including the pulse repetition frequency(PRF) and number of steering angle(NSA) were analyzed in the simulation experiments. In order to mimic the motion and deformation of the plaque, a constant axial compression at the strain rate of 2 s~(-1) was applied during the imaging process. The PRF was set from 0.2 kHz to 10 kHz and the NSA was set to 1, 3, 5 and 7. The elastographic signal-tonoise ratio(SNR) and contrast-to-noise ratio(CNR) were used to quantitatively evaluate the quality of strain estimation. The results showed that, the SNRs and CNRs increased with the PRF when PRF<4 kHz, and then remained constant. Comparing the performance of NSA=3, 5 and 7, the SNRs and CNRs were higher with a smaller NSA when PRF<1 kHz. When PRF exceeded4 kHz, the performance of SAC with different NSAs became similar in terms of SNRs and CNRs. In conclusion, this study has investigated the in?uence of the PRF and NSA on motion artifacts of strain imaging with SAC. In carotid elastography with SAC, the strain images with less motion artifacts are obtained when NSA is 3 and PRF>4 kHz.
引文
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[14]Huang CW,Pan XC,He Q,et al.Ultrasound-based carotid elastography for detection of vulnerable atherosclerotic plaques validated by magnetic resonance imaging[J].Ultrasound Med Biol,2016,42(2):365-377.
[15]Naim C,Cloutier G,Mercure E,et al.Characterisation of carotid plaques with ultrasound elastography:feasibility and correlation with high-resolution magnetic resonance imaging[J].Eur Radiol,2013,23(7):2030-2041.
[16]Hansen HHG,De Borst G J,Bots M L,et al.Validation of noninvasive in vivo compoundul trasound strain imaging using histologic plaque vulnerability features[J]Stroke,2016,47(11):2770-2775.
[17]Pan XC,Liu K,Shao JH,et al.Performance comparison of rigid and affine models for motion estimation using ultrasound radiofrequency signals[J].IEEE Trans Ultrason Ferroelectr Freq Control,2015,62(11):1928-1943.
[18]Pan XC,Gao J,Tao SZ,et al.A two-step optical flow method for strain estimation in elastography:Simulation and phantom study[J].Ultrasonics,2014,54(4):990-996.
[19]Liu Z,Huang C W,Luo JW.A systematic investigation of lateral estimation using various interpolation approaches in conventional ultrasound imaging[J].IEEE Trans Ultrason Ferroelectr Freq Control,2017,64(8):1149-1160.
[20]Udesen J,Jensen J A.Investigation of transverse oscillation method[J].IEEE Trans Ultrason Ferroelectr Freq Control,2006,53(5):959-971.
[21]Rao M,Varghese T.Spatial angular compounding for elastography without the incompressibility assumption[J]Ultrason Imaging,2005,27(4):256-270.
[22]Rao M,Varghese T.Estimation of the optimal maximum beam angle and angular increment for normal and shear strain estimation[J].IEEE Trans Biomed Eng,2009,56(3):760-769.
[23]Hansen HHG,Lopata RGP,De Korte CL.Noninvasive carotid strain imaging using angular compounding at large beam steered angles:Validation in vessel phantoms[J].IEEE Trans Med Imaging,2009,28(6):872-880.
[24]Hansen HHG,Lopata RGP,Idzenga T,et al.Full 2Ddisplacement vector and strain tensor estimation for superficial tissue using beam-steered ultrasound imaging[J].,2010,55(11):3201-3218.
[25]Jensen JA.FIELD:a program for simulating ultrasound systems[J].Med Biol Eng Comput,1996,34(1):351-352.
[26]Jensen J A,Svendsen N B.Calculation of pressure fields from arbitrarily shaped,apodized,and excited ultrasound transducers[J].IEEE Trans Ultrason Ferroelectr Freq Control,1992,39(2):262-267.
[27]Luo JW,Bai J,He P,et al.Axial strain calculation using a lowpass digital differentiator in ultrasound elastography[J].IEEETrans Ultrason Ferroelectr Freq Control,2004,51(9):1119-1127.
[2]Mendel T,Popow J,Hier DB,et al.Advanced atherosclerosis of the aortic arch is uncommon in ischemic stroke:an autopsy study[J].Neurol Res,2002,24(5):491-494.
[3]Fan ZY,Zhang ZL,Chung YC,et al.Carotid arterial wall mri at 3t using3d variable-flip-angle turbo spin-echo(TSE)with flow-sensitive dephasing(FSD)[J].J Magn Reson Imaging,2010,31(3):645-654.
[4]Finn AV,Nakano M,Narula J,et al.Concept of vulnerable/unstable plaque[J].Arterioscler Thromb Vasc Biol,2010,30(7):1282-1292.
[5]Chen JW,Wasserman BA.Vulnerable plaque imaging[J].Neuroimaging Clin N Am,2005,15(3):609-621.
[6]Clarke SE,Hammond RR,Mitchell JR,et al.Quantitative assessment of carotid plaque composition using multicontrast MRI and registered histology[J].Magn Reson Med,2003,50(6):1199-1208.
[7]Cai JM,Hastukami TS,Ferguson MS,et al.Classification of human carotid atherosclerotic lesions with in vivo multicontrast magnetic resonance imaging[J].Circulation,2002,106(11):1368-1373
[8]Nighoghossian N,Derex L,Douek P.The vulnerable carotid artery plaque-Current imaging methods and new perspectives[J].Stroke,2005,36(12):2764-2772.
[9]Ophir J,Garra B,Kallel F,et al.Elastographic imaging[J]Ultrasound Med Biol,2000,26(4):S23-S29.
[10]Dekorte CL,Cespedes EI,Vandersteen AFW,et al.Intravascular elasticity imaging using ultrasound:Feasibility studies in phantoms[J].Ultrasound Med Biol,1997,23(5):735-746.
[11]De Korte CL,Van Der Steen AFW,Cespedes EI,et al Characterization of plaque components and vulnerability with intravascular ultrasound elastography[J].Phys Med Biol,2000,45(6):1465-1475.
[12]De Korte CL,Hansen HHG,Van Der Steen AFW.Vascular ultrasound for a the roscleros is imaging[J].Interface Focus,2011,1(4):565-575.
[13]Schaar JA,De Korte CL,Mastik F,et al.Characterizing vulnerable plaque features with intravascular elastography[J].Circulation,2003,108(21):2636-2641.
[14]Huang CW,Pan XC,He Q,et al.Ultrasound-based carotid elastography for detection of vulnerable atherosclerotic plaques validated by magnetic resonance imaging[J].Ultrasound Med Biol,2016,42(2):365-377.
[15]Naim C,Cloutier G,Mercure E,et al.Characterisation of carotid plaques with ultrasound elastography:feasibility and correlation with high-resolution magnetic resonance imaging[J].Eur Radiol,2013,23(7):2030-2041.
[16]Hansen HHG,De Borst G J,Bots M L,et al.Validation of noninvasive in vivo compoundul trasound strain imaging using histologic plaque vulnerability features[J]Stroke,2016,47(11):2770-2775.
[17]Pan XC,Liu K,Shao JH,et al.Performance comparison of rigid and affine models for motion estimation using ultrasound radiofrequency signals[J].IEEE Trans Ultrason Ferroelectr Freq Control,2015,62(11):1928-1943.
[18]Pan XC,Gao J,Tao SZ,et al.A two-step optical flow method for strain estimation in elastography:Simulation and phantom study[J].Ultrasonics,2014,54(4):990-996.
[19]Liu Z,Huang C W,Luo JW.A systematic investigation of lateral estimation using various interpolation approaches in conventional ultrasound imaging[J].IEEE Trans Ultrason Ferroelectr Freq Control,2017,64(8):1149-1160.
[20]Udesen J,Jensen J A.Investigation of transverse oscillation method[J].IEEE Trans Ultrason Ferroelectr Freq Control,2006,53(5):959-971.
[21]Rao M,Varghese T.Spatial angular compounding for elastography without the incompressibility assumption[J]Ultrason Imaging,2005,27(4):256-270.
[22]Rao M,Varghese T.Estimation of the optimal maximum beam angle and angular increment for normal and shear strain estimation[J].IEEE Trans Biomed Eng,2009,56(3):760-769.
[23]Hansen HHG,Lopata RGP,De Korte CL.Noninvasive carotid strain imaging using angular compounding at large beam steered angles:Validation in vessel phantoms[J].IEEE Trans Med Imaging,2009,28(6):872-880.
[24]Hansen HHG,Lopata RGP,Idzenga T,et al.Full 2Ddisplacement vector and strain tensor estimation for superficial tissue using beam-steered ultrasound imaging[J].,2010,55(11):3201-3218.
[25]Jensen JA.FIELD:a program for simulating ultrasound systems[J].Med Biol Eng Comput,1996,34(1):351-352.
[26]Jensen J A,Svendsen N B.Calculation of pressure fields from arbitrarily shaped,apodized,and excited ultrasound transducers[J].IEEE Trans Ultrason Ferroelectr Freq Control,1992,39(2):262-267.
[27]Luo JW,Bai J,He P,et al.Axial strain calculation using a lowpass digital differentiator in ultrasound elastography[J].IEEETrans Ultrason Ferroelectr Freq Control,2004,51(9):1119-1127.
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