本文選題：CT成像 + X射線能譜估計(jì)�。� 參考：《光譜學(xué)與光譜分析》2017年07期

【摘要】：在CT硬化偽影校正、雙能CT圖像重建以及CT輻射劑量計(jì)算等實(shí)際應(yīng)用中,X射線的能譜信息具有重要的作用。然而,由于透射測量方程組系數(shù)矩陣的病態(tài)性、X光子的統(tǒng)計(jì)漲落和噪聲的干擾,使得EM等能譜估計(jì)方法難以獲得較精細(xì)的能譜刻畫。針對(duì)該問題,提出一種基于加權(quán)TV正則化的X射線CT系統(tǒng)能譜估計(jì)方法。首先采用能譜能量范圍內(nèi)帶有不同K-edge的材料作為體模以降低投影測量方程之間的相關(guān)性。然后,利用CT成像系統(tǒng)的幾何參數(shù)來獲取投影測量數(shù)據(jù)所對(duì)應(yīng)的準(zhǔn)確透射長度信息來減小投影方程的測量誤差。最后,綜合利用透射衰減測量數(shù)據(jù)的保真性、軔致輻射能譜部分的連續(xù)性、特征輻射能譜部分的離散性、能譜的非負(fù)性和歸一性以及平均有效衰減系數(shù)等信息,使用加權(quán)TV正則化方法建立目標(biāo)函數(shù),利用正則化理論中的L曲線準(zhǔn)則通過黃金分割參數(shù)搜索策略求得最優(yōu)正則化參數(shù)及對(duì)應(yīng)的能譜估計(jì)結(jié)果。分別通過不同統(tǒng)計(jì)波動(dòng)模型下的仿真能譜和實(shí)際測量數(shù)據(jù)對(duì)算法性能進(jìn)行了驗(yàn)證,結(jié)果表明該方法與EM等方法相比,不受初始能譜的影響,有效提高了能譜估計(jì)結(jié)果的穩(wěn)定性和準(zhǔn)確性。
[Abstract]:X-ray energy spectrum information plays an important role in the correction of CT hardening artifacts, reconstruction of dual-energy CT images and calculation of CT radiation dose.However, due to the ill-conditioned fluctuation of X photon and the interference of noise in the coefficient matrix of transmission measurement equations, it is difficult to obtain a more precise characterization of the energy spectrum by the EM equal-energy spectrum estimation method.To solve this problem, an energy spectrum estimation method for X ray CT system based on weighted TV regularization is proposed.Firstly, materials with different K-edge in the energy range of energy spectrum are used as bulk modes to reduce the correlation between the projection measurement equations.Then, the geometric parameters of the CT imaging system are used to obtain the accurate transmission length information corresponding to the projection measurement data to reduce the measurement error of the projection equation.Finally, the information of fidelity of transmission attenuation measurement data, continuity of Bremsstrahlung energy spectrum, discreteness of characteristic radiation spectrum, non-negative and normalization of energy spectrum, and average effective attenuation coefficient are synthetically used.The objective function is established by using weighted TV regularization method, and the optimal regularization parameters and the corresponding energy spectrum estimation results are obtained by using the L-curve criterion in regularization theory through the golden section parameter search strategy.The performance of the algorithm is verified by the simulation spectra and the actual measurement data under different statistical fluctuation models. The results show that the proposed method is not affected by the initial energy spectrum compared with EM and other methods.The stability and accuracy of the energy spectrum estimation results are improved effectively.
【作者單位】： 解放軍信息工程大學(xué)信息系統(tǒng)工程學(xué)院;北京大學(xué)重離子物理研究所;
【基金】：國家自然科學(xué)基金項(xiàng)目(61372172)資助
【分類號(hào)】：O434.1

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