Du Yong, Tsui Benjamin M W, Frey Eric C
Department of Radiology, The Johns Hopkins University, Baltimore, MD 21287, USA.
IEEE Trans Med Imaging. 2005 Aug;24(8):969-76. doi: 10.1109/TMI.2005.850547.
Partial volume (PV) effects degrade the quantitative accuracy of SPECT brain images. In this paper, we extended a PV compensation (PVC) method originally developed for brain PET, the geometric transfer matrix (GTM) method, to brain SPECT using iterative reconstruction-based compensations. In the GTM method a linear transform between the true regional activities and the measured results was assumed. Elements of the GTM were calculated by projecting and reconstructing maps with uniform regions representing different structures. However, with iterative reconstruction methods, especially when reconstruction-based compensation for detector response was applied, we found that it was important to treat the region maps as a perturbation to the reconstructed image in the estimation of the GTM. This modified method, termed perturbation-based GTM (pGTM) was evaluated using Monte Carlo (MC) simulated and experimentally acquired data. Results showed great improvement of the quantitative accuracy in brain SPECT imaging. For MC simulated data, PVC using pGTM reduced the underestimation of striatal activities from 30% to less than 1.2%. For experimental data, PVC using pGTM reduced the underestimation of striatal activities from 36% to less than 7.8%. The underestimation of the striatum to background activity ratio was also improved from 31% to 2.7%.
部分容积（PV）效应会降低单光子发射计算机断层扫描（SPECT）脑图像的定量准确性。在本文中，我们将最初为脑正电子发射断层扫描（PET）开发的一种PV补偿（PVC）方法——几何传递矩阵（GTM）方法，扩展到使用基于迭代重建的补偿的脑SPECT。在GTM方法中，假定真实区域活性与测量结果之间存在线性变换。GTM的元素是通过对代表不同结构的均匀区域的图谱进行投影和重建来计算的。然而，对于迭代重建方法，特别是当应用基于重建的探测器响应补偿时，我们发现在GTM估计中，将区域图谱视为对重建图像的扰动非常重要。这种改进后的方法称为基于扰动的GTM（pGTM），并使用蒙特卡罗（MC）模拟数据和实验采集的数据进行了评估。结果表明，脑SPECT成像的定量准确性有了很大提高。对于MC模拟数据，使用pGTM的PVC将纹状体活性的低估从30%降低到了不到1.2%。对于实验数据，使用pGTM的PVC将纹状体活性的低估从36%降低到了不到7.8%。纹状体与背景活性比值的低估也从31%提高到了2.7%。
