Dierkes Thomas, Grosenick Dirk, Moesta K Thomas, Möller Michael, Schlag Peter M, Rinneberg Herbert, Arridge Simon
Department of Computer Science, University College London, Gower Street, London WC1E 6BT, UK.
Phys Med Biol. 2005 Jun 7;50(11):2519-42. doi: 10.1088/0031-9155/50/11/006. Epub 2005 May 18.
We report on the reconstruction of absorption and reduced scattering coefficients of breast tissue in vivo of a patient with mastopathic disease. Distributions of times of flight of photons through the compressed breast were recorded by paraxial scanning. From data measured at four different source-detector offsets optical properties were reconstructed within the linear Rytov approximation by a fast inverse Fourier space method. Low-pass filtering in Fourier space was employed to remove excessive noise from high spatial frequency components and to reduce the computational efforts by a factor of 3, typically. The mammograms displaying reconstructed absorption and reduced scattering coefficients were compared with projection mammograms either obtained by time-window analysis of experimental data or based on average absorption and reduced scattering coefficients which were derived from measured temporal point spread functions within a simple homogeneous model. All inhomogeneities which were visible in the projection mammograms and which could be associated with specific breast tissue compartments could be correlated with inhomogeneities in the reconstructed absorption coefficient. In particular, the mastopathic disease was detected in the reconstructed absorption mammogram. In order to assess reliability of optical properties reconstructed from data obtained by paraxial scanning, corresponding phantom experiments and reconstructions of phantom optical properties were carried out. Because of the limited angular range sampled by the in vivo and phantom measurements, considerable blurring of the absorption coefficient occurs along the compression direction, compromising longitudinal resolution.
我们报告了对一名患有乳腺病的患者体内乳腺组织吸收系数和约化散射系数的重建情况。通过旁轴扫描记录光子穿过压缩乳腺的飞行时间分布。利用快速傅里叶逆空间方法，在Rytov线性近似范围内，根据在四个不同源 - 探测器偏移量下测量的数据重建光学特性。在傅里叶空间中采用低通滤波来去除高空间频率分量中的过多噪声，并通常将计算量减少三分之一。将显示重建的吸收系数和约化散射系数的乳房X线照片与通过对实验数据进行时间窗分析获得的投影乳房X线照片，或基于从简单均匀模型内测量的时间点扩展函数导出的平均吸收系数和约化散射系数的投影乳房X线照片进行比较。在投影乳房X线照片中可见的、可与特定乳腺组织区域相关联的所有不均匀性，都可以与重建吸收系数中的不均匀性相关联。特别是，在重建的吸收乳房X线照片中检测到了乳腺病。为了评估从旁轴扫描获得的数据重建的光学特性的可靠性，进行了相应的体模实验和体模光学特性重建。由于体内和体模测量所采样的角度范围有限，吸收系数在压缩方向上会出现相当大的模糊，从而影响纵向分辨率。
