Servicio de Radiofísica y Protección Radiológica, Hospital Universitario Virgen de la Arrixaca, Ctra. Madrid-Cartagena, 30120, El Palmar (Murcia), Spain.
J Digit Imaging. 2013 Jun;26(3):457-65. doi: 10.1007/s10278-012-9516-0.
In this paper, we consider the statistical characteristics of the so-called portal images, which are acquired prior to the radiotherapy treatment, as well as the noise that present the portal imaging systems, in order to analyze whether the well-known noise and image features in other image modalities, such as natural image, can be found in the portal imaging modality. The study is carried out in the spatial image domain, in the Fourier domain, and finally in the wavelet domain. The probability density of the noise in the spatial image domain, the power spectral densities of the image and noise, and the marginal, joint, and conditional statistical distributions of the wavelet coefficients are estimated. Moreover, the statistical dependencies between noise and signal are investigated. The obtained results are compared with practical and useful references, like the characteristics of the natural image and the white noise. Finally, we discuss the implication of the results obtained in several noise reduction methods that operate in the wavelet domain.
在本文中，我们研究了所谓的射野影像的统计特征，这些特征是在放射治疗之前获得的，以及射野成像系统中的噪声，以便分析在射野成像模式中是否可以找到其他图像模式（如自然图像）中众所周知的噪声和图像特征。这项研究在空间图像域、傅里叶域和最终的小波域中进行。对空间图像域中的噪声概率密度、图像和噪声的功率谱密度以及小波系数的边缘、联合和条件统计分布进行了估计。此外，还研究了噪声和信号之间的统计相关性。将获得的结果与实际且有用的参考资料进行了比较，例如自然图像和白噪声的特征。最后，我们讨论了在小波域中运行的几种降噪方法所得到的结果的意义。
