Giraldo Juan C Ramirez, Kelm Zachary S, Guimaraes Luis S, Yu Lifeng, Fletcher Joel G, Erickson Bradley J, McCollough Cynthia H
CT Clinical Innovation Center, Dept. of Radiology, Mayo Clinic, Rochester, MN, USA.
Annu Int Conf IEEE Eng Med Biol Soc. 2009;2009:3529-32. doi: 10.1109/IEMBS.2009.5334714.
Optimal noise control is important for improving image quality and reducing radiation dose in computed tomography. Here we investigated two image space based nonlinear filters for noise reduction: the bilateral filter (BF) and the nonlocal means (NLM) algorithm. Images from both methods were compared against those from a commercially available weighted filtered backprojection (WFBP) method. A standard phantom for quality assurance testing was used to quantitatively compare noise and spatial resolution, as well as low contrast detectability (LCD). Additionally, an image dataset from a patient's abdominal CT exam was used to assess the effectiveness of the filters on full dose and simulated half dose acquisitions. We found that both the BF and NLM methods improve the tradeoff between noise and high contrast spatial resolution with no significant difference in LCD. Results from the patient dataset demonstrated the potential of dose reduction with the denoising methods. Care must be taken when choosing the NLM parameters in order to minimize the generation of artifacts that could possibly compromise diagnostic value.
优化噪声控制对于提高计算机断层扫描中的图像质量和降低辐射剂量至关重要。在此，我们研究了两种基于图像空间的非线性降噪滤波器：双边滤波器（BF）和非局部均值（NLM）算法。将这两种方法得到的图像与商业加权滤波反投影（WFBP）方法得到的图像进行比较。使用一个用于质量保证测试的标准体模对噪声、空间分辨率以及低对比度可探测性（LCD）进行定量比较。此外，还使用了来自患者腹部CT检查的图像数据集来评估滤波器在全剂量和模拟半剂量采集上 的有效性。我们发现，BF和NLM方法都改善了噪声与高对比度空间分辨率之间的权衡，在LCD方面没有显著差异。患者数据集的结果表明了降噪方法在降低剂量方面的潜力。选择NLM参数时必须谨慎，以尽量减少可能会影响诊断价值的伪影产生。
