Kawaguchi Ren, Minagawa Tomoya, Hori Kensuke, Hashimoto Takeyuki
Department of Graduate School of Health Sciences, Kyorin University, 5-4-1 Shimorenjaku, Mitaka City, Tokyo, 181-8612, Japan.
Department of Radiology, Toho University Ohashi Medical Center, 2-22-36, Ohashi, Meguro-Ku, Tokyo, 153-8514, Japan.
Int J Comput Assist Radiol Surg. 2025 May 15. doi: 10.1007/s11548-025-03378-1.
PURPOSE: Deep learning has been widely used in research on sparse-view computed tomography (CT) image reconstruction. While sufficient training data can lead to high accuracy, collecting medical images is often challenging due to legal or ethical concerns, making it necessary to develop methods that perform well with limited data. To address this issue, we explored the use of nonmedical images for pre-training. Therefore, in this study, we investigated whether fractal images could improve the quality of sparse-view CT images, even with a reduced number of medical images. METHODS: Fractal images generated by an iterated function system (IFS) were used for nonmedical images, and medical images were obtained from the CHAOS dataset. Sinograms were then generated using 36 projections in sparse-view and the images were reconstructed by filtered back-projection (FBP). FBPConvNet and WNet (first module: learning fractal images, second module: testing medical images, and third module: learning output) were used as networks. The effectiveness of pre-training was then investigated for each network. The quality of the reconstructed images was evaluated using two indices: structural similarity (SSIM) and peak signal-to-noise ratio (PSNR). RESULTS: The network parameters pre-trained with fractal images showed reduced artifacts compared to the network trained exclusively with medical images, resulting in improved SSIM. WNet outperformed FBPConvNet in terms of PSNR. Pre-training WNet with fractal images produced the best image quality, and the number of medical images required for main-training was reduced from 5000 to 1000 (80% reduction). CONCLUSION: Using fractal images for network training can reduce the number of medical images required for artifact reduction in sparse-view CT. Therefore, fractal images can improve accuracy even with a limited amount of training data in deep learning.
目的:深度学习已广泛应用于稀疏视图计算机断层扫描(CT)图像重建的研究中。虽然充足的训练数据能带来高精度,但由于法律或伦理问题,收集医学图像往往具有挑战性,因此有必要开发在有限数据下仍能良好运行的方法。为解决这一问题,我们探索了使用非医学图像进行预训练。因此,在本研究中,我们调查了分形图像是否能提高稀疏视图CT图像的质量,即使医学图像数量减少。 方法:由迭代函数系统(IFS)生成的分形图像用作非医学图像,医学图像取自CHAOS数据集。然后使用稀疏视图中的36个投影生成正弦图,并通过滤波反投影(FBP)重建图像。FBPConvNet和WNet(第一个模块:学习分形图像,第二个模块:测试医学图像,第三个模块:学习输出)用作网络。然后研究每个网络预训练的有效性。使用两个指标评估重建图像的质量:结构相似性(SSIM)和峰值信噪比(PSNR)。 结果:与仅使用医学图像训练的网络相比,用分形图像预训练的网络参数显示出伪影减少,从而提高了SSIM。在PSNR方面,WNet优于FBPConvNet。用分形图像预训练WNet产生了最佳图像质量,主训练所需的医学图像数量从5000减少到1000(减少了80%)。 结论:使用分形图像进行网络训练可以减少稀疏视图CT中减少伪影所需的医学图像数量。因此,即使在深度学习中训练数据量有限的情况下,分形图像也可以提高准确性。
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