Submitted Successfully!
Thank you for your contribution! You can also upload a video entry or images related to this topic.
Ver. Summary Created by Modification Content Size Created at Operation
1 -- 1348 2023-06-02 11:21:52 |
2 format correct Meta information modification 1348 2023-06-05 03:39:02 |

Video Upload Options

Do you have a full video?


Are you sure to Delete?
If you have any further questions, please contact Encyclopedia Editorial Office.
Lin, W.; Miao, K. Channel Correction for Anterior Cruciate Ligament Tear. Encyclopedia. Available online: (accessed on 10 December 2023).
Lin W, Miao K. Channel Correction for Anterior Cruciate Ligament Tear. Encyclopedia. Available at: Accessed December 10, 2023.
Lin, Weilun, Kehua Miao. "Channel Correction for Anterior Cruciate Ligament Tear" Encyclopedia, (accessed December 10, 2023).
Lin, W., & Miao, K.(2023, June 02). Channel Correction for Anterior Cruciate Ligament Tear. In Encyclopedia.
Lin, Weilun and Kehua Miao. "Channel Correction for Anterior Cruciate Ligament Tear." Encyclopedia. Web. 02 June, 2023.
Channel Correction for Anterior Cruciate Ligament Tear

The anterior cruciate ligament (ACL) is critical for controlling the motion of the knee joint, but it is prone to injury during sports activities and physical work. If left untreated, ACL injuries can lead to various pathologies such as meniscal damage and osteoarthritis. 

deep learning medical image analysis anterior cruciate ligament magnetic resonance imaging

1. Introduction

The knee is a hinge joint held together by four ligaments. The ligaments are a structure in the knee that hold the bones together and help control joint motion. As shown in Figure 1, there is a ligament (collateral ligament) on each side of the knee and two ligaments deep within the knee. The anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) are the two ligaments in the knee that cross each other. The two ligaments attach to the end of the thigh bone on one side and the top of the tibia on the other.
Figure 1. Knee joint structure.
The anterior gliding of the tibia over the femur is controlled by the ACL, which essentially prevents too much forward motion [1]. A certain degree of anterior motion is necessary for the knee joint, but too much activity may damage other knee structures.
ACL injuries are prevalent in sports activities [2][3], and their incidence of has been on the rise in the US [4]. The cost of diagnosis and treatment of ACL injuries surpasses USD 7 billion annually, directly or indirectly [5]. If left untreated, ACL injuries can cause knee instability, meniscal damage [6], and osteoarthritis [7], significantly impacting an individual’s health and daily life. Raising awareness about ACL injuries and encouraging athletes to take necessary precautions is vital. Timely and accurate diagnosis in combination with effective treatment are essential for preventing further damage and improving outcomes for patients.
X-ray, ultrasound, and computed tomography (CT) can usually diagnose ACL injuries, and magnetic resonance imaging (MRI) is often used in the medical field [8]. MRI has become the imaging technique of choice for evaluating the ACL because it is more accurate and sensitive for that ligament [9]. Tears in the ACL are generally rated in three grades. Grade 0 means that the ACL is intact, grade 1 is a partial tear, and grade 2 is a complete tear [10].

2. Medical Image Classification

With the increasing development of machine learning, good results have been achieved on traditional image analysis tasks with the help of computers. Therefore, more people are focusing on applications in various fields, such as face recognition, vehicle detection, and other tasks. Medical image analysis has been of great help in medical research, clinical disease diagnosis, and treatment. Computer-aided methods, called Computer-Aided Detection/Diagnosis (CAD), have become a trend in this field. Among them, medical image classification generally belongs to the field of Computer-Aided Diagnosis and is one of its most popular applications.
CAD based on medical images can be traced back to the 1960s. To identify cardiac lesions, Becker et al. [11] input X-ray images into a computer to calculate the cardiothoracic ratio. Medical image-based CAD was developed as a direct result of this. Lee et al. [12] proposed classifying ultrasound liver images by selecting fractal feature vectors based on the M-band wavelet transform. Paredes et al. [13] obtained small square windows, i.e., local representations, from images and combined this approach with k-nearest neighbor techniques to achieve state-of-the-art results. Caicedo et al. [14] used bag-of-features combined with SVM to select appropriate kernel functions for processing. Moreover, they conducted extensive experiments on the use of different strategies and analyzed the impact of each configuration on the classification results.
Medical imaging has evolved more rapidly with the introduction of convolutional neural networks. The lung nodule classification problem was addressed in [15]. A multiscale CNN extracts discriminative features from alternately stacked layers while capturing nodule heterogeneity. Payan et al. [16] used sparse autoencoders and 3DCNNs to diagnose Alzheimer’s disease, and the results demonstrated that 3DCNNs produced state-of-the-art results. Gong et al. [17] extended the interpretability of deep networks and implemented complex spatial variations by deformable Gabor convolution (DGConv). This approach improved the representativeness and robustness of complex objects, resulting in a Deformable Gabor Feature Network (DGFN). Wei et al. [18] considered histopathology image classification as part of course learning and proposed a simple course learning method based on this, which resulted in a 4.5% improvement in the AUC compared with vanilla training.

3. Attention Mechanism

Attention mechanisms are designed to mimic the ability of humans to find salient regions in a scene, and such mechanisms can be used to highlight a specific part of the feature map by weighting the feature map. Attention mechanisms are usually classified into channel attention mechanisms, spatial attention mechanisms, temporal attention mechanisms, branching attention mechanisms, channel spatial attention mechanisms, and spatio-temporal attention mechanisms [19]. Spatial attention mechanisms, channel attention mechanisms, and hybrid domain attention mechanisms are more commonly used in image analysis.
The spatial attention mechanism starts from finding regions on the image spatial domain that are helpful for the task. For instance, according to [20], it was suggested that Spatial Transformer Networks (STN) should be able to learn how to adaptively spatially transform various data to obtain spatial transformation invariance.
On the other hand, the channel attention mechanism calculates the weight of each channel in the network to form the attention on the channel domain. Hu et al. [21] weighted the original features by dimensionality using a three-step operation of the squeeze, excitation, and attention on SeNet.
Woo et al. [22] designed the Convolutional Block Attention Module (CBAM) by combining the spatial and channel attention mechanisms. A simple and efficient forward CNN attention module is designed by combining two different dimensions, spatial and channel, to generate an attention map.
In medical image analysis, Schlempe et al. [23] proposed a novel Attention Gate (AG) model for medical imaging, which can automatically learn to focus on target structures of different shapes and sizes. An interactive attention mechanism was developed by Dai et al. [24] to implicitly instruct the network to focus on pathological tissue in multimodal data. Tao et al. [25] introduced an inter-slice contextual attention mechanism and an intra-slice spatial attention mechanism in lesion detection to improve model performance using fewer slices.

4. Loss Function

The loss function is used to evaluate the difference between the output and true label, which is the objective optimization function of the model. The smaller the loss, i.e., the closer the output is to the accurate label, the better the model works.
The standard loss functions in image classification are the 0–1 loss function, the binary cross-entropy loss function, and the multiclassification cross-entropy loss function. The 0–1 loss function is a discontinuous segmentation function, which is challenging to solve due to its minimization problem. Since Rubinstein et al. [26] proposed an adaptive algorithm using cross-entropy to estimate the probability of rare events in complex random networks, cross-entropy loss has also been applied to classification tasks [27]. In the time since then, many improvements have been made to cross-entropy. Liu et al. [28] proposed that large-margin softmax (L-Softmax) loss encourages the learning of intra-class compactness and inter-class separation features. Circle loss was proposed by Sun et al. [29] to re-weight those similarity scores that were not optimized to improve pair-based similarity.
Lin et al. [30] proposed focal loss for unbalanced samples to solve the complicated training problem by assigning relatively large weights to the losses of complex samples in the unbalanced dataset. Based on this, Li et al. [31] proposed GFocal loss to turn the labels into continuous values between 0 and 1, using the expanded form of focal loss on continuous labels to process them.
In medical imaging, Mazumdar et al. [32] proposed a new composite loss function for medical image segmentation by combining the Dice, focus, and Hausdorff distance loss functions. This function handles extreme class imbalances and directly optimizes Dice score and HD, thus significantly improving segmentation accuracy. According to the sequential nature of the knee injury classes, Chen et al. [33] developed a novel ordinal loss for the detection of knee osteoarthritis. This loss imposes a greater penalty for misclassification with a greater distance between the actual knee injury class and the predicted knee injury class. Liu et al. [34] addressed the drawback that the ordinal loss cannot be varied by proposing an adaptive ordinal weight adjustment strategy on this basis.


  1. Brantigan, O.C.; Voshell, A.F. The Mechanics of the Ligaments and Menisci of the Knee Joint. J. Bone Jt. Surg. Am. 1941, 23, 44–66.
  2. Agel, J.; Arendt, E.; Bershadsky, B. Anterior Cruciate Ligament Injury in National Collegiate Athletic Association Basketball and Soccer: A 13-Year Review. Am. J. Sports Med. 2005, 33, 524–530.
  3. Pujol, N.; Blanchi, M.; Chambat, P. The Incidence of Anterior Cruciate Ligament Injuries Among Competitive Alpine Skiers: A 25-year Investigation. Am. J. Sports Med. 2007, 35, 1070–1074.
  4. Herzog, M.; Marshall, S.; Lund, J.; Pate, V.; Mack, C.; Spang, J. Trends in Incidence of ACL Reconstruction and Concomitant Procedures Among Commercially Insured Individuals in the United States, 2002–2014. Sports Health Multidiscip. Approach 2018, 10, 523–531.
  5. Kaeding, C.; Léger-St-Jean, B.; Magnussen, R. Epidemiology and Diagnosis of Anterior Cruciate Ligament Injuries. Clin. Sports Med. 2016, 36, 1–8.
  6. Gupta, R.; Singhal, A.; Rai, A.; Shail, S.; Masih, G. Strong association of meniscus tears with complete Anterior Cruciate Ligament (ACL) injuries relative to partial ACL injuries. J. Clin. Orthop. Trauma 2021, 23, 101671.
  7. Simon, D.; Mascarenhas, R.; Saltzman, B.; Rollins, M.; Bach, B.; Macdonald, P. The Relationship between Anterior Cruciate Ligament Injury and Osteoarthritis of the Knee. Adv. Orthop. 2015, 2015, 928301.
  8. Schwenke, M.; Singh, M.; Chow, B. Anterior Cruciate Ligament and Meniscal Tears: A Multi-modality Review. Appl. Radiol. 2020, 49, 42–49.
  9. Roberts, C.; Towers, J.; Spangehl, M.; Carrino, J.; Morrison, W. Advanced MR Imaging of the Cruciate Ligaments. Radiol. Clin. N. Am. 2007, 45, 1003–1016.
  10. Moon, S.; Hong, S.; Choi, J.Y.; Jun, W.; Choi, J.A.; Park, E.A.; Kang, H.; Kwon, J. Grading Anterior Cruciate Ligament Graft Injury after Ligament Reconstruction Surgery: Diagnostic Efficacy of Oblique Coronal MR Imaging of the Knee. Korean J. Radiol. Off. J. Korean Radiol. Soc. 2008, 9, 155–161.
  11. Becker, H.C.; Nettleton, W.J.; Meyers, P.H.; Sweeney, J.W.; Nice, C.M. Digital Computer Determination of a Medical Diagnostic Index Directly from Chest X-Ray Images. IEEE Trans. Biomed. Eng. 1964, BME-11, 67–72.
  12. Lee, W.L.; Chen, Y.C.; Hsieh, K.S. Ultrasonic liver tissue classification by fractal feature vector based on M-band wavelet transform. IEEE Trans. Med. Imaging 2003, 22, 382–392.
  13. Paredes, R.; Keysers, D.; Lehmann, T.; Wein, B.; Ney, H.; Vidal, E. Classification of Medical Images Using Local Representations. In Bildverarbeitung für die Medizin 2002; Springer: Berlin/Heidelberg, Germany, 2002.
  14. Caicedo, J.; Cruz-Roa, A.; González, F. Histopathology Image Classification Using Bag of Features and Kernel Functions. In AIME 2009: Artificial Intelligence in Medicine; Springer: Berlin/Heidelberg, Germany, 2009; pp. 126–135.
  15. Shen, W.; Zhou, M.; Yang, F.; Yang, C.; Tian, J. Multi-scale Convolutional Neural Networks for Lung Nodule Classification. In IPMI 2015: Information Processing in Medical Imaging; Springer: Cham, Switzerland, 2015; Volume 24, pp. 588–599.
  16. Payan, A.; Montana, G. Predicting Alzheimer’s disease: A neuroimaging study with 3D convolutional neural networks. In Proceedings of the ICPRAM 2015—4th International Conference on Pattern Recognition Applications and Methods, Lisbon, Portugal, 10–12 January 2015; Volume 2.
  17. Gong, X.; Xia, X.; Zhu, W.; Zhang, B.; Doermann, D.S.; Zhuo, L. Deformable Gabor Feature Networks for Biomedical Image Classification. arXiv 2020, arXiv:2012.04109. Available online: (accessed on 10 March 2023).
  18. Wei, J.; Suriawinata, A.; Ren, B.; Liu, X.; Lisovsky, M.; Vaickus, L.; Brown, C.; Baker, M.; Nasir-Moin, M.; Tomita, N.; et al. Learn like a Pathologist: Curriculum Learning by Annotator Agreement for Histopathology Image Classification. In Proceedings of the 2021 IEEE Winter Conference on Applications of Computer Vision (WACV), Waikoloa, HI, USA, 3–8 January 2021; pp. 2472–2482.
  19. Guo, M.H.; Xu, T.X.; Liu, J.J.; Liu, Z.N.; Jiang, P.T.; Mu, T.J.; Zhang, S.H.; Martin, R.; Cheng, M.M.; Hu, S.M. Attention Mechanisms in Computer Vision: A Survey. Comput. Vis. Media 2021, 8, 331–368.
  20. Jaderberg, M.; Simonyan, K.; Zisserman, A.; Kavukcuoglu, K. Spatial Transformer Networks. In Proceedings of the NIPS, Montreal, QB, Canada, 7–12 December 2015.
  21. Hu, J.; Shen, L.; Sun, G. Squeeze-and-Excitation Networks. arXiv 2017, arXiv:1709.01507. Available online: (accessed on 10 March 2023).
  22. Woo, S.; Park, J.; Lee, J.Y.; Kweon, I.S. CBAM: Convolutional Block Attention Module. In Proceedings of the European Conference on Computer Vision (ECCV), Munich, Germany, 8–14 September 2018.
  23. Schlemper, J.; Oktay, O.; Schaap, M.; Heinrich, M.; Kainz, B.; Glocker, B.; Rueckert, D. Attention Gated Networks: Learning to Leverage Salient Regions in Medical Images. Med. Image Anal. 2019, 53, 197–207.
  24. Dai, Y.; Gao, Y.; Liu, F.; Fu, J. Mutual Attention-based Hybrid Dimensional Network for Multimodal Imaging Computer-aided Diagnosis. arXiv 2022, arXiv:2201.09421.
  25. Tao, Q.; Ge, Z.; Cai, J.; Yin, J.; See, S. Improving Deep Lesion Detection Using 3D Contextual and Spatial Attention. In MICCAI 2019: Medical Image Computing and Computer Assisted Intervention; Springer: Cham, Switzerland, 2019; pp. 185–193.
  26. Rubinstein, R.Y. The Cross-Entropy Method for Combinatorial and Continuous Optimization. Methodol. Comput. Appl. Probab. 1999, 1, 127–190.
  27. Mannor, S.; Peleg, D.; Rubinstein, R. The Cross Entropy Method for Classification. In ICML ’05: Proceedings of the 22nd International Conference on Machine Learning; Association for Computing Machinery: New York, NY, USA, 2005; pp. 561–568.
  28. Liu, W.; Wen, Y.; Yu, Z.; Yang, M. Large-Margin Softmax Loss for Convolutional Neural Networks. In Proceedings of the 33rd International Conference on Machine Learning, New York, NY, USA, 19–24 June 2016; pp. 507–516.
  29. Sun, Y.; Cheng, C.; Zhang, Y.; Zhang, C.; Zheng, L.; Wang, Z.; Wei, Y. Circle Loss: A Unified Perspective of Pair Similarity Optimization. In Proceedings of the 2020 IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), Seattle, WA, USA, 13–19 June 2020; pp. 6397–6406.
  30. Lin, T.Y.; Goyal, P.; Girshick, R.; He, K.; Dollár, P. Focal Loss for Dense Object Detection. In Proceedings of the 2017 IEEE International Conference on Computer Vision (ICCV), Venice, Italy, 22–29 October 2017; pp. 2999–3007.
  31. Li, X.; Wang, W.; Wu, L.; Chen, S.; Hu, X.; Li, J.; Tang, J.; Yang, J. Generalized Focal Loss: Learning Qualified and Distributed Bounding Boxes for Dense Object Detection. In Proceedings of the NeurIPS, Virtual, 6–12 December 2020.
  32. Mazumdar, I.; Mukherjee, J. Fully Automatic MRI Brain Tumor Segmentation Using Efficient Spatial Attention Convolutional Networks with Composite Loss. Neurocomputing 2022, 500, 243–254.
  33. Chen, P.; Gao, L.; Shi, X.; Allen, K.; Yang, L. Fully Automatic Knee Osteoarthritis Severity Grading Using Deep Neural Networks with a Novel Ordinal Loss. Comput. Med. Imaging Graph. 2019, 75, 84–92.
  34. Liu, W.; Ge, T.; Luo, L.; Hong, P.; Xu, X.; Chen, Y.; Zhuang, Z. A Novel Focal Ordinal Loss for Assessment of Knee Osteoarthritis Severity. Neural Process. Lett. 2022, 54, 5199–5224.
Contributors MDPI registered users' name will be linked to their SciProfiles pages. To register with us, please refer to : ,
View Times: 107
Revisions: 2 times (View History)
Update Date: 05 Jun 2023