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cryo-EM-denoising-pytorch-v1

Principle

Background Info

Cryo-electron microscopy has gradually become an important technology in the field of structural biology. With the development and improvement of hardware and software, more and more molecular biological structures close to atomic resolution have been resolved. In order to obtain an accurate and reliable three-dimensional structure, it is a very important and critical step to perform cluster analysis on the projection images of cryo-electron microscopy.

Siamese Network

  1. Randomly choose two images from the dataset, in one cluster or not.

  2. Send two images into the same networks (feature extractor), and obtain two latent vectors.

  3. Use the Contrastive Loss Function to evaluate the dissimilarity between two images.

$$L = \frac{1}{2N}\sum_{n=1}^N(1-y)d^2+(y)\max(\text{margin}-d,0)^2$$

y = 1 stands for the two images that come from different clusters, y = 0 stands for the two images that come from the same clusters.

  1. Kmeans are used to assign new labels.
# Siamese Network
class SiameseNetwork(nn.Module):
    def __init__(self):
        super().__init__()
        self.cnn1 = nn.Sequential(
            nn.ReflectionPad2d(1),
            nn.Conv2d(1,4,kernel_size=3),
            nn.ReLU(inplace=True),
            nn.BatchNorm2d(4),

            nn.ReflectionPad2d(1),
            nn.Conv2d(4,8,kernel_size=3),
            nn.ReLU(inplace=True),
            nn.BatchNorm2d(8),

            nn.ReflectionPad2d(1),
            nn.Conv2d(8,8,kernel_size=3),
            nn.ReLU(inplace=True),
            nn.BatchNorm2d(8),
        )

        self.fc1 = nn.Sequential(
            nn.Linear(8*64*64,500),
            nn.ReLU(inplace=True),

            nn.Linear(500,100),
            nn.ReLU(inplace=True),

            nn.Linear(100,20)
        )

    def forward_once(self,x):
        output = self.cnn1(x)
        output = output.view(output.size()[0],-1)
        output = self.fc1(output)
        return output

    def forward(self,input1,input2):
        output1 = self.forward_once(input1)
        output2 = self.forward_once(input2)
        return output1, output2 
        
# ContrastiveLoss Function
class ContrastiveLoss(torch.nn.Module):
    def __init__(self,margin=2):
        super(ContrastiveLoss, self).__init__()
        self.margin = margin
  
    def forward(self,output1,output2,label):
        euclidean_distance = F.pairwise_distance(output1,output2,keepdim=True)
        loss_constrastive = torch.mean((1-label)*torch.pow(euclidean_distance,2)+
                        (label)*torch.pow(torch.clamp(self.margin-euclidean_distance,min=0.0),2))
        return loss_constrastive

Result

Loss

loss

Clustering

cluster

Denoising Result

average

Usage

pip install -r requirements.txt

python main.py -h
usage: main.py [-h] [-c CLUSTER_NUM] [-g GPU] [-l LEARNING_RATE]
               [-e EPOCH_NUM] [-b BATCH_SIZE] [-r ROUND_NUM] [-d DATASET_DIR]

Cryo-EM Images Denoising v1

optional arguments:
  -h, --help            show this help message and exit
  -c CLUSTER_NUM, --cluster_num CLUSTER_NUM
  -g GPU, --gpu GPU
  -l LEARNING_RATE, --learning_rate LEARNING_RATE
  -e EPOCH_NUM, --epoch_num EPOCH_NUM
  -b BATCH_SIZE, --batch_size BATCH_SIZE
  -r ROUND_NUM, --round_num ROUND_NUM
  -d DATASET_DIR, --dataset_dir DATASET_DIR