Id |
Subject |
Object |
Predicate |
Lexical cue |
T312 |
0-7 |
Sentence |
denotes |
Methods |
T313 |
9-28 |
Sentence |
denotes |
Data sets splitting |
T314 |
29-205 |
Sentence |
denotes |
We used the multi-modal data sets from four public data sets and one hospital (Youan hospital) in our research and split the hybrid data set in the following manner.For X-data: |
T315 |
206-348 |
Sentence |
denotes |
The CXR images of COVID-19 cases collected from the public CCD52 contained 212 patients diagnosed with COVID-19 and were resized to 512 × 512. |
T316 |
349-422 |
Sentence |
denotes |
Each image contained 1–2 suspected areas with inflammatory lesions (SAs). |
T317 |
423-522 |
Sentence |
denotes |
We also collected 5100 normal cases and 3100 pneumonia cases from another public data set (RSNA)53. |
T318 |
523-744 |
Sentence |
denotes |
In addition, The CXR images collected from the Youan hospital contained 45 cases diagnosed with COVID-19, 503 normal cases, 435 cases diagnosed with pneumonia (not COVID-19 patients), and 145 cases diagnosed as influenza. |
T319 |
745-851 |
Sentence |
denotes |
The CXR images collected from the Youan hospital were obtained using the Carestream DRX-Revolution system. |
T320 |
852-969 |
Sentence |
denotes |
All the CXR images of COVID-19 cases were analyzed by the two experienced radiologists to determine the lesion areas. |
T321 |
970-1149 |
Sentence |
denotes |
The X-data of the normal cases (XNPDS), that of the pneumonia cases (XPPDS), and that of the COVID-19 cases (XCPDS) from public data sets constituted the X public data set (XPDS). |
T322 |
1150-1333 |
Sentence |
denotes |
The X-data of the normal cases (XNHDS), that of the pneumonia cases (XPHDS), and that of the COVID-19 cases (XCHDS) from the Youan hospital constituted the X hospital data set (XHDS). |
T323 |
1334-1346 |
Sentence |
denotes |
For CT-data: |
T324 |
1347-1829 |
Sentence |
denotes |
We collected CT-data of 120 normal cases from a public lung CT-data set (LUNA16, a large data set for automatic nodule detection in the lungs54), which was a subset of LIDC-IDRI (The LIDC-IDRI contains a total of 1018 helical thoracic CT scans collected using manufacturers from eight medical imaging companies including AGFA Healthcare, Carestream Health, Inc., Fuji Photo Film Co., GE Healthcare, iCAD, Inc., Philips Healthcare, Riverain Medical, and Siemens Medical Solutions)55. |
T325 |
1830-1995 |
Sentence |
denotes |
It was confirmed by the two experienced radiologists from the Youan Hospital that no lesion areas of COVID-19, pneumonia, or influenza were present in the 120 cases. |
T326 |
1996-2138 |
Sentence |
denotes |
We also collected the CT-data of pneumonia cases from a public data set (images of COVID-19 positive and negative pneumonia patients: ICNP)56. |
T327 |
2139-2311 |
Sentence |
denotes |
The CT-data collected from the Youan hospital contained 95 patients diagnosed with COVID-19, 50 patients diagnosed with influenza and 215 patients diagnosed with pneumonia. |
T328 |
2312-2480 |
Sentence |
denotes |
The images of the CT scans collected from the Youan hospital were obtained using the PHILIPS Brilliance iCT 256 system (Which was also used for the LIDC-IDRI data set). |
T329 |
2481-2594 |
Sentence |
denotes |
The slice thickness of the CT scans was 5 mm, and the CT-data images were grayscale images with 512 × 512 pixels. |
T330 |
2595-2785 |
Sentence |
denotes |
Areas with 2–5 SAs were annotated by the two experienced radiologists using a rapid keystroke-entry format in the images for each case, and these areas ranged from 16 × 16 to 64 × 64 pixels. |
T331 |
2786-2937 |
Sentence |
denotes |
The CT-data of the normal cases (CTNPDS) and that of the pneumonia cases (CTPPDS) from the public data sets constituted the CT public data set (CTPDS). |
T332 |
2938-3182 |
Sentence |
denotes |
The CT-data of the COVID-19 cases from the Youan hospital (CTCHDS), the influenza cases from the Youan hospital (CTIHDS), and the normal cases from the Youan hospital (CTNHDS) constituted the CT hospital (clinically-diagnosed) data set (CTHDS). |
T333 |
3183-3211 |
Sentence |
denotes |
For clinical indicator data: |
T334 |
3212-3438 |
Sentence |
denotes |
Five clinical indicators (white blood cell count, neutrophil percentage, lymphocyte percentage, procalcitonin, C-reactive protein) of 95 COVID-19 cases were obtained from the Youan hospital, as shown in Supplementary Table 20. |
T335 |
3439-3695 |
Sentence |
denotes |
A total of 95 data pairs from the 95 COVID-19 cases (369 images of the lesion area and the 95 × 5 clinical indicators) were collected from the Youan hospital for the correlation analysis of the lesion areas of the COVID-19 and the five clinical indicators. |
T336 |
3696-3803 |
Sentence |
denotes |
The images of the SAs and the clinical indicator data constituted the correlation analysis data set (CADS). |
T337 |
3804-3923 |
Sentence |
denotes |
We split the XPDS, XHDS, CTPDS, CTHDS, and CADS into the training-validation (train-val) and test data sets using TTSF. |
T338 |
3924-4030 |
Sentence |
denotes |
The details of the hybrid data sets for the public data sets and Youan hospital data are shown in Table 1. |
T339 |
4031-4118 |
Sentence |
denotes |
The train-val part of CTHDS is referred to as CTHTS, and the test part is called CTHVS. |
T340 |
4119-4260 |
Sentence |
denotes |
The same naming scheme was adopted for XPDS, XHDS, CTPDS, and CADS, i.e., XPTS, XPVS, XHTS, XHVS, CTPTS, CTPVS, CATS, and CAVS, respectively. |
T341 |
4261-4445 |
Sentence |
denotes |
The training-validation part of the four public data sets and the hospital (Youan Hospital) data set were mixed for X-data and CT-data, which were named as XMTS and CTMTS respectively. |
T342 |
4446-4519 |
Sentence |
denotes |
While the test parts were split in the same way and named XMVS and CTMVS. |
T343 |
4521-4540 |
Sentence |
denotes |
Image preprocessing |
T344 |
4541-4723 |
Sentence |
denotes |
All image data (X-data and CT-data) in the DICOM format were loaded using the Pydicom library (version 1.4.0) and processed as arrays using the Numpy library (version 1.16.0).X-data: |
T345 |
4724-4907 |
Sentence |
denotes |
The two-dimensional array (x axis and y axis) of the image of the X-data (size of 512 × 512) was normalized to pixel values of 0–255 and stored in png format using the OpenCV library. |
T346 |
4908-4976 |
Sentence |
denotes |
Each preprocessed image was resized to 512 × 512 and had 3 channels. |
T347 |
4977-4985 |
Sentence |
denotes |
CT-data: |
T348 |
4986-5147 |
Sentence |
denotes |
The array of the CT-data was three-dimensional (x axis, y axis, and z axis), and the length of the z axis was ~300, which represented the number of image slices. |
T349 |
5148-5224 |
Sentence |
denotes |
Each image slice was two-dimensional (x axis and y axis, size of 512 × 512). |
T350 |
5225-5412 |
Sentence |
denotes |
As shown in Fig. 1b, the array of the image was divided into three groups in the z axis direction, and each group contained 100 image slices (each case was resampled to 300 image slices). |
T351 |
5413-5543 |
Sentence |
denotes |
The image slices in each group were processed using a window center of −600 and a window width of 2000 to extract the lung tissue. |
T352 |
5544-5682 |
Sentence |
denotes |
The images of the CT-data with 300 image slices were normalized to pixel values of 0–255 and stored in npy format using the Numpy library. |
T353 |
5683-5892 |
Sentence |
denotes |
A convolution filter was applied with three 1 × 1 convolution kernels to preprocess the CT-data, which is a trainable layer with the aim of normalizing the input; the image size was 512 × 512, with 3 channels. |
T354 |
5894-5928 |
Sentence |
denotes |
Annotation tool for medical images |
T355 |
5929-6054 |
Sentence |
denotes |
The server program of the annotation tool was deployed in a computer with large network bandwidth and abundant storage space. |
T356 |
6055-6190 |
Sentence |
denotes |
The client program of the annotation tool was deployed in the office computer of the experts, who were given unique user IDs for login. |
T357 |
6191-6351 |
Sentence |
denotes |
The interface of the client program had a built-in image viewer with a window size of 512 × 512 and an export tool for obtaining the annotations in text format. |
T358 |
6352-6575 |
Sentence |
denotes |
Multiple drawing tools were provided to annotate the lesion area in the images, including a rectangle tool for drawing a bounding box around the target, a polygon tool for outlining the target, and a circle tool the target. |
T359 |
6576-6646 |
Sentence |
denotes |
Multiple categories could be defined and assigned to the target areas. |
T360 |
6647-6873 |
Sentence |
denotes |
All annotations were stored in a structured query language (SQL) database, and the export tool was used to export the annotations to two common file formats (comma-separated values (csv) and JavaScript object notation (json)). |
T361 |
6874-6921 |
Sentence |
denotes |
The experts could share the annotation results. |
T362 |
6922-7059 |
Sentence |
denotes |
Since the size of the X-data and the CT slice-data were identical, the annotations for both data were performed with the annotation tool. |
T363 |
7060-7155 |
Sentence |
denotes |
Here we use one image slice of the CT-data as an example to demonstrate the annotation process. |
T364 |
7156-7225 |
Sentence |
denotes |
In this study, two experts were asked to annotate the medical images. |
T365 |
7226-7286 |
Sentence |
denotes |
The normal cases were reviewed and confirmed by the experts. |
T366 |
7287-7381 |
Sentence |
denotes |
The abnormal cases, including the COVID-19 and influenza cases, were annotated by the experts. |
T367 |
7382-7472 |
Sentence |
denotes |
Bounding boxes of the lesion areas in the images were annotated using the annotation tool. |
T368 |
7473-7533 |
Sentence |
denotes |
In general, each case contained 2–5 slices with annotations. |
T369 |
7534-7677 |
Sentence |
denotes |
The cases with the annotated slices were considered positive cases, and each case was assigned to a category (COVID-19 case or influenza case). |
T370 |
7678-7743 |
Sentence |
denotes |
The pipeline of the annotation was shown in Supplementary Fig. 1. |
T371 |
7745-7776 |
Sentence |
denotes |
Model architecture and training |
T372 |
7777-8008 |
Sentence |
denotes |
In this study, we proposed a modular CNNCF to identify the COVID-19 cases in the medical images and a CNNRF to determine the relationships between the lesion areas in the medical images and the five clinical indicators of COVID-19. |
T373 |
8009-8085 |
Sentence |
denotes |
Both proposed frameworks consisted of two units (ResBlock-A and ResBlock-B). |
T374 |
8086-8188 |
Sentence |
denotes |
The CNNCF and CNNRF had unique units, namely the control gate block and regressor block, respectively. |
T375 |
8189-8314 |
Sentence |
denotes |
Both frameworks were implemented using two NVIDIA GTX 1080TI graphics cards and the open-source PyTorch framework.ResBlock-A: |
T376 |
8315-8335 |
Sentence |
denotes |
As discussed in ref. |
T377 |
8336-8477 |
Sentence |
denotes |
57, the residual block is a CNN-based block that allows the CNN models to reuse features, thus accelerating the training speed of the models. |
T378 |
8478-8638 |
Sentence |
denotes |
In this study, we developed a residual block (ResBlock-A) that utilized a skip-connection for retaining features in different layers in the forward propagation. |
T379 |
8639-8851 |
Sentence |
denotes |
This block (Fig. 6a) consisted of a multiple-input multiple-output structure with two branches (an upper branch and a bottom branch), where input 1 and input 2 have the same size, but the values may be different. |
T380 |
8852-8945 |
Sentence |
denotes |
In contrast, output 1 and output 2 had the same size, but output 1 did not have a ReLu layer. |
T381 |
8946-9073 |
Sentence |
denotes |
The upper branch consisted of a max-pooling layer (Max-Pooling), a convolution layer (Conv 1 × 1), and a batch norm layer (BN). |
T382 |
9074-9308 |
Sentence |
denotes |
The Max-Pooling had a kernel size of 3 × 3 and a stride of 2 to downsample the input 1 for retaining the features and ensuring the same size as the output layer before the element-wise add operation was conducted in the bottom branch. |
T383 |
9309-9487 |
Sentence |
denotes |
The Conv 1 × 1 consisted of multiple 1 × 1 convolution kernels with the same number as that in the second convolution layer in the bottom branch to adjust the number of channels. |
T384 |
9488-9637 |
Sentence |
denotes |
The BN used a regulation function to ensure the input in each layer of the model followed a normal distribution with a mean of 0 and a variance of 1. |
T385 |
9638-9728 |
Sentence |
denotes |
The bottom branch consisted of two convolution layers, two BN layers, and two ReLu layers. |
T386 |
9729-9937 |
Sentence |
denotes |
The first convolution layer in the bottom branch consisted of multiple 3 × 3 convolution kernels with a stride of 2 and a padding of 1 to reduce the size of the feature maps when local features were obtained. |
T387 |
9938-10074 |
Sentence |
denotes |
The second convolution layer in the bottom branch consisted of multiple 3 × 3 convolution kernels with a stride of 1 and a padding of 1. |
T388 |
10075-10194 |
Sentence |
denotes |
The ReLu function was used as the activation function to ensure a non-linear relationship between the different layers. |
T389 |
10195-10329 |
Sentence |
denotes |
The output of the upper branch and the output of the bottom branch after the second BN were fused using an element-wise add operation. |
T390 |
10330-10416 |
Sentence |
denotes |
The fused result was output 1, and the fused result after the ReLu layer was output 2. |
T391 |
10417-10465 |
Sentence |
denotes |
Fig. 6 The four units of the proposed framework. |
T392 |
10466-11146 |
Sentence |
denotes |
a ResBlock-A architecture, containing two convolution layers with 3 × 3 kernels, one convolution layer with a 1 × 1 kernel, three batch normalization layers, two ReLu layers, and one max-pooling layer with a 3 × 3 kernel. b ResBlock-B architecture; the basic unit is the same as the ResBlock-A, except for output 1. c The Control Gate Block has a synaptic-based frontend architecture that controls the direction of the feature map flow and the overall optimization direction of the framework. d The Regressor architecture is a skip-connection architecture containing one convolution layer with 3 × 3 kernels, one batch normalization layer, one ReLu layer, and three linear layers. |
T393 |
11147-11158 |
Sentence |
denotes |
ResBlock-B: |
T394 |
11159-11295 |
Sentence |
denotes |
The ResBlock-B (Fig. 6b) was a multiple-input single-output block that was similar to the ResBlock-A, except that there was no output 1. |
T395 |
11296-11446 |
Sentence |
denotes |
The value of the stride and padding in each layer of the ResBlock-A and ResBlock-B could be adjusted using hyper-parameters based on the requirements. |
T396 |
11447-11466 |
Sentence |
denotes |
Control Gate Block: |
T397 |
11467-11720 |
Sentence |
denotes |
As shown in Fig. 6c, the Control Gate Block was a multiple-input single-output block consisting of a predictor module, a counter module, and a synapses module to control the optimization direction while controlling the information flow in the framework. |
T398 |
11721-11845 |
Sentence |
denotes |
The pipeline of the predictor module is shown in Supplementary Fig. 19a, where the Input S1 is the output of the ResBlock-B. |
T399 |
11846-11947 |
Sentence |
denotes |
The Input S1 was then flattened to a one-dimensional feature vector as the input of the linear layer. |
T400 |
11948-12054 |
Sentence |
denotes |
The output of the linear layer was converted to a probability of each category using the softmax function. |
T401 |
12055-12203 |
Sentence |
denotes |
A sensitivity calculator used the Vpred and Vtrue as inputs to calculate the TP, TN, FP, and false-negative (FN) rates to calculate the sensitivity. |
T402 |
12204-12303 |
Sentence |
denotes |
The sensitivity calculation was followed by a step function to control the output of the predictor. |
T403 |
12304-12450 |
Sentence |
denotes |
The ths was a threshold value; if the calculated sensitivity was greater or equal to ths, the step function output 1; otherwise, the output was 0. |
T404 |
12451-12532 |
Sentence |
denotes |
The counter module was a conditional counter, as shown in Supplementary Fig. 19b. |
T405 |
12533-12598 |
Sentence |
denotes |
If the input n was zero, the counter was cleared and set to zero. |
T406 |
12599-12637 |
Sentence |
denotes |
Otherwise, the counter increased by 1. |
T407 |
12638-12672 |
Sentence |
denotes |
The output of the counter was num. |
T408 |
12673-12822 |
Sentence |
denotes |
The synapses block mimicked the synaptic structure, and the input variable num was similar to a neurotransmitter, as shown in Supplementary Fig. 19c. |
T409 |
12823-12882 |
Sentence |
denotes |
The input num was the input parameter of the step function. |
T410 |
12883-13011 |
Sentence |
denotes |
The ths was a threshold value; if the input num was greater or equal to ths, the step function output 1; otherwise, it output 0. |
T411 |
13012-13115 |
Sentence |
denotes |
An element-wise multiplication was performed between the input S1 and the output of the synapses block. |
T412 |
13116-13171 |
Sentence |
denotes |
The multiplied result was passed on to a discriminator. |
T413 |
13172-13272 |
Sentence |
denotes |
If the sum of each element in the result was not zero, the Input S1 was passed on to the next layer. |
T414 |
13273-13327 |
Sentence |
denotes |
Otherwise, the input S1 information was not passed on. |
T415 |
13328-13344 |
Sentence |
denotes |
Regressor block: |
T416 |
13345-13473 |
Sentence |
denotes |
The regressor block consisted of multiple linear layers, a convolution layer, a BN layer, and a ReLu layer, as shown in Fig. 6d. |
T417 |
13474-13616 |
Sentence |
denotes |
A skip-connection architecture was adopted to retain the features and increase the ability of the block to represent non-linear relationships. |
T418 |
13617-13747 |
Sentence |
denotes |
The convolution block in the skip-connection structure was a convolution layer with multiple numbers of 1 × 1 convolution kernels. |
T419 |
13748-13903 |
Sentence |
denotes |
The number of the convolution kernels was the same as that of the output size of the second linear layer to ensure the consistency of the vector dimension. |
T420 |
13904-14005 |
Sentence |
denotes |
The input size and output size of each linear layer were adjustable to be applicable to actual cases. |
T421 |
14006-14148 |
Sentence |
denotes |
Based on the four blocks, two frameworks were designed for the classification task and regression task, respectively.Classification framework: |
T422 |
14149-14214 |
Sentence |
denotes |
The CNNCF consisted of stage I and stage II, as shown in Fig. 3a. |
T423 |
14215-14286 |
Sentence |
denotes |
Stage I was duplicated Q times in the framework (in this study, Q = 1). |
T424 |
14287-14409 |
Sentence |
denotes |
It consisted of multiple ResBlock-A with a number of M (in this study, M = 2), one ResBlock-B, and one Control Gate Block. |
T425 |
14410-14513 |
Sentence |
denotes |
Stage II consisted of multiple ResBlock-A with a number of N (in this study, N = 2) and one ResBlock-B. |
T426 |
14514-14660 |
Sentence |
denotes |
The weighted cross-entropy loss function was used and was minimized using the SGD optimizer with a learning rate of a1 (in this study, a1 = 0.01). |
T427 |
14661-14911 |
Sentence |
denotes |
A warm-up strategy58 was used in the initialization of the learning rate for a smooth training start, and a reduction factor of b1 (in this study, b1 = 0.1) was used to reduce the learning rate after every c1 (in this study, c1 = 10) training epochs. |
T428 |
14912-15050 |
Sentence |
denotes |
The model was trained for d1 (in this study, d1 = 40) epochs, and the model parameters saved in the last epoch was used in the test phase. |
T429 |
15051-15072 |
Sentence |
denotes |
Regression framework: |
T430 |
15073-15145 |
Sentence |
denotes |
The CNNRF (Fig. 3b) consisted of two parts (stage II and the regressor). |
T431 |
15146-15390 |
Sentence |
denotes |
The inputs to the regression framework were the images of the lesion areas, and the output was the corresponding vector with five dimensions, representing the five clinical indicators (all clinical indicators were normalized to a range of 0–1). |
T432 |
15391-15495 |
Sentence |
denotes |
The stage II structure was the same as that in the classification framework, except for some parameters. |
T433 |
15496-15639 |
Sentence |
denotes |
The loss function was the MSE loss function, which was minimized using the SGD optimizer with a learning rate of a2 (in this study, a2 = 0.01). |
T434 |
15640-15888 |
Sentence |
denotes |
A warm-up strategy was used in the initialization of the learning rate for a smooth training start, and a reduction factor of b2 (in this study, b2 = 0.1) was used to reduce the learning rate after every c2 (in this study, c2 = 50) training epochs. |
T435 |
15889-16033 |
Sentence |
denotes |
The framework was trained for d2 (in this study, d2 = 200) epochs, and the model parameters saved in the last epoch were used in the test phase. |
T436 |
16034-16079 |
Sentence |
denotes |
The workflow of the classification framework. |
T437 |
16080-16153 |
Sentence |
denotes |
The workflow of the classification framework was demonstrated in Fig. 3c. |
T438 |
16154-16282 |
Sentence |
denotes |
The preprocessed images are sent to the first convolution block to expand the channels and processed as the input for the CNNCF. |
T439 |
16283-16425 |
Sentence |
denotes |
Given the input Fi with a size of M × N × 64, the stage I output feature maps F′i with a size of M/8 × N/8 × 256 in the default configuration. |
T440 |
16426-16565 |
Sentence |
denotes |
As we introduced above, the Control Gate Block controls the optimization direction while controlling the information flow in the framework. |
T441 |
16566-16648 |
Sentence |
denotes |
If the Control Gate Block is open, the feature maps F′i are passed on to stage II. |
T442 |
16649-16954 |
Sentence |
denotes |
Given the input F′i, the stage II output the feature maps F″i with a size of M/64 × N/64 × 512 which is defined as follows:1 Fi′=S1(Fi)Fi″=S2(Fi′)⊗CGB(Fi′),where S1 denotes the stage I block, S2 denotes the stage II block, and CGB is the Control Gate Block. ⊗ is the element-wise multiplication operation. |
T443 |
16955-17111 |
Sentence |
denotes |
Stage II is Followed by a global average pooling layer (GAP) and a fully connect layer (FC layer) with a softmax function to generate the final predictions. |
T444 |
17112-17202 |
Sentence |
denotes |
Given F″i as input, the GAP is adopted to generate a vector Vf with a size of 1 × 1 × 512. |
T445 |
17203-17570 |
Sentence |
denotes |
Given Vf as input, the FC layer with the softmax function outputs a vector Vc with a size of 1 × 1 × C.2 Vf=GAPFi′Vc=SMaxFCVf,where GAP is the global average pooling layer, the FC is the fully connect layer, SMax is the softmax function, Vf is the feature vector generated by the GAP, Vc is the prediction vector, and C is the number of case types used in this study. |
T446 |
17572-17649 |
Sentence |
denotes |
Training strategies and evaluation indicators of the classification framework |
T447 |
17650-17743 |
Sentence |
denotes |
The training strategies and hyper-parameters of the classification framework were as follows. |
T448 |
17744-17922 |
Sentence |
denotes |
We adopted a knowledge distillation method (Fig. 7) to train the CNNCF as a student network with one stage I block and one stage II block, each of which contained two ResBlock-A. |
T449 |
17923-18127 |
Sentence |
denotes |
Four teacher networks (the hyper-parameters are provided in Supplementary Table 21) with the proposed blocks were trained on the train-val part of each sub-data set using a 5-fold cross-validation method. |
T450 |
18128-18197 |
Sentence |
denotes |
All networks were initialized using the Xavier initialization method. |
T451 |
18198-18276 |
Sentence |
denotes |
The initial learning rate was 0.01, and the optimization function was the SGD. |
T452 |
18277-18387 |
Sentence |
denotes |
The CNNCF was trained using the image data and the label, as well as the fused output of the teacher networks. |
T453 |
18388-18510 |
Sentence |
denotes |
The comparison of RT-PCR test results using throat specimen and the CNNCF results were provided in Supplementary Table 22. |
T454 |
18511-18588 |
Sentence |
denotes |
Supplementary Fig. 20 shows the details of the knowledge distillation method. |
T455 |
18589-18705 |
Sentence |
denotes |
The definitions and details of the five evaluation indicators used in this study were given in Supplementary Note 2. |
T456 |
18706-18805 |
Sentence |
denotes |
Fig. 7 Knowledge distillation consisting of multiple teacher networks and a target student network. |
T457 |
18806-18906 |
Sentence |
denotes |
The knowledge is transferred from the teacher networks to the student network using a loss function. |
T458 |
18908-18947 |
Sentence |
denotes |
Gradient-weighted class activation maps |
T459 |
18948-19091 |
Sentence |
denotes |
Grad-CAM59 in the Pytorch framework was used to visualize the salient features that contributed the most to the prediction output of the model. |
T460 |
19092-19338 |
Sentence |
denotes |
Given a target category, the Grad-CAM performed back-propagation to obtain the final CNN feature maps and the gradient of the feature maps; only pixels with positive contributions to the specified category were retained through the ReLU function. |
T461 |
19339-19538 |
Sentence |
denotes |
The Grad-CAM method was used for all test data set (X-data and CT-data) in the CNNCF without changing the framework structure to obtain a visual output of the framework’s high discriminatory ability. |
T462 |
19540-19570 |
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denotes |
Statistics and reproducibility |
T463 |
19571-19689 |
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denotes |
We used multiple statistical indices and empirical distributions to assess the performance of the proposed frameworks. |
T464 |
19690-19849 |
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denotes |
The equations of the statistical indices are shown in Supplementary Fig. 21 and all the abbreviations used in this study are defined in Supplementary Table 23. |
T465 |
19850-19978 |
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denotes |
All the data used in this study followed the criteria: (1) sign informed consent prior to enrollment. (2) At least 18 years old. |
T466 |
19979-20110 |
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denotes |
This study was conducted following the declaration of Helsinki and was approved by the Capital Medical University Ethics Committee. |
T467 |
20111-20312 |
Sentence |
denotes |
The following statistical analyses of the data were conducted for both evaluating the classification framework and the regression framework.Statistical indices to evaluate the classification framework. |
T468 |
20313-20540 |
Sentence |
denotes |
Multiple evaluation indicators (PRC, ROC, AUPRC, AUROC, sensitivity, specificity, precision, kappa index, and F1 with a fixed threshold) were computed for a comprehensive and accurate assessment of the classification framework. |
T469 |
20541-20657 |
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denotes |
Multiple threshold values were in the range from 0 to 1 with a step value of 0.005 to obtain the ROC and PRC curves. |
T470 |
20658-20824 |
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denotes |
The PRC showed the relationship between the precision and the sensitivity (or recall), and the ROC indicated the relationship between the sensitivity and specificity. |
T471 |
20825-20912 |
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denotes |
The two curves reflected the comprehensive performance of the classification framework. |
T472 |
20913-21017 |
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denotes |
The kappa index is a statistical method for assessing the degree of agreement between different methods. |
T473 |
21018-21097 |
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denotes |
In our use case, the indicator was used to measure the stability of the method. |
T474 |
21098-21190 |
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denotes |
The F1 score is a harmonic average of precision and sensitivity and considers the FP and FN. |
T475 |
21191-21283 |
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denotes |
The bootstrapping method was used to calculate the empirical distribution of each indicator. |
T476 |
21284-21477 |
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denotes |
The detailed calculation process was as follows: we conducted random sampling with replacement to generate 1000 new test data sets with the same number of samples as the original test data set. |
T477 |
21478-21551 |
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denotes |
The evaluation indicators were calculated to determine the distributions. |
T478 |
21552-21625 |
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denotes |
The results were displayed in boxplots (Fig. 5 and Supplementary Fig. 2). |
T479 |
21626-21683 |
Sentence |
denotes |
Statistical indices to evaluate the regression framework. |
T480 |
21684-21831 |
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denotes |
Multiple evaluation indicators (MSE, RMSE, MAE, R2, and PCC) were computed for a comprehensive and accurate assessment of the regression framework. |
T481 |
21832-21914 |
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denotes |
The MSE was used to calculate the deviation between the predicted and true values. |
T482 |
21915-21962 |
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denotes |
The RMSE was the square root of the MSE result. |
T483 |
21963-22024 |
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denotes |
The two indicators show the accuracy of the model prediction. |
T484 |
22025-22099 |
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denotes |
The R2 was used to assess the goodness-of-fit of the regression framework. |
T485 |
22100-22191 |
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denotes |
The r was used to assess the correlation between two variables in the regression framework. |
T486 |
22192-22286 |
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denotes |
The indicators were calculated using the open-source tools scikit-learn and the scipy library. |