Architectural distortion (AD) is one of the most important potentially ominous signs of breast cancer. As a 3D imaging, digital breast tomosynthesis (DBT) is an accurate tool to detect AD. We developed a deep learning approach for AD detection guided by mammary gland spatial pattern (MGSP) in DBT. The approach consists of two stages: 2D detection and 3D aggregation. In 2D detection, prior MGSP information is obtained first. It includes 1) magnitude image and orientation field map produced from Gabor filters and 2) mammary gland convergence map. Second, Faster-RCNN detection network is employed. Region proposal network extracts features and determines locations of AD candidates and the soft classifier is used for reducing false positives. In 3D aggregation, a region fusion strategy is designed to fuse 2D candidates into 3D candidates. For evaluation, 265 DBT volumes (138 with ADs and 127 without any lesion) were collected from 68 patients. Free response receiver operating characteristic curve was obtained and the mean true positive fraction (MTPF) was used as the figure-of-merit of model performance. Compared with a baseline model based on convergence measure, the six-fold cross validation results showed that our proposed approach achieved MTPF of 0.50 ± 0.04, while the baseline achieved 0.37 ± 0.03. The improvement of our approach was statistically significant (p≪0.001).
Breast tumor segmentation is an essential step in a computer aided diagnosis (CAD) system. Due to the speckle noise, various size and locations of lesions, it is a challenging task to segment the tumors on breast ultrasound (BUS) image accurately. In this paper, we propose a region growing method which applies the similarity score and homogeneity based on the neutrosophic set (NS) domain to segment and detect tumors. At first, the original BUS image is transferred to the NS domain and calculate the different NS elements to obtain the NS image. Then, a thresholding method and morphology method are used to locate seed regions, and after that each seed region grows separately. The direction of region growing depends on the homogeneity vector, similarity set score vector and distance vector between the candidate points and seed regions. The suspensive condition also lies on the homogeneity vector and similarity set score vector between the seed region and the NS image. Finally, a pretrained deep learning network and transfer learning scheme are used for false positive reduction. Experiment on various clinic BUS images has suggested that the proposed method is able to segment the BUS image and extract tumor accurately.
Breast cancer is presently one of the most common cancer among women and has high morbidity and mortality worldwide. The emergence of microcalcifications (MCs) is an important early sign of breast cancer. In this study, a computer-aided detection and diagnosis (CAD) system is developed to automatically detect MC clusters (MCCs) and further providing cancer likelihood prediction. Firstly, each individual MC is detected using our previously designed MC detection system, which includes preprocessing, MC enhancement, MC candidate detection, false positive (FP) reduction of MCs and regional clustering procedures. Secondly, a deep convolution neural network (DCNN) is trained on 394 clinical high-resolution full field digital mammograms (FFDMs) containing biopsy-proven MCCs to discriminate MCC lesions. For cluster-based detection evaluation, a 90% sensitivity is obtained with a FP rate of 0.2 FPs per image. The classification performance of the whole system is validated on 70 cases and tested on 71 cases, and for case-based diagnosis evaluation, the area under the receiver operating characteristic curve (AUC) on validation and testing sets are 0.945 and 0.932, respectively. Different from previous literatures committing to finding and selecting effective features, the proposed method replaces manual feature extraction step by using deep convolution neural network. The obtained results demonstrate that the proposed method is effective in the automatically detection and classification of MCCs.
Three-dimensional reconstruction of nerve fascicle is important in the analysis of biological characteristics in the arm. The topology of fascicle has been used by doctors to investigate the nerve direction and the relationship between the individual nerve fascicle. However, there still does not exist an ideal internal fascicle and 3D model in the human peripheral nerve. Accurate segmentation of fascicle from CT images is a crucial step to obtain reliable 3D nerve fascicle model. Traditional method in the fascicle segmentation is not efficient due to time consuming, manual work and poor generalization capacity. In this study, we proposed an efficient deep segmentation network and then reconstruct 3D nerve fascicle model. The proposed network explores the intra-slice contextual features with convolutional long short-term memory for accurate fascicle segmentation, and model long-range semantic information among image slices. Transfer learning technique is integrated with ResNet34, and the discriminative capability of intermediate features are further improved. The proposed network architecture is efficient, flexible and suitable for separating the adhesive fascicle. Our approach is the first deep learning method for nerves segmentation. The proposed approach achieves state-of-the-art performance on our dataset, where the mean Dice of our method is 95.4% and at least 5% more than other methods.
Previous studies found that multiple view techniques improved the accuracy of lesion detection on mammograms. One of the key components in multiple view techniques was the detection of nipple location, which is the only reliable landmark on mammograms. In this study, our purpose was to develop a novel nipple detection scheme by using geometric and radiomic information extracted on digital mammography (DM). We first extracted a region of interest (ROI) to limit the region of nipple detection by using breast area and the chest wall orientation. The geometric information along the breast boundary was used to categorize the nipples into obvious and subtle types. A top hat transform was used to identify the location of obvious nipples. For subtle type, the radiomic feature matrix was calculated on straightened ROIs along the normal direction of breast boundary. A random forest classifier was trained to combine the radiomic features and to predict the location of subtle nipples. Seven hundred and twenty one DMs were collected for evaluation of our algorithm. A radiologist manually identified the location of nipples as the reference standard. It was found that the average Euclidean distances between the computer and the reference standard were 0.93±5.0 mm for obvious nipples, and 2.74±5.0 mm for subtle nipples, respectively. Future work is underway to evaluate the automated nipples on the registration of abnormalities on multiple view mammograms.
KEYWORDS: Neural networks, Breast cancer, Signal detection, Mammography, Computer aided diagnosis and therapy, Detection and tracking algorithms, Breast, Image processing
Breast cancer is one of the most common cancers and has high morbidity and mortality worldwide, posing a serious threat to the health of human beings. The emergence of microcalcifications (MCs) is an important signal of early breast cancer. However, it is still challenging and time consuming for radiologists to identify some tiny and subtle individual MCs in mammograms. This study proposed a novel computer-aided MC detection algorithm on the full field digital mammograms (FFDMs) using deep convolution neural network (DCNN). Firstly, a MC candidate detection system was used to obtain potential MC candidates. Then a DCNN was trained using a novel adaptive learning strategy, neutrosophic reinforcement sample learning (NRSL) strategy to speed up the learning process. The trained DCNN served to recognize true MCs. After been classified by DCNN, a density-based regional clustering method was imposed to form MC clusters. The accuracy of the DCNN with our proposed NRSL strategy converges faster and goes higher than the traditional DCNN at same epochs, and the obtained an accuracy of 99.87% on training set, 95.12% on validation set, and 93.68% on testing set at epoch 40. For cluster-based MC cluster detection evaluation, a sensitivity of 90% was achieved at 0.13 false positives (FPs) per image. The obtained results demonstrate that the designed DCNN plays a significant role in the MC detection after being prior trained.
A 3D multiscale intensity homogeneity transformation (MIHT) method was developed to reduce false positives (FPs) in our previously developed CAD system for pulmonary embolism (PE) detection. In MIHT, the voxel intensity of a PE candidate region was transformed to an intensity homogeneity value (IHV) with respect to the local median intensity. The IHVs were calculated in multiscales (MIHVs) to measure the intensity homogeneity, taking into account vessels of different sizes and different degrees of occlusion. Seven new features including the entropy, gradient, and moments that characterized the intensity distributions of the candidate regions were derived from the MIHVs and combined with the previously designed features that described the shape and intensity of PE candidates for the training of a linear classifier to reduce the FPs. 59 CTPA PE cases were collected from our patient files (UM set) with IRB approval and 69 cases from the PIOPED II data set with access permission. 595 and 800 PEs were identified as reference standard by experienced thoracic radiologists in the UM and PIOPED set, respectively. FROC analysis was used for performance evaluation. Compared with our previous CAD system, at a test sensitivity of 80%, the new method reduced the FP rate from 18.9 to 14.1/scan for the PIOPED set when the classifier was trained with the UM set and from 22.6 to 16.0/scan vice versa. The improvement was statistically significant (p<0.05) by JAFROC analysis. This study demonstrated that the MIHT method is effective in reducing FPs and improving the performance of the CAD system.
The curved planar reformation (CPR) method re-samples the vascular structures along the vessel centerline to generate
longitudinal cross-section views. The CPR technique has been commonly used in coronary CTA workstation to facilitate
radiologists’ visual assessment of coronary diseases, but has not yet been used for pulmonary vessel analysis in CTPA
due to the complicated tree structures and the vast network of pulmonary vasculature. In this study, a new curved planar
reformation and optimal path tracing (CROP) method was developed to facilitate feature extraction and false positive
(FP) reduction and improve our PE detection system. PE candidates are first identified in the segmented pulmonary
vessels at prescreening. Based on Dijkstra’s algorithm, the optimal path (OP) is traced from the pulmonary trunk
bifurcation point to each PE candidate. The traced vessel is then straightened and a reformatted volume is generated
using CPR. Eleven new features that characterize the intensity, gradient, and topology are extracted from the PE
candidate in the CPR volume and combined with the previously developed 9 features to form a new feature space for FP
classification. With IRB approval, CTPA of 59 PE cases were retrospectively collected from our patient files (UM set)
and 69 PE cases from the PIOPED II data set with access permission. 595 and 800 PEs were manually marked by
experienced radiologists as reference standard for the UM and PIOPED set, respectively. At a test sensitivity of 80%, the
average FP rate was improved from 18.9 to 11.9 FPs/case with the new method for the PIOPED set when the UM set
was used for training. The FP rate was improved from 22.6 to 14.2 FPs/case for the UM set when the PIOPED set was
used for training. The improvement in the free response receiver operating characteristic (FROC) curves was statistically
significant (p<0.05) by JAFROC analysis, indicating that the new features extracted from the CROP method are useful
for FP reduction.
We improved an image segmentation algorithm based on neutrosophic set (NS) and extended the modified method into color image segmentation. The original NS image segmentation approach transformed the images into NS domain, which is described using three membership sets: T, I, and F. Then two operations, α-mean and β-enhancement operations were employed to reduce the set indeterminacy. Although this method was quite successful in image segmentation application, some drawbacks still exist, such as oversegmentation and fixed α and β parameters. Thus, a new algorithm is proposed to overcome these limitations of the NS-based image segmentation algorithm. Then, the new modified method is extended into color image segmentation. The NS-based image segmentation algorithm is applied to each color channel independently. Then each channel is moved to a matrix column, respectively, to construct the input matrix to the γ-K-means clustering. Experiments are conducted on a variety of images, and our results are compared with those new existing segmentation algorithm. The experimental results demonstrate that the proposed approach can segment the color images automatically and effectively.
Image noise removal is the first step in image processing, pattern recognition, and computer vision. A novel algorithm is proposed to remove noise on images based on anisotropic diffusion and subpixel approaches. Firstly, the subpixel difference of an image is defined and the Euler-Lagrange equation is solved. Then, the diffusion equation is solved numerically using an iterative approach. Finally, the noise is removed after the diffusion procedure is finished. The experiments show that the proposed algorithm yields better signal-to-noise ratio and has no blocky effect and less generated speckle noise in the results than the other methods do. In addition, it is easy to implement, takes less iterations, and has low computational complexity.
We are developing a computer-aided detection (CAD) system to assist radiologists in pulmonary embolism (PE)
detection in computed tomographic pulmonary angiography (CTPA). Automatic segmentation and tracking of
pulmonary vessels is a fundamental step to define the search space for PE detection. For automated tracking of
pulmonary arteries, it is important to accurately identify the seed points to track the left and right pulmonary vessel
trees. In this study, we developed an automatic seed point identification and pulmonary main artery (PMA)
segmentation method. The seed point was derived from the bifurcation region where the pulmonary trunk artery
splits into the left and right. A 3D recursive optimal path finding method (RPF) was developed to find the paths from
the bifurcation point to the end of the left and right PMAs. The PMAs were finally extracted along the PMA paths
using morphological operation.
Two and 18 CTPA cases was used for training and testing, respectively. A set of points in the central luminal space
of the PMA were manually marked as the "reference standard" by two experienced chest radiologists using a
computer interface. A total of 3870 were marked in the test set. A voxel located on the computer-identified paths of
the PMA was counted as a true PMA voxel when its distance to the closest reference standard point is within a
threshold. Our results show that 95.6% (17681/18502) and 88.8% (16439/18502) of computer identified PMA path
points were within a distance of 10 mm and 8 mm to the closest reference point, respectively, and 100% (18/18) of
the seed points were detected in the bifurcation region. 2.7% (104/3870) of the reference standard points were not
contained in the computer segmented vessels and counted as false negative points.
Vessel segmentation is a fundamental step in an automated pulmonary embolism (PE) detection system. The purpose of
this study is to improve the segmentation scheme for pulmonary vessels affected by PE and other lung diseases. We have
developed a multiscale hierarchical vessel enhancement and segmentation (MHES) method for pulmonary vessel tree
extraction based on the analysis of eigenvalues of Hessian matrices. However, it is difficult to segment the pulmonary
vessels accurately under suboptimal conditions, such as vessels occluded by PEs, surrounded by lymphoid tissues or
lung diseases, and crossing with other vessels. In this study, we developed a new vessel refinement method utilizing
curved planar reformation (CPR) technique combined with optimal path finding method (MHES-CROP). The MHES
segmented vessels straightened in the CPR volume was refined using adaptive gray level thresholding where the local
threshold was obtained from least-square estimation of a spline curve fitted to the gray levels of the vessel along the
straightened volume. An optimal path finding method based on Dijkstra's algorithm was finally used to trace the correct
path for the vessel of interest. Two and eight CTPA scans were randomly selected as training and test data sets,
respectively. Forty volumes of interest (VOIs) containing "representative" vessels were manually segmented by a
radiologist experienced in CTPA interpretation and used as reference standard. The results show that, for the 32 test
VOIs, the average percentage volume error relative to the reference standard was improved from 32.9±10.2% using the
MHES method to 9.9±7.9% using the MHES-CROP method. The accuracy of vessel segmentation was improved
significantly (p<0.05). The intraclass correlation coefficient (ICC) of the segmented vessel volume between the
automated segmentation and the reference standard was improved from 0.919 to 0.988. Quantitative comparison of the
MHES method and the MHES-CROP method with the reference standard was also evaluated by the Bland-Altman plot.
This preliminary study indicates that the MHES-CROP method has the potential to improve PE detection.
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