Jan-Jurre Mordang

Computer-aided detection of breast cancers using Haar-like features in automated 3D breast ultrasound.

PURPOSE Automated 3D breast ultrasound (ABUS) has gained interest in breast imaging. Especially for screening women with dense breasts, ABUS appears to be beneficial. However, since the amount of data generated is large, the risk of oversight errors is substantial. Computer aided detection (CADe) may be used as a second reader to prevent oversight errors. When CADe is used in this fashion, it is essential that small cancers are detected, while the number of false positive findings should remain acceptable. In this work, the authors improve their previously developed CADe system in the initial candidate detection stage. METHODS The authors use a large number of 2D Haar-like features to differentiate lesion structures from false positives. Using a cascade of GentleBoost classifiers that combines these features, a likelihood score, highly specific for small cancers, can be efficiently computed. The likelihood scores are added to the previously developed voxel features to improve detection. RESULTS The method was tested in a dataset of 414 ABUS volumes with 211 cancers. Cancers had a mean size of 14.72 mm. Free-response receiver operating characteristic analysis was performed to evaluate the performance of the algorithm with and without using the aforementioned Haar-like feature likelihood scores. After the initial detection stage, the number of missed cancer was reduced by 18.8% after adding Haar-like feature likelihood scores. CONCLUSIONS The proposed technique significantly improves our previously developed CADe system in the initial candidate detection stage.

A Comparison Between a Deep Convolutional Neural Network and Radiologists for Classifying Regions of Interest in Mammography

In this paper, we employ a deep Convolutional Neural Network CNN for the classification of regions of interest of malignant soft tissue lesions in mammography and show that it performs on par to experienced radiologists. The CNN was applied to 398 regions of 5

The Effect of Mammogram Preprocessing on Microcalcification Detection with Convolutional Neural Networks

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LUT-QNE: Look-Up-Table Quantum Noise Equalization in Digital Mammograms

5i?źcm, half of which contained a malignant lesion and the other half depicted suspicious regions in normal mammograms detected by a traditional CAD system. Four radiologists participated in the study. ROC analysis was used for evaluating results. The AUC of CNN was 0.87, which was higher than the mean AUC of the radiologists 0.84, though the difference was not significant.

Vessel segmentation in screening mammograms

Convolutional neural networks CNNs have shown to be powerful for classification of image data and are increasingly used in medical image analysis. Therefore, CNNs might be very suitable to detect microcalcifications in mammograms. In this study, we have configured a deep learning approach to fulfill this task. To overcome the large class imbalance between pixels belonging to microcalcifications and other breast tissue, we applied a hard negative mining strategy where two CNNs are used. The deep learning approach was compared to a current state-of-the-art method for the detection of microcalcifications: the cascade classifier. Both methods were trained on a large training set including 11,711 positive and 27 million negative samples. For testing, an independent test set was configured containing 5,298 positive and 18 million negative samples. The mammograms included in this study were acquired on mammography systems from three manufactures: Hologic, GE, and Siemens. Receiver operating characteristics analysis was carried out. Over the whole specificity range, the CNN approach yielded a higher sensitivity compared to the cascade classifier. Significantly higher mean sensitivities were obtained with the CNN on the mammograms of each individual manufacturer compared to the cascade classifier in the specificity range of 0 to 0.1. To our knowledge, this was the first study to use a deep learning strategy for the detection of microcalcifications in mammograms.

Improving the automated detection of calcifications by combining deep cascades and deep convolutional nets.

Microcalcifications are an early mammographic indicator of breast cancer. To assist screening radiologists in reading mammograms, machine learning techniques have been developed for the automated detection of microcalcifications. In the last few years, Convolutional Neural Networks (CNNs) have achieved state-of-the-art performance in many computer vision and medical image analysis applications. A key step in CNN-based detection is image preprocessing, including brightness and contrast variations. In this work, we investigate the influence of preprocessing of digital mammograms on the microcalcification detection performance of two CNNs inspired by the popular AlexNet and VGGnet. We tested two preprocessing methods commonly applied to unprocessed raw digital mammograms: (i) the logarithmic transformation adopted by different manufacturers for the presentation of the image to the radiologists; and (ii) the square-root of image intensity that stabilizes the intensity-dependent noise present in the mammogram. Experiments were performed on 1,066 mammograms acquired with GE Senographe systems. Both preprocessing methods yielded statistically significantly better microcalcification detection performance. Results of the square-root transform were superior to those obtained with the log transform.

Mammogram denoising to improve the calcification detection performance of convolutional nets.

Purpose Computer‐aided detection (CADe) systems for mammography screening still mark many false positives. This can cause radiologists to lose confidence in CADe, especially when many false positives are obviously not suspicious to them. In this study, we focus on obvious false positives generated by microcalcification detection algorithms. Methods We aim at reducing the number of obvious false‐positive findings by adding an additional step in the detection method. In this step, a multiclass machine learning method is implemented in which dedicated classifiers learn to recognize the patterns of obvious false‐positive subtypes that occur most frequently. The method is compared to a conventional two‐class approach, where all false‐positive subtypes are grouped together in one class, and to the baseline CADe system without the new false‐positive removal step. The methods are evaluated on an independent dataset containing 1,542 screening examinations of which 80 examinations contain malignant microcalcifications. Results Analysis showed that the multiclass approach yielded a significantly higher sensitivity compared to the other two methods (P < 0.0002). At one obvious false positive per 100 images, the baseline CADe system detected 61% of the malignant examinations, while the systems with the two‐class and multiclass false‐positive reduction step detected 73% and 83%, respectively. Conclusions Our study showed that by adding the proposed method to a CADe system, the number of obvious false positives can decrease significantly (P < 0.0002).

Can radiologists improve their breast cancer detection in mammography when using a deep learning based computer system as decision support

Quantum noise is a signal-dependent, Poisson-distributed noise and the dominant noise source in digital mammography. Quantum noise removal or equalization has been shown to be an important step in the automatic detection of microcalcifications. However, it is often limited by the difficulty of robustly estimating the noise parameters on the images. In this study, a nonparametric image intensity transformation method that equalizes quantum noise in digital mammograms is described. A simple Look-Up-Table for Quantum Noise Equalization LUT-QNE is determined based on the assumption that noise properties do not vary significantly across the images. This method was evaluated on a dataset of 252 raw digital mammograms by comparing noise statistics before and after applying LUT-QNE. Performance was also tested as a preprocessing step in two microcalcification detection schemes. Results show that the proposed method statistically significantly improves microcalcification detection performance.