Index

Convolutional LSTM for Multi-organ Segmentation on CT and MR Images in Abdominal Region

Automatic Pathological Speech Intelligibility Assessment Using Speech Disentanglement Without Bottleneck Information

Optimizing the Preprocessing Pipeline for “virtual Dynamic Contrast Enhancement” in Breast MRI

Semi-supervised learning for multi-modal bone segmentation

Since AlexNet won the ImageNet Challenge by a wide margin in 2012, the popularity of deep learning has been steadily increasing. In the last years, a technique that has been especially popular is semantic segmentation, as it is used in self-driving cars and medical image analysis. A big challenge that arises when training neural networks (NN) for this task is the acquisition of adequate segmentation masks, because the labeling has often times to be performed by industry experts and is very time consuming. Resulting from that, solutions circumventing this problem had to be found. A popular solution for this task is semi-supervised learning, where only a certain amount of the data is annotated. This approach has the obvious advantage of reducing the time needed for the data acquisition process, but NNs trained this way still have a worse performance compared to ones that were trained fully-supervised.

A common disease affecting one in three women and one in twelve men is osteoporosis. It’s symptoms include low bone mass and a deterioration of bone tissue, leading to an increased fracture risk. The malady affects especially elderly people and for their protection, providing diagnostic tools and suitable treatments is important [1]. Structures that can be found in the bone include lacunae containing osteocytes and trans-cortical vessels (TCV). Murine and human tibia consists of two parts; the inner trabecular bone and the outer cortical bone, where TVCs can be found. To study them and their importance for the development of osteoporosis, we are trying to automatically segment the cortical bone from the surrounding tissue. Additionally, we will attempt to build a NN for the detection of TVCs and lacunae.

We want to achieve this using a model based on convolutional neural networks (CNN) for semantic segmentation. Similar tasks have already been performed [2], but our approach differs as we try to use as few labels as possible for the training process. Methods we want to incorporate are pre-training and the use of image transformations to make the most out of a limited amount of segmentation masks. If those approaches do not yield the desired results, we will also try to incorporate techniques of weakly- and self-supervised learning.

In detail, the thesis will consist of the following parts:

• implementation of multiple CNN-based architectures [3][4] to find a suitable model for our task,

• optimization of this model using different approaches,

• evaluation of the usefulness of pre-training and different semi-supervised learning techniques,

• integration of different techniques to increase the accuracy

References
[1] S P Tuck and R M Francis. Osteoporosis. Postgraduate Medical Journal, 78(923):526–532, 2002.
[2] Oliver Aust, Mareike Thies, DanielaWeidner, FabianWagner, Sabrina Pechmann, Leonid Mill, Darja Andreev, Ippei Miyagawa, Gerhard Kronke, Silke Christiansen, Stefan Uderhardt, Andreas Maier, and Anika Gruneboom. Tibia cortical bone segmentation in micro-ct and x-ray microscopy data using a single neural network. In Klaus Maier-Hein, Thomas M. Deserno, Heinz Handels, Andreas Maier, Christoph Palm, and Thomas Tolxdorff, editors, Bildverarbeitung fur die Medizin 2022 , pages 333–338, Wiesbaden, 2022. Springer Fachmedien Wiesbaden.
[3] Olaf Ronneberger, Philipp Fischer, and Thomas Brox. U-net: Convolutional networks for biomedical image segmentation. CoRR, abs/1505.04597, 2015.
[4] Jonathan Long, Evan Shelhamer, and Trevor Darrell. Fully convolutional networks for semantic segmentation. CoRR, abs/1411.4038, 2014.
[5] Adam Paszke, Sam Gross, Francisco Massa, Adam Lerer, James Bradbury, Gregory Chanan, Trevor Killeen, Zeming Lin, Natalia Gimelshein, Luca Antiga, Alban Desmaison, Andreas Kopf, Edward Yang, Zachary DeVito, Martin Raison, Alykhan Tejani, Sasank Chilamkurthy, Benoit Steiner, Lu Fang, Junjie Bai, and Soumith Chintala. Pytorch: An imperative style, high-performance deep learning library. In H. Wallach, H. Larochelle, A. Beygelzimer, F. d’Alche-Buc, E. Fox, and R. Garnett, editors, ´ Advances in Neural Information Processing Systems 32, pages 8024–8035. Curran Associates, Inc., 2019

Evaluation of a Modified U-Net with Dropout and a Multi-Task Model for Glacier Calving Front Segmentation

With global temperatures rising, the tracking and prediction of glacier changes become more and more relevant. Part of these efforts is the development of Neural Network Algorithms to automatically detect calving fronts of marine-terminating glaciers. Gourmelon et al. [1] introduce the first publicly available benchmark dataset for calving front delineation on synthetic aperture radar (SAR) imagery dubbed CaFFe. The dataset consists of the SAR imagery and two corresponding labels: one showing the calving front vs the background and the other showing different landscape regions. Moreover, the paper provides two deep learning models as baselines, one for each label. As there are many different approaches to calving front delineation the question of what method provides the best performance arises. Subsequently, the aim of this thesis is to evaluate the codes of the following two papers [2],[3] on the CaFFe benchmark dataset and compare their performance with the baselines provided by Gourmelon et al. [1].

paper 1:

Mohajerani et al. [2] employs a Convolutional Neural Network (CNN) with a modified U-Net architecture that also incorporates additional dropout layers. The CNN uses, in contrast to Gourmelon et al. [1], optical imagery as its input.

paper 2:

Heidler et al. [3] introduces a deep learning model for coastline detection, which combines the two tasks of segmenting water and land and binary coastline delineation into one cohesive multi-task deep learning model.

To make a fair and reasonable comparison, the hyperparameters of each model will be optimized on the CaFFe benchmark dataset and the model weights will be re-trained on CaFFe’s train set. The evaluation will be conducted on the provided test set and the metrics introduced in Gourmelon et al. [1] will be used for the comparison.

References

[1] Gourmelon, N.; Seehaus, T.; Braun, M.; Maier, A.; and Christlein, V.: Calving Fronts and Where to Find Them: A Benchmark Dataset and Methodology for Automatic Glacier Calving Front Extraction from SAR Imagery, Earth Syst. Sci. Data Discuss. [preprint]. 2022, https://doi.org/10.5194/essd-2022-139, in review.

[2] Mohajerani, Y.; Wood, M.; Velicogna, I.; and Rignot, E.: Detection of Glacier Calving Margins with Convolutional Neural Networks: A Case Study, Remote Sens. 2019, 11, 74. https://doi.org/10.3390/rs11010074

[3] Heidler, K.; Mou, L.; Baumhoer, C.; Dietz A.; and Zhu, X.: HED-UNet: Combined Segmentation and Edge Detection for Monitoring the Antarctic Coastline, IEEE Transactions on Geoscience and Remote Sensing. 2022, vol. 60, 1-14, Art no. 4300514, doi: 10.1109/TGRS.2021.3064606.

Animal-Independent Signal Enhancement Using Deep Learning

Examining and segmenting bioacoustic signals is an essential part of biology. For example, by analysing orca calls it is possible to draw several conclusions regarding the animals’ communication and social behavior.1 However, to avoid having to manually go through hours of audio material to detect those calls, the so-called ORCA-SPOT toolkit was developed, which uses Deep Learning to separate relevant signals from pure ambient sounds.2 These may nevertheless still contain background noise, which makes the examination rather difficult. To remove this background noise, ORCA-CLEAN was developed. Again, using a Deep Learning approach by adapting the Noise2Noise concept, as well as using machine-generated binary masks as an additional attention mechanism, the orca calls are denoised as best as possible without requiring clean data as foundation.3
But, as mentioned, this toolkit is optimized for the denoising of orca calls. Marine biologists are of course not the only ones who require clean audio signals for their research. Ornithologists alone deal with a great variety of different noise. One that studies urban bird species would like city sounds to be filtered from his audio samples, whereas one who works with tropical birds rather wants his recordings clean from forest noise. One could argue that almost every biologist who analyses recordings of animal calls would have use for a denoising tool kit.
Another task where audio denoising is of great relevance is when interpreting and processing human speech. It can be used to improve the sound quality of a phone call or a video conference, to preprocess a voice command to a virtual assistant on a smartphone, to improve voice recognition software and many other examples. Even in medicine it can help when analysing pulmonary auscultative signals, which is the key method to detect and evaluate respiratory dysfunctions.4
It therefore makes sense to generalize ORCA-CLEAN and to make it trainable for other animal sounds, perhaps even human speech, or body noises. One would then have a generalized version of ORCA-CLEAN, which can then be trained according to the desired purpose. The goal of this thesis will be to describe and explain the respective changes in the code, as well as to evaluate how differently trained models perform on audio recordings of different animals. The transfer from a model specialized on orcas to one specialized on another animal species will be demonstrated using recordings of hyraxes. The data used contains tapes of 34 hyrax individuals. For each individual there are multiple tapes available, and for each tape there is a corresponding table containing information like the exact location, the length, the peak frequency or the call type for each call on the tape.
The hyrax is a small hoofed mammal of the family of Procaviidae.5, 6 They usually weigh 4 to 5 kg, are about 30 to 50 cm long and are mostly herbivorous.5 Their calls, especially the advertisement calls, are helpful for distinguishing different hyrax species and for analysing the animals’ behaviour.6
Here are a few rough approaches how I would realize this thesis. I would begin by modifying the ORCA-CLEAN code. Since orca calls very much differ from hyrax ones in terms of frequency range as well as in length, the prepocessing of the audio tapes would have to be modified. I would also like to add some more input/output spectrogram variants to the training process.
One could use pairs of noisy and denoised human speech samples for example, or a pure noise spectrogram versus a completely empty one. The probability with which each of these variants is chosen could additionally be made variable.
After that, I would train different models with hyrax audio tapes, including original ORCA-CLEAN as well as an the newly created adaptions, and evaluate their performance. Since the provided hyrax tapes aren’t all equally noisy, they can be sorted by the so-called Signal to Noise Ratio (SNR). One can then compare these values before and after denoising, e.g., by correlating them, and check if the files were denoised correctly or if relevant parts were removed.
With help of these results further alterations can be made, for example by changing the probabilities of the training methods or by adapting the hyperparameters of the deep network, until hopefully in the end, a suitable network which doesn’t require huge amount of data is the result.
I hope I was able to give some insight into what I imagine the subject to be, and how I would roughly execute it.
Sources
[1] https://lme.tf.fau.de/person/bergler/#collapse_0
[2] C. Bergler, H. Schröter, R. X. Cheng, V. Barth, M. Weber, E. Nöth, H. Hofer, and A. Maier, “ORCA-SPOT: An Automatic Killer Whale Sound Detection Toolkit Using Deep Learning” Scientific Reports, vol. 9, 12 2019.
[3] C. Bergler, M. Schmitt, A. Maier, S. Smeele, V. Barth, and E. Nöth, “ORCA-CLEAN: A Deep Denoising Toolkit for Killer Whale Communication“ Interspeech 2020 (pp. 1136-1140). International Speech Communication Association.
[4] F. Jin and F. Sattar “Enhancement of Recorded Respiratory Sound Using Signal Processing Techniques“ In A. Cartelli, M. Palma (Eds.) “Encyclopedia of Information Communication Technology” (pp. 291-300), 2009.
[5] https://www.britannica.com/animal/hyrax
[6] https://www.wildsolutions.nl/vocal-profiles/hyrax-vocalizations/

Automated Scoring of Rey-Osterrieth Complex Figure Test Using Deep Learning

New speech, motor and cognitive exercises for mobile Parkinson’s Disease monitoring with Apkinson

Writer Verification/Identification using SuperPoint and SuperGlue

Self-supervised learning for pathology classification

Motivation
Self-supervised learning is a promising approach in the field of speech processing. The capacity to learn
representations from unlabelled data with minimal feature-engineering efforts results in increased
independence from labelled data. This is particularly relevant in the pathological speech domain, where the
amount of labelled data is limited. However, as most research focuses on healthy speech, the effect of selfsupervised
learning on pathological speech data remains under-researched. This motivates the current
research as pathological speech will potentially benefit from the self-supervised learning approach.
Proposed Method
Self-supervised machine learning helps make the most out of unlabeled data for training a model. Wav2vec
2.0 will be used, an algorithm that almost exclusively uses raw, unlabeled audio to train speech
representations [1][2]. These can be used as input feature alternatives to traditional approaches using Mel-
Frequency Cepstral Coefficients or log-mel filterbanks for numerous downstream tasks. To evaluate the
performance of these trained representations, it will be examined how well they perform on a binary
classification task where the model predicts whether or not the input speech is pathological.
A novel database containing audio files in German collected using the PEAKS software [3] will be used.
Here, patients with speech disorders, such as dementia, cleft lip, and Alzheimer’s Disease, were recorded
performing two different speech tasks: picture reading in !!Psycho-Linguistische Analyse Kindlicher Sprech-
Störungen” (PLAKSS) and “The North Wind and the Sun” (Northwind) [3]. As the database is still being
revised, some pre-processing of the data must be performed, for example, removing the voice of a (healthy)
therapist from the otherwise pathological recordings. After preprocessing, the data will be input to the
wav2vec 2.0 framework for self-supervised learning, which will be used as a pre-trained model in the
pathology classification task.
Hypothesis
Given the benefits of acquiring learned representations without labelled data, the hypothesis is that the selfsupervised
model’s classification experiment will outperform the approach without self-supervision. The
results of the pathological speech detection downstream task are expected to show the positive effects of
pre-trained representations obtained by self-supervised learning.
Furthermore, the model is expected to enable automatic self-assessment for the patients using minimallyinvasive
methods and assist therapists by providing objective measures in their diagnosis.
Supervisions
Professor Dr. Andreas Maier, Professor Dr. Seung Hee Yang, M. Sc. Tobias Weise
References
[1] Schneider, S., Baevski, A., Collobert, R., Auli, M. (2019) wav2vec: Unsupervised Pre-Training for
Speech Recognition. Proc. Interspeech 2019, 3465-3469
[2] A. Baevski, Y. Zhou, A. Mohamed, and M. Auli, “wav2vec 2.0: A Framework for Self-Supervised
Learning of Speech Representations,” in Advances in Neural Information Processing Systems. 2020, vol. 33,
pp. 12449–12460, Curran Associates, Inc.
[3] Maier, A., Haderlein, T., Eysholdt, U., Rosanowski, F., Batliner, A., Schuster, M., Nöth, E., Peaks – A
System for the automatic evaluation of voice and speech disorders, Speech Communication (2009)