Usiigaci: Instance-aware cell tracking in stain-free phase contrast microscopy enabled by machine learning

Hsieh-Fu Tsai^1,2, Joanna Gajda³, Tyler F.W. Sloan⁴, Andrei Rares⁵, Jason Ting-Chun Chou¹, and Amy Q. Shen¹

^{1Micro/Bio/Nanofluidics Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa Japan}

^{2Research Fellow of Japan Society of Promotion for Science}

^{3AGH University of Science and Technology, Krakow, Poland}

^{4Quorumetrix Solutions, Canada}

^{5ImagineA, The Netherlands}

Usiigaci, ウシーガチ, ushi:gachi in Hepburn romanization, in Ryukyuan language means "tracing", "透き写し" in Japanese，i.e. drawing the outline of objects based on a template. The process is essentially what we do: following the morphology and position of cells under microscope, analyze how cell respond upon environmental perturbation in the microenvironment. However, this process is bloody tedious if done by human, and now we developed a pipeline using the famous Mask R-CNN to do this for us. Letting us not only track objects by their position but also track how their morphology changes through time.

Zernike's phase contrast microscopy is a brightfield microscopy technique developed by Frits Zernike and by inventing the phase contrast technique, he won the 1953 Nobel Prize for physics. Phase contrast microscopy is favored by biologists because it translates the phase difference caused by cell components into amplitude thus making these transparent structures more visible. Also, in comparison to differential interference contrast microscopy, phase contrast microscopy works without problems with different substrates especially on plastics that are highly birefringent.

Phase contrast microscopy images are notoriously difficult to segment by conventional computer vision methods. However, accurate whole cell outline segmentation and resolution of cells that contact each other are essential as the first step for cell tracking in automated microscopy needs accurate cell identification. Tracking and visualization of the cellular dynamics based on the segmentations help us understand and quantitative analyze cellular dynamics.

We report Usiigaci, a semi-automated pipeline to segment, track, and visualize cell migration in phase contrast microscopy.

High accuracy instance-aware segmentation is achieved by adapting the mask regional convolutional neural network (Mask R-CNN), winner of Marr prize at ICCV 2017 by He et al.. We built Usiigaci's segmentation module based on the Mask R-CNN implementation by Matterport. Using 50 manually-annotated cell images for training, the trained Mask R-CNN neural network can generate high accuracy whole cell segmentation masks that allow us to analyze both cell migration and cell morphology which are difficult even by fluorescent imaging.

Cell tracking and data verification can be done in ImageJ, other existin tracking software such as Lineage Mapper, or Usiigaci tracker that we developed based on open-source trackpy library. A GUI is also developed to allow manual data verification to check tracking results and delete bad results.

A Jupyter Notebook and the corresponding python script are developed for automated processing and visualization of the tracked results. Step-centric and cell-centric parameters are automatically computed and saved into additional spreadsheets where users can access and reuse in statistical software or R. Automated visualization of cell migration is also generated for cell trajectory graphs, box plots, etc.

• Cell trajectory graph
  • 2D hair ball color coded by track
  • 2D hair ball color coded by time (Imaris like)
  • 2D hair ball color coded by direction (Ibidi like)
  • 2D hair ball color coded by direction length
  • 3D hair ball with z as time
  • scatter plot in gif
• Automated cell migration analysis
  • computation of step centric parameters
    • instantaneous displacement
    • instantaneous speed
    • turn angle
    • direction autocorrelation
  • compuatation of cell centric parameters
    • cumulative distance (total traveled distance)
    • Euclidean distance
    • net velocity
    • end point directionality ratio
    • orientation (cell alignment index)
    • Directedness
  • save individual cell track data
  • save summary of each cell throughout experiment
  • save summary of ensemble at each time point
• automated plotting of descriptive statistics
  • rose histogram of cell orientation
  • box plots, violin plots, and time series plots of cell migration parameters
  • frequency histograms

We worked on Usiigaci for our work on cell electrotaxis study, and hopefully can devote to current international effort to standardize cell migration experiments.

We hope Usiigaci is interesting to you and if it is useful for your research, please cite our paper.

Hsieh-Fu Tsai, Joanna Gajda, Tyler F.W. Sloan, Andrei Rares, and Amy Q. Shen, SoftwareX, 9, 230-237, 2019

Accessible here

Usiigaci is released under MIT License.

Copyright (c) 2018 Okinawa Institute of Science & Technology Graduate University

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and 
associated documentation files (the "Software"), to deal in the Software without restriction, including 
without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 
copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the 
following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions 
of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT 
LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO 
EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER 
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE 
USE OR OTHER DEALINGS IN THE SOFTWARE.

TensorFlow is open-sourced under Apache 2.0 opensource license.

Keras is released under MIT license

The copyright of PyQT belong to Riverbank Computing ltd.

Pandas is released under BSD 3-Clause License. Copyright owned by AQR Capital Management, LLC, Lambda Foundry, Inc. and PyData Development Team.

Trackpy is released under BSD 3-Clause License. Copyright owned by trackpy contributors.

NumPy and SciPy are released under BSD-new License

Scikit-image is released under modified BSD license

PIMS is released under modified BSD license

Matplotlib is released under Python Software Foundation (PDF) license

Seaborn is released under BSD 3-clause license

ffmpeg is licensed under LGPL 2.1 license

PyQtGraph is released under MIT license

Future work

(2019.Sep.01) We are working on a new architecture to become more light weight and flexible.

Mask R-CNN segmentation

• Add a function to save only the best model weight during training
• Add a function to compute F1 score, Jaccard index, Accurady, Precision to a test dataset after training
• pretrain model weights for DIC microscopy.
• pretrain model weights for recognition of nucleus
• add bounding box as an output format (overlay over original image)
• change output mask to 16 bit to support more instance to be recognized
• Multiclass segmentation to realize identification of mitotic cells.
• Multiclass segmentation to realize label-free co-cultured cell segmentation.
• Add multiple GPU training and inference support - likely need to rework the fundamentals.
• pretrain model weights for Atto cytowatcher microscope
• Pretrain model weights for Essen Incucyte S3
• Pretrain model weights for bacteria

Tracking

• Add lineage tracking function
• Add support for ultra-long time series tracking
• Add batch tracking scripts

data processing

• Add data analysis script for specific time frame
• Add output into rois for later use coupling imageJ (for users to quantify the roi)
• plotly based data visualization for rare event analysis.
• Add calculation of cell doubling time
• Add rare event detection
• Add confluency calculation
• Faster more integrated data processing pipeline, perhaps on C++
• Add cell contour vector analysis
• Add multiclass percent stacked bar plot.

Call for collaboration

We are still improving the software. If you'd like, please adapt the source code on your own dataset. If you are willing to share you dataset, but limited by computing power, we can initiate collaboration. We can try to annotate your data and train a model weight for your data or incorporate your data together with our dataset that you can use. If interested, please contact to the corresponding authors.

Acknowledgement:

This work is supported by JSPS KAKENHI Grant JP1700362 and Okinawa Institute of Science and Technology Graduate University with subsidy funding from the Cabinet Office, Government of Japan.

Dependencies

Hardware

A computer with CUDA-ready GPU should be able to run Usiigaci. We built the development machine in linux environment on an Alienware 15 with NVIDIA GTX 1070 8GB GPU. But Usiigaci has been verified working on the following machines.

1. Windows 10 64 bit on Alienware 15 with GTX 1070 8GB
2. Linux 64 bit on Alienware 15 with GTX1070 8GB or with a GTX 1080Ti 11GB in an Alienware graphics amplifier
3. Windows 7 64 bit on Dell Precision Workstation T7810 with Quadro M4000
4. Ubuntu 16.04 on Dell Precision Workstation T7810 with Quadro M4000

We see a high efficiency on running Usiigaci in a linux machine.

Mask R-CNN

our working linux setup

• Kubuntu 16.04 Linux
• NVIDIA graphics card with compute capability > 5.0
• CUDA 9.1 9.0
• TensorFlow 1.4 1.7 with GPU
• Keras 2.1.2 2.1.5
• Anaconda with Python 3.6

note: multiple GPU not working

our working windows setup

• Windows 10 64bit
• NVIDIA graphics card GTX 1070 8GB
• Anaconda with Python 3.6
• Tensorflow 1.9 with GPU
• CUDA 9.0
• CuDNN 7.1.4 for CUDA9.0
• Keras 2.1.6

The exact version of CUDA and Keras is required to work with the Matterport Mask R-CNN repo.

setup tutorial on an Ubuntu linux 16.04 LTS from scratch. (update 20190220)

installation of Ubuntu 16.04 LTS

download the Ubuntu 16.04 and do not upgrade to 18.04

installation of cuda

note: don't worry about getting the up-to-date graphics driver prior than cuda. the driver will be installed when cuda is installed.

1. preinstall actions

   • verify cuda-capable gpu

   lspci | grep -i nvidia
   

   • verify a supported version of linux

   uname -m && cat /etc/*-release
   

   • verify the system has gcc installed

   gcc --version
   

2. disable nouveau

   lsmod | grep nouveau
   

   if prints anything, means neouveau is loaded and must be disabled before proceeding to install cuda

   navigate to /etc/modprobe.d/

   sudo nano ./blacklist.nouveau.conf
   

   enter the following in the file

   blacklist nouveau
   options nouveau modeset=0
   

   save regenerate the kernel initrd by the command

   sudo update-initramfs -u
   

3. download cuda 9 deb from nvidia 9.0 local deb

   navigate to download folder

   sudo dpkg -i cuda-repo-ubuntu1604-9-0-local_9.0.176-1_amd64.deb
   

   installation of public gpg key

   sudo apt-key add /var/cuda/repo-9-0-local/7fa2af80.pub
   sudo apt-get update
   sudo apt-get install cuda
   

4. post installation operations edit bashrc file in user folder add the following two lines

   export PATH=/usr/local/cuda-9.0/bin${PATH:+:${PATH}}
   export LD_LIBRARY_PATH=/usr/local/cuda-9.0/lib64\${LD_LIBRARY_PATH:+:${LD_LIBRARY_PATH}}
   

5. installation of cudnn it is necessary to install cudnn of the right version otherwise the tensorflow will have error download from nvidia libcudnn7_7.0.5_15 for cuda 9.0 runtime library as well as developer library

   navigate to download folder

   sudo dpkg -i libcudnn7_7.0.5.15-1+cuda9.0_amd64.deb
   sudo dpkg -i libcudnn7-dev_7.0.5.15-1+cuda9.0_amd64.deb
   

installation tensorflow

1. installation python 3 and virtualenv

   sudo apt update
   sudo apt install python3-dev python3-pip python3-tk
   sudo pip3 install -U virtualenv
   

2. installation of tensorflow create a virtual environment, let it be tensorflow or anything you want to name after.

   virtualenv --system-site-packages -p python3 tensorflow
   

   afterward enter the virtual environment tensorflow

   source tensorflow/bin/activate
   

   pip install --upgrade pip
   pip install tensorflow-gpu==1.7
   

   exit bash and restart test tensorflow installation

   source tensorflow/bin/activate
   python
   import tensorflow as tf
   

   there should be no error

installation of other dependencies for usiigaci

source tensorflow/bin/activate
pip install opencv-python tqdm docopt imgaug h5py
pip install keras==2.1.5

voila there you should have a working environment for usiigaci on the linux try it out with the inference script

Python tracking GUI

• Python 3.4+
• Trackpy
• Scipy
• scikit-image==0.13
• Numpy
• Pandas
• Matplotlib
• PIMS
• PyQt5
• PyQtGraph
• ffmpeg
• Pandas

Single cell migration data analysis Notebook

• Python3.4+
• Numpy
• Scipy
• Pandas
• Matplotlib
• seaborn
• imageio
• read_roi
• (jupyter-navbar)

How to use Usiigaci

Video tutorial

Youtube link

Segmentation using Mask R-CNN

1. Download the trained weights

   Due to the file size limit of Github, please download the three weights we used for our phase contrast microscope in the Dropbox folder.

   Note: These are trained for phase contrast images on Nikon Ti-E with 10X phase contrast objective, 1.5X intermediate magnification with a Hamamatsu Orca Flash V4.0 sCMOS camera at 1024x1022 size. We have found Mask R-CNN to be more resilient to environmental changes, but if the results from pretrained weights are suboptimal, you can see the last section to train the network with your own data.

   The inference script "/Mask R-CNN/Inference.py" is the script you need to run on images for generating corresponding masks.

2. (organize you image data)

   assuming you're using NIS element, you can export the images by xy, t, and c if you have one.

   use the NIS_export_organize sorting script to the images so that for each xy dimension, all the time step images are organized in a folder.

3. edit the inference.py script

   line 288 change the path to the folder you want to run inference.

   The script will automatically search all th nested directories of this folder and run inference on each of them.

   line 292:294 change the path to the trained weights.

   you can specify multiple weights from different training, the inference code will run predictions using each model weight and average them. This costs more time to do inference. But since all neural networks can have false negatives (blinking), this can alleviate the false result frequency.

   line 296 adjust the model_list by the model_path you define.

4. run the inference.py script.

   python inference.py
   

   the keras and tensorflow should take care of looking for the main GPU and run the inference.

5. instance-aware mask images will saved in a mask folder be right next to the folder you defined and you can use it to run in Lineage Mapper or etc.

Data verification/tracking

Tracking on ImageJ

1. Load the images in ImageJ as a stack, you can verify the data and do manual tracking.
2. for ease of tracking, you can use an ImageJ plugin developed by Emanuele Martini.
   1. threshold the instance-aware stack to binary masks.
   2. run the plugin, you can find one target cells on the first slice with magic wand tool and click ok, based on overlapping, the plugin will find the target ROIs in the rest of the slices and add them into ROI manager.
   3. in ROI manager, you can edit each ROI and click "Measure" to output measured results for further analysis.

Tracking using Usiigaci tracker

A python tracking software is developed based on the trackpy libraries and others. The tracker is the work by Dr. Andrei Rares.

Prerequisite:

1. install required packages

   pip install pyqt5 pyqtgraph pims pandas trackpy pillow imageio--ffmpeg scikit-image==0.13
   

   some times pillow nees to be upgraded

   pip install --upgrade pillow
   

2. modify the Imageitem class of PyQtGraph overwrite the ImageItem.py into python/site-packages/pyqtgraph/graphicsItems folder

   If working in the virtual environment tensorflow: it will be under /home/username/tensorflow/lib/python3.5/site-packages/pyqtgraph/graphicitems/

3. if needed you can chage the suffix for the mask folder and the pixel scale in the params settings around line 342 in cell_main.py

Using the Usiigaci tracker:

1. Launch the tracker GUI by

   python cell_main.py
   

   The left panel is for displaying raw image. Right panel is for displaying mask images. Bottom are two synced scrollbars so users can check each frame of a time lapse experiments. On the top left is the parameters setting. If the mask folder bear a different suffix, please change here. On the right is a list for all the cell tracks. Upon finish of tracking, numbered ids and cell track list will be updated.

2. open the folder to the cell microscopy images.

   The tracker will load the segmented masks by looking for mask folder name with the name of the cell microscopy name + mask folder suffix

   remember to check the suffix is correct or not. If the suffix is incorrect, the tracker failed to find the mask, it will terminate. the suffix differs depend if you have averaging turned on or not.

   adjust the pixel scale if necessary also

3. Run cell tracking and the cell tracking will be done on using the mask generated from Mask R-CNN.

   The tracking results that are suboptimal from segmentation error were repaired. The tracking takes about a minute or two depending on the number of objects and frames.

4. After tracking is finished. If there are bad tracks. Users can deselect that track in the cell list.

   Alternatively, users can also take advantage of select all tracks, or select complete tracks (only the tracks that are recognized and tracked through all the frames).

5. Click "Save selection" to save the track results into "tracks.csv", labeled images, as well as rendered movies (you need ffmpeg) into a folder.

6. The XY coordinate, area, perimeter, and angle are extracted using scikit-image's measure.regionprops. Note: angle between long axis and x axis in radians was extracted using region.orientation, but not to confuse with the orientation index in cell migration, which is cosine 2*angle.

Tracking using other tracking software

Alternatively, you can load the indexed 8 bit masks files into Lineage Mapper, or Metamorph which the tracking can be easily done.

Data analysis and visualization

Currently we have coded data loading interfaces for 5 types of analyzed data. but you can look into the codes to adapt the output data in your preference also. One needs to make sure the data outputed from each tracking software is already calibrated into micron since the data analysis script does not take account of this anymore.

1. ImageJ tracked multi-measure output

   each cell track of all time points followed by another

2. Lineage Mapper tracked results

   only cells that did not divide, fusion or lost throughout time lapse is picked up.

3. Metamorph tracked data

4. Usiigaci tracker tracked data

   tracks.csv files are generated from the tracker. One can specify one file, or in the folder mode, the script will looks for all nested folders each containing a tracks.csv file and automated data analysis will be carried out on all the tracks.csv files. This will enable user to easily process large amount of data for cell analysis.

of all, since Lineage mapper and Metamorph only provide cell centroids data, the parameters regarding cell area, perimeter and orientation cannot be analyzed (despite error the analysis should still be done, just lack of data during data analysis and visualization in the notebook)

Using the data analysis script

1. install dependencies

   pip install ipython numpy pandas scipy matplotlib seaborn imageio read_roi
   

2. navigate to Usiigaci-master/DataAnalysis edit the Data_analysis_script.py or launch jupyter notebook in the folder and open the data_analysis ipynb

3. edit the experimental details in the dataanalysis script

   • line 52 : number of frames
   • line 54 : time interval of the time lapse
   • line 58 : the folder path to your data
   • line 60 : what kind of data your are processing, single csv file, or multiple tracks.csv in nested folders. (note right now only usiigaci is supported)
   • line 62 : what kind of the data? from imageJ, metamorph, or usiigaci tracker.

4. note the folder path definition under windows and under linux is slightly different. adjust if necessary

How to make your own training data and train them.

We manually annotate training data (phase contrast image acquired on Nikon Ti-E microscope with 10X Ph-1 objective and 1.5X intermediate magnification on Hamamatsu Orca Flash V4.0 with 2x2 binning) using opensource software Fiji ImageJ.

1. manually outline cell into ROI

   Load the image into ImageJ and use the freehand tool to outline each cell into individual ROI and save into ROI manager. (a Wacom tablet or Apple ipad with apple pencil come in handy)

2. create instance masks.

   Use a plugin called LOCI from University of Wisconsin, the ROI map function will index each individual ROI and output a 8bit indexed mask, save this mask as (labeled.png).

   save a raw image file and annotated mask into individual folder as a set in each folder.

3. run the preprocess_data.py to change the colored into gray scale 8 bit image. Alternatively, if you already have the 8 bit gray scale image with each cell having its index. you're good to go by naming them as "instance_ids.png"

4. run the train.py

   several variables to keep in mind line 22 input channel should be your training data channel filename line 29: IMAGES_PER_GPU, adjust according to your GPU memory line 31: In my system, it is essential two classes training keep it 2. Multiclass is not tested yet. line 33: STEPS_PER_EPOCH, put in the number of your training data line 34: VALIDATION_STEP, put in the number of your validation data

   for the rest of parameters, you can play around. If your image is of high intensity or low intensity, you might have to adjust MEAN_PIXEL on line 71 to the np.array of the mean of RGB of the image.

   Adjust the training epochs for the heads and all layers on line 188 and 196. modify the path to train_dir, val_dir, out_dir, and pretrained weight to start. from line 211-217

   in some cases if tensorflow-gpu takes alot of cpu time and lags your system, you might want to go into the model.py and find multiprocessing and set it to False.

We used 50 sets of training data. you can find the training data we made in the train and val folder. 45 sets are used in training and 5 sets are for validation. We trained additional 200 epochs of headers and 300 epochs on all layers based on a trained network from Matterport with MS COCO dataset.

The original ROIs used in the ImageJ also contains in the folder. You can use this to train on different neural network architect or on the DeepCell

We have found that Mask R-CNN network seems to be more resilient against environmental interferences in microscopy (out of focus, strong illumination, low light, etc) and the performance does not drop when segmenting cells with morphology that are significantly different from the cells in training set.

If the current trained network is suboptimal for you, be it poor accuracy or you have different size of images (which often need retraining of neural network), you can annotate your data by the same method and train further to see if it improves.