---
title: "LFA App User's Guide"
author: "Filip Paskali, Weronika Schary, Matthias Kohl"
date: "`r Sys.Date()`"
output:
rmarkdown::html_vignette:
toc: true
bibliography: lit.bib
vignette: >
%\VignetteIndexEntry{LFA App User's Guide}
%\VignetteEngine{knitr::rmarkdown}
%\VignetteEncoding{utf8}
---
# Introduction
The LFA shiny apps [@Shiny2020] consist of four modular Shiny applications:
(1) **LFA App core** for image acquisition, editing, region of interest definition
via gridding, background correction with multiple available methods, as well as
intensity data extraction of the pre-defined bands of the analysed LFAs. More
precisely, it consists of Tab 1, Tab 2 and parts of Tab 3 described in detail
below.
(2) **LFA App calibration** extends the LFA App core by methods for merging the
intensity data with information from experiments, computation of calibration
models and the generation of a report about the calibration analysis. The
functionality corresponds to the Tabs 1-6 described below.
(3) **LFA App quantification** enables quantification of the extracted intensity
values via loading existing calibration models. It extends the LFA App core
by Tab 7 described below.
(4) **LFA App analysis** includes the full functionality mentioned above and
enables full analysis in one application. That is, it consists of Tab 1-7.
The graphical user interface of the apps is built in a modular way divided into
several tabs, where each tab represents a specific step of the workflow. While
the applications can be used in a sequential fashion, the specific steps can
also be carried out individually.
# Testing our apps without installing
Before installing our package, one can also test our apps on https://www.shinyapps.io.
The desktop version of our full purpose analysis app is at
https://lfapp.shinyapps.io/LFAnalysis/
The respective mobile version is at
https://lfapp.shinyapps.io/mobile_app/
# Installation
The package requires Bioconductor package EBImage, which should be installed
first via.
```{r, eval = FALSE}
## Install package BiocManager
if(!requireNamespace("BiocManager", quietly = TRUE))
install.packages("BiocManager")
## Use BiocManager to install EBImage
BiocManager::install("EBImage", update = FALSE)
```
Our package depends on the most recent version of package shinyMobile, which
must be installed from github (https://github.com/RinteRface/shinyMobile) by
```{r, eval = FALSE}
## Install package remotes
if(!requireNamespace("remotes", quietly = TRUE))
install.packages("remotes")
## Install package shinyMobile
remotes::install_github("RinteRface/shinyMobile")
```
For generating our vignette and automatic reports, we need packages knitr and
rmarkdown, which will be installed next.
```{r, eval = FALSE}
## Install package knitr
if(!requireNamespace("knitr", quietly = TRUE))
install.packages("knitr")
## Install package rmarkdown
if(!requireNamespace("rmarkdown", quietly = TRUE))
install.packages("rmarkdown")
```
Finally, one can install package LFApp, where all remaining dependencies will
be installed automatically.
```{r, eval = FALSE}
## Install package LFApp
remotes::install_github("fpaskali/LFApp", build_vignette=TRUE)
```
# Start Apps
As already described above, package LFApp includes four different shiny apps
where there is a desktop and a mobile version for each app. They can be started
with one of the following commands:
```{r, eval = FALSE}
## desktop versions
## LFA App core
LFApp::run_core()
## LFA App quantification
LFApp::run_quan()
## LFA App calibration
LFApp::run_cal()
## LFA App full analysis
LFApp::run_analysis()
## mobile versions
## LFA App core
LFApp::run_mobile_core()
## LFA App quantification
LFApp::run_mobile_quan()
## LFA App calibration
LFApp::run_mobile_cal()
## LFA App full analysis
LFApp::run_mobile_analysis()
```
# Tab 1: Cropping and Segmentation
## Upload Image or Choose Sample Image
The first step consists of loading an image of one or several lateral flow strips.
For trying out the app one can also load a sample image provided with the package.
For the purpose of demonstration we will use the sample image provided with the
package. The image can be rotated or flipped horizontally (button FH) and
vertically (button FV) via the rotation panel on the left hand side. It can also
be cropped to a specific size via double click on the interactive plot.
## Set number of strips and number of lines per strip
In the next step, one needs to select the number of strips shown in the image and
the number of lines (bands) per strip.
The maximum number of strips per image is 10, but in principle could be extended
to a higher number. The only requirements is that the strips are regularly spaced
with identical or at least similar spaces between them and between the lines.
The minimum number of lines per strip is two, the maximum number of lines per
strip is six, since we are not aware of any lateral flow assay having more than
six lines. But again, this could be easily extended to a higher number.
## Apply Segmentation
After loading the image and selecting the number of strips as well as lines per strip,
one needs to click on the image and drag to generate a rectangular selection region
on the image. It is best, if each line is roughly in the middle of a respective segment.
In addition, there is a segment between two consecutive bands. This segment should
not include any part of a line, since it can be used for background correction;
see below. An example of a well selected cropping region is shown in the following
screenshot.
{width=100%}
By clicking "APPLY SEGMENTATION" the original image is cropped to size of the
selected region and segmented. The segments between the bands are used in our
quantile background correction method; see below. If you want to change the
cropped region you can select "RESET".
The cropping was adapted from the shiny app provided by package ShinyImage
[@shinyImage].
# Tab 2: Background
## Select Strip
If there is more than one strip on the analysed image, one first needs to select,
which strip shall be analysed.
## Optional: in case of color images
If the image is a color image, it will be transformed to grayscale. By default,
we apply the luminance approach, which converts color to grayscale preserving
luminance; that is, the grayscale values are obtained by
$$
0.2126 * R + 0.7152 * G + 0.0722 * B
$$
where R, G, B stands for the red, green and blue channel of the color image.
By selecting mode "gray", the arithmetic mean of the RGB values is used.
Furthermore, the selection of mode "red", "green" or "blue" allows a color
channel wise analysis of color images.
## Select threshold method and apply
There are four threshold methods, where the default is Otsu's method [@Otsu.1979].
Otsu's method returns a single intensity threshold that separates pixels into
foreground and background. It is equivalent to k-means clustering of the intensity
histogram [@Liu.2009]. Otsu and Li [@Li.1993, @Li.1998] are non-parametric,
fully automatic algorithms that find the optimal threshold for the image.
Additionally, two semi-automatic algorithms, namely Quantile and Triangle
[@Zack.1977] were included, to cover different images and cases where automatic
threshold results are not ideal.
The quantile method is a simple method that computes the specified quantile of
all pixel intensities of the segments between the lines (per strip). In most of
the images we have analysed so far, Otsu's method performed very well and better
than our quantile method.
However, in cases where the lines are unclear and very blurred our quantile method
may outperform Otsu's method. In case of the triangle method an additional
offeset (default = 0.2) is added to the computed threshold.
By clicking "APPLY TRESHOLD" the selected threshold method is applied to the
segmented images of the selected strip. The upper plots show the pixels that have
intensities above the background. The lower plots show the images after background
subtraction; see the screenshot below.
{width=100%}
The thresholds (top of the page) as well as calculated mean and median intensities
of the lines (bottom of the page) in order from top of the strip to the bottom
of the strip are shown as well.
## Add to intensity data
Clicking "ADD TO INTENSITY DATA" adds the mean and median of the background
subtracted intensities of the pixels with intensities above the threshold to the
data. Now, one can proceed with the second strip of the image, use a different
color conversion mode or go back to Tab 1 and load the next image. When all strips
and images are processed one can proceed with "SWITCH TO INTENSITY DATA".
## Switch To Intensity Data
Clicking "SWITCH TO INTENSITY DATA" changes the Tab to Tab 3.
# Tab 3: Intensity Data
Here, the latest version of the generated intensity data is shown in the Tab.
## Download data
By clicking "DOWNLOAD DATA" the data can be saved as a standard csv file.
## Restart with new data
We also provide a "DELETE DATA" button for restarting with new images or
uploading an already existing dataset.
## Upload existing data
Instead of generating new data, one can also upload already existing intensity
data, that can also be generated with a different software. This step can also
be seen as a second entry point of the app. The screenshot below shows an example
of data that was generated with the app saved and then loaded again.
{width=100%}
## Switch To Experiment Info
Clicking "SWITCH TO EXPERIMENT INFO" changes the Tab to Tab 4, where information
about the experiment can be loaded.
# Tab 4: Experiment Info
## Upload Experiment Info or upload existing merged data and go to calibration
One first can either upload information about the experiment in form of a .csv file
or upload already merged data (intensity data merged with experiment information).
An example of a table with information about the experiment is shown in the
screenshot below.
{width=100%}
This is a third optional starting point of the app. Here, one can also directly
start with already merged data and proceed with the calibration analysis.
## Select ID columns and merge datasets
For merging the intensity data with the information about the experiment, one
has to specify the names of the columns on which the merge should take place.
The default is "File", as a "File" column is generated when the intensity data
is computed with the app. By clicking "MERGE WITH INTENSITY DATA" the two
datasets will be merged. An example of a table with merged data is shown in the
screenshot below.
{width=100%}
## Download data
The merged data can be downloaded as a .csv file by clicking "DOWNLOAD DATA".
## Restart with new data
We again provide a "DELETE DATA" button for restarting with new images, uploading
new intensity data on Tab 3 or uploading an already existing merged dataset.
## Prepare Calibration
Clicking "PREPARE CALIBRATION" changes the Tab to Tab 5, where the data can be
further preprocessed and the calibration analysis can be started.
# Tab 5: Calibration
## Specify a folder for the analysis results
In the first step, a folder for the analysis results should be specified. If no
folder is provided, a new folder "LFApp" will be generated in the home directory
of the user.
## Upload existing preprocessed data
Instead of generating the preprocessed data with our app, one can also upload
preprocessed data and perform the calibration analysis on them. An example of
uploaded preprocessed data that were generated with our app and saved as a .csv
file is shown in the following screenshot.
{width=100%}
## Optional: average technical replicates
If the merged data includes technical replicates, these replicates can be averaged
either by the arithmetic mean or the median. For this purpose the name of the column,
which enables the identification of the replicates is required. By default we assume
that this column is called "Sample". In case there is more than one analyte/color
per line/band, one should set "Number of analytes/colors per line" to the respective
number. If this number is larger than 1, an additional field will be shown, where
one should enter the name of the column including the analyte/color information.
## Optional: reshape data from long to wide
If there is more than one analyte/color per line/band, one might want to combine
both information into one calibration model. For such cases it is useful to reshape
the data from long (analyte/color data in the rows) to wide (analyte/color data
in the columns).
{width=100%}
## Download data
By clicking "DOWNLOAD DATA", the data used for the calibration can be downloaded
as .csv file.
## Calibration by linear, local polynomial or generalized additive model
In the final step of this Tab, one has to specify the calibration model.
The model can the chosen via a checkbox (linear (lm), local polynomial (loess),
generalized additive model (GAM)). A column for concentration values has to be
selected. The concentration values can be logarithmized. In addition, one has
to specify a response variable.
{width=100%}
If only a subset of the data shall be used for the calibration analysis, an
logical R expression can be specified in the field below
"Optional: specify subset (logical R expression)". This expression will be applied
to select the respective subset.
## Run calibration analysis
By pressing "RUN CALIBRATION ANALYSIS" the RData-file "CalibrationData.RData"
will be generated and saved in the specified analysis folder. Next, the R markdown
file "CalibrationAnalysis(model).Rmd", where model = lm, loess, gam, will be
copied to the same folder and will be rendered into file
"CalibrationAnalysis(model).html" by using R package "rmarkdown" [@rmarkdown].
The results of the calibration analysis will be saved in file
"CalibrationResults.RData" and will be used to generated a brief overview
of the results that will be shown on Tab 6. All files will remain in the
folder selected for the analysis results. That is, one may use and modify these
files for an extended analysis. In addition, the fitted values for
the concentrations are added to data used for the calibration. That is, one
can also run several different calibration models, download the calibration
data and use the data to compare the results of different calibration models.
# Tab 6: Results
This Tab shows a brief overview of the analysis results as shown in the following
screenshot.
{width=100%}
## Open analysis report
By clicking "Open" the full report of the calibration analysis will be opened
in the standard browser. The first part of the report is visible in the following
screenshot.
{width=100%}
# Tab 7: Quantification
The final tab of our application enables the quantification of intensity values
with the help of a calibration model. You can upload an existing model from a
previous calibration analysis and use it to predict the concentrations for the
intensity values acquired beforehand by clicking "PREDICT". Via the "DOWNLOAD DATA"
button the data table can be saved as a .csv file containing the intensity values
as well as the predicted concentrations.
{width=100%}
# Required R packages
Our app requires the following R packages to work properly:
* stats: The R Stats Package [@R2020]
* mgcv: Mixed GAM Computation Vehicle with Automatic Smoothness Estimation [@mgcv]
* shiny: Web Application Framework for R [@Shiny2020]
* shinyjs: Easily Improve the User Experience of Your Shiny Apps in Seconds [@shinyjs.2020]
* shinythemes: Themes for Shiny [@shinythemes.2018]
* fs: Cross-Platform File System Operations Based on 'libuv' [@fs.2020]
* shinyFiles: A Server-Side File System Viewer for Shiny [@shinyfiles.2020]
* Bioconductor package EBImage: R package for image processing with applications to cellular phenotypes [@Pau.2010]
* DT: A Wrapper of the JavaScript Library 'DataTables' [@DT.2020]
* rmarkdown: Dynamic Documents for R [@rmarkdown]
* ggplot2: Elegant Graphics for Data Analysis [@Wickham.2016]
# References