Building digital pathology web apps with PHP

PHP != Python

Earlier we announced the availability of our PHP API.

It is worth pointing out that not all functionality from the Python API was taken over in the PHP API.

In turn, the PHP API introduces some interesting options weren’t available in the original Python interface, either (and that are probably worth bringing over to our Java API as a result).

Some functionality is (or will be, based on our most recently gained insights) available in all platform. We leave it up to you to determine which one makes the most sense given your habitat.

Here’s an interesting example. In our Python tutorial series, one of the things we do is load a slide’s thumbnail and send it to MatPlotLib’s pyplot.

Translating our Python functionality to PHP, we get:

<?php
include_once "lib_pathomation.php";

Use Pathomation\Core;

// connect to PMA.start
$session = Core::connect();

// pick up the first slide available in the C:\my_slides directory
$slides = Core::getSlides("C:/my_slides/", $session);
$my_slide = $slides[0];

// retrieve the slide's thumbnail as a GD image object
$thumb = Core::getThumbnailImage($my_slide);

// output JPEG content to webbrowser
header("Content-Type: image/png");
imagejpeg($thumb);
imagedestroy($thumb);
?>

However, this is a rather futile exercise: we’re sending image content back to the browser. A much easier way is to send back a URL to the browser of where the thumbnail is located. Let the browser figure it out from there; that’s why it exists in the first place.

A more PHP-ish way to render a slide’s thumbnail is:

<?php
 include_once "lib_pathomation.php";

Use Pathomation\Core;

// connect to PMA.start
 $session = Core::connect();

// pick up the first slide available in the C:\my_slides directory
 $slides = Core::getSlides("C:/my_slides/", $session);
 $my_slide = $slides[0];

header("location: ".Core::getThumbnailUrl($my_slide));
 ?>

The following syntax then just looks silly:

<img src="showThumbnail.php?slide=<?php echo urlencode($my_slide); ?>" />

Compare this to the following:

<img src="<?php echo Core::getThumbnailUrl($my_slide); ?>" />

Remember Larry Wall: why bother parsing the content of the thumbnail first ourselves, if we can completely delegate this to the webbrowser?

We still take care to provide data in a host environment’s most “naturally” feeling format.

Case in point: in Python we give you image data in PIL(low) format, in PHP we use GD.

The question that you have to ask yourself: does it make sense to work with GD image data yourself, or is it easier and more convenient to refer to a resource by its URL directly?

PHP introduction

Let’s look at some simple PHP-Pathomation interaction code. The following code is pretty much standard for each script you’ll write:

// include the interaction library
include_once "lib_pathomation.php";

// indicate what functionality you want from the library
Use Pathomation\Core;

// connect to PMA.start
$session = Core::connect();

Note that when you connect to a commercial version of PMA.core, only the last line of your code needs to change:

$session = Core::connect("http://my_server/my_pma_core", "user", "pass");

More so then in Python, in PHP you have to frequently ask yourself whether an action is taking place on the webserver back-end side or in the webbrowser client.

A good example of this is the isLite() method. Similar to its Python (and Java) counterpart, it checks and verifies PMA.start is found running. This function only is useful when you’re either using the PHP Command-line interface (CLI):

<?php
// load library
require "lib_pathomation.php";
use Pathomation\Core;

// test for PMA.core.lite (PMA.start)
echo "Are you running PMA.core.lite? ".(Core::isLite() ? "Yes!": "no :-(");

Alternatively, the method can be used when you’re developing for PMA.start and you’re guaranteed to have server and client operate at the level of the same localhost setup.

Working with slides

The PHP Core class comes with a number of methods to navigate WSI slides on your local hard disk. Most often you’ll be alternating between getDirectories and getSlides.

Here’s a script that will allow you to navigate your hard disk in a tree-like fashion (place this in c:\inetpub\wwwroot of your (localhost) IIS setup):

<?php
require_once "lib_pathomation.php";

use Pathomation\Core;

if (!Core::isLite()) {
 die("PMA.start not found");
}

Core::connect();

echo "<ul>";
if (!isset($_GET["p"])) {
 foreach (Core::getRootDirectories() as $rd) {
  echo "<li><a href='?p=".urlencode($rd)."'>$rd</li>";
 }
} else {
 $parts = explode("/", $_GET["p"]);
 foreach (Core::getRootDirectories() as $rd) {
  if ($parts[0] == $rd) {
   echo "<li><b>$rd</b>";
   foreach (Core::getDirectories($rd) as $subdir) {
    echo "<ul>";
    $subdirParts = explode("/", $subdir);
    if (stripos($_GET["p"], $subdir) === 0) {
     echo "<li><b>".end($subdirParts)."</b>";
     // keep drilling down, or see if you can retrieve slides as well     
     echo "</li>";
    } else {
     echo "<li><a href='?p=".urlencode($subdir)."'>".end($subdirParts)."</a></li>";
    }
    echo "</ul>";
   }
   echo "</li>";
  } else {
   echo "<li><a href='?p=".urlencode($rd)."'>$rd</a></li>";
  }
 }
}
echo "</ul>";
?>

Yes, this should all be in a recursive function so you can dig down to just about any level in your tree structure. However, this post is not about recursive programming; we’re mostly interested in showing you what our API/SDK can do.

For instance, you can retrieve the slides in a selected folder and generate a link to them for visualization:

 // now handle the slides in the subfolder
 echo "<ul>";
 foreach (Core::getSlides($subdir) as $slide) {
  $slideParts = explode("/", $slide);
  echo "<li>".end($slideParts)."</li>";
 }
 echo "</ul>";

Introducing the UI class

We can do better than our last example. Providing a link to PMA.start is easy enough, but once you get to that level you’ve lost control over the rest of your layout. What if you make a website where you want to place slides in certain predefined locations and placeholders?

That’s where the UI class comes in. Currently, you can use it to either embed slide viewports, or thumbnail galleries in your own website.

Here’s how you can include an arbitrary slide:

<?php
// load library
include_once "lib_pathomation.php";

Use Pathomation\UI;
Use Pathomation\Core;

// setup parameters
UI::$_pma_ui_javascript_path = UI::$_pma_start_ui_javascript_path;
$session = Core::connect();

// pick a slide to embed in your page
$slides = Core::getSlides("C:/my_slides/");
$slide = $slides[0];

// actually embed slide
UI::embedSlideBySessionID(Core::$_pma_pmacoreliteURL, $slide, $session);
?>

The embedSlideBySessionID() method return a string that serves as an identifier for the generated viewport. Use this identifier to subsequently define a style for your viewport:

<?php
// actually embed slide
$viewport = UI::embedSlideBySessionID(Core::$_pma_pmacoreliteURL, $slide, $session);
?>
<style type="text/css">
/* viewport style; as defined by PHP */
#<?php echo $viewport; ?> {
 width: 500px;
 height: 500px;
 border: 2px dashed green;
}
</style>

The result is now a 500 x 500 fixed square (with a dashed border) that doesn’t change as your modify the browser window:

You can have as many viewports on a single page as you want; each is automatically assigned a new ID, and so you can set separate layout for each one.

Working with galleries

What if you have a collection of slides and you want to present an overview of these (browsing through slide filenames is tiring and confusing). You could already combine the code we have in this post so far and request thumbnails for a list of a slides found in a directory, subsequently rendering selected slides in a viewport.

But what if you have 50 slides in the folder? Do you really want to handle the scrolling, just-in-time rendering of initially hidden thumbnails etc.?

Pretty early on in our Pathomation career we found ourselves facing the same problems. We re-invented our own wheel a couple of times, after which we figured it was round enough to encapsulate in a piece of re-usable code.

You guessed it: the UI class provides a way to generate galleries, too. At its simplest implementation, only one line of code is needed (setup not included):

<?php
include_once "lib_pathomation.php";

Use Pathomation\UI;
Use Pathomation\Core;

$session = Core::connect();
echo "<p>".$session."</p>\n";

UI::$_pma_ui_javascript_path = UI::$_pma_start_ui_javascript_path;

UI::embedGalleryBySessionID(Core::$_pma_pmacoreliteURL, "C:/my_slides", $session);
?>

You’ll notice that you can select slides in the gallery, but they’re not particularly reactive. For that, you’ll need to instruct PMA.UI to provide a viewport as well. When a slide is clicked in the gallery, the slide is then shown in the viewport:

UI::linkGalleryToViewport($gallery, "viewer");

 

The default orientation of a gallery is “horizontal”, but you can set it to a vertical layout, too:

$gallery = UI::embedGalleryBySessionID(Core::$_pma_pmacoreliteURL, "C:/my_slides", $session, array("mode" => "vertical"));

In which you can build something that looks like this:

 

Try it!

You can build pretty complicated interfaces already this way. One possibly scheme e.g. is where you offer end-users the possibility to compare slides. You need two galleries and two viewports, and that goes like this:

<table width="100%">
<tr>
<th width="50%">Slide 1</th>
<th width="50%">Slide 2</th>
</tr>
<tr>
<td width="50%" valign="top">
 <?php
 $galLeft = UI::embedGalleryBySessionID(Core::$_pma_pmacoreliteURL, "C:/my_slides", $session);
 ?>
</td>
<td width="50%" valign="top">
 <?php
 $galRight = UI::embedGalleryBySessionID(Core::$_pma_pmacoreliteURL, "C:/my_slides", $session);
 ?>
</td>
</tr>
<tr>
<td width="50%" valign="top">
 <?php
 UI::linkGalleryToViewport($galLeft, "viewerLeft");
 ?>
</td>
<td width="50%" valign="top">
 <?php
 UI::linkGalleryToViewport($galRight, "viewerRight");
 ?>
</td>
</tr>
</table>

Under the hood

Everything PHP spits out is HTML, JavaScript, or CSS. Essentially, the only means of communication PHP has is to provide instructions to the webrowser.

The PHP SDK demonstrated in this post do the same thing: simple single-line instructions in PHP are translated in whole parts of JavaScript code. The UI class takes care of loading all the required libraries, and makes sure housekeeping is taken care of in case of multiple viewports, galleries, etc.

You can see this for yourself by looking at the source-code of your PHP page, after it loads in the webbrowser.

The JavaScript framework that we wrote ourselves for browser-based WSI visualization is called PMA.UI. It comes with its own set of tutorials, and there is much more you can do with PMA.UI than through the PHP SDK alone.

However, we found in practice that there is much demand for cursive embedding of WSI content in any number of places on a website or corporate intranet. In my cases, a gallery browser and a “live” slide viewport are sufficient. In those scenarios, the PHP SDK can definitely come in handy and offer a reduced learning curve.

The SDK should help you get started . By studying the interaction between the PHP-code and the generated JavaScript, you can eventually master the PMA.UI library as well and interact with it directly.

By all means, do send us screenshots of your concoctions (let us know when you need help from your friendly neighborhood pathologists, too)! Perhaps we can have a veritable “wall of WSI fame” up one day.

The right person for the right job

Emerging opportunities

Digital pathology is on the rise, much in part of a 2017 FDA approval. With expanding activities comes the need to hire the right people for the right job.

Both manufacturers and customers have been putting out job ads at an increasing rate to keep up with the rapid move to digitization. But as I go over these postings, I often find unrealistic expectations on the customer side.

The digital pathology customer

What does a digital pathology customer look like? As it minimum, we’re talking about organizations that have decided to adopt whole slide imaging in at least some of their workflow.

Read that last sentence again. We don’t think you’re a digital pathology adapter if you bought a scanner. Then you bought a scanner. But there’s more to it than that: the organization that purchases the scanner must make the conscious decision of wanting to bring it into their regular workflow, and possibly modify their procedures where needed.

On that note, we think there are quite possibly people out there that are already doing digital pathology without realizing it, or at least without actually having the hardware to do whole slide imaging.

Many conventional microscopes can and have been outfitted with digital recording devices. If you have a workflow at your lab that is inherent to and optimized for these digital material produced by these, you are doing digital pathology. PMA.start probably supports your file types already.

Who to hire?

In many places around the world, the realization now sets in that digital pathology in indeed more than just getting the slide scanner. You need somebody to run the operation (and not just the scanner). You need somebody who can do internal PR and evangelization.

The person should have great communication skills, as they’ll need to interact with IT, as well as various types of end-users. Reporting to management or even the C-suite may bed required. You’ll need to communicate with various layers in the hierarchy, too. Say that you’re at a university: chances are that a PI doesn’t know or care about whole slide imaging, but that a number of students in the lab would indeed benefit from the technology. This requires certain diplomatic skills at time.

Let’s call the person that can do the above job the “digital pathology manager”.

There’s no well established job profile for a digital pathology manager yet. Yet I held this position myself for three years at the Vrije Universiteit Brussel. To be perfectly honest: this wasn’t a job title given to me. I picked it myself as it seemed fitting.

In retrospect, I think it was. The university had bought a scanner, and was looking for use cases and scenarios to fit it into. They were ready to embark on the digital pathology journey!

Responsibilities of the digital pathology manager

So here’s a list of tasks and responsibilities that I think fall under the responsibility of a digital pathology manager, and that may be included in a job ad:

  • Support digital pathology users
    • Teach techniques
    • Think about “best pracices”
  • Reporting
    • user trends
    • rate of adaptation
  • Maintain internal portal websites
    • Be vigilant about mobile digital pathology
      • It’s not because you CAN that you SHOULD
  • Support educational activities
    • Histology / pathology / microscopy
    • Digital pathology as a training and certification tool
  • Establish collaborations with external and international partners
  • Present the home institute or organization as a center of competence in digital pathology
    • representation at digital pathology conferences
    • lecture at conferences and other institutes (invited talks)
    • be an ambassador for digital pathology at events that are not necessarily DP-focused
      • like bioinformatics, image processing, or pathology)
    • supervise the publication of non-scientific content about digital pathology
      • e.g. through a blog or industry publication
    • keep an eye out for the possibility to (co)author scientific publications
    • organize workshops about digital pathology

I should point out that my function was at a public university. Depending on whether you work at a research institute, a company, or a hospital, accents on different aspect of the job can be expected to vary.

Finding your own

Why did I actually feel the need to post this?

I think that many job ads out there today don’t reflect what an organization actually needs to establish a successful digital pathology program. Many job ads ask for combined MD/PhD degrees, with experience in research as well as the clinic, and possibly have experience with digital pathology already.

Sure, you’ll need some background, and probably a substantial one. But do you really need two doctorate-level degrees? Why not throw in an MBA as well?

I find many of these ads go look for the proverbial five-legged sheep, and are therefore unlikely to find these.

Instead, focus on what you actually want to accomplish. Do you have a concrete scenario in mind already? Or are you still at an exploration phase? Do you have your (internal) customers lining up? Or are most people unaware that you have this technology now (or do they just not care)?

Digital pathology is still new and you will not find people that come from targeted degree programs.  I think the hiring challenge for digital pathology customers should start from making a list of responsibilities. Search and you will find.