Revolutionary Applications: Slide-Free Microscopy Part 2
In Part 1 of this series, we introduced the cutting-edge technology called “slide-free microscopy” (“direct-to-digital” microscopy). We touched on the challenges facing the traditional histology workflow and highlighted how this entire industry is overdue for innovation. We also showed how slide-free microscopy could eliminate the archaic, assembly line of expensive equipment and technicians needed to create glass slides. In short, this approach has the potential to completely transform how we generate the images we send to pathologists.
Oh, and if you’re not super into nerdy science, keep in mind that this is still a $30 billion market—so if you’re an investor or a business leader in either human or veterinary healthcare, you’ll want to pay attention.
Most people have no idea this technology is as mature as it is, but over the past 20 years, researchers have been working on a handful of optical imaging methods that could make all of this very real. In this newsletter, we discuss the potential applications for slide-free microscopy. In Part 3 we showcase the companies making this a reality.
But first, I realize you may be having a hard time envisioning what slide free microscopy is from a workflow perspective. We’ll get into details of each company’s workflow in Part 3, but for now we can boil it all down to this depiction below of a simplified and generic workflow that involves taking surgical tissue, processing/staining it, and then placing it into a device for imaging. For all of these points in the workflow, time and complexity vary from technique to technique. The end goal is the same: Generate a digital histopathology image from tissue without having to create glass slides.
A simplified depiction of a generic slide free microscopy workflow
Critical Considerations
When considering the technological approaches to slide-free microscopy, there are some key features for us to discuss. Here are the most important:
- Image quality: Some approaches generate images nearly indistinguishable from traditional H&E, while others have lower resolution more akin to frozen sections. Because image quality is a huge factor in determining how the technology can be used, it’s a critical one to consider.
- 2D vs. 3d: Pathologists have traditionally only evaluated 2 dimensional images, but some of these technologies give us incredible 3D images enabling spatial analysis.
- Workflow complexity and time: Generally, the simpler and faster the workflow, the more likely it’s going to replace standard laboratory processes. However, longer workflows may be acceptable if the payoff is more robust data, particularly for research applications.
- Imaging time: The images may be of the highest caliber, and the workflow may be simple, but if the imaging is too slow it’s a bottleneck in the workflow for clinical diagnostics. Again, tolerable for things like research if the payoff is better, but will limit clinical adoption.
- Equipment size and cost: These approaches have equipment that ranges from being surprisingly cheap ($<10k) to very expensive ($250k+). Cost will factor into whether replacing the traditional workflow is worth it and is closely tied to imaging throughput capabilities. Additionally, size becomes important if the instrument is intended for point-of-care use.
- Consumable cost: The price and type of consumables, especially whether they are proprietary or generic, will affect per-case expense and how likely the given technology will be adopted for specific purposes.
A 3 dimensional slide free microscopy image generated using Hybrid Open-Top Light Sheet Microscopy. Image courtesy of Alpenglow Biosciences
A slide free microscopy image generated by using automated multiphoton microscopy. Image courtesy of Applikate Technologies
Applications for Slide-Free Microscopy
Let’s start by mapping out how slide-free microscopy might be used. Once you unleash a new technology on an industry, it’s tough to guess precisely what it might do or what new tools will emerge. (Looking at you, ChatGPT!) But for the moment, here’s how I’m thinking about slide-free microscopy:
- Histology Lab Replacement
One obvious use is to overhaul the entire histology process and replace today’s expensive equipment and workflows. We’ve covered this in Part 1 already. It’s a no-brainer that labs would want to streamline their workflow when the right tech comes along. Ideally, you’d see a full replacement for every tissue type, but that could happen in stages as regulatory approvals come through, beginning with just one or two of the high volume tissue types. If that’s the goal, though, certain requirements have to be met:
Requirements
-
-
- High Image Quality: The resolution needs to meet or beat what we get with traditional H&E, or pathologists simply won’t adopt it. And, these images either have to resemble H&E or be easily convertible to that format. Some approaches produce incredible 3D or color-enhanced images that highlight structures in new ways, but the farther away from traditional H&E the images are the longer it’s going to take to gain traction—at least in the short term.
- Regulatory Approval, Maybe….. This is an obvious hurdle in the minds of readers from the human healthcare industry and is critical before this technology is used for clinical diagnostics. However, the exception here is that there is no regulatory body of veterinary diagnostics. It’s still the wild wild west over here. Any company with a solid product that needs more data or revenue while awaiting regulatory approval should look at bringing it to veterinary diagnostics. This is not to say that it’s easily done. It’s not, and there are unique challenges in animal health. That’s for another newsletter.
- Workflow: Simple, Efficient, Predictable: Traditional histology is predictable but hardly simple or efficient. Any new system has to knock it out of the park on all three counts to get people to change old habits.
- High Throughput: Even though current histology workflows are inefficient, they can handle a relatively large volume in a well-run lab. So a replacement technology has to keep up at scale. Tissue fixation requirements, staining/processing time, scan time, and file size/data transfer all factor in. A 30-minute scan might yield stunning images, but if the lab has a throughput of hundreds or thousands of tissues a day, that’s not gonna fly.
- Other Considerations: Special stains? Decalcification? Pigments like melanin and hemosiderin? Long-term tissue storage? Those might sound like small details, but they matter if we’re trying to truly replace the old system. Each of the technologies tackle these in unique ways which we will discuss later. For now I’ll just say that I’m optimistic there are solutions to all of these.
-
-
Point-of-Care Histopathology
I’ve long been envious of my radiology colleagues who receive images directly from a hospital and zip a report back in under two hours. Something similar is happening in vet med with point of care cytology scanners in hospitals: full cytology results come back in a matter of hours. No laboratory middle man required for radiology or cytology. Meanwhile, my anatomic pathology colleagues have to wait days for biopsy tissue to be fixed, shipped across the country, turned into glass slides by a lab, scanned to digital, then finally sent to the pathologist—usually 3–5 days or more from when the lab first receives the sample.
We’ve dreamed about the day when technology would allow doctors to image tissue right there in the hospital—maybe even while the patient is still on the table—and let us weigh in on the diagnosis or margin analysis in just minutes or hours. That exists in human medicine using frozen sections, but the quality of the slide and subsequent image generated is below that of standard histology, leaving room for an innovative technology to improve on the current frozen section application. Frozen sections have never been adopted in vet med due to the equipment costs, training requirements, and personnel needed. What if we had an affordable and simple point of care histopathology option for human and veterinary surgical suites?
Requirements
- Small Footprint: Clinics often have limited space, and every device is fighting for precious real estate.
- Rapid, Simple Workflow: It must require minimal training and have a low chance of operator error.
- Seamless Integration with Pathology: We need a frictionless way to send large images (often 2+ GB) to pathologists and get reports back. If intra-operative results are required, the network infrastructure has to be reliable and robust enough to handle that load and minimize anesthesia time.
- Instrument Cost: In vet clinics especially, cost is critical, and everyone’s mindful of ROI. A lower-cost device has a big advantage if we’re thinking about widespread point-of-care adoption.
Key Question: Do hospitals want this? For any point of care applications in vet med, we have to figure out if hospitals will justify the extra tech time to get faster results, or will they be content sending out and getting results a few days later. Many factors come into play here, but for point-of-care histopathology we need to consider the extra tech time and training required for grossing tissue, staining, and imaging. Quality technicians are already in short supply. Will hospitals find it worthwhile to invest in staff training and time at the bench to get faster biopsy reports in this innovative way, or will they opt for keeping the status quo and getting reports back in a few days? We haven’t really market-tested these questions yet and I think the jury is still out.
Research
The ability to do slide-free imaging also opens up interesting possibilities for research. At the very least, it simplifies in-house histology for a research group and could remove their dependence on an external lab. On top of that, some of these imaging approaches allow for multiple Z-axis scans or even 3D spatial analysis, with options to stain for certain immunomarkers. Add on machine learning to all this new data, and we’re looking at fascinating avenues for scientific discovery and a deeper understanding of disease processes.
Optical Imaging Approaches to Slide-Free Microscopy
A handful of optical imaging techniques for slide free microscopy have been explored over the past two decades, with much literature on the subject. The common approaches are listed below, with many variations of each existing:
- Confocal microscopy
- Multiphoton microscopy
- Raman microscopy
- Microscopy with UV Surface Excitation (MUSE)
- Fluorescence-Imitating Brightfield Imaging (FIBI)
- Structured Illumination Microscopy
- Photoacoustic microscopy
- Full-field Optical Coherence Tomography
- Light Sheet Fluorescence Microscopy
Each technique brings its own pros/cons/challenges for the applications we discussed above. When thinking about the future and the techniques competing in this space, realize this doesn’t have to be a zero sum game. The future pathology lab may be one that utilizes more than one of these techniques, or have devices that incorporate one or more techniques depending on the imaging need. If you’d like to dive into more detail on these approaches, check out the review articles in the references below.
The Companies Bringing Slide Free Microscopy to Market
Next up, in Part 3 of this series, I’m shining the spotlight on four companies I’m especially excited about:
Make sure you read Part 3 to get the deep dive on each of these companies!
Disclaimer
I am not currently employed by or affiliated with any company developing slide-free microscopy technology. However, I previously served as a scientific advisor for Smart Health Dx and hold equity in that company. My opinions in this article are my own and are based on my experience in pathology and my independent analysis of the field. This newsletter is intended for informational purposes only and does not constitute financial, medical, or investment advice.
References:
Tanishq Mathew Abraham, Richard Levenson, Current Landscape of Advanced Imaging Tools for Pathology Diagnostics, Modern Pathology, Volume 37, Issue 4, 2024, 100443, ISSN 0893-3952,https://doi.org/10.1016/j.modpat.2024.100443.
Yehe Liu, Richard M. Levenson, Michael W. Jenkins, Slide Over: Advances in Slide-Free Optical Microscopy as Drivers of Diagnostic Pathology,The American Journal of Pathology,Volume 192, Issue 2,2022,Pages 180-194,ISSN 0002-9440, https://doi.org/10.1016/j.ajpath.2021.10.010.
