SPIE Conference Part 1: Extended Depth of Field Imaging Holds Promise for Accelerating Digital Pathology Image Analysis

by Christos Evangelou, MSc, PhD – Medical Writer and Editor

SAN DIEGO, California – In a new study, researchers at the University of Texas at Dallas, USA, developed a new extended depth of field (EDOF) method for mosaic hyperspectral images. The team evaluated the performance of two fast EDOF methods and found that band-based EDOF provided the best quality reconstruction, highest speed, and lowest number of deconvolutions. The researchers believe that EDOF holds promise for accelerating whole-slide imaging (WSI). The study findings were presented at SPIE Medical Imaging 2023, which took place in San Diego on February 19–23.

Hyperspectral imaging (HSI) is a contact-free imaging modality that captures data in both the spectral and spatial domains. A major issue with HSI and WSI is that slides can be uneven in thickness, causing multiple focal planes to exist in a single slide. “These changes in focus can cause some regions to appear in focus, while others can appear out of focus,” explained Armand Rathgeb, research assistant at the University of Texas at Dallas. “EDOF can help improve focus in images at all points in the plane,” he added.

In this study, researchers aimed to develop a computationally efficient and rapid EDOF imaging method that would allow for the reconstruction of fully focused hyperspectral images and that could be easily integrated into WSI systems. To this end, they used an imaging system consisting of an inverted brightfield microscope, a hyperspectral camera, and custom auto-capture software to image 271 stacks of mosaicked hyperspectral histology slides from patients with head and neck cancer. Each image stack consisted of 14 mosaic hyperspectral frames, yielding a total of 3794 images.

The researchers compared the performance of the different EDOF methods and found that band-based EDOF outperformed both the growth-based and patch-based EDOF methods. Band-based EDOF was 12.2 times faster than the growth-based EDOF method and 5.17 times faster than the patch-based method.

Additionally, the team used the Brenner function to quantitatively measure the focus quality of the images generated using the three different EDOF reconstruction methods. Again, band-based EDOF reconstruction outperformed the growth-based and parch-based EDOF methods, although the differences in quality were less pronounced than the differences in speed.

“Although qualitative scores did not differ immensely among the three methods, patch-based reconstruction showed a variety of errors and blurry spots,” Rathgeb explained.

Given the high-quality reconstructions, speed, and computational efficiency, our algorithm promises to speed up WSI using hyperspectral cameras,” Rathgeb noted. “In the future, it might be useful to consider the use of deep learning methods to create higher quality reconstructions, as well as to adapt this method for use with other cameras,” he added.

SPIE Medical Imaging 2023

SPIE Medical Imaging 2023 started on Sunday, 19 February with conference presentations kicking off on the next day. The meeting in San Diego offered a great opportunity to hear the latest advances in image processing, physics, computer-aided diagnosis, perception, image-guided procedures, biomedical applications, ultrasound, informatics, radiology, and digital and computational pathology.

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