Dual-mode endoscope gives clearer picture of uterine health

06 Apr 2022

Shenzen project combines OCT and ultrasound for live animal imaging.

Combining different modalities into one endoscopy instrument is a potentially valuable way to improve imaging performance in several biomedical applications.

A project at Shenzhen Institute of Advanced Technology (SIAT) has developed a custom-made dual-modality OCT/ultrasound endoscopic imaging system and used it for in vivo intrauterine imaging of rabbit uteri, said to be the first time such imaging has been achieved.

The new probe could ultimately help doctors diagnose infertility problems that are related to endometrial receptivity with greater accuracy than current imaging technologies, while reducing the need for invasive biopsies, according to the project.

As described in Biomedical Optics Express, the work builds on previous work at SIAT studying endoscopic examination of ex vivo animal tissues, studies which successfully generated imaging data but employed a catheter too large for in vivo studies.

The design was duly modified to use a single-mode optical fiber rather than the double cladding fiber previously employed, offering higher resolution and reduced noise for the OCT mode. In addition, the researchers used a metal coil to allow the probe to rotate for a 360-degree field of view once it is inside the uterus.

Combining OCT and ultrasound images is potentially valuable for gathering both surface and depth information simultaneously, and showing the uterine features associated with the evaluation of the endometrial injury.

"This tool combines the two techniques of ultrasound and OCT, allowing it to obtain more information and provide a more accurate assessment of endometrial status than traditional vaginal ultrasound," said Xiaojing Gong from SIAT. "It has the potential to be used for basic endometrial research and to further advance clinical assessment of endometrial receptivity and other endometrial-related diseases."

Distinguishing between healthy and damaged tissues

In trials comparing live healthy rabbits with others in which injury models had been created through application of ethanol, the endometrial changes between uteri with and without injury could be recognized in both the OCT and ultrasound modalities.

In OCT images, the surface details of the healthy uteri appeared as continuous and smooth, while the surface of ethanol-induced uteri became discontinuous, noted the project in its paper. In the ultrasound images, the thickness of ethanol-induced uteri was seen to be significantly degraded compared to the healthy uteri.

"The system can obtain the thickness information of the endometrium, the echo pattern of the endometrium and information about damage to the endometrial surface, which play an important role in the evaluation of endometrial receptivity," said Gong.

Further work will include adding a photoacoustic (PA) mode to the platform, exploiting the existing synergies between PA and ultrasound modalities. In 2021 a group at the University of Buffalo developed a dual-scan photoacoustic and ultrasonic imaging platform intended for breast cancer imaging.

The Shenzen team are also working to improve the size, resolution and imaging range of the imaging catheter to make it more practical for clinical use in humans.