Dual-mode endoscope offers unprecedented insights into uterine health
Ultrasound-OCT probe could help study and diagnose a common cause of infertility
Date:
April 4, 2022
Source:
Optica
Summary:
A new endoscope design that combines ultrasound with optical
coherence tomography can assess the structural features of the
endometrium with unprecedented detail. This dual-mode endoscope
could help doctors diagnose infertility problems that are related
to endometrial receptivity with greater accuracy than current
imaging technologies.
FULL STORY ========================================================================== Researchers have developed a new endoscope that combines ultrasound with optical coherence tomography (OCT) to assess structural features of the
lining of the uterus, called the endometrium, in unprecedented detail. The
new probe could one day 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.
========================================================================== "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 research
team leader Xiaojing Gong from the Shenzhen Institutes of Advanced
Technology of the Chinese Academy of Sciences. "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." In the Optica Publishing Group journal Biomedical Optics
Express, the researchers report the ability for their dual-mode endoscope
to differentiate between healthy and injured endometrial tissue in rabbit models based on both surface features and depth information. It is the
first in vivo demonstration of intrauterine endoscopic imaging in small animals, with a probe measuring just 1.2 mm across.
The endometrium plays a critical role in the ability for a blastocyst to implant in a uterus and grow into a healthy fetus. Failure to implant
is recognized as a key bottleneck in the reproductive process, with
impaired endometrial receptivity accounting for about two-thirds of implantation failures.
By providing detailed structural information about the endometrium,
the probe could offer a less invasive way to determine if endometrial
problems are causing infertility, which affects about 10-20% of women worldwide, as well as help to diagnose other uterine health problems.
"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. "It also has the potential to detect diseases in the uterus, such as endometrial cancer and uterine fibroids." Creating a better probe
==========================================================================
The current gold standard method for assessing endometrial receptivity
is through biopsies, which require surgically removing and analyzing
a small tissue sample. Endoscopic imaging is a less invasive method,
but current endoscopes can only identify larger defects in the uterus
such as anatomical malformations or polyps, not assess the structure of
the endometrium. A vaginal ultrasound can provide information about the thickness of the endometrium and other structural features, but lacks
the resolution and contrast needed to comprehensively assess endometrial receptivity.
OCT is an imaging technique that uses relatively long wavelength light (commonly known as near infrared light) to produce high-resolution
images from within scattering media. It has been adapted for diagnostic
tools in several medical fields including ophthalmology, cardiology
and dermatology. Previous studies have shown OCT imaging can be used to identify structural features of the endometrium that are associated with implantation failures.
For the new study, researchers improved upon a prototype they had
previously developed to combine OCT and ultrasound imaging in a
single probe. The OCT modality provides detailed information about
the superficial endometrium including its surface information, while
ultrasound provides insights about its full thickness. Since multiple
features of the endometrium affect implantation success, combining
these imaging modalities provides a more accurate picture of endometrial receptivity than either mode individually.
The catheter is designed to pass through the cervix, enter the uterine
cavity and inject water to facilitate high-resolution imaging. A series
of tiny custom-designed optical and ultrasonic components are arranged
within the catheter to achieve both ultrasound and OCT mode. The improved
probe also uses a single-mode fiber, which offers 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 full-field of
view once it is inside the uterus.
"The imaging catheter can realize the rotation and retraction scanning
through the rotation-retraction unit at the rear end, and obtain the three-dimensional ultrasound-OCT image of the uterus," said Gong.
==========================================================================
A powerful combination To test the endoscope, the researchers used it
to image the uterine lining of four anesthetized rabbits. Some of the
rabbits were healthy while others had undergone a procedure to wash the endometrium with ethanol for different lengths of time, damaging the
tissue to varying degrees.
The researchers quantified features of the endometrium including its
thickness, distribution and surface roughness separately in ultrasonic
and OCT modalities.
The OCT images showed that healthy endometrial tissues had a smoother
and more continuous surface, while damaged tissues were more rough. In ultrasound images, the endometrium was found to be thicker in healthy
tissues and thinner in areas that had been damaged. While each modality provided valuable information on its own, it wasn't until the researchers combined the information from each that they were able to comprehensively
and accurately evaluate the degree of tissue injury.
"These results demonstrated the importance of bimodality in the detection
of the extent of endometrial damage," said Gong. "The variance is too
large, and it is difficult to distinguish the degree of injury through
a single mode of information. However, combining the information of the
two modalities can differentiate the degree of damage." The probe also provided echo patterns that were similar to what can be obtained with
vaginal ultrasound but with better resolution. In addition, the images
revealed physical features such as polyp-like formations as small as 200 microns, demonstrating the probe's ability to discern tiny lesions that
could affect endometrial health.
The researchers plan to add a photoacoustic mode to increase the probe's ability to observe blood flow and information about the vascular networks
in the uterine lining. In addition, they are working to improve the size, resolution and imaging range of the imaging catheter to make it more
practical for clinical use in humans.
========================================================================== Story Source: Materials provided by Optica. Note: Content may be edited
for style and length.
========================================================================== Journal Reference:
1. Jinke Zhang, Meng Du, JInghui Fang, Shengmiao Lv, Wenjin Lou,
Zhihua Xie,
Zhiyi Chen, Xiaojing Gong. In vivo evaluation of endometrium through
dual-modality intrauterine endoscopy. Biomedical Optics Express,
2022; 13 (5): 2554 DOI: 10.1364/BOE.453191 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/04/220404120522.htm
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