Ultraminiature SFDI System for Micro-Endoscopy Enables Early Diagnosis of GI Cancers

Gastrointestinal cancers (GCs) rank among the most prevalent cancer types and contribute to a significant proportion of cancer-related deaths globally. Early detection is key to reducing mortality rates associated with GCs, and endoscopic screening is effective in identifying potentially malignant tumors. For widespread application of screening programs, the imaging technology used must be cost-effective to produce and operate, while maintaining high accuracy to ensure low rates of missed diagnoses. To achieve this, researchers have been exploring various imaging techniques, including promising spatial frequency domain imaging (SFDI). SFDI involves projecting a repeating 2D light pattern onto the target area and analyzing the intensity of the reflected light patterns to deduce information about the tissue's optical properties, aiding in the detection of cancerous lesions. Despite its simplicity and affordability, the large size of current SFDI systems makes them too large to fit inside standard endoscopes, limiting their application in GC screening.

Now, researchers from University of Nottingham (Nottingham, UK) have developed a new SFDI device for gastrointestinal endoscopy, potentially expanding access to GC screening. Existing systems are unsuitable for regular endoscopic use in the gastrointestinal tract due to their reliance on expensive and large digital micromirror device-based projectors, low-quality pattern production using fiber bundles, or the inflexibility of rigid endoscopes. To address these challenges, the team developed an ultraminiature SFDI system using a custom optic fiber bundle as a projector. This bundle consists of seven individual optic fibers, each connectable to laser sources of varying wavelengths.

The system generates a 2D sinusoidal pattern on the target tissue by feeding a single laser wavelength into two different fibers, exploiting the interference phenomenon. By selecting different fiber pairs, the spatial characteristics of the pattern can be adjusted, and patterns with up to three wavelengths (like green, red, and blue) can be projected simultaneously. Coupled with an ultraminiature camera (1 mm x 1 mm), the researchers have assembled a prototype SFDI system just 3 mm in diameter. A custom algorithm further refines the system by tracking phase deviations in the projected patterns, enhancing the absorption and scattering profiles' clarity.

Tests with tissue phantoms mimicking healthy and cancerous tissues demonstrated the device's ability to clearly differentiate between the two types. The specificity and sensitivity rates for detecting squamous cell carcinoma were over 90%, comparable to current medical device standards. The researchers believe the system could be further miniaturized to a diameter of 1.5 mm, allowing for even less invasive endoscopic procedures. Its capacity for multi-wavelength imaging means it can capture optical information at various tissue depths, facilitating simultaneous analysis of multiple tissue layers. These findings highlight the potential of this novel imaging method for diagnostic purposes in gastrointestinal cancer detection.

“Our prototype shows promise as a cost-effective, quantitative imaging tool to detect variations in optical absorption and scattering as indicators of cancer,” said researcher Jane Crowley from University of Nottingham. “This work could form the basis of new devices suitable for cost-effective endoscopic deployment for screening of gastrointestinal cancers.”

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