Optimizing optical coherence tomography to detect occult spermatozoa in rat testis after induced non-obstructive azoospermia.

Significance: The ability to detect and localize sperm in the testes is crucial for the treatment of non-obstructive azoospermia (NOA), a condition where sperm retrieval is challenging due to the lack of visible sperm. Enhancing the accuracy and efficiency of sperm detection can significantly improve the outcomes of microdissection testicular sperm extraction (micro-TESE) procedures in NOA patients.

Aim: We aim to use optical coherence tomography (OCT) to detect the presence or absence of sperm in the imaged areas of the testes and to localize sperm-containing seminiferous tubules in a rat model of NOA.

Approach: Volumetric OCT scanning was performed on 180 distinct regions from the testes of two control and 15 busulfan-treated rats to mimic NOA. Following scanning, excised tubules were observed under a dissecting microscope with transillumination to confirm the presence of sperm. The OCT data were processed by first delineating the tubule lumen and then evaluating the calibrated intensity and attenuation coefficient within the lumen. These quantifications, along with outer tubule diameter, were evaluated to identify sperm by comparison with the results of the microscope examination.

Results: Our OCT results revealed a significant correlation between the presence of sperm and high attenuation coefficients in a rat model of NOA. The accuracy of sperm detection by OCT is 97.8% when compared with microscopic identification. In addition, OCT data were utilized for color-coded processing to automatically distinguish regions with a greater likelihood of the presence of sperm, which may assist surgeons in locating occult sperm in NOA patients.

Conclusions: By providing high-resolution, non-invasive, automatic capture, and color-coded images, OCT has the potential to significantly enhance the efficiency of identification of tubules with spermatozoa during micro-TESE.