Spectroscopic Photoacoustic Imaging for Accessing Cervical Tissue Composition in Human Cervical Biopsies

The cervix plays a central role in pregnancy and delivery. A short cervix (
$\leqslant 25\ \text{mm}$
), measured by ultrasound (US) imaging, at gestational ages between 22 to 24 weeks indicates a higher risk for preterm birth (PTB). Our previous publications had determined that a spectroscopic photoacoustic (sPA) imaging method in the near-infrared range has the potential to quantify the cervical remodeling as the collagen to water ratio (CWR) changes in murine cervices. Herein, we present the continuous study of the sPA method to identify un-ripened and ripened cervices in humans. A cross-sectional study was performed in comprised cervical biopsies obtained at the time of hysterectomy (
$\mathrm{n}=8$
) and at the scheduled cesarean delivery in pregnant women at term who were not in labor (
$\mathrm{n}=8$
). The results indicated that the average sPA-CWR in the cervical tissue from non-pregnant women is 55.5%, with a standard deviation (SD) of 20.3%. On the contrary, pregnant women have an average sPA-CWR of 18.7%, with an SD of 7.5%. The statistical analysis shows a significant difference between those two groups with a p-value less than 0.001. Furthermore, a sub-group analysis between pregnant and non-pregnant women of age less than or equal to 41 years old also showed a significant difference in the sPA-CWR with a p-value less than 0.001, mean 46.3%, SD 23.1%. Through histological analysis, the pregnant women group had lower collagen content. Therefore, the sPA method shows promise to become a new potential diagnostic indicator for evaluating cervical tissue composition and its association with the risk of cervical abnormalities leading to preterm birth.