Microscale characterization of prostate biopsies tissues using optical coherence elastography and second harmonic generation imaging

Photonics, especially optical coherence elastography (OCE) and second harmonic generation (SHG) imaging are novel high-resolution imaging modalities for characterisation of biological tissues. Following our preliminary experience, we hypothesized that OCE and SHG imaging would delineate the microstructure of prostate tissue and aid in distinguishing cancer from the normal benign prostatic tissue. Furthermore, these approaches may assist in characterisation of the grade of cancer, as well. In this study, we confirmed a high diagnostic accuracy of OCE and SGH imaging in the detection and characterisation of prostate cancer for a large set of biopsy tissues obtained from men suspected to have prostate cancer using transrectal ultrasound (TRUS). The two techniques and methods described here are complementary, one depicts the stiffness of tissues and the other illustrates the orientation of collagen structure around the cancerous lesions. The results showed that stiffness of cancer tissue was approximately 57.63% higher than that of benign tissue (Young’s modulus of 698.43 ± 125.29 kPa for cancerous tissue versus 443.07 ± 88.95 kPa for benign tissue with OCE. Using histology as a reference standard and 600kPa as a cut-off threshold, the data analysis showed sensitivity and specificity of 89.6% and 99.8% respectively. Corresponding positive and negative predictive values were 99.5% and 94.6% respectively. There was a significant difference noticed in terms of Young’s modulus for different Gleason scores estimated by OCE (p value < 0.05). For SHG, distinct patterns of collagen distribution were seen for different Gleason grade disease with computed quantification employing a ratio of anisotropic to isotropic (A: I ratio) and this correlated with disease aggressiveness.