Quantitative characterization of radiofrequency ablation lesions in tissue using optical coherence tomography

Abstract

Radiofrequency (RF) ablation is a widely used therapeutic intervention in the management of many cancers including breast and liver cancers. While optimum delivery of RF energy can be monitored through real-time temperature mapping from MR imaging, it is possible that microscopic foci of malignant tissue may be left untreated. Such microscopic tissue may be beyond the resolution limit of MRI and may result in sub-optimal treatment efficacy which may lead to cancer recurrence. Thus, for optimal treatment it is beneficial to incorporate higher-resolution techniques such as optical coherence tomography (OCT) that can surpass the resolution afforded by MRI into the micron range in situ and can provide histopathology level information on tissue in vivo. In this preliminary study, in order to test the feasibility of this approach, we characterized tissue properties such as the scattering coefficient (μs), in non-ablated and ablated bovine skeletal muscle ex vivo. The estimated μs of the non-ablated muscle region was 1.9641 mm-1 while the μs of the ablated region was 5.8998 mm-1 (p<0.001). The OCT image of ablated tissue shows higher backscattering and reduced penetration depth from higher attenuation. Significant histological differences in muscle fiber size and interstitial area were observed between the ablated and non-ablated tissue with the ablated tissue showing 31% less packing fraction (defined as the muscle fiber area divided by the total histology area) explaining the increased backscattered light that tends to augment the index mismatch for the incident light. These preliminary data demonstrate the characterization of morphological tissue properties that are altered by RF energy during ablation procedures and the feasibility of quantitatively assessing ablation lesions using OCT. © 2010 Springer-Verlag.