Correlating optical coherence tomography images with dose distribution in late oral radiation toxicity patients

Abstract

Abstract Background and objective: Late oral radiation toxicity occurs in about half of the patients who undergo head-and-neck radiotherapy, reducing the quality of life drastically. The total delivered radiation dose has been shown to be one of the predictors of these late complications. To demonstrate this, the studies carried out so far have used either visual observation together with symptom-based scoring systems or histology to evaluate the tissue response. However, the former lacks imaging information on tissue subsurface and the latter is invasive and exposes the patients to additional risks. Therefore, there is a need for a non-hazardous, non-invasive subsurface monitoring tool that can provide more objective information on dose-dependent response of normal oral tissue to radiation. Materials and methods: To address this unmet clinical need, optical coherence tomography (OCT) was used. A clinical study was conducted on 14 late oral radiation toxicity patients and 5 age-matched healthy volunteers. OCT structural images were acquired from different oral regions in both cohorts and were then de-speckled in order to provide a better visualization of the subsurface layers and features. The alterations in patients’ de-speckled OCT images compared to the healthy cohort are reviewed, and potential correlations between the total dose to specific regions and the abnormal features observed in the OCT images of the same sites are discussed. Results: OCT images were acquired from 32 sites in 14 patients, 15 of these sites belonged to the regions which received >50 Gy radiation dose and the rest to the region which was irradiated to <50 Gy. The de-speckled OCT images from the former group showed major differences, such as total layer disruption, compared to the images of healthy oral tissue. The de-speckled OCT images from all but one of the regions which received <50 Gy showed normal features and layer definition compared to healthy oral OCT images. Same results were observed in an intra-patient comparison of the ipsilateral (dose >70 Gy) and contralateral (dose <25 Gy) soft palate of one of the patients, suggesting the results are independent of anatomical differences between individuals. Conclusion: This preliminary clinical study showed the ability of OCT to differentiate subsurface features in the oral regions that received high radiation dose (>50 Gy) compared to healthy oral tissue. These results can be used to design a prospective study to monitor oral subsurface changes periodically (e.g., every 6 months) following radiotherapy, to further understand the mechanism of late radiation toxicity and its relation to dose.