PROJECT SUMMARY/ABSTRACT Successful treatment and management of oral mucosal lesions depend on a definitive, accurate, and timely diagnosis. Oral squamous cell carcinoma (OSCC) is very aggressive and tends to be diagnosed at late stages, leading to poor prognosis. Most OSCCs are preceded by oral potentially malignant disorders (OPMDs), which are a heterogeneous group of clinical oral lesions associated with a statistically increased risk of malignant transformation. The existing histopathological diagnosis for OPMD is subjective and unable to predict malignant transformation risk for individual OPMD cases, leading to challenges in precancerous oral lesion management. To fill the important medical gap in OPMD risk assessment, we propose an innovative Fourier Transform Infrared (FTIR) based multimodal imaging diagnostic platform, which integrates three complementary modalities: FTIR imaging for biochemical pattern recognition, histological imaging for morphological feature identification, and spatial transcriptomics for gene expression profiling. We will also employ cutting-edge machine learning (ML) and deep learning (DL) techniques for feature extraction and predictive model development. The central hypothesis of this proposal is that the integration of FTIR imaging with histological imaging and spatial transcriptomics techniques aided by ML/DL provides quantitative, objective, and accurate risk assessment for individual OPMDs. To test the hypothesis, we propose the following three specific aims: 1) Develop ML/DL models using the FTIR imaging technique for OPMD risk stratification, 2) Augment FTIR imaging with histological imaging to improve diagnostic efficiency and accuracy, 3) Apply spatial transcriptomics to profile gene expression and enhance biological interpretability of the OPMD diagnostic platform. The multimodal imaging-based diagnostic system can be easily integrated into the existing clinical diagnostic workflow for precise OPMD diagnosis, which together with effective OPMD management can lead to significantly improved patient outcomes and alleviate the global burden of oral cancer.