Noninvasive Oral Hyperspectral Imaging–Driven Digital Diagnosis of Heart Failure With Preserved Ejection Fraction: Model Development and Validation Study - Xiaomeng Yang; Zeyan Li; Lei Lei; Xiaoyu Shi; Dingming Zhang; Fei Zhou; Wenjing Li; Tianyou Xu; Xinyu Liu; Songyun Wang; Quan Yuan; Jian Yang; et al. (Journal of Medical Internet Research)