Ultrasound Imaging of the Facial Muscles and Relevance with Botulinum Toxin Injections: A Pictorial Essay and Narrative Review. - Wu, Wei-Ting; Chang, Ke-Vin; Chang, Hsiang-Chi; Chen, Lan-Rong; Kuan, Chen-Hsiang; Kao, Jung-Ting; Wei, Ling-Ying; Chen, Yunn-Jy; Han, Der-Sheng; Özçakar, Levent (Toxins, 2022)