{'fraction_non_alphanumeric': 0.03167746580273578, 'fraction_numerical': 0.018718502519798418, 'mean_word_length': 5.043478260869565, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
High-Frequency Ultrasound for Long-term Safety Assessment of Poly-L-Lactic Acid Facial Filler

BACKGROUND Injectable poly-l-lactic acid (PLLA) is a new type of biodegradable dermal filler that has been utilized for soft tissue filling. However, there is no convenient and reliable method to assess the long-term safety of PLLA filler. OBJECTIVE To assess the long-term safety of PLLA injection into nasolabial folds by high-frequency ultrasound and to select the ultrasonic probes with the most appropriate frequency. MATERIALS AND METHODS After a 30-month PLLA injection into the deep dermis of the nasolabial fold, subjects were examined by high-frequency ultrasound with the 20 MHz and 50 MHz probes. RESULTS Twenty subjects with nasolabial fold contour deficiency were enrolled in this study. After a 30-month PLLA injection in nasolabial folds, PLLA degraded entirely in 16 subjects (16/20, 80%), and abnormal echo in the skin was observed in 4 subjects (4/20, 20%) caused by undegraded PLLA microparticles, PLLA microparticles deposition, fibrous nodules, and granuloma. The 20-MHz probe is more appropriate than the 50-MHz probe for evaluating the adverse effects of PLLA injection. CONCLUSION High-frequency ultrasound is a rapid, reliable, and noninvasive method to monitor the degradation condition of PLLA and the formation of papules and nodules associated with PLLA injection.