Article ID: 2025-0105
Objectives: Despite the theoretical safety of high-intensity focused ultrasound in rejuvenation, adverse events continue to be reported. This study aimed to elucidate the mechanisms underlying adverse events associated with high-intensity focused ultrasound (HIFU) treatment.
Methods: A nationwide survey was conducted among 1,792 institutions in Japan utilizing HIFU, requesting them to complete a detailed questionnaire on adverse events. To identify patterns, we analyzed differences in adverse events by anatomical site and examined the characteristics of HIFU settings associated with these events. Numerical simulation was conducted to further validate our findings.
Results: A total of 139 valid cases were reported, involving 165 adverse events, as some cases involved multiple occurrences. The adverse events were categorized as follows: burns (n = 61), neuropathy (n = 49), purpura/subcutaneous hemorrhage (n = 19), hyperpigmentation (n = 10), wheals (n = 10), prolonged redness (n = 3), induration (n = 3, scars/hypertrophic scars (n = 2), edema/swelling (n = 2), floaters (n = 2), cataracts (n = 2), facial spasticity (n = 1), and salivary gland cysts (n = 1).
The most frequently implicated transducer depth for adverse events was 4.5 mm, accounting for 79 cases.
Conclusions: Transducers reaching deeper tissues must avoid areas that are anatomically at risk, such as nerves, vessels, and eyes. Heat generated in bone may damage adjacent nerves, while reflected and refracted ultrasound waves may refocus and cause burns. To minimize adverse events in HIFU therapy, it is critical to have a thorough understanding of HIFU characteristics, anatomy, and imaging-based evaluation of subcutaneous tissues.
