This is a single-center, single-arm, observational clinical study evaluating the efficacy and safety of low-dose liposomal amphotericin B (50 mg/day, intravenous, once daily) for the prevention of invasive fungal infections in adult patients (aged 18-75 years) with hematological malignancies who develop prolonged neutropenia (absolute neutrophil count ≤0.5×10\^9/L, expected to last \>7 days) and are at high risk for invasive fungal disease. Participants are those who, per the treating physician's routine clinical decision, have been initiated on liposomal amphotericin B prophylaxis at 50 mg/day due to intolerance or toxicity to other antifungal agents. The primary outcome is the incidence of proven or probable invasive fungal disease. Secondary outcomes include incidence of pneumonia, persistent unexplained fever \>4 days, use of additional systemic antifungal therapy, and adverse events. A total of 30 participants will be enrolled. Data will be collected at baseline, during treatment, and within 7 days after treatment completion.