This is a prospective, single-center, open-label clinical study designed to evaluate the safety, biodistribution, radiation dosimetry, and diagnostic performance of \[68Ga\]Ga-FFD PET imaging. The study consists of two cohorts: healthy volunteers and adult patients with histologically or clinically confirmed malignant solid tumors. Healthy volunteers will undergo serial PET imaging to evaluate tracer biodistribution, pharmacokinetics, and radiation dosimetry. Patients will undergo \[68Ga\]Ga-FFD PET imaging in addition to standard-of-care \^18F-FDG PET imaging for assessment of lesion detection and diagnostic performance. Safety will be evaluated through adverse event monitoring, vital signs, laboratory tests, physical examinations, and electrocardiography. Diagnostic performance will be assessed using histopathology, conventional imaging, and clinical follow-up as the reference standard.