Tissue harmonic imaging (THI) uses not the fundamental transmitted frequency but the harmonic frequencies generated as the ultrasound beam distorts while propagating through tissue. Because harmonics build up along the beam path rather than at the transducer surface, near-field artifacts and side lobe artifacts are greatly reduced. Harmonic imaging improves contrast resolution, reduces clutter, and enhances visualization of fluid–tissue interfaces, making it particularly valuable in difficult-to-image patients.