Comparison of tissue harmonic imaging with conventional US in abdominal disease

Harmonic waves are generated from nonlinear distortion of an acoustic signal as an ultrasound wave insonates tissues in the body. These beams are integer multiples of a fundamental transmitted frequency. Potential advantages of harmonic imaging include improved axial resolution due to higher frequencies and better lateral resolution due to narrower beams. Decreased noise from side lobes improves signal-to-noise ratios and reduces artifacts. Deleterious effects of the body wall are also reduced. The authors prospectively studied ultrasonographic (US) findings in 100 adult patients with 202 abdominal lesions by comparing harmonic US images with conventional US images. The results were subjected to statistical analysis. Harmonic imaging was superior to conventional US in regard to lesion visibility and diagnostic confidence. Harmonic imaging was particularly useful for depicting cystic lesions and those containing echogenic tissues such as fat, calcium, or air. In patients with a body mass index of 30 or more, harmonic imaging was clearly better for lesion visibility and confidence of diagnosis. The authors recommend routine use of harmonic imaging for abdominal US studies in all adult patients.