Coded Tissue Harmonic Ultrasound of Focal Hepatic Lesions: Comparison of Image Quality with Conventional Ultrasound

Abstract

Background Harmonic waves are generated from nonlinear distortion of an acoustic signal under an ultrasound wave traveling through the body. These beams are integer multiples of a fundamental transmitted frequency. Potential benefits of harmonic imaging include improved contrast resolution and better lateral resolution. Decreased noise from side lobes improves the signal-to-noise ratio and reduces artifacts. A variety of implementations now exist to create tissue harmonic imaging (THI), including frequency filtering, pulse inversion/phase cancellation and coded harmonics. The purpose of this study was to evaluate the image quality of coded tissue harmonic ultrasound (US) compared to conventional US for focal hepatic lesions. Materials and Methods A total of 275 patients with focal hepatic lesions were scanned with both conventional and coded tissue harmonic US. The hepatic lesions were classified into cystic, hypoechoic, hyperechoic, and heterogeneous appearance according to sonographic features. Analysis of these lesions focused on comparing THI with conventional US for visibility and providing more diagnostic information. Image quality was assessed as excellent, good, satisfactory, poor or unsatisfactory. Results Images were considered better with THI in 174 cases (63%), particularly in cystic (76%) and hyperechoic (71%) lesions. Mean visibility scores of lesions with THI were 4.12 for cystic lesions, 3.75 for hypoechoic lesions, 4.07 for hyperechoic lesions and 3.64 for heterogeneous lesions. Conclusion THI significantly improved image quality in focal hepatic lesions, especially for cystic or hyperechoic lesions.