Comparing the image quality of tissue harmonic and conventional B-mode ultrasound of kidney in over-obese individuals.

Background: Increased subcutaneous fat thickness and depth of target organs in over-obese patients, results in weak signals and inadequate images. Tissue harmonic imaging has been used widely in obese patients and is believed to result in higher quality images. This superiority is not proved in modern machines with improved image quality in conventional mode.

Objective: To compare the image quality between conventional and tissue harmonic ultrasound images.

Methods: This cross-sectional study was carried out from March 2015 to June 2016. Seventy-six over-obese patients referred to Ghaem Hospital (Mashhad, Iran) for weight-correction surgeries, were enrolled into the study. Conventional and tissue harmonic images of their kidneys were blinded and compared back-to-back by four expert radiologists. Data were analyzed by SPSS version 16, using Cochrane's Q test.

Results: All raters reported image quality to be better in tissue harmonic compared to fundamental frequency ultrasound (p=0.000, Cochrane's Q test). Although better image quality in tissue harmonic mode was reported by the four raters, there was weak inter-observer agreement (p=0.081 for right kidney and p=0.21 for left kidney).

Conclusion: Advances in ultrasound equipment and the introduction of tissue harmonic imaging can improve the diagnostic performance in over-obese patients and this mode of imaging should be used whenever evaluating over-obese subjects.