Evaluation of tissue harmonic imaging for breast tumors and axillary lymph nodes

We examined whether tissue harmonic imaging (THI) produces higher quality images of the breast and axilla than conventional sonography (CS). We studied 70 breast tumors in 68 consecutive patients and 170 axillary lymph nodes in 19 breast cancer patients. These areas were investigated by THI and CS, then image quality was evaluated by the consensus of three skilled radiologists. THI transmits and receives at 5.0 and 10.0 MHz, respectively, whereas CS uses 9.0 MHz. The evaluation parameters of image quality consisted of contrast and resolution with a visual scoring system. Resolution was individually evaluated on both proximal and distal sides of lesions. The grade of acoustic shadow was also evaluated. The quality in contrast (p<0.001) and proximal resolution (p<0.001) of breast tumors by THI was far superior to those of CS. Intense acoustic shadows degraded the distal resolution of breast lesions in THI compared with CS, but the quality of THI images of the axillary lymph nodes was higher with respect to all parameters (p<0.001). The grade of acoustic shadows did not differ between two modes of gray-scale sonography for lymph nodes. THI may improve diagnostic accuracy of breast and axillary lesions because image quality is improved, but acoustic shadows continue to present obstacles.