Phase-inversion sonography during the liver-specific late phase of contrast enhancement: Improved detection of liver metastases

OBJECTIVE. The purpose of our study was to assess whether phase-inversion s onography during the late, liver-specific phase of contrast enhancement usi ng Levovist improves the detection of hepatic metastases relative to unenha nced conventional B-mods sonography. SUBJECTS AND METHODS. Sixty-two patients were studied with unenhanced B-mod e sonography and phase-inversion sonography 2.5 min after the injection of Levovist. All patients underwent one reference examination (CT, MR imaging, or intraoperative sonography). The conspicuity, number, size, and distribu tion of metastases before and after contrast administration as judged by a sonographer (who was unaware of other imagine findings) were compared with each other and with reference imaging. RESULTS. The conspicuity of metastases was improved by contrast-enhanced ph ase inversion in 94% of patients. Thirty-nine patients showed metastases on reference imaging; 36 of these were positive on baseline sonography and 38 on phase-inversion sonography, Phase-inversion sonography showed mole refe rence imaging-confirmed metastases than baseline sonography in 28 patients (45%). The average number of confirmed metastases per patient was 3.06 for baseline sonography and 5.42 for contrast-enhanced phase-inversion sonograp hy (p < 0.01). The average sensitivity for detecting individual metastases improved from 63% to 91%. Metastases of less than 1 cm were shown in 14 pat ients on baseline sonography, in 24 patients on phase-inversion sonography and in 26 on reference imaging, Both sonographic techniques showed false-po sitive lesions in six patients. CONCLUSION. Contrast-enhanced phase-inversion sonography in the liver-speci fic phase of contrast enhancement using Levovist provides a marl;ed improve ment in the detection of hepatic metastases relative: to unenhanced convent ional sonography, without loss of specificity. Phase-inversion sonography w as particularly advantageous in detecting small metastases and may be a com petitive alternative to CT and MR imaging.