Aim: To determine whether delayed-phase liver imaging using a destructive imaging mode is able to provide similar information to phase-inversion imaging regarding detection and conspicuity of liver metastases.
Material and methods: Patients with a known primary malignancy with suspected liver metastases were recruited. Ultrasound was performed at baseline, and up to 5 min after the administration of Sonazoid, using phase-inversion imaging at both low and high mechanical indices (MI) and at 10-15 min using destructive imaging. One of four doses of Sonazoid was used: 0.008, 0.08, 0.12, and 0.36 microl/kg of body weight. Two observers documented lesion number and conspicuity subjectively, and divided the patients into group A (no lesions), group B (one to seven lesions), and group C(I-III) (more than eight lesions, subdivided with increasing lesion number) depending on the number of lesions and categories I-IV based on lesion conspicuity. These parameters were compared with contrast-enhanced computed tomography (CECT) as the reference standard.
Results: Sixteen patients were examined (six women, 10 men), mean age 67.3 years (range 48-83 years). Based on CECT imaging, the division was as follows: group A n=1, group B n=8, group C(I)n=1, group C(II)n=4, group C(III)n=2. The accuracy of baseline ultrasound versus CECT was 75% (in 12 of the 16 patients the group concurred) and the accuracy for contrast-enhanced ultrasound (CEUS) versus CECT was 93.8% (15/16). There was a significant improvement in lesion conspicuity for both low (p=0.0029) and high MI phase-inversion (p=0.0004) and destructive (p=0.0015) CEUS imaging in comparison with baseline ultrasound. Artefact was noted at higher doses of Sonazoid; and no side effects were recorded.
Conclusion: Following a single, intravenous injection of Sonazoid, the properties of this microbubble allow for a and robust examination of the liver using two different techniques with comparable results.