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 sonography during the late, liver-specific phase of contrast enhancement using Levovist improves the detection of hepatic metastases relative to unenhanced conventional B-mode sonography. SUBJECTS AND METHODS: Sixty-two patients were studied with unenhanced B-mode 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 distribution of metastases before and after contrast administration as judged by a sonographer (who was unaware of other imaging findings) were compared with each other and with reference imaging. RESULTS: The conspicuity of metastases was improved by contrast-enhanced phase 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 more reference 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 sonography (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 patients on baseline sonography, in 24 patients on phase-inversion sonography, and in 26 on reference imaging. Both sonographic techniques showed false-positive lesions in six patients. CONCLUSION: Contrast-enhanced phase-inversion sonography in the liver-specific phase of contrast enhancement using Levovist provides a marked improvement in the detection of hepatic metastases relative to unenhanced conventional sonography, without loss of specificity. Phase-inversion sonography was particularly advantageous in detecting small metastases and may be a competitive alternative to CT and MR imaging.

B-mode enhancement at phase-inversion US with air-based microbubble contrast agent: initial experience in humans.

Pulse- or phase-inversion ultrasonography (US) sums the signals returned from two 180 degrees ultrasound pulses. Linear scattering from tissue results in a signal void while nonlinear signals from microbubbles stand out. The technique was applied with a US contrast agent in 39 human subjects. B-mode enhancement of vessels and organ parenchyma was seen in all cases. Enhancement occurred from flowing and stationary microbubbles. The flow-independent enhancement of normal and abnormal tissue represents a major advance in contrast material-enhanced US with many potential applications especially in tumor imaging.

Matrix-assisted laser desorption/ionization mass spectrometry of nucleic acids with wavelengths in the ultraviolet and infrared.

A number of different matrices have been tested and compared for ultraviolet and infrared (UV and IR) matrix-assisted laser desorption/ionization (MALDI) of oligodeoxyribonucleotides and mixtures thereof, as well as ribonucleic acids (tRNA from yeast and rRNA from E. coli). A new technique for removing alkali cations from nucleic acid samples during sample preparation on the sample support is demonstrated. The amount of oligonucleotide sample consumed during a typical measurement in IR-MALDI-MS was determined.