Ultrasound matches CT in detecting hepatic abscesses
Using a low mechanical index technique and ultrasound contrast, Italian researchers have diagnosed liver abscesses caused by pyogenic organisms.
?The gold standard for imaging hepatic abscesses is contrast-enhanced CT. Low mechanical index, contrast-enhanced ultrasound compares quite well,? said lead author Dr. Orlando Catalano of the radiology department at S. Maria delle Grazie Hospital in Naples.
Imagers using the low mechanical index contrast-specific sonography technique can harness the harmonic capabilities of the newest generation of contrast agents to produce real-time contrast-enhanced gray-scale images. Physicians at his institution have been using the technique since January 2002, Catalano said. Their study was published in the February issue of the American Journal of Roentgenology.
Catalano and colleagues examined eight patients with aspiration-confirmed pyogenic liver abscesses. They performed baseline sonography and then obtained contrast-enhanced ultrasound exams using a 3.5-MHz convex transducer and sulfur hexafluoride-based microbubble contrast agent. All cases were correlated with spiral CT findings.
The researchers discovered 13 abscesses in eight patients. This ultrasound technique holds two important advantages over other modalities, like CT and MRI, in this application, according to Catalano. First, it allows researchers to perform imaging studies immediately without fasting, laboratory testing, or additional adverse reaction risk.
?Second, this technique allows for the unique possibility to evaluate liver lesions in real-time. We don?t have two or three phases, as you would for CT or MRI, but hundreds of phases that can be used to rescan the region of interest continuously for four to five minutes until we get a diagnosis,? Catalano said.
The real-time nature of the ultrasound images enabled the researchers to recognize lesion morphology that was not detected on the CT scans: · rim enhancement · dense and persistent septal enhancement · transient arterial phase hypervascularity around abscesses · portal phase hypovascularity around abscesses
?In our country, ultrasound is usually the first imaging employed to study the liver,? Catalano said. ?By using low mechanical index contrast-enhanced ultrasound, we can have an immediate and definitive diagnosis without scheduling the patient for a CT study.?
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