Contrast-Enhanced Ultrasound in the Assessment of Patients with Indeterminate Abdominal Findings at Positron Emission Tomography Imaging

Abstract

Widespread use of fluorodeoxyglucose-positron emission tomography (PET) in cancer imaging may result in a number of indeterminate and false-positive findings. We investigated the role of contrast-enhanced ultrasound (CEUS) as a second-level option after inconclusive PET. We reviewed CEUS images acquired over 4 y, selecting the examinations performed specifically to better assess an unclear PET image. Final diagnosis was confirmed by biopsy, surgery, further imaging or follow-up. Seventy CEUS examinations were performed after a PET scan (44 PET examinations, 19 PET-computer tomography [CT] examinations and 7 PET-CECT examinations). The target organ was the liver in 54 cases, spleen in 12, gallbladder in 2 and pancreas and kidney in one each. In 6 of 70 cases, CEUS was performed because of a negative PET (no uptake) despite an abnormal finding on the CT images of the PET-CT study; CEUS allowed a correct diagnosis in all of these. In 20 of 70 cases, the PET findings were categorized as indeterminate and non-specific (non-specific fluorodeoxyglucose uptake in PET report with no standardized uptake value given); CEUS reached a correct diagnosis in 19 of the 20 cases with one false negative. In 34 of 70 cases, PET was indeterminate, but specific (fluorodeoxyglucose uptake with a standardized uptake value provided); CEUS reached a correct diagnosis in 30 of these 34 cases. In 10 of 70 cases, PET was categorized as determinate but to be investigated because of discrepancy with clinical or imaging findings; CEUS a definitive diagnosis in 9 of 10 cases. CEUS proved to be effective option in the assessment of cancer patients with indeterminate PET findings.

Keywords: Abdomen; Cancer; Contrast-enhanced sonography; Focal liver lesions; Positron emission tomography.