Objective: The purpose of our study was to evaluate whether sonographic characterization of focal splenic lesions could be improved by using low mechanical index pulse-inversion sonography after sulfur hexafluoride-filled microbubble injection.
Materials and methods: One hundred forty-seven splenic lesions (68 benign, 79 malignant) in 147 patients (81 men, 66 women; mean age, 51 years) underwent baseline gray-scale sonography and sulfur hexafluoride-enhanced low-acoustic-power pulse-inversion sonography (mechanical index < 0.1). Two site investigators assessed in consensus lesion and splenic enhancement during arterial and parenchymal phases. Four readers (readers 1 and 2, blinded; and readers 3 and 4, unblinded to clinical data) independently reviewed baseline and contrast-enhanced sonograms and provided confidence rating for diagnosis of malignancy or benignancy. Accuracy, sensitivity, specificity, positive and negative predictive values, and areas under the receiver operating characteristic curves (A(z)) were calculated by considering biopsy results or splenectomy (51 patients) or CT or MR images followed by serial sonography 6-12 months apart (96 patients) as reference standards.
Results: Benign lesions appeared predominately non- or isoenhancing relative to splenic parenchyma, whereas malignant lesions appeared predominately progressively hypoenhancing. For correct diagnosis of benignancy or malignancy, review of contrast-enhanced sonography after baseline sonography yielded significantly improved diagnostic performance (overall accuracy, 51%, 43%, 70%, and 74% before vs 83%, 81%, 92%, and 91% after contrast-enhanced sonography for readers 1, 2, 3, and 4; p < 0.05; respectively) and significantly improved diagnostic confidence (A(z), 0.770, 0.678, 0.900, and 0.917 before vs 0.935, 0.917, 0.984, and 0.959 after contrast-enhanced sonography for readers 1, 2, 3, and 4; p < 0.05; respectively).
Conclusion: Sulfur hexafluoride-filled microbubble-enhanced sonography improves characterization of focal splenic lesions with and without the availability of clinical data.