Bolus Compared with Continuous Infusion of Microbubble Contrast Agent Using Real-Time Contrast Harmonic Imaging Ultrasound in Breast Tumors

Background: Contrast-enhanced ultrasound (CEUS) has gained interest because of its ability to gather vascular information in various organs. There is still a matter of debate concerning its value in breast lesions. The method of choice on how to administer the contrast agent varies depending on the organ to be studied. Infusion of microbubbles is used in echocardiography, while bolus administration is the preferred technique for abdominal organs. Purpose: To compare―in equal doses―bolus versus continuous infusion of microbubbles, using real-time contrast harmonic imaging in breast tumors. Material and Methods: A total of 29 female patients (mean age 54 years) with either clear malignant or benign findings in the breast or axilla were included. Contrast harmonic imaging (CHI US) was performed with a Philips iU22 using an L9-3 MHz linear probe, especially designed for this purpose. A low mechanical index (0.06-0.07) was used to avoid massive destruction of the microbubbles. A dose of 2.4 ml of Sono Vue was first infused intravenously over 1 min with an infusion pump. After 10 min, the same dose was injected as a bolus over 2 s, followed by a flush of 10 ml of saline solution. Contrast uptakes by the tumors were recorded 2 min from the moment of injection, with both methods for each patient. Results: Bolus administration of contrast agent provided a sharply demarcated enhancement and wash-out pattern for all lesions. The continuous infusion of the same contrast agent failed to show any wash-in/wash-out or time-to-peak/peak intensity phenomena in all cases. Conclusion: CEUS using real-time harmonic imaging in order to evaluate breast tumors should be performed with bolus administration of contrast agent in order to achieve better intensity/time curve outcomes.