Characterization of Ovarian Masses using Contrast-Enhanced Subharmonic Imaging

This clinical pilot study evaluated whether contrast-enhanced ultrasound subharmonic imaging (CEUS SHI) could be used to characterize indeterminate ovarian masses prior to surgical intervention. Ten women (with twelve lesions) scheduled for surgery of an ovarian mass underwent CEUS SHI examination of their pelvis using a modified Logiq E9 scanner (GE Healthcare, Waukesha, WI, USA) with an endocavitary transducer. Patients first received a bolus injection of ultrasound contrast agent Definity (Lantheus Medical Imaging, N Billerica, MA, USA), while ultrasound imaging was continuously performed up to 5 minutes after contrast injection. Following a 10 minute wait to ensure contrast agent clearance from the circulation, patients received an infusion of 1.5 ml of Definity diluted in 25 ml of saline over 5 minutes. During this time, destruction/ replenishment CEUS SHI imaging was performed in multiple planes across the lesion. The contrast time intensity curves were created off-line to quantitatively evaluate CEUS SHI kinetic parameters, which were compared to the tissue histology of the lesion after surgery. Of the 12 lesions, 8 were benign and 4 were malignant. Qualitative analysis of CEUS SHI images by a radiologist with 15 years of CEUS experience demonstrated diagnostic accuracy (determined as the area under the ROC curve) of 70%, compared to 56% without contrast, while analysis by a radiologist with 6 months of experience only improved from 50% to 57%. Diagnostic accuracy of quantitative CEUS SHI kinetic parameters was as high as 81%. Malignant masses showed significantly higher peak contrast intensity (p = 0.046) and overall perfusion (p = 0.045) than benign lesions. These results suggest that CEUS SHI for pre-surgical characterization of ovarian lesions may improve determination of malignancy, albeit based on a small sample size.