Roles of contrast-enhanced ultrasound and diffusion-weighted magnetic resonance imaging and their comparison in solid space-occupying lesions of the liver – Microbubbles and micromovements in imaging

Abstract

Aims: This study aims to establish the role of contrast-enhanced ultrasound (CEUS) and diffusion-weighted (DW) magnetic resonance imaging (MRI) in the characterization of solid liver lesions. Settings and Design: An analysis of 22 patients undergoing CEUS and DW MRI following identification of 1 or more solid liver lesions on conventional ultrasonography. Subjects and Methods: The study is carried in a standard Doppler ultrasound machine with contrast ultrasound capabilities and 1.5T MRI machine over a period of 2 years from July 2015 to June 2017. After baseline US examination, a bolus of 1.0–2.4 ml of ultrasound contrast agent was administered intravenously followed by 10 ml of saline flush. CEUS images were obtained during arterial, portal venous, and delayed phases. After CEUS, patient is transferred to MRI scanning room where the DW imaging (DWI) sequence is taken. The CEUS and DW MRI diagnosis were compared to other imaging modalities, histopathology, and/or clinical follow-up after 12 months. Statistical Analysis Used: Sensitivity, specificity, positive predictive value, negative predictive value, accuracy rate and receiver operating characteristic analysis curve was performed using Statistical Package – SPSS ver. 17.0. Statistical evaluation of qualitative analysis between benign and malignant lesions was performed using the Fisher's exact test. Results: CEUS correctly identified malignant liver lesions in 13 out of 14 cases, with the final diagnosis confirmed by histopathology in 6 cases, by other imaging modalities in 7 cases and follow-up in 1 case. Eight patients were correctly identified as benign liver lesions on CEUS imaging, with all these cases confirmed on other imaging modalities and/or follow-up and two cases by histopathology. In the detection of malignancy, the sensitivity is 86.7% and specificity is 100%. On the DW images the Mean apparent diffusion coefficient (ADC) value for benign lesions is 1.5 and mean ADC value for malignant lesions is 0.7. The ADC was significantly higher in benign lesions than in malignant lesions (P < 0.01). Conclusions: In our experience, CEUS and DWI with ADC values are highly accurate in confirming benign lesions, early detection of malignant lesions, and metastases in known primary malignancy patients. Other advantage of CEUS and DW MRI is that it is also cost-effective as compared to simultaneously performing individual investigations and can be performed in renal insufficiency patients. Hence, we conclude that CEUS and DW MRI sequence should be used in routine practice.