Characterization of Focal Liver Lesions using CEUS and MRI with Liver-Specific Contrast Media: Experience of a Single Radiologic Center.

AIM: The purpose of this study was to compare contrast-enhanced ultrasound (CEUS), magnetic resonance imaging (MRI) using liver-specific contrast agent and a combination of both for the characterization of focal liver lesions (FLL). METHODS: 83 patients with both benign and malignant liver lesions were examined using CEUS and MRI after the intravenous administration of liver-specific contrast media. All patients had inconclusive results from prior imaging examinations. Histopathological specimens could be obtained in 53 patients. Ultrasound was performed using a multi-frequency curved probe (1 - 6 MHz) after the injection of 1 - 2.4 ml ultrasound contrast media. The sensitivity, specificity, positive predictive value and negative predictive value of CEUS, MRI and a combination of both (CEUS + MRI) were compared. RESULTS: The sensitivity, specificity, positive and negative predictive values regarding lesion classification were 90.9 %, 70.6 %, 92.3 % and 66.6 %, respectively, for CEUS; 90.9 %, 82.4 %, 95.2 % and 70.0 %, respectively, for MRI; and 96.9 %, 70.6 %, 92.7 % and 85.7 % respectively, for CEUS + MRI. There were no statistically significant differences. 6 malignant lesions were missed using CEUS or MRI alone (false negatives). The use of both modalities combined reduced the false-negative results to 2. CONCLUSION: CEUS and MRI with liver-specific contrast media are very reliable and of equal informative value in the characterization of focal liver lesions. The number of false-negative results can be decreased using a combination of the two methods.

Acquisition of 3D temperature distributions in fluid flow using proton resonance frequency thermometry.

PURPOSE: Proton resonance frequency thermometry is well established for monitoring small temperature changes in tissue. Application of the technique to the measurement of complex temperature distributions within fluid flow is of great interest to the engineering community and could also have medical applications. This work presents an experimental approach to reliably measure three-dimensional (3D) temperature fields in fluid flow using proton resonance frequency thermometry. METHODS: A velocity-compensated three-dimensional gradient echo sequence was used. A flexible pumping system was attached to an MR compatible double pipe heat exchanger. The temperature of two separate flow circuits could be adjusted to produce various three-dimensional spatial temperature distributions within the fluid flow. Validation was performed using MR compatible temperature probes in a uniformly heated flow. A comparative study was conducted with thermocouples in the presence of a spatially varying temperature distribution. RESULTS: In uniformly heated flow, temperature changes were accurately measured to within 0.5 K using proton resonance frequency thermometry, while spatially varying temperature changes measured with MR showed good qualitative agreement with pointwise measurements using thermocouples. CONCLUSION: Proton resonance frequency thermometry can be used in a variety of complex flow situations to address medical as well as engineering questions. This work makes it possible to gain new insights into fundamental heat transfer phenomena. Magn Reson Med 76:145-155, 2016. © 2015 Wiley Periodicals, Inc.