Characterization Of Liver Lesions Research Articles

Prospective, open-label, multi-centre study evaluating the accuracy of unenhanced versus SonoVue® enhanced ultrasonography (US) in the characterisation of focal liver lesions

Objective: The aim of this study was to compare the accuracy of unenhanced versus SonoVueTM® enhanced ultrasonography in the characterisation of focal liver lesions.Methods: 127 patients with focal liver lesions were studied using top-of-range equipments with non-linear imaging facilities. Standardised baseline scans and SonoVue® enhanced US (dose: 2 × 2.4 ml and 1 × 4.8 ml) with optimised non-linear imaging modes were performed. On the basis of the tumour vascularity and pattern of enhancement in the vascular phase and degree of contrast uptake within the lesion relative to that of normal liver in the late phase, diagnosis was made as to whether the lesion was benign or malignant. SonoVue® enhanced diagnosis was compared with that of baseline using combined enhanced helical CT, MR, and/or histology as the reference standard.Results: Of the total of 134 lesions studied, 82 were malignant and 52 were benign on the basis of the reference standard. The sensitivity for correctly classifying malignant lesions for unenhanced US was 28% compared with 90% for SonoVue® enhanced US; the difference was highly significant (McNemar’s test: p<0.0001). The specificity for correctly classifying benign lesions for unenhanced US was 35% versus 81% for enhanced US; the difference was highly significant (McNemar’s test: p<0.0001). Of the 25 haemangiomas, diagnosis was correct for unenhanced US in 36% versus 84% for enhanced US with the characteristic display of peripheral nodular centripetal enhancement. Of the 13 FNHs, unenhanced US correctly diagnosed 31% whilst enhanced US was accurate in 77%.Conclusions: These results suggest that SonoVue® enhanced US with non-linear imaging modes is superior to unenhanced US in the characterization of focal liver tumours with significant reduction in the number of indeterminate diagnoses. Objective: The aim of this study was to compare the accuracy of unenhanced versus SonoVueTM® enhanced ultrasonography in the characterisation of focal liver lesions. Methods: 127 patients with focal liver lesions were studied using top-of-range equipments with non-linear imaging facilities. Standardised baseline scans and SonoVue® enhanced US (dose: 2 × 2.4 ml and 1 × 4.8 ml) with optimised non-linear imaging modes were performed. On the basis of the tumour vascularity and pattern of enhancement in the vascular phase and degree of contrast uptake within the lesion relative to that of normal liver in the late phase, diagnosis was made as to whether the lesion was benign or malignant. SonoVue® enhanced diagnosis was compared with that of baseline using combined enhanced helical CT, MR, and/or histology as the reference standard. Results: Of the total of 134 lesions studied, 82 were malignant and 52 were benign on the basis of the reference standard. The sensitivity for correctly classifying malignant lesions for unenhanced US was 28% compared with 90% for SonoVue® enhanced US; the difference was highly significant (McNemar’s test: p<0.0001). The specificity for correctly classifying benign lesions for unenhanced US was 35% versus 81% for enhanced US; the difference was highly significant (McNemar’s test: p<0.0001). Of the 25 haemangiomas, diagnosis was correct for unenhanced US in 36% versus 84% for enhanced US with the characteristic display of peripheral nodular centripetal enhancement. Of the 13 FNHs, unenhanced US correctly diagnosed 31% whilst enhanced US was accurate in 77%. Conclusions: These results suggest that SonoVue® enhanced US with non-linear imaging modes is superior to unenhanced US in the characterization of focal liver tumours with significant reduction in the number of indeterminate diagnoses.

Evidence for liver and spleen specific uptake of the microbubble SonoVue

Objective: Some microbubbles are known to have a liver and spleen specific phase, which can be used to improve liver lesion characterisation or detection. Such a phase has not been described for the new agent, SonoVue (Bracco, Milan, Italy). We have studied the pharmacokinetics of this microbubble using low power non-disruptive scanning.

Ultrasound contrast agents for hepatic imaging with nonlinear modes

Curr Probl Diagn Radiol 2003;32:66.

Ultrasound contrast agents for hepatic imaging with nonlinear modes

The continuing development of nonlinear imaging, as well as a whole new generation of contrast agents, holds out great prospects in improving liver imaging. Optimization of the equipment settings for different classes of contrast agents is essential in the detection and characterization of focal liver lesions. On the basis of the preliminary results of multicenter clinical trials, it is reasonable to assume that their application in specific clinical settings will impact favorably on patient management.

MDCT imaging of the aorta and peripheral vessels

Since its clinical introduction in 1991, volumetric CT scanning using spiral or helical scanners has resulted in a revolution for diagnostic imaging. Helical CT has improved over the past 8 years with faster gantry rotation, more powerful X-ray tubes, and improved interpolation algorithms, but the greatest advance has been the recent introduction of multi detector-row CT (MDCT) scanners [J. Comput. Assist. Tomogr. 23 (1999) S83]. Currently capable of acquiring four channels of helical data simultaneously, MDCT scanners have achieved the greatest incremental gain in scan speed since the development of helical CT and have profound implications for clinical CT scanning. Fundamental advantages of MDCT include substantially shorter acquisition times, retrospective creation of thinner or thicker sections from the same raw data, and improved three-dimensional (3-D) rendering with diminished helical artifacts. While these features will likely be important to many applications of CT scanning, including the characterization of focal lung and liver lesions through the creation of thin sections retrospectively, the greatest impact has been on CT angiography. The implication for CT angiography is that scans can be performed approximately three-times faster than is possible with the fastest single-detector CT scanner. For example a 1.25 mm nominal thick section (1.6 mm effective section thickness) can be acquired with a table speed of 9.4 mm/s, and a 2.5 mm nominal thick section (3.2 mm effective section thickness) can be acquired with an 18.8 mm/s table speed. The advantages of MDCT for imaging the vascular system can be broken down into three fundamental improvements over single detector-row CT scanners speed (faster), distance (longer), and section thickness (better). The focus of this article will be how multidetector-row CT technology has substantially improved aortoiliac and lower extremity arterial imaging.

Characterization of focal liver lesions with superparamagnetic iron oxide-enhanced MR imaging: value of distributional phase T1-weighted imaging.

ObjectiveTo determine the potential value of distributional-phase T1-weighted ferumoxides-enhanced magnetic resonance (MR) imaging for tissue characterization of focal liver lesions.Materials and MethodsFerumoxides-enhanced MR imaging was performed using a 1.5-T system in 46 patients referred for evaluation of known or suspected hepatic malignancies. Seventy-three focal liver lesions (30 hepatocellular carcinomas [HCC], 12 metastases, 15 cysts, 13 hemangiomas, and three cholangiocarcinomas) were evaluated. MR imaging included T1-weighted double-echo gradient-echo (TR/TE: 150/4.2 and 2.1 msec), T2*-weighted gradient-echo (TR/TE: 180/12 msec), and T2-weighted turbo spin-echo MR imaging at 1.5 T before and after intravenous administration of ferumoxides (15 mmol/kg body weight). Postcontrast T1-weighted imaging was performed within eight minutes of infusion of the contrast medium (distributional phase). Both qualitative and quantitative analysis was performed.ResultsDuring the distributional phase after infusion of ferumoxides, unique enhancement patterns of focal liver lesions were observed for hemangiomas, metastases, and hepatocellular carcinomas. On T1-weighted GRE images obtained during the distributional phase, hemangiomas showed a typical positive enhancement pattern of increased signal; metastases showed ring enhancement; and hepatocellar carcinomas showed slight enhancement. Quantitatively, the signal-to-noise ratio of hemangiomas was much higher than that of other tumors (p < .05) and was similar to that of intrahepatic vessels. This finding permitted more effective differentiation between hemangiomas and other malignant tumors.ConclusionT1-weighted double-echo FLASH images obtained soon after the infusion of ferumoxides, show characteristic enhancement patterns and improved the differentiation of focal liver lesions.

Radial fast spin-echo method for T2-weighted imaging and T2 mapping of the liver.

To evaluate a multishot radial fast-spin echo (RAD-FSE) method developed to improve the quality of abdominal T2-weighted imaging as well as the characterization of focal liver lesions. The RAD-FSE sequence used in this work consisted of a preparatory period followed by a short echo train (ETL = 16). A novel radial k-space trajectory was used to minimize streaking artifacts due to T2 variations and motion. Small diffusion gradients (b = 1.2 mm/s(2)) were used to improve flow suppression. The quality of images obtained with RAD-FSE was compared to multishot 2DFT fast spin-echo (2DFT-FSE) and half-Fourier acquisition single-shot turbo-spin-echo (HASTE) images using data from 16 patients. A postprocessing algorithm was used to generate multiple high-resolution images (at different effective TE values) as well as a T2 map from a single RAD-FSE data set. The T2 maps were used to differentiate malignant from benign lesions for a set of 33 lesions ranging from 0.8-194 cm(3). RAD-FSE produces high-resolution images of the liver in a breath-hold without the motion artifacts of 2DFT-FSE methods, and without the blurriness and loss of small lesion detectability of HASTE. The inclusion of diffusion weighting in RAD-FSE decreases the signal from blood in hepatic vessels, which improves lesion visualization. The T2 values obtained by postprocessing a single RAD-FSE data set can differentiate malignant from benign lesions. The mean T2 values obtained for malignancies, hemangiomas, and cysts are 108 +/- 30 msec, 240 +/- 14 msec, and 572 +/- 334 msec, respectively. These results indicate that RAD-FSE produces abdominal images of higher quality than 2DFT-FSE and HASTE. In addition, lesions can be characterized using T2 maps generated from a single RAD-FSE data set.

VIBE with parallel acquisition technique - a novel approach to dynamic contrast-enhanced MR imaging of the liver

The VIBE (volume interpolated breath-hold examination) sequence in combination with parallel acquisition technique (iPAT: integrated parallel acquisition technique) allows dynamic contrast-enhanced MRI of the liver with high temporal and spatial resolution. The aim of this study was to obtain first clinical experience with this technique for the detection and characterization of focal liver lesions. We examined 10 consecutive patients using a 1.5 T MR system (gradient field strength 30 mT/m) with a phased-array coil combination. Following sequences were acquired: T 2 -w TSE and T 1 -w FLASH, after administration of gadolinium, 6 VIBE sequences with iPAT (TR/TE/matrix/partition thickness/time of acquisition: 6.2 ms/ 3.2 ms/256 x 192/4 mm/13 s), as well as T 1 -weighted FLASH with fat saturation. Two observers evaluated the different sequences concerning the number of lesions and their dignity. Following lesions were found: hepatocellular carcinoma (5 patients), hemangioma (2), metastasis (1), cyst (1), adenoma (1). The VIBE sequences were superior for the detection of lesions with arterial hyperperfusion with a total of 33 focal lesions. 21 lesions were found with T 2 -w TSE and 20 with plain T 1 -weighted FLASH. Diagnostic accuracy increased with the VIBE sequence in comparison to the other sequences. VIBE with iPAT allows MR imaging of the liver with high spatial and temporal resolution providing dynamic contrast-enhanced information about the whole liver. This may lead to improved detection of liver lesions, especially hepatocellular carcinoma.

Liver Lesions: Manganese-enhanced MR and Dual-Phase Helical CT for Preoperative Detection and Characterization—Comparison with Receiver Operating Characteristic Analysis

The purpose of this study was to compare, by means of receiver operating characteristic (ROC) analysis, dual-phase helical computed tomography (CT) and manganese-enhanced magnetic resonance (MR) imaging in the detection and characterization of hepatic lesions in patients prior to surgery. Twenty-five patients known to have or suspected of having hepatic lesions who were eligible for surgery underwent dual-phase (ie, arterial and portal phase) helical CT and phased-array MR imaging (ie, unenhanced fast spin-echo T2-weighted imaging and gradient-echo T1-weighted imaging performed before and after administration of mangafodipir trisodium). All images were reviewed independently by three off-site blinded reviewers who separately reviewed the CT scans and MR images. The standard of reference was findings at surgery, intraoperative ultrasonography (US), and histopathologic examination. ROC curves were established to analyze the results for each reader and modality. Ninety-four lesions (77 malignant and 17 benign) were revealed at surgery, intraoperative US, and/or histopathologic examination. The overall rate of lesion detection for the three readers at CT was 81.9% +/- 7.8, 90.4% +/- 5.9, and 76.6% +/- 8.6. At MR imaging, the detection rates were 72.3% +/- 9.0, 71.3% +/- 9.1, and 69.1% +/- 9.3 (P =.001 for the difference between MR and CT). The average rate of false-positive diagnoses in patients was 14.1% at CT and 6.4% at MR imaging (P =.06 for the difference between MR and CT). The mean areas under the alternative-free-response ROC curves were 0.74 for MR and 0.72 for CT (P =.751, not significant). In detection and characterization of liver lesions, manganese-enhanced MR imaging and dual-phase helical CT were not statistically different.

Multislice CT of the abdomen--current indications and future trends

Multislice CT systems allow the simultaneous acquisition of multiple slices per gantry rotation. In combination with faster gantry rotation times of 0.5 seconds, the abdominal structures can be displayed in higher spatial and temporal resolution. In MS-CT of the liver it is possible to scan the entire organ with an optimal slice thickness of 2 - 3 mm within a defined perfusion phase in less than 10 seconds. This results in an improved detection and characterization of focal liver lesions. A high-quality, 3-dimensional reconstruction of the hepatic arterial and portalvenous system is obtained with the same data set. The diagnostic use of the simultaneously acquired perfusion data will lead to a better characterization of focal liver lesions in the future. The diagnostics of the pancreas also profits from MS-CT, especially for the detection of small tumors and the evaluation of resectability of a pancreatic carcinoma. All abdominal structures can be displayed in a coronal view without loss of image quality because of the almost isotropic voxels obtained. This proves to be beneficial for the preoperative diagnostics of renal cell carcinomas, especially if the tumor extension into adjacent organs (e. g., liver or spleen) in the longitudinal direction has to be evaluated. The multiplanar display and the sophisticated 3-dimensional reconstruction tools have a substantial value for the abdominal CT angiography. It proves to have a major diagnostic impact on acute abdominal aortic and visceral arterial diseases because even large distances in the z-direction can be covered with high spatial resolution.

Gadodiamide and Gadopentetate Dimeglumine in MRI versus Spiral CT in the Diagnosis of Liver Lesions

The purpose of this study was to compare the effectiveness of dynamic MRI (0.1 mmol/kg b.w. and 0.3 mmol/kg b.w. gadodiamide injection [OMNISCAN™]; 0.1 mmol/kg b.w. gadopentetate dimeglumine [MAGNEVIST™]) and dual-phase spiral CT in the detection and characterisation of liver lesions.

Ultrasound Imaging of Focal Liver Lesions with a Second-Generation Contrast Agent

For several years, the major diagnostic objective in using US contrast agents has been to detect flow in the circulation at a lower level than that otherwise possible in Doppler techniques. However, it turned out that enhanced color and power Doppler could provide fine details on small and deep vessels, but were not sensitive enough to detect contrast agents in the microcirculation. As a result, the usefulness of contrast agents in the field of liver imaging was limited to the evaluation of the vascular architecture of focal lesions. Recently, the development of new US techniques that produce images based on nonlinear acoustic effects of US interaction with microbubble contrast agents has opened new prospects for US imaging of the liver. These contrast-specific imaging techniques, in fact, can display microbubble enhancement in gray-scale, thus maximizing contrast and spatial resolution and enabling the analysis of the microcirculation. These techniques offer high sensitivity either to microbubble movement or to microbubble collapse independent of the level of the applied acoustic peak pressure. At low acoustic peak pressure levels grossly reflected by a low mechanical index (MI) the microbubble destruction can be reasonably neglected and the microbubble movement effect due to blood circulation is predominant. In contrast, when increasing the acoustic peak pressure levels (high MI), the destruction phenomena become the most important: the signal, in fact, is produced by microbubble collapse, and is related to microbubble concentration and not to blood flow velocity (1–3). We performed a pilot clinical study aimed at investigating the usefulness of both destructive (high MI) and non-destructive (low MI) gray-scale US techniques, in combination with a second-generation contrast agent, for the detection and characterization of focal liver lesions.

Characterization of Focal Liver Lesions with Phase Inversion Ultrasound During the Late Liver-Specific Phase of Levovist

On baseline scans mean C-values were: metastasis: 2.8 ( 5.5) dB, HHC: 3.2 ( 4.0) dB, haemangioma: 3.9 ( 5.1) dB, FNH 0.9 ( 4.8) dB, FF: 1.0 ( 7.6) dB, all malignant lesions: 2.9 ( 5.1) dB, all benign lesions: 1.6 ( 6.1) dB. On contrast enhanced PIUS mean C-values were: metastasis: 17.9 ( 7.3) dB, HHC: 14.5 ( 9.4) dB, haemangioma: 1.4 ( 5.6) dB, FNH 4.4 ( 5.15) dB, FF: 0.4 ( 2.1) dB, all malignant lesions: 17.0 ( 7.9) dB, all benign lesions: 1.8 ( 5.1) dB. The differences between benign and malignant lesions were significant both pre and post contrast (p 0.02 and p 0.0001). However on baseline there was a big overlap between the 2 groups and no discrimination was possible. Conversely, post Levovist all malignant lesions showed a C 5 dB while all but two benign lesions (one haemangioma and one FF) had a C 5dB.

Characterization of Focal Liver Lesions with Pulse Inversion Harmonic Imaging (PIHI) Using a Second Generation US Contrast Agent

First generation ultrasound (US) contrast agents are made by air microbubbles stabilized by albumin or D-galactose. Second generation US contrast agents comprise agents made of stabilized microbubbles of gases of high molecular weight and low solubility in water, which provide a higher resistance to US pulse pressure and a longer persistence in the bloodstream than first generation agents (1,2). Furthermore, the second generation contrast agents have a good harmonic response even at mid and low mechanical index (MI).

Liver Lesion Detection and Characterization with Sequential use of Hepatobiliary Contrast Agent Mangafodipir Trisodium and Gadolinium-DTPA in a Single Imaging Protocol

Liver Lesion Detection and Characterization with Sequential use of Hepatobiliary Contrast Agent Mangafodipir Trisodium and Gadolinium-DTPA in a Single Imaging Protocol

Low-Dose Gadobenate Dimeglumine-Enhanced MRI in the Detection and Characterization of Focal Liver Lesions

Magnetic resonance imaging (MRI) of the liver with conventional nonspecific gadolinium-based contrast agents has traditionally been performed at a dose of 0.1 mmol/kg of body weight. When administered as a bolus and combined with image acquisition during the dynamic phase of contrast enhancement, these agents at this dose have been used for the characterization of focal liver lesions (FLLs) ( 1 Hamm B Thoeni RF Gould RG et al. Focal liver lesions: characterization with nonenhanced and dynamic contrast material–enhanced MR imaging. Radiology. 1994; 190: 417-423 Crossref PubMed Scopus (217) Google Scholar , 2 Semelka RC Shoenut JP Kroeker MA et al. Focal liver disease: comparison of dynamic contrast-enhanced CT and T2-weighted fat-suppressed, FLASH, and dynamic gadolinium-enhanced MR imaging at 1.5 T. Radiology. 1992; 184: 687-694 Crossref PubMed Scopus (198) Google Scholar ). Unfortunately, these agents have not always proven satisfactory for the improved detection of FLLs, especially hypovascular metastases ( 3 Peterson MS Baron RL Murakami T Hepatic malignancies: usefulness of acquisition of multiple arterial and portal venous phase images at dynamic gadolinium-enhanced MR imaging. Radiology. 1996; 201: 337-345 Crossref PubMed Scopus (146) Google Scholar , 4 Hamm B Mahfouz AE Taupitz M et al. Liver metastases: improved detection with dynamic gadolinium-enhanced MR imaging?. Radiology. 1997; 202: 677-682 Crossref PubMed Scopus (96) Google Scholar ).

The role of contrast-enhanced ultrasound in the characterisation of focal liver lesions.

The role of contrast-enhanced ultrasound in the characterisation of focal liver lesions.

Multi-centre clinical study evaluating the efficacy of SonoVue™ (BR1), a new ultrasound contrast agent in Doppler investigation of focal hepatic lesions

Objectives: SonoVue™ is a new ultrasound contrast agent, which consists of stabilised microbubbles of a sulphur hexafluoride gas. The aim of the study was to assess its efficacy in the Doppler investigation of focal hepatic lesions. Materials and methods: Seventy patients with focal liver tumours were studied. Four doses (0.3, 0.6, 1.2 and 2.4 ml) of SonoVue™ were administered intravenously with at least 10 min delay between each injection. A complete colour/power and spectral Doppler imaging investigation of the lesions was performed at baseline pre-dosing and after each SonoVue injection. All examinations were recorded on SVHS videotapes. Baseline and post contrast videotapes were reviewed by the on-site (un-blinded) investigators and by two off-site blinded readers (a) to grade the global quality of the Doppler scans of the focal lesions vascularity and the normal parenchymal vessels (b) to measure the duration of clinically useful Doppler signal enhancement and (c) to determine the diagnostic accuracy and performance of the enhanced versus unenhanced scans using histopathology, tumour markers, CT and/or MR as the reference standard. Results: A statistically significant improvement was observed at all four SonoVue doses in the off site assessment of global quality of the Doppler examination of tumoral and normal parenchymal vessels in comparison with the baseline ( P<0.05). The median duration of clinically useful enhancement was significantly increased with increasing doses ( P<0.001), ranging between 1.4–2.2 min for the lowest dose and 3.2–3.8 min for the highest dose for the off-site readers. On-site assessment of diagnostic accuracy showed a significant increase in the specificity of the Doppler diagnoses ( P<0.0016) with an increase in the positive and negative predictive values and in the likelihood ratio in differentiating between benign and malignant lesions. Off-site evaluation showed a significant increase in the accuracy of enhanced Doppler diagnosis in comparison with the baseline performance. Conclusion: The results suggest that SonoVue™ is effective in improving the display of tumoral vascularisation and may be useful in the characterisation of focal liver lesions.

VOLUMETRIC MR IMAGING OF THE LIVER AND APPLICATIONS

Recent improvements in MR technology have enabled the development of volumetric three-dimensional (3D) imaging methods for fat-suppressed T1-weighted images of the entire upper abdomen with pixel sizes of approximately 2 mm in all dimensions and with acquisition times of less than 25 seconds for breath-hold imaging. When performed with a timing scheme, dynamic contrast-enhanced volumetric imaging of the liver can be performed with selective imaging during the arterial phase and portal venous phase of enhancement. The volumetric data sets can be reconstructed in any oblique plane, enabling improved detection, localization, and characterization of small liver lesions. The combination of high-resolution isotropic pixels and accurate timing also permits angiographic reconstructions of the 3D images, producing MR angiography and venography that can be useful in therapeutic planning, such as for catheter-based interventions or surgical resections or transplantation. Additionally, with use of a hepatobiliary contrast agent such as mangafodipir, T1-weighted volumetric MR cholangiography can be performed in patients with nonobstructed systems for depiction of intrahepatic biliary anatomy.

Tissue harmonic and contrast-specific imaging: back to gray scale in ultrasound.

The development of new US techniques that produce images based on nonlinear acoustic effects of US interaction with matter or microbubble contrast agents has opened new prospects for gray-scale US in native tissue and contrast imaging. Tissue harmonic imaging uses higher frequencies generated on propagation of the US beam through matter to improve image quality and resolve small anatomic structures and details, and is becoming a routine approach in US examination of many abdominal districts. Contrast-specific imaging techniques display enhancement of US agents in gray-scale with optimal contrast and spatial resolution, and offer high sensitivity either to microbubble movement or to microbubble destruction in dependence of the level of the applied acoustic peak pressure. Owing to the ability to exploit the microcirculation, contrast-specific techniques have enabled the evolution of contrast US from vascular imaging to the imaging of perfused tissues. Several studies have shown that these methods can substantially improve US detection and characterization of focal liver lesions, and promising results have been reported in other areas of investigation. This article reviews physical principles, technical issues, and clinical applications of tissue harmonic and contrast-specific imaging. It is foreseen that the new gray-scale US techniques will rapidly become a tool in numerous clinical scenarios.