Hepatic Signal Intensity Research Articles

Abstract No. 532 Analysis of Hepatic Signal Intensity Characteristics in Gadoxetate Disodium (Eovist) Enhanced Dynamic MRI Following TIPS Creation: A Single Institution Experience

Abstract No. 532 Analysis of Hepatic Signal Intensity Characteristics in Gadoxetate Disodium (Eovist) Enhanced Dynamic MRI Following TIPS Creation: A Single Institution Experience

Gadoxetic acid-enhanced MRI-derived functional liver imaging score (FLIS) and spleen diameter predict outcomes in ACLD.

Functional liver imaging score (FLIS) - derived from gadoxetic acid-enhanced MRI - correlates with liver function and independently predicts liver-related mortality in patients with chronic liver disease (CLD), while splenic craniocaudal diameter (SCCD) is a marker of portal hypertension. The aim of this study was to investigate the accuracy of a combination of FLIS and SCCD for predicting hepatic decompensation, acute-on-chronic liver failure (ACLF), and mortality in patients with advanced CLD (ACLD). We included 397 patients with CLD who underwent gadoxetic acid-enhanced liver MRI. The FLIS was calculated by summing the points (0-2) of 3 hepatobiliary-phase features: hepatic enhancement, biliary excretion, and portal vein signal intensity. Patients were stratified into 3 groups according to liver fibrosis severity and presence/history of hepatic decompensation: non-ACLD, compensated ACLD (cACLD), and decompensated ACLD (dACLD). SCCD showed excellent intra- and inter-reader agreement. Importantly, SCCD was an independent risk factor for hepatic decompensation in patients with cACLD (per cm; adjusted hazard ratio [aHR] 1.13; 95% CI 1.04-1.23; p= 0.004). Patients with cACLD and a FLIS of 0-3 points and/or a SCCD of >13cm were at increased risk of hepatic decompensation (aHR 3.07; 95% CI 1.43-6.59; p= 0.004). In patients with dACLD, a FLIS of 0-3 was independently associated with an increased risk of ACLF (aHR 2.81; 95% CI 1.16-6.84; p= 0.02), even after adjusting for other prognostic factors. Finally, a FLIS and SCCD-based algorithm was independently predictive of transplant-free mortality and stratified the probability of transplant-free survival (TFS) in ACLD (p <0.001): FLIS 4-6 and SCCD ≤13cm (5-year TFS of 84%) vs. FLIS 4-6 and SCCD >13cm (5-year TFS of 70%) vs. FLIS 0-3 (5-year TFS of 24%). The FLIS and SCCD are simple imaging markers that provide complementary information for risk stratification in patients with compensated and decompensated ACLD. Magnetic resonance imaging (MRI) can be used to assess the state of the liver. Previously the functional liver imaging score, which is based on MRI criteria, was developed as a measure of liver function and to predict the risk of liver-related complications or death. By combining this score with a measurement of spleen diameter, also using MRI, we generated an algorithm that could predict the risk of adverse liver-related outcomes in patients with advanced chronic liver disease.

Evaluation of hepatic function using dynamic contrast-enhanced magnetic resonance imaging in melanocortin 4 receptor-deficient mice as a model of nonalcoholic steatohepatitis

IntroductionMelanocortin 4 receptor-deficient (MC4R-KO) mice fed a high-fat diet (HFD) develop liver pathology similar to human nonalcoholic steatohepatitis (NASH). However, although liver histology and blood biochemistry have been reported, hepatic function has not been evaluated. In the present study, we evaluated hepatic function in MC4R-KO mice fed an HFD using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with gadolinium‑ethoxybenzyl‑diethylenetriamine pentaacetic acid (Gd-EOB-DTPA). Materials and methodsWild type (WT) mice and MC4R-KO mice were fed a standard diet (SD) or an HFD for 20 weeks. The hepatic signal intensity was obtained from DCE-MRI images, and relative enhancement (RE), the time to maximum RE (Tmax), and the half-life of RE elimination (T1/2) were calculated. Histopathological analysis was then performed. ResultsHistological analysis with nonalcoholic fatty liver disease activity score (NAS) revealed that MC4R-KO mice fed an HFD achieved the NAS of 5. There was moderate fibrosis in MC4R-KO mice fed an HFD. DCE-MRI with Gd-EOB-DTPA showed that Tmax and T1/2 were significantly longer in MC4R-KO mice fed an HFD compared with wild type (WT) mice (Tmax, WT, 3.9 ± 0.4 min; MC4R-KO, 7.4 ± 1.5 min; T1/2, WT, 23.7 ± 1.9 min; MC4R-KO, 62.5 ± 18.5 min). Tmax and T1/2 were significantly correlated with histopathologic score (steatosis vs. Tmax, rho = 0.48, P = 0.04; steatosis vs. T1/2, rho = 0.50, P = 0.03; inflammation vs. Tmax, rho = 0.55, P = 0.02; inflammation vs. T1/2, rho = 0.61, P < 0.01; ballooning vs. T1/2, rho = 0.51, P = 0.03;fibrosis vs Tmax, rho = 0.72, P < 0.01; fibrosis vs T1/2, rho = 0.75, P < 0.01). ConclusionsMC4R-KO mice fed an HFD developed obesity and NASH. The liver kinetics of Gd-EOB-DTPA were significantly different in MC4R-KO mice fed an HFD from WT mice, and correlated with the histopathologic score. These results suggest that MC4R-KO mice fed an HFD mimic the hepatic pathology and liver function of human NASH, and therefore might be useful for the study of hepatic dysfunction during the fibrotic stage of NASH.

Change in liver, spleen and bone marrow magnetic resonance imaging signal intensity over time in children with solid abdominal tumors.

Reticuloendothelial system MRI signal hypointensity is common in pediatric oncology patients with solid abdominal tumors. To assess changes in liver, spleen and bone marrow T2-weighted MRI signal intensity over time and their relationship to blood transfusion history in children with solid abdominal tumors. In this retrospective study we measured liver, spleen and bone marrow signal intensity on axial T2-weighted MR images obtained December 2009 through February 2016 in children with hepatoblastoma, neuroblastoma, ganglioneuroblastoma and Wilms tumor. All signal intensity measurements were normalized to paraspinal muscle signal intensity. We used linear mixed models (including a day*day quadratic term) to determine whether organ signal intensity changed over time and whether change was associated with blood transfusion volume or tumor type. We included 133 children (mean age at diagnosis =2.9years); 56 had neuroblastoma, 42 hepatoblastoma, 28 Wilms tumor and 7 ganglioneuroblastoma. Seventy-nine (59.4%) children received transfusions (median: 8 transfusions, range: 1-30; mean volume: 1,148.5mL). Hepatic, splenic and bone marrow signal intensity ratios changed quadratically over time for the study population, initially decreasing and then increasing (P<0.0001). Children receiving less than the mean blood transfusion volume showed no significant change in tissue signal intensity, while those receiving more than the mean volume showed significant changes in signal intensity over time (P<0.0001). Compared to children with Wilms tumor, those with neuroblastoma exhibited significantly lower hepatic (P=0.03) signal intensity ratios. Liver, spleen and bone marrow T2-weighted MRI signal intensity ratios change over time in some pediatric patients with solid abdominal tumors, likely from tissue iron deposition related to blood transfusions and perhaps because of tumor type.

Application of Modified Spin-Echo–based Sequences for Hepatic MR Elastography: Evaluation, Comparison with the Conventional Gradient-Echo Sequence, and Preliminary Clinical Experience

Purpose To (a) evaluate modified spin-echo (SE) magnetic resonance (MR) elastographic sequences for acquiring MR images with improved signal-to-noise ratio (SNR) in patients in whom the standard gradient-echo (GRE) MR elastographic sequence yields low hepatic signal intensity and (b) compare the stiffness values obtained with these sequences with those obtained with the conventional GRE sequence. Materials and Methods This HIPAA-compliant retrospective study was approved by the institutional review board; the requirement to obtain informed consent was waived. Data obtained with modified SE and SE echo-planar imaging (EPI) MR elastographic pulse sequences with short echo times were compared with those obtained with the conventional GRE MR elastographic sequence in two patient cohorts, one that exhibited adequate liver signal intensity and one that exhibited low liver signal intensity. Shear stiffness values obtained with the three sequences in 130 patients with successful GRE-based examinations were retrospectively tested for statistical equivalence by using a 5% margin. In 47 patients in whom GRE examinations were considered to have failed because of low SNR, the SNR and confidence level with the SE-based sequences were compared with those with the GRE sequence. Results The results of this study helped confirm the equivalence of SE MR elastography and SE-EPI MR elastography to GRE MR elastography (P = .0212 and P = .0001, respectively). The SE and SE-EPI MR elastographic sequences provided substantially improved SNR and stiffness inversion confidence level in 47 patients in whom GRE MR elastography had failed. Conclusion Modified SE-based MR elastographic sequences provide higher SNR MR elastographic data and reliable stiffness measurements; thus, they enable quantification of stiffness in patients in whom the conventional GRE MR elastographic sequence failed owing to low signal intensity. The equivalence of the three sequences indicates that the current diagnostic thresholds are applicable to SE MR elastographic sequences for assessing liver fibrosis. © RSNA, 2016.

Chronic acquired hepatocerebral degeneration, pallidal T1 MRI hyperintensity and manganese in a series of cirrhotic patients

Chronic acquired hepatocerebral degeneration (CAHD) is a rare neurological disorder of cirrhotic patients, characterized by parkinsonism and cognitive impairment. A T1 hyperintensity on the globus pallidum due to an accumulation of manganese (Mn) is found in these patients. The aim of the study was to investigate CAHD, Mn and the MRI pallidal signal in a series of cirrhotic patients. The association between pallidal T1 hyperintensity, CAHD, and blood levels of Mn, the effect of orthotopic liver transplantation (OLT) on the MRI signal and neurological findings, and the role of the pallidal signal as a predictor of CAHD were evaluated. Twenty-six out of 90 patients with cirrhosis had pallidal T1 hyperintensity. Seven patients had CAHD. OLT was followed by the disappearance of CAHD and MRI signal in 2/2 patients. The MRI signal disappeared after OLT in 8/13 patients after a median follow-up time of 24months. In the patients who did not undergo OLT, CAHD did not present after a median follow-up time of 18months. The cause of cirrhosis, episodes of acute hepatic encephalopathy and signal intensity were not correlated with CAHD. The blood levels of Mn did not reflect either the MRI signal or CAHD. In conclusion, the pallidal T1 hyperintensity is a prerequisite for the clinical manifestations of CAHD but is not sufficient. The blood levels of Mn as routinely monitored are not a useful marker of Mn burden. The MRI pallidal signal is not a predictor of CAHD.

Clinical and Histologic Implications of Delayed Hepatobiliary Enhancement on Magnetic Resonance Imaging With Gadolinium Ethoxybenzyl Diethylenetriaminepentaacetic Acid

The aim of this study was to evaluate the serial signal changes in hepatobiliary enhancement on gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid or gadoxetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging and its correlation with clinical parameters. Under institutional review board approval, Gd-EOB-DTPA-enhanced magnetic resonance imaging was performed in 77 subjects (21 healthy volunteers and 56 biopsy-proven chronic hepatitis patients), and the signal intensities of the liver and common hepatic ducts (CHD) were measured every 2 minutes up to 50 minutes postcontrast. The associations among hepatic and CHD signals, physiological and hematological variables, histological activity index, and Metavir scores were analyzed with Pearson correlation and multiple linear stepwise regressions. The predictive ability of contrast enhancement index (CEI) of the liver with histological activity index and fibrosis scores at different time points were studied using nonparametric receiver operating characteristic curves. Among the clinical parameters, body weight and body mass index had the highest negative correlation with hepatobiliary enhancement between 2 and 50 minutes postcontrast (P < 0.001). Multiple regressions showed that creatinine level, body weight, and body mass index were independent predictors for both mean hepatic and CHD signal intensity (P < 0.05). Patients with more severe fibrosis or moderate necrosis tended to have lower CEIs than other patients were. The predictive ability of CEI for the best differentiation between no fibrosis and any fibrosis (F ≥ 1) was at 10 minutes postcontrast (area under the receiver operating characteristic curve, 0.797). Delayed hepatobiliary enhancement with Gd-EOB-DTPA could be possibly used for staging liver fibrosis. Contrast enhancement index of the liver at 10 minutes is useful for differentiating between no fibrosis and any degree of fibrosis in chronic hepatitis patients.

Fatty Liver in Acute Pancreatitis

The objective of this research was to study the characteristics of fatty liver (FL) in acute pancreatitis (AP) in 2-dimensional in-phase (IP)/out-of-phase (OP) magnetic resonance imaging (MRI). Fifty patients with AP (23 men, 27 women; mean age, 44 [SD, 12] years [range, 16-73 years]) were included in this retrospective study. Patients' informed consent was waived. All of them performed abdominal MRI within 72 hours of symptom onset and MRI follow-up. The severity of the AP was graded according to the magnetic resonance severity index (MRSI). The MRSI cutoff was 7.0 points between the mild and the severe AP. Fatty liver in MRI was determined by the hepatic signal intensity difference between OP and IP images. Correlations between the severity of FL and MRSI or serum triglyceride levels were analyzed. Of the 50 patients with AP, FL was found in 66% of patients' MRIs. A close correlation can be seen between the difference of liver signal intensities on IP/OP images and the MRSI (r = 0.83, P < 0.001). Close correlations were found between FL appearance on MRI and serum triglyceride levels in both mild (r = 0.93, P < 0.001) and severe AP (r = 0.95, P < 0.001). During follow-up MRI, the appearance of FL decreased following the decrease in MRSI scores and serum triglyceride levels in both mild and severe AP. Fatty liver in AP is frequently observed in MRI. The appearance of FL in MRI may decrease after subsidence of AP.

The value of gadoxetate disodium-enhanced MR imaging for predicting posthepatectomy liver failure after major hepatic resection: A preliminary study

To investigate whether preoperative gadoxetate-disodium-enhanced MR imaging predicts posthepatectomy liver failure (PHLF) in patients who underwent major hepatic resection. Twenty nine patients who underwent preoperative gadoxetate-disodium-enhanced MR imaging and following major hepatic resection were enrolled. Hepatic parenchymal signal intensity (SI) on pre-contrast T1-weighted imaging and 20min hepatocyte phase was measured at each of the four liver segments by two observers using region of interest measurements. The mean value was calculated and used at each phase. The relative contrast enhancement index (RCEI) was calculated: (20min hepatocyte phase SI-pre-contrast SI)/pre-contrast SI. PHLF was determined by the International Study Group of Liver Surgery 2011 guidelines. Correlation analysis was performed between preoperative liver function test and RCEI. Diagnostic accuracy of RCEI for predicting PHLF was calculated with receiver operating characteristic curve analysis. The reproducibility of the RCEI measurement was evaluated. There was a significant correlation between preoperative albumin (r=0.496, P=0.006), T-bilirubin (r=-0.383, P=0.041), and RCEI. Seven patients (24%) experienced PHLF, and one of these patients (3%) died. The diagnostic accuracy of RCEI was 0.838 (sensitivity 85.7%, specificity 77.3%, cut-off value: 0.7508, 95% confidence interval: 0.654, 0.947). The 95% limits of agreement and ICC between repeated RCEI measurements were 18.4% of the mean and 0.94, respectively, and between RCEI measurements by the two observers were 21.7% and 0.929, respectively. Our results show that preoperative gadoxetate-disodium-enhanced MR imaging can predict PHLF in patients who underwent major hepatic resection.

Contrast-enhanced ultrasound to evaluate the severity of chronic hepatitis C

Background Non-invasive techniques are being developed to assess the severity of liver disease. Haemodynamic changes in the hepatic circulation during the development of liver disease can be evaluated with contrast-enhanced ultrasound. Aim To evaluate the possible correlation between ultrasound contrast-agent transit times and different stages of chronic hepatitis C. Patients Sixteen patients with clinically evident hepatitis C virus-related cirrhosis, 22 non-cirrhotic patients with chronic hepatitis C and 14 controls with no clinical evidence of liver disease were studied. Methods Contrast-enhanced hepatic ultrasonography was performed with a sulphur hexafluoride-filled microbubble contrast agent, and time curves of hepatic vein signal intensity were analysed to determine the time of enhancement onset (hepatic vein arrival time) and peak enhancement (hepatic vein peak enhancement). Results Hepatic vein arrival time in cirrhotic patients was significantly shorter ( p < 0.001) than in non-cirrhotic patients and controls. Within the group with chronic hepatitis C, METAVIR scores of fibrosis and necro-inflammatory changes had no significant effect on hepatic vein arrival times. Conclusion Analysis of the time of onset of ultrasound contrast enhancement of the hepatic vein appears to be a simple, non-invasive method for reliably excluding cirrhosis with signs of portal hypertension, but not for assessing the severity of either chronic hepatitis C or cirrhosis.

Transient Hepatic Intensity Differences: Part 1, Those Associated with Focal Lesions

The purpose of our study was to evaluate, on MRI, transient hepatic signal intensity differences (THID) that have already been seen on CT as transient hepatic attenuation differences (THAD) and to show the range of appearance of such arterial phenomena, when associated with focal lesions, in an effort to correlate morphology, cause, and pathogenesis. Hepatic arterial phenomena visualized on MRI should be known and recognized to avoid incorrect diagnoses and to improve the characterization of focal liver lesions because their shape can lead to an understanding of pathogenetic mechanisms.

Transient Hepatic Intensity Differences: Part 2, Those Not Associated with Focal Lesions

The purpose of our study was to evaluate and to show the range of appearance of transient hepatic signal intensity differences when not associated with focal lesions, and to correlate morphology, cause, and pathogenesis. Hepatic arterial phenomena, visualized on MRI and CT, must be considered important signs of underlying liver disorders, which these phenomena contribute to evaluate. Accordingly, the hepatic arterial phase must always be performed on MRI as well as on CT, even if no focal lesion is expected.

Dual Gradient-Echo In-Phase and Opposed-Phase Hepatic MR Imaging: A Useful Tool for Evaluating More Than Fatty Infiltration or Fatty Sparing

A T1-weighted gradient-echo in-phase and opposed-phase sequence has become a routine part of every hepatic magnetic resonance (MR) imaging protocol. Although this sequence is primarily used to identify common pathologic conditions, such as diffuse or focal steatosis and focal fatty sparing, it is also helpful in detection of pathologic entities associated with T2* effects owing to the double-echo approach. Thus, pathologic conditions such as hemochromatosis or hemosiderosis can be identified and characterized with a high level of confidence. In cases of iron storage disease, the hepatic parenchymal signal intensity decreases on the image with the longer echo time due to the continued decay of the transverse magnetization. In addition, susceptibility artifacts can be easily detected and characterized with in-phase and opposed-phase MR imaging. Metallic objects demonstrate a larger susceptibility artifact on the image with the second or longer echo time, which is usually the in-phase image. Finally, intrahepatic pneumobilia can be identified with the T1-weighted gradient-echo in-phase and opposed-phase sequence because gas also causes a susceptibility artifact, which is more pronounced on the image with the longer echo time. A complete understanding of both the chemical shift cancellation artifact and the T2* effects of the in-phase and opposed-phase sequence is important for correct interpretation of hepatic MR images.

Hepatic Macrosteatosis: Predicting Appropriateness of Liver Donation by Using MR Imaging—Correlation with Histopathologic Findings

To retrospectively evaluate the diagnostic performance of magnetic resonance (MR) imaging in predicting the appropriateness of liver donation in potential living liver donors by using histopathologic results as the reference standard. This study was approved by institutional review board; all patients gave informed consent for the use of MR data for future research. Fifty-seven potential liver donors (40 male, 17 female; age range, 17-57 years; mean age, 32 years) underwent dual-echo 1.5-T MR imaging. Two radiologists qualitatively graded each MR image, with consensus for disagreements. Livers were assigned one of three degrees of hepatic steatosis on the basis of changes in hepatic signal intensity (SI) between in-phase and opposed-phase images. For quantitative analysis, a third radiologist calculated mean hepatic and mean splenic SI by averaging 25 hepatic regions of interest and three splenic regions of interest. Relative SI decrease (RSID) in the liver on opposed-phase images compared with in-phase images was calculated. Linear regression analysis was used to correlate RSID with the degree of total steatosis, macrosteatosis, and microsteatosis. Diagnostic performance for predicting the appropriateness of liver donation was analyzed. Histologic findings of macrosteatosis resulted in 52 patients being categorized as appropriate donors, with the remaining five being categorized as inappropriate donors. RSID was correlated with total steatosis (r = 0.850). When the RSID criterion for inappropriateness of liver donation was set at 20%, the sensitivity, specificity, and accuracy were 100%, 92.3%, and 93%, respectively. When RSID was used, four livers that had been misclassified as inappropriate for transplantation were found to have microsteatosis of various degrees and a less than moderate degree of macrosteatosis at histologic analysis. Qualitative and quantitative analyses were comparably accurate. When an RSID criterion of less than 20% was used, dual-echo MR imaging facilitated the correct prediction of appropriateness of liver donation in 53 of 57 patients.

MR Imaging of Hepatocellular Carcinoma Arising in Genetic Hemochromatosis

A case of a 51-year-old male with previously unsuspected genetic hemochromatosis (GH) associated with hepatocellular carcinoma (HCC), for which MR imaging was useful in diagnosis, is presented. Contrast-enhanced ultrasonography depicted a mass in segment 8 of the liver and a liver tumor was suspected. The mass could not be revealed on unenhanced or enhanced CT examination. MR imaging with unenhanced T1-weighted FLASH and T2-weighted gradient echo sequences clearly depicted the tumor; the tumor appeared hyperintense against a background of low hepatic signal intensity caused by iron overload. The iron-overloaded liver provided a natural source of paramagnetic contrast for detection of HCC. Studies are required to further assess the accuracy of these sequences in detection of HCC in patients with GH.

Sinusoidal spread of liver metastases from renal cell carcinoma: simulation of diffuse liver disease on MR imaging

Rarely, hepatic metastases can simulate hepatic infiltrative diseases. We present a case of a patient with advanced metastatic renal cell carcinoma who developed hepatomegaly and clinical signs of hepatocellular injury. On magnetic resonance imaging, the injury simulated a diffuse process, e.g., acute fulminant viral or chemical hepatitis or drug toxicity. Despite its high resolution, magnetic resonance imaging might not depict focal lesions in patients with extensive metastases. In correlation with clinical history, malignant disease should be considered when diffusely abnormal hepatic signal intensity is noted.

Superparamagnetic iron oxide-mediated hepatic signal intensity change in patients with and without cirrhosis: pulse sequence effects and Kupffer cell function.

To analyze superparamagnetic iron oxide (SPIO)-mediated hepatic signal intensity change in cirrhotic and noncirrhotic liver and to investigate the relationship between pulse sequence effects in SPIO-enhanced magnetic resonance (MR) imaging for hepatic cirrhosis. Twelve patients with and 12 patients without cirrhosis underwent T2-weighted fast spin-echo, T2*-weighted gradient-echo (GRE), and T1-weighted GRE MR imaging before and twice (early and late phase) after SPIO administration. To assess the effect of SPIO, postcontrast relative signal-to-noise ratio (SNR) changes were statistically analyzed with repeated measurements analysis of variance for each pulse sequence. No interaction was shown between groups and data time points for any pulse sequence. There was no significant difference in mean hepatic relative SNR change on T2-weighted fast spin-echo images between the cirrhotic group and noncirrhotic group (-38.6% and -40.7%, early phase; -42.2% and -49.6%, late phase, respectively). For GRE images, statistically significant differences in mean hepatic relative SNR change were found between the cirrhotic group and noncirrhotic group (-14.2% and -44.5%, early phase; -28.5% and -56.4%, late phase on T2*-weighted GRE images (P <.001); 31.8% and 12.9%, early phase; 23.8% and 2.2%, late phase on T1-weighted GRE images (P <.05), respectively. Decreased overall phagocytic activity in cirrhotic liver is more likely due to Kupffer cell dysfunction than to Kupffer cell depletion, since magnetic susceptibility effects on T2*-weighted GRE images depend on intracellular SPIO cluster size.

CT AND MR IMAGING OF THE LIVER. Clinical importance of nutritional status

Purpose: In an experimental study in rats a correlation between nutritional status and hepatic attenuation in CT and signal intensities in MR imaging was shown. Is physiological nutritional status of importance in clinical CT and MR imaging? Material and Methods: In a cross-over study including 12 healthy volunteers (6 women and 6 men, mean age 34 years), CT and MR imaging of the liver were performed with nutritional status at three different levels, i.e., normal, fasting and after glycogen-rich meals. CT and MR were performed on clinical imaging systems and hepatic attenuation and signal intensity, respectively, were assessed. In MR, T1-weighted, proton density-weighted and T2-weighted pulse-sequences were used. Results: In CT there were significantly (p<0.01) higher liver attenuations in normal nutritional status and after glycogen rich-meals compared to the fasting condition. The difference between fasting and glycogen-rich meals were 10.5 HU for men, 7.4 for women and mean 8.8 HU for all 12 volunteers. In MR imaging the differences were small and non-significant. The results of this study are in accordance with an earlier experimental study in rats. Conclusion: In CT it may be of importance not to have patients in a fasting condition as it lowers the attenuation in normal liver tissue. The findings are important for planning of clinical studies where hepatic attenuation will be assessed and may be of some importance in clinical CT. In MR imaging the results indicate that the nutritional status is of less importance.

Synthesis, characterization, and imaging performance of a new class of macrocyclic hepatobiliary MR contrast agents.

To investigate the effect of substituent lipophilicity, substituent position, and overall charge on the hepatobiliary clearance and tolerance of a series of aromatic ring-containing macrocyclic Gd chelates to select a candidate compound for evaluation as a hepatobiliary imaging agent. Hepatobiliary clearance was studied in rats. Tissue distribution and tolerance were studied in mice. Imaging was performed in cats, rabbits, and Rhesus monkeys using T1-weighted pulse sequences or T1-weighted breath-hold pulse sequences. All the compounds were excreted bimodally. Gd-2,5-BPA-DO3A (15d) was found to have the optimal combination of hepatobiliary clearance (47% in rats, 29% in mice) and tolerance (minimum lethal dose 5.0 mmol/kg). Initial imaging studies in cats demonstrated the feasibility of Gd-2,5-BPA-DO3A for hepatic imaging. In rabbits with implanted VX-2 adenocarcinoma as a model for metastatic liver disease, Gd-2,5-BPA-DO3A provided sustained hepatic signal intensity (SI) enhancement and lesion conspicuity over a 120-minute imaging time course. In Rhesus monkeys with normal liver function, Gd-2,5-BPA-DO3A afforded sustained hepatic SI enhancement and a time-dependent increase in gallbladder SI over the entire 90-minute imaging time course. Gd-2,5-BPA-DO3A provides dramatic and sustained SI enhancement of hepatic tissue in cats, rabbits, and Rhesus monkeys that was superior in all respects to the extracellular space MRI agent, Gd-HP-DO3A, that was employed as a control.

Evaluation of portal MR angiography using superparamagnetic iron oxide.

The purpose of our research was to determine the effects of superparamagnetic iron oxide on MR imaging of the portal venous system. Eight piglets were examined in deep anaesthesia and respiratory arrest using a time-of-flight magnetic resonance fast low angle shot, two-dimensional angiography sequence at 1.5T, MR angiograms were acquired precontrast and after intravenous administration of a cumulative dose of 10, 20 and 40 mumol/kg SHU 555A, a superparamagnetic iron oxide contrast agent for MR imaging with a particle size of 60 nm. For each dose, two subsequent sets of scans were obtained and reconstructed by a maximum-intensity-projection algorithm. Hepatic parenchymal and portal venous signal intensities were measured, and portal vein contrast calculated for each set of scans. All examinations were visually rated as to portal vein contrast and homogeneity by two blinded observers. Receiver operating characteristics of both observers were analyzed. The contrast agent reduced hepatic parenchymal signal in a dose-dependent way. After a cumulative dose of 10 mumol iron oxide, hepatic parenchymal signal intensity decreased to 63 +/- 6% (average of measurements at 4 and 14 minutes, mean +/- standard error of the mean), after 20 mumol to 24 +/- 3%, and after 40 mumol to 12 +/- 1% of control. Intravascular signal in the left main portal vein branch increased to 117 +/- 6%, 127 +/- 10%, and 133 +/- 9% of control, respectively. The contrast-to-noise ratio of the portal vein improved (521 +/- 90%, 891 +/- 178%, and 995 +/- 201% of control in the left portal vein main branch). Intravascular signal intensities increased slightly. The combined effect improved contrast of the portal vein stem and its branches. Receiver operating characteristics analysis documented dose-dependency of contrast medium effects on portal venous contrast and intravascular homogeneity. Visual rating also indicated a positive effect on portal venous contrast. The superparamagnetic iron oxide agent improved portal venous contrast with surrounding hepatic parenchyma in this normal animal model, and could potentially result in more accurate diagnosis of portal venous pathology.