MRI of the liver

Preclinical Long-term Magnetic Resonance Imaging Study of Silymarin Liver-protective Effects

BACKGROUND AND AIMS

Efficacy evaluations with preclinical magnetic resonance imaging (MRI) are uncommon, but MRI in the preclinical phase of drug development provides information that is useful for longitudinal monitoring. The study aim was to monitor the protective effectiveness of silymarin with multiparameter MRI and biomarkers in a thioacetamide (TAA)-induced model of liver injury in rats. Correlation analysis was conducted to assess compare the monitoring of liver function by MRI and biomarkers.

METHODS

TAA was injected three times a week for 8 weeks to generate a disease model (TAA group). In the TAA and silymarin-treated (TAA-SY) groups, silymarin was administered three times weekly from week 4. MR images were acquired at 0, 2, 4, 6, and 8 weeks in the control, TAA, and TAA-SY groups.

RESULTS

The area under the curve to maximum time (AUC_tmax) and T₂* values of the TAA group decreased over the study period, but the serological markers of liver abnormality increased significantly more than those in the control group. In the TAA-SY group, MRI and serological biomarkers indicated attenuation of liver function as in the TAA group. However, pattern changes were observed from week 6 to comparable levels in the control group with silymarin treatment. Negative correlations between either AUC_tmax or T₂* values and the serological biomarkers were observed.

CONCLUSIONS

Silymarin had hepatoprotective effects on TAA-induced liver injury and demonstrated the usefulness of multiparametric MRI to evaluate efficacy in preclinical studies of liver drug development.

Chronic inflammatory demyelinating polyneuropathy with anti-contactin-associated protein 1 antibody and bile duct hamartomas in the liver: a case report

Background

Autoantibodies targeting node of Ranvier proteins are rarely reported in China.

Case presentation

We present the case of a 66-year-old Chinese man who concomitantly developed chronic inflammatory demyelinating polyneuropathy with anti-contactin-associated protein 1 antibody and bile duct hamartomas in liver, which are rarely reported in China. The man presented with chronic progressive sensory and motor symptoms, bilateral periphery facial paralysis, and protein–cell dissociation of cerebrospinal fluid. Nerve conduction study indicated demyelinating neuropathy. Enhanced magnetic resonance imaging of the liver showed diffuse intrahepatic lesions, which were considered as bile duct hamartomas in the liver. He was suspected as having chronic inflammatory demyelinating polyneuropathy and treated with intravenous immunoglobulin and prednisone. However, his condition got worse. One month later, he was diagnosed with chronic inflammatory demyelinating polyneuropathy associated with anti-contactin-associated protein 1 antibody. He received high-dose methylprednisolone, followed by standard plasma exchange and rituximab therapy. His sensory and motor manifestations were significantly improved at 1 year of follow-up.

Conclusions

This case reminds clinicians to be aware of antiparanodal antibodies, which are associated with specific phenotypes and therapeutic response.

Responsive Trimodal Probes for In Vivo Imaging of Liver Inflammation by Coassembly and GSH-Driven Disassembly

Noninvasive in vivo imaging of hepatic glutathione (GSH) levels is essential to early diagnosis and prognosis of acute hepatitis. Although GSH-responsive fluorescence imaging probes have been reported for evaluation of hepatitis conditions, the low penetration depth of light in liver tissue has impeded reliable GSH visualization in the human liver. We present a liver-targeted and GSH-responsive trimodal probe (GdNPs-Gal) for rapid evaluation of lipopolysaccharide- (LPS-) induced acute liver inflammation via noninvasive, real-time in vivo imaging of hepatic GSH depletion. GdNPs-Gal are formed by molecular coassembly of a GSH-responsive Gd(III)-based MRI probe (1-Gd) and a liver-targeted probe (1-Gal) at a mole ratio of 5/1 (1-Gd/1-Gal), which shows high r ₁ relaxivity with low fluorescence and fluorine magnetic resonance spectroscopic (¹⁹F-MRS) signals. Upon interaction with GSH, 1-Gd and 1-Gal are cleaved and GdNPs-Gal rapidly disassemble into small molecules 2-Gd, 2-Gal, and 3, producing a substantial decline in r ₁ relaxivity with compensatory enhancements in fluorescence and ¹⁹F-MRS. By combining in vivo magnetic resonance imaging (¹H-MRI) with ex vivo fluorescence imaging and ¹⁹F-MRS analysis, GdNPs-Gal efficiently detect hepatic GSH using three independent modalities. We noninvasively visualized LPS-induced liver inflammation and longitudinally monitored its remediation in mice after treatment with an anti-inflammatory drug, dexamethasone (DEX). Findings highlight the potential of GdNPs-Gal for in vivo imaging of liver inflammation by integrating molecular coassembly with GSH-driven disassembly, which can be applied to other responsive molecular probes for improved in vivo imaging.

Magnetic resonance microscopy of renal and biliary abnormalities in excised tissues from a mouse model of autosomal recessive polycystic kidney disease

Polycystic kidney disease (PKD) is transmitted as either an autosomal dominant or recessive trait and is a major cause of renal failure and liver fibrosis. The cpk mouse model of autosomal recessive PKD (ARPKD) has been extensively characterized using standard histopathological techniques after euthanasia. In the current study, we sought to validate magnetic resonance microscopy (MRM) as a robust tool for assessing the ARPKD phenotype. We used MRM to evaluate the liver and kidney of wild-type and cpk animals at resolutions <100 μm and generated three-dimensional (3D) renderings for pathological evaluation. Our study demonstrates that MRM is an excellent method for evaluating the complex, 3D structural defects in this ARPKD mouse model. We found that MRM was equivalent to water displacement in assessing kidney volume. Additionally, using MRM we demonstrated for the first time that the cpk liver exhibits less extensive ductal arborization, that it was reduced in volume, and that the ductal volume was disproportionately smaller. Histopathology indicates that this is a consequence of bile duct malformation. With its reduced processing time, volumetric information, and 3D capabilities, MRM will be a useful tool for future in vivo and longitudinal studies of disease progression in ARPKD. In addition, MRM will provide a unique tool to determine whether the human disease shares the newly appreciated features of the murine biliary phenotype.

Evaluation of hepatic fibrosis with portal pressure gradient in rats

MRI has the potential of providing a noninvasive assessment of liver pathology. This work introduces a portal pressure gradient (PPG) model derived from fluid mechanics, where the PPG is proportional to the average velocity and inversely proportional to the vessel area in the upper part of portal vein. Using a phase-contrast spoiled gradient echo sequence, the PPG model was verified in a phantom study and was tested in an animal study using 35 rats with various degrees of hepatic fibrosis induced by carbon tetrachloride (CCl(4)). Histological examination was conducted to determine the severity of hepatic fibrosis. The fibrosis score monotonically increased with the duration of CCl(4) treatment. The PPG was highly correlated with nonzero fibrosis scores (r(2) = 0.90, P < 0.05). There was a significant difference between control and cirrhosis groups (P < 0.0006, alpha < 0.0018). The difference between control and fibrosis (noncirrhosis) groups (P < 0.002, alpha < 0.006) was also significant. Without the administration of any contrast agent, the MRI-PPG approach shows promise as a noninvasive means of evaluating liver fibrosis.

Hepatocellular carcinoma: conventional MRI findings including gadolinium-enhanced dynamic imaging

A great variety of MR pulse sequences for hepatocellular carcinomas (HCCs) are now available. In this article, we reviewed the current MR imaging techniques that are routinely used for hepatic imaging, and described the optimization of these sequences as well as the utility and characteristics of each sequence for the accurate diagnosis of HCCs. Then, we reviewed various MR imaging findings of advanced and early HCCs with emphasis on signal intensity and hemodynamic patterns. Finally, we described the value of multi-arterial-phase contrast-enhanced dynamic MR imaging of the whole liver with excellent temporal resolution for evaluating transitional hemodynamics of hepatic lesions during the six arterial phases.

Assessment of the optimum section thickness for the estimation of liver volume using magnetic resonance images: a stereological gold standard study

Estimation of liver volume using magnetic resonance (MR) images has been described previously. We have, however, not found a gold standard study, which analyzes the effect of section thickness on the estimation of liver volume. In the present study, five normal cadaveric livers were scanned in the horizontal plane using a 1.5 T MR machine (Signa 1.5T SYS#GEMSOW General Electronic, Wisconsin, USA). Consecutive sections at a thickness of 10, 7.5, 5 and 2.5 mm were used to estimate the total volume of the livers by means of the Cavalieri principle. The point counting and planimetry were used for the volume estimates. With a view to evaluating the accuracy of two techniques, all the estimations were done by the same observer. The estimated volumes concur with the actual volume of the livers obtained by the fluid displacement technique (p > 0.05). However, the section thickness has an over- or under-projection effect on the estimated volume. The obtained volume estimation results were analyzed to reveal the deviation principles of the estimates based on the section thickness. The most suitable section thickness for the liver volume estimation was assessed to be 4-5 mm. There were no significant differences between the estimation results of two methods (p > 0.05). The point-counting technique did, however, take less time than planimetry for estimating liver volume from MR images. Results also showed that the effect of section thickness on volume estimates using the two approaches could not be omitted and the values obtained could be calibrated using the proposed regression formula presented in this study.

A general approach to the management of chronic hepatitis C

Hepatitis C virus (HCV) is the most common chronic blood-borne infection in the United States. Although many will live a lifetime unaffected by the consequence of chronic infection, some will develop cirrhosis and end-stage liver disease. Given the broad spectrum of disease outcomes, developing a careful systematic approach to infected patients is fundamental. This allows the practitioner to provide accurate education, develop treatment plans, and determine appropriate health care maintenance and screening. Care for the patient with HCV must be individualized. In this regard,the purpose of this article is not to present a guideline, but to provide a foundation of information that will aid the provider and patient in developing an appropriate treatment strategy.

Oral manganese for liver imaging at three different field strengths

RATIONALE AND OBJECTIVES

To study the magnetic resonance imaging signal intensity of the liver and gall bladder before and after ingestion of a new oral manganese containing contrast medium at three different field strengths.

MATERIALS AND METHODS

Twelve healthy male volunteers (mean age, 24.9 years; range, 20-39 years) underwent abdominal magnetic resonance imaging (T(2)W COR, T(1)W COR, T(1)W TRA) at 0.23 T, 0.6 T, and 1.5 T before and after the contrast administration. The duration of fasting was identical before the two studies. Volunteers were randomized into two equal groups (n = 6) to ingest either half or full strength CMC-001 providing either 0.8 or 1.6.g MnCl(2) plus absorption promoters. The CMC-001 dose was dissolved in 400 mL water and ingested 2.5 hours before imaging. The resulting images were evaluated with regard to visualization of the liver and the gall bladder by three radiologists. The signal intensity of the liver was also measured. Blood and urine samples were collected before and after ingestion of CMC-001.

RESULTS

The intake of CMC-001 caused a significant increase in the signal intensity of the liver at all three field strengths and at both dosages (up to 90%) on the T(1)W images. The internal structure of the liver was significantly better delineated. The bile in gall bladder was bright after ingestion of the low dose, but dark after the full dose. On the T(2)W images, CMC-001 lowered the signal intensity of liver with up to 30%. CMC-001 had a slight metallic taste, but of no importance according to the volunteers. No systematic adverse reactions caused by the contrast medium were registered. No changes in the blood levels of various routine parameters were measured.

CONCLUSION

It is possible to increase the signal intensity of the liver significantly by oral intake of essential nutritional elements including manganese. The imaging window is more than 2 hours.

Estudo comparativo das seqüências rápidas ponderadas em T2, utilizando-se sincronização respiratória, apnéia, supressão de gordura, bobina de corpo e bobina de sinergia para a avaliação do fígado pela ressonância magnética

OBJETIVO: Comparar, qualitativa e quantitativamente, as imagens de ressonância magnética do fígado, ponderadas em T2, utilizando-se seqüências rápidas, diferenciadas pela técnica de controle respiratório, pela utilização de supressão de gordura e pelo tipo de bobina de radiofreqüência. MATERIAIS E MÉTODOS: Estudo prospectivo em 71 pacientes consecutivos, sendo realizadas seis seqüências para comparação: 1) supressão de gordura com sincronização respiratória e bobina de corpo; 2) supressão de gordura em apnéia e bobina de corpo; 3) sem supressão de gordura com sincronização respiratória e bobina de corpo; 4) sem supressão de gordura em apnéia e bobina de corpo; 5) com supressão de gordura com sincronização respiratória e bobina de sinergia; 6) com supressão de gordura em apnéia e bobina de sinergia. A avaliação qualitativa foi baseada em três critérios: detecção de determinadas estruturas anatômicas do fígado, definição dos contornos hepáticos, e presença de artefatos de respiração. A análise quantitativa foi obtida através da relação das intensidades de sinal do fígado e do ruído de fundo. RESULTADOS: O valor médio dos índices globais de qualidade de imagem para cada uma das seis seqüências supracitadas foi de 7,8, 4,6, 7,9, 5,2, 6,7 e 4,6, respectivamente. As seqüências obtidas com sincronização respiratória apresentaram melhor qualidade de imagem e relação sinal/ruído superiores às seqüências com apnéia (p < 0,001). As seqüências realizadas com e sem supressão de gordura apresentaram qualidade de imagem e relação sinal/ruído semelhantes (p > 0,05). As seqüências obtidas com bobina de sinergia apresentaram qualidade de imagem semelhante (p > 0,05) e relação sinal/ruído inferior àquelas com bobina de corpo (p < 0,001). CONCLUSÃO: Associando-se as análises qualitativa e quantitativa das imagens, as melhores seqüências foram aquelas obtidas com sincronização respiratória e bobina de corpo, utilizando-se ou não supressão de gordura.

Comparison of two volumetric techniques for estimating liver volume using magnetic resonance imaging

PURPOSE

To compare the conventional technique of manual planimetry with the point counting technique for estimating liver volume from magnetic resonance imaging (MRI) data.

MATERIALS AND METHODS

This study comprised abdominal MR examinations of 38 consecutive patients. Evaluation of the images showed that liver size appeared normal in 27 patients and increased in 11. Liver volume was estimated using the techniques of planimetry and point counting. Both techniques were used in combination with the Cavalieri method of modern design stereology. A systematic slice sampling procedure was performed to estimate liver volumes using both volumetric techniques. The point counting technique was optimized by altering the point spacing of the grid. The agreement between the two techniques was found. Measurement repeatability of both volumetric techniques was also evaluated.

RESULTS

Both techniques allowed the same degree of optimization through the procedure of systematic section sampling. The application of a point spacing of 2.5 cm reduced the time measurement by a factor of 3.5 in relation with the time needed with planimetry. An excellent agreement was observed between the two volumetric techniques with mean differences (+/-SD) of 2.4 +/- 41.6 cm(3) and 8.5 +/- 49.8 cm(3) for the patients presenting normal and increased liver sizes, respectively. Both techniques were highly reproducible.

CONCLUSION

The point counting technique could be considered a more efficient approach than planimetry for estimating liver volume from MRI, due to its speed and simplicity.

Single imaging modality evaluation of living donors in liver transplantation: magnetic resonance imaging

BACKGROUND

Liver graft size, anatomy of the bile duct and the vascular inflow and outflow are essential for living related liver transplantation (LRLT). Preoperative delineation of those variations that would change the operative procedure to achieve a successful result especially in an emergency condition.

PURPOSE

Our aim was to develop a rapid and noninvasive imaging diagnostic method for the detection of anatomical variants that is mandatory for a safe operation when selecting potential liver transplant living donors. We used a different magnetic resonance (MR) imaging technique, which enabled to us to exploit the anatomical landmark of the liver, signal enhancement of blood flow in the abdomen, and the intrahepatic biliary routes inside the liver. Then, with the help of Advantage Window workstation reconstruction, the reconstructed single vascular or biliary systems were displaced in a three-dimensional fashion and the whole examination finished within 30 min.

METHODS

Modification of the standard MR technique was performed on a superconductive 1.5T whole body image scanner, MR arteriogaphy, venography, and cholangiography with three-dimensional reconstruction in evaluating the anatomy of the hepatic arteries, hepatic veins, portal venous system, bile ducts, and liver size in potential liver transplant living donors. These anatomical structures were compared with traditional imaging methods.

RESULTS

In all 38 cases, as well as delineation of the portal vein detail to the segmental level was satisfactorily obtained in this MR study. The images were well displayed in a three-dimensional fashion, which had good correlation with images from traditional imaging modalities and operative findings. In 86.8% cases, the MR arteriography was well matched with the celiac angiography. Of those 17 operative cases, estimation of liver volume was well correlated with the liver graft within 3.9-12.5% variation. In the major hepatic vein, we obtained 100% accuracy and 88.2% in the minor branches. Of 12 donors received intraoperative cholangiography during liver donation, good correlation of biliary anatomy was achieved. One donor was excluded from graft donation due to the complicated arterial supply to the left liver. According to the anatomical variation, surgical procedures in graft harvesting and anastomosis were readjusted and no major complications were found in those donors and all recipients survived after liver transplantation.

CONCLUSION

MR volumetry, venography, angiography, and cholangiography with three-dimensional reconstruction is sufficient for all major imaging evaluation. It may replace the traditional conventional catheter angiography, computed tomography, sonography and endoscopic retrograde cholangiography as a single investigation in the evaluation of the potential liver transplant donors. Angiography is only valuable in suboptimal cases and intraoperative cholangiography is only performed in biliary ductile variants.

Improving the detectability of focal liver lesions on T2-weighted MR images: ultrafast breath-hold or respiratory-triggered thin-section MRI?

The purpose of this study was to determine whether a respiratory-triggered (RT) T2-weighted turbo spin-echo (TSE) sequence with thin section can improve the detectability of focal liver lesions compared to a breath-hold (BH) T2-weighted TSE sequence. In 25 patients an RT TSE with 8-mm sections (8-TSE RT) and 5-mm sections (5-TSE RT) and a BH TSE sequence with 8-mm sections (8-TSE BH) were performed. Forty-one focal liver lesions (mean: 1.8 +/- 1.2 cm; 14 lesions < or =1 cm; 27 lesions >1 cm) were evaluated. The 5-TSE RT was significantly better in lesion detection compared to the 8-TSE BH sequence for all sizes of lesions (40/41 vs. 33/41; P = 0.014). For lesions >1 cm no relevant differences in the detection rate of the sequences were found (8-TSE RT, 26/27; 5-TSE RT, 26/27; 8-TSE BH, 25/27), for lesions < or =1 cm the 5-TSE RT provided significantly better sensitivity than the 8-TSE BH (14/14 vs. 8/14, P = 0.015). The results of this study suggest that lesion detection could be significantly improved by using an RT TSE sequence with thin sections compared with a BH TSE sequence.

Superior diagnostic strength of combined contrast enhanced MR-angiography and MR-imaging compared to intra-arterial DSA in liver transplantation candidates

To evaluate the diagnostic value of combined contrast enhanced MRA (ce-MRA) and MRI compared to that of intra-arterial DSA (i.a.DSA) in liver transplantation, transjugular porto-systemic (TIPSS) and spleno-renal shunt candidates. 50 patients in the workup for liver transplantation underwent ce-MRA/MRI and i.a.DSA within a three days interval. Both examinations were assessed with respect to vessel anatomy and patency of the arterial, portal venous, porto-systemic collateral and systemic venous system. The results were compared with the intra-operative findings when available. Malignancy detection in ce-MRA/MRI and i.a.DSA were compared. There are no significant differences for the arterial part of the vascular supply to the liver that is important for transplantation. Although the differences for the portal system are not significant, the difference between the two techniques is of clinical importance because i.a.DSA failed to detect portal vein occlusion in 4 patients. Ce-MRA is significantly better for the detection of collaterals (p < 0.001) and the assessment of the inferior vena cava, the hepatic and the renal veins (p < 0.001). Although the detection of liver malignancy is poor in both techniques, ce-MRA/MRI is superior to i.a.DSA. This study shows that a one step diagnostic approach with a combination of ce-MRA and MRI is a valuable radiological tool with a superior diagnostic strength compared to i.a.DSA in the liver transplantation and shunt candidate. Therefore, ce-MRA/MRI should replace i.a.DSA in these patients groups.

Recommendations for the outpatient surveillance of renal transplant recipients. American Society of Transplantation

Many complications after renal transplantation can be prevented if they are detected early. Guidelines have been developed for the prevention of diseases in the general population, but there are no comprehensive guidelines for the prevention of diseases and complications after renal transplantation. Therefore, the Clinical Practice Guidelines Committee of the American Society of Transplantation developed these guidelines to help physicians and other health care workers provide optimal care for renal transplant recipients. The guidelines are also intended to indirectly help patients receive the access to care that they need to ensure long-term allograft survival, by attempting to systematically define what that care encompasses. The guidelines are applicable to all adult and pediatric renal transplant recipients, and they cover the outpatient screening for and prevention of diseases and complications that commonly occur after renal transplantation. They do not cover the diagnosis and treatment of diseases and complications after they become manifest, and they do not cover the pretransplant evaluation of renal transplant candidates. The guidelines are comprehensive, but they do not pretend to cover every aspect of care. As much as possible, the guidelines are evidence-based, and each recommendation has been given a subjective grade to indicate the strength of evidence that supports the recommendation. It is hoped that these guidelines will provide a framework for additional discussion and research that will improve the care of renal transplant recipients.

Phase II double-blind, dose-ranging clinical evaluation of gadobenate dimeglumine in focal liver lesions: with analysis of liver and kidney signal change on early and delayed imaging

To evaluate the effect of contrast dose using gadobenate dimeglumine, 30 patients with focal liver lesions documented by computed tomography or ultrasound were studied by magnetic resonance imaging at 1.5 T. Patients received one of four doses of gadobenate dimeglumine (0.025, 0.05, 0.1, or 0.2 mmol/kg) or saline. The order of dosage was randomized, with both the physician and patient blinded to the administered dose. Scans were obtained before, immediately following injection, and after 80 minutes of delay. Enhancement effects were quantified by region of interest measurements. Films were also reviewed in a randomized prospective fashion by an abdominal radiologist blinded to contrast dose and diagnosis. Higher doses led to a statistically significant improvement in enhancement of normal liver, both on immediate (P = 0.01 for the comparison of 0.1 and 0.2 mmol/kg immediately post-contrast) and delayed scans (P = 0.003 for the same comparison). Liver-lesion contrast-to-noise ratio also increased with dose, although results for most comparisons by dose were not statistically significant. Scans following gadobenate dimeglumine injection were judged to provide additional diagnostic confidence sufficient to affect patient management in 10 of 24 cases. In seven cases this information was provided by dynamic scans, in one case by delayed scans, and in two cases by both dynamic and delayed scans. In 2 of the 10 cases the dose was 0.025 mmol/kg, in 2 cases 0.05 mmol/kg, in 3 cases 0.1 mmol/kg, and in 3 cases 0.2 mmol/kg. Gadobenate dimeglumine is effective for imaging of focal liver lesions at a range of doses, with trends toward improved diagnostic information at higher doses.

MR imaging of the liver: techniques and clinical applications

With a recent advance of fast MR imaging techniques including fast gradient-echo (GRE), fast spin-echo (FSE), single shot FSE (SSFSE) and echo-planar imaging (EPI), and availability of a phased-array torso coil, there can be many possible pulse sequences for liver MR imaging. In clinical practice, optimization of pulse sequences is important for improving diagnostic performance of liver diseases. In this article, we review the current status of liver MR imaging, focusing on the description of standard pulse sequences, and the utility of fast scanning technique and contrast-enhancement studies.