Hepatic nodules in liver transplantation candidates: MR imaging and underlying hepatic disease

OBJECTIVE: To assess by MR imaging the frequency of hepatic nodules in patients waiting on the liver transplant list and to determine whether certain underlying hepatic diseases were more often associated with the development of such hepatic nodules. MATERIAL AND METHODS: We reviewed the MR and clinical records in all patients seen by the liver transplant service at our center since its inception in January 1998 until September 2002. A total of 371 patients (207 men and 164 women, age range 18-68 years, mean 45 years) were included in the study. The presence of hepatic nodules, size, number and underlying hepatic diseases were determined in all patients. Magnetic resonance imaging was performed on a 1.5-T MR imager using T1-weighted, T2-weighted and multi-phase gadolinium-enhanced sequences. Odds ratio (OR) and 95% confidence intervals (CIs) were computed to evaluate the association between the underlying hepatic disease and the development of hepatic nodule. RESULTS: Among 371 liver transplantation candidates, the most common underlying hepatic disease was hepatitis C virus (HCV) infection, either alone (n=93; 25%) or associated with other hepatic diseases (n=40; 10.8%). Of all patients, 33 (8.9%) had regenerative nodules (RNs), 40 (10.7%) dysplastic nodules (DNs) and 57 (15.3%) hepatocellular carcinomas (HCCs). Hepatocellular carcinoma was observed in 35.3% of patients with HCV infection and alcohol abuse combined, 24.5% with cryptogenic cirrhosis, 25% with hemochromatosis and 19% with alcohol abuse. Patients who had either DNs or HCC were 2.5 times more likely to have either alcohol abuse or HCV, alone or combined, as the substrate of their liver disease (OR 2.54, 95% CI 1.56-4.13). Our data suggest a supra-additive interaction between HCV infection and ethanol in their association with MR imaging detected lesions. CONCLUSION: Patients with cryptogenic cirrhosis, alcohol abuse, HCV infection (alone or combined) and hemochromatosis had the greatest likelihood of having HCC, with the combination of HCV infection and alcohol abuse having the highest of all.     

Cavernous hemangiomas in patients with chronic liver disease: MR imaging findings

The purpose of our study was to assess the difference in magnetic resonance imaging (MRI) features of cavernous hemangiomas in patients with chronic liver disease compared them with hemangiomas in normal livers. We retrospectively searched our records of MRI of the liver between October 1998 and June 2002, and identified 76 hemangiomas in 49 patients (18 men and 31 women; age range 29-81 years [mean, 57 years]). Hemangiomas were classified into 3 groups: patients with cirrhosis [group 1, 8 lesions in 8 patients], patients with chronic hepatitis [group 2, 6 lesions in 5 patients], and patients without underlying liver disease [group 3, 62 lesions in 36 patients]. Four radiologists, blinded to clinical information, retrospectively reviewed in consensus the MRI findings of hemangiomas for number, size, signal intensities on T1- and T2-weighted images, and enhancement patterns on early- and late-phase postcontrast images. The mean lesion numbers and sizes were 1.0 and 16.2 +/- 9.6 mm, 1.2 and 15.3 +/- 7.1 mm, and 1.7 and 26.1 +/- 24.7 mm in groups 1-3, respectively. There was a correlation (p < 0.05, coefficient: 0.35) between lesion number and severity of liver disease. Although there was no significant difference in lesion size among the 3 groups, all of 11 lesions larger than 4 cm in diameter belonged to group 3. Almost all lesions appeared moderately hypointense on T1-weighted images and moderately hyperintense on T2-weighted images. Twenty-seven lesions showed immediate homogeneous enhancement (pattern 1), and 49 showed peripheral nodular enhancement with centripetal enhancement progression (pattern 2). There was no difference in frequency of enhancement patterns among the 3 groups. Hemangiomas were more often solitary in livers with chronic liver disease, large lesions were exclusively seen in livers without chronic liver disease, and there was a trend for small lesions in patients with chronic liver disease.     

MR imaging with phase encoding of intermolecular multiple quantum coherences

Novel 2D and 3D pulse sequences producing images through the phase encoding of intermolecular multiple quantum coherences (i-MQCs) are presented. The signal acquired with these sequences is free from intermolecular zero quantum coherences (i-ZQCs) which are not phase encoded and additional phase cycling eliminates artifacts. Phase encoding during the n-quantum evolution period provides n times the resolution expected from equivalent phase encoding of the reconverted single quantum coherences. These sequences have potential applications for producing i-MQC images of biological tissues as well as nonbiological materials with substantial amounts of water.     

MR imaging of non-cancerous hepatic lesions in Long-Evans Cinnamon rats

We measured MR images of the liver of Long-Evans Cinnamon (LEC) rats with pathologic correlation and assessed the effectiveness of MR imaging (MRI) for diagnosis of noncancerous hepatic lesions. T₁- and T₂-weighted images of their livers were obtained, and the dynamic and delayed studies after intravenous gadolinium injection were also performed. Cholangiofibrosis showed low signal intensity on T₁-weighted images and high signal intensity on T₂-weighted images. The T₂ relaxation time of cholangiofibrosis was significantly prolonged (p < .01), and the signal intensity ratio of this lesion to muscle on T₁-weighted images was significantly lower than that of normal liver parenchyma to muscle (p < .01). The lesion was enhanced immediately after gadolinium injection and the enhancement was prolonged. Among three cases of peliosis hepatis identified, one showed heterogeneous intensities on both T₁- and T₂-weighted images and the other two showed similar intensity pattern to cholangiofibrosis. The characteristic MR appearance of cholangiofibrosis may be useful to distinguish it from hepatocellular carcinoma (HCC).     

Functional MR imaging assessment of a non-responsive brain injured patient.

Functional magnetic resonance imaging (fMRI) was requested to assist in the evaluation of a comatose 38-year-old woman who had sustained multiple cerebral contusions from a motor vehicle accident. Previous electrophysiologic studies suggested absence of thalamocortical processing in response to median nerve stimulation. Whole-brain fMRI was performed utilizing visual, somatosensory, and auditory stimulation paradigms. Results demonstrated intact task-correlated sensory and cognitive blood oxygen level dependent (BOLD) hemodynamic response to stimuli. Electrodiagnostic studies were repeated and evoked potentials indicated supratentorial recovery in the cerebrum. At 3-months post trauma the patient had recovered many cognitive & sensorimotor functions, accurately reflecting the prognostic fMRI evaluation. These results indicate that fMRI examinations may provide a useful evaluation for brain function in non-responsive brain trauma patients.     

Introduction of fast MR imaging in the assessment of hepatic steatosis

We determined the utility of fast gradient echo techniques (modified Dixon method) in the assessment of hepatic fat content. Fast spoiled gradient echo was performed on bovine liver/corn oil homogenates with known fat fractions (FF_E) to assess the accuracy of fat quantitation (FF_MRI). The pulse sequence was manipulated via alterations in TE (echo time), TR (repetition time), and α (flip angle). In vivo studies were then performed using breath-holding maneuvers on normal adult volunteers and subjects at risk to develop hepatic steatosis, with cystic fibrosis or morbid obesity. At out-of-phase, TE, TR, and α were 2.1 ms, 7.3 ms, and 30–50° and in-phase TE, TR, and α were 4.2 ms, 9.3 ms, and 30–50°; FF_MRI correlated well with FF_E. An elevated fat fraction was observed in a high percentage of subjects with cystic fibrosis and morbid obesity. Fast gradient echo techniques were used successfully in the assessment of hepatic steatosis. The reduced acquisition times permitted in vivo analysis on adults and children using breath hold maneuvers.     

Hepatic sarcoidosis: MR appearances in patients with chronic liver disease

Purpose

To describe the MR appearances of hepatic sarcoidosis in patients with chronic liver disease and correlate the results with clinical stage of disease as measured with the Mayo end-stage liver disease (MELD) score.

Materials and methods

Twenty patients with chronic liver disease and histopathological diagnosis of hepatic sarcoidosis who underwent MR imaging were included in this study. Two abdominal radiologists retrospectively reviewed all images for the presence of cirrhosis, imaging pattern of the liver, intrahepatic biliary dilatation, presence of areas of parenchymal atrophy, presence of splenic nodules and lymphadenopathy. Imaging findings were correlated with the MELD score.

Results

Of the patients, 14/20 had imaging findings of cirrhosis, 9/20 had a large macronodular pattern of liver cirrhosis and 5/20 had a diffuse pattern of liver cirrhosis. Peripheral wedge-shaped areas of parenchymal atrophy were observed in 10 patients. The combination of a central macronodular pattern and peripheral atrophy was observed in 9/20 patients. The pattern of cirrhosis had statistically significant correlation with the presence of wedge-shaped areas of parenchymal atrophy (p < 0.005). No statistically significant difference was revealed between the clinical score of patients who had imaging findings consistent with cirrhosis and those who did not.

Conclusion

MR imaging appearances of chronic sarcoid liver disease are diverse and do not appear to correlate with severity of clinical disease. Large central regenerative nodules and wedge-shaped areas of peripheral parenchymal atrophy are frequent findings and may help to suggest the diagnosis.     

Recurrent hepatocellular carcinoma versus radiation-induced hepatic injury: differential diagnosis with MR imaging

The objective of this study was to assess the value of MR imaging in the differentiation between a recurrent hepatocellular carcinoma (HCC) and a radiation-induced hepatic injury. Nine male patients with suspected recurrence after radiotherapy for HCC underwent T(2)-, T(1)-weighted imaging and Gd-DTPA enhanced dynamic studies. T(2) relaxation times, signal intensity ratios in T(1)-weighted images (WI) and the relative enhancement of the dynamic study were calculated. Recurrent tumors and the irradiated area showed similar image characteristics: hypointense in T(1)-WI and hyperintense in T(2)-WI. T(2) values and signal intensity ratios in the T(1)-WI were not significantly different. In the gadolinium-enhanced dynamic study, a recurrent HCC showed early enhancement, followed by a rapid washout. However, the irradiated liver parenchyma showed hyperintensity from an early phase, and contrast enhancement tended to be more prominent and prolonged at the end of the dynamic studies. The characteristic findings of the dynamic MR study enable us to distinguish between a recurrent HCC and a radiation-induced hepatic injury.     

MR imaging of liver abscesses; application of Gd-DTPA

The potential utility of Gd-DTPA contrast enhancement of MR images in the evaluation of liver abscesses was assessed in rodents. Twelve rats with surgically implanted sterile liver abscesses were imaged at various stages of focal hepatic inflammation, 48 hours, 4 days, 7 days, 14 days and 21 days after lesion induction. Spin echo images, acquired before and repeatedly after intravenous injection of 0.2 mmol/kg Gd-DTPA, demonstrated improvement of the lesion-to-background contrast ranging from 2% to 40% depending on the stage of the disease. The enhancement pattern also varied with abscess evolution. Two, four and seven-day-old abscesses typically showed a ring enhancement, whereas two- and three-week-old abscesses presented largely homogeneously enhancing lesions. In the earlier lesions, contrast enhanced rim surrounding the low intensity center corresponded histologically to the formation of a capsule consisting of fibrous tissue and inflammatory cells. The center was necrotic. Data show that abscesses can be detected on images acquired with long repetition and echo times without injection of Gd-DTPA. The administration of Gd-DTPA, however, improved the lesion-to-background contrast and helped to define the abscess capsule evolution.     

MnDPDP-enhanced magnetization transfer MR imaging: implications for effective liver imaging

The benefit of combining magnetization transfer (MT) MR imaging technique with liver-specific contrast agent manganese dipyridoxyldiphosphate (MnDPDP) was assessed in our experimental investigation. The study was accomplished by imaging a phantom containing serial concentrations of MnDPDP in cross-linked bovine serum albumin (BSA) with various protein concentrations. A 0.1T clinical MR imager with different parameters for MT and conventional MR sequences were used. The combination of an offset frequency of 8 kHz and an amplitude of 25 microT produced nearly maximal MT effect for all protein samples either without MnDPDP or with different MnDPDP concentrations. With long TRs (TR > 200 ms) MT dramatically improved CNR in conjunction with MnDPDP. With short TRs, the gain in CNR with MT was negligible. However, long TRs with increased number of images are beneficial in liver imaging. We conclude that MT like preparation pulse is useful when paramagnetic contrast agents such as MnDPDP are employed.     

Epithelioid hemangioendothelioma of the liver. MR imaging findings

We report the MR appearance of epithelioid hemangioendothelioma (EHE) in a 51 year old man, who presented with a 14-month history of fatigue and anemia to his physician. The tumor showed massive replacement of the liver and had an unusual appearance of multiple high fluid content focal lesions with diminished vascularity.     

Combined diffusion-weighted and spectroscopic MR imaging in Creutzfeldt-Jakob disease

A 49-year-old woman presented with progressive dementia. Diffusion-weighted MR images showed abnormalities in the cerebral cortex as well as the putamen and caudate head bilaterally. MR spectroscopic imaging revealed marked asymmetric decrease of normal metabolites in the right basal ganglia, with concordant hypoperfusion on single photon emission computed tomography. Diffusion-weighted MR imaging is more sensitive to cortical involvement in sporadic Creutzfeldt-Jakob Disease, and MR spectroscopy may yield evidence of asymmetric involvement. Combined functional and metabolic MR imaging may be useful in studying CJD.     

Changes in the liver parenchyma after proton beam radiotherapy: evaluation with MR imaging

The objective of this study was to describe magnetic resonance (MR) findings with a 1.5T imager for hepatic parenchymal changes after proton beam radiotherapy. Thirty-two patients who received proton radiotherapy with doses of 50-87 Gy underwent MR imaging 1-75 months (mean 22 months) after the start of irradiation. Axial T(2), T(1)-weighted imaging, and a dynamic study after a gadolinium injection were performed. The irradiated areas showed hypointense in T(1)-weighted images, hyperintense in T(2)-weighted images, and intense and prolonged enhancement on the dynamic study (maximum relative enhancement 441.8%+/-263.3 vs. surrounding liver 145.6%+/-67.7, p<0.0001). T(2) values of the irradiated areas were 50.6 to 65.8 msec greater than in the surrounding liver (p<0.005). The values increased with time, being significantly greater 13 months or longer after the beginning of the therapy than after a period of less than 3 months (p<0.05). Pathologic examinations (n = 3) indicated that the irradiated areas were composed of collapsed lobules with hepatic small vein occlusions, and rich extracellular matrices which retained extracellular fluid. MR imaging can demonstrate hepatic parenchymal changes after proton beam radiotherapy, and show the changes are irreversible.     

Evaluation of a contraceptive device with MR imaging.

The purpose of this investigation is to evaluate the positioning and to confirm the volume concept of the Lea's Shield diaphragm utilizing MR imaging. We evaluated the device in two women, one nulliparous and one multiparous. We were able to comprehensively evaluate the device in both patients and answer all questions regarding anatomical positioning and aspects pertaining to the morphology of the device relevant to its function. MRI may be effectively utilized to evaluate contraceptive devices and their relationship to adjacent anatomical structures. This may enhance the gynecologist's clinical assessment of its correct positioning and efficacy.     

Primary malignant mesothelioma of the liver: MR imaging findings

We report the MR imaging findings of a primary malignant mesothelioma of the liver arising from Glisson's capsule. A 54-year-old woman, presenting with acute abdominal pain and a large liver mass previously shown on CT, underwent MR imaging to characterize the lesion. The tumor was a greater than 12 cm tumor located in the right lobe of the liver, which was sharply marginated, with heterogeneous internal signal, septations and central necrosis. The tumor was considered a hepatocellular carcinoma. The diagnosis of malignant mesothelioma was established by immunohistochemical staining and electron microscopy of the resected tumor.     

MR and CT imaging of ethanol-treated liver tumors in an animal model

To characterize the radiographic appearance of liver lesions over time following ethanol injection, seven New Zealand white rabbits underwent surgical implantation of small fragments of VX-2 carcinoma within the liver. Upon reaching 1 cm in diameter, a tumor nodule was directly injected with absolute ethanol. Another nodule in the same animal was injected with saline as a control. Imaging was performed 6-24 days after the injections by high resolution CT and MRI, and correlation obtained with the pathologic specimens. Long TR spin-echo MR sequences were found to characterize the ethanol-treated regions of liver most accurately. Liver tissue infarcted by alcohol could be differentiated from tumor and necrosis by virtue of its short T2 relaxation value. There were no distinguishing features by other imaging techniques between the ethanol-treated and control tumor nodules. Peripheral contrast enhancement was demonstrated in both, corresponding to fibrous tissue around the ethanol-injected regions, and to viable tumor in the case of controls.     

Giant hemangioma of the liver: MR imaging characteristics in 24 patients

We retrospectively reviewed the magnetic resonance imaging (MRI) of giant hemangiomas in 24 patients. MRI studies comprised T1-weighted, T2-weighted and serial gadolinium-enhanced spoiled gradient echo (SGE) images. Morphologic features, signal characteristics and enhancement patterns were assessed. Histopathologic evaluation was obtained in nine patients. On T2-weighted images all lesions (size 5.7-24 cm) were hyperintense relative to the spleen and two dominant patterns of heterogeneity were demonstrated: a central heterogeneous area of either bright, dark, or mixed signal intensity, and a network of multiple fibrous septa of low signal intensity. Histopathologic evaluation of two lesions with a central bright area demonstrated the presence of hypocellular myxoid tissue. Central enhancement (9 lesions) and an irregular flame-shaped peripheral pattern of enhancement (12 lesions) were present in lesions with a mean diameter greater than 10 cm. Although giant hemangiomas show greater variability in their MR imaging appearance, an accurate diagnosis can be made through still characteristic features of high signal intensity on T2-weighted images and discontinuous peripheral enhancement.     

Magnetization prepared rapid gradient-echo (MP-RAGE) MR imaging of the liver: comparison with spin-echo imaging.

We have implemented an MR technique that employs a rapid gradient echo sequence, preceded by magnetization preparation pulses to provide T1- and T2-weighted tissue contrast. With this technique, which can be identified as a member of a new family of pulse sequences, generically named Magnetization Prepared RApid Gradient Echo (MP-RAGE), very short repetition times are used, allowing acquisition times of less than one second and images virtually free of motion-induced artifacts during quiet respiration. Fifteen patients with known liver lesions (metastases, hemangiomas, and cysts) were examined using T1- and T2-weighted 2-dimensional MP-RAGE sequences, and the images were compared with conventional T1- and multi-echo T2-weighted spin-echo (SE) sequences. Signal difference-to-noise ratios (SD/Ns) of the lesions were calculated for all pulse sequences using corresponding axial images and were normalized for voxel volume. The mean normalized SD/Ns of the MP-RAGE sequences were generally comparable to those for the SE sequences. In addition, there were no noticeable respiratory artifacts on the MP-RAGE images whereas these were clearly present on the T2-weighted SE images and to a lesser degree on the T1-weighted SE images. It is concluded that the MP-RAGE technique could become an important method for evaluating the liver for focal disease.     

Feasibility of fast MR imaging of the liver at 1.5 T

A phantom with T1 and T2 relaxation times encompassing normal liver and liver lesions was constructed to evaluate fast magnetic resonance pulse sequences using TR from 21-100 milliseconds, TE 12-60 milliseconds and flip angles from 5 degrees-90 degrees. Ten of these fast MR sequences were then selected and compared with conventional spin-echo sequences in normal volunteers (n = 3) and in patients with liver lesions (n = 6). Subjectively, the fast MR sequences eliminated motion artefacts. Objectively, 8 of 10 fast sequences had signal-to-noise ratios comparable to spin-echo imaging whereas only 2 of 10 had contrast-to-noise ratios that were similar to spin-echo imaging. This preliminary study, performed at 1.5 Tesla, does not show any clear-cut advantage of fast imaging over spin-echo imaging in the detection of liver lesions. The use of a liver tissue equivalent phantom provides a rapid, practical approach in evaluation of fast scans.     

Superparamagnetic iron oxide-enhanced MR imaging for early and late radiation-induced hepatic injuries

Superparamagnetic iron oxide (SPIO)-enhanced MRI was performed in twenty-one patients undergoing proton-beam radiotherapy for hepatocellular carcinomas. Patients were divided into two groups: early and late phase hepatic injuries. Each group was investigated 3 to 9 weeks and 4 to 65 months after the start of irradiation, respectively. T(1)-weighted, T(2)-weighted, and T(2)*-weighted images were obtained before and after SPIO administration. In all postcontrast sequences in the early phase, irradiated livers demonstrated relatively higher intensity than nonirradiated livers and the radiation-to-liver contrast-to-noise ratio (C/N) was improved. Postcontrast T(2)*-weighted images showed the highest C/N. In the late phase, the irradiated areas showed high intensity on T(2)-weighted images and low intensity on T(1)-weighted images without SPIO, while high intensity on T(1)-weighted images with SPIO. The C/N increased with SPIO in all sequences and postcontrast T(2)-weighted images showed the highest C/N in the late phase. SPIO-enhanced MRI is useful to evaluate this entity both in the early and late phase of clinical studies.