Arterioportal shunts mimicking hepatic tumors with hyperintensity on T2-weighted MR images

We report and assess the imaging findings in a patient with multiple arterioportal shunting mimicking multiple hypervascular tumors that showed multiple areas of hyperintensity with gadolinium-enhanced gradient-recalled-echo images obtained in the hepatic arterial phase and corresponding areas of slight hyperintensity with T2-weighted images.     

T2rho-weighted contrast in MR images of the human brain.

In this work, the feasibility of using T2rho weighting as an MR contrast mechanism is evaluated. Axial images of a human brain were acquired using a single-slice spin-lock T2rho-weighted pulse sequence and compared to analogous T2-weighted images of the same slice. The contrast between white matter and gray matter in T2rho-weighted images was approximately 40% greater than that from T2-weighted data. These preliminary data suggest that the novel contrast mechanism of T2rho can be used to yield high-contrast T2-like images.     

Perilesional hyperintense rim of malignant hepatic tumors on ferumoxide-enhanced T1-weighted gradient-echo MR images: correlation between MR imaging and histopathologic findings

PURPOSE: To correlate the perilesional hyperintense rim of malignant hepatic tumors seen on ferumoxide-enhanced T1-weighted gradient-echo (GE) MR images with histopathologic findings. MATERIALS AND METHODS: In 13 tumors in 12 patients, T1-weighted GE images (TE of 1.4 msec, flip angle of 90 degrees) obtained after IV administration of ferumoxide were evaluated. MR imaging was initiated within one hour of the completion of ferumoxide administration. Surgical resection for tumors was performed within an interval of two weeks of the MR imaging. Resected specimens were histopathologically examined for peritumoral sinusoidal congestion, desmoplastic reaction, compressed hepatic parenchyma, lymphocytic infiltration, and vascular proliferation. RESULTS: In twelve tumors (92%), prominently (N = 2), moderately (N = 5), and mildly to minimally (N = 5), a perilesional hyperintense rim was observed. Among histopathologic findings, the degree of peritumoral sinusoidal congestion correlated (R =.75, P <.04) with the degree of perilesional hyperintense rim. The thickness of the perilesional hyperintense rim showed a moderate positive correlation (R =.65, P <.02) with the thickness of peritumoral area with sinusoidal congestion. CONCLUSION: Perilesional hyperintense rim of malignant hepatic tumors on ferumoxide-enhanced T1-weighted GE images may correlate with sinusoidal congestion surrounding malignant hepatic tumors.     

In vitro investigation of poor cerebrospinal fluid suppression on fluid-attenuated inversion recovery images in the presence of a gadolinium-based contrast agent.

Cerebrospinal fluid (CSF) enhancement on fluid-attenuated inversion recovery (FLAIR) images obtained post-gadolinium (Gd)-based agent injection is described in stroke and multiple sclerosis. Blood brain barrier (BBB) disruption with contrast agent extravasation into CSF shortens T(1) relaxation times, reducing fluid suppression. Reduced fluid suppression on FLAIR images was investigated in vitro in the presence of escalating gadopentetate dimeglumine (Gd-DTPA) concentrations mixed with artificial CSF. Low Gd-DTPA concentrations impair fluid suppression of FLAIR imaging in association with progressively reduced T(1) values. At higher concentrations, the prevalent T(2) shortening effect can explain signal intensity (SI) reduction. Post-Gd FLAIR may be useful in detecting subtle BBB leakage.     

Transthyretin-related familial amyloid polyneuropathy: evaluation of CSF enhancement on serial T1-weighted and fluid-attenuated inversion recovery images following intravenous contrast administration

BACKGROUND AND PURPOSE: CSF enhancement on MR images after intravenous administration of gadolinium chelate, which mimics subarachnoid hemorrhage, has been reported. The purpose of this study was to determine whether CSF enhancement can be seen on serial MR images following administration of contrast material in patients with transthyretin-related familial amyloid polyneuropathy (FAP) and to assess other ancillary MR findings. METHODS: We serially studied T1-weighted and fluid-attenuated inversion recovery (FLAIR) images of the brain before, immediately after, and 3, 6, and 24 hours after contrast administration in 6 patients with genetically confirmed transthyretin-related FAP. By consensus, 2 radiologists assessed the presence, degree, and extent of enhancement of the CSF, leptomeninges, brain parenchyma, and other structures. Statistical analysis was performed to define the difference of the enhancement between the 2 MR imagings. RESULTS: In 3/6 patients with cysteine-for-tyrosine substitutions at position 114 (Tyr114Cys mutations), marked CSF enhancement was observed on the FLAIR images at 3 and 6 hours and on T1-weighted images at 3 hours after contrast administration. Although there was no significant difference between the 2 MR imagings, leptomeningeal enhancement for these 3 patients was evident only on FLAIR images. The labyrinth and vitreous body was also enhanced on postcontrast delayed MR images of these 3 patients. These enhancements were not observed in the other 3 patients with Val30Met mutation. In none of the 6 patients did images demonstrate parenchymal enhancement of the brain. CONCLUSION: In FAP patients with Tyr114Cys mutations, contrast material can leak into the CSF. This finding may depend on the subtype of FAP and be more evident with FLAIR images. The enhancement of the leptomeninges, labyrinth, and vitreous body was also seen in the patients.     

Vacuum disc: frequency of high signal intensity on T2-weighted MR images

Objective. To determine the frequency of lumbar intervertebral disc vacuum clefts demonstrating high signal intensity on T2-weighted magnetic resonance (MR) images. Design and patients. MR images of the lumbosacral spine of 100 patients with radiographic evidence of the lumbar intervertebral disc vacuum phenomenon were retrospectively studied for the signal pattern of the intervertebral disc vacuum clefts. Results and conclusion. Twelve of the reviewed MR studies demonstrated high signal intensity of the vacuum clefts on long TR and TE sequences while the remaining 88 cases demonstrated the vacuum as signal void on both T1- and T2-weighted images. It is concluded that vacuum clefts not infrequently show high T2 signal intensity.     

Contrast-enhanced FLAIR imaging in combination with pre- and postcontrast magnetization transfer T1-weighted imaging: usefulness in the evaluation of brain metastases

PURPOSE: To assess whether the use of postcontrast fluid-attenuated inversion recovery (FLAIR) imaging in combination with pre- and postcontrast magnetization transfer (MT) T1-weighted imaging (T1WI) can increase diagnostic confidence in the evaluation of brain metastases. MATERIALS AND METHODS: Brain MR images from 41 patients with suspected brain metastases were reviewed. Two radiologists viewed pre- and postcontrast MT-T1W images for the presence of metastatic tumors and rated the possible enhanced lesions using a five-point confidence scale (session 1). The postcontrast FLAIR images were then viewed together with pre- and postcontrast MT-T1W images, and the presence of metastasis was rated again (session 2). RESULTS: A total of 240 possible enhanced lesions were detected in session 1. Judging by follow-up MR examinations, 196 were considered to be nonmetastatic findings and 44 were determined to be metastasis. In session 2 the confidence rating for nonmetastasis increased significantly in the subset of nonmetastatic findings (P < 0.001), and the confidence rating for metastasis increased significantly in the subset of metastases (P < 0.05). CONCLUSION: The addition of postcontrast FLAIR imaging to pre- and postcontrast MT-T1WI improves diagnostic confidence in evaluation of brain metastases.     

Relationship between levels of serum creatinine and perirenal hyperintensity on heavily T2-weighted MR images

Objective

To determine the frequency of perirenal hyperintensity on heavily T2-weighted images and to evaluate its relationship with serum creatinine levels.

Subjects and methods

Axial and coronal single-shot fast spin-echo images which have been originally obtained for MR cholangiopancreatography in 150 subjects were examined by two observers individually for the presence of perirenal hyperintensity. The morphologic properties of perirenal hyperintensity (peripheral rim-like, discontinuous, polar) were recorded. Chi square test was used to test whether the frequencies of bilateral perirenal hyperintensity differ significantly in subjects with high serum creatinine levels and those with normal creatinine levels. This test was also used to compare the frequencies of perirenal hyperintensity in patients with and without renal cysts and in patients with and without corticomedullary differentiation. A p value of less than 0.05 was considered to be statistically significant.

Results

The perirenal hyperintensity was identified in 40 of 150 cases (26.6%) on heavily T2-weighted image. Serum creatinine levels were high in 18 of 150 cases (12%). The perirenal hyperintensity was present in 11 of 18 subjects (61%) with high serum creatinine levels and 26 of 132 subjects (19.7%) with normal creatinine levels. The difference of rates in two groups was statistically significant. Odds ratio was 6407 (95% confidence interval 2264-18,129). The frequency of perirenal hyperintensity was also significantly higher in subjects with renal cyst or cysts in whom serum creatinine levels were normal (p < 0.05) (37.5% vs. 11.8%).

Conclusion

Perirenal hyperintensities are more frequent in patients with high serum creatinine levels. They are also more common in patients with simple renal cysts.     

Automated brain extraction from T2-weighted magnetic resonance images

Purpose:

To develop and implement an automated and robust technique to extract brain from T2‐weighted images.

Materials and Methods:

Magnetic resonance imaging (MRI) was performed on 75 adult volunteers to acquire dual fast spin echo (FSE) images with fat‐saturation technique on a 3T Philips scanner. Histogram‐derived thresholds were derived directly from the original images followed by the application of regional labeling, regional connectivity, and mathematical morphological operations to extract brain from axial late‐echo FSE (T2‐weighted) images. The proposed technique was evaluated subjectively by an expert and quantitatively using Bland–Altman plot and Jaccard and Dice similarity measures.

Results:

Excellent agreement between the extracted brain volumes with the proposed technique and manual stripping by an expert was observed based on Bland–Altman plot and also as assessed by high similarity indices (Jaccard: 0.9825 ± 0.0045; Dice: 0.9912 ± 0.0023).

Conclusion:

Brain extraction using the proposed automated methodology is robust and the results are reproducible. J. Magn. Reson. Imaging 2011;33:822–829. © 2011 Wiley‐Liss, Inc.     

Primary biliary cirrhosis: evaluation with T2-weighted MR imaging and MR cholangiopancreatography

Purpose

The aim of this retrospective study is to evaluate the role of T2-weighted MR imaging (MRI) and MR cholangiopancreatography (MRCP) findings in the diagnosis of primary biliary cirrhosis (PBC).

Materials and methods

The following T2-weighted MRI and MRCP findings: segmental hepatic atrophy/hypertrophy, irregular liver surface, parenchymal lace-like fibrosis, rounded low signal intensity lesions centering portal vein branches (periportal halo sign), periportal hyperintensity (cuffing), splenomegaly, ascites, lymphadenopathy, venous collaterals, and the configuration of intrahepatic biliary ducts were reviewed for their diagnostic significance by two observers in 13 female patients (mean age: 49 years) with PBC. Discordant readings of the observers were resolved at consensus.

Results

When parenchymal lace-like fibrosis and periportal halo sign were seen together the sensitivity of T2-weighted MR images was 69%. In six cases periportal hyperintensity (cuffing) and periportal halo sign were seen together. Segmental hypertrophy was present in nine patients and hepatic surface irregularity due to regenerative nodules were present in 10 patients. Lymphadenopathy was seen in 10, splenomegaly was seen in 5, collateral vascular structures were seen in 2 and minimal perihepatic free fluid was seen in 2 patients. MRCP images revealed various mild irregularity in the intrahepatic bile ducts in 8 patients and focal narrowing at the common bile duct level in 1 patient.

Conclusion

MRI and MRCP may support the clinical and laboratory findings of PBC even in the early stages of the disease. MRI can also be a choice of method for the recommended prolonged follow up.     

Principles of contrast enhancement in the evaluation of brain diseases: An overview

Intravenous contrast media are widely used in MR imaging of the brain. Clinical utility is high in both neoplastic and non-neoplastic disease. The agents approved to date are all gadolinium chelates, with extracellular distribution and renal excretion. The agents differ in regard to the maximum dose that can be administered and the theoretical safety margin. When administered at the same dose, the efficacy of the different available agents is comparable. Described in the following review article are the diagnostic use of contrast media and the patterns of enhancement encountered in neoplastic disease, infection, vascular disorders, and diseases of white matter. Only in congenital brain disease, when acute abnormalities are not suspected clinically and neoplastic disease is not a question, is contrast enhancement not indicated. The gadolinium chelates play a major role in the evaluation of patients by MR with known or suspected brain disease. These agents improve both the sensitivity and specificity of the examination. In many cases, lesions cannot be identified before contrast administration. Lesion delineation, assessment of lesion activity, and differential diagnosis are all improved, in general, with the addition of postcontrast scans. The scope of applications continues to expand as the modality and clinical experience matures.     

Effects of ami-25 on liver vessels and tumors on T1-weighted turbo-field-echo images: Implications for tumor characterization

This study was devoted to tumor differentiation in liver MR T1-weighted imaging with superparamagnetic iron oxide (SPIO). Twenty-one patients with 40 liver lesions were studied at 1.5 T. Before and at least 45 minutes after SPIO administration, turbo-field-echo (TFE) T1-weighted, TFE T1 × T2*-weighted (MXT), and fat-suppressed turbo-spin-echo T2-weighted images were acquired. A quantitative analysis was performed blindly. On TFE T1-weighted images, the signal enhancement was ?33% ± 12 for the liver, ?24% ± 2 for adenomas and focal nodular hyperplasia, +60% ± 33 for the hemangiomas; metastases and cyst enhancement were not significant. After SPIO on TFE T1-weighted images, the hemangioma-to-liver signal ratio (149% ± 18) was definitely higher than the mean metastasis-to-liver signal ratio (90% ± 16). This T1-related differentiation ability lacked dramatically on TFE MXT images and, in one case, was reduced on post-SPIO TFE T1-weighted images by a long imaging delay after SPIO administration (2 hours).     

Comparison of inversion recovery fast spin-echo (FSE) with T2-weighted fat-saturated FSE and T1-weighted MR imaging in bone marrow lesion detection

 Objective To prospectively compare inversion recovery (IR) fast spin-echo (FSE) with T1-weighted spin-echo (SE) and T2-weighted chemical-shift fat-saturated (FS) FSE magnetic resonance sequences in the detection of bone marrow abnormality. Design. Twenty-nine sets of T1-weighted SE [400–640/10–20 (TR/TE)], T2-weighted FS-FSE [2400–3800/91–112/8 (TR/TE/ETL)], and IR-FSE [3700–6000/12–14/170/8 (TR/TE/T1/ETL)] images were acquired with a 1.5-T magnet in 27 patients with bone marrow lesions. The visibility, margination, and extent of 41 lesions, image quality, contrast, and artifacts were qualitatively and quantitatively compared. Results. The lesions were more conspicuous on the IR-FSE than on the T1-weighted SE and T2-weighed FS-FSE images. The extent of lesions was similar for all three sequences. Image quality was better and there were fewer motion artifacts on the T1-weighted images. The mean lesion contrast-to-noise ratio was significantly higher on the T1-weighted images (p<0.05). Conclusion. The IR-FSE sequence is highly sensitive for detecting bone marrow pathology, with scan time comparable to the T1-weighted SE and T2-weighted FS-FSE sequences.     

Dynamic contrast enhancement of paragangliomas of the head and neck: evaluation with time-resolved 2D MR projection angiography

Our objective was to evaluate tumor hemodynamics of paragangliomas of the head and neck. A 2D magnetic resonance projection angiography (MRPA) protocol was developed. Six patients with histologically proven paragangliomas were included in the study. The sequence protocol and data post-processing procedure were optimized in view of a high temporal resolution and maximum contrast-to-noise ratio. Image-time series of two freely orientated slabs could be obtained. Correlation analysis was performed to generate selective arterial and venous weighted angiographic images. Glomus tumors showed a rapid and intense homogeneous enhancement following the intravenous administration of contrast material. The smallest tumors investigated measured 10 mm and could be visualized clearly. Time-resolved analysis of the tumor enhancement revealed an early bolus arrival within the vascular bed of the tumor and prolonged incomplete washout indicating blood pooling. The dynamic contrast enhancement of glomus tumors can be evaluated non-invasively with MRPA providing a high temporal resolution and high image quality. The characteristic contrast enhancement of glomus tumors can be helpful in the diagnostic workup of lesions that may mimic glomus tumors.     

Intracranial meningeal disease: comparison of contrast-enhanced MR imaging with fluid-attenuated inversion recovery and fat-suppressed T1-weighted sequences

BACKGROUND AND PURPOSE: Contrast-enhanced fluid-attenuated inversion recovery (FLAIR) imaging has been reported to have higher sensitivity for detecting leptomeningeal disease compared with contrast-enhanced T1-weighted MR imaging. The purpose of this study was to compare contrast-enhanced T1-weighted MR images with fat suppression to contrast-enhanced FLAIR images to determine which sequence was superior for depicting meningeal disease. METHODS: We reviewed MR images of 24 patients (35 studies) with a variety of meningeal diseases. The MR imaging protocol included contrast-enhanced T1-weighted MR images with fat suppression (FS) and contrast-enhanced fluid-attenuated inversion recovery (FLAIR) images that were reviewed by three neuroradiologists and were assigned a rating of positive, equivocal, or negative for abnormal meningeal enhancement. The two sequences were compared side by side to determine which better depicted meningeal disease. RESULTS: Abnormal meningeal enhancement was positive in 35 contrast-enhanced T1-weighted MR images with FS and in 33 contrast-enhanced FLAIR studies. In the first group, which had the T1-weighted sequence acquired first (21 of 33 studies), contrast-enhanced T1-weighted images with FS showed superior contrast enhancement in 11 studies (52%), inferior contrast enhancement in six studies (29%), and equal contrast enhancement in four studies (19%) compared with the contrast-enhanced FLAIR images. In the second group, which had the FLAIR sequence acquired first (12 of 33), contrast-enhanced T1-weighted images with FS showed superior contrast enhancement in seven studies (58%), inferior contrast enhancement in two studies (17%), and equal contrast enhancement in three studies (25%). CONCLUSION: Contrast-enhanced T1-weighted MR imaging with FS is superior to contrast-enhanced FLAIR imaging in most cases for depicting intracranial meningeal diseases.     

Comparative evaluation of magnetization transfer contrast and fluid attenuated inversion recovery sequences in brain tuberculoma

AIM: To compare T1-weighted magnetization transfer (MT) with fluid attenuated inversion recovery (FLAIR) imaging for evaluating conspicuity and number of lesions in individuals with brain tuberculoma. MATERIALS AND METHODS: In all 28 patients with brain tuberculoma underwent MR examination using fast spin-echo (FSE) T2, spin-echo (SE) T1, T1-weighted MT and FLAIR imaging. Post-contrast T1-weighted MT imaging was taken as the gold standard for assessing the number of lesions. Tuberculomas detected both on T1-weighted MT and FLAIR imaging were examined for the wall to be defined, and were divided into two groups on the basis of presence (group 1) or absence (group 2) of perilesional oedema visible on FLAIR imaging. The mean signal intensity of the wall of the lesions and adjacent oedema or brain parenchyma was analyzed qualitatively and quantitatively. RESULTS: The number of lesions detected on T1-weighted MT was higher than on FLAIR imaging (209 versus 163). Conspicuity in both groups was better on T1-weighted MT images qualitatively as well as quantitatively. The difference in the signal intensity of the wall of the lesion and perilesional oedema was statistically significant only on T1-weighted MT images in group 1 (p=0.0003 versus 0.3), whereas in group 2 it was statistically significant both on T1-weighted MT and FLAIR imaging (p=0.009 versus 0.05). CONCLUSION: FLAIR imaging is not helpful in the examination of brain tuberculomas compared with T1-weighted MT imaging, as it neither contributes to the characterization of lesion nor assesses the true disease load.     

T1-Weighted MR imaging of the brain using a fast inversion recovery pulse sequence

The purpose of this paper was to develop and evaluate a fast inversion recovery (FIR) technique for T1-weighted MR imaging of contrast-enhancing brain pathology. The FIR technique was developed, capable of imaging 24 sections in approximately 7 minutes using two echoes per repetition and an alternating echo phase encoding assignment. Resulting images were compared with conventional T1-weighted spin echo (T1SE) images in 18 consecutive patients. Compared with corresponding T1SE images, FIR images were quantitatively comparable or superior for lesion-to-background contrast and contrast-to-noise ratio (CNR). Gray-to-white matter and cerebrospinal fluid (CSF)-to-white matter contrast and CNR were statistically superior in FIR images. Qualitatively, the FIR technique provided comparable lesion detection, improved lesion conspicuity, and superior image contrast compared with T1SE images. Although FIR images had greater amounts of image artifacts, there was not a statistically increased amount of interpretation-interfering image artifact. FIR provides T1-weighted images that are superior to T1SE images for a number of image quality criteria.     

Characteristics and pitfalls of contrast-enhanced, T1-weighted magnetization transfer images of the brain

RATIONALE AND OBJECTIVES: This study was undertaken to clarify the difference in signal pattern on contrast material-enhanced T1-weighted magnetic resonance (MR) magnetization transfer (MT) images between enhancing and nonenhancing lesions in various intracranial diseases and to determine the necessity of nonenhanced MT images for evaluating lesional contrast enhancement. MATERIALS AND METHODS: MR images of 116 patients who underwent nonenhanced T1-weighted imaging, nonenhanced MT imaging, and contrast-enhanced MT imaging were reviewed. The increase in signal intensity of lesions relative to normal brain was compared between nonenhanced T1-weighted images and contrast-enhanced MT images. Signal intensity of lesions was compared with that of the striate nucleus and white matter on contrast-enhanced MT images. True enhancement was determined by comparison with nonenhanced MT images. RESULTS: In all, 143 lesions, including 86 enhancing and 57 nonenhancing lesions, were identified among 63 patients. Almost all (99%) of the enhancing lesions were hyperintense to striate nucleus on contrast-enhanced MT images, and most (>87%) showed moderate to marked signal intensity increase from nonenhanced T1-weighted images to contrast-enhanced MT images. Most (>95%) of the nonenhancing lesions showed mild or no increase in relative signal intensity, and most (75%) were iso- or hypointense to striate nucleus on contrast-enhanced MT images. A few nonenhancing lesions (4%-6%), however, showed increase in signal intensity that was indistinguishable from true enhancement without comparison to non-enhanced MT images. CONCLUSION: Nonenhanced MT images should be obtained to assess pathologic enhancement accurately.