Measurement of abdominal fat with T1-weighted MR images.

The cross-sectional area of visceral and subcutaneous fat in the abdomen was measured with T1-weighted spin-echo images acquired with a 1.5-T magnetic resonance (MR) imager. Four axial images centered on L-4 were acquired in each patient. Outline regions of interest (ROIs) were drawn manually for subcutaneous and visceral fat. The subcutaneous fat cross-sectional area was calculated from the ROIs drawn around the outer and inner margins of subcutaneous fat. Several adaptive processing methods were evaluated for measuring fat in the complex structure of the viscera. These methods were compared with an existing MR imaging measurement method for abdominal fat in 18 patients. The adaptive method that uses the valley between the fat and nonfat distributions in the average histogram curve was judged best for research evaluations because it reduces the effects of volume averaging while using a more natural division between fat and nonfat data. Another adaptive method that yielded comparable measurements was thought to be more suitable for clinical applications. Cross-sectional area measurements of abdominal fat were compared in 18 nonobese and 17 obese women to illustrate the utility of these measurements.     

Breast lesions: evaluation with dynamic contrast-enhanced T1-weighted MR imaging and with T2*-weighted first-pass perfusion MR imaging

PURPOSE: To evaluate the diagnostic value of an imaging protocol that combines dynamic contrast-enhanced T1-weighted magnetic resonance (MR) imaging and T2*-weighted first-pass perfusion imaging in patients with breast tumors and to determine if T2*-weighted imaging can provide additional diagnostic information to that obtained with T1-weighted imaging. MATERIALS AND METHODS: One hundred thirty patients with breast tumors underwent MR imaging with dynamic contrast-enhanced T1-weighted imaging of the entire breast, which was followed immediately with single-section, T2*-weighted imaging of the tumor. RESULTS: With T2*-weighted perfusion imaging, 57 of 72 carcinomas but only four of 58 benign lesions had a signal intensity loss of 20% or more during the first pass, for a sensitivity of 79% and a specificity of 93%. With dynamic contrast-enhanced T1-weighted imaging, 64 carcinomas and 19 benign lesions showed a signal intensity increase of 90% or more in the first image obtained after the administration of contrast material, for a sensitivity of 89% and a specificity of 67%. CONCLUSION: T2*-weighted first-pass perfusion imaging can help differentiate between benign and malignant breast lesions with a high level of specificity. The combination of T1-weighted and T2*-weighted imaging is feasible in a single patient examination and may improve breast MR imaging.     

Breast lesions with high signal intensity on T1-weighted MR images

Magnetic resonance imaging of the breast supplies much information concerning the signal characteristics of a lesion. Among these, high signal intensity on non-fat saturated T1-weighted imaging (WI) is a special finding. Such a finding may result from different causes, such as a paramagnetic substance or fatty, bloody or proteinaceous content. In this article, we present hyperintense breast lesions on T1-WI.     

Hyperintense basal ganglia on T1-weighted MR images in patients receiving parenteral nutrition

Patterns of intracranial signal intensity on magnetic resonance (MR) images were studied in nine patients undergoing long-term total parenteral nutrition therapy. The duration of therapy ranged from 5 months to 11 years (mean, 5.3 years). Symmetric increased signal intensity on T1-weighted MR images (hyperintense relative to white matter) was observed in the basal ganglia of all patients, without corresponding abnormality on T2-weighted images. Analysis of signal-intensity characteristics and distribution pattern suggests that the basis for these changes may be deposition of intravenously administered paramagnetic trace elements, especially manganese, and/or an astrogliotic reaction to such deposition.     

Hyperintense basal ganglia lesions on T1-weighted MR images in asymptomatic patients with hepatic dysfunction

Cranial MRI findings in four patients who had hepatic dysfunction, including one with sole hepatic form of Wilson's disease, were reported. The MR examinations revealed bilateral, symmetric hyperintensity in the globus pallidus, subthalamic nuclei and mesencephalon on T1-weighted images with no corresponding abnormality on T2-weighted sequences. The basal ganglia were normal on CT examinations in all patients. None of the patients had the clinical findings of hepatic encephalopathy. The MR findings in our patients did not correlate with the degree or duration of hepatic dysfunction. Correspondence to: I. Saatci     

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.     

High-intensity basal ganglia lesions on T1-weighted MR images in neurofibromatosis

Basal ganglia lesions, characterized on MR by increased signal intensity on T1-weighted images, were observed in seven patients with documented neurofibromatosis. These lesions most often involved the globus pallidus and internal capsules in a bilateral and symmetric fashion, and extended across the anterior commissure resulting in a "dumbbell" configuration. Smaller and less prominent foci of increased signal also were present on corresponding T2-weighted images. These lesions did not exhibit mass effect, edema, or enhancement with gadolinium-DTPA. They were not visible on CT (performed in two patients) and demonstrated no progression during a 2-year interval in three patients. Their signal characteristics and morphology suggest that they represent heterotopias containing Schwann cells and/or melanin deposits. Migrational abnormalities of these neural crest derivatives are known to occur in neurofibromatosis, and the presence of such heterotopias has been documented pathologically in patients with this disorder. While recent reports discuss foci of increased signal intensity on T2-weighted MR images in patients with neurofibromatosis, signal abnormalities on T1-weighted images have not yet been described. When lesions characterized by similar signal as well as morphologic characteristics are encountered on MR, the diagnosis of neurofibromatosis should be considered.     

High-intensity basal ganglia lesions on T1-weighted MR images in neurofibromatosis

Basal ganglia lesions, characterized on MR by increased signal intensity on T1-weighted images, were observed in seven patients with documented neurofibromatosis. These lesions most often involved the globus pallidus and internal capsules in a bilateral and symmetric fashion, and extended across the anterior commissure resulting in a "dumbbell" configuration. Smaller and less prominent foci of increased signal also were present on corresponding T2-weighted images. These lesions did not exhibit mass effect, edema, or enhancement with gadolinium-DTPA. They were not visible on CT (performed in two patients) and demonstrated no progression during a 2-year interval in three patients. Their signal characteristics and morphology suggest that they represent heterotopias containing Schwann cells and/or melanin deposits. Migrational abnormalities of these neural crest derivatives are known to occur in neurofibromatosis, and the presence of such heterotopias has been documented pathologically in patients with this disorder. While recent reports discuss foci of increased signal intensity on T2-weighted MR images in patients with neurofibromatosis, signal abnormalities on T1-weighted images have not yet been described. When lesions characterized by similar signal as well as morphologic characteristics are encountered on MR, the diagnosis of neurofibromatosis should be considered.     

MR imaging in the evaluation of benign uterine masses: value of gadopentetate dimeglumine-enhanced T1-weighted images.

Forty-six patients with surgically proved disease (115 leiomyomas, 19 cases of adenomyosis, and 14 endometrial polyps) were studied to determine if gadopentetate dimeglumine-enhanced T1-weighted MR images improve the detection and characterization of benign tumors of the uterus. Lesion detection and characterization were assessed separately for each sequence (unenhanced T1-weighted, proton-density-weighted, and T2-weighted and contrast-enhanced T1-weighted images) and for combinations of sequences (unenhanced T1- and T2-weighted images, unenhanced and contrast-enhanced T1-weighted images, and unenhanced T1- and T2-weighted and contrast-enhanced T1-weighted images). In the evaluation of leiomyomas, analysis of all three sequences provided the best detection (92%) and characterization (92%), but the improvement, except when compared with unenhanced T1-weighted images alone, was not statistically significant. The use of contrast medium did not contribute to either tumor detection or characterization. In the evaluation of adenomyosis, T2-weighted images provided significantly better lesion detection and characterization than did either unenhanced or contrast-enhanced T1-weighted images. In the evaluation of endometrial polyps, however, contrast-enhanced T1-weighted images provided significantly better lesion detection and characterization than did unenhanced images. With contrast-enhanced images, the detection rate was 79%, compared with 36% for T2-weighted images and 7% for T1-weighted images. Lesion characterization was the best (73%) when all imaging sequences were analyzed. Our study shows that with conventional spin-echo sequences, the use of contrast-enhanced T1-weighted images does not improve the detection or characterization of uterine leiomyomas or adenomyosis but significantly improves the detection of endometrial polyps.     

MR arthrography of the hip: evaluation of isotropic 3D intermediate-weighted FSE and hybrid GRE T1-weighted sequences

Purpose

To compare the diagnostic performance of three-dimensional (3D) intermediate-weighted FSE (IW-3D) and 3D hybrid T1-weighted sequences (Hy-3D) and 2D fast-spin-echo sequences (FSE) in diagnosing chondral and labral lesions at 1.5 Tesla hip MR arthrography (MRA).

Materials and methods

Institutional review board approval was obtained and informed consent was waived. Ninety-two consecutive patients were evaluated. Chondral and labral lesions were retrospectively and independently evaluated by two radiologists. Intra-operative findings were used as the reference standard (arthroscopy = 73, open surgery = 19). Sensitivity (Se), specificity (Sp), and accuracy (Acc) values that obtained were compared using McNemar test. A value of p < 0.05 was considered statistically significant. Inter-observer agreement was calculated using kappa statistics.

Results

Surgeons revealed 81 labrum and 44 chondral lesions, respectively. The highest Se, Sp, and Acc for Reader 1 were 96.3, 90.9, and 95.6%, respectively, in evaluating labral lesions (by reading 2D data set) and 90.9, 100, and 95.7% in evaluating chondral lesions (by reading IW-3D images). The highest Se, Sp, and Acc for Reader 2 were 93.8, 81.8, and 92.4% in evaluating labral lesions (using 2D images) and 88.6, 97.9, and 93.5%, respectively, in evaluating chondral lesions (using Hy-3D). The difference of diagnostic accuracy achieved was not significant (p > 0.05). A near-perfect inter-observer agreement was achieved by reading 2D data set (k = 0.88) and Hy-3D (k = 0.83) and IW-3D (k = 0.85).

Conclusions

At 1.5 Tesla hip MRA, the accuracy of IW-3D and Hy-3D images was not significantly higher than the 2D sequences in evaluating acetabular labrum and chondral lesions.

     

A histopathological evaluation of a concave-shaped low-intensity band on T1-weighted MR images in a subchondral insufficiency fracture of the femoral head

A 73-year-old female suffered from right hip pain without any history of antecedent trauma. The initial radiograph showed a slight narrowing of the joint space in the right hip. The patient was treated by non-weight bearing for 5 weeks. Radiographs obtained 3 months after the onset of pain showed the progression of both the joint-space narrowing and subchondral collapse at the superior portion. T1-weighted MR (magnetic resonance) images obtained 3 months after the onset revealed an irregular-shaped low-intensity area just beneath the articular cartilage as well as a low-intensity band, which was concave to the articular surface. A total hip replacement was performed. A histopathological examination revealed fracture callus and granulation tissue in the subchondral area. This subchondral fractured area was surrounded by vascular rich granulation tissue and fibrous tissue, which corresponded to the concave-shaped low-intensity band observed on the T1-weighted image.     

Hepatocellular tumors with high signal on T1-weighted MR images: chemical shift MR imaging and histologic correlation.

We reviewed conventional and chemical shift MR images and histologic findings of seven proven primary hepatic masses that had higher signal than liver on T1-weighted images to determine if this necessarily indicates fat and if the presence of fat indicates malignancy. These seven masses included five hepatocellular carcinomas (HCCs), one focal nodular hyperplasia (FNH), and one fatty dysplastic nodule. An eighth solitary high signal mass without histologic proof had evidence of abundant fat on each of two chemical shift MR images 25 months apart. Only one of the five HCCs had chemical shift or histologic evidence of fat, while the FNH and dysplastic nodule each had both chemical shift and histologic confirmation of fat. The dysplastic nodule became more dysplastic and grew significantly within 14 months, but remained benign. The unproven fatty lesion decreased in size over 25 months and is therefore presumably benign. Although no statistical inferences can be drawn from this small correlative study, we have shown that HCC may have higher signal intensity than liver on T1-weighted images, whether or not it contains fat. Chemical shift techniques can confirm the presence of intratumoral fat and thus indicate a mass of hepatocellular origin, but the mass may be benign or malignant.     

Adrenal masses: characterization with T1-weighted MR imaging

The ability of a T1-weighted spin-echo magnetic resonance (MR) sequence to allow differentiation of benign from malignant adrenal masses at 0.5 T was investigated in 28 patients with 35 adrenal masses. All nine lesions with an adrenal mass-liver signal intensity ratio of 0.71 or less were metastases, and all 15 with a ratio of 0.78 or more were adenomas. Eleven masses (31%)--including six adenomas, three metastases, a pheochromocytoma, and a neuroblastoma--had ratios between these values. Nine of ten masses with adrenal mass-fat intensity ratios of 0.35 or less were metastases, and all 12 with ratios of 0.42 or more were benign. Eleven masses (31%), four malignant and one benign, had ratios between these values. The ratios for two masses could not be calculated due to lack of fat. The specificity of T1-weighted MR imaging in differentiating benign from malignant adrenal masses appears similar to that reported for T2-weighted imaging. However, significant overlap occurred, as has also been reported for T2-weighted imaging. While both imaging sequences may help distinguish benign from malignant adrenal masses in some cases, biopsy is still necessary when an accurate histologic diagnosis is essential.     

Early biliary complications of laparoscopic cholecystectomy: evaluation on T2-weighted MR cholangiography in conjunction with mangafodipir trisodium-enhanced 3D T1-weighted MR cholangiography

OBJECTIVE: Our aim was to assess preliminary experience with combined conventional T2-weighted and mangafodipir trisodium (MnDPDP)-enhanced T1-weighted MR cholangiography in evaluating early biliary complications of laparoscopic cholecystectomy. SUBJECTS AND METHODS: Conventional heavily T2-weighted MR cholangiography with MnDPDP-enhanced T1-weighted MR cholangiography and ERCP were performed in seven patients with high clinical suspicion of biliary complications after laparoscopic cholecystectomy. The final diagnoses of complications were classified according to the presence and degree of bile duct injury, bile leakage, and retained stones. RESULTS: The diagnoses on MR cholangiography were as follows: complete transection and occlusion of the common bile duct with bile leakage (n = 3), partial strictures of the common bile duct with bile leakage (n = 1), cystic duct leakage (n = 1), partial ligation of an aberrant right hepatic duct (n = 1), and hemorrhage without biliary complication (n = 1). The final diagnoses at surgery (n = 2) and ERCP (n = 5) were as follows: complete transection and occlusion of the common bile duct with bile leakage (n = 2), partial strictures of the common bile duct with bile leakage (n = 2), cystic duct leakage (n = 1), partial ligation of an aberrant right hepatic duct (n = 1), and hemorrhage without biliary complication (n = 1). MR cholangiography accurately yielded the same findings as the final diagnoses, except in one case with partial stricture of the bile duct with bile leakage (overdiagnosed as complete occlusion on MR cholangiography). CONCLUSION: Combined conventional T2-weighted and MnDPDP-enhanced T1-weighted MR cholangiography may eliminate the use of other studies for the imaging of biliary complications after cholecystectomy if this preliminary data can be verified in a larger study.     

High intensity areas on noncontrast T1-weighted MR images in cerebral infarction

Among 46 noncontrast magnetic resonance studies on patients with cerebral infarction, 11 showed areas of high signal intensity of the involved brain on T1-weighted images. These areas were more frequent in cerebral or cerebellar cortical lesions. Lacunar infarcts in lenticular nuclei, internal capsules, corona radiata, or brain stem did not show any high signal intensity areas on T1-weighted images, whereas the thalamic infarcts did. Sequential studies revealed that these lesions displayed low signal intensity on T2-weighted images at first, and then a high signal intensity area appeared on T1-weighted images. We suggest that these high signal intensity areas on the T1-weighted images in cerebral infarction are caused by hemorrhagic changes at the periphery of the infarction, where blood flow is restored by recanalization or collateral supply.     

Axial vs sagittal T2-weighted brain MR images in the evaluation of multiple sclerosis

Axial and sagittal proton density and T2-weighted MR images (TR 2,500-3,000 ms, TE 15-22 and 85-90 ms) were performed in 50 patients with multiple sclerosis (MS) on a 1.5 T superconductive system. The number of plaques on the axial and sagittal images in the periventricular white matter, the corpus callosum, the brain stem, the cerebellum, and the basal ganglia were counted separately by two independent observers. A total of 858 lesions (mean 17.40 +/- 21.57) were seen on the axial series and 1,196 (mean 24.32 +/- 26.22) on the sagittal scans. More lesions were visualized on sagittal images in the periventricular region (mean 18.79 +/- 21.69 versus 13.34 +/- 16.45; p less than 0.001) and the corpus callosum (mean 3.00 +/- 2.72 versus 0.57 +/- 1.19; p less than 0.001). In the brain stem more lesions were visualized on the axial images (mean 1.55 +/- 2.55 versus 0.87 +/- 1.20; p less than 0.05). In the cerebellum and basal ganglia, scans in the two planes were equivalent (p greater than 0.5). In three patients lesions were seen on the sagittal series, while the axial scans were normal. Sagittal T2-weighted images appear to demonstrate significantly more MS plaques than transverse images, especially in the periventricular region and the corpus callosum. This is explained by partial volume averaging, by the orientation of some cerebral structures (e.g., corpus callosum) with regard to the section plane, and by the longer diameter of the lesions in the axial plane.     

Effect of multislice interference on image contrast in T2- and T1-weighted MR images

Multislice imaging markedly degrades the contrast of T2-weighted MR images as the separation between slices is reduced. Image contrast was measured clinically at 1.5 T and experimentally at 0.15 T as a function of interslice gap width and shown to be in agreement with calculations based on known relaxation times and excitation profiles. Thus, the cause of T2 contrast degradation in multislice sequences is demonstrated. Contrast in T1-weighted sequences is shown to be minimally affected or even slightly enhanced. Selective excitation pulses with better spatial definition will diminish these contrast changes. Since perfect slice profiles can never be achieved, the clinical implications of these findings are discussed for MR imaging. The choice of slice gaps is an important operator-selected parameter in reducing contrast degradation in T2-weighted sequences.