Multiple sclerosis: gadolinium enhancement in MR imaging

Magnetic resonance (MR) images--both nonenhanced and enhanced with gadolinium DTPA/dimeglumine (Gd)--were compared with high-iodine (88.1 g I) computed tomographic (HICT) scans in demonstrating lesions in 15 patients known to have multiple sclerosis (MS). T1-weighted, mixed (T1, proton density, and T2), and T2-weighted MR pulse sequences were used. More than 20 lesions in each of 14 patients were demonstrated by pre-Gd mixed images and T2WI. Nine patients had clinical symptoms of active disease. Gd-enhanced T1WI showed at least one lesion that appeared to correspond with newly reported symptoms or signs. In addition, three clinically stable patients showed enhancement. Enhancement was best seen on 3-minute T1WI. HICT scans showed enhancement in four of the nine patients with active disease and in none of five clinically stable patients. Gd-enhanced MR imaging appears to be more sensitive than HICT in the detection of the transient abnormalities of the blood-brain barrier that occur in patients with active MS and appears capable of distinguishing active lesions that may correspond to the anatomic regions responsible for abnormal clinical findings.     

Hepatic tumors: Magnetization transfer MR imaging with gadolinium enhancement

Thirty patients with 15 hepatocellular carcinomas, 10 metastases, four hemangiomas, and one cholangiocarcinoma underwent magnetic resonance imaging at 1.5 T with T1-weighted, T2- weighted spin-echo (SE) images, gradient-echo (GRE) magnetization transfer (MT) images, and gadolinium-enhanced T1-weighted SE and MT- GRE images. The MT effect and lesion-liver contrast-to-noise ratio (C/N) were calculated and visual assessment (qualitative analysis) performed for unenhanced and enhanced MT-GRE images and enhanced Tl-weighted SE images. The C/N values for hepatic adenocarcinomas (seven metastases and one cholangiocarcinoma) and hemangiomas were larger for enhanced MT-GRE images (adenocarcinoma, 8.4 ± 2.3 [P < 0.01); hemangioma, 24 ± 2.1 [P < 0.05]) than for enhanced GRE images (5.0 ± 1.9 and 18 ± 2.7, respectively). These enhancing tumors had the highest scores in the qualitative analysis. Enhanced MT-GRE images showed no advantage for depiction of hepatocellular carcinomas relative to the other images.     

Effect of field strength on gadolinium enhancement in MR imaging

This studv was designed to evaluate the influence of magnetic field strength on the relative enhancement effect (RE) of gadolinium (Gd)-chelates. Dilution series of two paramagnetic contrast agents (Gd-DTPA and Gd-DOTA) were examined in three commercially available MR systems. operating at different field strengths (02 T, 1. T, and 1.5 T). The RE was plotted against Gd concentration. The highest increases in signal intensity occurred with Gd concentrations of approximately L.0 mmol/L. No significant difference in RE was observed between MR systems ranging in field strength from 0.? T to 1.5 T. The RE of Gd-DTPA and Gd-DOTA was found to he equivalent.     

Mediastinal masses: MR imaging

Seventy-five patients with mediastinal masses were imaged with magnetic resonance (MR). Results were analyzed with regard to the ability of MR to demonstrate the masses, their morphology, and their encroachment or displacement of blood vessels and airways. T1 values were determined in 53 patients and T2 values in 59. Hydrogen density and percentage of contrast relative to muscle and fat were also obtained in 53 and 59 patients, respectively. MR images were compared with computed tomography (CT) scans, which were available in 45 patients. MR depicted all masses and demonstrated compromise of vessels and cardiac chambers owing to the inherent contrast between the masses and cardiovascular structures. Bronchogenic carcinoma had very long relaxation values for T1 and T2, while chronic inflammatory processes had intermediate values for T1 and T2, thus appearing less intense than bronchogenic carcinoma on T2-weighted images. Other neoplasms demonstrated T1 and T2 values between these two disease groups. Masses appeared less homogeneous on MR images than on CT scans, and vascular compromise was better assessed with MR. Thus, MR imaging is a completely noninvasive technique for the evaluation of mediastinal masses. While the anatomic information is comparable to that produced by CT, MR provides some insight into the composition of the mass.     

Atlantoaxial joints: patterns of gadolinium enhancement with MR imaging in normal subjects

OBJECTIVE: To evaluate normal patterns of enhancement of signal intensity in and about the atlantoaxial joints following intravenous administration of a gadolinium-containing contrast agent. METHODS AND MATERIAL: Fat-suppressed axial T1 weighted SE images were obtained in 12 patients without evidence of inflammmatory arthritis before and immediately after intravenous administration of a gadolinium-containing contrast agent. Patterns of enhancement of signal intensity in and about the atlantoaxial joints were evaluated qualitatively. RESULTS: Four different MR imaging patterns were observed: no enhancement of signal intensity, enhancement in the form of a single punctate region, enhancement in a confluent pattern, and bandlike enhancement. CONCLUSION: Enhancement occurs around the odontoid process in patients without evidence of rheumatoid arthritis (RA). The dividing line between early synovitis and normal enhancement seems broader than expected. The reasons remain unclear and warant further studies.     

Cerebrospinal fluid changes after intravenous injection of gadolinium chelate: assessment by FLAIR MR imaging

Fluid-attenuated inversion recovery (FLAIR) sequence is currently used in clinical practice. Some reports emphasize the possibility that, in pathologic conditions, intravenous injection of gadolinium chelates may lead to an increased signal inside the cerebrospinal fluid (CSF). The aim of this study was to evaluate the presence of CSF signal changes in pathologic conditions causing blood-brain barrier disruption or neovascularization when imaging is performed after intravenous injection of gadolinium. We obtained FLAIR sequences after gadolinium injection from 33 patients affected by different intracranial pathologies and 10 control subjects. Patients were affected by ischemic stroke in the subacute phase, from 2 to 7 days from onset of symptoms (12 patients), meningiomas (8 patients), high-grade gliomas (5 patients), previous surgical procedures for intra-axial neoplasms (5 patients), and multiple sclerosis with active plaques (3 patients). Magnetic resonance imaging was performed in patients and controls using a 1.5-T magnet, using T2- and T1-weighted FLAIR sequences. The FLAIR sequence was acquired before and 1–3 h after injection of a standard dose of gadolinium. In those patients affected by ischemic lesions, FLAIR sequences were repeated the next days and 3–4 days later. The CSF signal was visually evaluated by two readers and scored from 0 to 3 depending by the degree of enhancement. The location of CSF signal changes (close to the lesion, hemispheric, or diffuse) was also considered. The CSF signal was markedly increased after 3 h from intravenous injection of gadolinium in all the patients with stroke, in those with previous surgery, and in those with high-grade gliomas whose neoplasm's surface was in contact with the subarachnoid spaces (SAS) or ventricles; a strong enhancement was also evident inside the necrotic component of the tumor. The CSF changes were more evident close to the pathology and/or in the hemisphere involved by the pathology. Moderate CSF enhancement was observed in the SAS close to meningiomas. No signal changes were evident in all the others. In those patients with stroke imaged in the following days, CSF signal showed to be diffuse to both hemispheres the next day and returned to normal values within 2 days. In patients affected by pathologies with blood-brain barrier breakdown or neovascularization close the SAS or the ventricles, CSF changes, related to gadolinium leakage, are likely when FLAIR sequences are acquired 2–24 h after i.v. injection of the contrast. This pattern should be known in order to differentiate it from that of subarachnoid hemorrhage. Electronic Publication     

Pancreaticobiliary duct changes of periampullary carcinomas: quantitative analysis at MR imaging

Purpose

To quantitatively analyse the pancreaticobiliary duct changes of periampullary carcinomas with volumetric interpolated breath-hold examination (VIBE) and true fast imaging with steady-state precession (true FISP) sequence, and investigate the value of these findings in differentiation and preoperative evaluation.

Materials and methods

Magnetic resonance (MR) images of 71 cases of periampullary carcinomas (34 cases of pancreatic head carcinoma, 16 cases of intrapancreatic bile duct carcinoma and 21 cases of ampullary carcinoma) confirmed histopathologically were analysed. The maximum diameter of the common bile duct (CBD) and main pancreatic duct (MPD), dilated pancreaticobiliary duct angle and the distance from the end of the proximal dilated pancreaticobiliary duct to the major papilla were measured. Analysis of variance and the Chi-squared test were performed.

Results

These findings showed significant differences among the three subtypes: the distance from the end of proximal dilated pancreaticobiliary duct to the major papilla and pancreaticobiliary duct angle. The distance and the pancreaticobiliary duct angle were least for ampullary carcinoma among the three subtypes. The percentage of dilated CBD was 94.1%, 93.8%, and 100% for pancreatic head carcinoma, intrapancreatic bile duct carcinoma and ampullary carcinoma, respectively. And that for the dilated MPD was 58.8%, 43.8%, and 42.9%, respectively.

Conclusion

Quantitative analysis of the pancreaticobiliary ductal system can provide accurate and objective assessment of the pancreaticobiliary duct changes. Although benefit in differential diagnosis is limited, these findings are valuable in preoperative evaluation for both radical resection and palliative surgery.     

肥厚性心肌病:对比剂增强心血管MRI延迟强化定量分析

目的确定重复性最好的半自动灰阶阈值技术对大样本肥厚性心肌病(HCM)病人钆延迟强化(LGE)的定量。材料与方法研究由参与机构的内部审查委员会核准,所有     

Evaluation of adrenal masses with gadolinium enhancement and fat-suppressed MR imaging

A study was undertaken to determine the ability to characterize benign and malignant masses with unenhanced and contrast material-enhanced fast lowangle shot and fat-suppressed spin-echo magnetic resonance (MR) imaging. Thirty patients with adrenal masses detected at computed tomography (CT) underwent MR imaging within 14 days after CT. CT and MR images were interpreted in a prospective, blinded fashion. Sixteen patients had 20 benign adrenal masses, and 14 patients had 18 malignant masses. Quantitative measurements included percentage of contrast enhancement on immediate postcontrast dynamic images and periphery - center signal-to-noise ratio (S/N) on gadolinium-enhanced fat-suppressed images. Qualitative evaluation included determination of the regularity of lesion margins, homogeneity of signal intensity, and local extension. MR imaging depicted all adrenal masses discovered at CT examinations. Lesions ranged in diameter from 1 to 15 (mean, 4.4) cm. No significant difference was observed in percentage of contrast enhancement between benign (90.5% ± 59.0 [standard deviation]) and malignant (110.5% ± 116.4) masses. A difference was observed between periphery - center S/N for benign (?.05 ± 1.5) and malignant (7.7 ± 9.8) masses; overlap between the two, however, occurred. Qualitative evaluation allowed correct characterization of 32 of 38 masses, comparing favorably with CT, which allowed characterization of 30 lesions.     

Retinoblastoma: Abnormal gadolinium enhancement of anterior segment of eyes at MR imaging with clinical and histopathologic correlation

PURPOSE: To evaluate abnormal gadolinium enhancement of the anterior segment of eyes harboring retinoblastoma at magnetic resonance (MR) imaging and correlate this finding with clinical and histopathologic information. MATERIALS AND METHODS: Three neuroradiologists examined 46 eyes with 34 retinoblastomas in 25 children on gadolinium-enhanced T1-weighted orbital MR images obtained shortly after contrast material injection for evidence of abnormally high signal intensity in the anterior segment. Twenty-two of the 34 affected eyes were enucleated, and six of these 22 eyes were treated with preenucleation adjuvant therapy. Thus, correlation of the clinical, MR imaging, and histopathologic findings in 16 eyes was performed. Statistical analysis was performed with nonparametric methods (Fisher exact test). P <.05 indicated a statistically significant difference. RESULTS: Fourteen of the 34 affected eyes showed abnormal gadolinium enhancement of the anterior segment. Regarding the 16 eyes evaluated for statistical analysis, a significant correlation (P =.011) between abnormal gadolinium enhancement of the anterior segment and histopathologically documented optic nerve infiltration was noted. A trend toward an association between abnormal enhancement and elevated intraocular pressure (P =.215), tumor growth beyond the equator at MR imaging (P =.125), and histopathologically proved iris neoangiogenesis (P =.182) also was noted. Histopathologic evidence of optic nerve and/or choroid infiltration correlated significantly (P =.001; sensitivity, 100% [nine of nine eyes]; specificity, 86% [six of seven eyes]) with abnormal enhancement. CONCLUSION: Abnormal gadolinium enhancement of the anterior segments of eyes harboring retinoblastoma seems to indicate more aggressive tumor behavior.     

Multilocular cystic nephroma: MR imaging appearance with current techniques,including gadolinium enhancement

The purpose of the study was to define the MRI appearance of multilocular cystic nephroma (MLCN), using current MR techniques, including gadolinium (Gd)-enhanced sequences. Seven patients with MLCN underwent MR imaging with the following sequences: T1-weighted spin echo with fat suppression (TIFS, five patients), T1-weighted spoiled gradient echo (SGE, seven patients), T2-weighted fast spin echo (two patients), and Gd-enhanced TIFS (seven patients) and SGE (seven patients). MLCN was histologically proven by resection of the mass in six patients and by observation of typical imaging features with stability in appearance over a 6-month period in one patient. Lesion morphology and signal intensity (SI) features were retrospectively evaluated. MRI features of MLCN included a solitary cystic lesion with thin internal septations in six patients and a cluster of closely grouped cysts similar in size in one patient. Individual cystic spaces demonstrated SI, varying from low to high on T1-weighted images in three patients and demonstrated low-to-intermediate SI in four patients. Herniation of the lesions into the renal collecting system and thin enhancing septa were demonstrated in all patients. A complex cystic renal lesion with enhancing septa and herniation into the renal collecting system are the characteristic MR findings of MLCN. The direct multiplanar capability of MR may optimally show the relationship of MLCN to the renal pelvis and, thus, facilitate correct diagnosis.     

MR成像后锌金属置换反应和钆潴留的个案报道

1例因假牙粘合剂导致慢性锌中毒的病人,可能由于金属置换反应,行MRI检查后在体内发现钆潴留。螯合治疗期间,排泄的尿液中发现有高浓度的钆(注射钆29d     

Skeletal muscle lymphoma: observations at MR imaging

 We present the MR appearances of three patients with biopsy-proven primary lymphoma of skeletal muscle. In each case lymphoma resulted in bulky expansion of the involved muscle, homogeneously isointense to skeletal muscle on T1-weighted images, homogeneously hyperintense to skeletal muscle on T2-weighted images and diffusely enhancing following intravenous administration of gadopentate dimeglumine.     

Renal masses: quantitative assessment of enhancement with dynamic MR imaging

PURPOSE: To establish a quantitative magnetic resonance (MR) imaging contrast enhancement criterion for distinguishing cysts from solid renal lesions. MATERIALS AND METHODS: Regions of interest were measured in 74 patients with renal lesions evaluated by means of dynamic contrast material-enhanced MR imaging with serial breath-hold spoiled gradient-echo acquisitions. Sensitivity for renal tumors and specificity for renal cysts were established by using percentage of enhancement thresholds that varied between 5% and 35%. RESULTS: The mean percentage of enhancement at MR imaging for the 50 renal cysts was less than 5%; for the 50 renal tumors, it was 97% or higher. With use of a threshold percentage of enhancement of 15% and results obtained between 2 and 4 minutes after administration of contrast material, all malignancies (sensitivity for tumor, 100%) were diagnosed, and there were 6% or fewer false-positive tumor diagnoses. Lower thresholds resulted in unacceptably high false-positive rates (ie, cysts that appeared to enhance-pseudoenhancement), whereas higher threshold values (>20%) resulted in an unacceptably lower sensitivity for tumors. CONCLUSION: The optimal percentage of enhancement threshold for distinguishing cysts from malignancies with the imaging technique prescribed was 15%, and the optimal timing for measurement was 2-4 minutes after administration of contrast material.