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1.
Multimodal, biocompatible contrast agents for high magnetic field applications represent a new class of nanomaterials with significant potential for tracking of fluorescence and MR in vitro and vivo. Optimized for high‐field MR applications—including biomedical imaging at 21.1 T, the highest magnetic field available for MRI—these nanoparticles capitalize on the improved performance of chelated Dy3+ with increasing magnetic field coupled to a noncytotoxic Indium Phosphide/Zinc Sulfide (InP/ZnS) quantum dot that provides fluorescence detection, MR responsiveness, and payload delivery. By surface modifying the quantum dot with a cell‐penetrating peptide sequence coupled to an MR contrast agent, the bimodal nanomaterial functions as a self‐transfecting high‐field MR/optical contrast agent for nonspecific intracellular labeling. Fluorescent images confirm sequestration in perinuclear vesicles of labeled cells, with no apparent cytotoxicity. These techniques can be extended to impart cell selectivity or act as a delivery vehicle for genetic or pharmaceutical interventions. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.  相似文献   

2.
Alveolar echinococcosis of the liver: MR findings   总被引:1,自引:0,他引:1  
Nineteen cases of proven hepatic alveolar echinococcosis were examined by magnetic resonance (MR) and the results were compared with CT. Fibrous and parasitic tissue showed low signal both on T1- and, generally, on T2-weighted images. In a few cases a high signal on T2-weighted images may be observed, due either to central necrotic zones or to small peripheral cysts. Central necrosis was more easily identified by MR than by CT. However, MR seemed to be less effective than CT in allowing us to reach a positive diagnosis, due to its inability to show microcalcifications. In addition, MR may not reveal small lesions. In most cases T1-weighted images revealed more clearly than CT did the margins of the lesions and the hepatic extension, especially to hepatic veins, vena cava, and perihepatic spaces.  相似文献   

3.
PURPOSE: Percutaneous ethanol injection therapy (PEIT) of the abnormal parathyroid gland is an effective treatment in patients with chronic renal failure with dialysis that tends to be unresponsive to medication. To evaluate the efficacy of PEIT, we investigated the correlation between serum intact PTH (iPTH), and the findings of MR imaging and 99mTc-MIBI scintigraphy. MATERIALS AND METHODS: PEIT was performed 32 times in 24 patients with secondary hyperparathyroidism. Both MR imaging and MIBI scintigraphy were performed before and after PEIT. The detectability of parathyroid lesions was evaluated by MRI and MIBI scintigraphy with reference to ultrasound (B-mode) findings (as a standard) and the comparison of each treatment was done between imaging changes and serum iPTH levels. RESULTS: In the small parathyroid glands (< 0.5 ml with US), MR images detected abnormal glands in 74.0% (20/27), and MIBI accumulation was observed in 40.7% of the cases. Whereas, MR images and MIBI showed similar detectability (95.0% vs. 90.0%) to large parathyroid glands (> or = 0.5 ml with US). After PEIT, glands in which ethanol was successfully injected showed decreased signal intensity on T2-weighted images and decreased accumulation of MIBI. MR imaging and MIBI scintigraphy showed almost equivalent high sensitivity in evaluating therapeutic changes (73.3% vs. 76.4%) according to our evaluation category of more than 30% reduction of iPTH as effective. However, the specificity of MR imaging was much higher (100%) than that of MIBI scintigraphy in evaluating therapeutic effects. CONCLUSION: In conclusion, MRI provided better detectability of abnormal parathyroid glands than 99mTc-MIBI scintigraphy. The reduction of high signal intensity area after PEIT on T2-weighted MR images is considered an useful therapeutic evaluation guideline than the reduction of MIBI accumulation on scintigraphy.  相似文献   

4.
PURPOSETo compare the efficacy of single-dose gadolinium with magnetization transfer contrast (MTC) with that of triple-dose gadolinium in detecting enhancing multiple sclerosis lesions.METHODSTwenty-one patients with multiple sclerosis were examined with MR imaging first with 0.1 mmol/kg gadolinium (single dose) and then, after 24 to 72 hours, with 0.3 mmol/kg gadolinium (triple dose). T2-weighted fast spin-echo and T1-weighted spin-echo MR images with and without MTC were obtained before contrast administration followed by either T1-weighted spin-echo images with MTC (single dose) or conventional T1-weighted spin-echo images (triple dose), starting 5, 17, and 29 minutes after contrast administration. All images were evaluated in a blinded fashion and scored in random order by two readers. Outcome parameters included number of enhancing lesions, number of active MR examinations (those containing at least one enhancing lesion), contrast ratio (signal intensity of enhancing lesion divided by signal intensity of normal-appearing white matter), and size of enhancing lesions.RESULTSEighty-one percent more enhancing lesions and 49% more active MR examinations were detected when a triple dose of gadolinium was used as compared with a single dose. The level of agreement between readers as to the number of enhancing lesions was significantly higher for triple-dose than for single-dose gadolinium. With triple-dose gadolinium, contrast ratios and areas of enhancement increased by 10% and 33%, respectively. Delayed imaging increased the size of the lesion by 11% on single-dose MTC images and by 18% on triple-dose images.CONCLUSIONTriple-dose gadolinium is more effective (higher sensitivity and interobserver agreement) than single-dose gadolinium in combination with MTC in detecting enhancing multiple sclerosis lesions.  相似文献   

5.
PURPOSE: To investigate the immediate effects of microwave coagulation on rat tumors in various magnetic resonance (MR) images at high magnetic field strength using histopathological examinations as reference. MATERIALS AND METHODS: Tumors implanted in rat femurs were partially thermocoagulated by microwave. Immediately after, T1- and T2-weighted images, diffusion-weighted images (DWIs), and contrast-enhanced T1 weighted images (CE-T1WIs) were acquired with a 7-tesla MR scanner. After measurements, tumors were examined histopathologically with hematoxylin-eosin (HE) staining and histochemically for acid phosphatase activity. RESULTS: Without contrast, boundaries of coagulated areas were unclear on MR images, including apparent diffusion coefficient (ADC) maps. CE-T1WIs clearly showed immediate contrast enhancement of untreated areas of tumor, and the area of enhancement gradually enlarged in 5 min. Quantitative analyses were conducted by classifying tumor areas by contrast enhancement results. Signal intensities of the areas in the MR images showed no significant differences, but at the periphery, ADC values were significantly higher in areas with delayed enhancement than those with immediate enhancement. Compared with histopathological findings, with microwave thermocoagulation, increased ADC value seemed to derive from collection of extracellular fluid in the outer zone, where acid phosphatase activity was attenuated. CONCLUSION: ADC values in the areas with delayed enhancement of CE-T1WIs were higher than those in non-affected areas, but MR images could not show areas of coagulation within tumors. Clear detection of the boundaries of coagulated areas required contrast enhancement, even at magnetic field strength of 7T.  相似文献   

6.
The purpose of this study is to compare the quality of images of coronary arteries obtained with two-dimensional breath-hold coronary MR angiography during peak systole and mid diastole. Two-dimensional coronary MR angiography was performed in eight normal volunteers at peak systole and in mid diastole with a commercial 1.5-T MR imager. An ultrafast gradient-echo sequence with incremented flip angle series and k-space segmentation was used. The image quality grade, length, and proximal diameter of each visualized coronary artery were measured. The highest quality images in systole and diastole were compared. Coronary MR angiography provided high quality images in systole and diastole in 14 of 16 coronary vessels (87.5%). In 8 of 14 vessels (57%), there was no visible coronary MR angiogram image degradation when comparing peak systolic with mid-diastolic images. In 4 of 14 vessels (29%), there was mild MR image degradation. There was significant MR image degradation in only one case (7%). And in one case (7%), there was mild image improvement during systole. The width and length of the visualized coronary vessels did not change significantly from diastole to systole. Existing two-dimensional breath-hold coronary MR angiography provides MR images during peak systole and mid-diastole with little or no perceptible difference in quality.  相似文献   

7.
高场MR与超低场MR诊断脊柱转移瘤   总被引:2,自引:0,他引:2  
目的:探讨两种不同场强MR机对脊柱转称瘤的诊断价值,各自的信号变化以及不同的扫描技术特点,为两种场强MR诊断该疾病提供客观的依据。方法:回顾性总结高场MR(1.5T)与超低场MR(0.04T)诊断脊柱转移瘤各20例,分析其各自的特点。结果:两种场强发现病灶的敏感率均达到100%,敏感序列完全不同,高场是T1W,超低场是T2W,高场机的图像空间分辨率,序列选择,扫描时间等均明显优于超低场。结论:两种场强的MR机诊断脊柱转移瘤敏感,可靠,高场MR能提供更多的病理信息。  相似文献   

8.
PURPOSE: To evaluate the usefulness of a low field MRI system (0.2T; Esaote, Biomedica) for the evaluation of meniscal tears with regard to anatomic site, and to compare the results with findings from a high field unit (1.5T; Siemens, Erlangen). MATERIAL AND METHODS: MRI was performed in 25 patients in a low field (0.2T; Esaote, Biomedica), and a high field (1.5T; Siemens, Erlangen) MRI unit. The images were analyzed for the presence or absence of meniscal tears and the confidence of decision making. Results were further analyzed for the number of identical and unidentical findings on both imaging modalities. In seven patients, arthroscopy was performed and the findings compared with the results from MR imaging. Statistical analysis was performed by chi 2-test, Wilcoxon test and Friedman analysis. RESULTS: Qualitative evaluation of the level of confidence in decision making was significantly superior on high field strength images. When comparing the evaluations from both image modalities in 21 of 25 patients (84%), the diagnosis concerning the presence or absence of meniscal tears was identical. CONCLUSION: Although low field MR imaging might offer diagnostic potential concerning the presence or absence of meniscal tears, the level of confidence in decision making is significantly superior with high field strength imaging, probably reflecting the higher conspicuity of lesions from high field strength units.  相似文献   

9.
Magnetic resonance (MR) is an ideal technique for the evaluation of the pericardium since it enables the combination of high resolution anatomical images of the pericardial layers with functional information concerning the impact of pathology on diastolic heart function and cardiac filling in particular. In comparison with echocardiography, which remains the first choice technique for the study of the pericardium, MR provides larger fields of view allowing the visualisation of the entire chest, higher spatial and contrast resolution and greater reproducibility. The technique becomes particularly useful when ultrasound imaging does not provide adequate diagnostic information or requires further characterisation; 'non-echoic' patients, loculated pericardial effusions, focal thickening of the layers and pericardial masses are usually better assessed with MR. The method also provides valuable diagnostic information for establishing the diagnosis of constrictive pericarditis and to differentiate this condition from restrictive cardiomyopathy. The aim of this paper is to present the role of MR imaging in the assessment of a patient with suspected pericardial disease, and discuss the MR technique, anatomy and the main pathological conditions.  相似文献   

10.
Parkinson plus syndrome: diagnosis using high field MR imaging of brain iron   总被引:13,自引:0,他引:13  
The distribution of iron in the brain was analyzed using high field strength (1.5 T) magnetic resonance (MR) imaging in 14 healthy control individuals and six patients with Parkinson plus syndromes (multisystem atrophy and progressive supranuclear palsy) who were unresponsive to antiparkinsonian therapy. The normal topographic distribution of iron in the brain as indicated by high field MR images coincided precisely with the distribution of iron in the brain as determined by Perls staining for ferric iron. In Parkinson plus syndromes, there were abnormally increased concentrations of iron (decreased T2 relaxation times) in the putamen, and less prominent increases in the caudate nucleus and lateral pars compacta of the substantia nigra. In high field strength MR images of normal patients, the decreased signal intensity in the globus pallidus is more prominent than that of the putamen. In MR images of patients with Parkinson plus syndromes, the decreased signal intensity of the putamen is more prominent than that of the globus pallidus.  相似文献   

11.
PURPOSE: To evaluate the detectability of local hepatocellular carcinoma (HCC) recurrence after transcatheter arterial chemoembolization (TACE) by diffusion-weighted MR imaging in correlation with those of gadolinium-enhanced MR imaging. MATERIALS AND METHODS: Respiratory-triggered diffusion-weighted MR images (b factor, 500 s/mm(2); number of averaging, six were obtained in 25 patients with 39 HCCs. Two independent radiologists evaluated diffusion-weighted MR images, gadolinium-enhanced MR images after TACE, and assigned confidence levels for postoperative HCC recurrence. Apparent diffusion coefficients (ADCs) in HCCs were also measured. Sensitivities and specificities were compared using an extension of the McNemar test. Observer performance was also determined by ROC curve analysis. RESULTS: Local recurrences in 14 HCCs and complete tumor necrosis in 25 HCCs after TACE were determined. Sensitivity for the detection of local HCC recurrence was higher on gadolinium-enhanced MR imaging (82%) than on diffusion-weighted MR imaging (60.7%) for the two readers in combination and separately (P < 0.05). Specificities were comparably high for both sequences. Az values were higher for gadolinium-enhanced MR images (0.92) than for diffusion-weighted MR images (0.74) for readers in combination and separately (P < 0.05). Mean ADC values showed an increase after TACE (P < 0.001). CONCLUSION: Diffusion-weighted MR imaging was not found to be a reliable predictor of local HCC recurrence after TACE as compared with gadolinium-enhanced MR imaging.  相似文献   

12.
MR imaging of the larynx at 1.5 T   总被引:2,自引:0,他引:2  
The normal magnetic resonance (MR) anatomy of the larynx at high field strength (1.5 T) was studied in 2 normal excised larynges and 62 subjects without laryngopharyngeal disease. The two normal excised larynges were imaged using a 1.5 T MR scanner with a 3 in diameter circular surface coil and a GE 9800 CT scanner. The larynges were sectioned transversely and the MR and CT images compared to gross and histologic sections. Unossified hyaline cartilage was intermediate in signal intensity on T1-weighted and proton density images and low in intensity on T2-weighted images. The signal intensity from ossified cartilage was determined by the amount of fatty marrow and was high in intensity on T1-weighted and proton density images and low to intermediate in intensity on T2-weighted images. A chemical shift artifact from high intensity fatty marrow obscured the calcified or ossified cortex of the major laryngeal cartilages along the frequency encoding axis. The epiglottic cartilage demonstrated an intermediate signal intensity on T1-weighted images and higher intensity on proton density and T2-weighted images. The intralaryngeal muscles were well demonstrated as low intensity structures. The conus elasticus and the vocal ligaments were not recognized as distinct structures. However, the quadrangular membrane and a previously undescribed membrane separating the preepiglottic and paralaryngeal spaces were shown on MR as low intensity linear structures. In the 62 subjects, MR at 1.5 T proved excellent for demonstrating the anatomical details of the major laryngeal cartilages, extra- and intralaryngeal muscles, ligaments, and soft tissues including the vocal cords, false vocal cords, laryngeal ventricles, aryepiglottic folds, preepiglottic space, and paralaryngeal spaces. Visibility and intensity of muscles, ligaments, and soft tissues did not depend on age or sex. The intensity pattern of the thyroid and cricoid cartilages demonstrated wide variations in the same sex and age groups, depending on the degree of ossification. However, they did show more high intensity foci in older men than in younger women. Magnetic resonance showed better contrast resolution and finer detail than CT scans in the same subjects. Magnetic resonance imaging at 1.5 T, with either a saddle-shaped neck surface coil or a 3 in diameter circular surface coil, provides high contrast and high spatial resolution images and could be useful for the diagnosis of lesions of the larynx.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   

13.
The purpose of this study was to develop an image enhancement technique to detect acute cerebral infarct regions in brain MR images. Transverse relaxation times for abnormal changes tend to be longer than those for normal tissues. In order to obtain MR images with two different echo times, we employed the fast spin echo sequence. We then employed the image subtraction technique using two T(2)-weighted images to enhance acute cerebral infarct regions. As a result, the areas of acute cerebral infarct regions were enhanced as regions of higher signal than normal regions of brain tissue. Further, high signal areas in dual echo subtraction images corresponded to cerebral infarct regions of high signal areas in diffusion weighted images (DWI). We found that the image subtraction technique is useful to enhance very subtle regions of acute cerebral infarction in MR images. Because we employ the difference between transverse relaxation times for normal and abnormal tissues, which does not depend on the strength of the magnetic field, the dual echo subtraction method can be used in many hospitals.  相似文献   

14.
Gadoxetate disodium is a widely used magnetic resonance (MR) contrast agent for liver MR imaging, and it provides both dynamic and hepatobiliary phase images. However, acquiring optimal arterial phase images at liver MR using gadoxetate disodium is more challenging than using conventional extracellular MR contrast agent because of the small volume administered, the gadolinium content of the agent, and the common occurrence of transient severe motion. In this article, we identify the challenges in obtaining high-quality arterial-phase images of gadoxetate disodium-enhanced liver MR imaging and present strategies for optimizing arterial-phase imaging based on the thorough review of recent research in this field.  相似文献   

15.
PURPOSE: The purpose of this study was to determine the diagnostic performance of magnetic resonance (MR) obtained with intra-articular contrast medium in the evaluation of recurrent meniscal tears using low-field extremity-only and high-field whole-body magnets. MATERIALS AND METHODS: Postoperative standard MR examinations and MR arthrographies of 95 knees were reviewed. Patients experiencing pain and disability after meniscal repair underwent standard MR and MR arthrography (Gadoterate meglumine 0.0025 mmol/ml) on both a 0.2-T and 1.5-T magnet. In 52 of 95 patients, second-look arthroscopy was performed; in the remaining 43 of 95 patients, clinical follow-up was used as the standard of reference. Sensitivity, specificity, positive and negative predictive values as well as accuracy of MRI/MR arthrographic signs as meniscal morphologic changes and the presence of contrast medium tracking into the tear at T1- and T2-weighted sequences in the detection of recurrent meniscal tears were determined. RESULTS: All MR and MR arthrograpic signs were sensitive in the detection of recurrent tears (range 80-91%). Abnormal meniscal morphology had low specificity [26% (13/50)] for both the 0.2-T and 1.5-T scanner, whereas accuracy was 55% (52/95) and 57% (54/95), respectively. The presence of contrast medium within the meniscus substance on T2-weighted images had higher value of specificity [84% (42/50)] and accuracy [84% (80/95)] by using low field strength magnet than by using high field strength magnet [74% (37/50) and 81% (77/95), respectively]. Whereas, the increased intrameniscal signal intensity extending to the meniscal surface at T1-weighted sequences after intra-articular contrast medium administration had lower specificity and accuracy on 0.2-T images [84% (42/50) and 82% (78/95), respectively] than on 1.5-T images [90% (45/50) and 88% (84/95), respectively]. CONCLUSION: A diagnosis of recurrent meniscal tear in a previously arthroscopically repaired meniscus can be made both on 0.2-T and 1.5-T magnets on the basis of increased signal on T2-weighted and T1-weighted images in the presence of intra-articular contrast material.  相似文献   

16.
PURPOSE: We studied 11 healthy subjects were evaluated using cine MR imaging comparing HASTE and gradient echo sequences. Materials and methods :HASTE is a high-speed turbo-spin echo T2-weighted sequence. All examinations were performed using dynamic MRI using a simple process allowing acquisition of images at different stages during flexion and extension. The cine MR evaluation was obtained by rebuilding a cine-loop sequence. RESULTS: HASTE sequence provides a myelographic effect of the cervical spine. The size, the pattern and the movements of the cervical spine, the spinal cord, as well as the functional reserve of cerebro-spinal fluid are analysable. CONCLUSION: Because of its very high speed, HASTE sequence is particularly useful for cine MR imaging.  相似文献   

17.
Magnetic resonance (MR) imaging of the abdomen and pelvis with use of gastrointestinal (GI) contrast agents is slowly emerging as a valuable diagnostic tool. In the past few years, considerable effort has been expended on developing an oral contrast agent to serve as a bowel marker during abdominal and pelvic imaging. Four major categories of agents have been studied: compounds with positive contrast-enhancing characteristics (ie, which increase signal intensity), which may be either miscible or immiscible with bowel contents, and compounds with negative contrast-enhancing characteristics (ie, which decrease signal intensity), which also may be miscible or immiscible. Compared with precontrast images, MR images acquired after administration of GI contrast agents have shown increased anatomic delineation of the bowel lumen, pancreas, and paraaortic nodes, allowing increased detection of pancreatic lesions, improved assessment of bowel wall lesions, and distinction between intrahepatic and extrahepatic lesions. This review focuses on the general physics and requirements for intraluminal GI contrast media for MR imaging, the currently used intraluminal agents and their regulatory status, current and near-future availability, and cost considerations.  相似文献   

18.
Invasion of laryngeal cartilage by cancer: comparison of CT and MR imaging   总被引:2,自引:0,他引:2  
Forty-two patients with laryngeal carcinomas were examined with computed tomography (CT) and magnetic resonance (MR) imaging. The accuracy of both CT and MR imaging in the depiction of cartilage invasion was evaluated in 16 patients by comparing findings at CT and MR with pathologic findings. Calcified cartilage that has been invaded by cancer is frequently seen on CT scans as having an intact contour. Tumor approaching nonossified cartilage may simulate cartilage invasion. On T1-weighted MR images, invaded marrow of ossified cartilage is of intermediate signal intensity, allowing it to be differentiated from normal bone marrow. On proton-density images, tumor is of increased signal intensity, which allows it to be differentiated from nonossified cartilage. In our experience, the specificities of CT and MR imaging were approximately equal (91% and 88%, respectively), but CT had a considerably lower sensitivity than MR (46% vs. 89%). Gross movement artifacts, which resulted in nondiagnostic images, occurred in 16% of the MR examinations. MR imaging is recommended as the modality of choice in the diagnosis of cartilage invasion.  相似文献   

19.
The aim of the study was to investigate the feasibility of using digital subtraction in contrast-enhanced MR imaging of the brain to reduce the MR contrast dosage without jeopardizing patient care. Fifty-two patients with intracranial lesions, either intra-axial or extra-axial, detected by computerized tomography were selected for contrast-enhanced MR imaging with half-dose and full-dose of gadopentetate dimeglumine. The half-dose unsubtracted, full-dose unsubtracted, and half-dose subtracted MR images were visually assessed by counting the number of enhancing brain lesions in the images and quantitatively analyzed by computing their lesion contrast-to-background ratios (CBR). The visual conspicuity of the half-dose subtracted MR images was comparable to that of the full-dose unsubtracted MR images ( p>0.05), whereas the CBR of the half-dose subtracted images was approximately two to three times higher than that of the full-dose unsubtracted images. The half-dose subtracted T1-weighted spin-echo images might be able to replace the conventional standard-dose T1-weighted spin-echo images in MR imaging of the brain.  相似文献   

20.
PURPOSEWe compared conventional spin-echo (CSE) with fast spin-echo (FSE) dual-echo MR images to determine which of these sequences was better able to depict spinal cord abnormalities in patients with multiple sclerosis (MS).METHODSCSE and FSE dual-echo MR images were obtained in 37 patients with MS and in six healthy control subjects, all of whom were examined on a 1.0-T MR unit with a phased-array coil and cardiac triggering. Two blinded interpreters graded the MR studies, first separately and then by consensus. Images were scored for presence of artifacts, number of focal lesions, and presence of a diffuse increase in signal intensity.RESULTSNo abnormalities were seen in the volunteers. The CSE sequences were significantly less hindered by MR imaging artifacts than were the FSE sequences. Interobserver agreement was slightly higher for the CSE than the FSE sequences. After reaching a consensus, the observers found that both CSE and FSE techniques enabled detection of approximately the same number of focal lesions; however, in three patients, small single lesions seen on the CSE images were missed on the FSE images. Also, depiction of a diffuse increase in signal intensity was better on the CSE images. As a result, more patients had abnormal findings on the CSE sequences than on the FSE sequences (35 versus 31).CONCLUSIONCardiac-triggered dual-echo FSE sequences are almost as good as CSE sequences for depicting spinal MS lesions. Therefore, in cases of established spinal MS, FSE techniques may be as effective as CSE techniques. Because sensitivity for subtle abnormalities is lower with FSE imaging, CSE remains the preferred technique for patients with suspected MS of the spinal cord.  相似文献   

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