Measurement of synovial lining volume by magnetic resonance imaging of the knee in chronic synovitis

OBJECTIVES: Current methods of monitoring chronic synovitis in a single joint rely on clinical examination derived indices, such as the detection of synovial thickening. This study aimed to develop a reproducible method for quantifying the volume of synovial lining in chronic synovitis using contrast enhanced magnetic resonance (MR) imaging. METHODS: The knees of 18 patients with chronic synovitis were examined (34 studies). A 2D T1 weighted FLASH sequence was used to evaluate the temporal enhancement of synovial structures after intravenous contrast. Synovial lining volume was calculated from subtraction of pre and post-enhancement 3D T1 weighted MP RAGE images with thresholding and pixel counting. Eleven patients were examined before and after intra-articular glucocorticoid (mean interval 14 weeks) and MR data compared with changes in clinical examination derived indices of disease activity. RESULTS: Synovial lining volume varied from 52-267 ml. The coefficient of variation in volume calculation was 3.5% for a single observer and was 3.8% for two observers. Synovial lining volume was quantified in all patients where synovial lining thickening could not be detected clinically. A decrease in synovial lining volume of > 40% was associated with an improvement in synovial lining thickening, detected clinically. Decreases in synovial lining volume were quantified by MR in two of three patients where changes in clinical examination derived indices were inconsistent. CONCLUSIONS: A reproducible method of estimating the volume of synovial lining in patients with chronic synovitis has been developed. MR measurement of synovial lining volume may quantify changes in chronic synovitis that remain unidentified by clinical measures.     

Cost effectiveness of magnetic resonance imaging of the knee

When compared to diagnostic arthroscopy in patients with knee complaints consistent with internal derangement, MR imaging emerges as a cost effective diagnostic supplement to clinical examination. This article concludes that the results of MR imaging can be used as a guide for the management of knee pain.     

Influence of magnetic resonance imaging on indications for arthroscopy of the knee

In a prospective study, magnetic resonance imaging was performed before arthroscopy for all patients (n = 121) with a meniscal tear (n = 125). Criteria of the study were stable cruciate and collateral ligaments, absence of pathologic radiographic findings, and absence of prior surgical interventions of the involved knee joint. In 43 knees (34%), the clinical diagnosis of a meniscal tear was discarded because of the results of the magnetic resonance imaging examination. Synovitis was diagnosed in 16 patients (13%), articular cartilage damage in 10 patients (8%), bone bruise injuries in 10 patients (8%), osteochondritis dissecans in 3 patients (2%), disruption of the inner layer of the medial collateral ligament in 3 patients (2%), and osteonecrosis in 1 patient. The use of magnetic resonance imaging in establishing diagnosis of disorders of the knee joint altered treatment in a significant proportion of patients. Magnetic resonance imaging should be done before arthroscopy of the knee in all cases in which the clinical diagnosis has been reduced to a suspected meniscus injury.     

Quantification of optic nerve blood flow changes using magnetic resonance imaging

PURPOSE: To evaluate the possibilities of magnetic resonance imaging (MRI) for quantification of pharmacologically induced changes in optic nerve microcirculation. METHOD: T2-weighted MRI sequences were used to image the eye, optic nerve, and frontal cortex in rats. Two sets of control images before and one set during Gd (DTPA) infusion were recorded. Blood flow values for two regions of the optic nerve (an anterior part, including the optic nerve head, and a more posterior part) and the frontal cortex were calculated by image analysis from the change in signal intensity, as already reported for cerebral blood flow. For each rat, a control experiment before drug administration and a second experiment 30 minutes after subcutaneous injection of either placebo (n = 7), timolol (n = 7), or SDZ GLC-756, a dopamine D-1 antagonist and D-2 agonist (n = 7), were carried out in a double-blind fashion. RESULTS: Mean basal blood flow values were found between 29.4 and 45.6 ml/100 g per minute in the anterior part of the optic nerve, 38.3 and 42.9 ml/100 g per minute in the posterior part of the optic nerve, and 68.0 and 75.0 ml/100 g per minute in the frontal cortex. Placebo and timolol did not cause significant changes. SDZ GLC-756 significantly increased blood flow by 238% +/- 65% in the anterior part and by 87% +/- 40% in the posterior part of the optic nerve. CONCLUSIONS: These results suggest that MRI provides quantification of optic nerve blood flow and that dopaminergic substances increase optic nerve blood flow.     

Breast magnetic resonance imaging

Breast MRI is becoming an important tool for the improved management of breast cancer. The technical attributes of high contrast, high-resolution breast MRI acquisitions are summarized. The fundamentals of image interpretation are outlined, including lesion enhancement, morphological features, and extent categories. The indications for breast MRI include compromised mammography, staging of disease within the breast and adjacent structures, difficult histology, and other special diagnostic situations. Patients with compromised mammography include previous surgery, radiographically dense breasts, and silicone augmentation. The improved determination of disease extent aids in the management of breast conservation treatment. Certain lesions, particularly lobular carcinoma and ductal carcinoma in situ, can be better managed with the information available with breast MRI. Other potential indications are also discussed, including patients presenting with positive axillary nodes and no known primary, women with a high risk of malignancy, and recently postoperative breasts with positive margins. The need for MRI stereotaxis is reviewed, with indications and potential solutions. The potential future roles for MRI-directed interstitial hyperthermia are outlined.     

Magnetic resonance imaging of knee injuries in children

The appearances of knee injuries on MR imaging are less well documented in children than adults. Some patterns of injury are shared by both groups of patients, e. g. meniscal damage. The frequency of specific injuries may differ, e. g. anterior cruciate ligament (ACL) tear. Congenital abnormality, coexistent pathology and previous treatment of the knee appear to be associated with meniscal problems. Discoid menisci are seen most frequently in children and have unique features on MR scans. Cruciate ligament tears are difficult to diagnose in the smallest children. The ACL may not be identified due to its small size. Normal bone marrow signal may be confused with marrow infiltration or bone microfracture. Radiographically occult fractures around the knee appear to be strongly associated with ligamentous injury as in adult patients. Osteochondral fractures, osteochondral lesions and articular cartilage damage are revealed on MR scans, but their long-term effects are uncertain. It is possible to diagnose a range of knee injuries on MR scans in children. The biggest diagnostic challenge is in pre-school children.     

Contrast media-enhanced magnetic resonance imaging visualizes myocardial changes in the course of viral myocarditis

BACKGROUND: The course of tissue changes in acute myocarditis in humans is not well understood. Diagnostic tools currently available are unsatisfactory. We tested the hypothesis that inflammation is reflected by signal changes in contrast-enhanced magnetic resonance imaging (MRI). METHODS AND RESULTS: We assessed 44 consecutive patients with symptoms of acute myocarditis. Nineteen patients met the inclusion criteria revealing ECG changes, reduced myocardial function, elevated creatine kinase, positive troponin T, serological evidence for acute viral infection, exclusion of coronary heart disease, and positive antimyosin scintigraphy. We studied these patients on days 2, 7, 14, 28, and 84 after the onset of symptoms. We obtained ECG-triggered, T1-weighted images before and after application of 0.1 mmol/kg gadolinium. We measured the global relative signal enhancement of the left ventricular myocardium related to skeletal muscle and compared it with measurements in 18 volunteers. The global relative enhancement was higher in patients on days 2 (4.8+/-0.3 [mean+/-SE] versus 2.5+/-0.2; P<.0001); 7 (4.7+/-0.5, P<.0001); 14 (4.6+/-0.5, P<.0002); and 28 (3.9+/-0.4, P=.009) but not on day 84 (3.1+/-0.3; P=NS). On day 2, the enhancement was focal, whereas at later time points, the enhancement was diffuse. In patients with evidence of ongoing disease, the values remained elevated. CONCLUSIONS: Acute myocarditis evolves from a focal to a disseminated process during the first 2 weeks after onset of symptoms. Contrast media-enhanced MRI visualizes the localization, activity, and extent of inflammation and may serve as a powerful noninvasive diagnostic tool in acute myocarditis.     

Functional magnetic resonance imaging of regional cerebral blood oxygenation changes during breath holding

BACKGROUND and PURPOSE: Recently, noninvasive MRI methods have been developed that are now capable of detecting and mapping regional hemodynamic responses to various stress tests, which involve the use of vasoactive substances such as acetazolamide or inhalation of carbon dioxide. The aim of this study was to assess regional cerebral blood oxygenation changes during breath holding at 1.5 T. METHODS: In 6 healthy volunteers, T2*-weighted gradient echo images were acquired for a total dynamic scanning time of 10 minutes during alternating periods of breath holding and normal breathing at 40-second intervals after inspiration, at 30-second intervals after expiration, and at 18 seconds after expiration. To quantify the relative signal changes, 2.5-minute baseline image sampling with normal breathing was carried out. RESULTS: Repeated challenges of breath holding of various durations induced an overall rise in blood oxygen level-dependent (BOLD) signal intensities. In general, BOLD signal intensity increases were greatest in gray matter and nonsignificant in white matter. Depending on the breath-holding duration and techniques, BOLD signal intensity increases of all activated pixels varied from 0.8% to 3.5%. CONCLUSIONS: The present study demonstrates that cerebral blood oxygenation changes during breath holding can be detected by means of fMRI at 1.5 T. The breath-holding test, a short and noninvasive method to study cerebral hemodynamics with fMRI, could become a useful alternative to the acetazolamide or CO2 test.     

Use of functional magnetic resonance imaging

It has been the goal of this article to provide the reader with a brief background of fMRI, a basic understanding of the techniques of fMRI, and, more importantly, the potential for clinical and experimental studies using fMRI. In contrast to the limited number of installed PET and MEG units, the large installed base of MR imaging scanners (over 1000 installed at least at 1.5 T in the United States) makes fMRI potentially widely available. Initial studies (both clinical and experimental) have been validated and are reproducible in mapping the sensorimotor and visual cortices. The areas of language lateralization and memory are still preliminary at best. As methods to reduce the effects of head motion (due to both bulk head motion and physiologically induced motion) arise, the reliability of fMRI should improve, allowing for more definitive identification of task activation.     

Functional magnetic resonance imaging in macaque cortex

The ability to use fMRI in a monkey model would bridge the gap between the fMRI demonstration of cerebral activation in humans and the cumulative wealth of monkey data on the functional organization of the brain from single electrode mapping, radioisotope and histology studies. We report a new technique for fMRI in an awake co-operative rhesus macaque (Macaca mulatta) in a conventional clinical 1.5T MR scanner and present the first fMRI images from a macaque. Good resolution, signal-to-noise ratio and BOLD response (2.6-4.6%) have been achieved using the manufacturer's standard volume knee coil. T1 values of macaque gray and white matter (1490 ms, 1010 ms respectively) are higher than human brain, whereas T2 values are lower (55 ms, 48 ms respectively). An MR-compatible design for restraining the monkey is also described, along with a suitable EPI sequence for BOLD images, optimized for monkey T2, with voxel sizes from 29 to 61 microl, and MPRAGE sequence for anatomical studies with 0.8 mm isotropic resolution, optimized for monkey T1.     

Advances in magnetic resonance imaging: applications in body imaging

Recent developments in the field of endocrine cell biology and pathology at both morphological and molecular levels are briefly outlined and discussed as a basis for endocrine tumor characterization. The main tools available for identifying the endocrine nature of the tumors, their pathogenetic interpretation. and experimental reproduction with special emphasis on tumor antecedents are reported. Based on this, classifications of endocrine tumors of the pancreas and gastrointestinal tract are developed, covering most clinical (hyperfunctional syndromes included), pathological, and biological patterns, with special emphasis on tumor prognosis.     

Blount''s disease: magnetic resonance imaging

He often begins to answer before you have finished asking your question, but his replies are to the point. He speaks with emotion about the people he hopes to help, particularly children with fatal genetic diseases. 'I prefer to do something: the outcome of doing nothing is perfectly clear', he says. He began sequencing human genes while others were discussing how and when to do so. His methods have been called inelegant, redundant, wasteful, and too 'industrial'. Will his method fail to detect some infrequently transcribed genes? That's all right with him. He is not concerned with finding all the human genes, but rather with the fastest possible route to a useful catalog of most human genes.     

New multimeric magnetic resonance imaging agents

RATIONALE AND OBJECTIVES: The authors investigated the effect of multimerization on the relaxivity of macrocyclic gadolinium (Gd) chelates. The objective was to develop more sensitive magnetic resonance imaging (MRI) contrast agents to study biochemical processes. METHODS: Covalently linked nonionic, macrocyclic, multimeric lanthanide chelates that belong to the classes of dimers, trimers, tetramers, hexamer, and octamer, in the molecular weight range approximately 1 to 5 KDa, were synthesized. The chemical linkage was based on either the amide bond or the 2-hydroxypropylidene bond. Relaxivity values, 20r1, on Gd3+ chelates and hydration numbers, Q, on Tb3+ chelates were determined. RESULTS: Relaxivity values increased with molecular weight and Q values were not affected, the increase in r1 in attributable to the expected increase in the overall rotational correlation time, tau r with an increase in molecular weight. The rigidity of the linkers, which is expected to affect the intrachelate rotational correlation time tau r* that makes a contribution to the overall correlation time, tau r, exerted a noticeable effect. The hydroxyl-based chelates generally had lower r1 values than the amide-based chelates. This is rationalized as arising from the longer and thereby rate-limiting effect of the tau m value for the hydroxyl chelates compared with that reported of the amide-based chelates. This rate limiting effect of tau m becomes a dominant factor controlling attainable enhanced relaxivity when multimers based on traditional chelate designs are used for MRI applications. CONCLUSIONS: Approaches aimed at enhancing relaxivity by modulating the water relaxation time, tau m, will be important for the future development of functional MRI contrast agents for the imaging of biochemical processes.     

Serendipity in diagnostic imaging: magnetic resonance imaging of the breast

BACKGROUND: Magnetic resonance imaging (MRI) of the breast has been proposed as a noninvasive diagnostic test for evaluation of suspicious ("index") lesions noted on mammography and/or clinical breast examination (CBE). However, women may have incidental ("serendipitous") lesions detected by MRI that are not found on mammography or CBE. To understand better whether or not biopsy procedures should be performed to evaluate serendipitous lesions, we estimated the breast cancer risk for women with this type of lesion. METHODS: A decision analysis model was used to estimate the positive predictive value (i.e., the chance that a woman with a serendipitous lesion has cancer) of MRI for serendipitous lesions in women who had an abnormal mammogram and/or CBE suspicious for cancer (where a biopsy procedure is recommended). We restricted the analysis to data from women whose index lesions were noncancerous and used meta-analysis of published medical literature to determine the likelihood ratios (measures of how test results change the probability of having cancer) for MRI and the combination of CBE and mammography. The positive predictive value of MRI was calculated using the U.S. population prevalence of cancer (derived from registry data) and the likelihood ratios of the diagnostic tests. RESULTS: Under a wide variety of assumptions, the positive predictive value of MRI was extremely low for serendipitous lesions. For instance, assuming sensitivity and specificity values for MRI of 95.6% and 68.6%, respectively, approximately four of 1000 55- to 59-year-old women with serendipitous lesions would be expected to have cancer (positive predictive value = 0.44%, 95% confidence interval = 0.24%-0.67%). CONCLUSION: In women with a suspicious lesion discovered by mammography and/or CBE that is found to be benign, serendipitous breast lesions detected by MRI are extremely unlikely to represent invasive breast cancer. Immediate biopsy of such serendipitous lesions may, therefore, not be required.     

Multifunctional magnetic resonance imaging of cerebrovascular disease

Over the last few years magnetic resonance imaging (MRI) has developed into a multipurpose imaging technique. In addition to anatomical information, data can be obtained on perfusion, metabolism and imaging of the vascular anatomy. Especially in the field of neuroradiology the possibilities for obtaining multifunctional information from combined MR examinations are promising. In particular, stroke or stroke-related research benefits from these developments. This article reviews the current status and the potential of newly developed MR techniques with regard to the intracranial hemodynamic changes in patients with severe stenosis or occlusion of the internal carotid artery. The combination of MR angiography, perfusion-weighted MRI and MR spectroscopic imaging seems especially useful in the management of the individual patient.