Current uses of gadolinium chelates for clinical magnetic resonance imaging examination of the liver

The use of gadolinium chelates has become an integral part of magnetic resonance imaging (MRI) of the liver and extrahepatic abdomen. Although liver specific contrast agents are now available, gadolinium chelates continue to offer significant advantages for abdominal MRI. The gadolinium chelates uniquely provide important information about tumor perfusion that is key in our assessment of liver masses. These paramagnetic contrast agents assist with liver lesion detection, characterization, and in establishing the volume of viable perfused tumor. Gadolinium chelates are equally important for MRI of the extrahepatic abdomen. The interstitial accumulation of these agents within peritoneal, omental, and gastrointestinal tumor produces marked enhancement and is key in accurate tumor staging. Depiction of lesions within solid visceral organs such as the pancreas, kidneys, and spleen is also improved following gadolinium injection. The versatility of this workhorse contrast agent assures that gadolinium chelates will continue to occupy a central role in any busy abdominal MRI practice.     

Beta-blockers: a time for reappraisal

Recent studies have shown that SPECT bone scintigraphy is valuable to detect meniscal tears of the knee. This has not been formally assessed in a prospective study, and no substantive study has compared bone SPECT with other noninvasive diagnostic methods. One hundred consecutive patients referred to an orthopedic surgeon with undiagnosed knee pain were assessed by clinical examination, MRI, SPECT bone scintigraphy, and arthroscopy. The MRI and SPECT bone scan findings were reported blinded to other information. Using arthroscopy as a gold standard, both MRI and SPECT showed high diagnostic ability to detect meniscal tears, with respective sensitivity rate, specificity rates, and positive and negative predictive accuracies of 80%, 71%, 84%, and 71% for MRI and 84%, 80%, 88%, and 76% for SPECT. Some meniscal tears were detected by MRI alone (n = 5) or SPECT alone (n = 8). SPECT bone scintigraphy is a suitable alternative to MRI to detect meniscal tears. The comparable diagnostic ability of SPECT bone scintigraphy implies that it can be used successfully when MRI is unavailable or unsuitable.     

The significance of circadian organization for longevity in the golden hamster

INTRODUCTION: Altered patellofemoral biomechanics may result in pain, instability and early involutive processes. Magnetic Resonance Imaging (MRI), with its panoramic capabilities, has proved to be an effective technique in the study of knee extensor complex changes. The diagnostic advantages of dynamic studies of patellofemoral kinetics are reported in the recent scientific literature. We investigated the diagnostic potentials of passive studies of the knee extensor complex with sagittal and axial cine MRI. Then, we developed and optimized an innovative study method overcoming the limitations of the other dynamic techniques for the correct assessment of patellofemoral biomechanics. MATERIAL AND METHODS: We studied the knee with a .2 T permanent magnet dedicated to the limbs and acquired the images in different positions of flexion-extension with T1-weighted SE and T2-weighted GE sequences. We examined 21 healthy volunteers and 37 of 38 patients with anterior knee joint pain of suspected patellofemoral origin. All the images needed for dynamic studies were acquired in about 20 minutes. For the scan planes not to be affected by patellar motion in the different degrees of knee extension, it is necessary to acquire single axial images to be edited in cine motion afterwards. Each acquisition is aligned along sagittal reference planes depiciting always the same patellar aspect. RESULTS: Significant correlations were found between clinical and cine MR findings in 25 patients. In particular we depicted some extensor complex impingement conditions missed at conventional MRI, which clarified the role played by patellar dysplastic changes in cartilage microtraumas. Our technique was accurate, quite easy to perform and repeatable. We performed cost-effective dynamic studies which were useful in the evaluation of patients with anterior knee pain in whom conventional MRI had failed to provide enough information. CONCLUSIONS: Our technique differs from other passive or active dynamic studies reported on in the literature because the patellar volume does not change during acquisitions. This permits to decrease morphological changes and to simplify, on cine MR reconstructions, the specific analysis of patellofemoral dynamics during flexion-extension. Fewer morphological changes also mean a more accurate analysis showing the role of patellar dysplasia in cartilage microtraumas. Our dynamic MR protocol is accurate, easy to perform and to repeat; it allows dynamic studies in the patients with poor static MR findings.     

Correlation of MRI and arthroscopic diagnosis of knee pathology in children and adolescents

The accuracy of magnetic resonance imaging (MRI) in diagnosing knee pathology in the pediatric and adolescent population is not well established. The purpose of this study was to correlate the findings of MRI and knee arthroscopy in children and adolescents. One hundred and eight consecutive knee arthroscopies performed in patients ages 4-17 years between 1992 and 1996 were retrospectively reviewed. Fifty-three of these patients underwent preoperative MRI. Age-related comparisons were then made between MRIs and observed intraoperative meniscal and anterior cruciate ligament pathology. The pediatric group (ages 4-14 years) was demonstrated to have an appreciable decrease in sensitivity, specificity, positive predictive value, and accuracy for essentially all categories of pathologic changes. Conversely, negative predictive values for the pediatric group exceeded those of the adolescent group (ages 15-17 years) in each category. The ability of MRI to predict intraarticular knee pathology among adolescents is comparable to that in adults, whereas it is much less accurate in the pediatric population.     

Arthroscopy: possibilities and limitations in the diagnosis and therapy of meniscus lesions

The menisci consist of fibrocartilage and are an important supporting structure of the knee joint. They are poorly vascularized and have to withstand a high mechanical strain and load; therefore, lesions are common, especially on the medial side. Meniscal lesions are among the most frequent surgical procedures in orthopedic surgery. Meniscal lesions are diagnosed by a careful clinical examination in 80% of all cases in spite of modern imaging techniques such as magnetic resonance imaging (MRI). In the last 15 years, arthroscopic meniscectomy has become the 'golden standard' of therapy. Arthroscopy provides a powerful tool to precisely locate and classify the type of meniscus injury and to perform arthroscopic meniscectomy at the same time. This means less morbidity, reduced hospitalization time and earlier return to work and hence reduced costs. The endoscopic technique allows to exactly remove the damaged parts of the meniscus with precision instruments (partial meniscectomy). Former open techniques only allowed the complete removal of the meniscus. The arthroscopic techniques used nowadays allow a preservation of the functionally important edge of the meniscus, which is responsible for the stability and the biomechanics of the knee joint and can thus prevent an early onset of arthrosis. In rare cases of peripheral meniscal tears in young patients, arthroscopic refixation is an advantageous treatment option. Partial arthroscopic meniscectomy and arthroscopic meniscus refixation are challenging therapeutic procedures that require a trained and experienced orthopedic surgeon. Today diagnostic arthroscopy is more and more abandoned in favour of noninvasive and reliable MRI techniques. MRI is also useful in cases of previous knee surgery and clinically unclear findings, but should not be used on a routine basis. In differential diagnosis, the orthopedic surgeon always has to evaluate the MRI findings as to their impact. Today, arthroscopic knee surgery is a reliable, technically sophisticated and standardized technique to treat meniscal damages of all patients. There is a relatively low rate of complications, provided that the indication for the procedure is critically applied and restricted to patients with sufficient clinical and MRI findings.     

Meniscal lesions

The polymorphism and richness of arthrographic imaging and MRI of meniscal lesions require a perfect understanding of the anatomy of the menisci and the mechanisms of production of the lesions. Arthrography remains the reference diagnostic investigation with a good sensitivity and excellent spatial resolution. However, it is an invasive and operator-dependent technique. MRI of the knee, a non-invasive and independent method, allows the diagnosis of the majority of meniscal lesions. By using specific surface coils and appropriate sequences, MRI constitutes complete imaging technique allowing examination of all anatomical structures of the knee in all planes. Once MRI becomes more widely available, it should replace arthrography in the majority of clinical situations. The indications for arthrography will then be confined to contraindications of MRI.     

Traumatic hemarthrosis of the knee joint--clinical significance of nuclear magnetic resonance tomography

A prospective study was performed on 94 patients with hemarthrosis of the knee to assess the value of MR imaging (MRI) in detection of bleeding sources and selection of therapy modalities. Patients were examined clinically within a week after knee trauma; the investigations performed included puncture of the joint to confirm hemarthrosis, a conventional X-ray to exclude fractures, MRI and arthroscopy. MRI was performed for diagnosis of acute lesions, definition of bleeding sources by morphological criteria, and allocation of patients to conservative or surgical therapy. Arthroscopy was performed to control MRI, to visualize bleeding sources, and to maintain therapy if necessary. The 94 patients were found on arthroscopy to have a total of 123 bleeding sources, which were correctly defined by MRI in each of 107 cases as an acute lesion communicating with the joint space; 16 bleeding sources were not found and there were 10 false-positive reports. In keeping with our treatment strategies, arthroscopy disclosed lesions requiring surgical therapy in 77 of 94 patients (82%) and lesions that would be adequately treated by conservative therapy in 17 of 94 patients (18%). MRI predicted surgical or conservative therapy correctly before arthroscopy in 83 of 94 patients (88%). In conclusion, MRI has a high predictive value in definition of acute lesions that will lead to hemarthrosis of the knee. This noninvasive method allows screening out of the relatively small portion of patients without severe lesions, who then do not have to be subjected to further invasive therapy.     

Current status of imaging procedures in the diagnosis, prognosis and monitoring of osteoarthritis

X-ray, magnetic resonance imaging (MRI) and arthroscopy are the methods most widely used to assess the status of osteoarthritic joints. How do these methods compare? As diagnostic tools, what is the relative sensitivity of X-ray versus MRI, arthroscopy versus MRI and arthroscopy versus X-ray? Which imaging modalities can be used for predicting progression? Scintigraphy and MRI can assess the degree of cellular activity in the tissues of a joint, which may help in prognosis. Are the methods proven and are they reliable? Recommendations for clinical trials in knee osteoarthritis, state it is essential that reproducible radiographs are obtained for reliable assessment of progression. Two radiographic views of the knee have been proposed; which provides the more reliable assessment, the knee in extension or semi-flexed? Compared with standard radiography, does microfocal radiography make a difference to patient numbers required for drug trials?     

Tunneled hemodialysis catheters: use of a silver-coated catheter for prevention of infection--a randomized study

OBJECTIVE: The purpose of this study was to determine the feasibility of high-resolution sonography for the detection of meniscal cysts and associated meniscal tears and for the differentiation of meniscal cysts from other masses at the knee joint. SUBJECTS AND METHODS: Fifty consecutive patients (51 knees) with a palpable mass at the knee joint were examined prospectively using a 7.5-MHz annular array transducer. Mass consistency and location and meniscal integrity were evaluated. Sonographic findings were correlated with surgery (46/51) and histopathology (15/51). Five patients did not undergo surgery. RESULTS: At surgery, 32 masses appeared to be meniscal cysts, whereas 19 were other types of masses. Sonographically, 31 of the 32 meniscal cysts were diagnosed correctly. Sonographic differentiation of the other types of masses from meniscal cysts could reliably be made in 17 of 19 cases; two masses were falsely interpreted as meniscal cysts. Sensitivity, specificity, and accuracy of sonography in the depiction of meniscal cysts were 97%, 86%, and 94%, respectively. The positive predictive value was 94% and the negative predictive value was 92%. Meniscal tears (31/46) and meniscal tears concomitant with meniscal cysts (26/32) were detected with an accuracy of 83% and 88%, respectively. CONCLUSION: Sonography is an accurate imaging technique for the detection of meniscal cysts and associated meniscal tears. Differentiation of meniscal cysts from other cystic and solid masses at the knee joint can be reliably made with sonography.     

Clivus chordoma

Chordomas are slow growing, locally invasive tumors that most commonly present as midline masses in the sacrococcygeal or clival regions. The case presented in this paper demonstrates the typical MRI appearance of a clival chordoma in a patient presenting with classic symptoms of cranial nerve compression and headache. While the exact signal characteristics of these lesions seen on MRI may vary with pathologic subtypes, MRI has proven essential in the diagnosis, surgical planning and post-treatment evaluation of patients with these lesions.     

Diagnostic imaging of benign and malignant liver tumors: computerized tomography or magnetic resonance tomography?

Diagnostic imaging, consisting of roentgenograms and magnetic resonance images (MRIs), was performed as part of an evaluation of the effects of a functional electrical stimulation (FES) program on the knee joints of 29 adolescents with spinal cord injuries following implantation of fine-wire intramuscular electrodes in their lower extremity muscles. The subjects underwent a regimen consisting of stimulated exercise, standing and/or walking. The effects of FES on knee joints were prospectively studied by reviewing diagnostic imaging data. Evaluation of MRIs and plain radiographs showed no evidence of knee joint pathology secondary to FES exercise or weight bearing. In fact, based on follow-up of MRI scan, many of the joints improved following participation in the program. The MRI data supported the clinical examination of the knee joints of these children. Clinical examination appears adequate for screening for potential knee joint problems.     

The patellar tilt angle: correlation of MRI evaluation with anterior knee pain

The purpose of this study was to analyze the degree of patella tilt and its correlation with the symptoms of anterior knee pain. We used magnetic resonance imaging (MRI) to measure the angle of patella tilt. The patients (n = 128) were classified into two groups. Group 1 (n = 78) included patients who had never had symptoms of anterior knee pain but had MRI for evaluation of the menisci and the ligaments. Group 2 (n = 50) included patients who had MRI for evaluation of anterior knee pain syndrome. Patients who had gross deformities like patellar dislocation, tricompartmental osteoarthritis, or inflammatory arthritis were excluded. The average patella tilt angle was 6.3 (SD = 3.9) and 12.8 (SD = 8.4) degrees, respectively, for the two groups of patients. Twenty-three patients in group 2 underwent arthroscopy because of failure of conservative treatment, and the average patella tilt angle in this subgroup was 16.4 degrees. Our study suggests that patella tilt angle is correlated with the symptoms of anterior knee pain, and indicated that the cause of pain came from the tight lateral retinaculum. In addition, MRI was found to be an accurate and reproducible method of measurement of the patellar tilt angle.     

Office arthroscopy: a diagnostic alternative

Twenty patients with enigmatic knee symptoms were selected for evaluation by both magnetic resonance imaging (MRI) and office arthroscopy. Office arthroscopy was performed in a standard examination room using a miniature (1.7 mm) fiberoptic arthroscope under local anesthesia. All MRI scans were performed on a state-of-the-art 1.5-T magnet unit, and included specialized cartilage sequences in 7 patients. In 14 patients, 26 areas showed articular cartilage changes by arthroscopy (grade 2-3). Only nine of these areas were detected by MRI (sensitivity 34.6%). There were five false-positive and four false-negative readings of meniscal tears by MRI as compared with office arthroscopy. These results improved when postoperative menisci were excluded. Only one of three anterior cruciate ligament (ACL) disruptions identified by MRI could be verified by arthroscopy. The one posterior cruciate ligament (PCL) disruption was confirmed by both techniques. MRI was superior to arthroscopy in identifying bone contusions, subchondral sclerosis, and medial cruciate ligament (MCL) sprains. Office arthroscopy is an accurate and cost-efficient alternative to MRI in diagnostic evaluation of knee pathology in patients with enigmatic symptomatology.     

Accuracy of direct signs of tears of the anterior cruciate ligament

OBJECTIVE: To evaluate the accuracy of direct magnetic resonance imaging (MRI) signs of tears of the anterior cruciate ligament. PATIENTS AND METHODS: Over the period April 1991 to February 1994, 92 consecutive MRI studies of the knee were obtained for which arthroscopic data were also available. The MRI studies were retrospectively evaluated for course, continuity, signal intensity, morphologic features, contour and visualization of the anterior cruciate ligament. Arthroscopic findings were correlated with individual primary signs and the overall MRI diagnosis. RESULTS: Among the cases studied were 4 partial and 32 complete tears of the anterior cruciate ligament (as determined by arthroscopy). Because of the low number of partial tears, it was not possible to draw any meaningful conclusions about the MRI diagnosis of this type of tear. For complete tears, the criteria with the highest accuracy were abnormal course of the ligament (96.0%) and high signal intensity (89.3%). The overall diagnostic accuracy of MRI was 98.8%. CONCLUSIONS: The most accurate direct MRI finding in patients with a complete tear of the anterior cruciate ligament was abnormal course of the ligament, followed by abnormally high signal intensity.     

Sharps disposal systems

As clinical MRI has evolved, there have been numerous arguments for the use of different field strengths. Those favoring high magnetic field (1.5 T and above) include higher signal-to-noise ratio, capability for MR spectroscopy, and other forms of functional MRI, high speed imaging, and high resolution imaging. However, cost remains a significant limitation to the wider dissemination of high field MRI. There are definite cost advantages (capital, operating, siting) to the use of lower field MRI. Much debate has occurred over the past decade regarding the relative diagnostic benefits of high field MRI versus lower field MRI, but few randomized, controlled clinical trials have compared diagnostic accuracy of MRI at various field strengths. In this article, we review the physical principles of the field strength dependence of MRI in relation to image quality. The assessment of the importance of field strength in MR is incomplete without some analysis of diagnostic accuracy versus field strength. Such analysis is difficult to accomplish in an unbiased manner. The use of receiver-operator-characteristic (ROC) analysis is probably the best available method to measure diagnostic accuracy of various imaging methods without bias. An ROC study of diagnostic accuracy of 0.5 T versus 1.5 T MRI, examining several common clinical categories, has recently been conducted at our institution. Results from this study demonstrate diagnostic equivalence between these two field strengths in at least two common clinical disease categories (MS and internal derangement of the knee). These results are discussed and related to results from previous field strength studies.     

The knee joint--imaging

In the assessment of knee joint abnormalities plain films must still be used today as primary imaging modality. For soft tissue, cartilage, tendon and ligament lesions, sonography, CT and MRI (with arthrography) is available today. Especially MRI leads to a significantly extended diagnosis.     

Chondrocalcinosis of the hyaline cartilage of the knee: MRI manifestations

PURPOSE: To determine the ability of MRI to detect the presence of crystals of calcium pyrophosphate in the articular cartilage of the knee. DESIGN AND PATIENTS: The MR studies of 12 knees (11 cases) were reviewed retrospectively and correlated with radiographs (12 cases) and the findings at arthroscopy (2 cases) and surgery (1 case). A total of 72 articular surfaces were evaluated. Radiographic, surgical or arthroscopic demonstration of chondrocalcinosis was used as the gold standard. Additionally, two fragments of the knee of a patient who underwent total knee replacement and demonstrated extensive chondrocalcinosis were studied with radiography and MRI using spin-echo T1-, T2- and proton-density-weighted images as well as two- and three-dimensional fat saturation (2D and 3D Fat Sat) gradient recalled echo (GRE) and STIR sequences. RESULTS: MRI revealed multiple hypointense foci within the articular cartilage in 34 articular surfaces, better shown on 2D and 3D GRE sequences. Radiographs showed 12 articular surfaces with chondrocalcinosis. In three cases with arthroscopic or surgical correlation, MRI demonstrated more diffuse involvement of the articular cartilage than did the radiographs. The 3D Fat Sat GRE sequences were the best for demonstrating articular calcification in vitro. In no case was meniscal calcification identified with MRI. Hyperintense halos around some of the calcifications were seen on the MR images. CONCLUSION: MRI can depict articular cartilage calcification as hypointense foci using GRE techniques. Differential diagnosis includes loose bodies, post-surgical changes, marginal osteophytes and hemosiderin deposition.     

The determination of INR in stored whole blood

Portal venous aneurysm is an unusual vascular abnormality. We present this entity with magnetic resonance imaging (MRI) findings showing characteristic flow abnormality in two patients. Ultrasound examination revealed hyperechoic lobulated masses in the portal vein and the duplex Doppler study confirmed the venous flow patterns of low resistance within the lesion. The literature regarding this entity and the potential role of MRI are briefly discussed.     

Intrasplenic masses of "preserved" functioning splenic tissue in sickle cell disease: correlation of imaging findings (CT, ultrasound, MRI, and nuclear scintigraphy)

PURPOSE: We studied six patients with sickle cell disease (SSD), five homozygous for sickle cell anemia and one with sickle beta-thalassemia, in whom rounded intrasplenic masses proved to be preserved functioning splenic tissue. MATERIALS AND METHODS: Available images including computed tomography, ultrasonography, bone scans (Tc-99m MDP), liver spleen scans (Tc-99m sulfur colloid), and MRI were evaluated. RESULTS: The masses were low density on CT (in an otherwise calcified spleen), hypoechoic relative to the echogenic spleen on US, and had the imaging characteristics of normal spleen on MRI. They failed to accumulate Tc-99m MDP but did demonstrate uptake of Tc-99m sulfur colloid. CONCLUSION: In a patient with SSD and intrasplenic masses, proper correlation of multiple imaging modalities will establish the diagnosis of functioning splenic tissue and avoid mistaken diagnosis of splenic abscess or infarction.