Magnetic resonance (MR) imaging of the chest: state-of-the-art

To date, magnetic resonance (MR) is established as an imaging modality in the diagnosis of chest diseases. Because of its excellent distinction of vessels and soft tissue, MR can be performed as the primary imaging procedure before computed tomography in patients with suspected vascular lesions, mediastinal masses, hilar lesions, and pathological changes of the pleura and the chest wall. In these cases, MR is able to provide all the necessary diagnostic information. In other patients, a limited number of MR images may be helpful in cases of equivocal or confusing CT or clinical findings. More detailed information can be obtained, using surface coils or special imaging sequences, i.e. high resolution MR images of the pleura or angiographic images of mediastinal and pulmonary vasculature. From a clinical viewpoint, the most important task for thoracic magnetic resonance nowadays is the pretherapeutic evaluation of intrathoracic masses, the differential diagnosis of benign versus malignant lesions, and the accurate documentation of tumour extent in malignancies including three-dimensional-display to improve surgical or radiation planning. Future directions in thoracic magnetic resonance will be predominantly influenced by postprocessing approaches, specialized imaging techniques, and magnetic resonance-guided interventional applications.     

Concurrent and predictive validity of an early language screening program

MR imaging has fulfilled many of the dreams of the pediatric radiologist studying the hip: it has allowed depiction of detailed anatomy, evaluation of vascularity and perfusion, determination of synovial proliferation activity in chronic arthritis, and detection of bone marrow changes with great sensitivity. MR imaging also has brought some disenchantments; it lacks specificity, it is expensive and long, and it often requires sedation. MR imaging is operator dependent and hardware and software dependent. Finally, issues of cost-effectiveness and clinical efficacy in comparison with good physical examination and conventional radiography or ultrasound remain unresolved. Demonstration of its cost-effectiveness in the clinical setting is clearly the dominant challenge facing MR imaging today.     

MR imaging of tibial plateau fractures

Magnetic resonance (MR) images of five patients with acute tibial plateau fractures are presented and correlated with both clinical examination and findings at surgical intervention. The role of MR imaging in the evaluation of both osseous and soft tissue deformity in acute trauma, specifically in patients with tibial plateau fractures is discussed. The value of MR imaging as an alternative to computed tomography and arthroscopic evaluation of these patients is emphasized.     

The ovary. Computed tomography and magnetic resonance imaging

CT and MR imaging can both contribute valuable clinical information in women with benign and malignant ovarian masses; the superior soft tissue contrast and multiplanar capabilities provided by MR imaging make it a valuable tool to evaluate the normal ovary, polycystic ovaries, endometriosis, and disorders of sexual differentiation. CT is currently the recommended modality to stage ovarian carcinoma, and peritoneal implants as small as 5 mm can be visualized. With the addition of contrast-enhanced images to conventional MR sequences, however, improved visualization of intratumoral architecture has also allowed for accurate MR characterization of benign versus malignant ovarian masses. Fat saturation techniques used with conventional MR sequences can also be used for definitive characterization of benign fat-containing teratomas and differentiate these tumors from hemorrhagic ovarian cysts or endometriomas. Finally, the detailed visualization of the normal-sized ovary on MR images provided by both the body coil and the new phased-array coil allows detection of the normal ovaries, ovarian follicles, and ovarian cysts throughout the premenopausal and postmenopausal years. Findings of polycystic ovarian syndrome, which cannot be evaluated by CT, are characteristic on MR images. MR is unparalleled in the evaluation of disorders of sexual differentiation because MR images can depict ectopic and normally positioned gonads and provide multiplanar depiction of the other pelvic organs and perineum as well. CT and MR imaging can provide valuable and specific clinical information about the ovary and benign and malignant ovarian disease.     

Magnetic resonance imaging of the musculoskeletal system. Part 6. The Shoulder

The role of magnetic resonance imaging in the diagnosis and treatment of patients with shoulder pain has increased remarkably in recent years, largely because of improved resolution of images and increased experience of musculoskeletal radiologists. In rotator cuff disease/impingement and instability, magnetic resonance imaging adds a new dimension to the clinical findings through the noninvasive visualization of either the pathology itself or frequently associated abnormalities. It is the associated abnormalities that are depicted in instability: glenoid irregularities, labral tears, capsular laxity, and Hill-Sachs deformities. Glenoid, labral, and Hill-Sachs abnormalities can be assessed with either magnetic resonance imaging or computed tomography arthrography. Magnetic resonance imaging has the advantages of noninvasiveness, multiplanar imaging capability and exquisite soft tissue contrast. In rotator cuff disease, magnetic resonance imaging depicts the status of the rotator cuff itself, revealing partial and full thickness tears, allowing an estimation of size and quality of tendon edges. Possible impingement sites can be identified. Primary instability with secondary impingement may be first suspected on magnetic resonance imaging. Postoperative complications, including recurrent tendon detachment, deltoid dehiscence, and infection, are clarified. Unsuspected but clinically important lesions, such as neoplasm, osteonecrosis, and ganglion with entrapment of the suprascapular nerve, each have characteristic magnetic resonance imaging appearances.     

Disorders of the hallux sesamoid complex: MR features

Numerous painful conditions can affect the first metatarsophalangeal-sesamoid joint complex. Symptoms can be of sudden or insidious onset, and be of acute or chronic duration. Although conventional radiography is recognized as the initial diagnostic procedure for these symptoms, there is often a need to proceed to MR imaging. MR imaging is sensitive and can be utilized in the investigation of the hallux sesamoid complex to differentiate soft tissue from osseous pathology. Synovitis, tendonitis, and bursitis can be distinguished from bony abnormalities such as sesamoid fracture, avascular necrosis, and osteomyelitis. An understanding of MR imaging features and techniques will result in the highest diagnostic yield. Early and accurate diagnosis of sesamoid complex disorders can guide the physician to the appropriate clinical management and prevent potentially harmful longstanding joint dysfunction.     

Staphylococcal enterotoxin-A directly stimulates signal transduction and interferon-gamma production in psoriatic T-cell lines

MRI has gained an undisputed place in the evaluation of malignant bone tumors, not only for verifying results of conventional radiographs and clarifying differential diagnoses; it has also become increasingly important for the assessment of the malignant/benign nature of the tumor, its growth rate, definition of adequate sites for biopsy, local preoperative staging, and evaluation of the response to chemotherapy. However, several pitfalls have to be observed regarding choice of technical parameters (coils, sequences, imaging planes), tissue differentiation, and tumor staging. When staging malignant tumors, critical aspects which have to be observed are tumor extension, integrity of the cortical bone, soft tissue components, infiltration of a joint or neurovascular bundle. The use of contrast agents provides important additional information but can also give rise to misinterpretations. Thus, all features of a tumor have to be observed in order to establish a final diagnosis. Particular difficulties can occur with the interpretation of MR images of osteomyelitis, osteoid osteoma, stress and insufficiency fractures, bone infarcts, myositis ossificans, hemangiomas, and aneurysmal bone cysts.     

MR imaging of the major nerves about the elbow: cadaveric study examining the effect of flexion and extension of the elbow and pronation and supination of the forearm

Magnetic resonance (MR) imaging provides useful information in the evaluation of peripheral nerves. Recent advances in MR imaging allow for detailed depiction of the soft tissue structures of the elbow joint. Three major nerves are present about the elbow. Six cadaveric elbows were imaged to depict the normal anatomy of these nerves and to determine the best plane and position of the elbow for optimal visualization of each nerve. Axial images of the elbow in full extension with the forearm in supination allow identification of all major nerves. Axial images with the elbow in full flexion allow accurate assessment of the cubital tunnel and the ulnar nerve. Axial images of the elbow in full extension with the forearm in pronation are helpful for assessment of the median and radial nerves in the forearm.     

Imaging features and clinical significance of perineural spread or extension of head and neck tumors

Perineural spread of head and neck tumors is a form of metastatic disease in which tumor disseminates to noncontiguous regions along the endoneurium or perineurium. Both computed tomography (CT) and magnetic resonance (MR) imaging can help detect perineural spread, although MR imaging is the modality of choice because of its multiplanar capability, its superior soft-tissue contrast, and the decreased amount of artifact from dental hardware. Perineural spread most commonly occurs in adenoid cystic carcinoma and squamous cell carcinoma. Nerve enlargement may lead to foraminal enlargement and, ultimately, to foraminal destruction, findings that are best seen at CT. Extension through the foramen ovale and involvement of the Meckel cave is best seen on coronal T1-weighted MR images, and nerve enhancement is best seen on fat-suppressed T1-weighted MR images. Other radiologic findings include obliteration of fat planes at foraminal openings, neuropathic atrophy, cavernous sinus enlargement, and replacement of the trigeminal subarachnoid cistern with soft tissue. The pathway of perineural tumor spread is predictable with knowledge of the pertinent cranial nerve anatomy; however, patients with radiologically or pathologically proved perineural spread may have normal nerve function at clinical examination. Therefore, it is imperative that the radiologist be familiar with both normal cranial nerve anatomy and the radiologic appearance and assessment of perineural tumor extension.     

Correlation between anatomic features and low-field magnetic resonance imaging of the equine metacarpophalangeal joint

OBJECTIVE: To expand our current knowledge and to establish limits of correlation between signal intensities of the magnetic resonance (MR) image and actual macroscopic and microscopic anatomic features of the imaged structures of the equine metacarpophalangeal joint (MCPJ). SAMPLE POPULATION: The right MCPJ was obtained from 4 adult horses that were euthanatized for reasons unrelated to the musculoskeletal system. PROCEDURE: The distal portion of the right forelimbs was collected from 4 equine cadavers. The bones were drilled to provide fixed reference points and examined by MR imaging. After imaging, the joints were sectioned for gross and histologic inspection. The MR images were aligned and correlated with digitized gross and histologic images to identify tissue types. RESULTS: Comparison of the images resulted in identification of different bone types, articular cartilage, and soft tissue structures of the equine MCPJ. CONCLUSION: Results provided relevant information regarding the appearance of the imaged tissues of the equine MCPJ. CLINICAL RELEVANCE: Although MR imaging does not have current clinical applications for equine practitioners, its wide acceptance as the imaging modality used for most human musculoskeletal derangements may aid in developing more realistic applications in equine medicine.     

Pretherapeutic staging of laryngeal carcinoma. Clinical findings, computed tomography, and magnetic resonance imaging compared with histopathology

BACKGROUND: An accurate pretherapeutic staging of laryngeal carcinoma is required for most treatment planning as well as for evaluation and comparison of the results of different treatment modalities. Neoplastic invasion of the laryngeal cartilage may have important therapeutic implications. To our knowledge, no data are available comparing the impact of endoscopic examination, computed tomography (CT), and magnetic resonance (MR) imaging on pretherapeutic staging accuracy. The purpose of our study was to determine which imaging should be used as an adjunct to other clinical examinations in the pretherapeutic staging of laryngeal carcinoma. METHODS: In this study, 40 consecutive patients with neoplasms of the larynx, who were treated surgically, were included in a prospective pretherapeutic staging protocol that included indirect laryngoscopy, direct microlaryngoscopy, contrast-enhanced CT, and gadolinium-diethylenetriamine pentaacetic acid-enhanced MR imaging at 1.5 Tesla. The surgical specimens were cut in whole-organ slices parallel to the plane of the axial CT and MR images. The histologic findings were compared with the clinical findings including the CT and MR images. The impact of each diagnostic method on pretherapeutic staging was analyzed. RESULTS: Clinical/endoscopic evaluation failed to correctly stage 17 tumors due to invasion of the paraglottic space (1 tumor), preepiglottic space (2 tumors), and extralaryngeal soft tissues (14 tumors), resulting in a pretherapeutic staging accuracy of 57.5%. Neoplastic invasion of cartilage was present in 28 patients and absent in 12 patients. Although MR imaging was more sensitive in detecting neoplastic invasion of cartilage than CT (94% vs. 67%; P = 0.001), MR imaging was less specific than CT (74% vs. 87%; P = 0.007). There was no difference between the overall accuracy of CT and MR imaging in detecting neoplastic invasion of cartilage (80% vs. 82%). The accuracy of combined clinical/endoscopic examination and CT staging was 80% and the accuracy of combined clinical/endoscopic examination and MR imaging staging was 87.5%; the difference was not statistically significant. CONCLUSIONS: Clinical/endoscopic examination alone failed to identify tumor invasion of the laryngeal cartilages and of the extralaryngeal soft tissues, resulting in a low staging accuracy (57.5%). Many pT4 (according to the International Union against Cancer TNM Staging System) tumors were clinically unrecognized. The combination of clinical/endoscopic evaluation and an additional radiologic examination, either CT or MR imaging, resulted in significantly improved staging accuracy (80% vs. 87.5%). MR imaging is significantly more sensitive but less specific than CT in detecting neoplastic cartilage invasion. Therefore, MR imaging tends to overestimate neoplastic cartilage invasion and may result in overtreatment, whereas CT tends to underestimate neoplastic cartilage invasion and may lead to inadequate therapy.     

New aspects on the composition, structure and origin of calcium oxalate monohydrate calculi

We recently reported that typical abnormalities of avascular necrosis (AVN) in magnetic resonance images (MRI) of the hips of asymptomatic renal transplant recipients whose plain radiographs are normal may improve spontaneously and even disappear completely. We present the results of serial bone scans, most of which were performed with single-photon emission computed tomography obtained over periods as long as 24 mo after transplantation in 72 of these patients. Three paired imaging studies (i.e., MR and bone scan performed within 30 days of each other) were available for each of these patients. In three patients, both the MR images and the bone scans showed changes consistent with bilateral AVN within 4 mo after transplantation. All three patients developed hip pain which was bilateral in two and unilateral in one. Two patients (three hips) required surgical intervention at which time AVN was found on pathologic examination of all three hips. None of the remaining 69 patients developed hip pain during the study. However, in nine patients whose MR studies were consistently normal, at least one bone scan was abnormal (13 hips). The presence of AVN was pathologically confirmed in each of the hips subjected to surgery. Where the imaging findings were identical to those in the asymptomatic patients as well as those in whom the imaging abnormality regressed, we suggest that the subclinical imaging abnormalities represent mild AVN, which is reversible in some cases. Since the process was identified in 10 hips by MRI and in 13 hips by bone scan, both studies are needed to detect subclinical AVN. This may be important if treatment of subclinical disease is clearly shown to prevent progression to symptomatic AVN.     

Knee problems--imaging techniques

Standard radiographs still represent the standard imaging method in knee abnormalities. Major advantages include high spatial resolution, low cost, high availability and standardized imaging technique. Because there is an increasing pressure on the cost of health care, additional imaging should only be employed based on a working hypothesis. In most cases MR imaging is most suitable for further diagnosis. In internal knee derangements MR imaging has been shown to have a high negative predictive value, thus obviating unnecessary surgery. MR imaging also is the imaging method of choice in the detection and follow-up of arthritis, in the detection, staging and follow-up of malignant neoplasms, and in the detection of occult fractures. Ultrasonography is useful in the characterization of superficial soft-tissue abnormalities, but has not gained high acceptance in searching for internal derangements of the knee. Scintigraphy is competing with MR imaging in the early detection of bone abnormalities and for follow-up. However, it is less expensive and can be employed for the evaluation of multilocular processes. CT has a limited role in the evaluation of complex fractures mainly of the tibial plateau.     

Amyloid arthropathy of the hip joint: MR demonstration of presumed amyloid lesions in 152 patients with long-term hemodialysis

The aim of this study was to determine the spectrum of MR findings of presumed amyloid arthropathy of the hip joints in patients on long-term hemodialysis. We prospectively performed T1- and T2-weighted spin-echo imaging on 152 consecutive patients on hemodialysis. The duration of hemodialysis ranged from 5 months to 24 years, 2 months (mean: 8 years, 8 months). The frequency, location, and signal intensity of bone lesions were assessed. In 12 cases with contrast-enhanced MR examination, enhancement pattern of bone lesions, synovial lesions, and intra-articular lesions were characterized. Bone lesions presumed to be amyloid deposits were identified in 60 patients (39%). Magnetic resonance imaging revealed that amyloid lesions were more extensive than anticipated by plain radiographs. All bone lesions showed decreased signal intensity on T1-weighted images. On T2-weighted images, bone lesions showed increased signal intensity in 32 patients (54%), decreased signal intensity in 11 patients (18%), and both increased and decreased signal intensity in 17 patients (28%). Following intravenous injection of gadolinium-based contrast, all bone lesions showed moderate enhancement. Synovial thickening could not be identified on T1- and T2-weighted images. However, contrast-enhanced images showed thickened synovial membrane, which could be differentiated from joint fluid. Intra-articular nodules showed decreased or intermediate signal intensity on T1-weighted images and decreased signal intensity on T2-weighted images; the intra-articular nodules were contiguous with subchondral bone lesions. Magnetic resonance imaging is useful for evaluating the distribution and extent of amyloidosis of the hip joints in patients undergoing long-term hemodialysis.     

Fluoroscopic MR of the pharynx in patients with obstructive sleep apnea

PURPOSE: The purpose of our study was to introduce an ultrafast MR imaging technique of the pharynx as a diagnostic tool for viewing the mechanism of obstruction in patients with obstructive sleep apnea. METHODS: Six healthy volunteers and 16 patients with obstructive sleep apnea were examined on a 1.5-T whole-body imager using a circular polarized head coil. Ultrafast two-dimensional fast low-angle shot sequences were obtained in midsagittal and axial projections during transnasal shallow respiration at rest, during simulation of snoring, and during performance of the Müller maneuver. All patients underwent physical examination, transnasal fiberoptic endoscopy, and polysomnography. RESULTS: Five to six images were obtained per second with an in-plane resolution of 2.67 x 1.8 mm and 2.68 x 2.34 mm, allowing visualization of motion of the tongue, soft palate, uvula, and posterior pharyngeal surface. MR findings correlated well with results of clinical examination. The length of obstruction in the oropharynx, which cannot be ascertained by transnasal endoscopy of the pharynx, was clearly visible MR images. Differences between patients with obstructive sleep apnea and healthy subjects in terms of the degree of obstruction in the velopharynx and oropharynx depicted on MR images during the Müller maneuver were highly significant. CONCLUSION: We believe that ultrafast MR imaging is a reliable noninvasive method for use in the evaluation of obstructive sleep apnea.     

Differential diagnosis of pediatric musculoskeletal masses

MR imaging plays a major role in the evaluation of children with soft tissue and bone tumors. While the imaging characteristics of these lesions are often nonspecific, MR imaging provides valuable information on the extent of disease and relationship of tumors to the neurovascular bundle and other vital structures. This article reviews the radiographic and MR imaging appearances and clinical presentations of a wide range of musculoskeletal masses that occur in children.     

Detection of Aeromonas hydrophila serogroup 0:34 in faeces using an enzyme-linked immunosorbent assay

The efficacy of gadopentetate dimeglumine (Gd-DTPA) enhanced magnetic resonance (MR) imaging in the diagnosis and differentiation of soft-tissue, neoplastic and non-neoplastic lesion has not been well established. Thirty patients with soft tissue masses (18 neoplastic and 12 non-neoplastic) were studied, using MR imaging with and without administration of Gd-DTPA. Gd-DTPA proved helpful in characterisation of several entities, including differentiation of solid mass from proteinaceous cyst, demonstration of tumour nodules within haemorrhagic or necrotic masses, and delineation of tumour adjacent to oedema. The use of Gd-DTPA may provide additional information for tissue specificity and, in complicated cases, Gd-DTPA may also provide essential information that cannot be obtained using other methods. We recommend the use of contrast enhanced MR as an adjunct to conventional MR imaging in the initial assessment of musculoskeletal soft tissue masses. However, T2-weighted images show better tissue contrast of the lesions, and are equal to contrast enhanced images in delineation of tumour margins. Non-contrast enhanced images are, therefore, probably adequate for the delineation of lesions for surgical planning when a diagnosis has already been made.     

Primary muscle lymphoma: clinical and imaging findings

PURPOSE: To assess the clinical and imaging findings in primary muscle lymphoma. MATERIALS AND METHODS: Seven patients with biopsy-proved primary muscle lymphoma without evidence of systemic disease underwent imaging with plain radiography or computed tomography (CT) and magnetic resonance (MR) imaging. Four underwent bone scintigraphy, and two underwent gallium scintigraphy and fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) before and after therapy. RESULTS: Plain radiographs at initial examination (n = 5) showed no bone abnormalities. Soft-tissue masses and bone marrow involvement showed isoattenuation at CT (n = 3), but at MR imaging (n = 7), all masses demonstrated increased signal intensity on T2-weighted images that involved multiple muscle compartments and typically spanned a long segment of the extremity. Adjacent bone disease was less extensive than muscle disease, and, in most cases, subcutaneous stranding or extension was observed adjacent to the masses. Good size correlation was observed between findings at MR imaging, gallium scintigraphy, and FDG PET. Two patients developed recurrent multifocal muscle lymphoma several years after initial examination. CONCLUSION: The presence of an extensive soft-tissue mass with infiltration of adjacent subcutaneous fat and minimal or no extension into the bone marrow cavity at MR imaging and normal plain radiographic findings may suggest primary muscle lymphoma.     

Gadolinium-enhanced MR imaging of pediatric patients after reduction of dysplastic hips: assessment of femoral head position, factors impeding reduction, and femoral head ischemia

OBJECTIVE: We describe gadolinium-enhanced MR imaging of position and vascular enhancement of the femoral head in pediatric patients who have undergone reduction of hip dislocation. SUBJECTS AND METHODS: Within 24 hr of hip reduction and spica casting, we performed 25 gadolinium-enhanced MR studies in 18 infants and young children (15 girls, three boys) with 23 dysplastic hips. All but two patients underwent closed reductions. We evaluated intraoperative arthrograms for obstacles to reduction and subsequent radiographs for avascular necrosis. RESULTS: MR images showed that all femoral heads were in their respective acetabula, but several structures interfered with concentric reduction. Obstacles to reduction included a pulvinar (n = 16), infolding of the capsule (n = 9), interposition of the labrum (n = 2), and a hypertrophied ligamentum teres and transverse ligament (n = 2). All 50 femoral heads showed enhancement: 35 normally, 10 homogeneously but less than on the contralateral femoral head or the ipsilateral greater trochanter, and five with areas of focally decreased enhancement. Hips that showed decreased enhancement had undergone greater degrees of abduction (r = .38, p < .01). CONCLUSION: Gadolinium-enhanced MR imaging can reveal abnormalities of hip position and proximal femoral epiphyseal and physeal vascularity that can occur after hip reduction. Abnormalities of enhancement were more frequent in patients who had greater femoral abduction. The effect of decreased epiphyseal vascular enhancement is still uncertain.     

Low-field magnetic resonance imaging (0.2 T) of tendons with sonographic and histologic correlation. Cadaveric study

RATIONALE AND OBJECTIVES: The authors evaluate the role of low-field strength magnetic resonance imaging (MRI) compared with sonography in the evaluation of degenerative changes of tendons, with histologic correlation, based on investigations of horse cadavers. METHODS: Low-field MRI and sonography was performed in 42 hours specimens for the evaluation of tendons and ligaments. Magnetic resonance imaging included sagittal and axial T1-weighted, T2-weighted, and gradient echo images. Sonography and MR images were evaluated for degenerative changes or tears and the findings were correlated with the histologic results. RESULTS: Using histologic findings as a gold standard, the accuracy for the sonographic evaluation was 65.9%, sensitivity was 16.7%, and specificity was 100%. The corresponding data for low-field MR imaging were 70.5% accuracy, 44.4% sensitivity, and 88.5% specificity. CONCLUSIONS: Low-field MRI investigation allows more accurate staging of tendinous changes than sonography. It is more reproducible and potentially includes the advantages of the combined evaluation of bones, ligaments, and soft tissue.