Acromioclavicular joint osteoarthritis: comparison of findings derived from MR imaging and conventional radiography

The purpose of this study was to determine the correlation between routine radiography and magnetic resonance (MR) imaging in the analysis of the acromioclavicular (AC) joint osteoarthritis (OA). MR imaging studies of the shoulder in 50 patients performed over a 1-year period at a single institution with corresponding conventional radiographic examinations performed within 1 month of the MR imaging study were restrospectively evaluated by the consensus of two musculoskeletal radiologists with special attention to the AC joint. As conclusion, information provided by conventional radiography in the analysis of AC joint OA does not correlate with that provided by MR imaging. AC joint OA is more frequently detected with MR imaging than with radiography. MR imaging provides better assessment of the full extent of AC joint OA and its effect on the underlying RC.     

Pisotriquetral joint: assessment with MR imaging and MR arthrography

PURPOSE: To evaluate magnetic resonance (MR) imaging and MR arthrographic findings in the pisotriquetral joint (PTJ) and their contribution to assessment of PTJ osteoarthritis. MATERIALS AND METHODS: Images of 22 fresh human cadaveric PTJs were obtained with both conventional and arthrographic MR techniques. The MR appearances of all intraarticular and periarticular structures were analyzed and correlated with anatomic slices. Two readers graded visibility of anatomic structures and severity of joint abnormalities. Differences in the visibility ratings at standard MR imaging and at MR arthrography were calculated. Association between the type of pisiform insertion of ligament or muscle with cartilaginous abnormalities of the PTJ was assessed. The association between cartilaginous lesions and osteoarthritic changes was calculated. RESULTS: The tendon sheath, the fibrous capsule, and cartilaginous surfaces were better visualized at MR arthrography than at MR imaging. Pisohamate and pisometacarpal ligaments were slightly better seen on MR arthrograms. Tendons, muscles, and retinacular structures were well demonstrated at both conventional MR and MR arthrography. Cartilaginous lesions and osteophytes were easily identified and were detected more often in the pisiform bone than in the triquetral bone. Communication of the PTJ with the radiocarpal joint was noted in 18 (82%) of 22 wrists. CONCLUSION: MR imaging and/or MR arthrography allows visualization of all anatomic structures of the PTJ. MR arthrography improves visualization of findings of osteoarthritis.     

Optimizing joint imaging: MR imaging techniques

For optimizing MR of the joints, a sophisticated knowledge of MR system hard-and software condition, and coil technologies, sequence and contrast preparation techniques, and the use of paramagnetic contrast agents is necessary. This review article discusses the basic principles of the appropriate use of surfacecoilsas well as the different conventional and fast imagingsequences, including three-dimensional (3D)MR imaging. In addition, the applications of contrast agents as well as the most important contrast prepaation techniques are reviewed.     

Cerebrospinal fluid shunts: flow measurements with MR imaging

The authors describe a technique for determination of shunt patency by quantifying cerebrospinal fluid shunt flow rates with magnetic resonance (MR) imaging. This method uses a modified clinical sequence that is both sensitive to slow flow perpendicular to the imaging plane and capable of achieving oblique angles with a 4-cm field of view. Velocity-dependent phase images were used to quantify flow rates within the shunt. A preliminary study was performed in seven patients with hydrocephalus and cerebrospinal fluid shunts. Two patients were found to have zero flow in the shunt, while the remaining five had flow rates ranging from 4 to 19 mL/h. Results showed that the measurement of flow rates within the shunt lumen with MR imaging is clinically feasible.     

MR imaging of joint arthroplasty

Imaging evaluation of the painful total joint arthroplasty has, in the past, been limited to conventional radiographs, arthrography, and nuclear scintigraphy. All three modalities provide some clinical information regarding the status of the prosthesis, adjacent bone, and surrounding soft tissues but are hampered by poor specificity, particularly nuclear scintigraphy. Magnetic resonance imaging, using optimized pulse sequences to reduce the susceptibility artifact generated by the arthroplasty, can provide clinically relevant information regarding the prosthesis as well as the surrounding bone, soft tissues, and neurovascular structures.     

Failed temporomandibular joint prostheses: MR imaging

Magnetic resonance (MR) imaging with surface coils was performed on 43 temporomandibular joints with disk prostheses in 28 patients who had pain, dysfunction, or both after implantation of the prostheses. Fracture was diagnosed prospectively as a discontinuity of the prosthesis on the MR examination; the sensitivity and specificity of MR imaging for this diagnosis was determined on the basis of these studies. All patients underwent surgery, after which the final diagnosis was made. MR imaging was found to have a sensitivity of 0.81 and a specificity of 0.91. Other MR findings included an abnormal amount of soft tissue surrounding the disk, thinning of the disk, osteophytes, and erosion of the condyle. An as yet unexplained artifact was frequently seen and obscured the prostheses in four of the six false-negative studies. The one false-positive case resulted from the interpretation of a markedly thinned but intact region of the prosthesis as a fracture.     

Muscle edema in musculoskeletal tumors: MR imaging characteristics and clinical significance.

To determine the frequency and clinical significance of tumor-associated muscle edema, magnetic resonance (MR) imaging findings in 46 consecutive patients with benign or malignant musculoskeletal lesions were reviewed. Increased muscle signal intensity on T2-weighted, STIR (short-inversion-time inversion-recovery), and gadopentetate dimeglumine-enhanced T1-weighted images was present in 41 cases, with the clearest delineation of tumor margins seen on T2-weighted images. Typical peri/paratumoral edema (PTE) was present in equal proportions of malignant (25 of 37) and benign lesions (six of nine). Massive edema involving the entirety of at least one contiguous muscle--to the authors' knowledge, a previously undescribed finding--was identified on MR images of eight malignant and two benign lesions (22% of both groups). All cases of massive edema had a substantial soft-tissue component and involved muscles disrupted by tumor at the point of attachment to bone. Malignant tumors associated with massive edema were larger than those with typical or no PTE, showed a poorer response to initial chemotherapy, and had a higher frequency of metastases at diagnosis. Thus, the presence of massive muscle edema appears to be an ominous clinical finding in patients with malignant musculoskeletal lesions.     

Normal and abnormal temporomandibular joint: MR imaging with surface coil

The normal temporomandibular joint (TMJ) was evaluated using magnetic resonance (MR) imaging with a surface coil in five subjects and compared with the abnormal joint in 37 patients (aged 14-59 years; total joints studied, 76). Multisection 3-mm-thick sagittal, coronal, and axial images were obtained with a 1.5-T MR system and 6.5-cm-diameter surface coil using both partial saturation and spin-echo sequences (TR = 1,000 msec, TE = 20 or 25 msec). A comparison with arthrography (n = 13 joints), computed tomography (CT) (n = 11), and surgical (n = 5) findings demonstrated that MR imaging with a surface coil provided an accurate depiction of both normal and abnormal TMJs. MR provided information about meniscal position, morphology, and histology that was not available with either arthrography or CT alone. The imaging potential of MR and its noninvasive characteristics warrant priority for further examination of MR as a useful modality in the diagnosis of TMJ pain and dysfunction.     

Brain in eclampsia: MR imaging with clinical correlation

Cranial magnetic resonance (MR) imaging was performed on eight consecutive patients with generalized tonic-clonic seizures caused by eclampsia. Each patient underwent serial neurologic examinations until all symptoms resolved. Six of those eight patients underwent follow-up MR imaging. These patients were compared with those in previous case reports of MR imaging abnormalities of the brain in eclampsia. MR imaging typically demonstrates bilateral hyperintense lesions on T2-weighted images and iso- to hypointense lesions on T1-weighted images. MR imaging abnormalities are most commonly located in the distribution of the posterior cerebral circulation and are associated with visual disturbances. Basal ganglia and deep white matter lesions are less common and are associated with mental status changes. Most lesions seen at MR imaging in patients with eclampsia are reversible.     

MR imaging of meniscal cysts: incidence, location, and clinical significance.

OBJECTIVE: The purpose of this study was to determine the incidence of medial versus lateral meniscal cysts as seen on MR imaging. MATERIALS AND METHODS: A total of 2572 knee MR imaging reports were retrospectively reviewed for the presence of meniscal tears and cysts. Two musculoskeletal radiologists reviewed all images with reported cysts. The type and location of meniscal tear and the presence and location of meniscal cysts were recorded. RESULTS: A total of 1402 meniscal tears were reported in 2572 MR examinations (922 [66%] of 1402 in the medial compartment; 480 [34%] of 1402 in the lateral compartment). Meniscal cysts were present in 109 (4%) of 2572 knees. Of the 109 cysts, 72 (66%) were in the medial compartment, and 37 (34%) were in the lateral compartment. Meniscal cysts were found in association with 72 (7.8%) of the 922 medial meniscal tears and 37 (7.7%) of the 480 lateral meniscal tears. Meniscal cysts showed direct contact with an adjacent meniscal tear in 107 (98%) of 109 cases, with the tear showing a horizontal component in 96 (90%) of 107 cases. CONCLUSION: Meniscal cysts occur almost twice as often in the medial compartment as in the lateral compartment. Medial and lateral tears occur with the same frequency. These findings, when viewed in the context of the historical literature on meniscal cysts, suggest that MR imaging detects a greater number of medial meniscal cysts than physical examination or arthroscopy, and that MR imaging can have an important impact on surgical treatment of patients.     

MR imaging of intracranial fluid levels

Six patients with seven intracranial fluid levels were evaluated with both CT and MR at 1.5 T. A surgical diagnosis was obtained in six of the seven instances. MR was found to be superior to CT in detecting intracranial fluid levels, and the MR signal characteristics were helpful in identifying their contents. These cases demonstrate the necessity for a slightly different approach to lesions with fluid levels. In one patient, imaging in the prone position allowed detection of a solid component; in several others, detection of the fluid level was dependent on the selection of nonroutine windows and levels. Fluid levels are classified with respect to their components and MR features. MR is superior to CT in imaging fluid levels. The appearance of fluid levels on MR varies with their composition, the ratio of the components, the sequence parameters, and the position of the patient.     

MR imaging of body fluid collections

To evaluate the potential of magnetic resonance (MR) to characterize body fluids in vivo, we determined the relaxation times and the relative MR signal intensities of 42 body fluid collections in 42 patients. Twelve normal volunteers served as controls. We also studied albumin solutions at different concentrations and blood at various periods in vitro. Because of their long T1 relaxation times, most nonhemorrhagic fluid collections had low to intermediate intensity on images obtained with short repetition time (TR) and short echo time (TE) settings. Although the relaxation times and relative MR signal intensities of noninfected collections differed from those of infected collections, the values overlapped. On images obtained with short TR and short TE, blood in acute hemorrhages had intermediate signal intensity and serum in subacute hemorrhagic collections was the only pathologic fluid producing high signal intensity. Because of their relatively long T2 values, all the fluid collections were intense on images obtained with long TR and long TE settings; consequently, differences in intensity were less evident than on images obtained with short TR and short TE settings. Magnetic resonance allows reliable discrimination of subacute hemorrhagic collections from collections of other types, but the differentiation between acute hemorrhagic collections; nonhemorrhagic, noninfected collections; and nonhemorrhagic, infected collections is less accurate.     

Phenylketonuria: MR imaging of the brain with clinical correlation

Fifteen patients with biochemically documented phenylketonuria (PKU) were studied with use of magnetic resonance (MR) imaging with spin-echo T2-weighted pulse sequences. The resulting images demonstrated varying degrees of symmetric high signal intensity of the white matter within the posterior cerebral hemispheres. Involvement of the anterior hemispheres was seen only in cases with severe signal intensity changes. There was no involvement of the cerebral cortex, brain stem, or cerebellum. Moreover, no anatomic structural abnormalities were observed. Mild cortical atrophy was observed in eight of the 15 patients. There was no significant correlation between the patients' IQ scores and the level of MR signal intensity changes. Although MR imaging routinely shows relatively distinct abnormalities in patients with PKU, the clinical severity of the disease does not parallel its imaging severity.     

Acromioclavicular joint injuries and reconstructions: a review of expected imaging findings and potential complications

Shoulder injuries, including acromioclavicular (AC) joint separations, remain a common reason for presentation to the emergency room. Although the diagnosis can be made apparent through proper history and physical examination by the emergency medicine physician, ascertaining the degree of injury can be difficult on the basis of clinical evaluation alone. While there is consensus in the literature that low-grade AC joint injuries can be treated with conservative management, high-grade injuries will generally require surgical intervention. Furthermore, the treatment of grade 3 injuries remains controversial, making it incumbent upon the radiologist to become comfortable with distinguishing this diagnosis from lower or higher grade injuries. Imaging of AC joint injuries after clinical evaluation is generally initiated in the emergency room setting with plain film radiography; however, on occasion, an alternative modality may be presented to the emergency room radiologist for interpretation. As such, it remains important to be familiar with the appearance of AC joint separations on a variety of modalities. Another possible patient presentation in both the emergent and nonemergent setting includes new onset of pain or instability in the postsurgical shoulder. In this scenario, the onus is often placed on the radiologist to determine whether the pain or instability represents the sequelae of reinjury versus a complication of surgery. The purpose of this review is to present an anatomically based discussion of imaging findings associated with AC joint separations as seen on multiple modalities, as well as to describe and elucidate a variety of potential complications which may present to the emergency room radiologist.     

Moving knee joint: technique for kinematic MR imaging

A system for magnetic resonance imaging of the knee joint during movement was developed by using a gating system and cine acquisition. The technique was used in 10 subjects: five with no history of knee pain or injury and five with tears of the anterior cruciate ligament. The normal ligaments and menisci appeared as low-intensity structures against intermediate-intensity hyaline cartilage. The ligament tears appeared discontinuous and faint against the background of the to-and-fro moving joint fluid.