Evaluation of the rotator cuff and glenoid labrum using a 0.2-Tesla extremity magnetic resonance (MR) system: MR results compared to surgical findings.

The purpose of this investigation was to evaluate the diagnostic capabilities of magnetic resonance imaging (MRI) performed using a dedicated-extremity MR system in detecting lesions of the rotator cuff and glenoid labrum. This retrospective study compared the MR results obtained in 47 patients that underwent MRI using a 0.2-Tesla extremity MR system (E-scan) to the surgical findings. MR images of the shoulder were obtained as follows: shoulder coil, T1-weighted, coronal-oblique and axial images; short Tau inversion recovery (STIR), coronal-oblique images; and T2-weighted, coronal-oblique, sagittal-oblique, and axial images. The MR examinations were interpreted by three highly experienced, musculoskeletal radiologists. Open surgical (N = 26) or arthroscopic (N = 21) procedures were performed within a mean time of 33 days after MRI. The surgical findings revealed rotator cuff tears in 28 patients and labral lesions in 9 patients. For the rotator cuff tears, the sensitivity, specificity, positive predictive value, and negative predictive value were 89%, 100%, 100%, and 90%, respectively. For the labral lesions, the sensitivity, specificity, positive predictive value, and negative predictive value were 89%, 95%, 80%, and 97%, respectively. The findings indicated that there was good agreement comparing the MR results obtained using the low-field extremity MR system to the surgical findings for determination of lesions of the rotator cuff and glenoid labrum. Notably, the statistical values determined for the use of this MR system were comparable to those reported in the peer-reviewed literature for the use of whole-body, mid- and high-field-strength MR systems.

Kinematic magnetic resonance imaging of the effect of bracing on patellar position: qualitative assessment using an extremity magnetic resonance system.

OBJECTIVE: To use an extremity magnetic resonance system to perform kinematic magnetic resonance imaging (MRI) of the patellofemoral joint to qualitatively assess the effect of bracing on patellar position. DESIGN AND SETTING: Subjects underwent kinematic MRI of the symptomatic extremity with a 0.2-Tesla extremity magnetic resonance system. Images were obtained using a knee coil and a T1-weighted, spin echo pulse sequence. SUBJECTS: Seven female patients with patellofemoral joint symptoms. MEASUREMENTS: FOUR DIFFERENT AXIAL SECTIONS WERE OBTAINED FOR EACH POSITION: extension and 3 positions of flexion up to 36 degrees . An appropriate-sized patellofemoral brace was applied, and the kinematic MRI procedure was repeated. RESULTS: Six patients had lateral displacement of the patella, and 1 patient had medial displacement of the patella. After application of the brace, 6 patients (5 with lateral displacement and 1 with medial displacement, 86%) exhibited correction (5) or improvement (1 with lateral displacement) in the abnormal patellar positions, and 1 patient had worsening of the abnormal position of the patella. CONCLUSIONS: We used kinematic MRI to determine the presence of abnormal patellar positioning. Application of the brace counteracted the abnormal patellar positions in most of the patients studied.

Development and clinical application of kinematic MRI of the patellofemoral joint using an extremity MR system.

PURPOSE: Kinematic magnetic resonance imaging (MRI) of the patellofemoral joint provides diagnostic information pertaining to patellar alignment and tracking during the earliest increments of joint flexion, when abnormalities that affect this joint are the most apparent. Recently, a low-field strength (0.2 Tesla) dedicated extremity MR system has been designed, such that only the body part that is being imaged is placed inside of the magnet bore. The purpose of this investigation was to develop a kinematic MRI technique for the patellofemoral joint using the extremity MR system and to apply this procedure in the clinical setting. METHODS: An incremental, passive positioning kinematic MRI technique was developed for the patellofemoral joint that involved obtaining three different axial section locations with the patellofemoral joint extended and then imaging these same section locations repeatedly as the patellofemoral joint was flexed in four increments up to 36 degrees of flexion. MR images were obtained using a T1-weighted spin echo sequence. Five (10 PFJ) asymptomatic volunteers and nine patients (9 PFJ) with patellofemoral joint symptoms were studied. RESULTS: Volunteers had normal kinematic MRI examinations. Seven patients had lateral subluxation, and two patients had excessive lateral pressure syndrome. Two patients with lateral subluxation seen on their kinematic MRI studies had Merchant views (x-rays obtained at 45 degrees) that showed "normal" patellar alignment, illustrating the importance of imaging the patellofemoral joint at 30 degrees or less. CONCLUSIONS: A kinematic MRI technique was successfully developed for the low-field extremity MR system and utilized for clinical applications. This procedure may be used to determine the presence and severity of patellar malalignment and abnormal tracking patterns.

Cardiac pacemakers and implantable cardioverter defibrillators are unaffected by operation of an extremity MR imaging system.

OBJECTIVE: The objective of our investigation was to determine whether an MR imaging system designed to obtain images of the extremities affects the safety and functionality of pacemakers or that of implantable cardioverter defibrillators (ICDs). MATERIALS AND METHODS: Ex vivo experiments were conducted in which seven pacemakers and seven ICDs were exposed to a 0.2-T extremity MR imaging system. Magnetic field attraction was assessed at three positions relative to the MR imaging system. In addition, the devices were placed into a test apparatus that was oriented parallel and perpendicular relative to the MR imaging system while imaging was performed on a phantom using T1-weighted spin-echo and gradient-echo sequences. Various functional aspects of the pacemakers and ICDs were evaluated before, during (pacemakers only), and after MR imaging. RESULTS: Magnetic field attraction was relatively minor for all devices. The quality of the MR images was unaffected by the devices. Operation of this MR system did not alter any of the functional aspects of the pacemakers or ICDs evaluated in this study. CONCLUSION: According to these data and in consideration of how patients are positioned during examinations--that is, positioned so that the thorax (where the pacemaker or ICD and the corresponding leads are located) does not enter the magnet bore--the results suggest that it should be safe to perform MR imaging in patients with the pacemakers and ICDs evaluated in this study.

Aneurysm clips: assessment of magnetic field interaction associated with a 0.2-T extremity MR system.

Twenty-two different aneurysm clips were tested by means of the deflection angle test for magnetic field interaction associated with a 0.2-T extremity magnetic resonance (MR) system. At the opening of the magnet bore and 5 inches (13 cm) and 10 inches (25 cm) away from the magnet bore, respectively, deflection angles were 14 degrees, 2 degrees, and 0 degree for one clip and were 17 degrees, 4 degrees, and 0 degree for another, and were 0 degree for the remaining 20 clips. Because the patient's head does not enter the magnet bore, extremity MR imaging of patients with the aneurysm clips evaluated in this study should be safe.

Magnetic resonance imaging of hereditary hernias of the peroneus longus muscle.

Herniation of the left peroneus longus muscle was present in three male members of the same family, being the first reported case of this condition in a familial setting. The hernias were differentiated from other mass lesions and varices by magnetic resonance imaging. The images demonstrated a fascial defect originating in the area where vessels and nerves penetrate the fascia, suggesting that the three men had a congenital weakness in the fascia.

Musculotendinous injury.

Over the past decade, MR imaging has become one of the most valuable imaging tools for evaluation of musculoskeletal pathology. This is due to its high sensitivity to the vast majority of acute and chronic musculoskeletal injuries and the starting anatomic clarity provided. The latter feature allows definition of characteristic injury patterns, which is the key to most diagnoses and also usually allows accurate grading of the severity of injuries. Careful attention to imaging technique and the specific architectural patterns of musculotendinous disruption by the imaging specialist will result in accurate diagnoses for the patient and referring physician.

MR imaging in evaluation of suspected hip fracture: frequency of unsuspected bone and soft-tissue injury.

PURPOSE: To determine the frequency of unsuspected pelvic fracture and soft-tissue injury in patients referred for magnetic resonance (MR) imaging for possible radiographically occult hip fracture. MATERIALS AND METHODS: Seventy patients with symptoms of possible hip fracture but negative plain radiographs were evaluated with MR imaging. Large-field-of-view T1-weighted coronal images were obtained, and additional T2-weighted or short inversion time inversion recovery (STIR) sequences were used. The number of soft-tissue and bone injuries identified was recorded. RESULTS: Eighty percent of patients had bone or soft-tissue abnormalities. Occult femoral and pelvic fractures were demonstrated in 37% and 23% of patients, respectively. Soft-tissue abnormalities were noted in 74% of patients. When a proximal femoral fracture was not present, MR imaging revealed a 27% frequency of occult pelvic fracture and a 50% frequency of bone or soft-tissue abnormality. CONCLUSION: A high prevalence of occult pelvic fracture and soft-tissue injury may be identified with MR studies designed to evaluate occult hip fracture when large-field-of-view T1-weighted coronal sequences are combined with T2-weighted or STIR sequences.

MRI appearance of meniscal cysts.

PURPOSE: The purpose of this study was to review the MRI criteria for the distinction of meniscal cysts from other cystic lesions in the knee so that appropriate treatment may be planned. DESIGN: A retrospective review of 62 knee MRI scans possibly showing meniscal cysts was performed. The type of meniscal tear, the appearance of the connection between the cyst and the meniscal tear, and the location, size, morphology, and signal characteristics of the meniscal cysts were recorded. Other types of fluid collections that had been mistaken for meniscal cysts were described. PATIENTS: Sixty-two patients were studied, ages 16-79 years, 61% male, 39% female. RESULTS AND CONCLUSIONS: Most of the meniscal cysts (91%) occurred immediately adjacent to the meniscal tear (98% horizontal cleavage tears, 49% anterolateral), with the tear leading directly into the cysts. In two cases, the cyst had dissected into the soft tissues distant from the meniscus and a connecting stalk was visualized. Fluid collections in normal bursae and recesses that had been mistaken for meniscal cysts had no direct connection to a meniscal tear. MRI can be used to distinguish meniscal cysts from other fluid collections that may mimic meniscal cysts. Pitfalls can be avoided by familiarity with the normal bursal and capsular anatomy, and by the application of specific diagnostic criteria.

Meniscal ossicle: radiographic and MR imaging findings.

PURPOSE: To determine the magnetic resonance (MR) imaging appearance of meniscal ossicles and correlate that with the radiographic and clinical features. MATERIALS AND METHODS: Radiographs and MR images were studied retrospectively in six patients with meniscal ossicles; all patients had intermittent discomfort in the knee, and five patients had experienced knee trauma. Imaging findings were correlated with the clinical history. Four patients underwent arthroscopy. RESULTS: All patients had a visible ossicle on conventional radiographs initially interpreted as a loose joint body. MR imaging features included a corticated marrow-containing structure within the substance of the medial meniscus near the tibial attachment that appeared as a rounded focus of increased signal intensity on T1-weighted images that decreased in signal intensity on T2-weighted images. CONCLUSION: Meniscal ossicles have a characteristic MR appearance that may help distinguish them from loose bodies. They should be considered diagnostically when a circumscribed ossification is identified near the posterior horn of the medial meniscus on radiographs.

Atrial emptying with orthotopic heart transplantation using bicaval and pulmonary venous anastomoses: a magnetic resonance imaging study.

OBJECTIVES: We hypothesized that orthotopic heart transplantation with bicaval and pulmonary venous anastomoses preserves atrial contractility. BACKGROUND: The standard biatrial anastomotic technique of orthotopic heart transplantation causes impaired function and enlargement of the atria. Cine magnetic resonance imaging (MRI) allows assessment of atrial size and function. METHODS: We studied 16 patients who had undergone bicaval (n = 8) or biatrial (n = 8) orthotopic heart transplantation without evidence of rejection and a control group of 6 healthy volunteers. For all three groups, cine MRI was performed by combining coronal and axial gated spin echo and gradient echo cine sequences. Intracardiac volumes were calculated with the Simpson rule. Atrial emptying fraction was defined as the difference between atrial diastolic and systolic volumes, divided by atrial diastolic volume, expressed in percent. All patients had right heart catheterization. RESULTS: Right atrial emptying fraction was significantly higher in the bicaval (mean [+/- SD] 37 +/- 9%) than in the biatrial group (22 +/- 11%, p < 0.05) and similar to that in the control group (48 +/- 4%). Left atrial emptying fraction was significantly higher in the bicaval (30 +/- 5%) than in the biatrial group (15 +/- 4%, p < 0.05) and significantly lower in both transplant groups than in the control group (47 +/- 5%, p < 0.05). The left atrium was larger in the biatrial than in the control group (p < 0.05). Cardiac index, stroke index, heart rate and blood pressure were similar in the transplant groups. CONCLUSIONS: Left and right atrial emptying fractions are significantly depressed with the biatrial technique and markedly improved with the bicaval technique of orthotopic heart transplantation. The beneficial effects of the latter technique on atrial function could improve allograft exercise performance.

The impact of MRI on our understanding of the pathology of sports injuries.

NMR imaging has become an important diagnostic tool in the evaluation of musculoskeletal disease. However, its ability to evaluate pathogenic mechanisms of disease may eventually have even a greater impact on patient care. NMR imaging has significantly affected our understanding of the clinical significance of meniscal tears and appropriate patient management. It has also extended our understanding of the prevalence and importance of x-ray and arthroscopically occult bone, tendon and ligament injuries. By knowing the pathogenic mechanisms of disease, we can more reliably diagnose and treat pathology. In particular, many horizontal degenerative tears in older patients may be asymptomatic and are best left in place. Many acute tears may be best treated with immediate meniscal repair. MR imaging can reliably different these tear types with non-invasive imaging. MR's ability to detect bone injuries may lead to aggressive early non-weightbearing on injured bone, thereby preserving the subchondral bone from collapse and the joint from secondary osteoarthrosis. MRI's ability to detect and stage degenerative tendonosis of tendons and ligaments, such as the rotator cuff, may lead to arthroscopic decompression or debridement which provides symptomatic relief and may preserve and protect the intact cuff.

Posterosuperior glenoid impingement of the shoulder: findings at MR imaging and MR arthrography with arthroscopic correlation.

PURPOSE: To determine the utility of magnetic resonance (MR) imaging and MR arthrography in the evaluation of arthroscopic findings of posterosuperior glenoid impingement. MATERIALS AND METHODS: The findings at MR imaging, MR arthrography, and physical examination with the patient under anesthesia were retrospectively reviewed in eight patients with arthroscopic evidence of posterosuperior glenoid impingement. RESULTS: All patients had shoulder pain; anterior instability was found in six patients. Other than bone marrow abnormalities, findings at MR imaging were not reliable for the detection of posterosuperior glenoid impingement. MR arthrography was superior to routine MR imaging in all four cases in which it was done; positioning the shoulder in abduction and external rotation was beneficial in three of four patients. CONCLUSION: Impingement of the rotator cuff on the posterior superior glenoid labrum is a cause of posterior shoulder pain in athletes who throw. MR arthrography may allow detection of abnormalities associated with this clinical entity.

Musculoskeletal infection: findings on magnetic resonance imaging.

Magnetic resonance imaging (MRI) can provide considerable useful information in cases of musculoskeletal infection, in particular demonstrating the extent of involvement of soft tissues and medullary bone. Differentiation between infected tissue and abscess is also possible with MRI, especially if contrast agent is administered. MRI therefore serves as an adjunct to other imaging modalities, especially in complex cases. This review covers various manifestations of musculoskeletal infection as depicted with MRI.