Case studies in the diagnosis of upper extremity pain using magnetic resonance imaging.

The diagnosis of upper extremity pain can be a daunting task for the examining physician. The differential diagnosis for pain at each level in the upper extremity is often extensive and diverse. Quite frequently, the clinical signs and symptoms of multiple pathologic conditions are overlapping and nonspecific. The decision to treat conservatively or with surgery often depends on the magnetic resonance imaging (MRI) findings. MRI's ability to produce multiplanar images with excellent soft tissue contrast has made it an indispensable tool for diagnosis and treatment planning in patients with upper extremity pain. In most instances, MR imaging provides information that all other modalities cannot. This is all possible due to an incredible imaging device that creates magnificent images painlessly and with no known detrimental biological side effects. This article demonstrates only a small number of the possible causes of upper extremity pain that can be diagnosed with MR imaging. It is comforting to know that the vast majority of pathology causing pain in the upper extremity can be visualized with MRI scanning.     

Task-related signal decrease on functional magnetic resonance imaging.

An atypical pattern of signal change was identified on functional magnetic resonance (fMR) imaging in pathologic patients. Three normal volunteers and 34 patients with pathologic lesions near the primary motor cortex underwent fMR imaging with echo-planar imaging while performing a hand motor task. Signal intensities were evaluated with the z-score method, and the time course and changes of the signal intensity were calculated. Nine of the 34 patients with pathologic lesions displayed a significant task-related signal reduction in motor-related areas. They also presented a conventional task-related signal increase in other motor-related areas. The time courses of the increase and decrease were the inverse of each other. There was no significant difference between rates of signal increase and decrease. Our findings suggest that this atypical signal decrease is clinically significant, and that impaired vascular reactivity and altered oxygen metabolism could contribute to the task-related signal reduction. Brain areas showing such task-related signal decrease should be preserved at surgery.     

Clinical hypnosis modulates functional magnetic resonance imaging signal intensities and pain perception in a thermal stimulation paradigm

OBJECTIVE: This study was designed to describe regional changes in blood oxygenation level dependent signals in functional magnetic resonance images (fMRI) elicited by thermal pain in hypnotized subjects. These signals approximately identify the neural correlates of the applied stimulation to identify neuroanatomic structures involved in the putative effects of clinical hypnosis on pain perception. METHODS: After determination of the heat pain threshold of 12 healthy volunteers, fMRI scans were performed at 1.5 Tesla by using echoplanar imaging technique during repeated painful heat stimuli. Activation of brain regions in response to thermal pain during hypnosis (using a fixation and command technique of hypnosis) was compared with responses without hypnosis. RESULTS: With hypnosis, less activation in the primary sensory cortex, the middle cingulate gyrus, precuneus, and the visual cortex was found. An increased activation was seen in the anterior basal ganglia and the left anterior cingulate cortex. There was no difference in activation within the right anterior cingulate gyrus in our fMRI studies. No activation was seen within the brainstem and thalamus under either condition. CONCLUSION: Our observations indicate that clinical hypnosis may prevent nociceptive inputs from reaching the higher cortical structures responsible for pain perception. Whether the effects of hypnosis can be explained by increased activation of the left anterior cingulate cortex and the basal ganglia as part of a possible inhibitory pathway on pain perception remains speculative given the limitations of our study design.     

Lateral hip pain: findings from magnetic resonance imaging and clinical examination

STUDY DESIGN: Prospective cross-sectional study. OBJECTIVES: To examine the radiological and physical therapy diagnoses of lateral hip pain (LHP), and determine the validity of selected clinical variables for predicting gluteal tendon pathology. BACKGROUND: LHP is frequently encountered by clinicians. Further investigation is required to establish the specific pathologies implicated in the cause of LHP, and which clinical tests are useful in the assessment of this problem. METHODS AND MEASURES: Forty patients with unilateral LHP underwent a physical therapy examination followed by magnetic resonance imaging (MRI) studies. Three radiologists analyzed the images of both hips for signs of pathology. Interobserver reliability of the image analyses, the agreement between the physical therapy and radiological diagnoses, and the validity of the clinical tests were examined. RESULTS: Gluteus medius tendon pathology, bursitis, osteoarthritis and gluteal muscle atrophy (predominantly affecting gluteus minimus) were all implicated in the imaging report of LHP. While prevalent in symptomatic hips, abnormalities were also identified in asymptomatic hips, particularly relating to the diagnosis of bursitis. The strength of agreement between radiologists was variable and little agreement existed between the physical therapy and radiological diagnoses of pathology. Nine of the 26 clinical variables examined in relation to gluteal tendon pathology had likelihood ratios above 2.0 or below 0.5, but the associated 95% confidence intervals were large. CONCLUSIONS: The diagnosis of LHP is challenging and our results highlight some problems associated with the use of MRI as a diagnostic reference standard. This factor, together with the imprecise point estimates of the likelihood ratios, means that no firm conclusions can be made regarding the diagnostic utility of the clinical tests used in the assessment of gluteal tendon pathology.     

Functional magnetic resonance imaging in a low-field intraoperative scanner

BACKGROUND: Functional magnetic resonance imaging (fMRI) has been used for preoperative planning and intraoperative surgical navigation. However, most experience to date has been with preoperative images acquired on high-field echoplanar MRI units. We explored the feasibility of acquiring fMRI of the motor cortex with a dedicated low-field intraoperative MRI (iMRI). METHODS: Five healthy volunteers were scanned with the 0.12-tesla PoleStar N-10 iMRI (Odin Medical Technologies, Israel). A finger-tapping motor paradigm was performed with sequential scans, acquired alternately at rest and during activity. In addition, scans were obtained during breath holding alternating with normal breathing. The same paradigms were repeated using a 3-tesla MRI (Siemens Corp., Allandale, N.J., USA). Statistical analysis was performed offline using cross-correlation and cluster techniques. Data were resampled using the 'jackknife' process. The location, number of activated voxels and degrees of statistical significance between the two scanners were compared. RESULTS: With both the 0.12- and 3-tesla imagers, motor cortex activation was seen in all subjects to a significance of p < 0.02 or greater. No clustered pixels were seen outside the sensorimotor cortex. The resampled correlation coefficients were normally distributed, with a mean of 0.56 for both the 0.12- and 3-tesla scanners (standard deviations 0.11 and 0.08, respectively). The breath holding paradigm confirmed that the expected diffuse activation was seen on 0.12- and 3-tesla scans. CONCLUSIONS: Accurate fMRI with a low-field iMRI is feasible. Such data could be acquired immediately before or even during surgery. This would increase the utility of iMRI and allow for updated intraoperative functional imaging, free of the limitations of brain shift.     

Iatrogenic hyperthermia during cardiac magnetic resonance imaging

We report the occurrence of accidental hyperthermia in a young child undergoing anesthesia for cardiac magnetic resonance imaging. Although the tendency during anesthesia is to develop hypothermia, the absorbed radiofrequency energy from magnetic resonance scanning is added to metabolic energy and must be balanced by appropriate heat loss to maintain normothermia. In addition to stressing the clinical importance of temperature monitoring, this report suggests that the recommended specific absorption rates to prevent excessive patient heating may need to be revised for infants and young children.     

Intraoperative magnetic resonance imaging during transsphenoidal surgery

OBJECT: The aim of this study was to evaluate whether intraoperative magnetic resonance (MR) imaging can increase the efficacy of transsphenoidal microsurgery, primarily in non-hormone-secreting intra- and suprasellar pituitary macroadenomas. METHODS: Intraoperative imaging was performed using a 0.2-tesla MR imager, which was located in a specially designed operating room. The patient was placed supine on the sliding table of the MR imager, with the head placed near the 5-gauss line. A standard flexible coil was placed around the patient's forehead. Microsurgery was performed using MR-compatible instruments. Image acquisition was started after the sliding table had been moved into the center of the magnet. Coronal and sagittal T1-weighted images each required over 8 minutes to acquire, and T2-weighted images were obtained optionally. To assess the reliability of intraoperative evaluation of tumor resection, the intraoperative findings were compared with those on conventional postoperative 1.5-tesla MR images, which were obtained 2 to 3 months after surgery. Among 44 patients with large intra- and suprasellar pituitary adenomas that were mainly hormonally inactive, intraoperative MR imaging allowed an ultra-early evaluation of tumor resection in 73% of cases; such an evaluation is normally only possible 2 to 3 months after surgery. A second intraoperative examination of 24 patients for suspected tumor remnants led to additional resection in 15 patients (34%). CONCLUSIONS: Intraoperative MR imaging undoubtedly offers the option of a second look within the same surgical procedure, if incomplete tumor resection is suspected. Thus, the rate of procedures during which complete tumor removal is achieved can be improved. Furthermore, additional treatments for those patients in whom tumor removal was incomplete can be planned at an early stage, namely just after surgery.     

A comparison of the findings of wrist arthroscopy and magnetic resonance imaging in the investigation of wrist pain

Between 1996 and 1999, 54 patients with wrist pain had magnetic resonance imaging performed using a 1.5 Tesla scanner without a wrist coil. Wrist arthroscopy was performed using a standard technique. The findings were then compared. Magnetic resonance imaging had a low sensitivity for the detection of triangular fibrocartilage complex injuries (0.44) and scapholunate ligament injuries (0.11) when wrist arthroscopy was used as the standard of reference.We conclude that when a magnetoresonance technique that does not employ a dedicated wrist coil is used, a negative magnetic resonance imaging scan does not exclude these two significant injuries.     

Functional sodium magnetic resonance imaging of the intact rat kidney

BACKGROUND: Renal fluid homeostasis depends to a large extent on the sodium concentration gradient along the corticomedullary axis. The spatial distribution and extent of this gradient were previously determined by invasive methods, which yielded a range of results. We demonstrate here the capacity of sodium magnetic resonance imaging (MRI) to quantify non-invasively renal sodium distribution in the intact kidney. METHODS: Sodium MRI was applied to study normal, diuretic, and obstructed rat kidneys in vivo. The images were recorded at 4.7 Tesla using a 3-dimensional gradient echo sequence, with high spatial and temporal resolution. The tissue sodium concentration (TSC) was obtained by taking into account the measured nuclear relaxation rates and MRI visibility relative to a reference saline solution. RESULTS: The corticomedullary sodium gradient increased linearly from the cortex to the inner medulla by approximately 31 mmol/L/mm, from a TSC of approximately 60 mmol/L to approximately 360 mmol/L. Furosemide induced a 50% reduction in the inner-medulla sodium and a 25% increase in the cortical sodium. The kinetics of these changes was related to the specific site and mechanism of the loop diuretic. Distinct profiles of the sodium gradient were observed in acute obstructed kidneys, as well as spontaneously obstructed kidneys. The changes in the sodium gradient correlated with the extent of damage and the residual function of the kidneys. CONCLUSION: Quantitative assessment of the renal corticomedullary sodium gradient by high resolution sodium MRI may help verify new aspects of the kidney concentrating mechanism and serve as a non-invasive diagnostic method of renal function.     

磁共振成像在骨小梁结构研究中的应用

近来的各项研究都表明,骨小梁的强度和易骨折性不仅由骨密度决定,更与骨微结构有关.磁共振成像(MRI)作为一项新兴的非侵人性技术,也证实骨结构决定骨强度.由于MRI图像中骨小梁为低信号而骨髓为高信号,因此对显示骨结构尤为适合.MRI可以深入反映骨小梁内部的三维结构.MRI图像中的各项参数也与骨的生物力学特性和脆性有关.此外,MRI还可在动物或人体研究为疗效的评估提供帮助.本文对MRI的主要特点、技术方法、操作步骤、图像分析及其不足和应用前景作了回顾.