Faculty Bibliography

With the development of open-configuration magnetic resonance imaging (MRI) systems, magnetic resonance-compatible navigational tools, and fast pulse sequences, MRI-guided biopsy of musculoskeletal lesions has evolved into an effective and safe, minimally invasive technique. Magnetic resonance-guided percutaneous biopsy of musculoskeletal lesions is especially suited for lesions that are detectable only with MRI, lesions that require double-angulated needle paths, and for patients in which radiation exposure needs to be avoided. In this article, we review pertinent principles, techniques, and clinical applications of low-field MRI for biopsy procedures in the musculoskeletal system.

Magnetic resonance (MR)-guided spine injections describe techniques for selective spine injection procedures, in which MR imaging is used to visualize spinal targets and needle placement, monitor the injected drugs, and detect spread to potentially confounding nearby structures. The introduction of clinical high-field wide-bore MR imaging systems has increased the practicability and availability of MR-guided spine injections. The use of 1.5-T field strength, modern coils, and parallel imaging technology increases the MR signal, which can be utilized for faster temporal image acquisition, higher image resolution, better image contrast, or combinations thereof. Magnetic resonance imaging guidance provides excellent osseous and soft-tissue detail of spinal structures and is well suited to avoid radiation exposure. In this article, we discuss the technical background of interventional MR imaging, review the literature, and illustrate interventional MR imaging techniques of commonly performed spinal injection procedures, including sacroiliac joint injections, lumbar facet joint injections, selective spinal nerve root infiltration, and percutaneous drug delivery to the lumbar sympathetic nerves.

Magnetic resonance imaging (MRI) is promising tool for image-guided therapy. In musculoskeletal setting, image-guided therapy is used to direct diagnostic and therapeutic procedures and to steer patient management. Studies have demonstrated that MRI-guided interventions involving bone, soft tissue, joints, and intervertebral disks are safe and in selected indications can be the preferred action to manage clinical situation. Often, these procedures are technically similar to those performed in other modalities (computed tomography, fluoroscopy) for bone and soft tissue lesions. However, the procedural perception to the operator can be very different to other modalities because of the vastly increased data.Magnetic resonance imaging guidance is particularly advantageous should the lesion not be visible by other modalities, for selective lesion targeting, intra-articular locations, cyst aspiration, and locations adjacent to surgical hardware. Palliative tumor-related pain management such as ablation therapy forms a subset of procedures that are frequently performed under MRI. Another suitable entity for MRI guidance are the therapeutic percutaneous osseous or joint-related benign or reactive conditions such as osteoid osteoma, epiphyseal bone bridging, osteochondritis dissecans, bone cysts, localized bone necrosis, and posttraumatic lesions. In this article, we will describe in detail the technical aspects of performing MRI-guided therapeutic musculoskeletal procedures as well as the clinical indications.

PURPOSE/OBJECTIVE:To evaluate long-term effectiveness of magnetic resonance (MR)-guided radiofrequency (RF) ablation of hepatocellular carcinoma (HCC). MATERIALS AND METHODS/METHODS:This prospective study was approved by the institutional review board. In 20 patients, 28 HCCs (mean diameter, 28.0 mm; range, 6-58 mm) were treated with 25 sessions of MR-guided RF ablation. Previous chemoembolization had been performed in nine HCCs with diameters greater than 3 cm. The entire RF ablation procedures were carried out on a 0.2-T open MR system. Placement of MR-compatible internally cooled electrodes was performed under MR fluoroscopic imaging with fast gradient-echo sequences. Therapeutic assessment was based on dynamic MR-imaging (1.5 T) at a mean follow-up of 24.2 months (range, 6-52 mo). RESULTS:MR-guided RF ablation was technically successful in all 25 sessions (100%), as assessed at the end of each session. T2-weighted sequences were accurate to monitor the ablation zone and supported guidance of overlapping ablations if necessary. Technique effectiveness, defined as complete ablation confirmed at MR imaging 4 months after RF ablation, was achieved in 27 of 28 HCCs (96.4%). To achieve complete ablation, 25 of 27 tumors (92.6%) were treated in a single session and two tumors were treated twice. In one tumor initially defined as having been treated with technically effective RF ablation, local tumor progression was detected more than 4 months after ablation. Consequently, the available follow-up indicated complete ablation in 26 of 28 HCCs (92.9%). There was one major complication (4.0%) and one minor complication (4.0%). CONCLUSIONS:On a long-term basis, MR-guided RF ablation is an effective therapy option in the treatment of HCC.

The posterior tibial tendon (PTT) is the most important dynamic stabilizer of the medial ankle and longitudinal arch of the foot. PTT dysfunction is a degenerative disorder of the tendon, which secondarily involves multiple ligaments, joint capsules, fascia, articulations, and bony structures of the ankle, hindfoot, midfoot, and forefoot. When the tendon progressively attenuates, the patient develops a painful, progressive collapsed flatfoot or pes planovalgus deformity. This comprehensive review illustrates the 3-Tesla magnetic resonance imaging (3T MRI) features of PTT dysfunction. In addition, the reader will gain knowledge of the expected pathologic findings on MRI, as they are related to clinical staging of PTT dysfunction.

PURPOSE/OBJECTIVE:To perform in vitro assessment of needle artifacts with an interactive three-dimensional (3D) near-real-time magnetic resonance (MR) fluoroscopy system for musculoskeletal interventions in a 1.5-T open-bore magnet. MATERIALS AND METHODS/METHODS:One MR-compatible titanium needle, one MR-compatible Inconel (nickel-chromium superalloy) needle, and one MR-compatible carbon fiber needle were imaged with an interactive 3D MR sequence. Slice orientations, measurement parameters (fast low-angle shot, repetition time/echo time of 1,358/5 msec, flip angle of 15 degrees , bandwidth of 250 Hz/pixel; and true fast imaging with steady-state precession, repetition time/echo time of 770/2.2 msec, flip angle of 50 degrees , bandwidth of 558 Hz/pixel), phase encoding directions, and orientations to the main magnetic field (B(0)) were systematically varied. Artifact sizes, normalized artifact contrasts, and tip location errors were assessed for all variations of acquisition parameters and needles and compared with t tests. RESULTS:Mean artifact sizes, normalized artifact contrast, and tip location errors were 22.9 mm, 96%, and 5.4 mm, respectively, for the Inconel needle; 6.1 mm, 70%, and 0.3 mm, respectively, for the titanium needle; and 2.8 mm, 38%, and -1.9 mm, respectively, for the carbon fiber needle. Artifact widths depended on needle materials and needle orientation to B(0), with significant differences on ttests. Artifact contrast did not depend on measurement parameters. No significant influence on artifact character was found for changes in phase encoding direction and slice orientation. CONCLUSIONS:Because of its robustness in depicting needle artifacts, the interactive 3D MR fluoroscopy system appears to be suitable for MR-guided interventions. The titanium needle showed optimal artifacts with all combinations of measurement parameters. Artifacts with the other needles were too large (Inconel) or too small (carbon fiber).

OBJECTIVE:The purpose of this study was to investigate the role of dynamic contrast-enhanced MRI in the differential diagnosis of psoriatic and rheumatoid arthritis in the hand and wrist. SUBJECTS AND METHODS/METHODS:Forty-five consecutive patients (31 patients with rheumatoid arthritis and 14 patients with psoriatic arthritis) were examined in a 3-T whole-body MR unit. After contrast injection, a 3D encoded spoiled gradient-echo sequence was used for measurement of the time course of contrast-medium uptake in the synovial tissue. On the basis of the gained uptake curves, the rate of early enhancement was calculated after 35 and 52 seconds, and the relative enhancement rate was calculated after 35 seconds, 52 seconds, 3 minutes, and 15 minutes (late enhancement). Dynamic contrast-enhanced MRI rates of patients with rheumatoid arthritis and psoriatic arthritis were compared and correlated with laboratory and clinical data. RESULTS:A statistically significant difference between the two groups was found regarding the relative enhancement rate after 15 minutes (p < 0.01). In contrast, no difference in relative enhancement rate was found 35 seconds, 52 seconds, or 3 minutes after contrast injection (p = 0.695, p = 0.573, and p = 0.278, respectively). Regarding the rate of early enhancement at 35 and 52 seconds, no significant difference between patients with rheumatoid arthritis and those with psoriatic arthritis was found. Significant correlations were found between inflammatory parameters and dynamic contrast-enhanced parameters in patients with rheumatoid arthritis but not in those with psoriatic arthritis. CONCLUSION/CONCLUSIONS:Fifteen minutes after contrast injection, a statistically significant difference between rheumatoid arthritis and psoriatic arthritis was found in synovial enhancement that might play an important role in differentiating the two diseases.

OBJECTIVE:The purpose of our study was to test the hypothesis that real-time MRI-guided, selective injection procedures of the temporomandibular joints are feasible, accurate, and safe when performed on a clinical open-bore 1.5-T MR system. MATERIALS AND METHODS/METHODS:A retrospective analysis of 67 injection procedures of the temporomandibular joints (55% [37/67] were therapeutic injections, 27% [18/67] were diagnostic injections, and 18% [12/67] were arthrocentesis procedures), performed in 31 patients (58% [18/31] female, 42% [13/31] male; mean age, 14 years; age range, 3-34 years), was made. Seven of 38 (18%) subjects had two temporally separate procedures. Determinations of skin entry points, puncture, and injection were performed under real-time MRI. Data were assessed for rate of successful injections, quantitative and qualitative image quality, time requirements, and occurrence of complications. RESULTS:Drug delivery was successful in all procedures. The quality of real-time FLASH 2D MR images was sufficient in all cases. Real-time MRI proved to be helpful to achieve high rates of intraarticular injections. Contrast-to-noise ratios were sufficiently high for good delineation of relevant structures. Average length of time was 25 minutes (range, 16-53 minutes). No major complications occurred. CONCLUSION/CONCLUSIONS:We accept the hypothesis that real-time MRI-guided selective injection procedures of the temporomandibular joints are feasible, accurate, and safe when performed on a clinical open-bore 1.5-T MR system.