Faculty Bibliography

OBJECTIVE:The purposes of this review are to summarize the indications for MDCT arthrography of the shoulder, highlight the features of MDCT acquisition, and describe the normal and abnormal MDCT arthrographic appearances of the shoulder. CONCLUSION/CONCLUSIONS:MDCT arthrography is a valid alternative for shoulder imaging of patients with contraindications to MRI or after failed MRI. MDCT arthrography is accurate for assessment of a variety of shoulder abnormalities and, with further validation, may become the imaging test of choice for evaluation of the postoperative shoulder.

OBJECTIVE:Limb salvage surgery comprises surgical techniques designed to resect musculoskeletal extremity tumors and subsequently reconstruct a limb with an acceptable oncologic, functional, and cosmetic result. Today, 70-90% of malignant extremity tumors are being treated with limb salvage surgery. CONCLUSION/CONCLUSIONS:The purpose of this article is to describe the operative techniques, review the imaging techniques, and to illustrate imaging findings related to the surgeries in complicated and uncomplicated cases.

OBJECTIVE:The purpose of this study was to prospectively evaluate the accuracy of an augmented reality image overlay system in MRI-guided spinal injection procedures. MATERIALS AND METHODS/METHODS:An augmented reality prototype was used in conjunction with a 1.5-T MRI system. A human lumbar spine phantom was used in which 62 targets were punctured to assess the accuracy of the system. Sixty anatomic targets (facet joint, disk space, and spinal canal) were punctured to assess how the accuracy of the system translated into practice. A visualization software interface was used to compare planned needle paths and final needle locations on coregistered CT images (standard of reference). Outcome variables included entry error, angle error, depth error, target error, successful access of anatomic targets, number of needle adjustments, and time requirements. RESULTS:Accuracy assessments showed entry error of 1.6 ± 0.8 mm, angle error of 1.6° ± 1.0°, depth error of 0.7 ± 0.5 mm, and target error of 1.9 ± 0.9 mm. All anatomic targets (60 of 60 insertions) were successfully punctured, including all 20 facet joints, all 20 disks, and all 20 spinal canals. Four needle adjustments (6.7%) were required. Planning of a single needle path required an average of 55 seconds. A single needle insertion required an average of 1 minute 27 seconds. CONCLUSION/CONCLUSIONS:The augmented reality image overlay system evaluated facilitated accurate MRI guidance for successful spinal procedures in a lumbar spine model. It exhibited potential for simplifying the current practice of MRI-guided lumbar spinal injection procedures.

PURPOSE/OBJECTIVE:To prospectively assess overlay technology in providing accurate and efficient targeting for magnetic resonance (MR) imaging-guided shoulder and hip joint arthrography. MATERIALS AND METHODS/METHODS:A prototype augmented reality image overlay system was used in conjunction with a clinical 1.5-T MR imager. A total of 24 shoulder joint and 24 hip joint injections were planned in 12 human cadavers. Two operators (A and B) participated, each performing procedures on different cadavers using image overlay guidance. MR imaging was used to confirm needle positions, monitor injections, and perform MR arthrography. Accuracy was assessed according to the rate of needle adjustment, target error, and whether the injection was intraarticular. Efficiency was assessed according to arthrography procedural time. Operator differences were assessed with comparison of accuracy and procedure times between the operators. Mann-Whitney U test and Fisher exact test were used to assess group differences. RESULTS:Forty-five arthrography procedures (23 shoulders, 22 hips) were performed. Three joints had prostheses and were excluded. Operator A performed 12 shoulder and 12 hip injections. Operator B performed 11 shoulder and 10 hip injections. Needle adjustment rate was 13% (six of 45; one for operator A and five for operator B). Target error was 3.1 mm±1.2 (standard deviation) (operator A, 2.9 mm±1.4; operator B, 3.5 mm±0.9). Intraarticular injection rate was 100% (45 of 45). The average arthrography time was 14 minutes (range, 6-27 minutes; 12 minutes [range, 6-25 minutes] for operator A and 16 minutes [range, 6-27 min] for operator B). Operator differences were not significant with regard to needle adjustment rate (P=.08), target error (P=.07), intraarticular injection rate (P>.99), and arthrography time (P=.22). CONCLUSION/CONCLUSIONS:Image overlay technology provides accurate and efficient MR guidance for successful shoulder and hip arthrography in human cadavers.

OBJECTIVE:To assess the artefact properties of a MR-compatible carbon fibre needle with a nitinol mandrin in vitro and to report first clinical experiences. MATERIALS AND METHODS/METHODS:In vitro, the carbon fibre/nitinol needle was imaged at different angles against the main magnetic field (1.5T open bore magnet). A gradient echo MR fluoroscopy sequence (GRE: TR 9.3 ms, TE 3.12 ms, bandwidth 200 Hz/pixel, flip-angle 12°) and a fast turbo spin echo sequence (FSE: TR 412 ms, TE 9.7 ms, bandwidth 200 Hz/pixel, flip-angle 150°) were used. Artefact width, needle intensity contrast and needle tip location errors were assessed. In vivo, lumbar periradicular corticosteroid injections and one sclerotherapy were performed with carbon fibre needles (10 procedures) and with titanium alloy needles (2 procedures). The artefact sizes and contrasts were measured. RESULTS:In vitro, artefact diameters of the carbon fibre needle ranged from 3.3 to 4.6 mm, contrasts from 0.11 to 0.52, with larger artefact contrasts and widths with the GRE sequence. Needle tip location errors of -2.1 to -2.8 mm were observed. Decreasing angles to the main field lead to smaller artefacts. In vivo, the carbon fibre/nitinol needle produced smaller artefacts (mean width FSE/GRE: 2.8mm/4.6mm) with lower contrast (0.30-0.42) than the titanium alloy needle (mean width FSE/GRE: 4.1 mm/7.5 mm, contrast 0.60-0.73). CONCLUSIONS:The carbon fibre/nitinol needle is useful for performing MR-guided interventions at 1.5T, producing more subtle artefacts than a titanium alloy needle, but with an incomplete depiction and thus inaccurate localization of the needle tip.

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.

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.