Faculty Bibliography

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 report the safety and diagnostic performance of magnetic resonance (MRI)--guided core biopsy of osseous lesions in children with chronic recurrent multifocal osteomyelitis (CRMO) that were visible on MRI but were occult on radiography and computed tomography (CT). MATERIALS AND METHODS/METHODS:A retrospective analysis of MRI-guided osseous biopsy performed in seven children (four girls and three boys; mean age 13 years (range 11 to 14) with CRMO was performed. Indication for using MRI guidance was visibility of lesions by MRI only. MRI-guided procedures were performed with 0.2-Tesla (Magnetom Concerto; Siemens, Erlangen, Germany; n = 5) or 1.5-T (Magnetom Espree; Siemens; n = 2) open MRI systems. Core needle biopsy was obtained using an MRI-compatible 4-mm drill system. Conscious sedation or general anesthesia was used. Parameters evaluated were lesion visibility, technical success, procedure time, complications and microbiology, cytology, and histopathology findings. RESULTS:Seven of seven (100%) targeted lesions were successfully visualized and sampled. All obtained specimens were sufficient for histopathological analysis. Length of time of the procedures was 77 min (range 64 to 107). No complications occurred. Histopathology showed no evidence of malignancy, which was confirmed at mean follow-up of 50 months (range 28 to 78). Chronic nonspecific inflammation characteristic for CRMO was present in four of seven (58%) patients, and edema with no inflammatory cells was found in three of seven (42%) patients. There was no evidence of infection in any patient. CONCLUSION/CONCLUSIONS:MRI-guided osseous biopsy is a safe and accurate technique for the diagnosis of pediatric CRMO lesions that are visible on MRI only.

OBJECTIVES/OBJECTIVE:To evaluate the efficacy and safety of MRI-guided percutaneous biopsy procedures of head and neck lesions using 0.23T open MRI with optical tracking. METHODS:A retrospective analysis of 77 patients (51 male, 26 female; mean age, 43 years; range, 11-88 years) who underwent MRI-guided percutaneous biopsy of a head and neck lesion was performed. Mean lesion diameter was 3 cm (range, 1-7.8 cm). Rapid gradient echo sequences were used for image guidance. 23/77 lesions were biopsied after intravenous gadolinium. Tissue sampling techniques included needle aspiration (n = 19) and core needle biopsy (n = 58). Outcome variables included technical success, diagnostic accuracy, procedure time and complications. RESULTS:In all patients, a sufficient amount of tissue for pathological analysis was obtained. Pathological analysis diagnosed 41 malignant lesions and 36 benign lesions. In 42 cases, surgical correlation was available. In 35 cases, the final diagnosis was confirmed by imaging and clinical follow-up. MR-guided biopsy had a sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 93.2%, 100%, 100%, 91.7%, and 96%, respectively. Procedure time was 29 min (range, 15-47 min). No major complications occurred. CONCLUSIONS:MRI-guided biopsy of head and neck lesions has a high diagnostic performance and is safe in clinical practice. KEY POINTS/CONCLUSIONS:• MRI-guided biopsy helps clinicians to assess patients with head&neck masses. • Differention of malignant and benign lesions is possible with 96% accuracy. • The safety profile of MRI-guided biopsy of head&neck lesions is favorable. • MRI guidance enables accurate biopsy without the use of ionizing radiation.

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.

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.