Faculty Bibliography

OBJECTIVES/OBJECTIVE:To prospectively assess the technical performance of an augmented reality system for MR-guided spinal injection procedures. METHODS:The augmented reality system was used with a clinical 1.5-T MRI system. A total of 187 lumbosacral spinal injection procedures (epidural injection, spinal nerve root injection, facet joint injection, medial branch block, discography) were performed in 12 human cadavers. Needle paths were planned with the Perk Station module of 3D Slicer software on high-resolution MR images. Needles were placed under augmented reality MRI navigation. MRI was used to confirm needle locations. T1-weighted fat-suppressed MRI was used to visualise the injectant. Outcome variables assessed were needle adjustment rate, inadvertent puncture of non-targeted structures, successful injection rate and procedure time. RESULTS:Needle access was achieved in 176/187 (94.1 %) targets, whereas 11/187 (5.9 %) were inaccessible. Six of 11 (54.5 %) L5-S1 disks were inaccessible, because of an axial obliquity of 30˚ (27˚-34˚); 5/11 (45.5 %) facet joints were inaccessible because of osteoarthritis or fusion. All accessible targets (176/187, 94.1 %) were successfully injected, requiring 47/176 (26.7 %) needle adjustments. There were no inadvertent punctures of vulnerable structures. Median procedure time was 10.2 min (5-19 min). CONCLUSIONS:Image overlay navigated MR-guided spinal injections were technically accurate. Disks with an obliquity ≥27˚ may be inaccessible.

PURPOSE/OBJECTIVE:A clinical augmented reality guidance system was developed for MRI-guided musculoskeletal interventions Magnetic Resonance Image Overlay System (MR-IOS). The purpose of this study was to assess MRI compatibility, system accuracy, technical efficacy, and operator performance of the MR-IOS. METHODS AND MATERIALS/METHODS:The impact of the MR-IOS on the MR environment was assessed by measuring image quality with signal-to-noise ratio (SNR) and signal intensity uniformity with the system in various on/off states. The system accuracy was assessed with an in-room preclinical experiment by performing 62 needle insertions on a spine phantom by an expert operator measuring entry, depth, angle, and target errors. Technical efficacy and operator performance were tested in laboratory by running an experiment with 40 novice operators (20 using freehand technique versus 20 MR-IOS-guided) with each operator inserting 10 needles into a geometric phantom. Technical efficacy was measured by comparing the success rates of needle insertions between the two operator groups. Operator performance was assessed by comparing total procedure times, total needle path distance, presumed tissue damage, and speed of individual insertions between the two operator groups. RESULTS:The MR-IOS maximally altered SNR by 2% with no perceptible change in image quality or uniformity. Accuracy assessment showed mean entry error of 1.6 ± 0.6 mm, depth error of 0.7 ± 0.5 mm, angle error of 1.5 ± 1.1°, and target error of 1.9 ± 0.8 mm. Technical efficacy showed a statistically significant difference (p = 0.031) between success rates (freehand 35.0% vs. MR-IOS 80.95%). Operator performance showed: mean total procedure time of 40.3 ± 4.4 (s) for freehand and 37.0 ± 3.7 (s) for MR-IOS (p = 0.584), needle path distances of 152.6 ± 15.0 mm for freehand and 116.9 ± 8.7 mm for MR-IOS (p = 0.074), presumed tissue damage of 7,417.2 ± 955.6 mm(2) for freehand and 6062.2 ± 678.5 mm(2) for MR-IOS (p = 0.347), and speed of insertion 5.9 ± 0.4 mm/s for freehand and 4.3 ± 0.3 mm/s for MR-IOS (p = 0.003). CONCLUSION/CONCLUSIONS:The MR-IOS is compatible within a clinical MR imaging environment, accurate for needle placement, technically efficacious, and improves operator performance over the unassisted insertion technique. The MR-IOS was found to be suitable for further testing in a clinical setting.

PURPOSE/OBJECTIVE:To assess the performance of sterile saline solution as the sole contrast agent for percutaneous magnetic resonance imaging (MRI)-guided epidural injections at 1.5 T. METHODS:A retrospective analysis of two different techniques of MRI-guided epidural injections was performed with either gadolinium-enhanced saline solution or sterile saline solution for documentation of the epidural location of the needle tip. T1-weighted spoiled gradient echo (FLASH) images or T2-weighted single-shot turbo spin echo (HASTE) images visualized the test injectants. Methods were compared by technical success rate, image quality, table time, and rate of complications. RESULTS:105 MRI-guided epidural injections (12 of 105 with gadolinium-enhanced saline solution and 93 of 105 with sterile saline solution) were performed successfully and without complications. Visualization of sterile saline solution and gadolinium-enhanced saline solution was sufficient, good, or excellent in all 105 interventions. For either test injectant, quantitative image analysis demonstrated comparable high contrast-to-noise ratios of test injectants to adjacent body substances with reliable statistical significance levels (p < 0.001). The mean table time was 22 ± 9 min in the gadolinium-enhanced saline solution group and 22 ± 8 min in the saline solution group (p = 0.75). CONCLUSION/CONCLUSIONS:Sterile saline is suitable as the sole contrast agent for successful and safe percutaneous MRI-guided epidural drug delivery at 1.5 T.

Multi-detector computed tomography angiography (MDCTA) of the lower extremities is an integral part of the decision-making process of lower extremity trauma. MDCTA can be integrated into multiphasic whole-body trauma MDCT and has replaced the traditional gold standard of catheter-based angiography as the preferred technique for the initial assessment of lower extremity trauma in many institutions worldwide. Advances in MDCT technology enable high speed simultaneous evaluation of both complete lower extremities, rapid image reconstruction, and advanced image visualization for the noninvasive and accurate diagnosis of vascular, including hematoma, active extravasation, vasospasm, stenosis, external compression, occlusion, intimal injury and dissection, arteriovenous fistulas, and pseudoaneurysm formation. In this exhibit, we outline the role of MDCTA in the management of lower extremity trauma, review current MDCT protocols and the practical use of advanced visualization techniques, and illustrate typical MDCTA findings, pearls, and pitfalls, which help to accurately characterize vascular injury and guide management.

OBJECTIVE:The objective of this study was to evaluate the diagnostic performance and safety of magnetic resonance (MR) imaging-guided percutaneous mediastinal biopsy procedures using a 0.23-T open MR system with optical tracking navigation. MATERIALS AND METHODS/METHODS:A retrospective analysis of 59 participants (38 males and 21 females; mean age, 45 years; range, 16-73 years) who underwent MR imaging-guided percutaneous mediastinal biopsy procedures was performed. The access techniques included extrapleural (40 of 59; 67.8%) and transpulmonary (19 of 59; 32.2%) needle paths. Tissue sampling techniques included fine-needle aspiration (22 of 59; 37.3%) and core-needle biopsy (37 of 59; 62.7%). Histopathological analysis of surgical specimen and clinical and imaging follow-ups were used as the reference standard. The procedures were evaluated for technical success rate, number of biopsy passes, diagnostic performance, procedure time, and complications. RESULTS:Technical success was achieved in 57 of the 59 procedures (96.6%). For the fine-needle aspiration, a mean of 3 passes (range, 2-4 passes) was performed. For the core-needle biopsy, a mean of 4 passes (range, 3-6 passes) was performed. Pathological and cytological analysis of biopsy specimens showed 41 of 57 malignant lesions (71.9%) and 16 of 57 benign lesions (28.1%), with a sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 93.2% (41 of 44), 100% (13 of 13), 100% (41 of 41), 81.2% (13 of 16), and 94.7% (54 of 57), respectively. Procedure time was 30 minutes (range, 20-50 minutes). Mild hemoptysis occurred in 3 cases, and in 2 cases, a small pneumothorax occurred. CONCLUSIONS:Magnetic resonance imaging-guided biopsy of mediastinal masses has a high diagnostic performance and is safe for use in clinical practice.

OBJECTIVE:To assess the feasibility, technical success, and effectiveness of high-resolution magnetic resonance (MR)-guided posterior femoral cutaneous nerve (PFCN) blocks. MATERIALS AND METHODS/METHODS:A retrospective analysis of 12 posterior femoral cutaneous nerve blocks in 8 patients [6 (75%) female, 2 (25%) male; mean age, 47 years; range, 42-84 years] with chronic perineal pain suggesting PFCN neuropathy was performed. Procedures were performed with a clinical wide-bore 1.5-T MR imaging system. High-resolution MR imaging was utilized for visualization and targeting of the PFCN. Commercially available, MR-compatible 20-G needles were used for drug delivery. Variables assessed were technical success (defined as injectant surrounding the targeted PFCN on post-intervention MR images) effectiveness, (defined as post-interventional regional anesthesia of the target area innervation downstream from the posterior femoral cutaneous nerve block), rate of complications, and length of procedure time. RESULTS:MR-guided PFCN injections were technically successful in 12/12 cases (100%) with uniform perineural distribution of the injectant. All blocks were effective and resulted in post-interventional regional anesthesia of the expected areas (12/12, 100%). No complications occurred during the procedure or during follow-up. The average total procedure time was 45 min (30-70) min. CONCLUSIONS:Our initial results demonstrate that this technique of selective MR-guided PFCN blocks is feasible and suggest high technical success and effectiveness. Larger studies are needed to confirm our initial results.

PURPOSE/OBJECTIVE:The purpose of this study was to prospectively test the hypothesis that image overlay technology facilitates accurate navigation for magnetic resonance (MR)-guided osseous biopsy. MATERIALS AND METHODS/METHODS:A prototype augmented reality image overlay system was used in conjunction with a clinical 1.5-T MR imaging system. Osseous biopsy of a total of 16 lesions was planned in 4 human cadavers with osseous metastases. A loadable module of 3D Slicer open-source medical image analysis and visualization software was developed and used for display of MR images, lesion identification, planning of virtual biopsy paths, and navigation of drill placement. The osseous drill biopsy was performed by maneuvering the drill along the displayed MR image containing the virtual biopsy path into the target. The drill placement and the final drill position were monitored by intermittent MR imaging. Outcome variables included successful drill placement, number of intermittent MR imaging control steps, target error, number of performed passes and tissue sampling, time requirements, and pathological analysis of the obtained osseous core specimens including adequacy of specimens, presence of tumor cells, and degree of necrosis. RESULTS:A total of 16 osseous lesions were sampled with percutaneous osseous drill biopsy. Eight lesions were located in the osseous pelvis (8/16, 50%) and 8 (8/16, 50%) lesions were located in the thoracic and lumbar spine. Lesion size was 2.2 cm (1.1-3.5 cm). Four (2-8) MR imaging control steps were required. MR imaging demonstrated successful drill placement inside 16 of the 16 target lesions (100%). One needle pass was sufficient for accurate targeting of all lesions. One tissue sample was obtained in 8 of the 16 lesions (50%); 2, in 6 of the 16 lesions (38%); and 3, in 2 of the 16 lesions (12%). The target error was 4.3 mm (0.8-6.8 mm). Length of time required for biopsy of a single lesion was 38 minutes (20-55 minutes). Specimens of 15 of the 16 lesions (94%) were sufficient for pathological evaluation. Of those 15 diagnostic specimens, 14 (93%) contained neoplastic cells, whereas 1 (7%) specimen demonstrated bone marrow without evidence of neoplastic cells. Of those 14 diagnostic specimens, 11 (79%) were diagnostic for carcinoma or adenocarcinoma, which was concordant with the primary neoplasm, whereas, in 3 of the 14 diagnostic specimens (21%), the neoplastic cells were indeterminate. CONCLUSIONS:Image overlay technology provided accurate navigation for the MR-guided biopsy of osseous lesions of the spine and the pelvis in human cadavers at 1.5 T. The high technical and diagnostic yield supports further evaluation with clinical trials.

Imaging studies are central to the evaluation of persistent or recurrent symptoms after hip arthroplasty. The evaluation starts with radiographs and may be followed by arthrography, aspiration, scintigraphy, sonography, computed tomography, and MR imaging. Common etiologies of a painful or dysfunctional hip arthroplasty are mechanical loosening, polyethylene wear-induced osteolysis, adverse local tissue reaction to metal wear products, infection, fractures, heterotopic ossification, tendinopathy, and nerve injury. MR imaging with optimized protocols and dedicated techniques for metal artifact reduction is the most comprehensive imaging modality. In this article, we discuss and illustrate the imaging appearances of these conditions with a focus on the MR imaging evaluation.

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.