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1.  18F-FDG PET of the hands with a dedicated high-resolution PEM system (arthro-PET): correlation with PET/CT, radiography and clinical parameters 
The aim of this study was to prospectively determine the feasibility and compare the novel use of a positron emission mammography (PEM) scanner with standard PET/CT for evaluating hand osteoarthritis (OA) with 18F-FDG.
Institutional review board approval and written informed consent were obtained for this HIPAA-compliant prospective study in which 14 adults referred for oncological 18F-FDG PET/CT underwent dedicated hand PET/CT followed by arthro-PET using the PEM device. Hand radiographs were obtained and scored for the presence and severity of OA. Summed qualitative and quantitative joint glycolytic scores for each modality were compared with the findings on plain radiography and clinical features.
Eight patients with clinical and/or radiographic evidence of OA comprised the OA group (mean age 73±7.7 years). Six patients served as the control group (53.7±9.3 years). Arthro-PET quantitative and qualitative joint glycolytic scores were highly correlated with PET/CT findings in the OA patients (r=0.86. p =0.007; r=0.94, p=0.001). Qualitative arthro-PET and PET/CT joint scores were significantly higher in the OA patients than in controls (38.7±6.6 vs. 32.2±0.4, p=0.02; 37.5±5.4 vs. 32.2±0.4, p=0.03, respectively). Quantitative arthro-PET and PET/CT maximum SUV-lean joint scores were higher in the OA patients, although they did not reach statistical significance (20.8±4.2 vs. 18±1.8, p= 0.13; 22.8±5.38 vs. 20.1±1.54, p=0.21). By definition, OA patients had higher radiographic joint scores than controls (30.9±31.3 vs. 0, p=0.03).
Hand imaging using a small field of view PEM system (arthro-PET) with FDG is feasible, performing comparably to PET/CT in assessing metabolic joint activity. Arthro-PET and PET/CT showed higher joint FDG uptake in OA. Further exploration of arthro-PET in arthritis management is warranted.
PMCID: PMC4322913  PMID: 25134669
PET/CT; Positron emission mammography (PEM); Osteoarthritis (OA); Arthritis; 18F-Fluoro- 2-deoxy-D-glucose (FDG)
2.  Spectrum of magnetic resonance imaging findings in congenital lumbar spinal stenosis 
AIM: To investigate whether congenital lumbar spinal stenosis (CLSS) is associated with a specific degenerative changes of the lumbar spine.
METHODS: The lumbar spine magnetic resonance imaging studies of 52 subjects with CLSS and 48 control subjects were retrospectively evaluated. In each examination, the five lumbar levels were assessed for the presence or absence of circumferential or shallow annular bulges, annular tears, anterior or posterior disc herniations, epidural lipomatosis, Schmorl’s nodes, spondylolisthesis, pars defects, and stress reactions of the posterior vertebral elements.
RESULTS: Compared to control individuals, subjects with CLSS exhibited increased incidence of circumferential and shallow annular bulges, annular tears, disc herniations and spondylolisthesis (P < 0.05).
CONCLUSION: CLSS is associated with increased incidence of degenerative changes in specific osseous and soft-tissue elements of the lumbar spine.
PMCID: PMC4266837  PMID: 25516864
Congenital lumbar spinal stenosis; Magnetic resonance imaging; Imaging findings; Degenerative changes; Low back pain
3.  High-resolution measurements of the multilayer ultra-structure of articular cartilage and their translational potential 
Current musculoskeletal imaging techniques usually target the macro-morphology of articular cartilage or use histological analysis. These techniques are able to reveal advanced osteoarthritic changes in articular cartilage but fail to give detailed information to distinguish early osteoarthritis from healthy cartilage, and this necessitates high-resolution imaging techniques measuring cells and the extracellular matrix within the multilayer structure of articular cartilage. This review provides a comprehensive exploration of the cellular components and extracellular matrix of articular cartilage as well as high-resolution imaging techniques, including magnetic resonance image, electron microscopy, confocal laser scanning microscopy, second harmonic generation microscopy, and laser scanning confocal arthroscopy, in the measurement of multilayer ultra-structures of articular cartilage. This review also provides an overview for micro-structural analysis of the main components of normal or osteoarthritic cartilage and discusses the potential and challenges associated with developing non-invasive high-resolution imaging techniques for both research and clinical diagnosis of early to late osteoarthritis.
PMCID: PMC4061724  PMID: 24946278
4.  Recurrent ulnar nerve entrapment at the elbow: Correlation of surgical findings and 3-Tesla magnetic resonance neurography 
The authors describe the correlation between 3-Tesla magnetic resonance neurography (MRN) and surgical findings in two patients who underwent multiple previous failed ulnar nerve surgeries. MRN correctly localized the site of the abnormality. Prospectively observed MRN findings of perineural fibrosis, ulnar nerve re-entrapment abnormalities, medial antebrachial cutaneous neuroma and additional median nerve entrapment were confirmed surgically.
PMCID: PMC3805642  PMID: 24421652
3T MRN; MR neurography; Subcutaneous transposition; Submuscular transposition; Ulnar nerve entrapment
Muscle & nerve  2012;45(5):755-761.
The diagnosis of amyloid myopathy is delayed when monoclonal gammopathies are not detected on initial testing and muscle biopsies are nondiagnostic, and the EMG and symptoms can mimic an inflammatory myopathy.
Case report of a patient presenting with severe progressive muscle weakness of unclear etiology despite an extensive workup including two nondiagnostic muscle biopsies.
Directed by MRI, a third biopsy revealed amyloid angiopathy and noncongophilic kappa light chain deposition in scattered subsarcolemmal rings and perimysial regions. A serum free light chain (FLC) assay revealed a kappa monoclonal gammopathy, which was not detected by multiple immunofixations.
The spectrum of immunoglobulin deposition in muscle is similar to other organs. It comprises a continuum that includes parenchymal amyloid deposition, amyloid angiopathy, and noncongophilic Light Chain Deposition Disease (LCDD). We recommend including the FLC assay in the routine investigation for monoclonal gammopathies. This case also highlights the value of MRI-guided muscle biopsy.
PMCID: PMC4133774  PMID: 22499107
amyloid; gammopathy; light chain deposition; MRI; myopathy
6.  Role of MR spectroscopy in musculoskeletal imaging 
Magnetic resonance spectroscopy (MRS) is an imaging approach that allows for the noninvasive molecular characterization of a region of interest. By detecting signals of water, lipids, and other metabolites, MRS can provide metabolic information for lesion characterization and assessment of treatment response. Although MRS has been routinely used in the brain, clinical applications within the musculoskeletal system have only more recently emerged. The aim of this article is to review the technical considerations for performing MRS in the musculoskeletal system, focusing on proton MRS, and to discuss its potential roles in musculoskeletal tumor imaging and the assessment of muscle physiology and disease.
PMCID: PMC4126135  PMID: 25114383
Choline; MR spectroscopy; musculoskeletal
7.  Bone marrow lesions: A systematic diagnostic approach 
Bone marrow lesions on magnetic resonance (MR) imaging are common and may be seen with various pathologies. The authors outline a systematic diagnostic approach with proposed categorization of various etiologies of bone marrow lesions. Utilization of typical imaging features on conventional MR imaging techniques and other problem-solving techniques, such as chemical shift imaging and diffusion-weighted imaging (DWI), to achieve accurate final diagnosis has been highlighted.
PMCID: PMC4126144  PMID: 25114392
Bone marrow lesion; chemical shift imaging; diffusion; magnetic resonance imaging
8.  Magnetic Resonance Imaging Predictors of Surgical Outcome in Patients with Lumbar Intervertebral Disc Herniation 
Spine  2013;38(14):1216-1225.
Study Design
A retrospective cohort design
To determine if baseline MRI findings including central/foraminal stenosis, Modic change, disc morphology, facet arthropathy, disc degeneration, nerve root impingement, and thecal sac compression are associated with differential surgical treatment effect.
Summary of Background Data
Intervertebral Disc Herniation (IDH)remains the most common source of lumbar radiculopathy treated either with discectomy or non-operative intervention. Although MRI remains the reliable gold standard for diagnosis, uncertainty surrounds the relationship between MRI findings and treatment outcomes.
Three-hundred-and-seven “complete” images from patients enrolled in a previous trial were de-identified and evaluated by one of 4 independent readers. Findings were compared to outcome measures including the Oswestry Disability Index. Differences in surgery and non-operative treatment outcomes were evaluated between image characteristic subgroups and TE determined by the difference in ODI scores.
The cohort was comprised of 40% females with an average age of 41.5 (±11.6), 61% of which underwent discectomy for IDH. Patients undergoing surgery with Modic type I endplate changes had worse outcomes (−26.4 versus −39.7 for none and −39.2 for type 2, p=0.002) and smaller treatment effect (−3.5 versus −19.3 for none and −15.7 for type 2, p=0.003). Those with compression >=1/3 showed the greatest improvement within the surgical group (−41.9 for >=1/3 versus −31.6 for none and −38.1 for <1/3,p=0.007), and the highest TE (−23 compared to −11.7 for none and −15.2 for <1/3, p=0.015). Furthermore, patients with minimal nerve root impingement demonstrated worse surgical outcomes(−26.5 versus −41.1 for “displaced” and −38.9 for “compressed”, p=0.016).
Among patients with IDH, those with thecal sac compression >=1/3 had greater surgical treatment effect than those with small disc herniations and Modic type I changes. Additionally, patients with nerve root “compression” and “displacement” benefit more from surgery than those with minimal nerve-root impingement.
PMCID: PMC3683115  PMID: 23429684
Intervertebral Disc Herniation; Lumbar; surgical outcome; Magnetic Resonance Imaging; Modic Change; Thecal Sac Compression
9.  Plexiform nerve sheath tumor or vascular malformation—role of advanced MR neurography and diffusion tensor imaging 
Skeletal radiology  2013;42(7):1007-1010.
The authors report a vascular malformation mimicking a plexiform peripheral nerve sheath tumor. Three Tesla magnetic resonance neurography with high-resolution anatomic and advanced functional diffusion tensor imaging was helpful in evaluating full extent of the lesion and characterizing its internal architecture.
PMCID: PMC3991119  PMID: 23519761
Vascular Malformation; Magnetic Resonance Neurography; Nerve Sheath Tumor
10.  Inhibition of TGF–β signaling in subchondral bone mesenchymal stem cells attenuates osteoarthritis 
Nature medicine  2013;19(6):704-712.
Osteoarthritis is a highly prevalent and debilitating joint disorder. There is no effective medical therapy for osteoarthritis due to limited understanding of osteoarthritis pathogenesis. We show that TGF–β1 is activated in the subchondral bone in response to altered mechanical loading in an anterior cruciate ligament transection (ACLT) osteoarthritis mouse model. TGF–β1 concentrations also increased in human osteoarthritis subchondral bone. High concentrations of TGF–β1 induced formation of nestin+ mesenchymal stem cell (MSC) clusters leading to aberrant bone formation accompanied by increased angiogenesis. Transgenic expression of active TGF–β1 in osteoblastic cells induced osteoarthritis. Inhibition of TGF–β activity in subchondral bone attenuated degeneration of osteoarthritis articular cartilage. Notably, knockout of the TGF–β type II receptor (TβRII) in nestin+ MSCs reduced development of osteoarthritis in ACLT mice. Thus, high concentrations of active TGF–β1 in the subchondral bone initiated the pathological changes of osteoarthritis, inhibition of which could be a potential therapeutic approach.
PMCID: PMC3676689  PMID: 23685840
11.  Sports Health Orthopaedic Magnetic Resonance Imaging Challenge 
Sports Health  2012;4(3):261-263.
PMCID: PMC3435933  PMID: 23016097
12.  MR Neurography: Advances 
High resolution and high field magnetic resonance neurography (MR neurography, MRN) is shown to have excellent anatomic capability. There have been considerable advances in the technology in the last few years leading to various feasibility studies using different structural and functional imaging approaches in both clinical and research settings. This paper is intended to be a useful seminar for readers who want to gain knowledge of the advancements in the MRN pulse sequences currently used in clinical practice as well as learn about the other techniques on the horizon aimed at better depiction of nerve anatomy, pathology, and potential noninvasive evaluation of nerve degeneration or regeneration.
PMCID: PMC3622412  PMID: 23589774
13.  High resolution imaging of tunnels by magnetic resonance neurography 
Skeletal radiology  2011;41(1):15-31.
Peripheral nerves often traverse confined fibro-osseous and fibro-muscular tunnels in the extremities, where they are particularly vulnerable to entrapment and compressive neuropathy. This gives rise to various tunnel syndromes, characterized by distinct patterns of muscular weakness and sensory deficits. This article focuses on several upper and lower extremity tunnels, in which direct visualization of the normal and abnormal nerve in question is possible with high resolution 3T MR neurography (MRN). MRN can also serve as a useful adjunct to clinical and electrophysiologic exams by discriminating adhesive lesions (perineural scar) from compressive lesions (such as tumor, ganglion, hypertrophic callous, or anomalous muscles) responsible for symptoms, thereby guiding appropriate treatment.
PMCID: PMC3158963  PMID: 21479520
MRI; MR neurography; Peripheral nerve; Tunnels; 3T
14.  Case Report: Bilateral Proximal Epiphyseal Clavicular Stress-related Lesions in a Male Gymnast 
Stress lesions of the upper extremity are relatively uncommon, and physeal stress lesions of the clavicle are rare. We present a case of bilateral physeal stress-related lesions of the proximal clavicular growth plate near the sternoclavicular joint in an adolescent male gymnast.
Case Description
A 13-year-old gymnast presented with a 3-week history of insidious onset of pain in the proximal clavicular area of his left shoulder. He had no pain at rest or at night. He recently had added a new maneuver to his routine. His radiographs were normal, but further study with CT scanning confirmed a stress lesion of his proximal clavicular physis. The lesion healed with time, and he returned to gymnastics with no symptoms. Approximately 5 months after the initial symptoms on the left side, he felt a pop and immediate pain in his right sternoclavicular joint area while doing a routine. Imaging revealed a chronic stress lesion of the proximal physis similar to that of the other side. The patient achieved healing with rest and returned to gymnastics with no limitations.
Literature Review
Physeal stress-related lesions of the proximal clavicular physis have not been reported in the literature.
Purpose and Clinical Relevance
Medial clavicle pain in adolescent gymnasts may be secondary to stress-related lesions of the proximal clavicular growth plate. Such lesions are rare.
PMCID: PMC3237983  PMID: 22045068
15.  A Quantitative Method to Assess Focal Acetabular Overcoverage Resulting From Pincer Deformity Using CT Data 
Current assessment techniques for focal acetabular overcoverage are neither consistent nor quantitatively accurate.
We propose: (1) a method to precisely quantify the amount of focal acetabular overcoverage in a patient’s pincer deformity based on CT data; (2) to evaluate the consistency of this method; and (3) to compare the method with conventional radiographic assessments.
We developed a method to assess focal acetabular overcoverage using points selected from CT scans along the acetabular rim after realigning the pelvis into a neutral position. Using four resampled and segmented pelvic CT scans of cadaveric specimens with virtually induced impingement, two observers independently tested the algorithm’s consistency. Our algorithm assessed the amount of focal acetabular overcoverage using CT data and projected data from reconstructed radiographs.
(1) We successfully showed the feasibility of the software to produce consistent, quantitative measurements. (2) Testing showed the average difference between observers in aligning the pelvis was 0.42°, indicative of a consistent approach. (3) Differences between measurements on three-dimensional (3-D) CT and simulated radiographs were significant.
The proposed method represents a new avenue in consistently quantifying focal acetabular overcoverage using CT models while correcting for pelvic tilt and rotation. Our analysis confirms AP hip radiograph simulations overestimate the amount of overhanging acetabular rim in a pincer deformity.
Clinical Relevance
This technique has potential to improve preoperative diagnostic accuracy and enhance surgical planning for correction of a pincer deformity resulting from focal acetabular overcoverage.
PMCID: PMC3171557  PMID: 21748515
16.  Talbot phase-contrast X-ray imaging for the small joints of the hand 
Physics in medicine and biology  2011;56(17):5697-5720.
A high resolution radiographic method for soft tissues in the small joints of the hand would aid in the study and treatment of Rheumatoid Arthritis (RA) and Osteoarthritis (OA), which often attacks these joints. Of particular interest would be imaging with <100 μm resolution the joint cartilage, whose integrity is a main indicator of disease. Differential phase-contrast or refraction based X-ray imaging (DPC) with Talbot grating interferometers could provide such a method, since it enhances soft tissue contrast and it can be implemented with conventional X-ray tubes. A numerical joint phantom was first developed to assess the angular sensitivity and spectrum needed for a hand DPC system. The model predicts that due to quite similar refraction indexes for joint soft tissues, the refraction effects are very small, requiring high angular resolution. To compare our model to experiment we built a high resolution bench-top interferometer using 10 μm period gratings, a W anode tube and a CCD based detector. Imaging experiments on animal cartilage and on a human finger support the model predictions. For instance, the estimated difference between the index of refraction of cartilage and water is of only several percent at ~25 keV mean energy, comparable to that between the linear attenuation coefficients. The potential advantage of DPC imaging comes thus mainly from the edge enhancement at the soft tissue interfaces. Experiments using a cadaveric human finger are also qualitatively consistent with the joint model, showing that refraction contrast is dominated by tendon embedded in muscle, with the cartilage layer difficult to observe in our conditions. Nevertheless, the model predicts that a DPC radiographic system for the small hand joints of the hand could be feasible using a low energy quasi-monochromatic source, such as a K-edge filtered Rh or Mo tube, in conjunction with a ~2 m long ‘symmetric’ interferometer operated in a high Talbot order.
PMCID: PMC3166798  PMID: 21841214
18.  An Online Evidence-Based Decision Support System for Distinguishing Benign from Malignant Vertebral Compression Fractures by Magnetic Resonance Imaging Feature Analysis 
Journal of Digital Imaging  2010;24(3):507-515.
Decision support systems have been used to promote the practice of evidence-based medicine. Computer-assisted diagnosis can serve as one element of evidence-based radiology. One area where such tools may provide benefit is analysis of vertebral compression fractures (VCFs), which can be a challenge in MRI interpretation. VCFs may be benign or malignant in etiology, and several MRI features may help to make this important distinction. We describe a web-based decision support system for discriminating benign from malignant VCFs as a prototype for a more general diagnostic decision support framework for radiologists. The system has three components: a feature checklist with an image gallery derived from proven reference cases, a prediction model, and a reporting mechanism. The website allows users to input the findings for a case to be interpreted using a structured feature checklist. The image gallery complements the checklist, for clarity and training purposes. The input from the checklist is then used to calculate the likelihood of malignancy by a logistic regression prediction model. Standardized report text is generated that summarizes pertinent positive and negative findings. This computer-assisted diagnosis system demonstrates the integration of three areas where diagnostic decision support can aid radiologists: first, in image interpretation, through feature checklists and illustrative image galleries; second, in feature-based prediction modeling; and third, in structured reporting. We present a diagnostic decision support tool that provides radiologists with evidence-based guidance for discriminating benign from malignant VCF. This model may be useful in other difficult-diagnosis situations and requires further clinical testing.
PMCID: PMC3092053  PMID: 20680384
Decision support; computer-assisted diagnosis; compression fracture; magnetic resonance imaging; structured reporting
19.  Prediction of transitional lumbosacral anatomy on magnetic resonance imaging of the lumbar spine 
World Journal of Radiology  2012;4(3):97-101.
AIM: To evaluate two simple angle measurements for predicting lumbosacral transitional vertebra (LSTV) in magnetic resonance imaging (MRI) studies of the spine.
METHODS: The lumbar spine MRI studies of 50 subjects with LSTV and 50 subjects with normal lumbosacral anatomy were retrospectively evaluated. In each study, the mid-sagittal T2-weighted image was used to measure the angle formed by a line parallel to the superior surface of the sacrum and a line perpendicular to the axis of the scan table (A-angle), as well as the angle formed by a line parallel to the superior endplate of the L3 vertebra and a line parallel to the superior surface of the sacrum (B-angle).
RESULTS: The total study population consisted of 100 subjects (46 males, 54 females, 51 ± 16 years old). There were no differences in age and sex between the two groups. Both A-angle and B-angle were significantly increased in subjects with LSTV compared to controls (P < 0.05). The optimal cut-off values of A-angle and B-angle for the prediction of LSTV were 39.8° (sensitivity = 80%, specificity = 80%, accuracy = 83%; 95% confidence interval = 74%-89%, P = 0.0001) and 35.9° (sensitivity = 80%, specificity = 54%, accuracy = 69%; 95% confidence interval = 59%-78%, P = 0.0005), respectively.
CONCLUSION: On sagittal MR images of the lumbar spine, an increased A-angle and/or B-angle should alert the radiologist to the presence of LSTV.
PMCID: PMC3314934  PMID: 22468190
Lumbosacral transitional vertebra; Magnetic resonance imaging; Lumbar spine; Angle; Prediction
20.  Superolateral Hoffa’s Fat Pad Edema: Association With Patellofemoral Maltracking and Impingement 
AJR. American journal of roentgenology  2010;195(6):1367-1373.
Nonelderly patients presenting with knee pain often have patellofemoral maltracking or impingement abnormalities. There is a relative paucity of literature on the incidence and significance of impingement-related edema of the superolateral aspect of Hoffa’s (infrapatellar) fat pad in these cases. Our study was designed to systematically evaluate the correlation of superolateral Hoffa’s fat pad edema with various anatomic parameters of trochlear morphology and patellar alignment.
We evaluated 50 knee MRI examinations in 47 patients for the presence of edema in superolateral Hoffa’s fat pad and associated anatomic abnormalities of the patellofemoral joint.
Of the 50 examinations, 25 (50%) showed superolateral Hoffa’s fat pad edema, and statistically significant differences were seen between those with and without edema with respect to sex (6/22 men vs 19/28 women) and patellar tendon patellar–length ratio (1.3 ± 0.16 and 1.1 ± 0.12 for those with and without edema, respectively).
The findings in our study suggest that edema in superolateral Hoffa’s fat pad may be an important indicator of underlying patellofemoral maltracking or impingement in younger, symptomatic patients.
PMCID: PMC3094907  PMID: 21098197
Hoffa’s fat pad edema; infrapatellar fat pad; malalignment; patellofemoral impingement
22.  A systematised MRI approach to evaluating the patellofemoral joint 
Skeletal radiology  2010;40(4):375-387.
Knee pain in young patients is a common indication for knee MRI. Many static and dynamic internal derangements of the patellofemoral joint in these patients lead to various secondary MRI findings. This article focuses on how to systematically approach, detect, and emphasize the importance of these findings in the diagnosis of patellofemoral tracking and impingement syndromes with relevant case examples.
PMCID: PMC2919651  PMID: 20217407
Patellofemoral; Impingement; Maltracking; MRI
23.  Subscapularis Strain From Swinging a Baseball Bat in an Adolescent With Closed Physis 
Sports Health  2011;3(3):283-286.
A healthy 16-year-old female baseball player was referred by her pediatrician for evaluation of pain in her right, dominant shoulder. The pain had begun insidiously 4 weeks previously after several sessions of batting practice and had worsened until she could not participate in baseball, even with low doses of ibuprofen. She was not participating in any other sports or weight lifting and had had no previous incidents of shoulder pain, but she did have a history of being able to voluntarily subluxate the right shoulder since she was a child. Her voluntary shoulder subluxation and reduction did not reproduce or worsen her pain. Results from her physical examination and radiographs were normal. Magnetic resonance imaging showed edema in the subscapularis muscle consistent with acute muscle strain. She was treated with 6 weeks of rest, ice, and anti-inflammatory medication as needed. She returned to baseball and hitting during the following 6 weeks with no limitations.
PMCID: PMC3445160  PMID: 23016019
rotator cuff; baseball; muscle strain; adolescent; subscapularis
24.  Perk Station – Percutaneous Surgery Training and Performance Measurement Platform 
Image-guided percutaneous (through the skin) needle-based surgery has become part of routine clinical practice in performing procedures such as biopsies, injections and therapeutic implants. A novice physician typically performs needle interventions under the supervision of a senior physician; a slow and inherently subjective training process that lacks objective, quantitative assessment of the surgical skill and performance[S1]. Shortening the learning curve and increasing procedural consistency are important factors in assuring high-quality medical care.
This paper describes a laboratory validation system, called Perk Station, for standardized training and performance measurement under different assistance techniques for needle-based surgical guidance systems. The initial goal of the Perk Station is to assess and compare different techniques: 2D image overlay, biplane laser guide, laser protractor and conventional freehand. The main focus of this manuscript is the planning and guidance software system developed on the 3D Slicer platform, a free, open source software package designed for visualization and analysis of medical image data.
The prototype Perk Station has been successfully developed, the associated needle insertion phantoms were built, and the graphical user interface was fully implemented. The system was inaugurated in undergraduate teaching and a wide array of outreach activities. Initial results, experiences, ongoing activities and future plans are reported.
PMCID: PMC2817987  PMID: 19539446
Image Guidance; Needle Placement; Augmented Reality; Surgical Training
25.  Minimally invasive percutaneous transpedicular screw fixation: increased accuracy and reduced radiation exposure by means of a novel electromagnetic navigation system 
Acta Neurochirurgica  2010;153(3):589-596.
Minimally invasive percutaneous pedicle screw instrumentation methods may increase the need for intraoperative fluoroscopy, resulting in excessive radiation exposure for the patient, surgeon, and support staff. Electromagnetic field (EMF)-based navigation may aid more accurate placement of percutaneous pedicle screws while reducing fluoroscopic exposure. We compared the accuracy, time of insertion, and radiation exposure of EMF with traditional fluoroscopic percutaneous pedicle screw placement.
Minimally invasive pedicle screw placement in T8 to S1 pedicles of eight fresh-frozen human cadaveric torsos was guided with EMF or standard fluoroscopy. Set-up, insertion, and fluoroscopic times and radiation exposure and accuracy (measured with post-procedural computed tomography) were analyzed in each group.
Sixty-two pedicle screws were placed under fluoroscopic guidance and 60 under EMF guidance. Ideal trajectories were achieved more frequently with EMF over all segments (62.7% vs. 40%; p = 0.01). Greatest EMF accuracy was achieved in the lumbar spine, with significant improvements in both ideal trajectory and reduction of pedicle breaches over fluoroscopically guided placement (64.9% vs. 40%, p = 0.03, and 16.2% vs. 42.5%, p = 0.01, respectively). Fluoroscopy time was reduced 77% with the use of EMF (22 s vs. 5 s per level; p < 0.0001) over all spinal segments. Radiation exposure at the hand and body was reduced 60% (p = 0.058) and 32% (p = 0.073), respectively. Time for insertion did not vary between the two techniques.
Minimally invasive pedicle screw placement with the aid of EMF image guidance reduces fluoroscopy time and increases placement accuracy when compared with traditional fluoroscopic guidance while adding no additional time to the procedure.
PMCID: PMC3040822  PMID: 21153669
Minimally invasive; Electromagnetic field navigation; Pedicle screw; Fluoroscopy; Accuracy

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