Objective: Rheumatoid arthritis (RA) and psoriatic arthritis (PsA) commonly affect the small joints of the wrist and hand. We evaluated the performance of a new, high resolution extremity positron emission tomography (PET)/CT scanner for characterizing and quantifying pathologies associated with the two arthritides in the wrist and hand joints.Methods: Patients with RA or PsA underwent fluorine-18 fludeoxyglucose (F-18-FDG) PET/CT wrist and hand imaging, respectively, on the high-resolution scanner, Calibrated CT images and co-registered PET images were reconstructed. PET/CT was derived for the radiocarpal and pisiform-triquetral compartments, joints with erosive changes, sites of synovitis or tenosynovitis and the nail bed and were correlated with clinical and MRI findings,Results: Significantly elevated F-18-FDG uptake was measured for the radiocarpal and pisiform-triquetral compartments and at sites of bone erosion, synovitis, pannus and oedema, compared with unaffected joints (p < 0.05) in patients with RA, consistent with their clinical findings. In patients with PsA, significantly elevated F-18-FDG uptake was measured for joints with synovitis compared with unaffected joints (p < 0,05), with patterns of F-18-FDG uptake along the tendons, at the enthesis and in the nail bed, consistent with tenosynovitis, enthesitis and nail dystrophy, respectively.Conclusion: High-resolution F-18-FDG PET/CT imaging of the wrist and hand is feasible in an RA or PsA patient cohort and is capable of providing quantifiable measures of disease activity (synovitis, enthesitis, oedema and bone destruction).Advances in knowledge: High-resolution PET/CT imaging shows promise as a tool for understanding the pathogenesis of the arthritic process and for noninvasive, objective assessment of RA or PsA severity and therapy selection.

We present the case of a rupture of the brachialis muscle in a 17-year-old male. We provide an overview of the current literature discussing previously reported cases, the clinical features, and recommended treatment. The anatomy and function of the brachialis muscle and possible mechanism of injury are also discussed.

Multicentric reticulohistiocytosis (MRH) is a rare systemic inflammatory granulomatous disease that primarily manifests clinically with severe erosive arthritis and widespread papulonodular skin lesions but can involve multiple other organ systems. Despite the fact that this condition can become aggressive, debilitating as well as deforming with significant detrimental consequences, the etiology of this disease remains poorly understood. Moreover, the fact that MRH is such an uncommon disease has created an obstacle in the path of adequate clinical trials that are needed for better understanding of this phenomenon and for the development of treatment options for this patient population. In this review, we will attempt to discuss the epidemiology, pathophysiology, clinical features, associated conditions, differential diagnoses, diagnostic workup, and available treatments of MRH with the hope of creating a better understanding of this very challenging yet elusive disease process.

RATIONALE AND OBJECTIVES:At the authors' institutions, faculty members and trainees work at multiple sites scattered miles apart, making it difficult to physically attend weekly teaching conferences. As a possible solution, a weekly online musculoskeletal teaching conference was undertaken. This quickly grew to include multiple other sites around North America. The authors share their experiences to assist other radiologists in organizing similar educational conferences.MATERIALS AND METHODS:The conferences are run using the Citrix GoToMeeting online meeting system. It runs on multiple platforms, including Mac, PC, iPhone, iPad, and Android. Attendees use a wide variety of microphones, sound cards, powered speakers, and webcams. Most users have fast institutional Internet connections, though several attend via slower connections, such as 3G.RESULTS:The conference has run successfully for 2 years, with participants logging in from 24 different sites in 18 states, two Canadian provinces, and three countries. About 48 sessions are held each year, with 10 to 15 sites joining the conferences each week and about 10 to 15 cases seen each week. Most attendees are from university medical centers, though several private practice radiologists attend regularly. Screen-sharing quality is superb, with no discernible difference between local and remote slide quality. Audio quality is usually quite good, particularly for those using computer audio. Audio feedback is an occasional problem, but this issue is now more easily addressed. No single time is equally convenient for participants scattered among four to six time zones. However, some sites find the conferences sufficiently valuable to rearrange their afternoon procedure schedules to reduce conflicts with the conferences. The social aspect of visiting weekly with friends and colleagues from afar is highly valued, as are seeing the wide range of pathology from other institutions and the ability to confer with colleagues on difficult cases. The conferences have also spawned several collaborative educational projects, such as an online journal club, a published book of conference cases, and an online musculoskeletal hardware atlas.CONCLUSIONS:The weekly online musculoskeletal conference described in this report has matured over 2 years from a peculiar experiment to a very popular conference. Cases not seen locally provide enrichment, and attendees gain educational opportunities not otherwise available. Other radiology groups should be able to create and maintain similar conferences.

Eur J Nucl Med Mol Imaging (2010) 37:1047 DOI 10.1007/s00259-009-1364-x IMAGE OF THE MONTH High-resolution 18 F-FDG PET with MRI for monitoring response to treatment in rheumatoid arthritis Abhijit J. Chaudhari & Spencer L. Bowen & George W. Burkett & Nathan J. Packard & Felipe Godinez & Anand A. Joshi & Stanley M. Naguwa & David K. Shelton & John C. Hunter & John M. Boone & Michael H. Buonocore & Ramsey D. Badawi Received: 20 November 2009 / Accepted: 10 December 2009 / Published online: 30 January 2010 # The Author(s) 2010. This article is published with open access at Springerlink.com Molecular imaging can potentially provide means for mon- itoring response to therapy in rheumatoid arthritis (RA) early in the course of disease [1].Quantitative measurements of RA disease activity made in the wrist by whole-body PET scanners, however, have inadequate accuracy because of limited spatial resolution [2]. A high-resolution PET/CT scanner for imaging extremities has been built at our insti- tution [3]. In conjunction with a clinical MRI scanner, high- resolution PET/MR images can be obtained for the wrist. The CT image is used for PET/MR image coregistration. A 57-year-old female with established RA was stable until a recent clinical flare-up in the right wrist. Clinical exami- nation revealed synovitis, swelling, and diminished range of motion. The patient also had a history of osteoarthritis (OA). An extremity 18 F-FDG PET/CT scan immediately following MRI at baseline was performed on this patient. Tumor necrosis factor alpha (TNF-α) inhibitor (etanercept) therapy was then initiated as a part of the patient’s standard of care. The patient was re-scanned 5 weeks after starting treatment. The figure shows high-resolution 18 F-FDG PET images (pseudocolor) overlaid on pre-contrast MRI images (gray This work was funded by the NIH grants UL1-RR024146, R01CA129561, R01EB002138 and the UC Davis Imaging Research Center. A. J. Chaudhari (*) : S. L. Bowen : G. W. Burkett : N. J. Packard : F. Godinez : D. K. Shelton : J. C. Hunter : J. M. Boone : M. H. Buonocore : R. D. Badawi Department of Radiology, UC Davis Medical Center, Sacramento, CA, USA e-mail: ajchaudhari@ucdavis.edu A. A. Joshi Department of Neurology, UCLA School of Medicine, Los Angeles, CA, USA S. M. Naguwa Department of Internal Medicine, UC Davis Medical Center, Sacramento, CA, USA scale) at baseline (left column) and 5 weeks (right column). Significant reduction in PET signal (suggesting reduced inflammation) in the synovium and at sites of erosions (white arrows) is visible. The green arrow shows inflammation due to OA. Physician examination at 3 months confirmed that this patient responded positively to etanercept. This case illustrates the potential of high-resolution PET with MRI for quantitative visualization of early response to therapy in RA. Open Access This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which per- mits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. References 1. Brenner W. 18F-FDG PET in rheumatoid arthritis: there still is a long way to go. J Nucl Med. 2004;45(6):927–9. 2. Beckers C, Ribbens C, Andre B, Marcelis S, Kaye O, Mathy L, et al. Assessment of disease activity in rheumatoid arthritis with (18)F-FDG PET. J Nucl Med. 2004;45(6):956–64. 3. Bowen SL, Wu Y, Chaudhari AJ, Fu L, Packard NJ, Burkett GW, et al. Initial characterization of a dedicated breast PET/CT scanner during human imaging. J Nucl Med. 2009;50(9):1401–8.

BACKGROUND:Numerous structural deformities of the acetabulum are associated with hip osteoarthritis (OA). Acetabular retroversion has been implicated in the development of femoroacetabular impingement. However, it is unknown if retroversion occurs from isolated excessive bone in the superior acetabulum or a torsional phenomenon of the entire pelvic segment.QUESTIONS/PURPOSES:A method was developed to measure acetabular version (AV) using 3-D models thus eliminating positional factors. This method was used to determine if acetabular retroversion is an isolated entity or an effect involving the entire pelvic segment containing the acetabulum.METHOD:Fifty pelvic CT scans were selected from a large database. Measurements were performed for abduction, ischial spine position, and AV at multiple levels. The relationships between anteversion at multiple levels and between midacetabular anteversion and ischial spine position were analyzed.RESULTS:The mean upper and midlevel acetabular anteversion values were 14.4° ± 10.5° and 21.3° ± 5.8°, respectively. The mean abduction was 39.7° ± 4.3°. The prevalence of acetabular retroversion was 7%. Females had greater anteversion than males at all levels. Correlations were found between Levels 1 and 4 version (r = 0.74) and the ischial spine index and Level 4 version (r = 0.67).CONCLUSIONS:These data suggest retroversion involves the acetabulum at all levels and includes the entire pelvic segment containing the acetabulum and the ischial spine.CLINICAL RELEVANCE:These data are relevant for surgeons in providing targets for normal positioning of the acetabulum during periacetabular osteotomies and acetabular recontouring procedures.

The authors report a case of a 19-year-old man with a Segond fracture with knee effusion after an acute injury, in addition to findings of prior anterior cruciate ligament (ACL) reconstruction. This case illustrates the predictive nature of Segond fracture for further acute meniscoligamentous injury, even after previous ACL reconstruction.

Rheumatoid arthritis (RA) is a debilitating inflammatory disease which results in 9 million physician visits and 250,000 hospitalizations per year. New molecularly-targeted pharmaceuticals are available to treat this disease, but clinical examination and conventional imaging do not accurately distinguish long-term responders from non-responders to these expensive therapies. We hypothesize that longitudinal information gained from high resolution MRI, CT and PET imaging of wrists of RA patients receiving therapy will be synergistic and thus, in combination will lead to the development of new imaging metrics that will help clinicians match clinical response with active joint disease. These metrics could potentially be used to separate responders to therapy from non-responders at early time points in the course of the disease. To test this hypothesis, we aim to use a unique high resolution extremity PET/CT scanner built by UC Davis researchers and a knee coil in a 1.5T MRI wholebody scanner. A multimodality wrist restraint system (WRS) has been designed and fabricated, and is used to immobilize the wrist during and between scans. Phantom experiments have been carried out for the scanners in the presence of the WRS. No apparent image degradation due to the WRS was observed. Images from the three modalities have been rigidly registered using a fiducial marker-based approach. A repositioning study was carried out in healthy volunteers using the MRI scanner. Results from this study examining repositioning error in wrist bones look promising. Instrumentation development has been completed and proof-of-principle scans have been carried out. A clinical trial in 10 patients for monitoring response in RA has been approved by IRB and recruiting has begun in early November.

A 62-year-old woman with severe seizure disorder presented with right ankle and foot pain after being found down, presumably following a seizure recurrence. Imaging showed an acute comminuted fracture of the anterolateral aspect of the right calcaneus, as well as an acute avulsion fracture of the right navicular tuberosity at the site of insertion of the tibialis posterior tendon. This fracture pattern suggests forced abduction of the midfoot or forefoot with severe compression of the lateral column and failure of the medial column under tension, an entity that has previously been described as the nutcracker fracture. This mechanism of injury should prompt particularly careful evaluation of the navicular, cuboid, and calcaneus for any signs of injury. Subtle fractures of the navicular and calcaneus may be overlooked in the emergency setting, leading to a delay in surgical treatment and ultimately chronic foot deformities that can result in significant functional disability.

712 Objectives: 3D anatomical (CT and MRI) and functional (PET and DCE-MRI) imaging of the wrist would be highly desirable for probing response to therapy in Rheumatoid Arthritis (RA), since changes in imaging metrics, e.g. synovial thickness, FDG-SUV, contrast, erosion, etc, can be monitored over time and in turn may be linked to the clinical status of the disease [1,2]. The aim of this study was to design and fabricate an ergonomic wrist restraint system (WRS) compatible with a MRI scanner and the UC Davis dedicated high resolution extremity PET/CT scanner. This setup is expected to yield better anatomical correlation between images from the two scanners. Methods: The WRS consisted of a styrofoam base on which the forearm could be rested in either the prone or supine position. A thermoplastic sheet was used to create a mask for the wrist. The mask was appropriately locked in position on the base by means of nylon bolts. A plastic frame for MRI and a center stage for PET/CT supported the WRS to lie along the central axes of the scanners. Results: The multimodality WRS was designed and fabricated. Studies determining the accuracy of repositioning are being conducted. A proposal for conducting patient scans is funded and has been submitted to the IRB. Conclusions: Coregistered high resolution anatomical and functional data to be acquired using the proposed setup should facilitate the investigation of indicators of positive or negative response to therapy in RA. Research Support: NIH-NCRR UL1 RR024146 UC Davis Clinical and Translational Sciences Center Pilot Award, the UC Davis Imaging Research Center and the Rusch Fund for Nuclear Medicine.

Introduction: Traditional advanced imaging modalities such as CT and MRI are limited in their ability to perform accurate linear distance and angular measurements regardless of anatomical orientation. The construction of 3D models has been used to perform anthropometric analyses as well as in the reconstruction of rapid prototypes. We hypothesized that such measurements would be precise to within 2 mm or 2° of measurements performed with a coordinate measurement machine (CMM). We also hypothesized that there would be a high degree of interobserver reliability with these measurements. Materials and Methods: Multiple aluminum screws were implanted in various positions in three foam pelvises which were subsequently scanned by CT and rendered as 3D models using a commercially available software package (Mimics). Linear and angular measurements were performed using a CMM machine, the software package, and a dial caliper or goniometer. The deviation of the measurements from the CMM data was compared using ANOVA. The interobserver reliability of both the manual and computer-generated measurements was calculated. Results: The mean difference between the CMM distances and those measured manually and with the software was 2.12 ± 1.20 mm and 1.57 ± 1.05 mm, respectively. The mean difference between the CMM angular measurements and the angular measurements performed manually and with the software was 4.07 ± 4.70° and 1.62 ± 1.32°, respectively. In all cases, the manual measurements were significantly less accurate (p < 0.0001) and there was a high degree of interobserver reliability. Conclusions: Computer-generated measurements taken from three-dimensionally reconstructed models are more accurate than manual measurements and are within 2 mm and 2° of measurements performed with a CMM. These measurements have high interobserver reliability.

OBJECTIVE:This study was designed to test our hypothesis that football players with shoulder pain, shoulder instability, or both requiring MR arthrography for evaluation are at an increased likelihood relative to non-football players for having a tear of the posterior glenoid labrum.CONCLUSION:We conclude that posterior glenoid labrum tears are more prevalent in football players than in non-football players.

We describe a case of a spinal fusion site infection, which was first suggested on plain radiographs due to interval displacement and partial dissolution of the bone graft material. These radiographic findings occurred 4 weeks before the infection became clinically evident. Cultures taken during eventual surgical debridement grew Aspergillus fumigatus. This case emphasizes the importance of noting changes in bone graft material in addition to the routine evaluation of alignment and hardware in patients who have undergone posterior spinal fusion.

A 21-year-old man presented with ankle pain after a motor vehicle accident. Imaging revealed an acute fracture of the os trigonum in addition to multiple, other lower-extremity fractures. In this case, the fracture of the os trigonum was a result of a significant traumatic injury. Thus, the presence of this fracture in an acute setting should prompt a search for other associated fractures.