7T for clinical imaging of benign peripheral nerve tumors: preliminary results

PURPOSE

MRI has become an essential diagnostic imaging modality for peripheral nerve pathology. Early MR imaging for peripheral nerve depended on inferred nerve involvement by visualizing downstream effects such as denervation muscular atrophy; improvements in MRI technology have made possible direct visualization of the nerves. In this paper, we share our early clinical experience with 7T for benign neurogenic tumors.

MATERIALS

Patients with benign neurogenic tumors and 7T MRI examinations available were reviewed. Cases of individual benign peripheral nerve tumors were included to demonstrate 7T MRI imaging characteristics. All exams were performed on a 7T MRI MAGNETOM Terra using a 28-channel receive, single-channel transmit knee coil.

RESULTS

Five cases of four pathologies were selected from 38 patients to depict characteristic imaging features in different benign nerve tumors and lesions using 7T MRI.

CONCLUSION

The primary advantage of 7T over 3T is an increase in signal-to-noise ratio which allows higher in plane resolution so that the smallest neural structures can be seen and characterized. This improvement in MR imaging provides the opportunity for more accurate diagnosis and surgical planning in selected cases. As this technology continues to evolve for clinical purposes, we anticipate increasing applications and improved patient care using 7T MRI for the diagnosis of peripheral nerve masses.

ACR Appropriateness Criteria® Imaging After Total Knee Arthroplasty: 2023 Update

Total knee arthroplasty is the most commonly performed joint replacement procedure in the United States. This manuscript will discuss the recommended imaging modalities for six clinical variants; 1. follow-up of symptomatic or asymptomatic patients with a total knee arthroplasty. Initial imaging, 2. Suspected infection after total knee arthroplasty. Additional imaging following radiographs, 3. Pain after total knee arthroplasty. Infection excluded. Suspect aseptic loosening or osteolysis or instability. Additional imaging following radiographs, 4. Pain after total knee arthroplasty. Suspect periprosthetic or hardware fracture. Additional imaging following radiographs, 5. Pain after total knee arthroplasty. Measuring component rotation. Additional imaging following radiographs, and 6. Pain after total knee arthroplasty. Suspect periprosthetic soft-tissue abnormality unrelated to infection, including quadriceps or patellar tendinopathy. Additional imaging following radiographs. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

ACR Appropriateness Criteria® Imaging After Total Hip Arthroplasty

This article reviews evidence for performing various imaging studies in patients with total hip prostheses. Routine follow-up is generally performed with radiography. Radiographs are also usually the initial imaging modality for patients with symptoms related to the prosthesis. Following acute injury with pain, noncontrast CT may add information to radiographic examination regarding the presence and location of a fracture, component stability, and bone stock. Image-guided joint aspiration, noncontrast MRI, and white blood cell scan and sulfur colloid scan of the hip, are usually appropriate studies for patients suspected of having periprosthetic infection. For evaluation of component loosening, wear, and/or osteolysis, noncontrast CT or MRI are usually appropriate studies. Noncontrast MRI is usually appropriate for identifying adverse reaction to metal debris related to metal-on-metal articulations. For assessing patients after hip arthroplasty, who have trochanteric pain and nondiagnostic radiographs, ultrasound, or MRI are usually appropriate studies. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Radiotherapy vs. Cystectomy for Treatment of Muscle Invasive Bladder Cancer in Very Elderly Patients

PURPOSE/OBJECTIVE(S)

Radical cystectomy (RC) has long remained the principal treatment of muscle invasive bladder cancer (MIBC). It is, however, associated with significant morbidity, long recovery, and reported worse overall and cancer specific survival, particularly for the very elderly (age > = 80). Bladder preservation with transurethral resection of bladder tumor (TURBT) followed by radiotherapy (RT) +/- concurrent chemotherapy (ChT) is regarded as a curative-intent alternative to RC in well-selected patients. The optimal treatment strategy remains unclear in very elderly patients. We hypothesize that outcomes following RT vs RC are clinically equivalent for treatment of MIBC in very elderly patients.

MATERIALS/METHODS

Patients > = 80 years old with T2-T4 N0-N1 bladder cancer treated definitively with RT versus RC were included. Exclusion criteria included history of pelvic RT, prior cystectomy, or palliative treatment intent. Clinicopathologic and treatment-related details, as well as clinical outcomes and toxicities were retrospectively abstracted. Kaplan-Meier analyses were performed.

RESULTS

At a median follow-up of 17 months (range 0.25-190), 47 patients received RT vs 83 patients who underwent RC with median age of 86 years (80-97) vs 83 years (range 80-91) (p<0.01), respectively. Median Charlson Comorbidity Index was similar between groups (p = 0.35) with median 7 for both cohorts, predicting 0% estimated 10y survival. Most patients had cT2 tumors (91% vs 99%, p = 0.06), cN0 nodal status (96% vs 100%, p = 0.06), and urothelial carcinoma histology (79% vs 90%, p = 0.22). Most RT patients received concurrent ChT (90%) and a minority of RC patients received neoadjuvant ChT (16%). 70% of RT pts had complete TURBTs prior to RT. Common RT regimens were 50-55 Gy in 20-25 fractions or 60-64.8 Gy in 30-36 fractions, using IMRT (89%) or 3D conformal (11%) technique. Overall survival for RT vs RC at 1- and 2- years was 79% vs 85% and 57% and 69%, respectively (p = 0.20). Locoregional control at 1- and 2-years was 73% vs 70% and 63% vs 66% (p = 0.59), respectively. Progression free survival at 1- and 2-years was 69% vs 66% and 52% vs 54% (p = 0.75), respectively. No RT patients went on to receive salvage cystectomy. Treatment complications are listed in Table 1; the Clavien Dindo classification system was used to describe acute surgical complications of RC and the Common Terminology Criteria for Adverse Events (CTCAE) Dictionary v5.0 was used for acute and late toxicity of RT.

CONCLUSION

In the very elderly, RT (with or without concurrent ChT) offers survival and locoregional control rates comparable to RC, with a favorable side effect profile. RT should be offered for definitive management of non-metastatic MIBC as an alternative to RC in selected, well- informed, and compliant very elderly patients.

Delayed cognitive impairments in a rat model of Gulf War Illness are stimulus-dependent

Gulf War Illness (GWI) collectively describes the multitude of central and peripheral disturbances affecting soldiers who served in the 1990-1991 Gulf War. While the mechanisms responsible for GWI remain elusive, the prophylactic use of the reversible acetylcholinesterase inhibitor, pyridostigmine bromide (PB), and war-related stress have been identified as chief factors in GWI pathology. Post-deployment stress is a common challenge faced by veterans, and aberrant cholinergic and/or immune responses to these psychological stressors may play an important role in GWI pathology, especially the cognitive impairments experienced by many GWI patients. Therefore, the current study investigated if an immobilization stress challenge would produce abnormal responses in PB-treated rats three months later. Results indicate that hippocampal cholinergic responses to an immobilization stress challenge are impaired three months after PB administration. We also assessed if an immune or stress challenge reveals deficits in PB-treated animals during hippocampal-dependent learning and memory tasks at this delayed timepoint. Novel object recognition (NOR) testing paired with either acute saline or lipopolysaccharide (LPS, 30 µg/kg, i.p.), as well as Morris water maze (MWM) testing was conducted approximately three months after PB administration and/or repeated restraint stress. Rats with a history of PB treatment exhibited 24-hour hippocampal-dependent memory deficits when challenged with LPS, but not saline, in the NOR task. Similarly, in the same cohort, PB-treated rats showed 24-hour memory deficits in the MWM task. Ultimately, these studies highlight the long-term effects of PB treatment on hippocampal function and provide insight into the progressive cognitive deficits observed in veterans with GWI.

Incidence of complications related to shoulder arthroplasties identified on computed tomography

PURPOSE

Determine incidence of shoulder arthroplasty complications identified on computed tomography (CT).

MATERIALS AND METHODS

Retrospective institutional database review of patients with shoulder arthroplasties who underwent CT between 01/2006-11/2021 at a tertiary academic referral center with subspecialized orthopedic shoulder surgeons. CT reports were reviewed for arthroplasty type and complication. Data were stratified and summarized. Associations between complications and arthroplasty types were determined with Chi-squared goodness of fit test.

RESULTS

Eight hundred twelve CTs in 797 unique patients were included (438 (53.9%) females and 374 (46.1%) males; mean age 67 ± 11 years). There were 403 total shoulder arthroplasties (TSA), 317 reverse total shoulder arthroplasties (rTSA), and 92 hemiarthroplasties (HA). Complications were present in 527/812 (64.9%) and incidences were: loosening/aseptic osteolysis 36.9%, periprosthetic failure 21.6%, periprosthetic fracture 12.3%, periprosthetic dislocation 6.8%, joint/pseudocapsule effusion 5.9%, prosthetic failure 4.8%, infection 3.8%, and periprosthetic collection 2.1%. Complications per arthroplasty were: 305/403 (75.7%) TSAs, 176/317 (55.5%) rTSAs, and 46/92 (50%) HAs (p < 0.001). Periprosthetic fracture (20.8%), prosthetic dislocation (9.8%), and prosthetic failure (7.9%) were highest in rTSAs (p < 0.001, p < 0.013, p < 0.001, respectively). Loosening/aseptic osteolysis most frequent in TSAs (54.1%) (p < 0.001). Periprosthetic failure most frequent in HA (32.6%) (p < 0.001). Significant associations were identified with joint/pseudocapsule effusion and loosening/aseptic osteolysis (p = 0.04) and prosthetic dislocation (p < .001).

CONCLUSION

In this single tertiary academic referral center cohort, the incidence of shoulder arthroplasty complication identified on CT was 64.9% and the most commonly occurring complication was loosening/aseptic osteolysis (36.9%). TSA had the highest incidence of complication (75.7%).

Cognitive Development in Single-Suture Craniosynostosis - A Systematic Review

There is conflicting evidence whether single-suture craniosynostosis (SSC), is linked to adversities of cognitive development. To assess the evidence for a link between SSC and cognition, a systematic literature search was conducted and eligible studies assessed for inclusion by two independent readers. Forty-eight studies met inclusion criteria. Small to medium but persistent effects on both general and some specific cognitive functions across age bands were found in higher quality studies for SSC overall. There was limited evidence for effects related to surgical correction. Methodologies varied substantially and there was a lack of longitudinal studies using broad assessment batteries.

ACR Appropriateness Criteria® Chronic Hip Pain: 2022 Update

Chronic hip pain is a frequent chief complaint for adult patients who present for evaluation in a variety of clinical practice settings. Following a targeted history and physical examination, imaging plays a vital role in elucidating the etiologies of a patient's symptoms, as a wide spectrum of pathological entities may cause chronic hip pain. Radiography is usually the appropriate initial imaging test following a clinical examination. Depending on the clinical picture, advanced cross-sectional imaging may be subsequently performed for further evaluation. This documents provides best practice for the imaging workup of chronic hip pain in patients presenting with a variety of clinical scenarios. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

ACR Appropriateness Criteria® Chronic Extremity Joint Pain-Suspected Inflammatory Arthritis, Crystalline Arthritis, or Erosive Osteoarthritis: 2022 Update

Evaluation for suspected inflammatory arthritis as a cause for chronic extremity joint pain often relies on imaging. It is essential that imaging results are interpreted in the context of clinical and serologic results to add specificity because there is significant overlap of imaging findings among the various types of arthritis. This document provides recommendations for imaging evaluation of specific types of inflammatory arthritis, including rheumatoid arthritis, seronegative spondyloarthropathy, gout, calcium pyrophosphate dihydrate disease (or pseudogout), and erosive osteoarthritis. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

ACR Appropriateness Criteria® Chronic Shoulder Pain: 2022 Update

Chronic shoulder pain is an extremely common presenting complaint. Potential pain generators include the rotator cuff tendons, biceps tendon, labrum, glenohumeral articular cartilage, acromioclavicular joint, bones, suprascapular and axillary nerves, and the joint capsule/synovium. Radiographs are typically the initial imaging study obtained in patients with chronic shoulder pain. Further imaging may often be required, with modality chosen based on patient symptoms and physical examination findings, which may lead the clinician to suspect a specific pain generator. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

ACR Appropriateness Criteria® Osteoporosis and Bone Mineral Density: 2022 Update

Osteoporosis constitutes a significant public health risk. An estimated 10.2 million adults in the United States >50 years of age have osteoporosis, a systemic condition that weakens the bones increasing the susceptibility for fractures. Approximately one-half of women and nearly one-third of men >50 years of age will sustain an osteoporotic fracture. These fractures are associated with a decrease in quality of life, diminished physical function, and reduced independence. Dual-energy X-ray absorptiometry (DXA) is the primary imaging modality used to screen for osteoporosis in women >65 years of age and men >70 years of age. DXA may be used in patients <65 years of age to evaluate bone mass density if there are additional risk factors. In certain situations, vertebral fracture assessment and trabecular bone score may further predict fracture risk, particularly in patients who are not yet osteoporotic but are in the range of osteopenia. Quantitative CT is useful in patients with advanced degenerative changes in the spine. Given the proven efficacy of pharmacologic therapy, the role of imaging to appropriately identify and monitor high-risk individuals is critical in substantially reducing osteoporosis-associated morbidity and mortality, and reducing the considerable cost to the health care system. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Clinical and Radiological Safety of Retained Implantable Doppler Devices Used for Free Flap Monitoring

INTRODUCTION

Implantable Doppler devices are reliable adjuncts used for free flap monitoring. Occasionally, the probe/wire is not removed and remains in the soft tissues. The clinical safety of the retained probes and safety and compatibility with magnetic resonance imaging (MRI) have not been studied. We present a series of retained implantable Doppler probes examining clinic outcomes, safety and compatibility with MRI, and effect on MRI image quality.

METHODS

A retrospective review was conducted of patients who had an implantable Doppler device for free flap monitoring between July 2007 and August 2018. Routine post-operative imaging was reviewed for all patients to identify incidental findings of a retained probe. A subset of patients with retained implantable Doppler probes who underwent MRI was identified. Magnetic resonance images were reviewed to detect any degradation of image quality.

RESULTS

A total of 323 patients who had an implantable Doppler device placed were reviewed 18 (5.6%) patients were identified with a retained probe and were included in this study. Mean age was 49 years with mean follow-up of 34.4 months. One potential device-related complication occurred in 1 (5.6%) patient. A total of 32 MRI scans were performed in 8 patients with retained devices, including 6 patients who underwent a total of 21 MRIs of the surgical site. There were no complications related to the MRI scans, and we found no significant degradation of image quality.

CONCLUSION

Retained implantable Doppler probes were not associated with substantial adverse clinical outcomes nor affected MRI image quality of the surgical site.

High-resolution MRI of a peroneal intraneural ganglion cyst arising from the knee joint: illustrative case

BACKGROUND

The advancement of high-resolution imaging and increased clinical experience have led to an increased understanding of the formation and treatment of intraneural ganglion cysts. Nearly all intraneural ganglion cysts in the common peroneal nerve have been reported to arise from a joint connection to the superior tibiofibular joint. The authors have identified four cases of intraneural ganglion cysts arising from the knee joint itself; however, none of these reported cases were well described, documented, or illustrated with high-resolution imaging.

OBSERVATIONS

Here the authors present the case of an intraneural ganglion cyst arising from the knee joint and causing intermittent weakness and pain. The articular branch to the knee joint was clearly demonstrated on high-resolution magnetic resonance imaging and confirmed at surgical exploration. The patient was treated with articular branch ligation and has had complete resolution of his symptoms without recurrence of the cyst on follow-up imaging.

LESSONS

This case adds to the mounting evidence that intraneural cyst pathology is dependent on a connection to a synovial joint as stated in the unifying theory of intraneural cyst development.

Tuberculosis in a Spanish cohort of children living with HIV: the CHOTIS study (Childhood HIV & TB study)

BACKGROUND: Tuberculosis (TB) is the leading opportunistic infection in children with human immunodeficiency virus (HIV), but is uncommon in low prevalence regions. We aim to describe the changing epidemiology and clinical presentation of TB-HIV co-infection in a cohort of HIV-infected children in Spain.METHODS: Children diagnosed with TB between 1995 and 2016 in the paediatric HIV cohort were identified. The incidence and clinical presentation were compared in three periods: 1995-1999 (P1, before initiation of combined antiretroviral therapy, cART), 2000-2009 (P2, increase in immigration), and 2010-2016 (P3, decrease in immigration).RESULTS: We included 29 TB cases among 1183 children aged <18 years (2.4%, 243/100 000 person-years). The proportion was stable in P1 and P2 (1.3%), but decreased in P3 (0.8%). The median age at TB diagnosis was 6.4 years (IQR 4-10.6); most children in P3 were aged >10 years (20% vs. 23.1% vs. 83.3%, P = 0.01). TB was diagnosed at HIV presentation in 11/29 children (37.9%). Foreign-born children accounted for respectively 0%, 8% and 67% of the total number of children in each period (P ≤ 0.0001). One third had extrapulmonary TB; four children died (13.8%).CONCLUSION: In our cohort, the incidence of TB-HIV co-infection decreased with decline in immigration. In regions with adequate cART coverage and low TB transmission, paediatric TB-HIV coinfection is uncommon, but associated with significant morbidity. Strategies for TB surveillance, diagnosis and treatment in this vulnerable population should be reinforced.

Understanding the Implications of the Meniscal Ossicle: Patient Presentation, Treatment, and Outcomes

The meniscal ossicle is observed in clinical practice, yet there currently is limited information on its potential clinical significance. The purpose of this study was to assess the clinical presentation, imaging findings, and clinical treatment and outcomes of a series of patients identified as having a meniscal ossicle. An institutional database was reviewed to identify knees with a meniscal ossicle. Clinical presentation, magnetic resonance imaging (MRI), treatment, and outcomes were analyzed. Radiographs were graded using Kellgren-Lawrence (KL) scores. MRIs were reviewed for the presence and location of meniscal ossicles and additional knee pathology. Knee arthroplasty rates were recorded with the remaining patients contacted to obtain final International Knee Documentation Committee (IKDC) and Tegner's scores. Failure was defined as conversion to arthroplasty or failing IKDC score (< 75.4). Forty-five meniscal ossicles in 45 patients (26 males and 19 females) with a mean age of 51 years (standard deviation [SD] = 19.0) were included. Pain was the most common presenting symptom (89%). Forty-two patients (93%) had an associated meniscus root tear on MRI. Eighteen percent of patients that did not have an ossicle on initial imaging subsequently developed an ossicle. Mean KL grades progressed significantly from baseline of 1.84 (SD = 1.0) to 2.55 (SD = 0.93 p < 0.01) on final follow-up. Thirty-nine percent of baseline radiographs showed KL grades of less than 2 compared with only 15% of follow-up radiographs (p = 0.04). Mean IKDC score obtained for patients ≤ 60 at an average follow-up of 3.1 years (SD = 3.2) was 65.2 (SD = 19.0). Eight out of 45 patients (18%) had progressed to total knee arthroplasty (TKA) by latest available follow-up. Sixty-two percent of patients met failure criteria at latest available follow-up. The meniscal ossicle is most commonly found in the posterior horn or root of the medial meniscus and is highly suggestive to be sequelae of a posterior root tear. Therefore, the presence of a meniscal ossicle should alert the orthopaedic surgeon to the high likelihood of the patient having a meniscus root tear. These patients have shown to have poor clinical outcomes and worsening arthritis.

7T MR Thermometry technique for validation of system-predicted SAR with a home-built radiofrequency wrist coil

PURPOSE

A 7T magnetic resonance thermometry (MRT) technique was developed to validate the conversion factor between the system-measured transmitted radiofrequency (RF) power into a home-built RF wrist coil with the system-predicted SAR value. The conversion factor for a new RF coil developed for ultra high magnetic field MRI systems is used to ensure that regulatory limits on RF energy deposition in tissue, specifically the local 10g-averaged specific absorption rate (SAR_10g ), are not exceeded. MRT can be used to validate this factor by ensuring that MRT-measured SAR values do not exceed those predicted by the system.

METHODS

A 14-cm diameter high-pass birdcage RF coil was built to image the wrist at 7T. A high spatial and temporal resolution dual-echo gradient echo MRT technique, incorporating quasi-simultaneous RF-induced heating and temperature change measurements using the proton resonance frequency method, was developed. The technique allowed for high-temperature resolution measurements (~±0.1°C) to be performed every 20 s over a 4-min heating period, with high spatial resolution (2.56 mm³ voxel size) and avoiding phase discontinuities arising from severe magnetic susceptibility-induced B₀ inhomogeneities. Magnetic resonance thermometry was performed on a phantom made from polyvinylpyrrolidone to mimic the dielectric properties of muscle tissue at 297.2 MHz. Temperature changes measured with MRT and four fiber optic temperature sensors embedded in the phantom were compared. Electromagnetic simulations of the coil and phantom were developed and validated via comparison of simulated and measured B₁ ⁺ maps in the phantom. The position of maximum SAR within the coil was determined from simulations, and MRT was performed within a wrist-sized piece of meat positioned at that SAR hotspot location. MRT-measured and system-predicted SAR values for the phantom and meat were compared.

RESULTS

Temperature change measurements from MRT matched closely to those from the fiber optic temperature sensors. The simulations were validated via close correlation between the simulated and MRT-measured B₁ ⁺ and SAR maps. Using a coil conversion factor of 2 kg^-1 , MRT-measured point-SAR values did not exceed the system-predicted SAR_10g in either the uniform phantom or in the piece of meat mimicking the wrist located at the SAR hotspot location.

CONCLUSIONS

A highly accurate MRT technique with high spatial and temporal resolution was developed. This technique can be used to ensure that system-predicted SAR values are not exceeded in practice, thereby providing independent validation of SAR levels delivered by a newly built RF wrist coil. The MRT technique is readily generalizable to perform safety evaluations for other RF coils at 7T.

MRI appearance of jogger's foot

OBJECTIVE

To characterize the MRI findings present in patients with clinically proven or suspected jogger's foot.

MATERIALS AND METHODS

Ten years of medical charts in patients clinically suspected of having jogger's foot and who had MRI studies completed were identified utilizing a computer database search. Six study cases were identified. The MRI examinations of the study cases and an age- and gender-matched control group were reviewed in a blinded fashion by two musculoskeletal radiologists. Size and signal intensity of the medial plantar nerve were measured and characterized. The medial foot musculature was assessed for acute or chronic denervation changes.

RESULTS

The medial plantar nerve was found to have moderately increased T2 signal compared with normal skeletal muscle in 3/6 study group cases and markedly increased T2 signal in the remaining 3/6 cases. In all control cases, the nerve was reported to have T2 signal equal or minimally higher than normal skeletal muscle. The mean total size of the medial plantar nerve was significantly larger in the study group when compared with that in the control group at all measured locations (p < 0.04).

CONCLUSIONS

Abnormal thickness and T2 hyperintensity of the medial plantar nerve centered at the master knot of Henry are characteristic MRI findings in patients with jogger's foot when compared with control subjects. Muscular denervation changes may also be seen, most commonly in the flexor hallucis brevis muscle.

Magnetic Resonance Safety in the 7T Environment

The arrival of 7T MR imaging into the clinic represents a significant step-change in MR technology. This article describes safety concerns associated with imaging at 7T, including the increased magnetic forces on magnetic objects at 7T and the interaction of the 300 MHz (Larmor) radiofrequency energy with tissue in the body. A dedicated multidisciplinary 7T Safety team should develop safety policies and procedures to address these safety challenges and keep abreast of best practice in the field. The off-label imaging of implanted devices is discussed, and also the need for staff training to deal with complexities of patient handling and image interpretation.

Quantitative Knee Arthrography in a Large Animal Model of Osteoarthritis Using Photon-Counting Detector CT

OBJECTIVE

The aim of this study was to grade cartilage damage in a swine model of osteoarthritis using a whole-body photon-counting detector (PCD) CT.

MATERIALS AND METHODS

A multienergy phantom containing gadolinium (Gd) (2, 4, 8, and 16 mg/mL) and hydroxyapatite (200 and 400 mg/cc) was scanned using a PCD-CT system (48 × 0.25 mm collimation, 80 kV, 800 mAs, D50 reconstruction kernel) to serve as calibration for material decomposition and to assess quantification accuracy. Osteoarthritis was induced in Yucatan miniswine (n = 8) using 1.2 mg monoiodoacetate (MIA) injected into a randomized knee, whereas the contralateral control knee received saline. Twenty-one days later, a contrast bolus (gadoterate meglumine, 4 mL/knee) was intra-articularly administered into both knees. The knees were simultaneously scanned on the PCD-CT system (48 × 0.25 mm collimation, 80 kV, 800 mAs). Multienergy images were reconstructed with a sharp "V71" kernel and a quantitative "D50" kernel. Image denoising was applied to the V71 images before grading cartilage damage, and an iterative material decomposition technique was applied to D50 images to generate the Gd maps. Two radiologists blinded to the knee injection status graded the cartilage integrity based on a modified International Cartilage Repair Society scoring system. Histology was performed on excised cartilage using methylene blue/basic fuchsin. Statistical analysis of grade distribution was performed using an exact test of omnibus symmetry with P < 0.05 considered significant.

RESULTS

Material decomposed images from the multienergy phantom scan showed delineation and quantification of Gd and hydroxyapatite with a root-mean-squared error of 0.3 mg/mL and 18.4 mg/cc, respectively. In the animal cohort, the radiologists reported chondromalacia in the MIA knees with International Cartilage Repair Society scores ranging from grade 1 (cartilage heterogeneity, n = 4 knees) to grade 3 (up to 100% cartilage loss, n = 4 knees). Grade 1 was characterized by cartilage heterogeneity and increased joint space in the patellofemoral compartment, whereas grade 3 was characterized by cartilage erosion and bone-on-bone articulation in the patellofemoral compartment. All control knees were scored as grade 0 (normal cartilage). Significant difference (P = 0.004) was observed in the grade distribution between the MIA and control knees. Gross examination of the excised knees showed cartilage lesions in the grade 3 MIA knees. The Gd maps from material decomposition showed lower contrast levels in the joint space of the MIA knee compared with the contralateral control knee due to joint effusion. Histology revealed chondrocyte loss in the MIA knee cartilage confirming the chondrotoxic effects of MIA on cartilage matrix.

CONCLUSIONS

We demonstrated a high-resolution and quantitative PCD-CT arthrography technique for grading cartilage damage in a large animal model of osteoarthritis. Photon-counting detector CT offers simultaneous high-resolution and multienergy imaging capabilities that allowed morphological assessment of cartilage loss and quantification of contrast levels in the joint as a marker of joint disease. Cartilage damage in the MIA knees was graded using PCD-CT images, and the image-based findings were further confirmed using histology and gross examination of the excised knees.

MR imaging of the postsurgical cubital tunnel: an imaging review of the cubital tunnel, cubital tunnel syndrome, and associated surgical techniques

Ulnar nerve compression at the elbow, specifically the cubital tunnel, is the second most common upper extremity compression neuropathy. Many patients presenting with compression symptoms will subsequently undergo surgical intervention. We review the open surgical treatment of cubital tunnel syndrome and review the expected postoperative imaging appearance of those treatments on magnetic resonance imaging (MR), including: simple or in situ decompression, medial epicondylectomy, and anterior transposition, including subcutaneous, intramuscular, and submuscular variants. We discuss the relevant anatomy of the presurgical cubital tunnel and common sites and causes of ulnar nerve compression at and about the cubital tunnel. The imaging appearance of the preoperative and postoperative ulnar nerve and postoperative complications are reviewed.

Imaging for Acute and Chronic Scaphoid Fractures

The scaphoid is the most commonly fractured bone in the wrist but 20% to 40% of scaphoid fractures are radiographically occult. Delayed or misdiagnosis can have significant consequences with late complications such as nonunion, malunion, or the development of avascular necrosis in the proximal pole. After initial negative radiographs, advanced cross-sectional imaging, including CT and MRI, ultimately may provide more accurate and rapid diagnosis than conventional radiography. With chronic fractures, the preferred modality depends on the clinical question. New techniques are evolving that will further advance imaging for diagnosis and treatment of scaphoid fractures.

Uniform combined reconstruction of multichannel 7T knee MRI receive coil data without the use of a reference scan

BACKGROUND

MR image intensity nonuniformity is often observed at 7T. Reference scans from the body coil used for uniformity correction at lower field strengths are typically not available at 7T.

PURPOSE

To evaluate the efficacy of a novel algorithm, Uniform Combined Reconstruction (UNICORN), to correct receive coil-induced nonuniformity in musculoskeletal 7T MRI without the use of a reference scan.

STUDY TYPE

Retrospective image analysis study.

SUBJECTS

MRI data of 20 subjects was retrospectively processed offline. Field Strength/Sequence: Knees of 20 subjects were imaged at 7T with a single-channel transmit, 28-channel phased-array receive knee coil. A turbo-spin-echo sequence was used to acquire 33 series of images.

ASSESSMENT

Three fellowship-trained musculoskeletal radiologists with cumulative experience of 42 years reviewed the images. The uniformity, contrast, signal-to-noise ratio (SNR), and overall image quality were evaluated for images with no postprocessing, images processed with N4 bias field correction algorithm, and the UNICORN algorithm.

STATISTICAL TESTS

Intraclass correlation coefficient (ICC) was used for measuring the interrater reliability. ICC and 95% confidence intervals (CIs) were calculated using the R statistical package employing a two-way mixed-effects model based on a mean rating (k = 3) for absolute agreement. The Wilcoxon signed-rank test with continuity correction was used for analyzing the overall image quality scores.

RESULTS

UNICORN was preferred among the three methods evaluated for uniformity in 97.9% of the pooled ratings, with excellent interrater agreement (ICC of 0.98, CI 0.97-0.99). UNICORN was also rated better than N4 for contrast and equivalent to N4 in SNR with ICCs of 0.80 (CI 0.72-0.86) and 0.67 (CI 0.54-0.77), respectively. The overall image quality scores for UNICORN were significantly higher than N4 (P < 6 × 10^-13 ), with good to excellent interrater agreement (ICC 0.90, CI 0.86-0.93).

DATA CONCLUSION

Without the use of a reference scan, UNICORN provides better image uniformity, contrast, and overall image quality at 7T compared with the N4 bias field-correction algorithm.

LEVEL OF EVIDENCE

4 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:1534-1544.

Lightweight, compact, and high-performance 3T MR system for imaging the brain and extremities

PURPOSE

To build and evaluate a small-footprint, lightweight, high-performance 3T MRI scanner for advanced brain imaging with image quality that is equal to or better than conventional whole-body clinical 3T MRI scanners, while achieving substantial reductions in installation costs.

METHODS

A conduction-cooled magnet was developed that uses less than 12 liters of liquid helium in a gas-charged sealed system, and standard NbTi wire, and weighs approximately 2000 kg. A 42-cm inner-diameter gradient coil with asymmetric transverse axes was developed to provide patient access for head and extremity exams, while minimizing magnet-gradient interactions that adversely affect image quality. The gradient coil was designed to achieve simultaneous operation of 80-mT/m peak gradient amplitude at a slew rate of 700 T/m/s on each gradient axis using readily available 1-MVA gradient drivers.

RESULTS

In a comparison of anatomical imaging in 16 patients using T₂ -weighted 3D fluid-attenuated inversion recovery (FLAIR) between the compact 3T and whole-body 3T, image quality was assessed as equivalent to or better across several metrics. The ability to fully use a high slew rate of 700 T/m/s simultaneously with 80-mT/m maximum gradient amplitude resulted in improvements in image quality across EPI, DWI, and anatomical imaging of the brain.

CONCLUSIONS

The compact 3T MRI system has been in continuous operation at the Mayo Clinic since March 2016. To date, over 200 patient studies have been completed, including 96 comparison studies with a clinical 3T whole-body MRI. The increased gradient performance has reliably resulted in consistently improved image quality.

What we know and what we don't know about perinatal Zika virus infection: a systematic review

INTRODUCTION

Zika virus (ZIKV) infection has caused the most challenging worldwide infectious epidemic outbreak in recent months. ZIKV causes microcephaly and other congenital malformations. There is a need to perform updated systematic reviews on ZIKV infection periodically because this epidemic is bringing up new evidence with extraordinary speed. Areas covered: Evidence related to ZIKV infection in the gestational, perinatal, and early infant periods covering epidemiology, virology, pathogenesis, risk factors, time of infection during pregnancy, newborn symptoms, treatment, and vaccines. To this end, a search was performed using terms ['Zika'] AND ['Perinatal Infection'] OR ['Congenital Infection'] in the PubMed® international electronic database. Out of a total of 1,538 articles published until 30 November 2017, we finally assessed 106 articles articles that were relevant to the research areas included in this study. Expert commentary: ZIKV is a new teratogenic/neurotropic virus affecting fetuses. Many challenges are still far from being solved regarding the epidemiology, case definition, clinical and laboratory diagnosis, and preventive measures. An approach using 'omics' and new biomarkers for diagnosis, and a ZIKV-vaccine for treatment, might finally give us the tools to solve these challenges.

B0 concomitant field compensation for MRI systems employing asymmetric transverse gradient coils

PURPOSE

Imaging gradients result in the generation of concomitant fields, or Maxwell fields, which are of increasing importance at higher gradient amplitudes. These time-varying fields cause additional phase accumulation, which must be compensated for to avoid image artifacts. In the case of gradient systems employing symmetric design, the concomitant fields are well described with second-order spatial variation. Gradient systems employing asymmetric design additionally generate concomitant fields with global (zeroth-order or B₀ ) and linear (first-order) spatial dependence.

METHODS

This work demonstrates a general solution to eliminate the zeroth-order concomitant field by applying the correct B₀ frequency shift in real time to counteract the concomitant fields. Results are demonstrated for phase contrast, spiral, echo-planar imaging (EPI), and fast spin-echo imaging.

RESULTS

A global phase offset is reduced in the phase-contrast exam, and blurring is virtually eliminated in spiral images. The bulk image shift in the phase-encode direction is compensated for in EPI, whereas signal loss, ghosting, and blurring are corrected in the fast-spin echo images.

CONCLUSION

A user-transparent method to compensate the zeroth-order concomitant field term by center frequency shifting is proposed and implemented. This solution allows all the existing pulse sequences-both product and research-to be retained without any modifications. Magn Reson Med 79:1538-1544, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Effects of Surgical Factors on Cartilage Can Be Detected Using Quantitative Magnetic Resonance Imaging After Anterior Cruciate Ligament Reconstruction

BACKGROUND

Quantitative magnetic resonance (qMR) can be used to measure macromolecules in tissues and is a potential method of observing early cartilage changes in the development of posttraumatic osteoarthritis. Hypothesis/Purpose: We hypothesized that specific patient and surgical factors affecting cartilage matrix composition after anterior cruciate ligament (ACL) reconstruction (ACLR) can be detected using T1ρ and T2 relaxation times. Our purpose was to demonstrate this ability in a multicenter feasibility study.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A total of 54 patients who underwent ACLR underwent bilateral MRI at baseline before surgery and 6 months postoperatively. Operative findings were recorded. T1ρ and T2 relaxation times were calculated for 6 cartilage regions: the medial femur, lateral femur, medial tibia, lateral tibia, patella, and trochlea. A paired t test compared relaxation times at baseline and 6 months, univariate regression identified regions that influenced patient-reported outcome measures, and analysis of covariance was used to determine the surgical factors that resulted in elevated relaxation times at 6 months.

RESULTS

The injured knee had significantly prolonged T1ρ and T2 relaxation times in the tibiofemoral compartment at baseline and 6 months but had shorter values in the patellofemoral compartment compared with the uninjured knee. Prolonged T1ρ and T2 times at 6 months were noted for both the injured and uninjured knees. At 6 months, prolongation of T1ρ and T2 times in the tibial region was associated with lower patient-reported outcome measures. ACLR performed within 30 days of injury had significantly shorter T1ρ times in the tibial regions, and lateral meniscal tears treated with repair had significantly shorter T1ρ times than those treated with excision.

CONCLUSION

Prolonged relaxation times in multiple regions demonstrate how the injury affects the entire joint after an ACL tear. Changes observed in the uninjured knee may be caused by increased loading during rehabilitation, especially in the patellofemoral articular cartilage and distal femur. Relaxation times in the tibial regions may be predictive of patient symptoms at 6 months. These same regions are affected by surgical timing as early as 30 days after injury, but this may partially be reflective of the severity of the preoperative injury and the choice of treatment of meniscal tears.

Safety Studies for Use of Adipose Tissue-Derived Mesenchymal Stromal/Stem Cells in a Rabbit Model for Osteoarthritis to Support a Phase I Clinical Trial

Adipose‐derived mesenchymal stem cells (AMSCs) offer potential as a therapeutic option for clinical applications in musculoskeletal regenerative medicine because of their immunomodulatory functions and capacity for trilineage differentiation. In preparation for a phase I clinical trial using AMSCs to treat patients with osteoarthritis, we carried out preclinical studies to assess the safety of human AMSCs within the intra‐articular joint space. Culture‐expanded human AMSCs grown in human platelet‐lysate were delivered via intra‐articular injections into normal healthy rabbit knees and knees at risk for the development of osteoarthritis after bilateral medial anterior hemimeniscectomy. Treatment outcomes and safety were evaluated by assessing the general health, function, and behavior of the animals. Joint tissues were analyzed by x‐ray, magnetic resonance imaging, and histopathology. Intra‐articular AMSC therapy was well tolerated in this study. We did not observe adverse systemic reactions, nor did we find evidence of damage to intra‐articular joint tissues. Thus, the data generated in this study show a favorable safety profile for AMSCs within the joint space in support of a phase I clinical trial evaluating the clinical utility of AMSCs to treat osteoarthritis. Stem Cells Translational Medicine2017;6:910–922

Imaging of the Proximal and Distal Radioulnar Joints

The proximal and distal radioulnar joints form a unique articular arrangement between the radius and ulna, allowing pivot motion of the forearm and positioning the hand in space. Typically imaged in conjunction with the elbow, radiographs, computed tomography (CT), and MR imaging of the proximal radioulnar joint contribute unique diagnostic information. Because dysfunction of the distal radioulnar joint is often a result of instability, dynamic CT protocols stressing the joint in addition to anatomic imaging with radiographs and MR imaging is valuable. Detailed knowledge of the patient's clinical condition and careful selection of imaging protocols will maximize the benefits.

[The Spanish Society of Paediatric Infectious Diseases (SEIP) recommendations on the diagnosis and management of invasive candidiasis]

Candida yeasts are ubiquitous commensals, which can cause opportunistic infection in any location of the body. The source of infection may be both endogenous and exogenous. Invasive candidiasis encompasses different entities ranging from invasive candidiasis to disseminated multiorgan infection. Invasive candidiasis is the third leading cause of nosocomial bloodstream infection and the fourth of all nosocomial infections. It is also the most common invasive fungal infection in non-neutropenic critically ill patients, with a remarkable increase in the last 20 years owing to the increased survival of these patients and to more complex diagnostic, therapeutic and surgical procedures. Its incidence in infants, according to recent reviews, stands at 38.8 cases/100,000 children younger than 1 year. Candida albicans remains the most frequent isolate in invasive infections, although infections caused by other species have risen in the last years, such as C. kruzsei, C. glabrata and C. parapsilosis; the latter causing invasive candidiasis mainly associated with central venous catheter management, especially in neonatal units. The overall mortality of invasive candidiasis is high, with 30-day mortality reaching 20-44% in some series involving paediatric patients. This report provides an update on incidence, epidemiology, clinical presentation, diagnosis, treatment and outcome of invasive infection by Candida spp. in the paediatric patient.

MRI Findings of 26 Patients with Parsonage-Turner Syndrome

OBJECTIVE

The objective of our study was to describe the MRI features of patients with Parsonage-Turner syndrome. Familiarity with the MRI features associated with this entity is important because radiologists may be the first to suggest the diagnosis. Twenty-six patients with Parsonage-Turner syndrome were treated at our institution between 1997 and 2005. We retrospectively reviewed the MR images of patients with clinical or electromyographic evidence (or both) of acute brachial neuritis without a definable cause.

CONCLUSION

MRI of the brachial plexus and shoulder in patients with Parsonage-Turner syndrome showed intramuscular denervation changes involving one or more muscle groups of the shoulder girdle. The supraspinatus and infraspinatus muscles were the most commonly involved. MRI is sensitive for detecting signal abnormalities in the muscles of the shoulder girdle of patients with Parsonage-Turner syndrome. MRI may be instrumental in accurately diagnosing the syndrome.

Reprint of imaging of the elbow: a review of imaging findings in acute and chronic traumatic disorders of the elbow

Traumatic injuries of the elbow are frequent in patients of all ages but are particularly common in young children and adolescents engaged in normal play and athletic competition. Injury may result primarily due to direct trauma or may be secondary to transmission of forces through the elbow following a fall on an outstretched hand. In middle-aged and older individuals, chronic repetitive injuries tend to predominate. In all patients, radiographs remain the initial imaging study of choice. Many patients, however, may need advanced cross-sectional imaging (i.e. MRI, CT, or ultrasound) either at presentation or during the course of their treatment and follow-up. This article reviews the imaging appearance of common acute and chronic traumatic disorders of the elbow.

MR Imaging of Synovial Disorders of the Knee: An Update

Synovial disorders often affect the knee joint and are a common cause of morbidity. Before MR imaging, radiologists were limited in their ability to provide information about the presence or absence of synovial disease. With the advent of MR imaging, useful information can now be provided to referring clinicians, often at a time when the initiation of therapy may mitigate significantly the long-term sequelae of synovial disorders. MR imaging, owing to its superior soft-tissue contrast, is the imaging modality of choice for demonstrating and quantifying pathologic changes of the synovium. MR imaging provides invaluable information to the clinician regarding the need to either initiate or modify therapy in those patients suffering from diseases of, or affecting, the synovium.

Imaging of the elbow: a review of imaging findings in acute and chronic traumatic disorders of the elbow

Traumatic injuries of the elbow are frequent in patients of all ages but are particularly common in young children and adolescents engaged in normal play and athletic competition. Injury may result primarily due to direct trauma or may be secondary to transmission of forces through the elbow following a fall on an outstretched hand. In middle-aged and older individuals, chronic repetitive injuries tend to predominate. In all patients, radiographs remain the initial imaging study of choice. Many patients, however, may need advanced cross-sectional imaging (i.e. MRI, CT, or ultrasound) either at presentation or during the course of their treatment and follow-up. This article reviews the imaging appearance of common acute and chronic traumatic disorders of the elbow.

Magnetic resonance imaging with metal suppression for evaluation of periprosthetic osteolysis after total knee arthroplasty

Osteolysis around total knee arthroplasty (TKA) can be difficult to identify and quantitate on plain radiographs. This study reports on magnetic resonance imaging (MRI) with metal suppression for the evaluation of suspected periprosthetic osteolysis around TKA. We retrospectively reviewed 11 patients referred for MRI with suspected periprosthetic osteolysis. Radiographic and MRI findings and findings at revision arthroplasty were correlated. The presence of osteolysis was identified or suspected radiographically in all of the 11 patients. Osteolysis was confirmed in 10 patients by MRI. In 9 of 11 patients, the extent of osteolysis was greater on MRI than estimated radiographically. In 5 of 11 patients, MRI demonstrated additional osteolytic lesions which were radiographically occult. In one case, the amount of osteolysis on MRI was less than on initial radiographs, and in one case, osteolysis was felt to be present radiographically but was not confirmed on MRI. In all 7 of 11 patients subsequently treated with revision TKA, MRI findings were confirmed at revision.

Postoperative Imaging of the Knee

The knee is a frequently injured joint and, thus, a common focus of operative intervention. As operative techniques and imaging modalities evolve, radiologists must be aware of the expected postoperative appearance after knee surgeries that are performed commonly and also must be comfortable recognizing complications encountered commonly in the immediate and delayed postoperative period. Drawing on the large amount of attention this subject has received of late in the radiologic and orthopedic literature, this article reviews the knee surgeries performed most commonly and the expected normal and most frequently encountered abnormal postoperative imaging findings with an emphasis on MR imaging.

Imaging Findings in Desmoplastic Fibroma of Bone: Distinctive T2 Characteristics

OBJECTIVE

The purpose of this study was to evaluate the imaging features of desmoplastic fibroma of the bone, with an emphasis on MRI signal characteristics.

CONCLUSION

Significant T2 shortening of a nonsclerotic fibroosseous lesion should place desmoplastic fibroma high among the diagnostic considerations.

Oral immunization of mice with ricin toxoid vaccine encapsulated in polymeric microspheres against aerosol challenge

Mucosal (oral) immunization of mice with carrier-delivered ricin toxoid (RT) vaccine was accomplished by one long (7 weeks) or two short (4 weeks) immunization schedules. For the long and short immunization schedule two lots of vaccine were administered prepared with the same procedure but at different occasions. The long schedule consisted of a total of seven doses of 50 microg of vaccine in microencapsulated (lot #108) or aqueous form administered on days 1, 2, 3, 28, 29, 30 and 49. With the short schedule a total of seven or six doses of 25 microg (lot #111) were administered on days 1, 2, 3, 14, 15, 16 and 30, or on 1, 2, 14, 15, 30, 31 and 32, respectively. Mice immunized orally with the long schedule, 50 microg of RT vaccine incorporated into poly-DL-lactide-co-glycolyde (DL-PLG) microspheres (MS) produced serum IgG, IgG2a and IgA ELISA antibodies. All mice immunized with RT in DL-PLG MS (RT-MS) were protected against a lethal ricin aerosol challenge. In contrast, with the same schedule and with the same dose, the aqueous vaccine (RT) failed to stimulate IgG, IgG2a and IgA antibodies, and these mice were not protected against an aerosol ricin toxin challenge. With the shorter immunization scheme, seven doses of 25 microg RT-MS stimulated a significant, though reduced, protection with the microencapsulated, but not with the aqueous vaccine. When the first and second 3-day cycles of the short immunization schedule was reduced to two doses, and the 3-day cycle was administered at the end of the schedule, neither RT-MS nor RT stimulated protection against the challenge. These results indicated that successful oral immunization with RT-MS depended on both the dose and the schedule, consisting of three consecutive days of administration in two cycles, 4 weeks apart. Altering this schedule and the dose, resulted in a reduced protection or no protection at all. Furthermore, under the conditions of this study, the advantage of the microencapsulated RT vaccine over the aqueous vaccine for effective oral immunization was well demonstrated.

TPA-induced inhibition of gap junctional intercellular communication is not mediated through free radicals

The present investigation was designed to determine whether the inhibition of gap junction-mediated intercellular communication (GJIC) induced by TPA (12-O-tetradecanoylphorbol-13-acetate) in rat liver epithelial (WB-F344) cells in vitro is mediated through free radical production. As assessed by fluorescence redistribution after photobleaching (FRAP) analysis, GJIC was significantly inhibited in cells treated for 1 hr with either 10 ng/ml TPA or 500 microM hydrogen peroxide (H2O2). Addition of 1000 U/ml catalase or 25 microM N',N'-diphenyl-p-phenylenediamine (DPPD) to TPA-treated cells did not alleviate the TPA-induced inhibition of GJIC. However, the concurrent addition of 1000 U/ml catalase to the culture medium prevented the H2O2 inhibition of GJIC. 2'-7'-dichlorofluorescein-mediated fluorescence, a measure of free radical production utilizing the Meridian ACAS 470 interactive laser cytometer, was not significantly increased in WB-F344 cells treated with 10 and 100 ng/ml TPA when compared to control cells. However, polymorphonuclear leukocytes (PMNs) treated for 10 min with 100 ng/ml TPA showed a substantial oxidative burst, as did WB-F344 cells treated for 1 hr with 500 microM H2O2. The concurrent addition of 1000 U/ml catalase to the culture medium attenuated H2O2-mediated free radical production in both PMNs and WB-F344 cells. Data from this study do not support a role for free radicals in the TPA-induced inhibition of GJIC in WB-F344 cells.