Imaging in dermatomyositis in adults and children

Dermatomyositis is a rare autoimmune disorder in which an abnormal immune reaction against vascular endothelial antigens and endomysium leads to obstructive inflammatory changes of blood vessels within muscles, skin and other tissues. The disease is characterized by involvement of muscles, and less frequently of other systems, including the gastrointestinal tract, heart and lungs. Dermatomyositis may be diagnosed based on a detailed patient history, through clinical examination, detection of characteristic physical findings and certain specialized tests. Additional imaging studies may be performed to aid in the diagnosis. These include magnetic resonance imaging and ultrasound of the affected muscles. Magnetic resonance imaging is the modality of choice in the diagnostic work-up and monitoring of dermatomyositis affecting muscles, fasciae, and the subcutis. It may recognize acute inflammatory edematous changes in the affected muscles as well fatty replacement and atrophy. The role of ultrasound to diagnose and follow up muscle echogenicity, vascularity, elasticity and volume during treatment has increased over the last years in both adults and children. Ultrasound is used to discriminate between high and low disease activity, may show features of subclinical disease and may be used to confirm remission.

Joint Effusion and Bone Outlines of the Knee: Radiographic/MR Imaging Correlation

Knee radiographs are widely used in clinical practice. Many features can be depicted when a systematic analysis of the different views is performed. This article focuses on different types of joint effusion and on the analysis of the bone outlines of the knee, particularly on the lateral view. Systematic analysis of these bone outlines and knowledge of several key points are particularly useful for the depiction of abnormal bone morphology or positioning, and of several conditions, such as trochlear dysplasia, patellar dislocation, impaction fractures, or ligament injuries and avulsion fractures.

Comparison of regional bone marrow adiposity characteristics at the hip of underweight and weight-recovered women with anorexia nervosa using magnetic resonance spectroscopy

Bone marrow adiposity (BMA) is an underestimated tissue, with properties that may alter bone strength especially in diseases that fragilize bone such as anorexia nervosa. In the present study, we investigated the regional characteristics of BMA at the hip of 40 underweight and 36 weight-recovered anorexic women, along with 10 healthy women, using magnetic resonance spectroscopy at multiple anatomical subregions (acetabulum, femoral neck, proximal femoral diaphysis and greater trochanter) to measure bone marrow fat fraction (BMFF) and apparent lipid unsaturation levels (aLUL). Correlations between BMFF, aLUL, body fat percentage (BF), and bone mineral density (BMD) at the femoral neck and total hip, both measured using dual-energy X-ray absorptiometry, were assessed in anorexic patients. Whereas BMFF was significantly higher and aLUL significantly lower at the femoral neck of underweight and weight-recovered patients compared to controls (BMFF: 90.1 ± 6.7% and 90.3 ± 7.5% respectively versus 81.3 ± 8.1%; aLUL: 7.6 ± 1.4% and 7.3 ± 1.3% versus 9.2 ± 1.5%), BMFF and aLUL were not significantly different between the 2 subgroups of patients. Besides, three noteworthy features were observed between BMA and the other measured parameters in anorexic patients. First, synergic alterations of BMA were observed at all sites, with an inverse relationship between BMFF and aLUL (ρ = -0.88). Second, bone mineral compartment and BMA were associated, as a negative correlation between total hip BMD and BMFF was observed at all sites except the greater trochanter (ρ = [-0.32;-0.29]), as well as a positive correlation with aLUL at all sites except the proximal femoral diaphysis (ρ = [0.25;0.37]). Finally, we found a positive correlation between BF and BMFF at the femoral neck (ρ = 0.35), and a negative correlation between BF and aLUL at this same subregion (ρ = -0.33), which suggest a complex relationship between BMA and BF. Overall, BMA possesses regional specificities which may impair bone health, even after weight recovering.

Carpal tunnel ultrasound: is the "safe zone" on the ulnar side of the median nerve really avascular?

INTRODUCTION

Numerous publications have studied the regional anatomy of the carpal tunnel to define a "safe zone" to reduce the risk of perioperative neurovascular complications. This zone, located between the ulnar neurovascular bundle and the median nerve, is considered to be safe mainly because of the absence of vascular structures. This study aims to assess the presence of arterioles within this area using superb microvascular imaging (SMI).

MATERIALS AND METHODS

The images from patients who underwent a bilateral routine wrist ultrasound with SMI, between January 28 and February 28, 2019, were retrospectively reviewed by two radiologists to evaluate the presence and location of arterioles in the safe zone. In addition, cadaveric wrists injected with intra-arterial red latex underwent dissection of the carpal tunnel.

RESULTS

The images from 27 patients (54 wrists) were reviewed. In the safe zone, arterioles were seen superficial to the retinaculum in 36 wrists (36/54; 66.7%) and deep to the retinaculum in 21 wrists (21/54; 38.9%). The arterioles located deep to the retinaculum were more frequently found close to the median nerve (21/54; 38.9%) than to the ulnar artery (9/54; 16.7%). In five cadaveric wrists, arterioles were detected superficial to the retinaculum in 3 wrists (3/5; 60%) and deep to the retinaculum in 2 wrists (2/5; 40%).

CONCLUSION

Arterioles can be seen in the safe zone both superficial and deep to the flexor retinaculum. Deep to the retinaculum, they are mainly observed in the proximal aspect of the carpal tunnel and more frequently close to the median nerve.

KEY POINTS

• Superb microvascular imaging (SMI) enables the visualization of arterioles within the "safe zone" of the carpal tunnel (visible both superficial and deep to the flexor retinaculum). • Arterioles were more frequently observed in the proximal aspect of the carpal tunnel. • Deep to the retinaculum, arterioles were more frequently seen in proximity to the median nerve.

Impact of the rise of artificial intelligence in radiology: What do radiologists think?

PURPOSE

The purpose of this study was to assess the perception, knowledge, wishes and expectations of a sample of French radiologists towards the rise of artificial intelligence (AI) in radiology.

MATERIAL AND METHOD

A general data protection regulation-compliant electronic survey was sent by e-mail to the 617 radiologists registered in the French departments of Nord and Pas-de-Calais (93 radiology residents and 524 senior radiologists), from both public and private institutions. The survey included 42 questions focusing on AI in radiology, and data were collected between January 16^th and January 31^st, 2019. The answers were analyzed together by a senior radiologist and a radiology resident.

RESULTS

A total of 70 radiology residents and 200 senior radiologists participated to the survey, which corresponded to a response rate of 43.8% (270/617). One hundred ninety-eight radiologists (198/270; 73.3%) estimated they had received insufficient previous information on AI. Two hundred and fifty-five respondents (255/270; 94.4%) would consider attending a generic continuous medical education in this field and 187 (187/270; 69.3%) a technically advanced training on AI. Two hundred and fourteen respondents (214/270; 79.3%) thought that AI will have a positive impact on their future practice. The highest expectations were the lowering of imaging-related medical errors (219/270; 81%), followed by the lowering of the interpretation time of each examination (201/270; 74.4%) and the increase in the time spent with patients (141/270; 52.2%).

CONCLUSION

While respondents had the feeling of receiving insufficient previous information on AI, they are willing to improve their knowledge and technical skills on this field. They share an optimistic view and think that AI will have a positive impact on their future practice. A lower risk of imaging-related medical errors and an increase in the time spent with patients are among their main expectations.

Artificial intelligence to diagnose meniscus tears on MRI

PURPOSE

The purpose of this study was to build and evaluate a high-performance algorithm to detect and characterize the presence of a meniscus tear on magnetic resonance imaging examination (MRI) of the knee.

MATERIAL AND METHODS

An algorithm was trained on a dataset of 1123 MR images of the knee. We separated the main task into three sub-tasks: first to detect the position of both horns, second to detect the presence of a tear, and last to determine the orientation of the tear. An algorithm based on fast-region convolutional neural network (CNN) and faster-region CNN, was developed to classify the tasks. The algorithm was thus used on a test dataset composed of 700 images for external validation. The performance metric was based on area under the curve (AUC) analysis for each task and a final weighted AUC encompassing the three tasks was calculated.

RESULTS

The use of our algorithm yielded an AUC of 0.92 for the detection of the position of the two meniscal horns, of 0.94 for the presence of a meniscal tear and of 083 for determining the orientation of the tear, resulting in a final weighted AUC of 0.90.

CONCLUSION

We demonstrate that our algorithm based on fast-region CNN is able to detect meniscal tears and is a first step towards developing more end-to-end artificial intelligence-powered diagnostic tools.

Automatic knee meniscus tear detection and orientation classification with Mask-RCNN

PURPOSE

This work presents our contribution to a data challenge organized by the French Radiology Society during the Journées Francophones de Radiologie in October 2018. This challenge consisted in classifying MR images of the knee with respect to the presence of tears in the knee menisci, on meniscal tear location, and meniscal tear orientation.

MATERIALS AND METHODS

We trained a mask region-based convolutional neural network (R-CNN) to explicitly localize normal and torn menisci, made it more robust with ensemble aggregation, and cascaded it into a shallow ConvNet to classify the orientation of the tear.

RESULTS

Our approach predicted accurately tears in the database provided for the challenge. This strategy yielded a weighted AUC score of 0.906 for all three tasks, ranking first in this challenge.

CONCLUSION

The extension of the database or the use of 3D data could contribute to further improve the performances especially for non-typical cases of extensively damaged menisci or multiple tears.

Dynamic contrast-enhanced MRI perfusion of normal muscle in adult hips: Variation of permeability and semi-quantitative parameters

The purpose of this prospective study was to ascertain the degree of variation of semi-quantitative and permeability parameters on DCE-MRI of normally appearing striated muscles. Dynamic contrast-enhanced MRI of the right hip was performed in 20 women and 24 men. Mean age was 39.1 ± 12.4 years. Two regions of interest (ROI) were drawn in twelve muscles of anterior, medial and gluteal compartments: a free-form ROI covering the largest muscle section and a smaller elliptical ROI. Semi-quantitative and permeability parameters were calculated using the extended Tofts model. Statistical analysis was performed with a linear mixed model to assess perfusion parameters variation. Intra- and inter-observer agreements were assessed. The intra-observer agreement was considered to be good for free-form ROI (minimum Intra-Class Coefficient (ICC) = 0.72) and moderate for elliptical ROI (minimum ICC = 0.51), while the inter-observer agreement was considered to be bad in both cases (minimum ICC = 0.11). There was a high inter-individual variation in most of the perfusion parameters evaluated. The average coefficients of variation were: Time To Peak = 9%, Area Under the Curve = 44%, V_e = 61%, K_ep = 90%, Initial Slope = 99%, and K^trans = 128%. A considerable variation in resting muscle perfusion parameters was seen. This could lead to errors in the analysis of muscle DCE-MRI studies or oncologic/non oncologic studies using muscle as a referential. Further studies targeted on acquisition protocols and post-processing software are necessary to improve the performance of muscle MR perfusion.

Sacroiliac joints: anatomical variations on MR images

OBJECTIVE

To describe the appearance of the anatomical variations of the sacroiliac joints (SIJ) on MR images and to highlight the potential MR features that might be misleading.

METHODS

Consecutive MRI examinations of SIJs performed at our department from January 2015 to December 2016 were retrospectively analyzed. As one of our goals was to describe potential misleading edematous or structural changes associated with SIJ anatomical variations, patients fulfilling the ASAS criteria were excluded from this study to ensure that signal intensity changes would not be related to sacroiliitis. Five anatomical variations and a dysmorphic appearance of the SIJ were detected.

RESULTS

The final group consisted of 157 patients. Unilateral or bilateral anatomical variations of the SIJ were found in 50 patients (accessory SIJ, iliosacral complex and sacral defect in 17, 18 and 21 patients, respectively, and synostosis in one patient). A dysmorphic appearance of the SIJ was found in 26 patients. No case of an unfused ossification centers was depicted. Structural and/or edematous changes of the facing bones were quite frequently observed in accessory and dysmorphic SIJ. Iliosacral complex and sacral defects could be associated with prominent vessels running along their bony surfaces.

CONCLUSION

Several anatomical variations of the SIJs are relatively commonly seen on MR images, particularly in females. These variations may be associated with signal intensity changes, which may be mechanical and not necessarily inflammatory in nature.

KEY POINTS

• Anatomical variations of SIJ may involve the cartilaginous or ligamentous part of the joint • Anatomical variations of SIJ are sometimes associated with edematous and/or structural changes of the adjacent bone • Anatomical variations of the SIJ can be misleading on MR imaging.

Musculoskeletal Manifestations of Non-RA Connective Tissue Diseases: Scleroderma, Systemic Lupus Erythematosus, Still's Disease, Dermatomyositis/Polymyositis, Sjögren's Syndrome, and Mixed Connective Tissue Disease

The most common systemic rheumatologic conditions are connective tissue diseases (including rheumatoid arthritis [RA]) followed by spondyloarthropathy. With the advent of biotherapies and imaging biomarkers, development in the imaging of RA and spondyloarthropathies has received substantial attention in the literature. This article details the various musculoskeletal imaging features of the other connective tissue diseases such as scleroderma and progressive systemic sclerosis, systemic lupus erythematosus, Still's disease, dermatomyositis and polymyositis, Sjögren's syndrome, and mixed connective tissue disease.

Assessment of the zonal variation of perfusion parameters in the femoral head: a 3-T dynamic contrast-enhanced MRI pilot study

OBJECTIVE

The objective was to describe MR perfusion characteristics of the femoral head, with a focus on the subchondral bone.

MATERIALS AND METHODS

This prospective monocentric study was approved by our local Ethics Committee. Written informed consent was obtained from all subjects. Dynamic contrast-enhanced MRI of the right hip was performed in 59 adults with suspected spondyloarthritis (32 women, 28 men). Mean age was 37.5 (±12.5) years. Regions of interest were drawn in the femoral head epiphysis, in the subchondral areas the most exposed to mechanical load (superolateral, anterosuperior, and posterior zones) and in areas less exposed to mechanical load (inferior subchondral zone and center of the femoral head). Semi-quantitative and pharmacokinetic parameters were calculated using the Tofts model. Statistical analysis was performed with a linear mixed model to compare the perfusion parameters in the different femoral head zones.

RESULTS

Extravascular extracellular volume and area under the curve were lower in the superolateral zone than in the inferior zone (p = 0.0135 and p < 0.0001 respectively) and the central zone (p = 0.007 and p = 0.0134 respectively). Extravascular extracellular volume and rate constant were lower in the anterosuperior zone than in the inferior zones (p = 0.011 and p = 0.029). In the anterosuperior zone, extravascular extracellular volume was lower, and time to peak was higher than in the central zones (p = 0.0056 and p = 0.0013 respectively). No significant differences were found for any values between other paired zones.

CONCLUSION

The perfusion of femoral head subchondral bone assessed with dynamic contrast-enhanced magnetic resonance imaging is not homogeneous: the areas exposed to more mechanical loading are less perfused.

Anatomical and MR correlative study of the proximal sciatic nerve vasculature

OBJECTIVE

The aim of our study is to demonstrate that increased T₂ signal on MRI could be due to intraneural vessels in asymptomatic individuals, and may therefore be a normal finding.

METHODS

An initial anatomic cadaveric study was undertaken to gain a better understanding of the vascular supply of the proximal sciatic nerve. Secondly, a retrospective study of MR imaging of patients without sciatic symptoms was performed to assess the prevalence of intraneural vessels, defined as hyperintensity on at least three consecutive slices on both T₂ and gadolinium enhanced T₁ weighted imaging, visible on routine MSK pelvic imaging.

RESULTS

The anatomical study demonstrated a relatively abundant blood supply in the peri-ischiatic region. In the MR study, 20/76 (26%) patients showed visible intraneural vessels. More than one intraneural vessel was depicted in two of the sciatic nerves. Direct branching between the extrinsic and intrinsic systems was seen in only five cases.

CONCLUSION

Normal intraneural vessels can frequently be seen within the sciatic nerve on routine musculoskeletal pelvic imaging. Advances in knowledge: T₂ hyperintensity in the proximal sciatic nerve can be due to intraneural vessels and should not necessarily be reported as abnormal.

Conventional Radiology in Crystal Arthritis: Gout, Calcium Pyrophosphate Deposition, and Basic Calcium Phosphate Crystals

This article reviews the main radiographic features of crystal deposition diseases. Gout is linked to monosodium urate crystals. Classic radiographic features include subcutaneous tophi, large and well-circumscribed paraarticular bone erosions, and exuberant bone hyperostosis. Calcium pyrophosphate deposition (CPPD) can involve numerous structures, such as hyaline cartilages, fibrocartilages, or tendons. CPPD arthropathy involves joints usually spared by osteoarthritis. Basic calcium phosphate deposits are periarticular or intraarticular. Periarticular calcifications are amorphous, dense, and round or oval with well-limited borders, and most are asymptomatic. When resorbing, they become cloudy and less dense with an ill-defined shape and can migrate into adjacent structures.

Bone marrow perfusion measured with dynamic contrast enhanced magnetic resonance imaging is correlated to body mass index in adults

Bone marrow metabolism is complex and far from being fully understood. Novel aspects, such as the roles of bone marrow adiposity and vascularisation in bone metabolism currently attract attention. There is also a growing interest in the influence obesity might have on bone metabolism. Our objective was to determine the effect of BMI on bone marrow perfusion parameters using dynamic contrast-enhanced magnetic resonance imaging. This prospective monocentric study was approved by our local Ethics committee. Written consent was obtained. The right hip of 59 adults under 60years old (mean age 37.5) was imaged with a dynamic 3D T1 spoiled gradient echo magnetic resonance imaging sequence. Mean BMI was 24.8 (+/-4.4). Perfusion parameters were measured in the acetabulum and femoral neck, in the greater trochanter, in the femoral head epiphysis and in the subcutaneous adipose tissue. Associations between perfusion parameters and BMI were studied using a linear mixed model adjusted for age and sex effects. Our results showed that as the BMI increased, the exchanges between blood and bone marrow appeared more important (increased K_trans and K_ep values, p=0.018 and p=0.002 respectively) and the intramedullary blood flow appeared increased (lower time to peak values, p=0.0002). In the subcutaneous fat, as the BMI increased, the vascularization decreased (lower area under the curve and initial slope values, p=0.019 and p=0.013 respectively). These results suggest that there is a relation between bone marrow perfusion and BMI, and that subcutaneous fat and bone marrow fat have different microvascular behaviours. Researchers must be aware of the effect of BMI on bone marrow perfusion parameters when they build a MR research protocol and analyse their data. A better understanding of these findings may provide the basis for the management of obesity-related bone changes.

Results and limitations of humeral head resurfacing: 105 cases at a mean follow-up of 5 years

BACKGROUND

The objective of this study was to assess clinical and computed-tomography (CT) outcomes at least 2 years after humeral head resurfacing to treat concentric gleno-humeral osteoarthritis.

HYPOTHESIS

Humeral head resurfacing provides similar outcomes to those achieved with stemmed humeral head implants.

MATERIALS AND METHODS

This single-centre retrospective study included 40 Copeland™ and 65 Aequalis™ humeral resurfacing heads implanted between 2004 and 2012. Mean patient age at diagnosis was 64 years. The diagnoses were osteoarthritis with an intact (68%) or torn (21%) rotator cuff, avascular necrosis (5%), osteoarthritis complicating chronic instability (3%), post-traumatic osteoarthritis (2%), and chronic inflammatory joint disease (1%). Validated clinical scores, radiographs, and CT before surgery and at last follow-up were compared.

RESULTS

During the mean follow-up of 56 months, complications occurred in 24 implants. Revision surgery with reverse shoulder replacement was required in 18 cases, after a mean of 43.6 months, to treat glenoid wear or a rotator cuff tear. At last follow-up, for the implants that did not require revision surgery, the mean Constant score was 64/100. The implants had a mean varus of 5° and mean retroversion of -13.3°. The mean increase in glenoid cavity depth was 2.4mm. Mean increases in medial and lateral humeral offset were 1.9mm and 2.7mm, respectively. Pre-operative factors significantly associated with failure were rotator cuff tear (P=0.017) and glenoid erosion (P=0.001).

DISCUSSION

We found a high failure rate related to glenoid wear or progressive rotator-cuff impairment, although CT showed no evidence of implant malposition or overstuffing. Previous studies of stemmed humeral head implants showed better outcomes. Given the low medium-term prosthesis survival rate, we now reserve humeral head resurfacing for concentric osteoarthritis without glenoid erosions or rotator cuff damage.

LEVEL OF EVIDENCE

IV, retrospective study.