An introduction to the EULAR-OMERACT rheumatoid arthritis MRI reference image atlas

High-resolution (18)F-FDG PET/CT for assessing disease activity in rheumatoid and psoriatic arthritis: findings of a prospective pilot study

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 ((18)F-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 (18)F-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 (18)F-FDG uptake was measured for joints with synovitis compared with unaffected joints (p < 0.05), with patterns of (18)F-FDG uptake along the tendons, at the enthesis and in the nail bed, consistent with tenosynovitis, enthesitis and nail dystrophy, respectively.

CONCLUSION

High-resolution (18)F-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 non-invasive, objective assessment of RA or PsA severity and therapy selection.

Efficacy of VX-509 (decernotinib) in combination with a disease-modifying antirheumatic drug in patients with rheumatoid arthritis: clinical and MRI findings

OBJECTIVE

To assess early effects on joint structures of VX-509 in combination with stable disease-modifying antirheumatic drug (DMARD) therapy using MRI in adults with rheumatoid arthritis (RA).

METHODS

This phase II, placebo-controlled, double-blind, dose-ranging study randomised patients with RA and inadequate DMARD response to VX-509 100 mg (n=11), 200 mg (n=10) or 300 mg (n=10) or placebo (n=12) once daily for 12 weeks. Outcome measures included American College of Rheumatology score (ACR20; improvement of ≥20%) and disease activity score (DAS28) using C reactive protein (CRP), and the RA MRI scoring (RAMRIS) system.

RESULTS

ACR20 response at week 12 was 63.6%, 60.0% and 60.0% in the VX-509 100-mg, 200-mg and 300-mg groups, respectively, compared with 25.0% in the placebo group. DAS28-CRP scores decreased in a dose-dependent manner with increasing VX-509 doses. Decreases in RAMRIS synovitis scores were significantly different from placebo for all VX-509 doses (p<0.01) and for RAMRIS osteitis scores (p<0.01) for VX-509 300 mg. Treatment was generally well tolerated.

CONCLUSIONS

VX-509 plus a DMARD reduced the signs and symptoms of RA in patients with an inadequate response to a DMARD alone. MRI responses were detected at week 12. Treatment was generally well tolerated.

TRIAL REGISTRATION NUMBER

NCT01754935; results.

Accurate quantitative assessment of synovitis in rheumatoid arthritis using pixel-by-pixel, time-intensity curve shape analysis

OBJECTIVE

To improve on the reproducibility and sensitivity of the assessment of patients with rheumatoid arthritis (RA), two semi-automated measurement methods of the area of enhancing pannus (AEP), based on thresholding (AEP_THRES) and pixel-by-pixel time-intensity curve analysis (AEP_TIC), were evaluated as an alternative for the gold-standard manual contouring method (AEP_MANUAL).

METHODS

8 patients (7 females and 1 male) with RA of the wrist or finger joints participated in the study. A three-dimensional contrast-enhanced dynamic sequence was used at 3 T. After identifying the most relevant time-intensity curve (TIC) shape in terms of synovitis by comparing with the synovitis score using the RA-MRI scoring system, three different approaches for measuring the AEP were performed. Spearman's test of rank correlation was used to compare AEPs via two semi-automated methods (AEP_THRES and AEP_TIC) against manual segmentation (AEP_MANUAL) in the entire hand region as well as the wrist and the finger regions.

RESULTS

The TIC shape of "washout after fast initial enhancement" had excellent correlation with synovitis score (r = 0.809). The correlation coefficient between AEP_TIC and AEP_MANUAL was evaluated to be better than that of AEP_THRES and AEP_MANUAL in the wrist region (AEP_THRES: r = 0.716, AEP_TIC: r = 0.815), whereas these were of comparable accuracy for the entire hand and the finger regions.

CONCLUSION

This study suggests that TIC analysis may be an alternative to manual contouring for pannus quantification and provides important clinical information of the extent of the disease in patients with RA.

ADVANCES IN KNOWLEDGE

TIC shape analysis can be applied for new quantitative assessment for RA synovitis in the wrist.

Magnetic resonance imaging in early rheumatoid arthritis: a multicenter, prospective study

To identify the magnetic resonance imaging (MRI) features of hands and wrists in early rheumatoid arthritis (RA). A total of 129 early arthritis patients (≤1 year) were enrolled in the study. At presentation, MRI of the hands was performed, with clinical and laboratory analyses. After a 1-year follow-up, clinical diagnosis of early RA or non-RA was confirmed by two rheumatologists. The characteristics of MRI variables at baseline in RA patients not fulfilling ACR 1987 criteria [RA-87(-)] were compared with those fulfilling ACR1987 criteria [RA-87(+)] and non-RA. In the 129 early arthritis patients, 90 were diagnosed with RA in a 1-year follow-up. There were 47.8 % (43/90) of the RA patients not fulfilling ACR 1987 criteria [RA-87(-)]. The scores of synovitis in RA-87(-) patients were similar with those in RA-87(+) [Synovitis score, 14.0 (IQR, 4.0-25.0) vs. 14.0 (IQR, 10.0-25.0), p > 0.05]. Compared with those in non-RA, RA-87(-) patients had higher synovitis scores and occurrence of synovitis in proximal interphalangeal (PIP) joints [synovitis score, 14.0 (IQR, 4.0-25.0) vs. 6.0 (IQR, 2.0-14.5), p = 0.046; occurrence of PIP synovitis: 53.5 vs. 27.3 %, p = 0.02]. There was no significant difference of bone marrow edema, bone erosion, and tenosynovitis between RA-87(-) and non-RA. Synovitis in PIP joints was independent predictor for RA-87(-) [OR, 3.1 (95 %CI 1.2-8.1)]. High synovitis scores and synovitis in PIP joints on MRI were important in early RA, especially those not fulfilling ACR 1987 criteria.

Erosion or normal variant? 4-year MRI follow-up of the wrists in healthy children

BACKGROUND

A large proportion of healthy children have wrist changes on MRI, namely carpal depressions, findings that have been described as pathological in children with juvenile idiopathic arthritis.

OBJECTIVE

We performed follow-up imaging in a cohort of healthy children to evaluate carpal surface depressions over time, focusing on the presence of overlying cartilage as a potential discriminator between normal variants and true erosions.

MATERIALS AND METHODS

74 of the initial cohort of 89 healthy children (83%) had a re-scan of their wrists using the same protocol, including coronal T1 and fat-saturated T2 sequences. A cartilage-selective sequence was added for this study. We registered number and location of bony depressions and presence of overlying cartilage.

RESULTS

The total number of carpal depressions increased by age group and over time; their location was unchanged in 370 of 487 (76%) carpal sites and 91 of 117 (78%) metacarpal sites. In total, 426 of the 1,087 (39.2%) bony depressions were covered by cartilage, with a decreasing percentage by age (P = 0.001).

CONCLUSION

Normal appearances during growth, such as bony depressions, should not be mistaken for pathology. There must be additional findings to support a diagnosis of disease. A cartilage sequence may add to the diagnostic image analysis.

Safety and efficacy of intra-articular anti-tumor necrosis factor α agents compared to corticosteroids in a treat-to-target strategy in patients with inflammatory arthritis and monoarthritis flare

The aim of this study was to assess safety and efficacy of ultrasonography (US)-guided intra-articular injections using tumor necrosis factor (TNF) blockers compared to corticosteroids in rheumatoid arthritis (RA) or psoriatic arthritis (PsA) patients, experiencing refractory monoarthritis despite the current systemic therapy. Eighty-two patients were randomized to receive three intra-articular injections monthly of either corticosteroid or TNF blockers. Primary endpoints were the safety and an improvement greater than 20% for visual analogic scales of involved joint pain in patients injected with anti-TNFα. Further clinical, US, and magnetic resonance imaging (MRI) evaluations were considered secondary endpoints. Intra-articular TNF blockers are a safe strategy, determining a significant reduction of patient and physician reported clinical outcomes and US/MRI scores, in RA and PsA patients, when compared to intra-articular injections of corticosteroids. US guidance excluded the possibility to inject the drug in the wrong site, maximizing local effects, reducing systemic effects, and increasing the safety of the procedure. Patients with inflammatory monoarthritis could be successfully treated with US-guided intra-articular TNF blockers that are a safe and well tolerated procedure, to achieve a longstanding clinical and radiological good clinical response and/or disease remission.

Automated assessment of synovitis in 0.2T magnetic resonance images of the wrist

According to the current recommendations in diagnosis of rheumatoid arthritis (RA), Magnetic Resonance (MR) images of wrist joints are used to evaluate three main types of lesions: synovitis, bone edema and bone erosions. In the clinical practice, the RA-related lesions seen in MR images are assessed manually with the semi-quantitative RAMRIS scoring system. In this paper we present an automated method for inflamed synovial membrane volume determination, based on the analysis of pre- and post-contrast MR images and segmentation of wrist bones seen in MR images. We found that the correlation between the automatically quantified volume of synovitis and RAMRIS scores was in the range from 0.76 to 0.87 for the total RAMRIS synovitis score. This can be compared with the correlation between the manually quantified volume of synovitis and RAMRIS scores which was in the range from 0.75 to 0.81 for the total synovitis score. The results of the study demonstrate that computer assisted methods for assessment of synovitis have great potential for clinical applications.

Standardized quantitative measurements of wrist cartilage in healthy humans using 3T magnetic resonance imaging

AIM: To quantify the wrist cartilage cross-sectional area in humans from a 3D magnetic resonance imaging (MRI) dataset and to assess the corresponding reproducibility.

METHODS: The study was conducted in 14 healthy volunteers (6 females and 8 males) between 30 and 58 years old and devoid of articular pain. Subjects were asked to lie down in the supine position with the right hand positioned above the pelvic region on top of a home-built rigid platform attached to the scanner bed. The wrist was wrapped with a flexible surface coil. MRI investigations were performed at 3T (Verio-Siemens) using volume interpolated breath hold examination (VIBE) and dual echo steady state (DESS) MRI sequences. Cartilage cross sectional area (CSA) was measured on a slice of interest selected from a 3D dataset of the entire carpus and metacarpal-phalangeal areas on the basis of anatomical criteria using conventional image processing radiology software. Cartilage cross-sectional areas between opposite bones in the carpal region were manually selected and quantified using a thresholding method.

RESULTS: Cartilage CSA measurements performed on a selected predefined slice were 292.4 ± 39 mm² using the VIBE sequence and slightly lower, 270.4 ± 50.6 mm², with the DESS sequence. The inter (14.1%) and intra (2.4%) subject variability was similar for both MRI methods. The coefficients of variation computed for the repeated measurements were also comparable for the VIBE (2.4%) and the DESS (4.8%) sequences. The carpus length averaged over the group was 37.5 ± 2.8 mm with a 7.45% between-subjects coefficient of variation. Of note, wrist cartilage CSA measured with either the VIBE or the DESS sequences was linearly related to the carpal bone length. The variability between subjects was significantly reduced to 8.4% when the CSA was normalized with respect to the carpal bone length.

CONCLUSION: The ratio between wrist cartilage CSA and carpal bone length is a highly reproducible standardized measurement which normalizes the natural diversity between individuals.

Relationship between tissue stress during gait in healthy volunteers and patterns of urate deposition and bone erosion in gout: a biomechanical computational modelling study

Objectives

To determine whether patterns of high internal tissue stress during gait are associated with patterns of monosodium urate crystal deposition and bone erosion in gout.

Methods

We compared patterns of foot von Mises stress predicted computationally during gait in volunteers of normal and high body mass index (BMI) with patterns of urate deposition in gout and asymptomatic hyperuricaemia, and bone erosion in gout using dual-energy and conventional CT data.

Results

The highest average and peak von Mises stress during gait was observed at the third metatarsal (MT) head. Similar stress patterns were observed for high and low BMI groups. In contrast, for both urate deposition and bone erosion, the first MT head was most frequently affected, with very infrequent involvement of the third MT head. There was no clear relationship between average or peak von Mises stress patterns with patterns of urate deposition or bone erosion (−0.29>r<0.16). Addition of BMI into linear regression models did not alter the findings.

Conclusions

These data do not support the concept that elevated internal tissue stress during biomechanical loading plays an important role in patterns of monosodium urate crystal deposition or structural damage in gout.

Polish Medical Society of Radiology and Polish Society of Rheumatology Recommendations for Magnetic Resonance Imaging of Musculoskeletal Disorders in Rheumatology

This document presents the recommendations of the Polish Medical Society of Radiology (PLTR) and the Polish Society of Polish Society of Rheumatology (PTR) regarding the standards of collaboration between radiologists and rheumatologists so as to optimize the diagnostics and treatment of patients with rheumatic diseases of the musculoskeletal system, including rheumatoid arthritis and spondyloarthropathies.

Computer-aided and manual quantifications of MRI synovitis, bone marrow edema-like lesions, erosion and cartilage loss in rheumatoid arthritis of the wrist

PURPOSE

To investigate the reliability and validity of computer-aided automated and manual quantification as well as semiquantitative analysis for MRI synovitis, bone marrow edema-like lesions, erosion and cartilage loss of the wrist in rheumatoid arthritis (RA) compared to the OMERACT-RAMRIS.

METHODS AND MATERIALS

Wrist MRI was performed at 3 T in 16 patients with RA. Synovial volume and perfusion, bone marrow edema-like lesion (BMEL) volume, signal intensity and perfusion, and erosion dimensions were measured manually and using an in-house-developed automated software algorithm; findings were correlated with the OMERAC-RAMRIS gradings. In addition, a semiquantitative MRI cartilage loss score system was developed. Intraclass correlation coefficients (ICCs) were used to test the reproducibility of these quantitative and semiquantitative techniques. Spearman correlation coefficients were calculated between lesion quantifications and RAMRIS and between the MRI cartilage score and radiographic Sharp van der Heijde joint space narrowing scores.

RESULTS

The intra- and interobserver ICCs were excellent for synovial, BMEL and erosion quantifications and cartilage loss grading (all >0.89). The synovial volume, BMEL volume and signal intensity, and erosion dimensions were significantly correlated with the corresponding RAMRIS (r = 0.727 to 0.900, p < 0.05). Synovial perfusion parameter maximum enhancement (Emax) was significantly correlated with synovitis RAMRIS (r = 0.798). BMEL perfusion parameters were not correlated with the RAMRIS BME score. Cartilage loss gradings from MRI were significantly correlated with the Sharp joint space narrowing scores (r = 0.635, p = 0.008).

CONCLUSION

The computer-aided, manual and semiquantitative methods presented in this study can be used to evaluate MRI pathologies in RA with excellent reproducibility. Significant correlations with standard RAMRIS were found in the measurements using these methods.

The OMERACT MRI in Arthritis Working Group - Update on Status and Future Research Priorities

OBJECTIVE

To provide an update on the status and future research priorities of the Outcome Measures in Rheumatology (OMERACT) magnetic resonance imaging (MRI) in arthritis working group.

METHODS

A summary is provided of the activities of the group within rheumatoid arthritis (RA), psoriatic arthritis (PsA), and osteoarthritis (OA), and its research priorities.

RESULTS

The OMERACT RA MRI score (RAMRIS) evaluating bone erosion, bone edema (osteitis), and synovitis is now the standard method of quantifying articular pathology in RA trials. Cartilage loss is another important part of joint damage, and at the OMERACT 12 conference, we provided longitudinal data demonstrating reliability and sensitivity to change of the RAMRIS JSN component score, supporting its use in future clinical trials. The MRI group has previously developed a PsA MRI score (PsAMRIS). At OMERACT 12, PsAMRIS was evaluated in a randomized placebo-controlled trial of patients with PsA, demonstrating the responsiveness and discriminatory ability of applying the PsAMRIS to hands and feet. A hand OA MRI score (HOAMRIS) was introduced at OMERACT 11, and has subsequently been further validated. At OMERACT 12, good cross-sectional interreader reliability, but variable reliability of change scores, were reported. Potential future research areas were identified at the MRI session at OMERACT 12 including assessment of tenosynovitis in RA and enthesitis in PsA and focusing on alternative MRI techniques.

CONCLUSION

MRI has been further developed and validated as an outcome measure in RA, PsA, and OA. The group will continue its efforts to optimize the value of MRI as a robust biomarker in rheumatology clinical trials.

MRI pattern of arthritis in systemic lupus erythematosus: a comparative study with rheumatoid arthritis and healthy subjects

OBJECTIVE

In this study we aimed to describe the magnetic resonance imaging (MRI) pattern of the distribution of bone marrow edema (BME) and joint erosion in hands and wrists of patients with systemic lupus erythematosus (SLE) with arthritis in comparison with rheumatoid arthritis (RA) and healthy subjects (H).

METHODS

SLE patients with arthritis (n = 50), patients with RA (n = 22), and H (n = 48) were enrolled. Every patient underwent a non-dominant hand (2nd-5th metacarpophalangeal joints) and wrist MRI without contrast injection with a low-field extremity dedicated 0.2-Tesla instrument.

RESULTS

BME was observed in two SLE patients in the hand (4%) and in 15 in the wrist (13%) versus three (30%), and 14 (63%) RA patients. No BME was found in H. Erosions were observed in the hand in 24 SLE patients (48%), 15 RA patients (68%), and 9 H (18 %); in the wrist, in 41 (82%) SLE, all RA and 47 (97%) H. The cumulative erosive burden in SLE was significantly higher than in H (c = 0.002) but similar to RA patients.

CONCLUSIONS

Joint involvement of the wrist in SLE is similar to RA and is not as rare as expected, as shown by the comparison with healthy subjects. On the contrary, the involvement of the hand in SLE is significantly lower compared to RA.

Detection of Subclinical Synovitis with Macrophage Targeting and Positron Emission Tomography in Patients with Rheumatoid Arthritis without Clinical Arthritis

Objective.

To determine whether macrophage targeting by (R)-11C-PK11195 positron emission tomography (PET) can visualize subclinical joint inflammation in patients with rheumatoid arthritis (RA) without clinical arthritis during or after treatment, with flare as clinical outcome measure.

Methods.

(R)-11C-PK11195 PET and contrast-enhanced magnetic resonance imaging (MRI) of hands/wrists were performed in 29 patients with RA without clinical arthritis. (R)-11C-PK11195 PET uptake (semiquantitative score 0–3) in metacarpophalangeal, proximal interphalangeal, and wrist joints (i.e., 22 joints per patient) was scored and summed to obtain a cumulative PET score (range 0–66). Rheumatoid Arthritis Magnetic Resonance Imaging Scoring (RAMRIS) was performed on similar joints. Synovitis and bone marrow edema scores (> 1) were summed to obtain a cumulative MRI score (range 0–288). Occurrence of flare was determined during 3-year followup.

Results.

Flare was observed in 17/29 patients (59%). (R)-11C-PK11195 PET showed enhanced tracer uptake in 16/29 patients (55%), of which 11 (69%) developed a flare. Highest cumulative PET scores (> 6, n = 3) corresponded with highest cumulative MRI scores (> 39) and were related to development of flare in hands/wrists within 6 months. Cumulative PET scores of patients developing a flare were higher than those of patients without a flare [median (interquartile range) 2 (0–4.5) vs 0 (0–1), p < 0.05]. In contrast, no significant differences were found between cumulative MRI scores of patients with and without a flare.

Conclusion.

(R)-11C-PK11195 PET showed enhanced uptake, pointing to presence of subclinical synovitis in over half of patients without clinical arthritis. (R)-11C-PK11195 PET may be of value for prediction of exacerbation of RA, since cumulative PET scores > 1 were associated with development of flare within 3 years.

The role of imaging in the evaluation of joint involvement in 102 consecutive patients with systemic lupus erythematosus

OBJECTIVE

To assess the prevalence of joint involvement in consecutive patients with systemic lupus erythematosus (SLE) by means of clinical assessment, joint US and MRI and to evaluate the sensitivity and specificity of physician evaluation of joint involvement.

METHODS

At enrollment, patients underwent a complete physical examination including a 44-joint count, and hand deformities were scored. On the day of enrollment, each patient underwent a non-dominant hand-wrist ultrasound (US) examination and a non-dominant hand-wrist MRI study without contrast injection.

RESULTS

One hundred and two patients (F 95, M 7) were enrolled. By physician examination hand or wrist involvement was diagnosed in 23.5%. At least one pathological finding was revealed by US examination at wrist and/or hand joints in 55%. We found a low sensitivity (46.5%) with high specificity (93.2%) of the physician assessment for the evaluation of joint involvement. The MRI imaging showed at least one erosion in 47.3% patients at the hand and in 98.9% at the wrist; in healthy subjects erosions were found in 19.6% and 97.8% at the hand and wrist, respectively.

CONCLUSIONS

In conclusion, (i) physicians tend to underestimate the severity of joint involvement in SLE; (ii) US assessment shows a high prevalence of joint and tendon involvement; and (iii) the MRI evaluation shows a high prevalence of damage, suggesting that joint involvement in SLE could be more severe than expected.

Insights into rheumatoid arthritis from use of MRI

Magnetic resonance imaging (MRI) is ideal for imaging the joints of rheumatoid arthritis (RA) patients. It produces anatomically detailed images of bone, cartilage, tendons and synovial membrane. It can reveal structural damage, in the form of bone erosion, cartilage thinning and/or tendon rupture, and regions of inflammation, using sequences that reveal water content and vascularity. MRI synovitis, tenosynovitis and bone oedema/osteitis all have prognostic significance, and MRI studies of RA have helped elucidate the mechanisms whereby bone and synovial inflammation lead to joint damage. Bone oedema/osteitis has become an important imaging biomarker, and can be used to help predict progression from undifferentiated arthritis to definite RA. Recent MRI studies have confirmed that subclinical inflammation is often present in patients in clinical remission, and these data may affect disease management. Finally, recent clinical trials are reviewed, in which MRI outcome measures are being established as sensitive response markers.

A study of erosive phenotypes in lupus arthritis using magnetic resonance imaging and anti-citrullinated protein antibody, anti-RA33 and RF autoantibody status

OBJECTIVES

The aims of this study were to investigate the extent of MRI-determined joint disease (erosion and synovitis) in SLE and to link this to autoantibody profiles known to be relevant to SLE, including ACPA, RF and anti-RA33 antibodies.

METHODS

Contrast-enhanced MRI of the hand and wrist was performed in 34 symptomatic SLE patients and in 15 RA patients with similar disease duration. Images were scored by two observers using the OMERACT rheumatoid arthritis MRI scoring (RAMRIS) system. Findings were correlated with clinical examination and autoantibody status.

RESULTS

Erosions were present at the wrist in 93% of SLE patients and at the MCP joints in 61% of SLE patients. Despite the high prevalence of MRI-determined erosion, only 8.8% of SLE patients were ACPA positive, although these patients had a higher burden of erosive disease. There was no positive correlation with anti-RA33 titres and erosion scores in the SLE patients, but there was a negative correlation with anti-RA33 titres and total bone oedema scores in the SLE patients. Ninety-three per cent of SLE patients had at least grade 1 synovitis at one or more MCP joints, and wrist joint synovitis was present in all the SLE patients.

CONCLUSION

An MRI-determined joint erosive phenotype is common in SLE, even in ACPA-negative cases. The conventional radiographic observation that anti-RA33 is not positively associated with erosion in patients with RA was also found to be the case in SLE patients.

Synovial explant inflammatory mediator production corresponds to rheumatoid arthritis imaging hallmarks: a cross-sectional study

Introduction

Despite the widespread use of magnetic resonance imaging (MRI) and Doppler ultrasound for the detection of rheumatoid arthritis (RA) disease activity, little is known regarding the association of imaging-detected activity and synovial pathology. The purpose of this study was to compare site-specific release of inflammatory mediators and evaluate the corresponding anatomical sites by examining colour Doppler ultrasound (CDUS) and MRI scans.

Methods

RA patients were evaluated on the basis of CDUS and 3-T MRI scans and subsequently underwent synovectomy using a needle arthroscopic procedure of the hand joints. The synovial tissue specimens were incubated for 72 hours, and spontaneous release of monocyte chemoattractant protein 1 (MCP-1), interleukin 6 (IL-6), macrophage inflammatory protein 1β (MIP-1β) and IL-8 was measured by performing multiplex immunoassays. Bone marrow oedema (BME), synovitis and erosion scores were estimated on the basis of the rheumatoid arthritis magnetic resonance imaging score (RAMRIS). Mixed models were used for the statistical analyses. Parsimony was achieved by omitting covariates with P > 0.1 from the statistical model.

Results

Tissue samples from 58 synovial sites were obtained from 25 patients. MCP-1 was associated with CDUS activity (P = 0.009, approximate Spearman’s ρ = 0.41), RAMRIS BME score (P = 0.01, approximate Spearman’s ρ = 0.42) and RAMRIS erosion score (P = 0.03, approximate Spearman’s ρ = 0.31). IL-6 was associated with RAMRIS synovitis score (P = 0.04, approximate Spearman’s ρ = 0.50), BME score (P = 0.04, approximate Spearman’s ρ = 0.31) and RAMRIS erosion score (P = 0.03, approximate Spearman’s ρ = 0.35). MIP-1β was associated with CDUS activity (P = 0.02, approximate Spearman’s ρ = 0.38) and RAMRIS synovitis scores (P = 0.02, approximate Spearman’s ρ = 0.63). IL-8 associations with imaging outcome measures did not reach statistical significance.

Conclusions

The association between imaging activity and synovial inflammatory mediators underscores the high sensitivity of CDUS and MRI in the evaluation of RA disease activity. The associations found in our present study have different implications for synovial mediator releases and corresponding imaging signs. For example, MCP-1 and IL-6 were associated with both general inflammation and bone destruction, in contrast to MIP-1β, which was involved solely in general synovitis. The lack of association of IL-8 with synovitis was likely underestimated because of a large proportion of samples above assay detection limits among the patients with the highest synovitis scores.

Subclinical inflammation on MRI of hand and foot of anticitrullinated peptide antibody-negative arthralgia patients at risk for rheumatoid arthritis

Introduction

It is known that anticitrullinated peptide antibody (ACPA)–positive rheumatoid arthritis (RA) has a preclinical phase. Whether this phase is also present in ACPA-negative RA is unknown. To determine this, we studied ACPA-negative arthralgia patients who were considered prone to progress to RA for local subclinical inflammation observed on hand and foot magnetic resonance imaging (MRI) scans.

Methods

We studied a total of 64 ACPA-negative patients without clinically detectable arthritis and with arthralgia of the small joints within the previous 1 year. Because of the character of the patients’ symptoms, the rheumatologists considered these patients to be prone to progress to RA. For comparisons, we evaluated 19 healthy, symptom-free controls and 20 ACPA-negative RA patients, who were identified according to the 1987 American Rheumatism Association criteria. All participants underwent MRI of unilateral wrist, metacarpophalangeal and metatarsophalangeal joints. Synovitis and bone marrow oedema (BME) were scored according to the OMERACT rheumatoid arthritis magnetic resonance imaging scoring system, and the scores were summed to yield the ‘MRI inflammation score’. Scores were compared between groups. Among the ACPA-negative arthralgia patients, MRI inflammation scores were related to C-reactive protein (CRP) levels and the tenderness of scanned joints.

Results

MRI inflammation scores increased progressively among the groups of controls and ACPA-negative arthralgia and RA patients (median scores = 0, 1 and 10, respectively; P < 0.001). The MRI inflammation scores of ACPA-negative arthralgia patients were significantly higher than those of controls (P = 0.018). In particular, the synovitis scores were higher in ACPA-negative arthralgia patients (P = 0.046). Among the ACPA-negative arthralgia patients, inflammation was observed predominantly in the wrist (53%). The synovitis scores were associated with CRP levels (P = 0.007) and joint tenderness (P = 0.026). Despite the limited follow-up duration, five patients developed clinically detectable arthritis. These five patients had higher scores for MRI inflammation (P = 0.001), synovitis (P = 0.002) and BME (P = 0.003) compared to the other patients.

Conclusion

Subclinical synovitis was observed in the small joints of ACPA-negative arthralgia patients, and especially in patients whose conditions progressed to clinically detectable arthritis. This finding suggests the presence of a preclinical phase in ACPA-negative RA. Further longitudinal studies of these lesions and patients are required to confirm this hypothesis.

Characterising arthralgia in the preclinical phase of rheumatoid arthritis using MRI

BACKGROUND

The phase of arthralgia is the earliest moment to clinically recognize patients who may develop Rheumatoid Arthritis (RA). Previous imaging studies in the arthralgia phase have shown that inflammation precedes RA development. It is unknown which symptoms/characteristics relate to subclinical joint inflammation as measured by MRI. Among all patients with arthralgia, those with clinically suspect arthralgia (CSA) are suspected to progress to arthritis according to the clinical judgement of their rheumatologists. We determined the symptoms/characteristics of patients with CSA who had inflammation on MRI.

METHODS

102 patients with CSA and without clinical arthritis were included. They completed questionnaires, underwent joint counts and unilateral 1.5 T MRI of MCP joints 2-4, wrist and MTP joints 1-5. Synovitis, bone marrow oedema (BME) and tenosynovitis were scored according to the OMERACT rheumatoid arthritis MRI scoring system. Symptoms and signs were related to MRI inflammation (based on MRI scores in symptom-free controls; a sum of synovitis, BME and tenosynovitis scores ≥3 was considered positive). Whether certain clinical characteristics frequently occurred together with MRI inflammation was studied by partial least squares analysis.

RESULTS

MRI was performed in 93 patients with CSA, 44% of whom had subclinical MRI inflammation. Synovitis was the most prevalent inflammatory feature on MRI (20%). Patients with MRI inflammation were older and were more frequently positive for anti-citrullinated peptide antibodies than patients without MRI inflammation (p<0.001 and 0.049). In PLS analysis, including 16 clinical and serological characteristics as independent variables and MRI inflammation as dependent variable, no clear clusters of patients with and without MRI inflammation were identified.

CONCLUSIONS

Subclinical inflammation as measured by MRI is present in 44% of patients with CSA. A combination of symptoms/characteristics incompletely differentiated patients with and without MRI inflammation.

MRI in rheumatoid arthritis: a useful tool for the clinician?

Over the last two decades, MRI has emerged as an important clinical tool to assist in the diagnosis and management of rheumatic disease. In rheumatoid arthritis (RA), MRI has improved our understanding of the pathological basis of disease and has provided new information about imaging features that reflect joint inflammation and damage. Using MRI, we can now directly observe inflammation involving the synovial membrane and tenosynovium, plus joint damage including bone erosion and cartilage thinning. Inflammation of bone beneath the joint (osteitis) appears as bone oedema which is a feature unique to MRI and yields important diagnostic and prognostic information in patients with inflammatory arthritis. With the introduction of biologics to rheumatology clinical practice, sensitive tools are required to monitor disease activity and progression, so that the disease suppressing effect of these new agents can be measured. MRI fits the bill for this role as it can inform the clinician about the development of bone erosions well before plain radiography, and its ability to reveal cartilage damage is emerging. The use of MRI as a marker of outcome in clinical trials is being paralleled by its increasing role in the clinic. Both extremity and high field MRI have clinical applications in RA and need to be considered along with other advanced imaging techniques as useful tools to add to the clinician's armamentarium. This review will summarise recent advances in this field and will apply current knowledge to specific clinical scenarios relevant to modern rheumatology practice.

Advantages of a combined rheumatoid arthritis magnetic resonance imaging score (RAMRIS) for hand and feet: does the RAMRIS of the hand alone underestimate disease activity and progression?

Background

To evaluate a combined rheumatoid arthritis magnetic resonance imaging score (RAMRIS) for hand and foot (HaF-score) in rheumatoid arthritis (RA).

Methods

Magnetic resonance imaging (MRI, 0.2 Tesla) of the dominant hand and foot of 26 ACPA positive RA patients before and 6 months after initiation of methotrexate was obtained. RAMRIS of the hand was complemented by corresponding scoring of the foot (MTP I-V; HaF-score). Disease Activity Score 28 (DAS28) and a tender and swollen joint count (JC) of the joints scored in MRI were recorded. Changes in these scores (Δ) were assessed.

Results

ΔHaF-score correlated significantly with ΔDAS28 (r = 0.820, 95%-CI 0.633-0.916). Correlations to ΔDAS28 were best for changes in the synovitis subscore (0.648) and bone marrow edema (0.703). Correlations to ΔDAS28 were significantly better for of the ΔHaF-score than ΔRAMRIS (0.499, 0.139-0.743, p = 0.0368).

All patients with at least moderate response (EULAR criteria, n = 11) had continuing disease activity on MRI, including five cases with new erosions, three of them at the feet. Improvements of the hand JC or foot JC were seen in 16 and 15 cases, respectively. However, MRI of the hand or feet improved in only 10 and 9 cases, respectively. No patient fulfilled SDAI remission criteria.

Conclusions

The HaF-score identifies patients with continuing disease activity despite clinical response that would have been missed by consideration of the traditional RAMRIS or the DAS28 alone. Response as opposed to remission may be an insufficient goal in RA as all patients showed continuing disease activity, especially at the feet.

Bone marrow oedema assessment by magnetic resonance imaging in rheumatoid arthritis wrist and metacarpophalangeal joints: the importance of field strength, coil type and image resolution

OBJECTIVE

The aim of this study was to examine the influence of different MRI unit field strengths, coil types and image resolutions on the OMERACT RA MRI scoring system (RAMRIS) of bone marrow oedema (BME) and image quality.

METHODS

Forty-one patients and 12 healthy controls participated in this cross-sectional study. Coronal short tau inversion recovery (STIR) and T1-weighted sequences were obtained at 0.23, 0.6, 1.5 and 3T using flex coils (Flex). Additional STIR sequences were obtained with phased array extremity coils (Extr) (at 0.6 and 1.5T) and higher resolution (at 1.5T). In otal, 338 STIR image sets were anonymized and scored according to RAMRIS and parameters of image quality were measured.

RESULTS

The BME sum scores were similar overall when comparing the different MRI units, coil types and voxel sizes, yet significantly higher at the higher resolution of 1.5T Extr compared with 0.23T Flex (P = 0.004), 0.6T Flex (P = 0.03), 1.5T Flex (P = 0.05) and 3T Flex (P = 0.001). Mean differences were relatively minor (0-3.5). Intrareader reliability of BME scores was high [intraclass correlation coefficient ≥ 0.90 for all except 0.23T (0.81) and percentage exact agreement 81-88%]. The smallest detectable difference was better at 0.6, 1.5 and 3T (9-29% of maximum value) than at 0.23T (40%). Image quality was lowest at 0.23T.

CONCLUSION

No major, consistent differences were found between BME scores using STIR sequences obtained at different field strengths, coil types and image resolutions, suggesting that these are equally suited for assessment of BME in RA. However, parameters of image quality and intrareader reliability (favouring 0.6, 1.5 and 3T) should be considered when selecting the MRI acquisition strategy.

Imaging of rheumatoid arthritis

Increased awareness of the need for early diagnosis of rheumatoid arthritis and advances in the ability to effectively treat rheumatoid arthritis have made disease remission and maintenance of function a reality for many patients. However, identification of patients who are at risk for erosive disease remains a challenge. As more is learnt about risk factors for disease severity and the role of imaging techniques such as ultrasound and magnetic resonance imaging, the ability to prevent disease progression in the form of joint damage and its attendant deformity and functional limitation will further improve.

Evaluating processes underlying the predictive value of baseline erosions for future radiological damage in early rheumatoid arthritis

OBJECTIVES

Baseline erosions are characteristic for rheumatoid arthritis (RA) and predictive for a severe disease course. The mechanisms leading to baseline erosions being a strong predictor for radiological progression are unknown. We aimed to increase this understanding by mediation analyses in an observational cohort and a cross-sectional MRI study.

METHODS

3256 hands and feet radiographs of 653 early RA patients assessed during 7 years of disease were scored using the Sharp-van der Heijde method. Mediation models and multivariate regression analyses were used to explore the association between baseline erosions, other predictors and radiological damage over time. 603 joints (MCP2-5 and MTP1-5) of 67 RA patients underwent 1.5 T MRI at baseline. Data on MRI inflammation were compared with clinical inflammation and baseline radiological erosions.

RESULTS

Patients with baseline erosions had, at any point in time during 7 years, 3.45 times more joint damage than patients without erosions (p<0.001, 95% CI 3.00 to 3.98). Baseline erosions were an independent predictor and not a mediator between symptom duration, systemic or local clinical inflammation (erythrocyte sedimentation rate (ESR), swollen joint count (SJC)) or autoantibodies (anti-citrullinated-peptide antibodies, rheumatoid factor) and radiological damage. Subclinical MRI inflammation was studied in relation to erosions, revealing that 83% of the non-swollen joints with baseline erosions had subclinical MRI inflammation compared with 25% of the non-swollen joints without baseline erosions (OR 15.2 95% CI 3.1 to 102.1). The association between MRI inflammation and baseline erosions was independent of symptom duration, ESR, SJC and autoantibodies.

CONCLUSIONS

Baseline erosions are a predictor for future joint damage, independent of known predictors as time, autoantibodies or clinical measurable inflammation. Subclinical inflammation is suggested as an underlying mechanism.

Concordance between inflammation at physical examination and on MRI in patients with early arthritis

BACKGROUND

MRI is increasingly used to measure inflammation in rheumatoid arthritis (RA) research, but the correlation to clinical assessment is unexplored. This study determined the association and concordance between inflammation of small joints measured with MRI and physical examination.

METHODS

179 patients with early arthritis underwent a 68 tender joint count and 66 swollen joint count and 1.5T MRI of MCP (2-5), wrist and MTP (1-5) joints at the most painful side. Two readers scored synovitis and bone marrow oedema (BME) according to the OMERACT RA MRI scoring method and assessed tenosynovitis. The MRI data were first analysed continuously and then dichotomised to analyse the concordance with inflammation at joint examination.

RESULTS

1790 joints of 179 patients were studied. Synovitis and tenosynovitis on MRI were independently associated with clinical swelling, in contrast to BME. In 86% of the swollen MCP joints and in 92% of the swollen wrist joints any inflammation on MRI was present. In 27% of the non-swollen MCP joints and in 66% of the non-swollen wrist joints any MRI inflammation was present. Vice versa, of all MCP, wrist and MTP joints with inflammation on MRI 64%, 61% and 77%, respectively, were not swollen. BME, also in case of severe lesions, occurred frequently in clinically non-swollen joints. Similar results were observed for joint tenderness.

CONCLUSIONS

Inflammation on MRI is not only present in clinically swollen but also in non-swollen joints. In particular BME occurred in clinically non-inflamed joints. The relevance of subclinical inflammation for the disease course is a subject for further studies.

MRI of the wrist in juvenile idiopathic arthritis: erosions or normal variants? A prospective case-control study

BACKGROUND

Bony depressions at the wrist resembling erosions are frequently seen on MRI in healthy children. The accuracy of MRI in detecting early bony destruction is therefore questionable. We compared findings on MRI of the wrist in healthy children and those with juvenile idiopathic arthritis (JIA) to investigate markers for true disease.

MATERIALS AND METHODS

We compared the number and localisation of bony depressions at the wrist in 85 healthy children and 68 children with JIA, ages 5-15 years. The size of the wrist was assessed from a radiograph of the wrist performed on the same day as the MRI.

RESULTS

No significant difference in the number of bony depressions in the carpal bones was seen between healthy children and children with JIA at any age. Depressions are found in similar locations in the two groups, except for a few sites, where bony depressions were seen exclusively in the JIA group, particularly at the CMC joints. The wrist was significantly smaller in children with JIA (P < 0.001).

CONCLUSIONS

Using adult scoring systems and standard MR sequences in the assessment of bone destruction in children may lead to overstaging or understaging of disease. At present, standard MRI sequences cannot easily be used for assessment of early signs of erosions in children.

Osteitis and synovitis, but not bone erosion, is associated with proteoglycan loss and microstructure damage in the cartilage of patients with rheumatoid arthritis

OBJECTIVES

To investigate the relation between anatomic changes of the synovium, the bone, the bone marrow and the cartilage to biochemical properties of the cartilage in patients with rheumatoid arthritis (RA).

METHODS

33 patients with RA received 3-T MRI scans of the metacarpophalangeal joints. Two independent methods, (A) the delayed gadolinium enhanced MRI of the cartilage (dGEMRIC, T2-mapping), which was used to assess the biochemical properties of the cartilage; (B) synovitis, osteitis and bone erosions were quantified according to the RA MRI scoring (RAMRIS) method and cartilage thickness (CT), interbone joint space (IBJS, distance between proximal and distal bone surface) and intercartilage joint space (ICJS, distance between proximal and distal cartilage surface) were measured.

RESULTS

Biochemical changes of the cartilage, corresponding to low dGEMRIC and high T2 values, were more likely to be seen in joints with decreased IBJS and ICJS as well as decreased CT. For instance, dGEMRIC was directly correlated to the IBJS (p=0.001) and ICJS (p=0.001), whereas T2 mapping was inversely correlated to IBJS and ICJS (both p=0.017). Moreover, the degree of osteitis, and to some extent synovitis, was correlated to biochemical cartilage changes as measured by dGEMRIC (p=0.003) or the T2 mapping (p=0.013). By contrast, bone erosions did not correlate to the degree of biochemical cartilage changes.

DISCUSSION

These data support the concept that synovitis and osteitis may be two main triggers for cartilage damage. Thus, the actual inflammatory state of a joint, but not so much the degree of bone erosion, appears to influence cartilage properties in RA.

Should modern imaging be part of remission criteria in rheumatoid arthritis?

With recent improvements in the treatment of rheumatoid arthritis (RA), remission has become an achievable goal for a large proportion of RA patients, and remission is now a defined target in current RA guidelines. However, studies have shown that progression of radiographic joint damage may occur in clinical remission, regardless of the choice of remission definition. Sub-clinical inflammation detected by modern imaging techniques such as ultrasonography and magnetic resonance imaging is present in the majority of patients in clinical remission, and is associated with progressive joint damage and disease activity flare in these patients. This chapter aims to assess the importance of imaging findings in RA patients in clinical remission and to discuss the possible role of modern imaging in future remission criteria.

Magnetic resonance imaging versus musculoskeletal ultrasonography in detecting inflammatory arthropathy in systemic sclerosis patients with hand arthralgia

The aim of the study was the detection of inflammatory arthropathy in patients with systemic sclerosis (SSc) with arthralgia using musculoskeletal ultrasonography (MSUS) and magnetic resonance imaging (MRI) and to compare between MRI versus MSUS detecting musculoskeletal abnormalities and find out its relation with other clinical and laboratory parameters. Sixteen SSc patients with hand arthralgia had a baseline MSUS for their hands. Six months later, patients had a second MSUS and MRI with gadolinium of their most symptomatic hand. Of the 16 patients examined by MSUS, it was found that on baseline and second examination, tenosynovitis was seen in 8 (50 %) and 7 (43.7 %) patients and synovitis was seen in 4 (25 %) and 5 (31 %) patients, respectively, indicating persistence synovial inflammation, and erosion was seen in only 1 (6.3 %) patient on baseline and second examination. Regarding MRI, 81.3 % (13) patients had tenosynovitis, 87.5 % (14) patients had synovitis, and 62.5 % (10) patients had erosions. Applying the RAMRIS system (a semiquantitative MRI scoring system used in RA), the mean values for synovitis, bone marrow edema, and erosions fell within the range seen in RA. Systemic sclerosis patients with arthralgia that have no obvious clinical inflammatory arthritis were found to have persistent inflammatory erosive arthropathy in their hands and wrists using MSUS and MRI. While both MRI and MSUS are useful in characterizing synovial inflammation in SSc, MRI is clearly more sensitive than MSUS in this setting. Further studies on larger number of SSc patients with arthralgia and a control group consisting of SSc patients without arthralgia to better establish the clinical and radiological findings in SSc.

Comparison of OMERACT-RAMRIS scores and computer-aided dynamic magnetic resonance imaging findings of hand and wrist as a measure of activity in rheumatoid arthritis

The purpose of this study was to compare the value of conventional magnetic resonance imaging (MRI) finding of rheumatoid arthritis (RA) and computer-aided dynamic MRI measurements in predicting the activity of disease. The activity of the disease in 40 RA patients was evaluated by the disease activity score in 28 joints (DAS28). The conventional MRI of the wrists of all patients were scored for bone edema, synovitis and erosions, according to the criteria of RA-MRI scoring system (RAMRIS) developed by Outcome measures in rheumatology clinical trials (OMERACT) MR Imaging Group. Synovitis was also quantified by dynamic postcontrast MRI imaging using color coded maximum slope of increase maps and measurements of early enhancement rate (EER) and relative enhancement (RE). Twenty-two (55 %) patients with a score higher than 5.1 constituted the high disease activity group, 18 (45 %) patients with a score of 5.1 or less constituted moderate disease activity group. The dynamic MRI-EER score was the most significant parameter to differentiate between the groups (p = 0.001). Among OMERACT scores, only bone edema [p = 0.020 for wrist and p = 0.037 for metacarpophalangeal joints (MCP)] had a significant difference between the two groups. Dynamic MRI RE score and OMERACT scores for erosions and synovitis for both the wrist and MCP joints did not differ significantly between the two groups. Computer-aided dynamic MRI is a reliable, noninvasive method of evaluating the RA patients, which correlates with the DAS28 scores, at a higher significance than the OMERACT-RAMRIS scores.

Patterns of magnetic resonance imaging of the foot in rheumatoid arthritis: which joints are most frequently involved?

To investigate patterns of inflammatory MRI pathologies of the fore- and midfoot in rheumatoid arthritis (RA) and early RA (ERA) and their changes under therapy. In this prospective study, MRI data of the foot of 39 RA patients (29 female, 10 male; age: 54 ± 13 years; disease duration: 35 ± 37 months; baseline DAS28: 3.0 ± 2.0; medication: 29 DMARD, 1 biological, 9 symptomatic or non-specific treatment) were evaluated for synovitis in 314 joints, bone marrow edema and erosions according to RAMRIS criteria in a total of 585 joints. The change in joint pathology intensity was evaluated on follow-up MRI (time of follow-up: 8 ± 4 months) in 25 patients. Inflammation was generally more frequent in the metatarsophalangeal (MTP) joints (221/292; 76 %) than in the proximal metatarsal (47/292; 16 %) and tarsal bones (24/292; 8 %). The overall most frequently involved joints of the foot were MTP 5 (51/292; 18 %) and 1 (49/292; 17 %). Change under therapy was most frequently seen in the MTP 1 joint. Progress of inflammation in the MTP 1 was more frequently found in ERA patients than in patients with established RA (disease duration >12 months) (p = 0.002). In RA, the MTP joints, primarily MTP 5 and 1, are the predominant sites of inflammatory MRI pathologies of the foot. A change of inflammatory activity under therapy can be most frequently noted in the MTP 1 joint. This information might be helpful to improve effectiveness of MRI-controlled therapy approaches and clinical trials.

MRI findings of treated bacterial septic arthritis

INTRODUCTION

The purpose of this study was to report the MRI findings that can be encountered in successfully treated bacterial septic arthritis.

MATERIALS AND METHODS

The study included 12 patients (8 male and 4 female; mean age 38 years, range 9-85) with 13 proven cases of bacterial septic arthritis. The joints involved were hip (n = 3), knee (n = 3), shoulder (n = 2), sacroiliac (n = 2), ankle (n = 1), wrist (n = 1), and elbow (n = 1). MRI examinations following surgical debridement and at initiation of antibiotic therapy and after successful treatment were compared for changes in effusion, synovium, bone, and periarticular soft tissues. Imaging findings were correlated with microbiological and clinical findings.

RESULTS

Joint effusions were present in all joints at baseline and regressed significantly at follow-up MRI (p = 0.001). Abscesses were present in 5 cases (38 %), and their sizes decreased significantly at follow-up (p = 0.001). Synovial enhancement and thickening were observed in all joints at both baseline and follow-up MRI. Myositis/cellulitis was present in 10 cases (77 %) at baseline and in 8 cases (62 %) at follow-up MRI. Bone marrow edema was present in 10 joints (77 %) at baseline and persisted in 8 joints (62 %). Bone erosions were found in 8 joints (62 %) and persisted at follow-up MRI in all cases.

CONCLUSION

The sizes of joint effusions and abscesses appear to be the factors with the most potential for monitoring therapy for septic arthritis, since both decreased significantly following successful treatment. Synovial thickening and enhancement, periarticular myositis/cellulitis, and bone marrow edema can persist even after resolution of the infection.