Computerized measurement of magnetic resonance imaging erosion volumes in patients with rheumatoid arthritis: a comparison with existing magnetic resonance imaging scoring systems and standard clinical outcome measures

Computer‐Assisted Image Analysis in Assessment of Peripheral Joint MRI in Inflammatory Arthritis: A Systematic Review and Meta‐analysis

Objective

To summarize the feasibility of computer‐assisted quantification of joint pathologies on magnetic resonance imaging (MRI) in patients with inflammatory arthritis by evaluating the published data on reliability, validity, and feasibility.

Methods

A systematic literature search was performed for original articles published from January 1, 1985, to January 1, 2021. We selected studies in which patients with inflammatory arthritis were enrolled, and arthritis‐related structural damage/synovitis in peripheral joints was assessed on non‐contrast‐enhanced, contrast‐enhanced (CE), or dynamic CE (DCE)‐MRI using (semi)automated methods. Data were pooled using random‐effects model.

Results

Twenty‐eight studies consisting of 1342 MRIs were included (mean age, 54.8 years; 66.7% female; duration of arthritis, 3.6 years). Among clinical/laboratory factors, synovial membrane volume (SV) was moderately correlated with erthrocyte sedimentation rate (ESR) level (P < 0.01). Pooled analysis showed an overall excellent intra‐ and inter‐reader reliability for computer‐aided quantification of bone erosion volume (BEV; r = 0.97 [95% CI: 0.92‐0.99], 0.93 [0.87‐0.97]), SV (r = 0.98 [95% CI: 0.90‐0.99], 0.86 [0.78‐0.91]), and DCE‐MRI perfusion parameters (r = 0.96‐0.99). Meta‐regression showed that computer‐aided and manual methods provide comparable reliability (P > 0.05). Computer‐aided measurement of BEV (r = 0.92), SV (r = 0.82), and DCE‐MRI biomarkers (r = 0.72 N‐total; r = 0.74 N‐plateau; r = 0.64 N‐washout) were significantly correlated with the Rheumatoid Arthritis Magnetic Resonance Imaging Score (RAMRIS; P < 0.01), allowing for earlier assessment of drug efficacy. On average, (semi)automated analysis of BEV/SV took 17 minutes (vs. 9 minutes for the RAMRIS) and DCE‐MRI took 4 minutes (vs. 33 minutes for manual assessment).

Conclusion

Computer‐aided image quantification technologies demonstrate excellent reliability and validity when used to quantify MRI pathologies of peripheral joints in patients with inflammatory arthritis. Computer‐aided evaluation of inflammatory arthritis is an emerging field and should be considered as a viable complement to conventional observer‐based scoring methods for clinical trials application.

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.

Registration-Based Morphometry for Shape Analysis of the Bones of the Human Wrist

We present a method that quantifies point-wise changes in surface morphology of the bones of the human wrist. The proposed method, referred to as Registration-based Bone Morphometry (RBM), consists of two steps: an atlas selection step and an atlas warping step. The atlas for individual wrist bones was selected based on the shortest ℓ2 distance to the ensemble of wrist bones from a database of a healthy population of subjects. The selected atlas was then warped to the corresponding bones of individuals in the population using a non-linear registration method based on regularized ℓ2 distance minimization. The displacement field thus calculated showed local differences in bone shape that then were used for the analysis of group differences. Our results indicate that RBM has potential to provide a standardized approach to shape analysis of bones of the human wrist. We demonstrate the performance of RBM for examining group differences in wrist bone shapes based on sex and between those of the right and left wrists in healthy individuals. We also present data to show the application of RBM for tracking bone erosion status in rheumatoid arthritis.

Assessing the Reliability of a Semiautomated Segmentation Algorithm for Quantifying Erosions in the Metacarpophalangeal Joints of Patients with Rheumatoid Arthritis

OBJECTIVE

Assess the reliability of early erosions in rheumatoid arthritis (EERA) software for quantifying erosive damage to the metacarpophalangeal joints of patients with rheumatoid arthritis (RA).

METHODS

One hundred magnetic resonance image sets from 68 patients with early referral RA were evaluated. Reliability was assessed using 95% limits of agreement and intraclass correlation coefficient (ICC) with 95% CI.

RESULTS

Limits of agreement linearly depended on erosion volume: 0.44× between readers and 0.19× within readers. Interrater ICC was 0.976 (95% CI 0.965-0.984) and intrarater ICC was 0.996 (95% CI 0.994-0.997).

CONCLUSION

EERA is highly reproducible for quantifying erosions in patients with early RA.

Methods of assessment of tophus and bone erosions in gout using dual-energy CT: reproducibility analysis

This study aims to evaluate the intraobserver and interobserver reproducibility of the tophus urate volume, erosion volume, and the erosion score measurements in patients with gout by using dual-energy CT (DECT) scans comparing their bone erosion volumes against bone erosion scores and also to determine a valid measure of joint destruction in chronic gout. Sixty-six subjects underwent DECT scans of the hands or feet. Two independent observers measured the tophus urate volumes and bone erosion volumes using automated volume assessment software and the erosion scores based on the rheumatoid arthritis magnetic resonance imaging score (RAMRIS). The intraobserver and interobserver reproducibility were analyzed by intraclass correlation coefficient (ICC) and limits of agreements analysis. The relationship between erosion volumes and erosion scores was analyzed. The intraobserver and interobserver ICC for tophus urate volume measurements (n = 636) were 1.000 (95 % confidence interval (95 % CI) 1.000 to 1.000) and 1.000 (95 % CI 1.000 to 1.000), 0.999 (0.999, 0.999) and 0.999 (0.999, 0.999) for bone erosion volumes (n = 350), 0.937 (0.928, 0.946) and 0.899 (0.883, 0.912) for erosion scores (n = 350). Strong positive correlations were demonstrated between individual erosion volumes and scores (r s = 0.914, p < 0.001) as well as total erosion volume and score per patient (r = 0.838-0.867, p < 0.001). This study demonstrated a high reproducibility of tophus urate volumes, erosion volumes, and erosion score measurements using DECT. Erosion volumes show to be a more direct and accurate method to evaluate bone erosion compared with erosion score, strongly supporting it as a superior and standard measure of structural joint damage in gout.

Early extremity MRI findings and pathological synovial changes in antigen-induced arthritis rabbit model

PURPOSE

To investigate the association between early extremity MRI (E-MRI) findings and synovial pathological changes in antigen-induced arthritis (AIA) rabbit model.

MATERIALS AND METHODS

AIA was successfully induced in the right knee of 32 sensitized Japanese white rabbits, which were then divided into four groups according to the time of killing after AIA induction: 1-week (Group A), 2-weeks (Group B), 3-weeks (Group C), and 4-weeks (Group D); the left knee served as control in each rabbit.

RESULTS

There were varying degrees of joint effusion in all AIA groups. E-MRI scan showed low signal in T1-weighted images (T1Wi) and high signal in T2-weighted images (T2Wi). Enhanced E-MRI revealed elevated synovial signal at the right knee in the three-dimensional spoiled gradient T1WI, showing linear and band-shaped, diffuse hyperintensity. Histological examination of right knees found scattered inflammatory cell infiltration, swelling, and proliferation of the synovial cells at 7 days after AIA induction and dispersed and disordered proliferation of synovial cells up to 3 layers at 28 days postinduction. The synovial enhancement of right knee E-MRI was consistent with a synovial pathology score for all rabbits (Kappa = 0.965, P < 0.01).

CONCLUSION

E-MRI can reveal the degree of changes in the joints and synovium at different periods of the AIA model.

Validity of a computer-assisted manual segmentation software to quantify wrist erosion volume using computed tomography scans in rheumatoid arthritis

BACKGROUND

To investigate the performance of conventional radiography (CR) for the detection of bone erosions of wrist in rheumatoid arthritis (RA) using multidetector computed tomography (CT) as the reference method and to evaluate the validity of a computer-assisted manual segmentation (outlining) technique to quantify erosion volume on CT scans.

METHODS

Twenty five RA patients and six controls underwent CT and radiographic evaluation of the dominant wrist on the same day. CT was performed by using a 64 GE light Speed VCT power. Wrists images were evaluated separately and scored for the presence of erosions according to the Outcome Measures in Rheumatology Rheumatoid Arthritis MRI Scoring System (RAMRIS) and the Sharp/van der Heijde scoring method. Measurements of bone erosion volumes were obtained using OsiriX medical imaging software. The mean value of the volumes of the CT bone erosions detected at two readings was used to calculate inter-rater agreement.

RESULTS

The overall sensitivity, specificity and accuracy of radiography for detecting erosions were 25.5%, 98.3% and 70.1%, respectively. Using computer-assisted manual segmentation (outlining) technique, erosion volume on CT measurements per subject was ranged from 0.001 cm³ to 2.01 cm³. Spearman's RAMRIS score of each wrist bones in all subjects (n = 25) were correlated with the total erosion volume on CT (p < 0.0001), with the ratio between erosion volume and the corresponding bone volume on a percentage basis (p < 0.0001). The total Sharp/van der Heijde erosion score of the all wrist bones was correlate with the RAMRIS score (p = 0.008). The intraclass correlation coefficients (ICC) for manual segmentation showed high agreement (ICC = 0.901).

CONCLUSIONS

Considering CT as the reference method, CR showed very low sensitivity. A close correlation with CT erosion volumes supports the OMERACT RAMRIS erosion score as a semiquantitative measure of joint damage in RA. Although the computer-assisted manual segmentation can be beneficial for diagnostic decision in cross-sectional CT examinations of the wrist in RA, this technique will require further evaluation in terms of responsiveness.

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.

Reliability and longitudinal validity of computer-assisted methods for measuring joint damage progression in subjects with rheumatoid arthritis

OBJECTIVE

To compare the metric properties of a computer-assisted erosion segmentation volume measurement with scoring using the Rheumatoid Arthritis Magnetic Resonance Imaging Score (RAMRIS) in a longitudinal cohort of patients with rheumatoid arthritis (RA).

METHODS

Thirty-two sets of baseline and 2-year followup magnetic resonance imaging (MRI) of metacarpal phalangeal 2-5 joints of patients with RA were scored using RAMRIS and segmented using OSIRIS software. The smallest detectable difference (SDD), standardized response mean (SRM), and paired t-test were used to evaluate the sensitivity to change. Eleven of the 32 patients' MRI were segmented by both readers to evaluate interreader agreement. The 28-joint Disease Activity Score (DAS28) and Sharp erosion scores further evaluated construct and longitudinal validity.

RESULTS

Reliability of erosion progression by computer-assisted volume measurement was superior to RAMRIS [intrareader interclass correlation coefficient (ICC) 0.97 (0.94-0.99) vs 0.52 (0.22-0.73)] and interreader ICC of volume measurement was 0.85 (0.53-0.96). Computer-assisted volume measurements identified 10 of 32 patients who progressed more than the SDD progression, whereas RAMRIS identified only 4 of 32 patients (p = 0.0013). By a paired t-test, however, all MRI measures progressed significantly over 2 years (irrespective of treatment arm) and there was little difference by SRM. Construct correlational validity of the MRI methods was 0.47-0.90 for status scores and 0.33-0.81 for progression. There was no relationship between the average DAS28 and erosion progression by any imaging method.

CONCLUSION

Computer-assisted measurement of erosion volume has good performance metrics. It had excellent intrareader and interreader reliability and was more sensitive to change than RAMRIS in this group of patients. www.ClinicalTrials.gov, NCT00451971.

A simple technique for morphological measurement of cerebral arterial circle variations using public domain software (Osiris)

This article describes a straightforward method to measure the dimensions and identify morphological variations in the cerebral arterial circle using the general-purpose software program Osiris. This user-friendly and portable program displays, manipulates, and analyzes medical digital images, and it has the capability to determine morphometric properties of selected blood vessels (or other anatomical structures) in humans and animals. To ascertain morphometric variations in the cerebral arterial circle, 132 brains of recently deceased fetuses, infants, and adults were dissected. The dissection procedure was first digitized, and then the dimensions were measured with Osiris software. Measurements of each vessel's length and external diameters were used to identify and classify morphological variations in the cerebral arterial circle. The most commonly observed anatomical variations were uni- and bilateral hypoplasia of the posterior communicating artery. This study demonstrates that public domain software can be used to measure and classify cerebral arterial circle vessels. This method could be extended to examine other anatomical regions or to study other animals. Additionally, knowledge of variations within the circle could be applied clinically to enhance diagnostic and treatment specificity.

Quantifying synovitis in rheumatoid arthritis using computer-assisted manual segmentation with 3 Tesla MRI scanning

PURPOSE

To investigate the reliability, validity and feasibility of a computer-assisted manual segmentation method for determining the synovial membrane volume as a surrogate measure for synovitis in patients with rheumatoid arthritis (RA).

MATERIALS AND METHODS

The 3 Tesla (T) MRI scans were acquired in 22 early RA and 16 established RA patients. Synovial membrane volumes in postcontrast T1w axial images at three wrist joint regions were determined by two nonradiologist observers using a computer-assisted manual segmentation method.

RESULTS

Intraobserver reliability, measured by intraclass correlation coefficients (ICCs), was excellent in the early (ICC = 0.99) and established (ICC = 0.99) RA cohorts. Interobserver reliability (mean ICC [95% Confidence Interval]) was moderate to excellent in the early and established RA groups (ICCs = 0.87 [0.68,0.94] and 0.88 [0.66, 0.96], respectively). There was a strong correlation between the synovial membrane volumes derived by segmentation and the RA MRI scoring system (RAMRIS) scores for synovitis at all joints in the early (Spearman rho = 0.86-0.96) and established (Spearman rho = 0.85-0.93) RA cohorts. The entire segmentation technique took 19 to 21 min per patient.

CONCLUSION

Measurement of MRI synovitis using a computer-assisted manual segmentation method demonstrated excellent intraobserver and very good interobserver reliability, content validity (represented by its strong correlation with RAMRIS synovitis), and moderate feasibility.

Measuring bone erosion and edema in rheumatoid arthritis: a comparison of manual segmentation and RAMRIS methods

PURPOSE

To investigate the reliability, feasibility, and validity of a computer-assisted manual segmentation (outlining) technique for measuring magnetic resonance imaging (MRI) bone erosion and edema at the wrist in rheumatoid arthritis (RA).

MATERIALS AND METHODS

The 3T MRI scans were obtained in 22 RA patients (<2 years). Bone erosion and edema volumes were scored by two readers using outlining and were compared with RAMRIS scores.

RESULTS

Using outlining, intraobserver reliability for erosions and edema was high: intraclass correlation coefficients (ICCs) = 0.994 (0.991, 0.997) and 0.996 (0.994, 0.998), respectively (Reader 1). Interobserver reliability was high for bone erosion (ICC [90% confidence interval, CI] = 0.80 [0.64, 0.92]) and comparable to RAMRIS scoring (ICC 0.78 [0.64, 0.92]), but was only moderate for bone edema (0.46 [0.00, 0.96]), compared with RAMRIS (ICC = 0.84 [0.73, 0.94]). The methods were highly correlated for erosion scores, r = 0.90, 0.82 (Readers 1 and 2) and moderately correlated for edema, r = 0.57, 0.87.

CONCLUSION

Segmentation (outlining) can be used to measure the volume of MRI bone erosion and edema at the wrist in RA patients. When compared with RAMRIS scoring, outlining had similar reliability for quantifying erosions but reliability was lower for bone edema, possibly reflecting difficulty delineating the borders of affected bone.

Synovial and inflammatory diseases in childhood: role of new imaging modalities in the assessment of patients with juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) represents a group of heterogeneous diseases characterized by a chronic inflammatory process primarily targeting the synovial membrane. A persistent synovitis is associated with an increased risk of osteocartilaginous damage.With the advent of effective structure-modifying treatment for JIA, it may be possible to significantly reduce or even completely prevent structural damage and associated functional disability. The trend towards early suppression of inflammation, in order to prevent erosive disease, shifts the emphasis away from conventional radiographic detectable structural damage to the slightest traces of early joint damage, and drives the need for alternative imaging techniques more sensitive in detecting early signs of disease activity and damage. In this regard MRI and US are playing an increasing role in the evaluation of arthritic joints.This article will review the key aspects of the current status and recent important advances of imaging techniques available to investigate the child with rheumatic disease, briefly discussing conventional radiography, and particularly focusing on MRI and US. In this era of advancing imaging technology, knowledge of the relative values of available imaging techniques is necessary to optimize the management of children with JIA.

MR imaging of early rheumatoid arthritis

Early diagnosis and treatment have been recognized as essential for improving clinical outcomes in patients with early rheumatoid arthritis. However, diagnosis is somewhat difficult in the early stages of the disease because the diagnostic criteria were developed from data obtained in patients with established rheumatoid arthritis and therefore are not readily applicable. Magnetic resonance (MR) imaging is increasingly being used in the assessment of rheumatoid arthritis due to its capacity to help identify the key pathologic features of this disease entity at presentation. MR imaging has demonstrated greater sensitivity for the detection of synovitis and erosions than either clinical examination or conventional radiography and can help establish an early diagnosis of rheumatoid arthritis. It also allows the detection of bone marrow edema, which is thought to be a precursor for the development of erosions in early rheumatoid arthritis as well as a marker of active inflammation. In addition, MR imaging can help differentiate rheumatoid arthritis from some clinical subsets of peripheral spondyloarthropathies by allowing identification of inflammation at the insertions of ligaments and tendons (enthesitis).

MRI quantification of rheumatoid arthritis: current knowledge and future perspectives

The international consensus on treatment of rheumatoid arthritis (RA) involves early initiation of disease modifying anti-rheumatic drugs (DMARDs) for which a reliable identification of early disease is mandatory. Conventional radiography of the joints is considered the standard method for detecting and quantifying joint damage in RA. However, radiographs only show late disease manifestations as joint space narrowing and bone erosions, whereas it cannot detect synovitis and bone marrow oedema, i.e., inflammation in the synovium or the bone, which may be visualized by magnetic resonance imaging (MRI) months to years before erosions develop. Furthermore, MRI allows earlier visualization of bone erosions than radiography. In order to allow early treatment initiation and optimal guidance of the therapeutic strategy, there is a need for methods which are capable of early detection of inflammatory joint changes. In this review, we will discuss available data, advantages, limitations and potential future of MRI in RA.

Longitudinal changes in rheumatoid arthritis after rituximab administration assessed by quantitative and dynamic contrast-enhanced 3-T MR imaging: preliminary findings

We retrospectively assessed the longitudinal changes of rheumatoid arthritis under rituximab therapy by use of quantitative and dynamic contrast-enhanced 3-T magnetic resonance (MR) imaging of the metacarpophalangeal joints of 10 patients at baseline and 26 weeks (n = 10). Additional studies were available at 12 weeks (n = 9) and at 52 weeks (n = 5). Clinical activity was assessed by use of the 28-joint disease activity score (DAS28). MR imaging was used to assess volumes of synovial enhancement, osseous enhancement, and erosions and early rapid enhancement. DAS28 and serum C-reactive protein trended down over time and were significantly lower at 26 weeks. Volume of synovial enhancement and early rapid enhancement showed a significant minimum at 26 weeks and increased thereafter. The erythrocyte sedimentation rate paralleled these two trends. Osseous enhancement did not significantly change over time. Erosions showed a significant progression. Trends of DAS28 and erosions were significantly different (P = 0.0075). In conclusion, our preliminary results suggest that rituximab is associated with a decrease of the inflammatory activity of synovitis with a minimum at 26 weeks and increasing activity thereafter suggesting recurrence. Our results further suggest subclinical progression of erosions with an inverse relationship to decreasing disease activity scores. Further studies are needed to confirm these results.

Early rheumatoid arthritis and its differentiation from other joint abnormalities

The introduction of disease-modifying antirheumatic drugs has created new demands on imaging to early identify patients with rheumatoid arthritis and opened new prospects in therapeutic management of patients with aggressive disease. Therefore, new imaging modalities such as magnetic resonance imaging and ultrasound have developed during the past few years in this field. In some cases, both magnetic resonance imaging and ultrasound may be also useful in making the distinction between early rheumatoid arthritis and other joints abnormalities, including early psoriatic arthritis. This article will review key aspects of important advances in imaging in rheumatoid arthritis, particularly focusing on magnetic resonance imaging and ultrasound.

The Development of EERA: Software for Assessing Rheumatic Joint Erosions

Objective

The principal aim of this study was to create a segmentation program, to be used by nonmusculoskeletal or junior fellows, that defines the bones in the metacarpophalangeal joint in a dynamic 3-dimensional image that will lead to higher inter-reader agreement of bone erosion scores.

Methods

The second to fifth metacarpal head and phalangeal bases of 15 participants were rated according to the Rheumatoid Arthritis Magnetic Resonance Imaging Scoring system by one trained and one untrained reader. Two comparisons were made. The first comparison was between the 2 readers using only the traditional 2-dimensional magnetic resonance image set. The second comparison was between the 2 readers, with the untrained reader using a custom segmentation program with traditional 2-dimensional magnetic resonance image set.

Results

The software marginally increased inter-reader reliability with the exception of the second metacarpal head, for which reliability was increased substantially. Future work will concentrate on improving image acquisition, better delineate erosions from surrounding bone oedema, and address methods to directly determine erosion volumes.

Conclusions

Software designed to display dynamic 3-dimensional images enables a relatively untrained user to score the metacarpophalangeal joints in the hand for erosions equivalent to that produced by an expert using the manual methods.

Overview of imaging in inflammatory arthritis

Whether magnetic resonance imaging (MRI) or ultrasound (US) are chosen for the purposes of musculoskeletal interrogation depends upon a variety of factors ranging from the anatomy targeted to cost considerations and the time of acquisition. Newer technologies such as higher-strength MRI or 3D-US promise to help overcome some of the disadvantages of each option. Improving technical proficiency is the thrust of efforts to support more widespread application of sonographic assessment in various clinical arenas. Finally, these technologies offer the opportunity to diagnose inflammatory conditions at early stages of their disease progression.

Detection of bone erosions in rheumatoid arthritis wrist joints with magnetic resonance imaging, computed tomography and radiography

BACKGROUND

The objectives of the present study were, with multidetector computed tomography (CT) as the reference method, to determine the performance of magnetic resonance imaging (MRI) and radiography for the detection of bone erosions in rheumatoid arthritis wrist bones, and to test whether measuring volumes of erosions on CT and MRI is reproducible and correlated to semiquantitative assessments (scores) of erosions on CT, MRI and radiography.

METHODS

Seventeen patients with rheumatoid arthritis and four healthy control individuals underwent CT, MRI and radiography of one wrist, performed on the same day. CT was performed on a Philips Mx8000IDT unit (voxel size 0.4 mm x 0.4 mm x 1 mm) and MRI was performed on a Philips Panorama 0.6T unit (voxel size 0.4 mm x 0.4 mm x 0.4 mm). Images were evaluated separately for erosions in all wrist bones and were scored according to the principles of the Outcome Measures in Rheumatology Rheumatoid Arthritis MRI Scoring System (CT and MRI) and the Sharp/van der Heijde (radiographs) scoring methods. Measurements of erosion volumes of all erosions were performed twice with a 1-week interval.

RESULTS

With CT as the reference method, the overall sensitivity, specificity and accuracy (concordance) of MRI for detecting erosions were 61%, 93% and 77%, respectively, while the respective values were 24%, 99% and 63% for radiography. The intramodality agreements when measuring erosion volumes were high for both CT and MRI (Spearman correlation coefficients 0.92 and 0.90 (both P < 0.01), respectively). Correlations between volumes and scores of individual erosions were 0.96 for CT and 0.99 for MRI, while they were 0.83 (CT) and 0.80 (MRI) for persons' total erosion volume and total score (all P < 0.01).

CONCLUSION

With CT as the reference method, MRI showed moderate sensitivity and good specificity and accuracy for detection of erosions in rheumatoid arthritis and healthy wrist bones, while radiography showed very low sensitivity. The tested volumetric method was highly reproducible and correlated to scores of erosions.

Three-dimensional and thermal surface imaging produces reliable measures of joint shape and temperature: a potential tool for quantifying arthritis

Introduction

The assessment of joints with active arthritis is a core component of widely used outcome measures. However, substantial variability exists within and across examiners in assessment of these active joint counts. Swelling and temperature changes, two qualities estimated during active joint counts, are amenable to quantification using noncontact digital imaging technologies. We sought to explore the ability of three dimensional (3D) and thermal imaging to reliably measure joint shape and temperature.

Methods

A Minolta 910 Vivid non-contact 3D laser scanner and a Meditherm med2000 Pro Infrared camera were used to create digital representations of wrist and metacarpalphalangeal (MCP) joints. Specialized software generated 3 quantitative measures for each joint region: 1) Volume; 2) Surface Distribution Index (SDI), a marker of joint shape representing the standard deviation of vertical distances from points on the skin surface to a fixed reference plane; 3) Heat Distribution Index (HDI), representing the standard error of temperatures. Seven wrists and 6 MCP regions from 5 subjects with arthritis were used to develop and validate 3D image acquisition and processing techniques. HDI values from 18 wrist and 9 MCP regions were obtained from 17 patients with active arthritis and compared to data from 10 wrist and MCP regions from 5 controls. Standard deviation (SD), coefficient of variation (CV), and intraclass correlation coefficients (ICC) were calculated for each quantitative measure to establish their reliability. CVs for volume and SDI were <1.3% and ICCs were greater than 0.99.

Results

Thermal measures were less reliable than 3D measures. However, significant differences were observed between control and arthritis HDI values. Two case studies of arthritic joints demonstrated quantifiable changes in swelling and temperature corresponding with changes in symptoms and physical exam findings.

Conclusion

3D and thermal imaging provide reliable measures of joint volume, shape, and thermal patterns. Further refinement may lead to the use of these technologies to improve the assessment of disease activity in arthritis.

Rheumatoid arthritis bone erosion volumes on CT and MRI: reliability and correlations with erosion scores on CT, MRI and radiography

OBJECTIVES

To investigate intramodality and intermodality agreements of CT and MRI erosion volumes in metacarpophalangeal (MCP) joints in rheumatoid arthritis (RA), and to compare the volumes with erosion scores for CT, MRI and radiography.

METHODS

In total, 17 patients with RA and four healthy controls underwent unilateral CT, MRI and radiography of second to fifth MCP joints in one hand. Erosion volumes (using OSIRIS software) and scores were determined from CT, MRI and radiography (scores only).

RESULTS

CT, MRI and radiography detected 77, 62 and 12 erosions, respectively. On CT, the mean erosion volume was 26 mm(3) (median 10; range 0 to 248) and 30 mm(3) (18; 1 to 163) on MRI. Total erosion volumes (per patient/control) were 97 mm(3) (29; 0 to 485) on CT and 90 mm(3) (46; 0 to 389) on MRI. For volumes, Spearman correlation coefficients were 0.96 to 0.99 (CT vs CT), 0.95 to 0.98 (MRI vs MRI) and 0.64 to 0.89 (CT vs MRI), all p<0.01. MRI erosion volumes correlated with the Outcome Measures in Rheumatology Clinical Trials/Rheumatoid Arthritis Magnetic Resonance Imaging Score (OMERACT RAMRIS) erosion scores (0.91 to 0.99; p<0.01) and the Sharp/van der Heijde erosion score (0.49 to 0.63; p<0.01).

CONCLUSION

Very high intramodality and high intermodality agreements of CT and MRI erosion volumes were found, encouraging further testing in longitudinal studies. A close correlation with CT and MRI erosion volumes supports the OMERACT RAMRIS erosion score as a valid measure of joint destruction in RA.

[Magnetic resonance of the hand in rheumatoid arthritis. Review of methodology, and its use in diagnosis, monitoring and prognosis]

The ideal aim of treatment in rheumatoid arthritis (RA) is to suppress synovial inflammation and to stop or reduce structural joint damage progression. To evaluate joint damage in RA, radiographic assessment of hands and feet is the traditional method. Nevertheless, plain film radiography can only evaluate bone damage (erosion) and, indirectly, joint cartilage. Magnetic resonance imaging presents important advantages since allows to study, not only the cortical bone and the marrow, but also the synovial membrane, tendon and ligament structures,and adjacent soft tissue that usually are involved in early disease. Moreover, hand-magnetic resonance (h-MRI) has shown to be more sensitive than plain radiography in detecting early erosions and predicting progression of bone damage, allowing a rapid diagnosis and to start the most efficient therapy as well as to achieve better outcomes for this disease.

Advanced imaging in rheumatoid arthritis: part 2: erosions

Rheumatoid arthritis (RA) is a chronic and progressive inflammatory disorder primarily affecting the synovium. We now recognise that conventional radiographic images show changes of rheumatoid arthritis late after irreversible joint damage has occured. With the advent of powerful disease-modifying drugs there is a need for early demonstration of rheumatoid arthritis and to monitor progress of the disease and response to therapy. Advanced imaging techniques such as ultrasound and MRI have focussed on the demonstration and quantification of synovitis and erosions and allow early diagnosis of RA. The technology to quantify synovitis and erosions is developing rapidly and now allows change in disease activity to be assessed. However, problems undoubtedly exist in quantification techniques and this review serves to highlight them. Much of the literature on advanced imaging in RA appears in rheumatological journals and may not be familiar to radiologists. This review article aims to increase the awareness of radiologists to this field and to encourage them to participate and contribute to the ongoing development of these modalities. Without this collaboration it is unlikely that these modalities will reach their full potential in the field of rheumatological imaging. This review is in two parts. This first part addresses synovitis imaging. The second part will look at advanced imaging of erosions in RA.

Automatic quantification of changes in bone in serial MR images of joints

Recent innovations in drug therapies have made it highly desirable to obtain sensitive biomarkers of disease progression that can be used to quantify the performance of candidate disease modifying drugs. In order to measure potential image-based biomarkers of disease progression in an experimental model of rheumatoid arthritis (RA), we present two different methods to automatically quantify changes in a bone in in-vivo serial magnetic resonance (MR) images from the model. Both methods are based on rigid and nonrigid image registration to perform the analysis. The first method uses segmentation propagation to delineate a bone from the serial MR images giving a global measure of temporal changes in bone volume. The second method uses rigid body registration to determine intensity change within a bone, and then maps these into a reference coordinate system using nonrigid registration. This gives a local measure of temporal changes in bone lesion volume. We detected significant temporal changes in local bone lesion volume in five out of eight identified candidate bone lesion regions, and significant difference in local bone lesion volume between male and female subjects in three out of eight candidate bone lesion regions. But the global bone volume was found to be fluctuating over time. Finally, we compare our findings with histology of the subjects and the manual segmentation of bone lesions.

Periarticular Bone Findings in Rheumatoid Arthritis: T2-Weighted Versus Contrast-Enhanced T1-Weighted MRI

OBJECTIVE

The purpose of this study was to establish the relative predictive value of T2-weighted and contrast-enhanced T1-weighted MRI techniques for bone erosions that are evident on CT. Because it is known that MRI depicts abnormalities in the periarticular bone of patients with rheumatoid arthritis, we wanted to compare the outcomes of T2-weighted versus contrast-enhanced T1-weighted MRI techniques.

MATERIALS AND METHODS

Eleven patients with rheumatoid arthritis underwent CT imaging of their most affected wrist. Fast spin-echo T2-weighted MR images were then acquired with spectral fat saturation. Enhanced T1-weighted spin-echo images acquired before and after IV administration of gadopentetate dimeglumine were used to determine the percent enhancement. Imaging examinations were scored for 15 anatomic zones. The CT score was based on cortical bone erosion. The MR score was based on periarticular bone marrow signal alteration.

RESULTS

Both T2-weighted MR images with spectral fat saturation and enhanced T1-weighted images were concordant for the presence or absence of bone abnormalities in 122 of 165 zones (74%). Of the 43 zones that were discordant for an abnormality by the two MR techniques, the T2-weighted images were positive in five zones, and enhanced T1-weighted images were positive in 38 zones (p < 0.001). Of the 43 zones that were discordant by the two MR techniques, enhanced T1-weighted images were concordant with CT in 20 zones, whereas the T2-weighted images were concordant with CT in 23 zones (p = 0.76). A greater proportion of lesions detected by the T2-weighted images were "edema-like" signal patterns.

CONCLUSION

In rheumatoid arthritis, contrast-enhanced T1-weighted MRI depicts more periarticular bone abnormalities than fat-suppressed T2-weighted MRI. These MR techniques are equally predictive of frank, erosive disease that is evident on CT.

Quantifying peri-meniscal synovitis and its relationship to meniscal pathology in osteoarthritis of the knee

The objectives of this study were to validate a semiquantitative scoring system for estimating perimeniscal synovitis in osteoarthritic (OA) knees and to examine the relationship between the extent of synovitis and the degree of meniscal pathology using gadolinium-enhanced magnetic resonance imaging (MRI). Forty-three subjects with clinically diagnosed OA knee were assessed for peri-meniscal synovitis using gadolinium-enhanced MRI. Quantitative measurements of synovitis were made by summing areas in consecutive slices within generated regions of interest, and the synovitis was also scored semi-quantitatively using a 0-3 scale. Meniscal pathology (extrusion, degeneration and tearing) was also scored semiquantitatively. Establishment of a correlative relationship was undertaken using Spearman's rho (rho). A total of 86 sites were assessed. The semi-quantitative synovitis score correlated well with the quantitative synovitis score (rho>0.9). A moderate association between medial meniscal extrusion and synovitis was demonstrated (rho=0.762, P<0.000), although this association was not as strong in the lateral compartment (rho=0.524, P<0..000). The results suggest the semiquantitative scoring system is valid for assessing perimeniscal synovitis. The relationship between meniscal pathology and adjacent synovitis requires further study.

The relationship between limited MRI section analyses and volumetric assessment of synovitis in knee osteoarthritis

AIM

To assess whether simple, limited section analysis can replace detailed volumetric assessment of synovitis in patients with osteoarthritis (OA) of the knee using contrast-enhanced magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Thirty-five patients with clinical and radiographic OA of the knee were assessed for synovitis using gadolinium-enhanced MRI. The volume of enhancing synovium was quantitatively assessed in four anatomical sites (the medial and lateral parapatellar recesses, the intercondylar notch and the suprapatellar pouch) by summing the volumes of synovitis in consecutive sections. Four different combinations of section analysis were evaluated for their ability to predict total synovial volume.

RESULTS

A total of 114 intra-articular sites were assessed. Simple linear regression demonstrated that the best predictor of total synovial volume was the analysis containing the inferior, mid and superior sections of each of the intra-articular sites, which predicted between 40-80% (r(2) = 0.396, p < 0.001 for notch; r(2) = 0.818, p < 0.001 for medial parapatellar recess) of the total volume assessment.

CONCLUSIONS

The results suggest that a three-section analysis on axial post-gadolinium sequences provides a simple surrogate measure of synovial volume in OA knees.

Reliability and sensitivity to change of the OMERACT rheumatoid arthritis magnetic resonance imaging score in a multireader, longitudinal setting

OBJECTIVE

To assess the intra- and interreader reliability and the sensitivity to change of the Outcome Measures in Rheumatology Clinical Trials (OMERACT) Rheumatoid Arthritis Magnetic Resonance Imaging Score (RAMRIS) system on digital images of the wrist joints of patients with early or established rheumatoid arthritis (RA).

METHODS

Ten sets of baseline and 1-year followup MR images of the wrists of patients with progressive changes on conventional hand radiographs were scored independently by 4 readers on 2 consecutive days, preceded by reader training and calibration. The MR images were acquired and scored according to the recommendations from the OMERACT MRI group. The intra- and interreader agreement (evaluated by intraclass correlation coefficients [ICCs]) and the sensitivity to change (evaluated by the smallest detectable difference [SDD]) were determined for scores of synovitis, erosion, and bone marrow edema status and for change scores.

RESULTS

Intrareader ICCs were generally very high, both for status scores (median baseline and followup 0.89 and 0.90 for synovitis, 0.91 and 0.90 for erosion, and 0.90 and 0.98 for edema) and for change scores (median 0.80 for synovitis, 0.96 for erosion, and 0.97 for edema). The SDDs were generally low, suggesting a high potential to detect changes. Interreader single-measure ICCs were high for status scores (mean baseline and followup 0.69 and 0.78 for synovitis, 0.83 and 0.73 for erosion, and 0.79 and 0.95 for edema) and for change scores (mean 0.74 for synovitis, 0.67 for erosion, and 0.95 for edema). The average-measure ICCs were > or =0.94 for all components of both the status scores and change scores.

CONCLUSION

The RAMRIS showed very good intrareader reliability, good interreader reliability, and a high level of sensitivity to change. The results suggest that the RAMRIS may be a suitable system for use in monitoring joint inflammation and destruction in RA.

The validation of simple scoring methods for evaluating compartment-specific synovitis detected by MRI in knee osteoarthritis

OBJECTIVES

Synovitis is common in osteoarthritis (OA) of the knee. In order to evaluate its importance, valid and reliable quantification methods are required. The aim of this study was to compare simple, semiquantitative synovitis scores with detailed volume assessments in subjects with knee OA using magnetic resonance imaging (MRI) as the investigative tool.

METHODS

Thirty-five subjects with clinically diagnosed OA of the knee were assessed for synovitis using gadolinium-enhanced MRI. The volume measurement of synovitis was assessed at four sites (medial and lateral parapatellar recesses, intercondylar notch and suprapatellar pouch). The semiquantitative scoring of synovitis was scored on a 0-3 scale. Establishment of a correlative relationship was undertaken using Spearman's rho for the individual site-specific measurements. Ordinal regression modelling was undertaken in order to establish the capacity of the synovitis scoring to predict the volume measurement.

RESULTS

A total of 140 sites were assessed. There were good correlations between the semiquantitative scores and the volume measurements, ranging from rho = 0.86 (P < 0.00) for the medial parapatellar recess to rho = 0.71 (P < 0.00) for the lateral parapatellar recess. The ordinal regression suggested that, while the synovitis scores predicted between 50 and 70% (R2 = 0.53, P < 0.00 to R2 = 0.71, P < 0.00) of the volume measurements, there was some minor overlap, particularly in the mid-range synovitis scores.

CONCLUSIONS

These results suggest that semiquantitative synovitis scores are valid and will enable feasible evaluation of the synovium in OA cohorts.

A novel ultrasonographic synovitis scoring system suitable for analyzing finger joint inflammation in rheumatoid arthritis

OBJECTIVE

To develop an ultrasonographic (US) synovitis scoring system suitable for evaluation of finger joint inflammation in patients with active rheumatoid arthritis (RA) and to compare semiquantitative US scoring with quantitative US measurements.

METHODS

US was performed at the palmar and dorsal sides of the second through fifth metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints in 10 healthy subjects and in the clinically more affected hand in 46 RA patients. Ten patients additionally underwent magnetic resonance imaging (MRI). Synovitis was measured, standardized, and scored according to a semiquantitative method. The 2 methods (semiquantitative US scoring, quantitative US) were compared and statistical cutoffs were identified using receiver operating characteristic (ROC) curve analysis. MRI results were compared with semiquantitative US scoring and quantitative US results. The optimal US scoring method from 6 joint combinations was identified (ROC curve analysis).

RESULTS

Synovitis was most frequently detected in the palmar proximal area (86% of affected joints). We found no significant differences between individual PIP joints or between individual MCP joints, indicating that all fingers within each of these joint groups should be treated equally for statistical calculations, although each joint group as a whole should be treated separately. The optimal cutoff point to distinguish between "health" and "pathology" was 0.6 mm both for MCP joints (sensitivity 94%, specificity 89%) and for PIP joints (sensitivity 90%, specificity 88%). There was no significant difference between semiquantitative US scores and quantitative US measurements. The best results for joint combinations were achieved using the "sum of 4 fingers" (second through fifth MCP and PIP joints) and "sum of 3 fingers" (second through fourth MCP and PIP joints) methods. Comparison of MRI results with semiquantitative US scores revealed high concordance.

CONCLUSION

US evaluation of finger joint synovitis can be considerably simplified by focusing on the palmar side and by applying semiquantitative grading instead of quantitative measurements. For evaluation of treatment efficacy based on synovitis in RA patients, we recommend using the "sum of 3 fingers" method in longitudinal trials.

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

This article gives a short overview of the development and characteristics of the OMERACT rheumatoid arthritis MRI scoring system (RAMRIS), followed by an introduction to the use of the EULAR-OMERACT rheumatoid arthritis MRI reference image atlas. With this atlas, MRIs of wrist and metacarpophalangeal joints of patients with rheumatoid arthritis can be scored for synovitis, bone oedema, and bone erosion, guided by standard reference images.

The EULAR-OMERACT rheumatoid arthritis MRI reference image atlas: the wrist joint

This paper presents the wrist joint MR images of the EULAR-OMERACT rheumatoid arthritis MRI reference image atlas. Reference images for scoring synovitis, bone oedema, and bone erosions according to the OMERACT RA MRI scoring (RAMRIS) system are provided. All grades (0-3) of synovitis are illustrated in each of the three wrist joint areas defined in the scoring system--that is, the distal radioulnar joint, the radiocarpal joint, and the intercarpal-carpometacarpal joints. For reasons of feasibility, examples of bone abnormalities are limited to five selected bones: the radius, scaphoid, lunate, capitate, and a metacarpal base. In these bones, grades 0-3 of bone oedema are illustrated, and for bone erosion, grades 0-3 and examples of higher grades are presented. The presented reference images can be used to guide scoring of wrist joints according to the OMERACT RA MRI scoring system.

Clinical characteristics of an anatomical hand index measured in patients with rheumatoid arthritis as a potential outcome measure

OBJECTIVES

To determine the clinical characteristics of an anatomical hand index previously reported as a potential measure of joint deformity and outcome in patients with rheumatoid arthritis.

METHODS

The hand index (open hand span - closed hand span/lateral height of the hand) was measured in a cross-sectional study of 145 out-patients with rheumatoid arthritis with disease durations 0-55 yr. Subsets of patients were restudied at mean follow-ups of approximately 9 months and 4 yr.

RESULTS

The hand index fell gradually with disease duration. Correlations were demonstrated with the Sharp index (r = - 0.39, P = 0.000) and to a lesser extent with disease activity score (r = - 0.28, P = 0.001). At 260 +/- 115 days the hand index worsened by 0.09 units (P = 0.09, NS). At 51.6 +/- 5.4 months the index showed a fall from 1.96 +/- 0.73 to 1.61 +/- 0.65 (P = 0.000). During the same interval the Sharp index increased from 60 +/- 68 to 80 +/- 71 (P = 0.000).

CONCLUSIONS

Measurement of simple hand dimensions can demonstrate worsening of hand deformity with time in patients with rheumatoid arthritis. We suggest that more sophisticated analysis of digital hand images, as used in our original study, might yield additional information and increase the sensitivity of an anatomical hand index as an outcome measure in rheumatoid arthritis.

Magnetic resonance imaging of peripheral joints in rheumatic diseases

The need for better methods than the conventional clinical, biochemical and radiographical examinations in the management of inflammatory joint diseases is evident, since these methods are not sensitive or specific to early pathologies and subtle changes. Magnetic resonance imaging (MRI) offers improved sensitivity to early inflammatory and destructive changes in peripheral joints in rheumatoid arthritis (RA) and, even though less well documented, in other inflammatory joint diseases. Good evidence is available that MRI bone erosions represent true bone abnormalities and are predictors of radiographical outcome in RA. Similarly, there is solid evidence for MRI synovitis representing true synovial inflammation and being of considerable practical, clinical and radiological significance in RA. Describing the encouraging current knowledge regarding MRI for diagnosis, monitoring and prognosis, this chapter discusses the potential for the use of MRI in the clinical management of patients with suspected and diagnosed inflammatory joint diseases, as well as research priorities and clinical situations where the use of MRI could be suggested.

Measurement of cartilage volumes in rheumatoid arthritis using MRI

MRI is a valuable imaging modality for assessment of the articular cartilage in rheumatoid arthritis (RA) and is potentially of use in monitoring disease progression and response to therapy. In this study, we investigated the sources of error in volume measurements obtained by segmentation of MR images of knee cartilage in patients with RA and followed cartilage volume in a group of RA patients for 12 months. 23 RA patient volunteers were recruited for knee imaging. Six subjects were imaged at baseline only, six were imaged at baseline and again within an hour in the same imaging session, six subjects were imaged at baseline and 7 days, and 17 subjects were imaged at baseline, 4+/-2 months and 12 months. Imaging was performed at 1.0 T using a three-dimensional spoiled gradient-echo sequence with fat-suppression. Manual image segmentation was performed once or twice on the lateral tibial, medial tibial, patellar and femoral compartment by either one or two segmenters. Coefficients of variation (CoV) for repeated volume measurement of total cartilage were 2.2% (same segmenter, same scan), 5.2% (different segmenter, same scan), 4.9% (same segmenter, different scan, same session), and 4.4% (same segmenter, different scan, different session). Over the 12 month duration of the study there was no significant change in total cartilage volume, nor were there significant changes in volume in any individual compartment. This measurement technique is reproducible, but any net change in cartilage volume over 1 year is very small.

Noninvasive techniques for assessing skeletal changes in inflammatory arthritis: imaging technique

New imaging techniques such as ultrasound and MRI are likely to play increasing roles in the future management of patients with inflammatory arthritis, particularly those with rheumatoid arthritis and spondyloarthropathies. Ultrasound has a number of distinct advantages including its ability to scan multiple joints, safety, and immediately availability in clinic. MRI, however, is more sensitive and has a greater field of view because of its tomographic nature. Both modalities have the added advantage over radiography in that they can image soft tissue as well as bone. Dual X-ray absorptiometry already has an established role to play in the assessment of osteoporosis, but new techniques such as digital radiogrametry, quantitative CT, and ultrasound potentially will have a more important role to play in the future.

Multispectral analysis of bone lesions in the hands of patients with rheumatoid arthritis

Quantitative measures of rheumatoid arthritis (RA) disease progression can provide valuable tools for evaluation of new treatments during clinical trials. In this study, a novel multispectral (MS) MRI analysis method is presented to quantify changes in bone lesion volume (DeltaBLV) in the hands of RA patients. Image registration and MS analysis were employed to identify MS tissue class transitions between two serial MRI exams. DeltaBLV was determined from MS class transitions between two time points. The following three classifiers were investigated: (a) multivariate Gaussian (MVG), (b) k-nearest neighbor (k-NN), and (c) K-means (KM). Unlike supervised classifiers (MVG, k-NN), KM, an unsupervised classifier, does not require labeled training data, resulting in potentially greater clinical utility. All MS estimates of DeltaBLV were linearly correlated (r(p)) with manual estimates. KM and k-NN estimates also exhibited a significant rank-order correlation (r(s)) with manual estimates. For KM, r(p) = 0.94 p < 0.0001, r(s) = 0.76 p = 0.002; for k-NN, r(p) = 0.86 p = 0.0001, r(s) = 0.69 p = 0.009; and for MVG, r(p) = 0.84 p = 0.0003, r(s) = 0.49 p = 0.09. Temporal classification rates were as follows: for KM, 90.1%; for MVG, 89.5%; and for k-NN, 86.7%. KM matched the performance of k-NN, offering strong potential for use in multicenter clinical trials. This study demonstrates that MS tissue class transitions provide a quantitative measure of DeltaBLV.

Use of multispectral magnetic resonance imaging analysis to quantify erosive changes in the hands of patients with rheumatoid arthritis: short-term and long-term longitudinal studies

OBJECTIVE

Magnetic resonance imaging (MRI) has been shown to be more sensitive than radiography for detecting bone erosions in rheumatoid arthritis (RA). Semiquantitative scoring based on visual image assessment has been introduced. However, there is considerable interest in true quantitative measures, particularly in the context of clinical trials designed to show differences between treatment groups. This study was undertaken to investigate the use of a new quantitative approach, multispectral (MS) image analysis, for assessing erosive change.

METHODS

T1-weighted spin-echo (SE) and fat-suppressed gradient-echo (GE) sequences of metacarpophalangeal joints of the dominant hand were acquired at various time points throughout a 2-year period. MS analysis was applied to all images, resulting in segmentation into a generalized bone and a soft tissue class. Voxel changes from one to the other class identified apparent bone lesion volume change (Delta BLV). MR images were also visually scored for erosions (E score). All analyses were performed separately, on a per-joint basis, for short-term and long-term data sets.

RESULTS

Analysis of variance with adjustment for individual effect revealed similar results in the short-term and the long-term studies, using either GE or SE images for visual assessment. Patients with an increase in E score on visual assessment had a significantly higher Delta BLV than those without.

CONCLUSION

Temporal MS analysis of MRIs can be used to detect and quantify erosive changes in RA. This semiautomated method may be useful for demonstrating differences between treatment groups in clinical trials.