Interobserver Agreement and Performance of Concurrent AI Assistance for Radiographic Evaluation of Knee Osteoarthritis.

Background Due to conflicting findings in the literature, there are concerns about a lack of objectivity in grading knee osteoarthritis (KOA) on radiographs. Purpose To examine how artificial intelligence (AI) assistance affects the performance and interobserver agreement of radiologists and orthopedists of various experience levels when evaluating KOA on radiographs according to the established Kellgren-Lawrence (KL) grading system. Materials and Methods In this retrospective observer performance study, consecutive standing knee radiographs from patients with suspected KOA were collected from three participating European centers between April 2019 and May 2022. Each center recruited four readers across radiology and orthopedic surgery at in-training and board-certified experience levels. KL grading (KL-0 = no KOA, KL-4 = severe KOA) on the frontal view was assessed by readers with and without assistance from a commercial AI tool. The majority vote of three musculoskeletal radiology consultants established the reference standard. The ordinal receiver operating characteristic method was used to estimate grading performance. Light kappa was used to estimate interrater agreement, and bootstrapped t statistics were used to compare groups. Results Seventy-five studies were included from each center, totaling 225 studies (mean patient age, 55 years ± 15 [SD]; 113 female patients). The KL grades were KL-0, 24.0% (n = 54); KL-1, 28.0% (n = 63); KL-2, 21.8% (n = 49); KL-3, 18.7% (n = 42); and KL-4, 7.6% (n = 17). Eleven readers completed their readings. Three of the six junior readers showed higher KL grading performance with versus without AI assistance (area under the receiver operating characteristic curve, 0.81 ± 0.017 [SEM] vs 0.88 ± 0.011 [P < .001]; 0.76 ± 0.018 vs 0.86 ± 0.013 [P < .001]; and 0.89 ± 0.011 vs 0.91 ± 0.009 [P = .008]). Interobserver agreement for KL grading among all readers was higher with versus without AI assistance (κ = 0.77 ± 0.018 [SEM] vs 0.85 ± 0.013; P < .001). Board-certified radiologists achieved almost perfect agreement for KL grading when assisted by AI (κ = 0.90 ± 0.01), which was higher than that achieved by the reference readers independently (κ = 0.84 ± 0.017; P = .01). Conclusion AI assistance increased junior readers' radiographic KOA grading performance and increased interobserver agreement for osteoarthritis grading across all readers and experience levels. Published under a CC BY 4.0 license. Supplemental material is available for this article.

Inter-software and inter-threshold reliability of quantitative paraspinal muscle segmentation.

PURPOSE: Changes in the cross-sectional area (CSA) and functional cross-sectional area (FCSA) of the lumbar multifidus (MF) and erector spinae muscles (ES) are factors that can contribute to low back pain. For the assessment of muscle CSA and composition there are various software and threshold methods used for tissue segmentation in quantitative analysis. However, there is currently no gold standard for software as well as muscle segmentation. This study aims to analyze the measurement error between different image processing software and different threshold methods for muscle segmentation. METHODS: Magnetic resonance images (MRI) of 60 patients were evaluated. Muscle CSA and FCSA measurements were acquired from axial T2-weighted MRI of the MF and ES at L4/L5 and L5/S1. CSA, FCSA, and FCSA/CSA ratio were measured independently by two observers. The MRI images were measured using two different software programs (ImageJ and Amira) and with two threshold methods (Circle/Overlap method) for each software to evaluate FCSA and FCSA/CSA ratio. RESULTS: Inter-software comparisons revealed high inter-rater reliability. However, poor inter-rater reliability were obtained with different threshold methods. CSA, FCSA, and FCSA/CSA showed excellent inter-software agreement of 0.75-0.99 regardless of the threshold segmentation method. The inter-rater reliability between the two observers ranged between 0.75 and 0.99. Comparison of the two segmentation methods revealed agreement between 0.19 and 0.84. FCSA and FCSA/CSA measured via the Overlap method were significantly higher than those measured via the Circle method (P < 0.01). CONCLUSION: The present study showed a high degree of reliability with very good agreement between the two software programs. However, study results based on different threshold methods should not be directly compared.

Characterization of bone marrow lesions in axial spondyloarthritis using quantitative T1 mapping MRI.

OBJECTIVE: Conventional magnetic resonance imaging (MRI) uses T1-weighted and short-tau inversion recovery (STIR) sequences to characterize bone marrow in axial spondyloarthritis. However, quantification is restricted to estimating the extent of lesions because signal intensities are highly variable both within individuals and across patients and MRI scanners. This study evaluates the performance of quantitative T1 mapping for distinguishing different types of bone marrow lesions of the sacroiliac joints. MATERIALS AND METHODS: In this prospective study, 62 patients underwent computed tomography (CT) and MRI of the sacroiliac joints including T1, STIR, and T1 mapping. Bone marrow lesions were characterized by three readers and assigned to one of four groups: sclerosis, osteitis, fat lesions, and mixed marrow lesions. Relaxation times on T1 maps were compared using generalized estimating equations and receiver operating characteristics (ROC) analysis. RESULTS: A total of 119 lesions were selected (sclerosis: 38, osteitis: 27, fat lesions: 40; mixed lesions: 14). T1 maps showed highly significant differences between the lesions with the lowest values for sclerosis (1516±220 ms), followed by osteitis (1909±75 ms), and fat lesions (2391±200 ms); p<0.001. T1 mapping differentiated lesions with areas under the ROC curve of 99% (sclerosis vs. osteitis) and 100% (other comparisons). CONCLUSION: T1 mapping allows accurate characterization of sclerosis, osteitis, and fat lesions at the sacroiliac joint but only for homogeneous, non-mixed lesions. Thus, further sequence development is needed before implementation in clinical routine.

New bone formation at the sacroiliac joint in axial spondyloarthritis: characterization of backfill in MRI and CT.

OBJECTIVE: MRI findings of the SI joint space in axial SpA (axSpA) include inflammation and fat metaplasia inside an erosion; the latter is also termed 'backfill'. We compared such lesions with CT to better characterize whether they represent new bone formation. METHODS: We identified patients with axSpA who underwent both CT and MRI of the SI joints in two prospective studies. MRI datasets were jointly screened by three readers for joint space-related findings and grouped into three categories: type A-high short tau inversion recovery (STIR) and low T1 signal; type B-high signal in both sequences; type C-low STIR and high T1 signal. Image fusion was used to identify MRI lesions in CT before we measured Hounsfield units (HU) in each lesion and surrounding cartilage and bone. RESULTS: Ninety-seven patients with axSpA were identified and we included 48 type A, 88 type B, and 84 type C lesions (maximum 1 lesion per type and joint). The HU values were 73.6 (s.d. 15.0) for cartilage, 188.0 (s.d. 69.9) for spongious bone, 1086.0 (s.d. 100.3) for cortical bone, 341.2 (s.d. 96.7) for type A, 359.3 (s.d. 153.5) for type B and 446.8 (s.d. 123.0) for type C lesions. Lesion HU values were significantly higher than those for cartilage and spongious bone, but lower than those for cortical bone (P < 0.001). Type A and B lesions showed similar HU values (P = 0.93), whereas type C lesions were denser (P < 0.001). CONCLUSION: All joint space lesions show increased density and might contain calcified matrix, suggesting new bone formation, with a gradual increase in the proportion of calcified matrix towards type C lesions (backfill).

Anatomical variation of the sacroiliac joint carries an increased risk for erosion and bone marrow oedema in axial spondyloarthritis.

OBJECTIVES: To assess the impact of joint shape variations on inflammatory lesions on SI joint MRIs in patients with axial spondyloarthritis (axSpA). METHODS: A total of 1194 patients from four different prospective cohorts were evaluated, with 684 (57.3%) having sufficient imaging data for inclusion (379 axSpA, 305 controls). All images were evaluated for joint form, erosion, sclerosis, fat metaplasia and bone marrow oedema (BMO) by two independent readers. Logistic regression analyses were used to assess the association of joint form and lesions on imaging for axSpA patients and controls. RESULTS: Atypical joint forms were common in both axSpA (43.5% [154/354]) and control patients (44.2% [134/303]); both intra-articular variants and a crescent joint shape were significantly more common in axSpA patients (18.4% vs 11.6% and 11.0% vs 5.3.%, respectively; P < 0.001). The axSpA patients with intra-articular joint form variants had 2-fold higher odds of exhibiting erosions [odds ratio (OR) 2.09 (95% CI 1.18, 3.69)] and BMO [OR 1.79 (95% CI 1.13, 2.82)]; this association was not observed in controls. Accessory joints increased the odds for sclerosis in axSpA patients [OR 2.54 (95% CI 1.10, 5.84)] and for sclerosis [OR 17.91 (95% CI 6.92, 46.37)] and BMO [OR 2.05 (95% CI 1.03, 4.07)] in controls. CONCLUSIONS: Joint form variations are associated with the presence of inflammatory lesions on SI joint MRIs of axSpA patients. This should be taken into consideration in future research on the interplay of mechanical strain and inflammation in axSpA.

Self-reported diagnostic confidence predicts diagnostic accuracy in axial spondyloarthritis imaging.

OBJECTIVES: Reporting diagnostic confidence (DC) in axial spondyloarthritis (axSpA) imaging is recommended by the ASAS guidelines. Our aim was to investigate whether self-reported DC predicts diagnostic accuracy in axSpA imaging using X-ray (XR), computed tomography (CT) and magnetic resonance imaging (MRI). METHODS: We performed a post hoc analysis including 163 patients with low back pain (89 axSpA and 56 non-axSpA). Nine blinded readers with different experience levels (inexperienced (< 1 year), semi-experienced (3-8 years) and experienced (> 12 years)) scored the sacroiliac joint images for compatibility with axSpA. DC was reported on a scale from 1 (not sure) to 10 (very sure). Mean DC scores and standard deviations were calculated for correct and incorrect responses using XR, CT, MRI, XR+MRI and CT+MRI. Differences in DC were assessed using the Mann-Whitney U test. RESULTS: DC scores were higher for correct axSpA diagnoses and differed significantly between correct and incorrect responses for all modalities (p< 0.001), with a mean DC of 7.1 ± 2.1 and 6.3 ± 2.1 for XR, 8.3 ± 1.8 and 6.7 ± 2.0 for CT, 8.1 ± 1.9 and 6.2 ± 1.9 for MRI, 8.2 ± 1.8 and 6.7 ± 1.8 for XR+MRI and 8.4 ± 1.8 and 6.8 ± 1.8 for CT+MRI, respectively. This was also the case when looking at the results by experience group, except for XR in the inexperienced group. CONCLUSION: Providing self-reported DC in radiological reports is useful information to predict diagnostic reliability in axSpA imaging.

Sex Differences in Renal Cell Carcinoma: The Importance of Body Composition.

PURPOSE: To examine sex-specific differences in renal cell carcinoma (RCC) in relation to abdominal fat accumulation, psoas muscle density, tumor size, pathology, and survival, and to evaluate possible associations with RCC characteristics and outcome. METHODS: A total of 470 patients with RCC who underwent nephrectomy between 2006 and 2019 were included in this retrospective study. Specific characteristics of RCC patients were collected, including sex, height, tumor size, grade, and data on patient survival, if available. Abdominal fat measurements and psoas muscle area were determined at the level of L3 (cm2). RESULTS: Women had a higher subcutaneous (p < 0.001) and men had a higher visceral fat area, relative proportion of visceral fat area (p < 0.001), and psoas muscle index (p < 0.001). Logistic regression analysis showed an association between higher psoas muscle index and lower grade tumors [women: odds ratio (OR) 0.94, 95% confidence interval (CI) 0.89-0.99, p = 0.011; men: OR 0.97 (95% CI, 0.95-0.99, p = 0.012]. Univariate regression analysis demonstrated an association between psoas muscle index and overall survival (women: OR 1.41, 95% CI 1.03-1.93, p = 0.033; men: OR 1.62 (95% CI, 1.33-1.97, p < 0.001). In contrast, there were no associations between abdominal fat measurements and tumor size, grade, or survival. Also, there were no sex-specific differences in tumor size or tumor grades. CONCLUSIONS: A higher preoperative psoas muscle index was independently associated with overall survival in RCC patients, with a stronger association in men compared with women. In addition, the psoas muscle index showed an inverse association with tumor grade, whereby this association was slightly more pronounced in women than in men.

Approach-related anatomical differences in patients with lumbo-sacral transitional vertebrae undergoing lumbar fusion surgery at level L4/5.

INTRODUCTION: Lumbo-sacral transitional vertebrae (LSTV) are accompanied by changes in soft tissue anatomy. The aim of our retrospective study was to evaluate the effects of LSTV as well as the number of free lumbar vertebrae on surgical approaches of ALIF, OLIF and LLIF at level L4/5. MATERIAL AND METHODS: We assessed the CTs of 819 patients. Of these, 53 had LSTV from which 11 had six (6LV) and 9 four free lumbar vertebrae (4LV). We matched them for sex and age to a control group. RESULTS: Patients with LSTV had a higher iliac crest and vena cava bifurcation, a greater distance between the common iliac veins and an anterior translation of the psoas muscle at level L4/5. In contrast, patients with 6LV had a lower iliac crest and aortic bifurcation, no differences in vena cava bifurcation and distance between the iliac veins compared to the control group. CONCLUSIONS: For patients with LSTV and five or four free lumbar vertebrae, the LLIF approach at L4/5 may be hindered due to a high riding iliac crest as well as anterior shift of the psoas muscle. Whereas less mobilization and retraction of the iliac veins may reduce the risk of vascular injury at this segment by ALIF and OLIF. For patients with 6LV, a lower relative height of the iliac crest facilitates lateral approach during LLIF. For ALIF and OLIF, a stronger vessel retraction due to the deeper-seated vascular bifurcation is necessary during ALIF and is therefore potentially at higher risk for vascular injury.

Choose wisely: imaging for diagnosis of axial spondyloarthritis.

OBJECTIVE: To assess the diagnostic accuracy of radiography (X-ray, XR), CT and MRI of the sacroiliac joints for diagnosis of axial spondyloarthritis (axSpA). METHODS: 163 patients (89 with axSpA; 74 with degenerative conditions) underwent XR, CT and MR. Three blinded experts categorised the imaging findings into axSpA, other diseases or normal in five separate reading rounds (XR, CT, MR, XR +MR, CT +MR). The clinical diagnosis served as reference standard. Sensitivity and specificity for axSpA and inter-rater reliability were compared. RESULTS: XR showed lower sensitivity (66.3%) than MR (82.0%) and CT (76.4%) and also an inferior specificity of 67.6% vs 86.5% (MR) and 97.3% (CT). XR +MR was similar to MR alone (sensitivity 77.5 %/specificity 87.8%) while CT+MR was superior (75.3 %/97.3%). CT had the best inter-rater reliability (kappa=0.875), followed by MR (0.665) and XR (0.517). XR +MR was similar (0.662) and CT+MR (0.732) superior to MR alone. CONCLUSIONS: XR had inferior diagnostic accuracy and inter-rater reliability compared with cross-sectional imaging. MR alone was similar in diagnostic performance to XR+MR. CT had the best accuracy, strengthening the importance of structural lesions for the differential diagnosis in axSpA.

Contrast-enhanced CT techniques and MRI perform equally well in arthritis imaging of the hand: a prospective diagnostic accuracy study.

OBJECTIVES: To investigate the performance of dual-energy CT (DECT)-generated iodine maps (iMap) and CT subtraction (CT-S) in the detection of synovitis, tenosynovitis, and peritendonitis/paratenonitis compared to magnetic resonance imaging (MRI) using musculoskeletal ultrasound (MSUS) as standard of reference. METHODS: This IRB-approved prospective study consecutively investigated patients with undifferentiated arthritis. All patients underwent MSUS, MRI and contrast-enhanced DECT of the hand; from the latter conventional CT-S, image-based iMap (iMap-I) and raw data-based iMap (iMap-RD) were reconstructed. CT and MRI datasets were scored for synovitis and tenosynovitis/paratenonitis applying the modified Rheumatoid Arthritis MRI Score (RAMRIS). Sensitivity, specificity, and diagnostic accuracy were calculated. Non-inferiority was tested using the one-tailed McNemar test. Correlation of sum scores was assessed using Pearson's test. Interreader reliability was assessed using Cohen's kappa. RESULTS: Overall, 33 patients were included. MSUS was positive for synovitis and tenosynovitis/paratenonitis in 28 patients with a sum score of 6.91. Excellent correlation with MSUS was shown for CT-S (sum score 6.38; r = 0.91), iMap-RD (sum score 9.74; r = 0.82), MRI (sum score 12.70; r = 0.85), and iMap-I (sum score 6.94; r = 0.50). CT-S had the highest diagnostic accuracy of 83%, followed by iMap-I (78%), MRI (75%), and iMap-RD (74%). All modalities showed non-inferiority. Reader agreement was good for CT-S and MRI (κ = 0.62; 0.64) and fair for iMap-RD and iMap-I (κ = 0.31; 0.37). CONCLUSION: CT-S and iMap allow highly standardized arthritis imaging and are suitable for clinical practice. MSUS still has the highest availability for arthritis imaging and served as gold standard for this study. KEY POINTS: • CT subtraction, iodine map with dual-energy CT, and MRI showed non-inferiority to musculoskeletal ultrasound. • MRI was the most sensitive but least specific imaging technique compared with CT subtraction and dual-energy CT. • CT subtraction showed the best correlation with musculoskeletal ultrasound.

Joint anatomy in axial spondyloarthritis: strong associations between sacroiliac joint form variation and symptomatic disease.

OBJECTIVES: The aim of this investigation was to determine the prevalence of variant SI joint forms in symptomatic patients with mechanical joint disease (MJD) and axial SpA (axSpA) compared with control patients. METHOD: A total of 973 patients were included in this cross-sectional study (95 axSpA; 61 MJD; 817 controls); clinical diagnosis, age and gender were noted. An established scoring system was used to classify joint forms on CT scans of the pelvis. Frequencies of joint forms were compared between groups (axSpA; MJD; controls). RESULTS: Patients with MJD exhibited the highest proportion of atypical joints (80.3% in MJD vs 44.1% in axSpA and 37.5% in controls; P < 0.001). Overall, females had a significantly higher proportion of atypical joints than men (65.0 vs 17.8%; P < 0.001); proportions of atypical joints were significantly higher in males with symptomatic joint disease than in male controls: 32.2% in axSpA, 55.0% in MJD and 13.9% in controls; P ≤ 0.001. Two specific joint forms were significantly more prevalent in symptomatic patients than in controls: the iliosacral complex (16.2 vs 4.2%; P < 0.001) and the crescent-shaped ilium (9.1 vs 2.8%; P < 0.05). CONCLUSIONS: Our data demonstrate a strong association between atypical joint forms and symptomatic joint disease.

Anatomical Joint Form Variation in Sacroiliac Joint Disease: Current Concepts and New Perspectives.

PURPOSE OF REVIEW: The aim of this article is to further the understanding of anatomical variation of the sacroiliac joint (SIJ) within the rheumatological community and point out promising fields of research in the interplay of SIJ anatomy and joint disease. RECENT FINDINGS: Mechanical strain has long been implicated in onset and progression of axial spondyloarthritis (axSpA). Recent investigations found changes in the pattern of degenerative lesions of the SIJ in the normal population in patients with atypical joint forms. Furthermore, atypical SIJ forms are more prevalent in patients with axial spondyloarthritis and mechanical SIJ disease. Mechanical stress from anatomical joint form variation may have an impact on development and progression of axSpA. Furthermore, mechanically induced bone marrow edema may act as an axSpA mimic on MRI and needs to be more accurately classified.

Musculature adaption in patients with lumbosacral transitional vertebrae: a matched-pair analysis of 46 patients.

OBJECTIVE: Even though lumbosacral transitional vertebrae (LSTV) are one of the most common congenital anomalies of the spine, their effect on surrounding soft tissues is not well-studied. We therefore aimed at analyzing the association between LSTV and changes in volume, mass, symmetry, and degeneration of lumbar and trunk muscles. MATERIALS AND METHODS: Abdomen-pelvis CT scans were analyzed in patients with LSTV and a matched control group. LSTV were classified according to the Castellvi classification. Muscles were segmented from the remaining soft tissue and their cross-sectional area and volume were examined at five defined levels. Threshold segmentation was used to differentiate between muscle fibers and fat tissue. Matched pairs were compared using Wilcoxon rank sum tests. For comparison of categorical data, chi-squared tests were performed and for associations between the degree of fusion and muscle size and degeneration, Spearman's correlation coefficients were calculated. Inter- and intrarater reliabilities were evaluated by computing intraclass correlation coefficients. RESULTS: Forty-six patients with LSTV and 46 controls were included. Muscle volume of the paraspinal and trunk muscles was significantly lower (707.0 cm3 vs. 809.7 cm3, p < 0.001) and fatty muscle changes were significantly increased in all but the caudal paravertebral muscles of LSTV patients (M. psoas p < 0.04, M. quadratus lumborum p < 0.001, paravertebral muscles p = 0.011, M. rectus abdominis p < 0.001, M. obliquus abdominis p < 0.001). Correlations between the degree of Castellvi classification and muscle volume were significant (p = 0.001). CONCLUSION: LSTV are associated with a reduction in muscle volume and an increase in muscle degeneration of both lumbar and trunk muscles.

Dual-energy CT collagen density mapping of wrist ligaments reveals tissue remodeling in CPPD patients: first results from a clinical cohort.

OBJECTIVES: To evaluate differences in collagen density as detected by dual-energy computed tomography (DECT) of wrist ligaments between patients with calcium pyrophosphate-dihydrate deposition disease (CPPD) and a control group in order to gain insight into changes of the extracellular matrix in response to crystal deposition. MATERIALS AND METHODS: This retrospective study included 28 patients (18 with CPPD, 10 controls) who underwent DECT of the wrist. Collagen density maps were reconstructed from the DECT datasets and used to measure densities in regions of interest (ROIs) placed in the scapholunate (SL) ligament (dorsal, palmar, proximal), lunotriquetral (LT) ligament, and extensor carpi radialis (ECR) tendon, (n = 260 measurements). The presence of calcifications on standard CT images in these regions was assessed by a blinded reader. Densities were compared with nonparametric tests, and linear regression analysis was performed to investigate the impact of age, sex, and CT- detected calcium deposition on collagen density. RESULTS: Collagen density in the SL ligament was significantly higher in CPPD patients than in controls (overall mean: 265.4 ± 32.1 HU vs. 196.3 ± 33.8 HU; p < 0.001). In the ECR tendon, collagen densities did not differ significantly (p = 0.672): 161.3 ± 20.1 HU in CPPD vs. 163.6 ± 12.0 HU in controls. Regression analysis showed that diagnosis, but not age or calcification, had a significant impact on collagen density. CONCLUSION: Collagen density of the SL ligament is significantly higher in CPPD patients than in control patients. Further research is needed to understand these changes in the extracellular matrix of ligaments in CPPD.

Application of an advanced noise reduction algorithm for imaging of hands in rheumatic diseases: evaluation of image quality compared to standard-dose images.

OBJECTIVES: X-ray is the fundamental imaging technique in both diagnosis and follow-up of rheumatic diseases. As patients often require sequential X-rays over many years, dose reduction is of great importance. New advanced noise reduction algorithms allow for a dose reduction of up to 50%. The aim of this study was to evaluate whether quality of low-dose images is non-inferior to standard-dose images and, therefore, application of this technique is possible in the context of imaging of rheumatic diseases. METHODS: A total of 298 patients with known or suspected rheumatic disease were enrolled prospectively into this study, separated into three consecutive groups: 80%, 64% and 50% tube charge reduction. All patients received imaging of one hand (laterality randomly assigned) with low-dose technique and imaging of the contralateral hand with standard-dose protocol. Images were evaluated by two independent readers who scored (on a scale of 1-5) the visualization of bony cortex, trabeculae and joint spaces of fingers and wrist separately. Additionally, soft tissue and overall contrast were evaluated on the same scale. RESULTS: Overall image quality (expressed by mean sum score out of 40) of the 50% low-dose images was 31.52 (SD 1.94) vs. 31.66 (SD 1.82) for standard images (p = 0.068). Bony contours as well as trabeculae were equally well visualized in both image sets. Median scores for soft tissue visualization was slightly lower for low dose compared to standard images [4 (IQR 3.5-4) vs. 4 (IQR 3.88-4); p = 0.001]. CONCLUSIONS: Overall image quality of low-dose images was not inferior to standard-dose images. Therefore, the application of low-dose technology based on advanced noise estimation algorithms in the context of imaging of rheumatic diseases is possible.

Dual-energy CT in the differentiation of crystal depositions of the wrist: does it have added value?

OBJECTIVES: To evaluate the ability of dual-energy computed tomography (DECT) to improve diagnostic discrimination between gout and other crystal arthropathies such as calcium pyrophosphate deposition disease (CPPD) of the wrist in a clinical patient population. MATERIALS AND METHODS: This retrospective case-control study included 29 patients with either gout (case group; n = 9) or CPPD (control group; n = 20) who underwent DECT of the wrist for clinically suspected crystal arthropathy. Color-coded urate and enhanced calcium as well as virtual 120 kVe blended images were reconstructed from the DECT datasets. Two independent and blinded readers evaluated each reconstructed dataset for the presence of depositions in 17 predefined regions. Additionally, a global diagnosis was made first for 120 kVe images only, based solely on morphologic criteria, and subsequently for all reconstructed images. RESULTS: Sensitivity for the global diagnosis of gout was 1.0 (95% CI 0.63-1) for both DECT and 120 kVe images with specificities of 0.70 (95% CI 0.46-0.87) for DECT and 0.80 (95% CI 0.56-0.93) for 120 kVe images. Color-coded DECT images did not detect more depositions than monochrome standard CT images. CONCLUSION: Discrimination of crystal arthropathies of the wrist is limited using DECT and primarily relying on color-coded images. Evaluation of morphologic criteria on standard CT images is essential for accurate diagnosis.

Low-dose computed tomography as diagnostic tool in calcium pyrophosphate deposition disease arthropathy: focus on ligamentous calcifications of the wrist.

OBJECTIVES: To identify specific morphologic features of calcium pyrophosphate deposition disease (pseudogout, CPPD) manifestations of the wrist as detected using low-dose CT-scans. METHODS: In this retrospective study 46 patients with arthritis of the wrist were included. All patients underwent a low dose CT scan of both wrists on a 320-row detector in volume scan mode. Individual radiation exposure was recorded for all patients. Two blinded raters independently evaluated osteoarthritis, cysts, erosions, calcifications (cartilage and ligaments separately) and carpal misalignment in 33 specified locations. An expert rheumatologist classified the patients as CPPD positive or negative. Fisher's exact test was applied to identify differences between both groups. Receiver operating characteristics (ROC) analyses with calculations of area under the curve (AUC) were carried out for both in the literature established and newly identified imaging findings for each rater individually. RESULTS: Twenty-seven patients were classified as CPPD, 19 patients as other diagnoses. Ligamentous calcifications were significantly more prevalent in the CPPD group (p<0.05). All non-ligamentous findings revealed no difference in frequency. AUC analysis for established findings (0.675; 0.619 - rater 1; 2) vs. ligamentous calcifications (0.786 both raters) showed a markedly higher diagnostic accuracy for the latter. Effective radiation exposure was determined to be 0.019-0.095 mSv per patient. CONCLUSIONS: Calcifications of carpal ligaments are highly specific morphologic features of CPPD arthropathy. Low-dose CT is a useful tool to detect these calcifications at a radiation exposure similar to a standard radiograph.

Diagnostic accuracy of dual-energy computed tomography and joint aspiration: a prospective study in patients with suspected gouty arthritis.

OBJECTIVES: To validate the diagnostic benefit of dual-energy computed tomography (DECT) and synovial fluid aspiration in suspected gout. METHODS: A total of 43 patients with suspected gout underwent aspiration and DECT (320-row CT; Canon Medical Systems, Japan). The patients were assessed (gout vs. non-gout) based on the 2015 ACR/EULAR gout classification criteria using clinical and laboratory findings. The results were analysed by comparing two scenarios using McNemar test: Scenario A: ACR/EULAR criteria, followed by DECT results and aspiration findings. Scenario B: ACR/EULAR criteria, followed by aspiration and DECT results. RESULTS: 15/43 patients (34.9%) were positive for MSU crystals, and 16/43 patients (37.2%) for gouty tophi (DECT). 26/43 patients (60.5%) were diagnosed with gout and fulfilled the ACR/EULAR criteria. The diagnostic performance of either synovial fluid aspiration or DECT was similar with sensitivity of 58% and specificity of 100% and 94%, respectively. Combination of both modalities (at least one of them positive), resulted in increased sensitivity of 85% and unchanged specificity (94%). Based only on clinical and laboratory findings, 13/43 patients (30.2%) were classified as gout according to ACR/EULAR criteria. In scenario A, additional 8 out of 30 (26.7%) patients were diagnosed as gout by DECT findings, and another 5/22 (22.7%) patients by aspiration findings. In scenario B, initial consideration of aspiration findings resulted in 10 out of 30 (33.3%) additionally identified patients, and another 3 (15%) patients by DECT findings. There was no relevant difference between scenarios A and B (p=0.508). CONCLUSIONS: Combination of joint aspiration and DECT improves the diagnostic algorithm for gout. In our attempt to establish an optimal sequence of diagnostic tests, we did not identify an advantage for either synovial fluid analysis or DECT as the initially better modality after clinical examination and analysis of blood tests.