Computed tomography-current status and future directions for arthritis imaging.

Applications of computed tomography (CT) in arthritis imaging have rapidly expanded in recent years due to ongoing technical developments. Dual-energy CT (DECT) has become indispensable in clinical practice, particularly for diagnosing gouty arthritis and assessing bony structural changes. Technological innovations such as low-dose CT and state-of-the-art reconstruction algorithms reduce radiation exposure while maintaining image quality and short acquisition times. This review explores the growing role of CT in arthritis imaging. Recent innovations have extended DECT's utility beyond gout diagnosis to the detection of inflammatory changes in various arthritic conditions. Postprocessing techniques such as the generation of subtraction images and iodine maps provide valuable insights into tissue perfusion and inflammatory activity, crucial for arthritis management. DECT can distinguish calcium from uric acid crystals, facilitating the differential diagnosis of various crystal arthropathies in a variety of clinical settings. This ability is particularly valuable in distinguishing between different clinical conditions in patients with inflammatory joint changes within a single imaging examination. Moreover, the advent of four-dimensional CT promises a better assessment of dynamic joint instabilities and ligament injuries, especially in the wrist. Overall, DECT offers a comprehensive approach to arthritis imaging, from the detection of structural changes to the assessment of active inflammation in joints and tendons. Continuous advances in CT technology, including photon-counting CT, hold promise for further improving diagnostic accuracy and expanding the role of CT in arthritis imaging and therapy monitoring.

Learning imaging in axial spondyloarthritis: more than just a matter of experience.

OBJECTIVE: Reliable interpretation of imaging findings is essential for the diagnosis of axial spondyloarthritis (axSpA) and requires a high level of experience. We investigated experience-dependent differences in diagnostic accuracies using X-ray (XR), MRI and CT. METHODS: This post hoc analysis included 163 subjects with low back pain. Eighty-nine patients had axSpA, and 74 patients had other conditions (mechanical, degenerative or non-specific low back pain). Final diagnoses were established by an experienced rheumatologist before the reading sessions. Nine blinded readers (divided into three groups with different levels of experience) scored the XR, CT and MRI of the sacroiliac joints for the presence versus absence of axSpA. Parameters for diagnostic performance were calculated using contingency tables. Differences in diagnostic performance between the reader groups were assessed using the McNemar test. Inter-rater reliability was assessed using Fleiss kappa. RESULTS: Diagnostic performance was highest for the most experienced reader group, except for XR. In the inexperienced and semi-experienced group, diagnostic performance was highest for CT&MRI (78.5% and 85.3%, respectively). In the experienced group, MRI showed the highest performance (85.9%). The greatest difference in diagnostic performance was found for MRI between the inexperienced and experienced group (76.1% vs 85.9%, p=0.001). Inter-rater agreement was best for CT in the experienced group with κ=0.87. CONCLUSION: Differences exist in the learnability of the imaging modalities for axSpA diagnosis. MRI requires more experience, while CT is more suitable for inexperienced radiologists. However, diagnosis relies on both clinical and imaging information.

New Bone Formation in Axial Spondyloarthritis: A Review.

BACKGROUND: Axial spondyloarthritis (axSpA) is a chronic inflammatory disease primarily affecting the sacroiliac joints (SIJs) and the spine. Imaging plays a crucial role in the diagnosis of axSpA, with magnetic resonance imaging (MRI) and radiography being the primary modalities used in clinical practice. New bone formation occurs in both the spine (non-bridging and bridging syndesmophytes, transdiscal ankylosis, and ankylosis of small joints and posterior elements) and the SIJs (backfill and ankylosis). New bone formation indicates advanced axSpA. METHOD: This review explores the role of imaging in the diagnosis and monitoring of axSpA, focusing on the significance of new bone formation, and provides an overview of the characteristic imaging findings of new bone formation in axSpA in each imaging modality. CONCLUSION: Imaging methods, such as X-ray, MRI, and CT, have different diagnostic accuracies for detecting structural lesions and new bone formation. Each modality has its strengths and weaknesses, and the choice depends on the specific clinical context. Imaging is crucial for the diagnosis and monitoring of axSpA, particularly for the detection of new bone formation. Different imaging techniques provide valuable information about disease progression and treatment response. Understanding the significance of new bone formation and its detection using imaging modalities is essential for the accurate diagnosis and effective management of patients with axSpA. KEY POINTS: · New bone formation is a hallmark feature of advanced axial spondyloarthritis.. · New bone formation occurs both in the spine and in the sacroiliac joints.. · Differentiation of new bone formation in axial spondyloarthritis from that in other conditions such as diffuse idiopathic skeletal hyperostosis and from osteophytes is essential.. · Imaging methods, such as X-ray, MRI, and CT, have different diagnostic accuracies for detecting new bone formation..

Sex-specific diagnostic efficacy of MRI in axial spondyloarthritis: challenging the 'One Size Fits All' notion.

OBJECTIVES: Sex-specific differences in the presentation of axial spondyloarthritis (axSpA) may contribute to a diagnostic delay in women. The aim of this study was to investigate the diagnostic performance of MRI findings comparing men and women. METHODS: Patients with back pain from six different prospective cohorts (n=1194) were screened for inclusion in this post hoc analysis. Two blinded readers scored the MRI data sets independently for the presence of ankylosis, erosion, sclerosis, fat metaplasia and bone marrow oedema. Χ2 tests were performed to compare lesion frequencies. Contingency tables were used to calculate markers for diagnostic performance, with clinical diagnosis as the standard of reference. The positive and negative likelihood ratios (LR+/LR-) were used to calculate the diagnostic OR (DOR) to assess the diagnostic performance. RESULTS: After application of exclusion criteria, 526 patients (379 axSpA (136 women and 243 men) and 147 controls with chronic low back pain) were included. No major sex-specific differences in the diagnostic performance were shown for bone marrow oedema (DOR m: 3.0; f: 3.9). Fat metaplasia showed a better diagnostic performance in men (DOR 37.9) than in women (DOR 5.0). Lower specificity was seen in women for erosions (77% vs 87%), sclerosis (44% vs 66%), fat metaplasia (87% vs 96%). CONCLUSION: The diagnostic performance of structural MRI markers is substantially lower in female patients with axSpA; active inflammatory lesions show comparable performance in both sexes, while still overall inferior to structural markers. This leads to a comparably higher risk of false positive findings in women.

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.

HLA-B27 status and inflammatory MRI lesions of the sacroiliac joints: a post hoc analysis in patients without axial spondyloarthritis.

OBJECTIVE: The assessment of inflammatory and structural lesions in the sacroiliac joint (SIJ) is crucial in axial spondyloarthritis (axSpA). HLA-B27 status plays an important role in axSpA diagnosis and has been linked to MRI lesion burden in the general population. We aimed to investigate the sex-specific influence of HLA-B27 status on inflammatory and structural MRI findings in patients with low back pain of non-inflammatory origin. METHODS: This post hoc analysis included 139 non-axSpA patients (90 women) with chronic low back pain. Two readers scored MRIs of the SIJ for the presence of sclerosis, erosion, fat metaplasia, bone marrow oedema (BMO) and ankylosis. Frequencies and extent of lesions were compared regarding the HLA-B27 status using χ2 tests and t-tests. Regression models to assess the sex-dependent influence of HLA-B27 on lesion burden were computed. RESULTS: HLA-B27 was positive in 33 women (36.7%) and 23 men (46.9%). The overall occurrence of all SIJ lesions did not differ in HLA-B27 negative and positive individuals. There were no significant differences in the extent of lesions considering the HLA-B27 positivity, for erosion (mean sum score (MSS) of 0.91 vs 0.48; p=0.144), sclerosis (MSS 1.65 vs 1.88; p=0.576), fat metaplasia (MSS 0.56 vs 0.27; p=0.425), BMO (MSS 0.75 vs 0.59; p=0.460) and ankylosis (MSS 0.06 vs 0.04; p=0.659). CONCLUSION: HLA-B27 status has no significant influence on the occurrence and extent of SIJ lesions in patients with low back pain of non-inflammatory origin in either men or women.

Four-dimensional computed tomography detects dynamic three-dimensional pathologies of the wrist in patients with calcium pyrophosphate deposition disease.

Objectives: Crystal deposits in ligaments of the wrist are typical findings in patients with calcium pyrophosphate deposition (CPPD) disease. CPPD crystals trigger inflammation and ultimately result in ligament tears with scapholunate (SL) advanced collapse (SLAC). This study aimed to investigate carpal instabilities in patients with CPPD using four-dimensional computed tomography (4D-CT) of the wrist. Methods: This IRB-approved prospective feasibility study investigated patients with CPPD of the hand. All patients underwent a static 3D-CT and two dynamic 4D-CT in ulnar- and radial abduction and in supination and pronation movements to analyze instabilities of the SL region and of the distal radioulnar joint (DRUJ). Two independent readers scored the images for the presence of SL ligament and triangular fibrocartilage complex (TFCC) calcifications. Furthermore, the readers assessed the dynamic images for SL and DRUJ instabilities. Descriptive analyses were performed. Inter-rater reliability was assessed using Cohen's kappa (κ). Results: Nine patients were included. SL ligament calcifications and instabilities were found in all patients. Of these, dynamic SL instability was detected in 77.8% of the patients, while 22.2% had a SLAC wrist. TFCC calcifications were found in 87.5% of the patients. Four patients had DRUJ instability (50%). No patient showed DRUJ instability without the presence of TFCC calcifications. Agreement between readers for calcifications was excellent (κ = 1) and almost perfect (κ = 0.89) for instabilities. Conclusion: This study provides the first evidence of relevant dynamic carpal instability in CPPD patients using advanced imaging techniques with 4D-CT, offering unique insights into wrist biomechanics.

Influence of contrast medium on tophus detection using dual-energy CT: phantom study and clinical illustration.

BACKGROUND: To investigate the influence of iodinated contrast medium (ICM) on detection of monosodium urate (MSU) with dual-energy computed tomography (DECT) in two types of phantoms and demonstrate an example patient for clinical illustration. METHODS: Approval is by the institutional review board, and written informed consent was obtained. A grid-like and a biophantom with 25 suspensions containing different concentrations of ICM (0 to 2%) and MSU (0 to 50%) were prepared and scanned with sequential single-source DECT using established methodology. Ascending orders of tube currents were applied at 80 kVp (16.5 to 220.0 mAs) and 135 kVp (2.75 to 19.25 mAs). Volume and mass measurements were performed using clinical gout software (dual-energy decomposition analysis). Numbers of true-positive and false-positive MSU detections were recorded and compared for different ICM concentrations. We demonstrate a patient with gouty arthritis for clinical illustration. RESULTS: Effects of ICM on MSU detection varied with the amount of iodine. Lower ICM concentrations (0.25 and 0.50%) improved detection of small uric acid concentrations of 35 to 45% in comparison to scans without ICM. However, high ICM concentrations (1 and 2%) almost completely precluded MSU detection for all MSU concentrations investigated. In a patient with gouty arthritis, tophi in the wrist were only detected after intravenous ICM administration. CONCLUSIONS: Exploring multimodal DECT for arthritis imaging, enhancement of ICM influences tophus detection. It can help in visualizing previously undetected MSU depositions but, with too strong enhancement, also obscure tophi. RELEVANCE STATEMENT: Use of iodinated contrast media in dual-energy CT might help in visualizing previously undetected uric acid depositions but, with too strong enhancement, obscure gouty tophi. KEY POINTS: • Iodine significantly influences the uric acid crystal detection in systematic phantom studies. • Lower iodine concentrations improved detection of low and medium uric acid concentrations. • High concentrations of iodine hampered detection of all uric acid concentrations.

Sex Disparities of the Sacroiliac Joint: Focus on Joint Anatomy and Imaging Appearance.

The sacroiliac joint (SIJ) is an anatomically complex joint which, as a functional unit with the pelvis and spine, is of decisive biomechanical importance for the human body. It is also a commonly overlooked source of lower back pain. Like the entire bony pelvis, the SIJ exhibits major sexual dimorphisms; thus, the sex-dependent evaluation of this joint is becoming increasingly important in clinical practice, both anatomically with joint shape variations and biomechanical differences as well as in terms of image appearance. The influence of the SIJ shape, which differs in women and men, is crucial for the different biomechanical joint properties. These differences are important in the development of joint diseases at the SIJ, which shows a specific difference between the sexes. This article aims to provide an overview of sex disparities of the SIJ regarding different anatomical and imaging appearances to further understand the insights into the interplay of sex differences and SIJ disease.

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.

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.

Dual-Energy Computed Tomography Collagen Density Mapping of the Cranio-Cervical Ligaments-A Retrospective Feasibility Study.

The objectives of this study were to investigate the mean collagen content of the atlanto-axial joint (AAJ) ligaments in a cohort without inflammatory disease and to analyze clinical confounders such as age, sex, and presence of ligamentous calcifications. A total of 153 patients who underwent dual-energy computed tomography (DECT) due to various reasons (e.g., suspected cancer or infection) were included in this retrospective study. Reconstruction of collagen density maps from the DECT dataset was performed. Region of interest (ROI) analysis was performed to assess densities in the following regions: ligamentum transversum atlantis (LTA), ligamenta alaria, fasciculi longitudinales, ligamentum nuchae, and retro-odontoid soft tissue (RDS). Osteoarthritis (OA) and the presence of calcifications were assessed by two experienced readers blinded to clinical data. Subgroup comparisons were performed using unpaired t-tests. The correlation of collagen density and clinical factors was investigated using Pearson's correlation coefficient. Mean LTA collagen density was 141.7 (SD 35.7). Ligamentous calcifications were rare (14.4 %). OA of the AAJ was common (91.5 %). LTA collagen density was not associated with age (Pearson's r of 0.109; p = 0.180) and was not significantly higher in patients with OA (p = 0.070). No correlations between RDS thickness, collagen density or calcifications were found. Our results show collagen density mapping of the cranio-cervical joint ligaments to be feasible; collagen densities are not significantly associated with age, sex, AAJ degeneration, or asymptomatic ligamentous calcification.

Virtual Monochromatic Images from Dual-Energy Computed Tomography Do Not Improve the Detection of Synovitis in Hand Arthritis.

The objective of this study was to investigate subtraction images from different polychromatic and virtual monochromatic reconstructions of dual-energy computed tomography (CT) for the detection of inflammation (synovitis/tenosynovitis or peritendonitis) in patients with hand arthritis. In this IRB-approved prospective study, 35 patients with acute hand arthritis underwent contrast-enhanced dual-energy CT and musculoskeletal ultrasound (MSUS) of the clinically dominant hand. CT subtractions (CT-S) were calculated from 80 and 135 kVp source data and monochromatic 50 and 70 keV images. CT-S and MSUS were scored for synovitis and tenosynovitis/peritendonitis. Specificity, sensitivity and diagnostic accuracy were assessed by using MSUS as a reference. Parameters of objective image quality were measured. Thirty-three patients were analyzed. MSUS was positive for synovitis and/or tenosynovitis/peritendonitis in 28 patients. The 70 keV images had the highest diagnostic accuracy, with 88% (vs. 50 keV, 82%; 80 kVp, 85%; and 135 kVp, 82%), and superior sensitivity, with 96% (vs. 50 keV: 86%, 80 kVp: 93% and 135 kVp: 79%). The 80 kVp images showed the highest signal- and contrast-to-noise ratio, while the 50 keV images provided the lowest image quality. While all subtraction methods of contrast-enhanced dual-energy CT proved to be able to detect inflammation with sufficient diagnostic accuracy, virtual monochromatic images with low keV showed no significant improvement over conventional subtraction techniques and lead to a loss of image quality.

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.

CT-like images in MRI improve specificity of erosion detection in patients with hand arthritis: a diagnostic accuracy study with CT as standard of reference.

OBJECTIVE: To compare the diagnostic accuracy of susceptibility-weighted imaging (SWI), standard T1-weighted (T1w) images and high-resolution 3D-gradient echo sequences (volumetric interpolated breath-hold examination (VIBE)) for detection of erosions in patients with peripheral arthritis using CT as standard of reference. MATERIALS AND METHODS: A total of 36 patients were included in the study. All patients underwent CT and MRI, including SWI, VIBE and T1w sequences of the clinically more affected hand. Two trained readers scored all imaging datasets separately for erosions in a blinded fashion. Specificity, sensitivity and diagnostic accuracy of MRI sequences were calculated on a per-patient level. RESULTS: CT was positive for erosion in 16 patients and 77 bones (Rheumatoid Arthritis MRI Score >0), T1w in 28 patients, VIBE in 25 patients and SWI in 17 patients. All MRI sequences performed with comparably high sensitivities (T1w 100%, VIBE 94% and SWI 94%). SWI had the highest specificity of 90%, followed by VIBE (50%) and T1w (40%). Both T1w and VIBE produced significantly higher sum scores than CT (341 and 331 vs 148, p<0.0001), while the sum score for SWI did not differ from CT (119 vs 148; p=0.411). CONCLUSION: Specificity for erosion detection remains a challenge for MRI when conventional and high-resolution sequences are used but can be improved by direct bone depiction with SWI. Both T1w and VIBE tend to overestimate erosions, when CT is used as the standard of reference.

Fractal analysis of perfusion imaging in synovitis: a novel imaging biomarker for grading inflammatory activity based on assessing angiogenesis.

OBJECTIVES: The mutual and intertwined dependence of inflammation and angiogenesis in synovitis is widely acknowledged. However, no clinically established tool for objective and quantitative assessment of angiogenesis is routinely available. This study establishes fractal analysis as a novel method to quantitatively assess inflammatory activity based on angiogenesis in synovitis. METHODS: First, we established a pathophysiological framework for synovitis including fractal analysis of software perfusion phantoms, which allowed to derive explainability with a known and controllable reference standard for vascular structure. Second, we acquired MRI datasets of patients with suspected rheumatoid arthritis of the hand, and three imaging experts independently assessed synovitis analogue to Rheumatoid Arthritis MRI Scoring (RAMRIS) criteria. Finally, we performed fractal analysis of dynamic first-pass perfusion MRI in vivo to evaluate angiogenesis in relation to inflammatory activity with RAMRIS as reference standard. RESULTS: Fractal dimension (FD) achieved highly significant discriminability for different degrees of inflammatory activity (p<0.01) in software phantoms with known ground-truth of angiogenic structure. FD indicated increasingly chaotic perfusion patterns with increasing grades of inflammatory activity (Spearman's ρ=0.94, p<0.001). In 36 clinical patients, fractal analysis quantitatively and objectively discriminated individual RAMRIS scores (p≤0.05). Area under the receiver-operating curve was 0.84 (95% CI 0.7 to 0.89) for fractal analysis when considering RAMRIS as ground-truth. Fractal analysis additionally identified angiogenesis in cases where RAMRIS underestimated inflammatory activity. CONCLUSIONS: Based on angiogenesis and perfusion pathophysiology, fractal analysis non-invasively enables comprehensive, objective and quantitative characterisation of inflammatory angiogenesis with subjective and qualitative RAMRIS as reference standard. Further studies are required to establish the clinical value of fractal analysis for diagnosis, prognostication and therapy monitoring in inflammatory arthritis.

[Multicentric Castleman's disease combined with polyserositis and POEMS syndrome: case report and review article]. / Multizentrische Castleman-Erkrankung in Kombination mit Polyserositis und POEMS-Syndrom ­ Fallbericht und Übersichtsbeitrag.

Castleman disease (CD) is a very rare disorder characterised by hyperplasia of the lymphoid tissue. The aetiology varies considerably and includes autoimmunological, infectious, autoinflammatory and paraneoplastic diseases (e.g. MGUS with POEMS syndrome). What they all have in common is usually a dysregulation/overproduction of certain cytokines and growth factors (including interleukin 6 and VEGF). The sum of these changes sometimes causes very heterogeneous symptoms and thus often makes early diagnosis difficult. The prognosis of unrecognised and untreated disease is very serious and has an average 5­year survival rate of 55-77%. The present paper describes the case of a 79-year-old patient with refractory polyserositis who was correctly diagnosed after > 8 years.

Perfusion in hand arthritis on dynamic contrast-enhanced computed tomography: a randomized prospective study using MRI as a standard of reference.

OBJECTIVE: To evaluate the performance of dynamic contrast-enhanced CT (DCE-CT) in detecting and quantitatively assessing perfusion parameters in patients with arthritis of the hand compared with dynamic contrast-enhanced MRI (DCE-MRI) as a standard of reference. MATERIALS AND METHODS: In this IRB-approved randomized prospective single-centre study, 36 consecutive patients with suspected rheumatoid arthritis underwent DCE-CT (320-row, tube voltage 80 kVp, tube current 8.25 mAs) and DCE-MRI (1.5 T) of the hand. Perfusion maps were calculated separately for mean transit time (MTT), time to peak (TTP), relative blood volume (rBV), and relative blood flow (rBF) using four different decomposition techniques. Region of interest (ROI) analysis was performed in metacarpophalangeal joints II-V and in the wrist. Pairs of perfusion parameters in DCE-CT and DCE-MRI were compared using a two-tailed t test for paired samples and interpreted for effect size (Cohen's d). According to the Rheumatoid Arthritis Magnetic Resonance Imaging Score (RAMRIS) scoring results, differentiation of synovitis-positive and synovitis-negative joints with both modalities was assessed with the independent t test. RESULTS: The two modalities yielded similar perfusion parameters. Identified differences had small effects (d 0.01-0.4). DCE-CT additionally differentiates inflamed and noninflamed joints based on rBF and rBV but tends to underestimate these parameters in severe inflammation. The total dose-length product (DLP) was 48 mGy*cm with an estimated effective dose of 0.038 mSv. CONCLUSION: DCE-CT is a promising imaging technique in arthritis. In patients with a contraindication to MRI or when MRI is not available, DCE-CT is a suitable alternative to detect and assess arthritis.

Ultra-low-dose CT detects synovitis in patients with suspected rheumatoid arthritis.

PURPOSE: To prove the feasibility and measure the diagnostic accuracy of contrast-enhanced ultra-low-dose CT (ULD-CT) for the depiction of inflammatory soft-tissue changes (synovitis, tenosynovitis and peritendonitis) in patients with arthritis of the hand. MATERIALS AND METHODS: In this institutional review board-approved study, 36 consecutive patients over the age of 50 with suspected rheumatoid arthritis underwent ULD-CT (estimated radiation exposure <0.01 mSv) and MRI of the hand with weight-adapted intravenous contrast administration. ULD-CT subtraction and MR images were assessed for synovitis, tenosynovitis and peritendonitis by three readers using a modified Rheumatoid Arthritis MRI Score (RAMRIS). Patients were asked which modality they would prefer for future examinations. Sensitivity and specificity of ULD-CT for detection of inflammatory changes were calculated using MRI as standard of reference. The sum scores were correlated using Pearson's r. RESULTS: All 36 patients showed synovitis in MRI. ULD-CT had 69% sensitivity on the patient level and 65% on the joint level with 87% specificity. Sensitivity was higher in patients with more severe inflammation (80% for MRI RAMRIS >1). There was almost perfect correlation between the modified RAMRIS sum scores of ULD-CT and MRI (Pearson's r=0.94). Regarding preferences for future examinations, 85% preferred ULD-CT over MRI. ULD-CT detected more differential diagnoses than MRI (8 vs 2/12). CONCLUSION: Contrast-enhanced ULD-CT of the hand allows for depiction of soft-tissue inflammation at the hand and can be achieved using very low radiation exposure (<0.01 mSv). ULD-CT may evolve to a fast and comfortable alternative to MRI, although it is not as sensitive as MRI for detecting mild disease.