Fluorescence-optical imaging as a promising easy-to-use imaging biomarker to increase early psoriatic arthritis detection in patients with psoriasis: a cross-sectional cohort study with follow-up

Molecular imaging of psoriatic arthritis

PURPOSE OF REVIEW

Psoriatic arthritis (PsA) is a chronic inflammatory disease associated with psoriasis. Conventional imaging techniques are used to diagnose the disease and detect long-term structural changes. This review will assess molecular imaging in PsA, to evaluate its potential additive value over conventional and advanced anatomical imaging methods (e.g. ultrasound and MRI).

RECENT FINDINGS

Current research is primarily focused on the molecular imaging technique PET/computed tomography (PET/CT) imaging, in which different tracers have been investigated. Fluorodeoxyglucose (FDG) can visualize disease activity and subclinical inflammation. New tracers targeting inflammatory sites have also been studied, such as FAPI (fibroblast activation protein inhibitor). Moreover, NaF (sodium fluoride) shows promise for imaging of new bone formation. Next to PET/CT, also fluorescence imaging and multispectral optoacoustic tomography have been investigated in the context of PsA.

SUMMARY

Molecular imaging techniques hold promise for early diagnosis, monitoring and management of PsA. Future research is needed to define the role of molecular imaging relative to conventional and anatomical imaging techniques in patient care.

Optical spectral transmission to monitor disease activity in arthritis patients: longitudinal follow-up comparison with clinical parameters

OBJECTIVE

To examine the longitudinal associations of optical spectral transmission (OST) with clinical inflammatory arthritis activity markers in order to investigate its potential in monitoring disease activity.

METHODS

OST measurements were performed in 1312 wrist and finger joints of 60 patients with clinical suspicion of inflammatory activity, within the context of known rheumatic inflammatory diseases at two separate time intervals. In each time point, patients underwent additional clinical and laboratory examinations. The change of OST values was statistically compared with changes in clinical activity parameters like DAS28 and swollen joint counts (SJC). Additionally, the diagnostic performance of OST was assessed in comparison to a historic control group (2508 joints of 114 healthy subjects) using receiver operating characteristics (ROC). The relationships between OST values, clinical and laboratory parameters, as well as patient characteristics, were evaluated through correlation analyses.

RESULTS

Mean OST scores were significantly higher in the inflammatory arthritis group compared with the control group (P < 0.001). OST correlated significantly with clinical activity markers like DAS28, SJC and TJC in both time points (all; P < 0.05). Longitudinal changes of OST values (ΔOST) were significantly associated with changes in DAS28 (ΔDAS28) (r = 0.377; P = 0.004) and ΔSJC (r = 0.488; P < 0.001) over the same time period. The area under the curve of the baseline receiver operating characteristic curve was 0.781 (95%CI 0.82-0.94).

CONCLUSION

OST was able to reliably assess disease activity and correlated longitudinally with arthritis activity markers, showing promising potential during monitoring of inflammatory arthritis.

Diagnostic performance of optical spectral transmission compared to magnetic resonance imaging in patients with inflammatory arthritis

BACKGROUND

Optical spectral transmission (OST) is a modern diagnostic method capable of quantifying inflammation in the finger and wrist joints of arthritis patients by assessing the blood-specific absorption of light transmitted through a tissue. The diagnostic performance of this modality has not been adequately examined and data regarding OST associations with magnetic resonance imaging (MRI) are limited. Aim of this study was therefore to investigate the performance of OST in assessing joint inflammation as compared to MRI in patients with inflammatory arthritis (IA).

METHODS

Data from patients who underwent MRI and OST for suspected IA were analyzed. For comparison, a historical healthy control (HC) group with OST was also accounted. MRI findings were quantified using the Rheumatoid Arthritis MRI Score (RAMRIS). Diagnostic accuracy of OST was evaluated using Receiver Operating Characteristics (ROC), while correlation analyses were conducted to explore relationships between OST and MRI, as well as disease activity markers.

RESULTS

Overall, 71 patients with known rheumatic diseases (n = 1,542 wrist and finger joints) and 114 HC (n = 2,508 joints) subjects were included. 51 patients showed inflammatory signs on MRI (MRI+). These also showed significantly higher OST scores (16.41 ± 5.53) than subjects without MRI inflammation (MRI-) (11.52 ± 5.03) or HC (10.78 ± 4.19) (all; p < 0.001). OST showed significant correlations with RAMRIS-synovitis and tenosynovitis scores in the MRI + group (rho = 0.541, p < 0.001; rho = 0.341, p = 0.01, respectively). Significant correlations were observed between OST and clinical parameters for disease activity. Using MRI as a reference, the best diagnostic value of OST was observed at the wrist level in the MRI + group, by an AUC of 0.833 (95%CI 0.700-0.966).

CONCLUSION

OST showed an excellent performance compared to MRI and correlated significantly with RAMRIS scores and clinical parameters in IA patients, also differentiating IA from HC.

Unconventional Imaging Methods in Psoriatic Arthritis

PURPOSE OF REVIEW

Psoriatic arthritis (PsA) is a complex heterogeneous inflammatory disease that affects about one-third of patients with psoriasis. PsA leads to significant physical impairment and reduced quality of life. Therefore, early diagnosis and intervention are critical for improving long-term outcomes. The purpose of this review is to highlight the advantages of unconventional imaging methods in the diagnosis and management of PsA and to discuss recent advancements in imaging technology.

RECENT FINDINGS

Conventional imaging methods, such as radiography, musculoskeletal ultrasound, and magnetic resonance imaging, have been instrumental in detecting structural joint damage and inflammation. However, these imaging modalities have several limitations, resulting in their inability to detect early disease changes. Recent advancements in imaging technology have led to the development of novel imaging modalities capable of characterizing not only early structural but also molecular aspects of disease activity. These cutting-edge approaches have been lately applied to both psoriasis and PsA patients, offering new insights into disease progression, the transition from psoriasis to PsA, and treatment responses. By providing more detailed and individualized assessments, unconventional imaging modalities may bring us closer to realizing the potential of personalized medicine in the management of PsA.

Imaging in psoriatic arthritis: established methods and emerging techniques

Psoriatic arthritis (PsA) is a heterogeneous, chronic, inflammatory musculoskeletal disease that can lead to peripheral and axial damage and loss of function. A clear difference between PsA and other forms of inflammatory arthritis is the different forms of bone remodeling seen in PSA which incorporates not only increased bone resorption with bone erosions, osteolysis, and loss of bone mineral density but also increased bone formation with periostitis, syndesmophytes, enthesiophytes, and ankylosis. PsA, if diagnosed late, will lead to significant structural damage, the most severe form of which is known as arthritis mutilans, and loss of physical function. Imaging plays a crucial role in diagnosing and monitoring both peripheral and axial conditions associated with PsA. Radiography is currently the main modality used to monitor structural damage in PsA though commonly used scoring systems do not include bony proliferation as a criterion. Besides, radiography is limited in determining the presence and cause of periarticular soft tissue thickening, which may arise from tendinosis, tenosynovitis, synovial proliferation, bursitis, or enthesitis. Recently, much more attention has been paid to determining the imaging characteristics of PsA, which enables more precise identification of disease and severity assessment. Newer imaging technologies also enable variations in normal bone microstructure to be distinguished from disease-related abnormality. This review discusses the current state of innovative imaging modalities in PsA, specifically concentrating on their roles in PsA diagnosis and treatment, improving the early detection of PsA, and identifying patients with skin psoriasis at risk of developing psoriatic arthritis.

Metabolic and molecular imaging in inflammatory arthritis

It is known that metabolic shifts and tissue remodelling precede the development of visible inflammation and structural organ damage in inflammatory rheumatic diseases such as the inflammatory arthritides. As such, visualising and measuring metabolic tissue activity could be useful to identify biomarkers of disease activity already in a very early phase. Recent advances in imaging have led to the development of so-called 'metabolic imaging' tools that can detect these changes in metabolism in an increasingly accurate manner and non-invasively.Nuclear imaging techniques such as 18F-D-glucose and fibroblast activation protein inhibitor-labelled positron emission tomography are increasingly used and have yielded impressing results in the visualisation (including whole-body staging) of inflammatory changes in both early and established arthritis. Furthermore, optical imaging-based bedside techniques such as multispectral optoacoustic tomography and fluorescence optical imaging are advancing our understanding of arthritis by identifying intra-articular metabolic changes that correlate with the onset of inflammation with high precision and without the need of ionising radiation.Metabolic imaging holds great potential for improving the management of patients with inflammatory arthritis by contributing to early disease interception and improving diagnostic accuracy, thereby paving the way for a more personalised approach to therapy strategies including preventive strategies. In this narrative review, we discuss state-of-the-art metabolic imaging methods used in the assessment of arthritis and inflammation, and we advocate for more extensive research endeavours to elucidate their full field of application in rheumatology.

Fluorescence optical imaging feature selection with machine learning for differential diagnosis of selected rheumatic diseases

Background and objective

Accurate and fast diagnosis of rheumatic diseases affecting the hands is essential for further treatment decisions. Fluorescence optical imaging (FOI) visualizes inflammation-induced impaired microcirculation by increasing signal intensity, resulting in different image features. This analysis aimed to find specific image features in FOI that might be important for accurately diagnosing different rheumatic diseases.

Patients and methods

FOI images of the hands of patients with different types of rheumatic diseases, such as rheumatoid arthritis (RA), osteoarthritis (OA), and connective tissue diseases (CTD), were assessed in a reading of 20 different image features in three phases of the contrast agent dynamics, yielding 60 different features for each patient. The readings were analyzed for mutual differential diagnosis of the three diseases (One-vs-One) and each disease in all data (One-vs-Rest). In the first step, statistical tools and machine-learning-based methods were applied to reveal the importance rankings of the features, that is, to find features that contribute most to the model-based classification. In the second step machine learning with a stepwise increasing number of features was applied, sequentially adding at each step the most crucial remaining feature to extract a minimized subset that yields the highest diagnostic accuracy.

Results

In total, n = 605 FOI of both hands were analyzed (n = 235 with RA, n = 229 with OA, and n = 141 with CTD). All classification problems showed maximum accuracy with a reduced set of image features. For RA-vs.-OA, five features were needed for high accuracy. For RA-vs.-CTD ten, OA-vs.-CTD sixteen, RA-vs.-Rest five, OA-vs.-Rest eleven, and CTD-vs-Rest fifteen, features were needed, respectively. For all problems, the final importance ranking of the features with respect to the contrast agent dynamics was determined.

Conclusions

With the presented investigations, the set of features in FOI examinations relevant to the differential diagnosis of the selected rheumatic diseases could be remarkably reduced, providing helpful information for the physician.