Fluorescence optical imaging in pediatric patients with inflammatory and non-inflammatory joint diseases: a comparative study with ultrasonography

[Can rheuma be scanned? : Review of the current study situation on fluorescence optical imaging]

BACKGROUND

The novel technique of indocyanine green (ICG)-based fluorescence optical imaging (FOI) using the Xiralite® system (Rheumascan) has been the subject of many different studies worldwide since approval for clinical use in the European Union (2009), USA (2014) and Asia. The FOI depicts the disturbed microcirculation in the joints of both hands caused by inflammation.

OBJECTIVE

The aim of this article is to provide an overview of the current state of studies on ICG-based FOI in different rheumatologic indications.

METHODS

A narrative literature review of publications on ICG-based FOI in the diagnosis of various inflammatory rheumatic joint diseases since 2010 is presented, its use in treatment monitoring is explained, and its value in systemic sclerosis is outlined.

RESULTS

In summary, studies have extensively demonstrated the accuracy of FOI in inflammation detection. Therefore, it can be concluded that FOI is a good supplement to existing imaging modalities. Due to characteristic patterns of both skin and nails, FOI is an indicated procedure especially in psoriatic arthritis and can be very helpful in the diagnostic process in early undifferentiated arthritis. The FOI has shown its usefulness in children (juvenile idiopathic arthritis), for monitoring the course of treatment, and for demonstrating disturbed microcirculation in patients with systemic sclerosis.

CONCLUSION

The presented data imply that FOI should be considered as a valuable complementary imaging tool in the diagnostic algorithm of daily rheumatologic practice, both for diagnosis and for follow-up monitoring. In particular, the automated analyses should be able in the future to objectify measurements of inflammatory activity as well as monitoring the response to treatment.

Optical spectral transmission to assess glucocorticoid therapy response in patients with arthritis: a longitudinal follow-up comparison with joint ultrasound

BACKGROUND

Optical spectral transmission (OST) is a modern diagnostic modality, able to assess the blood-specific absorption of light transmitted through a tissue, promising quantification of inflammation in the finger and wrist joints of patients with arthritis. To date, there are no adequate data regarding the diagnostic value of OST in the evaluation of inflammatory activity changes, during arthritis follow-up. Objectives of this study were therefore to examine the performance of OST in assessing response to anti-inflammatory therapy in patients with active arthritis and to explore OST associations with clinical, laboratory, and ultrasonographic (US) activity markers.

METHODS

1173 joints of 54 patients with arthritides of the wrist and finger joints were examined by OST before and after oral administration of glucocorticoids (GC), during a disease flare. For the same time-points patients underwent clinical, laboratory, and joint US [grayscale (GSUS), power-Doppler (PDUS)] examinations. The distribution of ΔOST-values between the two time-points was compared with the respective distributions of ΔPDUS and ΔGSUS by Bayesian statistical analyses. Moreover, the diagnostic performance of OST compared to a control group (2508 joints of 114 subjects) was examined by receiver operating characteristics and associations of OST values with clinical, laboratory, and arthrosonographic parameters were evaluated by correlation analyses.

RESULTS

OST and US performed similarly in the assessment of inflammatory changes caused by GC (same value-change tendency in 83.2% of the cases). Bayesian statistics revealed no significant differences between ΔOST and ΔPDUS for all 3 examined joint categories (accuracy: metacarpophalangeal (MCP): 68.1%; proximal interphalangeal (PIP): 60.4%; wrists: 50.4%) and between ΔOST and ΔGSUS for MCP and PIP joints (accuracy: 51.1% and 78.7%, respectively). OST diagnostic performance (patients vs. controls) was excellent in both time-points [area under the curve (AUC) before GC=0.883(95%CI=0.83-0.94) and after GC=0.811(95%CI=0.74-0.881); p<0.001]. Furthermore, OST correlated significantly with all examined sonographic activity scores (all; p<0.001) and with swollen joint counts (p<0.01).

CONCLUSIONS

OST was able to assess response to therapy in a similar way to joint US and correlated significantly with arthritis activity markers. Therefore, OST has proved to be a valuable tool to assist disease activity monitoring in the examined cohort.

TRIAL REGISTRATION

German Registry of Clinical Trials, DRKS00016752.

Fluorescence optical imaging: ready for prime time?

The novel technique of fluorescence optical imaging (FOI, Xiralite), which is approved in the European Union and the USA for clinical use, has been the object of studies since 2009. Indocyanine green-based FOI can demonstrate an impaired microcirculation caused by inflammation in both hands in one examination. Several studies have investigated FOI for detection of joint inflammation by comparing FOI to magnetic resonance imaging (MRI) and/or musculoskeletal ultrasound (MSUS). The results have shown a generally good agreement (>80%) between FOI and clinical examination, MRI and MSUS by power Doppler in inflammatory joint diseases. Moreover, characteristic enhancements in skin and nails are seen in PsA, which potentially can be useful in the diagnostic process of early undifferentiated arthritis. Furthermore, FOI has been investigated for the visualisation of a disturbed microcirculation in the hands and fingers of patients with systemic sclerosis (SSc), highlighting the potential of monitoring vascular changes in SSc and other vasculopathies. The available data indicate that it is time to consider FOI as a useful part of the imaging repertoire in rheumatology clinical practice, particularly where MSUS and MRI are not easily available.

Fluorescence optical imaging in patients with active rheumatoid arthritis: a comparison with ultrasound and an association with biomarkers

Objectives: This study compared indocyanine green (ICG)-enhanced fluorescence optical imaging (FOI) and musculoskeletal ultrasound (MSUS), and explored the significance of the FOI findings based on the association between the FOI and MSUS findings and serum biomarkers in patients with rheumatoid arthritis (RA). The study also explored the association between the FOI findings and patients' joint destruction at the joint-area level.Method: We enrolled 50 consecutive patients with active RA from among the patients hospitalized from May 2014 to March 2016 at Nagasaki University Hospital, Japan. FOI images were acquired with the Xiralite^® fluorescence imaging system and compared with the patients' clinical examination results and MSUS findings. On the same day, the patients' clinical disease activity and levels of serum biomarkers (including vascular endothelial growth factor) were obtained.Results: Although the FOI detected synovitis with high sensitivity, the frequency of positive findings and the diagnostic performance with MSUS as the reference standard for FOI differed considerably among the phases of FOI as well as among the affected joint regions. The FOI scores were positively correlated with clinical disease activity, MSUS scores, and serum biomarkers. The severity of FOI-proven synovitis was associated with the presence of MSUS-proven bone erosion.Conclusion: FOI is effective for detecting joint inflammation in RA patients, with high accuracy. The severity of the FOI score was closely associated with the joint destruction at the joint-area level. However, the significance of positive FOI findings differed depending on not only the phase of FOI but also the affected joint regions.

Optical and Optoacoustic Imaging Probes

Tissue has characteristic properties when it comes to light absorption and scattering. For optical (OI) and optoacoustic imaging (OAI) these properties can be utilised to visualise biological tissue characteristics, as, for example, the oxygenation state of haemoglobin alters the optical and optoacoustic properties of the molecule.