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Background Long COVID occurs in lower frequency in children and adolescents than in adults. Morphologic and free-breathing phase-resolved functional low-field MRI may identify persistent pulmonary manifestations after SARS-CoV-2 infection. Purpose To characterize both morphologic and functional changes of lung parenchyma on low-field MRI in children and adolescents with post COVID-19 compared with healthy controls. Materials and Methods Between August and December 2021, a cross-sectional, prospective clinical trial using low-field MRI was performed in children and adolescents from a single academic medical center. The primary outcome was the frequency of morphologic changes on MRI. Secondary outcomes included MRI-derived functional proton ventilation and perfusion parameters. Clinical symptoms, the duration from positive RT-PCR test and serological parameters were compared with imaging results. Nonparametric tests for pairwise and corrected tests for groupwise comparisons were applied to assess differences in healthy controls, recovered participants and with long COVID. Results A total of 54 participants post COVID-19 infection (mean age, 11 years ±3 [SD], 56 males) and 9 healthy controls (mean age, 10 years ±3 [SD], 70 males) were included: 29 (54%) in the COVID-19 group had recovered from infection and 25 (46%) were classified as having long COVID on the day of enrollment. Morphologic abnormality was identified in one recovered participant. Both ventilated and perfused lung parenchyma (V/Q match) was reduced from 81±6.1% in healthy controls to 62±19% (

Background Brain injury and subsequent neurodevelopmental disorders are major determinants for later-life outcomes in neonates with transposition of the great arteries (TGA). Purpose To quantitatively assess cerebral perfusion in neonates with TGA undergoing arterial switch operation (ASO) using transfontanellar contrast-enhanced US (T-CEUS). Materials and Methods In a prospective single-center cross-sectional diagnostic study, neonates with TGA scheduled for ASO were recruited from February 2018 to February 2020. Measurements were performed at five time points before, during, and after surgery (T

Objectives The assessment of SARS-CoV-2 infections in children is still challenging, but essential for appropriate political decisions. The aim of this study was to investigate whether residual blood samples can be used for SARS-CoV-2 seroprevalence monitoring in pediatrics. Methods In this repeated cross-sectional cohort study, anonymous residual blood samples from pediatric patients aged 0–17 years were collected in three time-periods (Oct.–Nov. 2020, April 2021, and June–July 2021) and analyzed for SARS-CoV-2 Spike protein (anti-S) and nucleocapsid (anti-N) antibodies using commercial antibody assays. 28 reactive samples were used to compare antibody levels with a pseudotyped neutralization assay. The results were further compared to the official national COVID-19 surveillance data to calculate the number of unreported cases. Results In total, n=2,626 individual blood samples were analyzed. In this unvaccinated pediatric cohort anti-S and anti-N antibody seroprevalence increased over the three time periods (anti-S: 1.38–9.16%, and 14.59%; anti-N: 1.26%, to 6.19%, and 8.56%). Compared to the national surveillance data this leads to a 3.93–5.66-fold increase in the number of unreported cases. However, a correlation between the cumulative incidence of the individual provinces and our assigned data was found (r=0.74, p=0.0151). In addition, reactive samples with anti-S and anti-N and samples with only anti-S showed neutralization capabilities (11/14 and 8/14, respectively). Anti-S levels were not significantly different between age groups and sexes (all p>0.05). Conclusions The present study suggests that residual blood samples from routine laboratory chemistry could be included in the estimation of the total SARS-CoV-2 seroprevalence in children.

Buried bumper syndrome (BBS) is a severe complication of percutaneous endoscopic gastrostomy (PEG) resulting from overgrowth of gastric mucosa and penetration of the inner holding plate into the gastric wall. The aim of this study was to evaluate the diagnostic value of transabdominal ultrasound (US) in comparison to an artificial intelligence (AI) model for the diagnosis of BBS in children. In this monocentric retrospective study, pediatric US data concerning BBS from a ten-year period (2009-2019) were analyzed. US findings were compared to a clinical multiparameter-based AI model and reference standard endoscopy. Clinical risk factors for the occurrence of pediatric BBS were determined. In n = 121 independent examinations of n = 82 patients, the placement of the inner holding plate of the PEG was assessed by US. In n = 18 cases BBS was confirmed. Recall and precision rates were 100 % for US and 88 % for the AI-based assessment. Risk factors for the occurrence of BBS were mobilization problems of the PEG (r Transabdominal US enables correct, rapid, and noninvasive diagnosis of BBS in pediatric patients. Preceding AI models could aid during diagnostic workup. To avoid unnecessary invasive procedures, US could be considered as a primary diagnostic procedure in suspected BBS. .ZIEL: Das Buried-Bumper-Syndrom (BBS) ist eine schwerwiegende Komplikation der perkutanen endoskopischen Gastrostomie (PEG) und beschreibt eine Schleimhautüberwucherung der inneren PEG-Halteplatte. Ziel dieser Studie war es, die Wertigkeit des transabdominalen Ultraschalls (US) mit einem Modell der künstlichen Intelligenz (KI) zur Diagnose eines BBS zu vergleichen. In dieser monozentrischen retrospektiven Studie wurden US-Daten mit Bezug zu BBS aus einem Jahrzehnt (2009–2019) untersucht. Die US-Ergebnisse wurden mit der Endoskopie und mit einem eigens entwickelten KI-Modell verglichen. Darüber hinaus wurden Risikofaktoren für das Auftreten von BBS bewertet. Die Position der inneren PEG-Halteplatte wurde bei n = 82 pädiatrischen Patienten in n = 121 unabhängigen US-Untersuchungen bewertet. Alle n = 18 Fälle mit BBS wurden mittels US korrekt diagnostiziert (Sensitivität/positiver Prädiktionswert von 100 %). Das KI-basierte Modell zeigte eine Sensitivität/einen positiven Prädiktionswert von 88 %. Risikofaktoren für das Auftreten eines BBS waren Mobilisierungsprobleme der PEG (r Transabdominaler US ermöglicht die korrekte, schnelle und nichtinvasive Diagnosestellung eines BBS bei Kindern. Vorangehende KI-Modelle könnten die diagnostische Abklärung unterstützen. Bei Verdacht auf ein BBS sollte primär ein US eingesetzt werden, um unnötige invasive Eingriffe zu vermeiden.

Ultrasonography is the primary imaging modality in pediatrics but still lacks sufficient reimbursement in Germany. In this multicenter study, national data for the duration of standard ultrasound in pediatrics were systematically documented in order to specify the actual time required. N = 10 hospitals (N = 5 university hospitals, N = 5 non-university hospitals) and N = 3 medical practices in Germany recorded the entire process of an ultrasound examination in a special protocol developed by the Pediatric Section of the DEGUM. The duration of each of seven single steps during ultrasonography (from data input to final discussion of the results) of different organ systems was logged. In total, N = 2118 examinations from different organ systems were recorded. N = 10 organ systems were examined frequently ( 30 times). The total duration of an ultrasound examination was statistically significantly longer in hospitals compared to medical practices (median (IQR) 27 min. (18-38) vs. 12 min. (9-17), p 0.001). The "hands-on" patient time was approximately one half of the total required time in both settings (49.9 % vs. 48.9 %). Ultrasonography of the abdomen and brain lasted longer in university hospitals than in non-university hospitals (p 0.001, and p = 0.04, respectively). Cooperation and age did not uniformly correlate with the total duration. This study provides novel comprehensive national data for the duration of standardized ultrasound examinations of children and adolescents in Germany. These data are essential for a further evaluation of the economic costs and should support better remuneration in the future. Die Sonografie ist die primäre bildgebende Diagnostik in der Pädiatrie, wird in Deutschland jedoch unzureichend vergütet. Ziel dieser multizentrischen und systematischen Erhebung von Ultraschalluntersuchungszeiten in der Pädiatrie ist die erstmalige Analyse des tatsächlichen Zeitbedarfs. N = 10 Kliniken (n = 5 Universitätskliniken, n = 5 kommunale Kliniken) und n = 3 Praxen aus Deutschland erfassten die Gesamtheit einer Ultraschalluntersuchung in einem eigens hierfür entwickelten Fragebogen der pädiatrischen Sektion der Deutschen Gesellschaft für Ultraschall in der Medizin (DEGUM). Es wurde der genaue Zeitaufwand für sieben definierte Untersuchungsschritte (von Dateneingabe bis Befundbesprechung) für verschiedene Organsysteme protokolliert. Bei insgesamt n = 2118 Kindern wurde eine Ultraschalluntersuchung eines Organsystems durchgeführt. N = 10 Organsysteme wurden häufiger als 30-mal untersucht. Die Untersuchungszeiten in Krankenhäusern waren mehr als doppelt so lange wie in der pädiatrischen Praxis (median (IQR) 27 min (18–38) vs. 12 min (9–17); p 0,001). Die „Hands on“-Zeit am Patienten nahm jeweils fast die Hälfte der Gesamtdauer der Untersuchung in Anspruch (49,9 % vs. 48,9 %). Die Abdomen- und ZNS-Sonografie dauerte an Universitätskliniken länger als an kommunalen Kliniken (p 0,001 und p = 0,04). Kooperation und Alter des Kindes hatten keinen einheitlichen Einfluss auf die Untersuchungszeiten. Diese Studie zeigt erstmals dezidierte Daten zum zeitlichen Aufwand von Ultraschalluntersuchungen von Kindern und Jugendlichen in Deutschland. Die erhobenen Daten sind für eine reale Bewertung des Aufwands und der volkswirtschaftlichen Kosten der pädiatrischen Sonografie von elementarer Bedeutung und können in Zukunft als Grundlage für eine entsprechende Vergütung der erbrachten Leistungen dienen.

ObjectiveTo compare the effects of interleukin-6 (IL-6) receptor and tumour necrosis factor inhibition on inducing repair of existing bone erosions in patients with very early rheumatoid arthritis (RA).MethodsProspective non-randomised observational study in patients with active erosive RA with inadequate response to methotrexate (MTX) receiving either tocilizumab (TOC) monotherapy or adalimumab (ADA) with MTX for 52 weeks. Erosion volumes were assessed in metacarpal heads (MCH) and the radius by high-resolution peripheral quantitative CT at baseline and after 52 weeks. Clinical response was monitored using Clinical Disease Activity Index, Simple Disease Activity Index and Disease Activity Score 28-erythrocyte sedimentation rate (DAS28-ESR) scores every 12 weeks.ResultsTOC (N=33) and ADA/MTX (N=33) treatment groups were balanced for age, sex, body mass index, comorbidities, disease and activity, functional state, autoantibody status, baseline bone damage and baseline bone biomarkers. Both TOC (DAS28-ESR: baseline: 6.2±0.5; 52 weeks: 2.3±1.0) and ADA/MTX (6.3±0.6; 2.8±1.2) significantly reduced disease activity. Erosion volumes significantly decreased in the MCH and radius of patients with RA treated with TOC (p3 and −3.3±5.9 mm3 in the MCH and radius of TOC-treated patients, respectively, and −0.05±0.9 mm3 and −0.08±4.1 mm3 in patients treated with ADA/MTX.ConclusionsThe REBONE study shows that TOC monotherapy achieves more pronounced repair of existing bone erosions than ADA/MTX. Hence, IL-6 is a central factor for the disturbed bone homeostasis in the joints of patients with RA.

Proximal spinal muscular atrophy (SMA) is a rare progressive, life limiting genetic motor neuron disease. While promising causal therapies are available, meaningful prognostic biomarkers for therapeutic monitoring are missing. We demonstrate handheld Multispectral Optoacoustic Tomography (MSOT) as a novel non-invasive imaging approach to visualize and quantify muscle wasting in pediatric SMA. While MSOT signals were distributed homogeneously in muscles of healthy volunteers (HVs), SMA patients showed moth-eaten optoacoustic signal patterns. Further signal quantification revealed greatest differences between groups at the isosbestic point for hemoglobin (SWL 800 nm). The SWL 800 nm signal intensities further correlated with clinical phenotype tested by standard motor outcome measures. Therefore, handheld MSOT could enable non-invasive assessment of disease burden in SMA patients.

OBJECTIVES Aortic coarctation with distal aortic arch hypoplasia can be effectively addressed by coarctation resection with extended end-to-end-anastomosis (REEEA). Particularly, when unilateral cerebral perfusion (UCP) is established by clamping of left-sided supra-aortic vessels, the extent of cerebral blood flow distribution during repair remains undetermined, so far. Transfontanellar contrast-enhanced ultrasound (T-CEUS) can be utilized for real-time visualization and quantitative evaluation of cerebral blood flow. This study quantitatively evaluates cerebral perfusion during REEEA by using intraoperative T-CEUS. METHODS In a prospective study, 9 infants with open fontanelle undergoing REEEA [median age: 13 days (range 1–34) and median weight 3.1 kg (range 2.2–4.4)] were intraoperatively examined with T-CEUS at 3 consecutive time-points: before skin incision, during UCP and after skin suture. A software-based analysis of 11 parameters was used for data evaluation. Absolute and relative blood flow in contralateral hemispheres was measured in side-by-side comparison, and referenced to baseline measurements. RESULTS No side-depend absolute or relative cerebral perfusion differences were found during REEEA, except for an increased relative ‘wash-out-rate’ (P = 0.0013) in favour of the right hemisphere after surgery. Compared to ipsilateral baseline levels, ‘rise time’ was transiently increased in right (P = 0.0277) and ‘time-to-peak’ in both hemispheres (right: P = 0.0403 and left: P = 0.0286), all during UCP. CONCLUSIONS The use of T-CEUS provided evidence for homogenous distribution of contrast agent in both hemispheres during UCP. T-CEUS can be utilized for the postprocedural evaluation of cerebral perfusion during congenital cardiac surgery. Clinical Trial Registration URL: http://www.clinicaltrials.gov Unique, Identifier: NCT03215628.

Graphical abstract, Photo-or optoacoustic imaging (OAI) allows quantitative imaging of target tissues. Using multi-wavelength illumination with subsequent ultrasound detection, it may visualize a variety of different chromophores at centimeter depth. Despite its non-invasive, label-free advantages, the precision of repeated measurements for clinical applications is still elusive. We present a multilayer analysis of n = 1920 imaging datasets obtained from a prospective clinical trial (NCT03979157) in n = 10 healthy adult volunteers. All datasets were analyzed for 13 single wavelengths (SWL) between 660 nm–1210 nm and five MSOT-parameters (deoxygenated/oxygenated/total hemoglobin, collagen and lipid) by a semi-automated batch mode software. Intraclass correlation coefficients (ICC) were good to excellent for intrarater (SWL: 0.82–0.92; MSOT-parameter: 0.72−0.92) and interrater reproducibility (SWL: 0.79−0.87; MSOT-parameter: 0.78−0.86), with the exception for MSOT-parameter lipid (interrater ICC: 0.56). Results were stable over time, but exercise-related effects as well as inter-and intramuscular variability were observed. The findings of this study provide a framework for further clinical OAI implementation.

Optoacoustic imaging (OAI), or photoacoustic imaging (PAI), has fundamentally influenced basic science by providing high-resolution visualization of biological mechanisms. With the introduction of multispectral optoacoustic tomography (MSOT), these technologies have now moved closer to clinical applications. MSOT utilizes short-pulsed near-infrared laser light to induce thermoelastic expansion in targeted tissues. This results in acoustic pressure waves, which are used to resolve specific endo- and exogenous chromophores. Especially in the pediatric population, this non-invasive imaging approach might hold fundamental advantages compared to conventional cross-sectional imaging modalities. As this technology allows the visualization of quantitative molecular tissue composition at high spatial resolution non-invasively in sufficient penetration depth, it paves the way to personalized medicine in pediatric diseases.

German pediatric guidelines for severe traumatic brain injury (TBI) management expired in 2011. Thus, divergent evidence-based institutional protocols are predominantly being followed. We performed a survey of current Pediatric Intensive Care Unit (PICU) management of isolated severe TBI in Germany to reveal potential varying practices. Seventy German PICUs were invited to join an anonymous online survey from February to May 2017. Twenty-nine participants (41.4%) successfully completed the survey (17 university hospitals and 12 district hospitals). The majority of items were polar (yes/no) or scaled (e.g., never - always). Main topics were imaging, neurosurgery, neuromonitoring, adjuvant therapy, and medication. Severity of TBI was defined via Glasgow Coma Scale. The majority of respondents (93.1%) had internal TBI standards, and patients were mainly administered to interdisciplinary trauma units. The use of advanced neuromonitoring techniques, intracranial hypertension management, and drug treatment differed between PICUs. Routine administration of hypertonic saline in TBI-associated cerebral edema was performed by 3.4%, while it was never an option for 31.0% of the participants. Prophylactic anticonvulsive therapy was restrictively performed. If indicated, the main anticonvulsive drugs used were phenobarbital and levetiracetam. Neuroendocrine follow-up was recommended/performed by 58.6% of the PICUs. This survey provides an overview of the current PICU practices of isolated severe TBI management in Germany and demonstrates a wide instrumental and therapeutical range, revealing an unmet need for the revised national guideline and further (international) clinical trials for the treatment of severe TBI in pediatrics.

Optoacoustic or photoacoustic imaging (OAI/PAI) is a technology which enables non-invasive visualization of laser-illuminated tissue by the detection of acoustic signals. The combination of “light in” and “sound out” offers unprecedented scalability with a high penetration depth and resolution. The wide range of biomedical applications makes this technology a versatile tool for preclinical and clinical research. Particularly when imaging inflammation, the technology offers advantages over current clinical methods to diagnose, stage, and monitor physiological and pathophysiological processes. This review discusses the clinical perspective of using OAI in the context of imaging inflammation as well as in current and emerging translational applications.

Rationale: To develop a simple and fast protocol for the assessment of acute and chronic experimental intestinal inflammation using contrast-enhanced µCT. Methods: For the imaging studies, an acute 2% and 3% dextran sodium sulfate (n = 15, female, 8-12 weeks) and a chronic adoptive transfer colitis model (n = 10, female, 8-9 weeks) were established over 9 days or 6 weeks, respectively. Throughout the experiments, longitudinal measurement of murine intestinal wall thickness and time dependent perfusion was performed on a small animal µCT system (90 kV, 160 μA, FOV: 60 mm, scan time: 17 s, image size: 512x512, layer thickness: 118 µm) between 0.5 and 30 min after intravenous bolus injection of an iodine contrast agent. Weight development, small animal endoscopy, and histological ex vivo analysis were compared to contrast-enhanced µCT imaging findings. Results: Murine intestinal wall thickness was significantly increased in inflamed colons of acute colitis at day 9 in comparison to pre-inflamed state. Perfusion analysis revealed a late contrast enhancement in acute inflamed colons and the renal medulla at day 9 compared to control mice. An increasing intestinal wall thickness was monitored 3, 5 and 6 weeks after on-set of chronic colitis in comparison to controls. A good correlation with endoscopic (r = 0.75, p < 0.0001) and histologic degree of inflammation (r = 0.83, p = 0.04) was found. Conclusion: Contrast-enhanced µCT is a simple and fast method to assess acute intestinal inflammation and to monitor disease progression in experimental models of chronic colitis. According to our findings, one single contrast-enhanced µCT-scan is a valid non-invasive modality to quantify the degree of inflammation in the entire digestive tract in murine inflammatory models.

OBJECTIVES To investigate whether MRI allows the detection of osteosclerosis as a sign of repair of bone erosions compared with high-resolution peripheral quantitative computed tomography (HR-pQCT) as a reference and whether the presence of osteosclerosis on HR-pQCT is linked to synovitis and osteitis on MRI. METHODS A total of 103 RA patients underwent HR-pQCT and MRI of the dominant hand. The presence and size of erosions and the presence and extent (grades 0-2) of osteosclerosis were assessed by both imaging modalities, focusing on MCP 2 and 3 and wrist joints. By MRI, the presence and grading of osteitis and synovitis were assessed according to the Rheumatoid Arthritis MRI Score (RAMRIS). RESULTS Parallel evaluation was feasible by both modalities on 126 bone erosions. Signs of osteosclerosis were found on 87 erosions by HR-pQCT and on 22 by MRI. False-positive results (MRI(+)CT(-)) accounted for 3%, while false-negative results (MRI(-)CT(+)) accounted for 76%. MRI sensitivity for the detection of osteosclerosis was 24% and specificity was 97%. The semi-quantitative scoring of osteosclerosis was reliable between MRI and HR-pQCT [intraclass correlation coefficient 0.917 (95% CI 0.884, 0.941), P < 0.001]. The presence of osteosclerosis on HR-pQCT showed a trend towards an inverse relationship to the occurrence and extent of osteitis on MRI [χ(2)(1) = 3.285; ϕ coefficient = -0.124; P = 0.070] but not to synovitis [χ(2)(1) = 0.039; ϕ coefficient = -0.14; P = 0.844]. CONCLUSION MRI can only rarely detect osteosclerosis associated with bone erosions in RA. Indeed, the sensitivity compared with HR-pQCT is limited, while the specificity is high. The presence of osteitis makes osteosclerosis more unlikely, whereas the presence of synovitis is not related to osteosclerosis.

Background The detection of bone erosions is fundamental both for monitoring of disease activity and therapy decisions in rheumatoid arthritis (RA). Recently, it could be shown by high-resolution peripheral quantitative computed tomography (HR-pQCT) that erosion repair is associated with bone apposition at the bottom of the erosion (“sclerosis”) [1;2]. MRI however is more widely available in clinical settings and used as a monitoring tool of disease activity in RA. Objectives To investigate whether MRI allows visualization of sclerosis at the bottom of erosive lesions in comparison to HR-pQCT as a reference. Methods 53 RA patients fulfilling the new ACR/EULAR criteria received a 1.5T MRI (Siemens, Vario) and an HR-pQCT (Scanco Medical AG, XtremeCT) of the metacarpophalangeal joints 2 and 3 of the clinically dominant hand. Prevalence of erosions as well as sclerosis was assessed in both imaging modalities in the coronal plane. All MRI- and CT-images were evaluated twice by two readers in a blinded fashion. Demographic and clinical data were collected for each patient. Results 69.8% of patients were females, mean ±SD age was 53.15±15.90 years; mean disease duration ±SD was 34.9±64.5 months, and mean DAS28±SD was 3.61±1.81. Prevalence of RF and ACPA was 52.8% and 58.5% respectively. A mean number of 66.5 erosions were detected by MRI per reading as compared to 81.5 erosions per reading by HR-pQCT (4 readings, 2 readers for each modality). The average proportion of correctly classified non sclerosed lesions in the MRI compared to HR-pQCT was 94% (specificity), while the average proportion of correctly classified sclerosed lesions was 31% (sensitivity). Hence, our results show a good concordance of the two imaging modalities for absence of sclerosis, but poor agreement for presence of sclerosis. On average, the observation of a “non sclerosed lesion” in the MRI was correct in 80.5% of cases after validation by HR-pQCT (negative predictive value-NPV), whereas it was 62% for “sclerosed lesions” in the MRI (positive predictive value-PPV). Conclusions According to our results, MRI has limitations to detect repair of bone lesions in RA. References Finzel S, Rech J, Schmidt S, et al. Ann Rheum Dis. 2011 Sep;70(9):1587-93. Finzel S, Rech J, Schmidt S, et al. Ann Rheum Dis. 2012 May 14. [Epub ahead of print] Disclosure of Interest None Declared

Biomarkers for monitoring of disease progression and response to therapy are lacking for muscle diseases such as Duchenne muscular dystrophy. Noninvasive in vivo molecular imaging with multispectral optoacoustic tomography (MSOT) uses pulsed laser light to induce acoustic pressure waves, enabling the visualization of endogenous chromophores. Here we describe an application of MSOT, in which illumination in the near- and extended near-infrared ranges from 680–1,100 nm enables the visualization and quantification of collagen content. We first demonstrated the feasibility of this approach to noninvasive quantification of tissue fibrosis in longitudinal studies in a large-animal Duchenne muscular dystrophy model in pigs, and then applied this approach to pediatric patients. MSOT-derived collagen content measurements in skeletal muscle were highly correlated to the functional status of the patients and provided additional information on molecular features as compared to magnetic resonance imaging. This study highlights the potential of MSOT imaging as a noninvasive, age-independent biomarker for the implementation and monitoring of newly developed therapies in muscular diseases. Imaging of muscle fibrosis with a handheld device could potentially serve as a biomarker for disease progression and response to therapy in patients with Duchenne muscular dystrophy.

Objective To explore the metabolic characteristics of arthritis and enthesitis using multispectral opto-acoustic tomography (MSOT), a technology using near-infrared multispectral laser to stimulate tissues and detect the emitted acoustic energy, enabling non-invasive quantification of tissue components in vivo based on differential absorbance at multiple wavelengths. Methods We performed a cross-sectional study in patients with RA or PsA and healthy controls (HCs). Participants underwent clinical, ultrasonographic and MSOT examination of MCP and wrist joints as well as the entheses of the common extensor tendon at the lateral humeral epicondyles and of the patellar, quadriceps and Achilles tendon. MSOT-measured haemoglobin (Hb), oxygen saturation, collagen and lipid levels were quantified and scaled mean differences between affected and unaffected joints and entheses were calculated as defined by clinical examination or ultrasonography using linear mixed effects models. Results We obtained 1535 MSOT and 982 ultrasonography scans from 87 participants (34 PsA, 17 RA, 36 HCs). Entheseal tenderness was not associated with significant metabolic changes, whereas enthesitis-related sonographic changes were associated with increased total Hb, oxygen saturation and collagen content. In contrast, the presence of arthritis-related clinical and sonographic findings showed increased Hb levels, reduced oxygen saturation and reduced collagen content. Synovial hypertrophy was associated with increased lipid content in the joints. Conclusion MSOT allows determination of distinct metabolic differences between arthritis and enthesitis in a non-invasive setting in humans in vivo.