Microwave Radiometry for the Diagnosis and Monitoring of Inflammatory Arthritis

The ability of microwave radiometry (MWR) to detect with high accuracy in-depth temperature changes in human tissues is under investigation in various medical fields. The need for non-invasive, easily accessible imaging biomarkers for the diagnosis and monitoring of inflammatory arthritis provides the background for this application in order to detect the local temperature increase due to the inflammatory process by placing the appropriate MWR sensor on the skin over the joint. Indeed, a number of studies reviewed herein have reported interesting results, suggesting that MWR is useful for the differential diagnosis of arthritis as well as for the assessment of clinical and subclinical inflammation at the individual large or small joint level and the patient level. MWR showed higher agreement with musculoskeletal ultrasound, used as a reference, than with clinical examination in rheumatoid arthritis (RA), while it also appeared useful for the assessment of back pain and sacroiliitis. Further studies with a larger number of patients are warranted to confirm these findings, taking into account the current limitations of the available MWR devices. This may lead to the production of easily accessible and inexpensive MWR devices that will provide a powerful impetus for personalized medicine.

Joint microwave radiometry for inflammatory arthritis assessment

OBJECTIVES

Increased in-depth joint temperature measured by the rapid, easy-to-perform microwave radiometry (MWR) method may reflect inflammation, even in the absence of clinical signs. We hypothesized that MWR is useful for RA and spondyloarthritis patients' assessment.

METHODS

Clinical examination, joint ultrasound and/or MRI and MWR were performed in two independent patient-control cohorts (n = 243).

RESULTS

Among single RA joints MWR performed best in the knee using ultrasound as reference, with 75% sensitivity-73% specificity for grey-scale synovitis score ⩾2, and 80% sensitivity-82% specificity for power Doppler positivity. A stronger agreement was evident between increased knee relative temperature (Δt) and power Doppler positivity (82%) than with clinical examination (76%). In a different patient cohort with painful knees, a knee Δt ⩽0.2 predicted power Doppler positivity with 100% positive and negative predictive values. A thermo-score summing 10 Δt values of three large and seven small RA joints (elbow, knee, ankle, wrist, four hand and two foot joints of the clinically dominant arm or hand and leg or foot) correlated with ultrasound scores of synovitis/tenosynovitis (all P < 0.001) and the 28-joint Disease Activity Score (DAS28) (P = 0.004). The agreement of the thermo-score with ultrasound-defined joint inflammation (82%) was stronger than with DAS28 (64%). The thermo-score improved significantly after 90 days of treatment in patients with active RA at baseline (P = 0.004). Using MRI as reference, Δt of sacroiliac joints could discriminate between spondyloarthritis patients with or without sacroiliitis with 78% sensitivity-74% specificity.

CONCLUSION

In-depth increased MWR-derived joint temperature reflects both subclinical and clinically overt inflammation and may serve as a biomarker in arthritis.

P3716Increased two-year cerebrovascular event rate in patients with bilateral high carotid tempratures

Introduction

The association of carotid plaque inflammation with cerebrovascular events is a matter of rigorous research. Microwave Radiometry (MWR) allows in vivo noninvasive measurement of the internal temperatures of tissues, reflecting inflammation.

Purpose

To investigate whether increased carotid temperatures in patients with documented coronary artery disease (CAD) are associated with cerebrovascular events.

Methods

Consecutive patients with significant CAD from three tertiary centers were included in the study. Maximum carotid plaque thickness was assessed in all carotids by ultrasound. ΔT by MWR was assigned as the temperature difference (maximal minus minimum) along the carotid artery. ΔT ≥0.90°C was assigned as high ΔT. All patients were followed-up clinically for two years and all strokes were adjudicated by an independent committee. Transient ischemic attacks were excluded.

Results

In total 300 patients were included in the study. High ΔT temperatures bilaterally were measured in 47 patients (15.7%). Three patients (1.0%) suffered a stroke, including one fatal. Stoke rate was 4.3% in the group with bilateral high ΔT and 0.4% in non-high ΔT group (p=0.02). In Kaplan-Meier plot patients with bilateral high ΔT showed higher stroke rate (log-rank p=0.004, figure)

Conclusions

Bilateral high carotid temperatures are associated with increased two-year stroke rate. The potential value of the present finding in risk stratification of intermediate carotid stenosis mandates further investigation.

Multi-center feasibility study of microwave radiometry thermometry for non-invasive differential diagnosis of arterial disease in diabetic patients with suspected critical limb ischemia

AIMS

Diagnosis of vascular involvement in diabetic foot ulceration (DFU) remains challenging. We conducted a proof of concept study to investigate the feasibility of microwave radiometry (MWR) thermometry for non-invasive differential diagnosis of critical limb ischemia (CLI) in subjects with DFU.

METHODS

This prospective, multi-center, study included 80 participants, divided into four groups (group N: normal control subjects; group DN: participants with diabetes and verified neuropathic ulcers without vascular involvement; group DC: participants with diabetes and CLI and group NDC: participants with CLI without diabetes). Vascular disease was confirmed with angiography. All patients underwent MWR (RTM-01-RES:University of Bolton, UK) to record mean tissue temperatures at various pre-determined foot sites. Comparisons of temperature measurements between study groups were performed using one-way ANOVA and Dunn tests. ROC analysis was performed to determine sensitivity, specificity and cut-off value of MWR for CLI diagnosis.

RESULTS

Temperatures recorded in vicinity to the foot ulcers of participants with diabetes and CLI were similar to those with CLI without diabetes, but significantly lower than in subjects with neuropathic ulcers without vascular involvement and normal controls (group DC:29.30°C±1.89 vs. group NDC:29.18°C±1.78vs. group N:33.01°C±0.45 vs. group DN:33.39°C±1.37;P<.0001). According to ROC analysis, cut-off temperature value to diagnose CLI was <31.8°C (area under the curve: 0.984; 95% CI: 0.965-1.005;P<.001), with a sensitivity of 100.0% (95%CI: 90.26-100.0) and specificity of 88.37% (95% CI: 74.92-96.11).

CONCLUSIONS

Tissue temperatures in vicinity to ulcers were significantly lower in participants with CLI, with or without diabetes, compared to non-ischemic controls. MWR could be used for differential diagnosis of arterial ischemia in subjects with DFU.

Noninvasive detection of increased carotid artery temperature in patients with coronary artery disease predicts major cardiovascular events at one year: Results from a prospective multicenter study

BACKGROUND AND AIMS

Limited prospective data have been reported regarding the impact of carotid inflammation on cardiovascular events in patients with coronary artery disease (CAD). Microwave radiometry (MWR) is a noninvasive, simple method that has been used for evaluation of carotid artery temperature which, when increased, predicts 'inflamed' plaques with vulnerable characteristics. We prospectively tested the hypothesis that increased carotid artery temperature predicts future cerebro- and cardiovascular events in patients with CAD.

METHODS

Consecutive patients from 3 centers, with documented CAD by coronary angiography, were studied. In both carotid arteries, common carotid intima-media thickness and plaque thickness were evaluated by ultrasound. Temperature difference (ΔT), measured by MWR, was considered as the maximal temperature along the carotid artery minus the minimum; ΔT ≥0.90 °C was assigned as high. Major cardiovascular events (MACE, death, stroke, myocardial infarction or revascularization) were recorded during the following year.

RESULTS

In total, 250 patients were studied; of them 40 patients (16%) had high ΔT values in both carotid arteries. MACEs occurred in 30% of patients having bilateral high ΔT versus 3.8% in the remaining patients (p<0.001). Bilateral high ΔT was independently associated with increased one-year MACE rate (HR = 6.32, 95% CI 2.42-16.53, p<0.001, by multivariate cox regression hazard model). The addition of ΔT information on a baseline model based on cardiovascular risk factors and extent of CAD significantly increased the prognostic value of the model (c-statistic increase 0.744 to 0.845, p_dif = 0.05) CONCLUSIONS: Carotid inflammation, detected by MWR, has an incremental prognostic value in patients with documented CAD.

Electromagnetic wave absorption properties of ternary poly(vinylidene fluoride)/magnetite nanocomposites with carbon nanotubes and graphene

Ternary nanocomposite systems of PVDF/Fe₃O₄/CNT and PVDF/Fe₃O₄/GN, prepared with twin screw compounding method, exhibit enhanced microwave absorption properties.

Effect of Addition of Multiwalled Carbon Nanotubes on the Piezoelectric Properties of Polypropylene Filaments

The effect of addition of multiwalled carbon nanotubes (CNTs) on the piezoelectric properties of polypropylene (PP) monofilaments has been investigated. Various amounts of CNTs (0%, 0.01%, 0.1% and 1% weight ratios) were melt-blended with PP and the resulting nanocomposites were extruded in a continuous process with simultaneous on-line poling to produce monofilaments. Concurrent stretching at a draw ratio of 5:1 and polarisation at applied electric fields of 15 kV of PP/CNT filaments was observed to enhance the piezoelectric properties. The microstructure and crystallinity of the filaments was analysed using scanning electron microscopy (SEM), differential scanning calorimetric (DSC) and Fourier transform infrared spectroscopy (FTIR) techniques. Voltage generation by the CNT-modified PP filaments was determined by the application of predetermined load impact. The results show that the incorporation of CNTs in the PP fibre structure has a considerable impact on the enhancement of piezoelectric properties of the PP filament obtained that the peak voltage generation was almost four fold (from 0.76 V to 2.92 V) when 0.1 wt% of CNTs added into the polymer. This is owing to the fact that carbon nanotubes act as nucleating agent for enhancing the crystallisation during the melt extrusion process.

Exclusive self-aligned β-phase PVDF films with abnormal piezoelectric coefficient prepared via phase inversion

Self-polarised poly(vinylidene fluoride), (PVDF), films were prepared via a facile phase-inversion technique wherein the polymorphism of the films was controlled from exclusive α- (>90%) to β-phase (>98%) by simply varying the quenching temperature from 100 °C to -20 °C, respectively. At low temperatures, the β-phase crystallites were found to be self-aligned, with the PVDF thin films possessing a high piezoelectric coefficient of up to -49.6 pm V(-1). The extraordinarily high β-phase and piezoelectric coefficient of these PVDF films make them suitable for electroactive and energy harvesting applications.

Low-Pressure H2, NH3 Microwave Plasma Treatment of Polytetrafluoroethylene (PTFE) Powders: Chemical, Thermal and Wettability Analysis

Functionalization of Polytetrafluoroethylene (PTFE) powders of ~6 μm particle size is carried out using low-pressure 2.45 GHz H₂, NH₃ microwave plasmas for various durations (2.5, 10 h) to chemically modify their surface and alter their surface energy. The X-ray Photoelectron Spectroscopy (XPS) analyses reveal that plasma treatment leads to significant defluorination (F/C atomic ratio of 1.13 and 1.30 for 10 h NH₃ and H₂ plasma treatments, respectively vs. 1.86 for pristine PTFE), along with the incorporation of functional polar moieties on the surface, resulting in enhanced wettability. Analysis of temperature dependent XPS revealed a loss of surface moieties above 200 °C, however, the functional groups are not completely removable even at higher temperatures (>300 °C), thus enabling the use of plasma treated PTFE powders as potential tribological fillers in high temperature engineering polymers. Ageing studies carried over a period of 12 months revealed that while the surface changes degenerate over time, again, they are not completely reversible. These functionalised PTFE powders can be further used for applications into smart, high performance materials such as tribological fillers for engineering polymers and bio-medical, bio-material applications.

Bilateral symmetry of local inflammatory activation in human carotid atherosclerotic plaques

INTRODUCTION

Only a few studies have investigated the structural and functional characteristics of carotid arteries bilaterally. Furthermore, there is controversy as to whether inflammation in paired vascular beds is a local or systemic phenomenon. We aimed to examine, in patients with coronary artery disease, whether intra-subject left and right carotid arteries have similar inflammatory status, as determined non-invasively by microwave radiometry (MWR).

METHODS

Consecutive patients (n=200) with significant coronary artery disease were evaluated via an ultrasound echo-colour Doppler (US-ECD) study of both carotid arteries and temperature measurements with MWR. During thermography, thermal heterogeneity (ΔT) was defined as the maximum temperature along the carotid artery minus the minimum temperature.

RESULTS

Mean T was similar between the left and right carotid arteries (0.78 ± 0.48 vs. 0.84 ± 0.52°C, p=0.12). Mean right intima-media thickness (IMT) was greater compared to mean left IMT (2.16 ± 1.20 vs. 1.93 ± 0.94 mm, p<0.01). In all carotids, there was a correlation between left and right carotid plaque ΔT (R=0.38, p<0.001) and between left and right IMT (R=0.48, p<0.001). Independent predictors for the presence of bilateral carotid plaques were found to be the extent of coronary artery disease, high ΔT, and therapy with angiotensin II receptor blockers; predictors for the presence of high ΔT bilaterally were bilateral carotid plaques, male sex, diabetes mellitus, and hypertension.

CONCLUSIONS

There is bilateral inflammatory activation in the carotid atherosclerotic lesions of patients with coronary artery disease. At this stage of carotid disease, arterial hypertension and diabetes mellitus are more strongly correlated with bilateral functional abnormalities in carotid plaques than with structural changes.

Incremental Predictive Value of Carotid Inflammation in Acute Ischemic Stroke

Background and Purpose—

Microwave Radiometry (MWR) allows in vivo noninvasive assessment of internal temperature of tissues. The aim of the present study was to evaluate in patients with ischemic stroke and bilateral carotid plaques (1) whether ipsilateral carotid arteries exhibit higher temperature differences (Δ T ), as assessed by MWR; (2) the predictive accuracy of MWR in symptomatic carotid artery identification.

Methods—

Consecutive patients with recent acute anterior circulation ischemic stroke because of large artery atherosclerosis were included in the study. Carotid arteries of all patients were evaluated by carotid ultrasound and MWR.

Results—

In total, 50 patients were included in the study. Culprit carotid arteries had higher Δ T compared with nonculprit (0.93±0.58 versus 0.58±0.35°C; P <0.001). The addition of Δ T to a risk prediction model based only on ultrasound plaque characteristics increased its predictive accuracy significantly (c-statistic: 0.691 versus 0.768; P dif =0.05).

Conclusions—

Culprit carotid arteries show higher thermal heterogeneity compared with nonculprit carotid arteries in patients with acute ischemic stroke and bilateral carotid plaques. MWR has incremental value in culprit carotid artery discrimination.

On the origin of the high capacitance of nitrogen-containing carbon nanotubes in acidic and alkaline electrolytes

The preparation of nitrogenated carbon nanotubes (N-CNT) using pyridine as a carbon precursor resulted in an eight-times increase in gravimetric capacitance.

Morphological and Functional Assessment of Carotid Plaques Have Similar Predictive Accuracy for Coronary Artery Disease

Background and Purpose—

Microwave radiometry allows noninvasive in vivo measuring of internal temperature of tissues reflecting inflammation. In the present study, we evaluated the predictive accuracy of this method for the diagnosis of coronary artery disease (CAD).

Methods—

Consecutive patients (n=287) scheduled for coronary angiography were included in the study. In carotid arteries of both groups, the following measurements were performed: (1) intima-media thickness (IMT max ) and (2) temperature measurements by microwave radiometry (Δ T max ). C-statistic and net reclassification improvement were used to compare the prediction ability of the markers IMT max and Δ T max for the presence of CAD and multivessel CAD.

Results—

Of 287 patients, 239 had stenoses ≥50% (CAD group), and 48 did not have significant stenoses (NO-CAD group). Δ T max was an independent predictor for the presence of CAD and multivessel CAD, showing similar predictive accuracy to intima-media thickness, as assessed by c-statistic and net reclassification improvement.

Conclusions—

Local inflammatory activation, as detected by microwave radiometry, has similar predictive accuracy to intima-media thickness for the presence and extent of CAD.

Detection of subclinical synovial inflammation by microwave radiometry

Objective

Microwave Radiometry is a non-invasive method which determines within seconds the in vivo temperature of internal tissues at a depth of 3–7 cm with an accuracy of ±0.2°C. In this proof-of-concept study, we tested the hypothesis that, in absence of relevant clinical signs, increased local temperature detected by microwave radiometry reflects subclinical synovial inflammation, using ultrasound as reference method.

Methods

Knees of healthy controls, subjects with recent knee trauma and symptom-free patients with rheumatoid arthritis (RA) or osteoarthritis were examined by placing the microwave radiometry sensor, a) at the upper one third of the anterior surface of the thigh (control-point), and b) over the suprapatellar recess. Ultrasound was performed immediately after and the possible presence of fluid and/or synovitis was correlated with microwave radiometry findings.

Results

In 30 healthy and 10 injured knees the temperature was always lower than thigh (32.3±1.1 and 31.8±1.4 versus 34.1±0.9 and 33.6±1.2°C with a difference (ΔΤ) of −1.8±0.2 and −1.9±0.4°C respectively). Of 40 RA and 20 osteoarthritis knees examined, ultrasound findings indicative of subclinical inflammation (fluid effusion and/or Doppler signal) were found in 24 and 12, respectively, in which the temperature was higher than healthy knees and ΔΤ was lower (−0.9±0.7 in RA and −1.0±0.5 in osteoarthritis versus −1.8±0.2°C, p<0.001). The 5 RA knees with power Doppler findings indicative of grade 2 inflammation had a ΔΤ 3 times lower compared to healthy (−0.6±0.6, p = 0.007), whereas the 9 RA and the 7 osteoarthritis knees with additionally fluid effusion, had even lower ΔΤ (−0.4±0.7, p<0.001).

Conclusion

Using a safe, rapid and easy-to-perform method, such as microwave radiometry, thermal changes within the knee joint may reflect non-clinically apparent joint inflammation. Refinement of this method, including production of sensors for small joints, could result to the development of the ideal objective tool to detect subclinical synovitis in clinical practice.