Quantifying digital vascular disease in patients with primary Raynaud's phenomenon and systemic sclerosis

Understanding the value of non-specific abnormal capillary dilations in presence of Raynaud's phenomenon: a detailed capillaroscopic analysis

BACKGROUND

Nailfold videocapillaroscopy (NVC) non-specific abnormalities may be present in subjects with isolated Raynaud's phenomenon (RP) before the potential transition to systemic sclerosis (SSc) specific microvascular alterations ('scleroderma pattern'). This study aims to investigate NVC non-specific abnormalities, notably capillary dilations, in RP patients, as possible forerunners of the 'scleroderma pattern'.

METHODS

A 10-year retrospective NVC-based investigation evaluated 55 RP patients sorted into 3 sex-matched and age-matched groups according to clinical evolution: 18 later developing SSc (cases), 19 later developing other connective tissue disease and 18 maintaining primary RP at long-term follow-up (controls). All patients had a basal NVC showing non-specific abnormalities, namely non-specific >30 µm dilated capillaries (30-50 μm diameter). Sequential NVCs were longitudinally evaluated using current standardised approach. Statistical analysis assessed the risk for developing a 'scleroderma pattern'.

RESULTS

Significantly larger capillary diameters were observed in cases versus controls both at basal NVC and during follow-up NVC (p=<0.05 to <0.001). Interestingly, controls showed stable NVC non-specific abnormalities over the study follow-up. The number of >30 µm dilated capillaries/mm at basal NVC was the strongest single predictor of 'scleroderma pattern' evolution with 24% increased risk per each dilated capillary (OR 1.24, 95% CI 1.17,1.32). Additionally, a tree-based analysis suggested the efferent (venous) diameter of the most dilated capillary on basal NVCas a variable of interest to identify patients maintaining primary RP.

CONCLUSION

This is the first study to describe an NVC 'prescleroderma signature' to potentially identify RP patients later developing a 'scleroderma pattern'.

Digital pressure with laser Doppler flowmetry is better than photoplethysmography to characterize peripheral arterial disease of the upper limbs in end-stage renal disease patients

OBJECTIVE

There is no consensual definition of significant peripheral arterial disease of the upper limbs. Patients with end-stage renal disease are usually explored with Doppler ultrasound, which seems insufficient to characterize and quantify the arterial disease in this anatomic site. Candidates for haemodialysis access tend to be increasingly older and have polyvascular disease, and a better assessment of the vascular status of their upper limbs with finger systolic blood pressure is necessary. Photoplethysmography is simple and currently used in practice, but laser Doppler flowmetry may be more sensitive for low values. Our objective is to investigate additional information in the digit assessment over the ultrasound assessment of the upper limbs of patients awaiting haemodialysis and compare digital pressure values taken by photoplethysmography and laser Doppler.

METHODS

All included patients with end-stage renal disease scheduled for haemodialysis access received a prospective evaluation of their upper limbs with a clinical examination of the hands, an arterial upper limb Doppler ultrasound, and finger systolic blood pressure using photoplethysmography and laser Doppler flowmetry. Significant upper limb arterial disease was defined by a finger systolic blood pressure below 60 mm Hg or a finger brachial pressure index below 0.7.

RESULTS

Twenty-four patients were included in the study. In all, 41.7% of patients (n = 10) had parietal calcifications to the antebrachial arteries on Doppler ultrasound, 8.3% of patients (n = 2) had bilateral finger systolic blood pressure values below 60 mm Hg with laser Doppler flowmetry (but not confirmed with photoplethysmography), and 16.6% of patients (n = 4) had a finger brachial pressure index below 0.7 on both laser Doppler flowmetry and photoplethysmography. While there was an agreement between these two methods, higher values were recorded with photoplethysmography. The Pearson coefficient was 0.493 for the median of basal digital pressures in absolute values and 0.489 for finger brachial pressure index (p < 0.001).

CONCLUSION

Our study confirms the need to evaluate significant upper limb arterial disease in patients with end-stage renal disease not only with Doppler ultrasound but also with an evaluation of the finger systolic blood pressure. The correlation of the finger systolic blood pressure values using laser Doppler flowmetry and photoplethysmography was poor, which was probably due to an overestimation of the pressures with photoplethysmography. Despite the absence of a gold standard, we suggest that Laser Doppler flowmetry should be used rather than photoplethysmography to better characterize significant peripheral arterial disease of the upper limbs in patients with end-stage renal disease, particularly before creation of a new haemodialysis access. Protocol Record on clinical trial 38RC19.285.

Infrared Thermography as a Method of Verification in Raynaud's Phenomenon

Raynaud's phenomenon (RP) is characterized by the episodic whitening of the fingers upon exposure to cold. A recently described thermographic algorithm was proposed as a diagnostic replacement of the currently applied finger systolic pressure (FSP) test. The aim of the study was to evaluate the performance of the thermographic algorithm when applied in patients suspected of having RP. Forty-three patients were examined using thermographic imaging after local cooling of the hands in water of 10 °C for 1 min. The thermographic algorithm was applied to predict the probability of RP. The performance of the algorithm was evaluated with different cut-off levels. A new algorithm was proposed based on patients from the target population. The performance of the tested algorithm was noninferior to the FSP test, when a cut-off level of 0.05 was applied, yielding a sensitivity and specificity of 69% and 58%, respectively. The accuracy was 66%. The FSP test had a sensitivity and specificity of 77% and 37%, respectively, and the accuracy was 59%. The thermographic method proved useful for detecting RP and was able to replace the FSP test as a diagnostic test. The alternative algorithm revealed that other thermographic variables were more predictive of the target population, but this should be verified in future patients.

Characteristic Features of Infrared Thermographic Imaging in Primary Raynaud's Phenomenon

Raynaud’s phenomenon (RP) is characterized by the episodic whitening of the fingers upon exposure to cold. Verification of the condition is crucial in vibration-exposed patients. The current verification method is outdated, but thermographic imaging seems promising as a diagnostic replacement. By investigating patients diagnosed with RP, the study aimed at developing a simple thermographic procedure that could be applied to future patients where verification of the diagnosis is needed. Twenty-two patients with primary RP and 58 healthy controls were examined using thermographic imaging after local cooling of the hands for 1 min in water of 10°C. A logistic regression model was fitted with the temperature curve characteristics to convey a predicted probability of having RP. The characteristics time to end temperature and baseline temperature were the most appropriate predictors of RP among those examined (p = 0.004 and p = 0.04, respectively). The area under the curve was 0.91. The cut-off level 0.46 yielded a sensitivity and specificity of 82% and 86%, respectively. The positive and negative predictive values were 69% and 93%, respectively. This newly developed thermographic method was able to distinguish between patients with RP and healthy controls and was easy to operate. Thus, the method showed great promise as a method for verification of RP in future patients. Trial registration: ClinicalTrials.gov NCT03094910.

Correlation between the infrared thermogram and microvascular abnormalities of the nailfold in patients with systemic sclerosis

INTRODUCTION

Systemic sclerosis (SSc) is a multisystemic disease with an extensive microvasculopathy. The gold standard for its investigation is nailfold videocapillaroscopy (NVC).

AIM

To assess the value of thermography (IRT) for the assessment of microvasculopathy in patients with SSc.

MATERIAL AND METHODS

Nineteen patients with limited cutaneous SSc were enrolled in the study. They underwent IRT imaging and NVC. An average temperature (Tavg) at the nailfold and a gradient of temperatures (ΔTavg) between the central metacarpus of the hand and the nailfold was determined for all fingers. NVC pictures were classified to capillaroscopic patterns according to Cutolo et al. system and they were analysed quantitatively to measure the density of capillaries and to calculate capillaroscopic skin ulcers risk index (CSURI) for each finger separately.

RESULTS

There was only a moderate correlation (0.4 < r < 0.6) between thermographic parameters and density of capillaries in fingers II-V (r = 0.5; p < 0.001 for Tavg and r = -0.45; p < 0.001 for ΔTavg), but none in thumbs (r = 0.29; p = 0.089 for Tavg and r = -0.19; p = 0.275 for ΔTavg). Early pattern was associated with a significantly greater surface temperature (Tavg) of nailfolds and essentially milder ΔTavg in fingers II-V when compared to all other capillaroscopic patterns in fingers II-V. Surface temperature (Tavg) was significantly lower and ΔTavg was markedly more pronounced in fingers II-V with a greater risk of development of digital ulcers (DU) calculated by CSURI.

CONCLUSIONS

Although IRT measurements correlate only moderately with density of capillaries, this technique seems to be substantial to determine the capillaroscopic pattern and to identify patients at greater risk of DU development.

Finger blood flow after the cold challenge with primary Raynaud's syndrome: a case report

Background 

Raynaud’s syndrome is a commonly encountered disorder. The relationship between the grade of Raynaud’s phenomenon and severity of vasoconstriction is unclear. Recently, various methods including colour Doppler ultrasonography have been used for assessment of vascularity of the extremities including fingers.

Case summary 

A 53-year-old man had a 6-year history of Raynaud’s phenomenon with typical tri-coloured changes proceeding from white, blue to red and slight pain and slight paresthaesia in the fingers of both hands when his fingers were exposed to cold. He was diagnosed with primary Raynaud’s syndrome. After treatment with the calcium channel blocker amlodipine (5 mg once daily), a cold challenge did not induce Raynaud’s phenomenon on the fingers in the present patient. After the cold challenge, colour Doppler ultrasonography showed that vascularity was markedly decreased or was absent, whereas there was little difference in skin colour of the fingers.

Discussion 

In Raynaud's phenomenon, vasospasm may occur even if the symptoms are well-controlled with a calcium channel blocker. It is unlikely that clinical symptoms in patients with Raynaud’s syndrome always reflect the severity of vasoconstriction in their fingers.

New perspectives in the imaging of Raynaud's phenomenon

The last 10-20 years have seen huge strides in imaging science. The aim of this review article is to share with the reader the key recent advances in non-invasive imaging of the digital (finger) vasculature in patients with Raynaud's phenomenon (RP), including in systemic sclerosis (SSc)-related digital vasculopathy. For the rheumatologist, seeing a patient with RP is an opportunity for early diagnosis of an underlying SSc-spectrum disorder or (conversely) for reassuring the patient with primary (idiopathic) RP. Non-invasive imaging techniques can help to provide diagnostic certainty. In addition, they can provide new insights into pathophysiology and have the potential to facilitate the development of much needed effective treatments by providing primary and secondary endpoints for randomized controlled trials: validation studies are ongoing. This review article focuses on nailfold capillaroscopy, thermography, and laser Doppler methods but also discusses (briefly) other technologies, including optical coherence tomography, multispectral imaging, and photoacoustic imaging. Key recent advances are the increasing use/availability of nailfold capillaroscopy (and better understanding of the role of low-cost hand-held devices), increased accessibility of thermography (including mobile phone thermography), and increased application of laser Doppler methods to the study of RP/digital vasculopathy (in particular of laser Doppler imaging and laser speckle contrast imaging, both of which measure blood flow over an area rather than at a single site). In an era of precision medicine, non-invasive imaging techniques can help stratify risk of (a) SSc in the patient with RP and (b) digital vascular disease progression in the patient with an SSc-spectrum disorder.

Multimodal Optical Diagnostics of the Microhaemodynamics in Upper and Lower Limbs

The introduction of optical non-invasive diagnostic methods into clinical practice can substantially advance in the detection of early microcirculatory disorders in patients with different diseases. This paper is devoted to the development and application of the optical non-invasive diagnostic approach for the detection and evaluation of the severity of microcirculatory and metabolic disorders in rheumatic diseases and diabetes mellitus. The proposed methods include the joint use of laser Doppler flowmetry, absorption spectroscopy and fluorescence spectroscopy in combination with functional tests. This technique showed the high diagnostic importance for the detection of disturbances in peripheral microhaemodynamics. These methods have been successfully tested as additional diagnostic techniques in the field of rheumatology and endocrinology. The sensitivity and specificity of the proposed diagnostic procedures have been evaluated.

Light Emitting Diodes based Photoacoustic Imaging and Potential Clinical Applications

Using low cost and small size light emitting diodes (LED) as the alternative illumination source for photoacoustic (PA) imaging has many advantages, and can largely benefit the clinical translation of the emerging PA imaging technology. Here, we present our development of LED-based PA imaging integrated with B-mode ultrasound. To overcome the challenge of achieving sufficient signal-to-noise ratio by the LED light that is orders of magnitude weaker than lasers, extensive signal averaging over hundreds of pulses is performed. Facilitated by the fast response of the LED and the high-speed driving as well as the high pulse repetition rate up to 16 kHz, B-mode PA images superimposed on gray-scale ultrasound of a biological sample can be achieved in real-time with frame rate up to 500 Hz. The LED-based PA imaging could be a promising tool for several clinical applications, such as assessment of peripheral microvascular function and dynamic changes, diagnosis of inflammatory arthritis, and detection of head and neck cancer.

Assessment of hand superficial oxygenation during ischemia/reperfusion in healthy subjects versus systemic sclerosis patients by 2D near infrared spectroscopic imaging

BACKGROUND AND OBJECTIVE

Patients affected by systemic sclerosis (SSc) develop functional and structural microcirculatory dysfunction, which progressively evolves towards systemic tissue fibrosis (sclerosis). Disease initially affects distal extremities, which become preferential sites of diagnostic scrutiny. This pilot investigation tested the hypothesis that peripheral microcirculatory dysfunction in SSc could be non-invasively assessed by 2D Near Infrared Spectroscopic (NIRS) imaging of the hand associated with Vascular Occlusion Testing (VOT). NIRS allows measurement of hemoglobin oxygen saturation (StO₂) in the blood perfusing the volume tissue under scrutiny.

METHODS

In five normal volunteers and five SSc patients we applied a multispectral oximetry imaging device (Kent camera, Kent Imaging, Calgary, Canada) to acquire StO₂ 2D maps of the whole hand palm during baseline, ischemia and reperfusion phase.

RESULTS

We found significant differences between controls and SSc patients in basal StO₂ (82.80 ± 2.51 vs 65.44 ± 7.96%, p = 0.0016), minimum StO₂ (59.35 ± 4.29 vs 40.73 ± 6.47%, p = 0.0007), final StO₂ (83.83 ± 4.09 vs 68.84 ± 11.41%, p = 0.02) and time to maximum StO₂ (40 ± 12.25 vs 62 ± 4.47 s, p = 0.005).

CONCLUSIONS

This is, to our knowledge, the first application of 2D NIRS imaging of the whole hand to the investigation of microvascular dysfunction in systemic sclerosis. The image processing presented here considered the StO₂ in the entire hand allowing a comprehensive view of the spatial heterogeneity of microvascular dysfunction.

Follow-Up of Treatment Response With Dynamic Doppler Ultrasound in Raynaud Phenomenon

OBJECTIVE

The purpose of this study was to investigate the role of flow parameters obtained with dynamic Doppler ultrasound in the objective follow-up of treatment response in patients with Raynaud phenomenon (RP).

SUBJECTS AND METHODS

The study included 33 patients with newly diagnosed primary RP, 31 with secondary RP, and 26 healthy participants (control subjects). Both groups of patients with RP underwent sonography before and after treatment. The control group underwent sonography once. Baseline digital arterial diameter and flow volume were measured at room temperature. After cold provocation, diameter and flow volume were measured again, and flow starting time and flow normalizing time were recorded. Data were measured as mean (± SD) values.

RESULTS

Baseline diameter did not significantly increase in either group after treatment (p > 0.05) (primary RP pretreatment, 0.79 ± 0.17 mm; posttreatment, 0.82 ± 0.19 mm; secondary RP pretreatment, 0.66 ± 0.13 mm; posttreatment, 0.68 ± 0.14 mm). Baseline flow volume increased significantly in both groups (p < 0.01) (primary RP pretreatment, 3.08 ± 2.96 mL/min; posttreatment, 3.91 ± 3.39 mL/min; secondary RP pretreatment, 2.14 ± 1.94 mL/min; posttreatment, 2.80 ± 2.15 mL/min). Cold provocation diameter increased significantly in both groups after treatment (p < 0.01) (primary RP pretreatment, 0.63 ± 0.15 mm; posttreatment, 0.70 ± 0.16 mm; secondary RP pretreatment, 0.56 ± 0.15 mm; posttreatment, 0.63 ± 0.13 mm). Cold provocation flow volume increased significantly in both groups after treatment (p < 0.01) (primary RP pretreatment, 1.18 ± 1.26 mL/min; posttreatment, 2.17 ± 2.16 mL/min; secondary RP pretreatment, 1.07 ± 1.40 mL/min; posttreatment, 1.46 ± 1.67 mL/min). After treatment, there was no statistically significant increase in flow starting time in patients with primary RP (p > 0.05), but there was a significant increase in patients with secondary RP (p < 0.05) (primary RP pretreatment, 1.15 ± 2.27 minutes; posttreatment, 0.61 ± 1.41 minutes; secondary RP pretreatment, 3.13 ± 4.81 minutes; posttreatment, 1.58 ± 2.36 minutes). After treatment, flow volume normalizing time improved significantly in both groups (p < 0.01) (primary RP pretreatment, 7.24 ± 7.60 minutes; posttreatment, 3.84 ± 3.39 minutes; secondary RP pretreatment, 9.58 ± 8.49 minutes; posttreatment, 4.32 ± 3.56 minutes). Among patients with primary RP, the posttreatment flow starting time was similar to that in the control group. Despite improvements, all remaining parameters differed in the treatment group compared with the control group.

CONCLUSION

Doppler ultrasound can be used effectively to monitor RP treatment. Blood flow volume can be measured without cold provocation to facilitate follow-up care of patients with RP.

A non-invasive technique for the evaluation of peripheral circulatory functions in female subjects with Raynaud's phenomenon

Japanese women now account for 43 percent of the labor force. A number of them are involved in construction, agricultural and forestry jobs. The aim of this study was to establish a non-invasive technique for the evaluation of peripheral circulatory functions in women with Raynaud's phenomenon (RP) and introduce a specific method for the assessment of vascular disturbances in females exposed to hand-transmitted vibration. The subjects of this study were 10 women with primary RP, 7 women with progressive systemic sclerosis (PSS) secondary to RP, and 17 females who were included as the control group. The evaluation of peripheral circulatory functions in all subjects was based on the values of finger blood flow (FBF) and finger skin temperature (FST) measured before, during and following a 5-min recovery period after the hand was immersed in cold water (5°C, 1 min). The measured values of FBF and FST of the primary RP group before and after the immersion test were significantly (p<0.01) lower compared to those of the control group. The technique applied in this study could be used as a non-invasive and tolerable technique to determine the digital circulatory functions in female subjects with RP.

Postocclusive Hyperemia Measured with Laser Doppler Flowmetry and Transcutaneous Oxygen Tension in the Diagnosis of Primary Raynaud's Phenomenon: A Prospective, Controlled Study

The aim of this study was to measure the sensitivity and specificity of transcutaneous oxygen tension and postocclusive hyperemia testing using laser Doppler flowmetry in patients with primary Raynaud's phenomenon. One hundred patients and one hundred controls were included in the study. Baseline microvascular blood flow and then time to peak flow following occlusion were measured using laser Doppler flowmetry. Afterwards, the transcutaneous oxygen tension was recorded. The sensitivities of baseline microvascular blood flow, postocclusive time to peak flow, and transcutaneous oxygen tension were 79%, 79%, and 77%, respectively. The postocclusive time peak flow had a superior specificity of 90% and area under the curve of 0.92 as compared to 66% and 0.80 for baseline microvascular flow and 64% and 0.76 for transcutaneous oxygen tension. Time to postocclusive peak blood flow measured by laser Doppler flowmetry is a highly accurate test for differentiating patients with primary Raynaud's phenomenon from healthy controls.

The Place of Nailfold Capillaroscopy Among Instrumental Methods for Assessment of Some Peripheral Ischaemic Syndromes in Rheumatology

Micro- and macrovascular pathology is a frequent finding in a number of common rheumatic diseases. Secondary Raynaud's phenomenon (RP) is among the most common symptoms in systemic sclerosis and several other systemic autoimmune diseases including a broad differential diagnosis. It should be also differential from other peripheral vascular syndromes such as embolism, thrombosis, etc., some of which lead to clinical manifestation of the blue toe syndrome. The current review discusses the instrumental methods for vascular assessments. Nailfold capillaroscopy is the only method among the imaging techniques that can be used for morphological assessment of the nutritive capillaries in the nailfold area. Laser-Doppler flowmetry and laser-Doppler imaging are methods for functional assessment of microcirculation, while thermography and plethysmography reflect both blood flow in peripheral arteries and microcirculation. Doppler ultrasound and angiography visualize peripheral arteries. The choice of the appropriate instrumental method is guided by the clinical presentation. The main role of capillaroscopy is to provide differential diagnosis between primary and secondary RP. In rheumatology, capillaroscopic changes in systemic sclerosis have been recently defined as diagnostic. The appearance of abnormal capillaroscopic pattern inherits high positive predictive value for the development of a connective tissue disease that is higher than the predictive value of antinuclear antibodies. In cases of abrupt onset of peripheral ischaemia, clinical signs of critical ischaemia, unilateral or lower limb involvement, Doppler ultrasound and angiography are indicated. The most common causes for such clinical picture that may be referred to rheumatologic consultation are the antiphospholipid syndrome, mimickers of vasculitides such as atherosclerosis with cholesterol emboli, and neoplasms.

Relation between blood flow and tissue blood oxygenation in human fingertip skin

BACKGROUND

Tissue blood flow (BF) is thought to be involved in the regulation of tissue blood oxygenation (StO2). The purpose of the present study was to show the relation between BF and StO2 by measuring them simultaneously under different conditions.

METHODS

Twenty-one healthy subjects (age 21-30years) participated in this study. We measured BF and StO2 in a small area of skin (fingertip, palm, forearm) simultaneously using a laser Doppler flowmeter and a tissue oxygenation monitor. Three measurements were made at rest while performing mental arithmetic and during constriction of the ipsilateral upper arm.

RESULTS

At rest, BF and StO2 were higher in the fingertip than in the palm or forearm (p<0.01). Performing mental arithmetic produced significant decreases in BF, oxygenated hemoglobin, and StO2 in the fingertip (p<0.05). Constriction of the ipsilateral upper arm produced significant decreases in BF and StO2 (p<0.05) and an increase in oxygenated hemoglobin (p<0.05). Both procedures produced significant increases in deoxygenated hemoglobin (p<0.05), which was in antiphase to the decrease in StO2.

CONCLUSIONS

BF decrease produced a significantly decreased StO2 in fingertip skin. The results show that simultaneous measurement of BF and StO2 is beneficial for showing the close relation between them.

Low local blood perfusion, high white blood cell and high platelet count are associated with primary tumor growth and lung metastasis in a 4T1 mouse breast cancer metastasis model

It was originally thought that no single routine blood test result would be able to indicate whether or not a patient had cancer; however, several novel studies have indicated that the median survival and prognosis of cancer patients were markedly associated with the systemic circulation features of cancer patients. In addition, certain parameters, such as white blood cell (WBC) count, were largely altered in malignant tumors. In the present study, routine blood tests were performed in order to observe the change of blood cells in tumor-bearing mice following the implantation of 4T1 breast cancer cells into the mammary fat pad; in addition, blood flow in breast tumor sites was measured indirectly using laser Doppler perfusion imaging (LDPI), in an attempt to explain the relevance between the blood circulation features and the growth or metastasis of breast cancer in mice model. The LDPI and blood test results indicated that the implantation of 4T1 breast cancer cells into BALB/c mice led to thrombosis as well as high WBC count, high platelet count, high plateletcrit and low blood perfusion. Following implantation of the 4T1 cells for four weeks, the lung metastatic number was determined and the Pearson correlation coefficient revealed that the number of visceral lung metastatic sites had a marked negative association with the ratio of basophils (BASO%; r=-0.512; P<0.01) and the mean corpuscular hemoglobin was significantly correlated with primary tumor weight (r=0.425; P<0.05). In conclusion, the results of the present study demonstrated that tumor growth led to thrombosis and acute anemia in mice; in addition, when blood BASO% was low, an increased number of lung metastases were observed in tumor-bearing mice.

Simultaneous estimation of bidirectional particle flow and relative flux using MUSIC-OCT: phantom studies

In an optical coherence tomography (OCT) scan from a living tissue, red blood cells (RBCs) are the major source of backscattering signal from moving particles within microcirculatory system. Measuring the concentration and velocity of RBC particles allows assessment of RBC flux and flow, respectively, to assess tissue perfusion and oxygen/nutrition exchange rates within micro-structures. In this paper, we propose utilizing spectral estimation techniques to simultaneously quantify bi-directional particle flow and relative flux by spectral estimation of the received OCT signal from moving particles within capillary tubes embedded in tissue mimicking phantoms. The proposed method can be directly utilized for in vivo quantification of capillaries and microvessels. Compared to the existing methods in the literature that can either quantify flow direction or power, our proposed method allows simultaneous flow (velocity) direction and relative flux (power) estimation.

Development of a hybrid microwave-optical thermoregulation monitor for the muscle

This paper presents the latest development of the hybrid microwave-optical thermoregulation monitor for the muscle. It is capable of warming the muscle and measuring the subsequent blood volume changes, using a novel microwave applicator with integrated optical probes. The challenge is to measure the thermoregulation response in deep tissue while minimizing any effect from the skin layer. We have introduced a skin cooling device, an additional integrated optical Laser Doppler flow monitoring probe and a temperature sensor to measure skin blood flow and temperature, respectively. The result shows that skin cooling is essential to minimize skin flow changes during microwave warming. The hybrid probe was placed on a human thigh to measure oxy/deoxy/total haemoglobin concentration changes (ΔHbO₂/ΔHHb/ΔHbT), skin flux and temperature upon microwave warming. Without skin cooling, the skin temperature was elevated by 4 °C and both ΔHbO₂/ΔHbT and skin flux increased, showing microwave warming occurring in both the skin and muscle. With skin cooling, the skin temperature was kept relatively constant. While ΔHbO₂/ΔHbT increased, the skin flux was relatively stable, showing a preferential microwave warming in the muscle, rather than the skin.

Digital thermography of the fingers and toes in Raynaud's phenomenon

The aim of this study was to determine whether skin temperature measurement by digital thermography on hands and feet is useful for diagnosis of Raynaud's phenomenon (RP). Fifty-seven patients with RP (primary RP, n = 33; secondary RP, n = 24) and 146 healthy volunteers were recruited. After acclimation to room temperature for 30 min, thermal imaging of palmar aspect of hands and dorsal aspect of feet were taken. Temperature differences between palm (center) and the coolest finger and temperature differences between foot dorsum (center) and first toe significantly differed between patients and controls. The area under curve analysis showed that temperature difference of the coolest finger (cutoff value: 2.2℃) differentiated RP patients from controls (sensitivity/specificity: 67/60%, respectively). Temperature differences of first toe (cutoff value: 3.11℃) also discriminated RP patients (sensitivity/specificity: about 73/66%, respectively). A combination of thermographic assessment of the coolest finger and first toe was highly effective in men (sensitivity/specificity : about 88/60%, respectively) while thermographic assessment of first toe was solely sufficient for women (sensitivity/specificity: about 74/68%, respectively). Thermographic assessment of the coolest finger and first toe is useful for diagnosing RP. In women, thermography of first toe is highly recommended.

Assessment of skin microcirculation by laser Doppler flowmetry in systemic sclerosis patients

Introduction

First lesions to occur in the course of systemic sclerosis (SSc) involve microcirculation.

Aim

The study involved assessment of the suitability of laser Doppler flowmetry (LDF) in examination of the performance of skin microcirculation in the distal portion of the upper extremity in SSc patients.

Material and methods

Overall the study involved 27 patients with systemic sclerosis. The control group comprised age – and gender-matched 27 healthy individuals. All the study subjects underwent microcirculation perfusion measurement at rest (rest flow – RF) as well as microcirculatory flow challenge tests – reactive hyperaemia test (RHT) and thermal stimulation test (TST).

Results

The study did not show any differences in the skin microcirculation perfusion at rest between the test group and the control, while reactive hyperaemia test results revealed significantly lower skin microcirculation perfusion values during the cuff inflation in SSc patients, as compared to the controls. In the test group, a lower perfusion value was observed during secondary hyperaemia following cuff release. Comparative analysis of skin microcirculation perfusion changes during the thermal stimulation test revealed a significantly lower change of the perfusion value and longer time of return to the baseline in the test group as compared to the control group.

Conclusions

The study performed has shown the suitability of LDF in the assessment of the microangiopathy degree in systemic sclerosis patients. The skin perfusion value in SSc patients should be assessed on the basis of parameters obtained in microcirculation challenge tests.

Development of a hybrid microwave-optical tissue oxygenation probe to measure thermal response in the deep tissue

The design of a new non-invasive hybrid microwave-optical tissue oxygenation probe is presented, which consists of a microwave biocompatible antenna and an optical probe. The microwave antenna is capable of inducing localised heat in the deep tissue, causing tissue blood flow and therefore tissue oxygenation to change. These changes or thermal responses are measured by the optical probe using near-infrared spectroscopy. Thermal responses provide important information on thermoregulation in human tissue. The first prototype of the biocompatible antenna was developed and placed on the human calf for in vivo experiments. The measured results include oxy-, deoxy- and total haemoglobin concentration changes (ΔHbO2/ΔHHb/ΔHbT), tissue oxygenation index and the normalised tissue haemoglobin index for two human subjects. Both ΔHbO2 and ΔHbT show an increase during 5 min of microwave exposure. The thermal response, defined as the ratio of the increase in ΔHbT to the time duration, is 7.7 μM/s for subject 1 (fat thickness = 6.8 mm) and 18.9 μM/s for subject 2 (fat thickness = 5.0 mm), which may be influenced by the fat thicknesses. In both subjects, ΔHbO2 and ΔHbT continued to increase for approximately another 70 s after the microwave antenna was switched off.

'Go with the flow ': a review of methods and advancements in blood flow imaging

Physics has delivered extraordinary developments in almost every facet of modern life. From the humble thermometer and stethoscope to X-Ray, CT, MRI, ultrasound, PET and radiotherapy, our health has been transformed by these advances yielding both morphological and functional metrics. Recently high resolution label-free imaging of the microcirculation at clinically relevant depths has become available in the research domain. In this paper, we present a comprehensive review on current imaging techniques, state-of-the-art advancements and applications, and general perspectives on the prospects for these modalities in the clinical realm.

The pathogenesis, diagnosis and treatment of Raynaud phenomenon

The past 10 years have seen the publication of results from several multicentre clinical trials in primary and systemic sclerosis (SSc)-related Raynaud phenomenon. The publication of these studies has occurred as a result of new insights into the pathogenesis of Raynaud phenomenon, which are directing new treatment approaches, and increased international collaboration between clinicians and scientists. Although the pathogenesis of Raynaud phenomenon is complex, abnormalities of the blood vessel wall, of neural control mechanisms and of intravascular (circulating) factors are known to interact and contribute. Key players relevant in drug development include nitric oxide, endothelin-1, alpha adrenergic receptor activation, abnormal signal transduction in vascular smooth muscle, oxidative stress and platelet activation. The main advances in diagnosis have been a clearer understanding of autoantibodies and of abnormal nailfold capillary patterns as independent predictors of SSc, and widespread use and increased availability of capillaroscopy. The ultimate aim is to translate the advances made in the pathophysiology and early diagnosis into development of treatments to prevent and reverse digital vascular dysfunction and injury. This Review provides an update of the pathogenesis, diagnosis and treatment of Raynaud phenomenon. Current and future treatment approaches are discussed, and some key unanswered questions are highlighted.

Influence of the cold challenge on the discriminatory capacity of the digital distal-dorsal difference in the thermographic assessment of Raynaud's phenomenon

OBJECTIVES

To investigate the influence of a standardised cold stress test (CST) on the thermographic 'distal-dorsal difference' (DDD) and its capacity to differentiate between disease states in the assessment of Raynaud's phenomenon (RP), and to compare the discriminatory capacity of the DDD of individual digits with composite indices of multiple digits.

METHODS

Thermographic images of 55 patients with primary RP (PRP, n=27) and systemic sclerosis (SSc, n=28) who had undergone assessment of RP were retrospectively reviewed. The DDD for individual digits, and composite scores of multiple digits, were calculated at baseline (23°C), and at 10 min following CST. The discriminatory capacity of the mean DDD, and the proportion of patients with a clinically meaningful DDD of <-1°C, were assessed for individual digits and composite indices, at baseline and following cold challenge.

RESULTS

There was a more pronounced decrease of the DDD (indicating reduced distal perfusion) following CST in patients with PRP compared to SSc. The disparity in response to CST between groups narrowed the differences that were present at baseline, reducing the discriminatory capacity of the DDD for all endpoints. Sparing of the thumbs occurs to a greater extent in SSc (P<0.005) compared with PRP (P<0.05) but does not facilitate differentiation between groups. Large variability of the DDD within groups precludes easy differentiation between disease states. Composite indices of multiple digits are preferable to individual digital assessment.

CONCLUSIONS

The discriminatory capacity of the DDD is lost following CST. The CST may not be essential in the thermographic assessment of RP, potentially allowing greater use of thermography in clinical practise.

Functional infrared imaging of paroxysmal ischemic events in patients with Raynaud's phenomenon

The use of thermal infrared (IR) imaging together with the study of the thermal recovery from a controlled cold challenge has been proposed in the diagnosis and follow-up of therapeutic response of Raynaud's Phenomenon (RP) and Systemic Sclerosis (SSc). The controlled cold challenge test usually performed during IR investigations may induce a RP in patients with the latter condition. In our Institution we routinely perform capillaroscopy and thermal IR to follow-up SSc patients. In this paper, we describe the thermal recovery patterns shown by two SSc patients (a 40 year-old male with diffuse variant of SSc and a 71 year-old female with a limited variant of SSc) who presented ischemic and paroxysmal RP attack while recovering from the routine controlled cold challenge test. During RP attack, the cutaneous temperature of some fingers continued to decrease for some minutes even after the cessation of the cold stress. To the best of our knowledge, to date, no literature report has documented the thermal behaviour of SSc patients' fingers which occasionally present ischemic and paroxysmal response. Triggering of ischemic RP attack appears to not rely only on morphological and structural finger impairment, but also upon other aspects, like the emotional attitude of the subject and the possible discomfort experienced with the proceeding of the functional cold stress test.

The specificity of capillaroscopic pattern in connective autoimmune diseases. A comparison with microvascular changes in diseases of social importance: arterial hypertension and diabetes mellitus

Capillaroscopy is a method with substantial value for diagnosis and differentiation of primary and secondary Raynaud's phenomenon in rheumatic diseases. The most specific finding is in systemic sclerosis--the so-called "scleroderma pattern." which is characterized by the presence of dilated capillaries, hemorrhages, avascular areas, and neoangiogenesis. Similar changes are found in patients with dermatomyositis, overlap syndromes, and others and are termed "scleroderma-like pattern." For the development of these patterns, the most specific finding in the early phase is appearance of dilated capillaries. Capillaroscopic changes in connective autoimmune diseases are specific and differ significantly from those of that can be found in other diseases. Diseases of social importance such as diabetes mellitus and arterial hypertension often present as comorbidity in patients with rheumatic diseases. In diabetes mellitus, the capillaroscopic examination does not show dilated capillaries until the advanced stages of the disease. In the late stages of connective tissue disease, a loss of capillaries is typical. In addition, in diabetes mellitus, the diabetic stiff-hand syndrome and sclerodactyly are common complications, which have to be differentiated from similar signs in rheumatic diseases, and capillaroscopic examination appears to be useful in these situations. In arterial hypertension, a reduced capillary density in different body regions has been observed in patients with established disease as well as in preclinical stages. Analogous phenomenon of reduction in the nail-fold area has also been observed in a group of patients with essential hypertension, none of whom previously received hypertensive drugs.

Therapeutic angiogenesis in patients with systemic sclerosis by autologous transplantation of bone-marrow-derived cells

We examined the efficacy and safety of autologous transplantation of bone-marrow-derived cells in patients with intractable ulcers caused by systemic sclerosis. Eight patients with ulcers resistant to treatment were enrolled. Bone marrow cells were gathered from the bilateral iliac crests with multiple repositioning bone marrow needles, and bone-marrow-derived mononuclear cells were isolated and injected into skeletal muscles of the ischemic limb. Visual analog scale (VAS), Sclerosis Health Assessment Questionnaire (SHAQ), modified Rodnan total skin score (mTSS), and the size and depth of the ulcer were examined. Thermography, capillaroscopy, intra-arterial digital subtraction angiography (IA-DSA), and laser Doppler flowmetry were also examined before and after transplantation. In all patients, reduction of ulcer size and improvement of VAS were observed after treatment. Elevation of surface temperature, increase of blood flow volume, and new capillaries of the nail bed were also found after our treatment. There were no major adverse effects of this treatment. Autologous transplantation of bone-marrow-derived cells was shown to be a novel and useful approach to intractable ulcers in systemic sclerosis.

Finger thermoregulatory model assessing functional impairment in Raynaud's phenomenon

Raynaud's Phenomenon (RP) is a paroxysmal vasospastic disorder of small arteries, pre-capillary arteries, and cutaneous arteriovenous shunts of the extremities, typically induced by cold exposure and emotional stress. RP is either primary (PRP) or secondary to systemic sclerosis. In this study we use Control System Theory to model finger thermoregulatory processes in response to a standardized cold challenge (a diagnostic test routinely performed for differential diagnosis of RP). The proposed model is based on a homeostatic negative feedback loop, characterized by five distinct parameters which describe how the control mechanisms are activated and maintained. Thermal infrared imaging data from 14 systemic sclerosis subjects (SSc), 14 PRP, and 16 healthy control subjects (HCS) were processed. HCS presented the fastest active recovery, with the highest gain. PRP presented the slowest and weakest recovery, mostly due to passive heat exchange with the environment. SSc presented an intermediate behavior, with the longest delay of response onset. The estimated model parameters elucidated the level of functional impairment expressed in the various forms of this disease.

The complexity of managing systemic sclerosis: screening and diagnosis

The difficulties inherent in diagnosing, screening and treating SSc are reflected by the complex pathology of the disease, which involves the development of severe organ-based complications that reduce both quality of life and overall survival. Early detection and prompt treatment of such complications depend upon a successful and timely screening strategy, which, in turn, requires cooperation between disciplines and good collaborative links at all stages of the disease. Establishment of a disease registry for SSc may also be of benefit, as such registries facilitate longitudinal observation of trends in disease presentation, management and outcome. They may also help to determine potential risk factors and identify those patient subgroups that face the highest risk of developing disease. In patients with known or suspected SSc, a panel of disease-specific markers--such as autoantibodies, cell activation markers and markers of organ involvement--may help to establish the diagnosis and assess prognosis; however, changes in serum levels of such markers throughout the course of SSc should be interpreted with caution, as they may not always correlate with disease activity. Nail-fold capillaroscopy is a promising tool for SSc assessment and may provide useful diagnostic and prognostic information, although further research is required to clarify its role in evaluating disease evolution.

The role of capillaroscopy in differentiation of primary and secondary Raynaud's phenomenon in rheumatic diseases: a review of the literature and two case reports

The purpose of this study is to study and systematize the current knowledge about the role of capillaroscopy in differentiation of primary and secondary Raynaud's phenomenon (RP) in rheumatic diseases. This method is a review of the literature. Capillaroscopy is of crucial value for diagnosis and differentiation of primary and secondary RP in rheumatic diseases. The appearance of abnormal capillaroscopic pattern inherits high positive predictive value for the development of systemic rheumatic disease. The most specific pattern is found in systemic sclerosis (SSc), so called "scleroderma pattern", which is characterized by the presence of dilated capillaries, hemorrhages, avascular areas and neoangiogeneis. It is found in more than 90% of patients with overt SSc. Similar changes are found in patients with dermatomyositis, mixed connective tissue disease, undifferentiated connective tissue disease and they are called "scleroderma-like pattern". Absence of abnormal capillaroscopic findings can be regarded as a diagnostic criterion for primary RP. Inclusion of pathologic capillaroscopic pattern may increase the sensitivity of ACR classification criteria for SSc. In conclusion, capillaroscopy is of crucial importance for the differentiation of primary and secondary RP in rheumatic diseases, and also in differentiation between different forms of connective tissue diseases as well as for their early diagnosis.

Noninvasive evaluation of upper-extremity vascular perfusion

Evaluation of vascular disorders of the upper extremity requires an anatomic and functional approach. The combination of a good history and physical examination, laboratory testing, and specialized vascular laboratory studies will help detect any underlying collagen vascular disease or coagulopathy and provide physiologic-specific and patient-oriented management. This paper reviews the currently available noninvasive modalities for the evaluation of upper-extremity perfusion.

Biomedical applications of functional infrared imaging

This paper introduces the reader to the functional infrared imaging, that is the application to the biomedical field of high-technology infrared imaging devices combined to the modeling of the bio-heat processes involved in the body thermoregulation. Such an approach allows defining quantitative parameters for diagnosis and monitoring. Some recent biomedical applications of the technique are then shown and explained.

Thermal Parametric Imaging in the Evaluation of Skin Burn Depth

The aim of this paper is to determine the extent to which infrared (IR) thermal imaging may be used for skin burn depth evaluation. The analysis can be made on the basis of the development of a thermal model of the burned skin. Different methods such as the traditional clinical visual approach and the IR imaging modalities of static IR thermal imaging, active IR thermal imaging and active-dynamic IR thermal imaging (ADT) are analyzed from the point of view of skin burn depth diagnostics. In ADT, a new approach is proposed on the basis of parametric image synthesis. Calculation software is implemented for single-node and distributed systems. The properties of all the methods are verified in experiments using phantoms and subsequently in vivo with animals with a reference histopathological examination. The results indicate that it is possible to distinguish objectively and quantitatively burns which will heal spontaneously within three weeks of infliction and which should be treated conservatively from those which need surgery because they will not heal within this period.