Vascular imaging

Harnessing the power of bioprinting for the development of next-generation models of thrombosis

Thrombosis, a leading cause of cardiovascular morbidity and mortality, involves the formation of blood clots within blood vessels. Current animal models and in vitro systems have limitations in recapitulating the complex human vasculature and hemodynamic conditions, limiting the research in understanding the mechanisms of thrombosis. Bioprinting has emerged as a promising approach to construct biomimetic vascular models that closely mimic the structural and mechanical properties of native blood vessels. This review discusses the key considerations for designing bioprinted vascular conduits for thrombosis studies, including the incorporation of key structural, biochemical and mechanical features, the selection of appropriate biomaterials and cell sources, and the challenges and future directions in the field. The advancements in bioprinting techniques, such as multi-material bioprinting and microfluidic integration, have enabled the development of physiologically relevant models of thrombosis. The future of bioprinted models of thrombosis lies in the integration of patient-specific data, real-time monitoring technologies, and advanced microfluidic platforms, paving the way for personalized medicine and targeted interventions. As the field of bioprinting continues to evolve, these advanced vascular models are expected to play an increasingly important role in unraveling the complexities of thrombosis and improving patient outcomes. The continued advancements in bioprinting technologies and the collaboration between researchers from various disciplines hold great promise for revolutionizing the field of thrombosis research.

Peripheral vasoreactivity in acute ischemic stroke with hemiplegia

The association between vasomotor tone of the peripheral arteries and cerebral hemisphere function has not been established. This study analyzed the peripheral vasoreactivity of patients with acute ischemic stroke and hemiplegia using a modified Raynaud scan, which is a new technology for blood flow measurement. In this retrospective case–control study, we examined patients with unilateral weakness consistent with ischemic lesions who underwent brain magnetic resonance imaging and modified Raynaud scanning within five days from the onset of symptoms. The modified Raynaud scan was used to quantify the radioactivity of the bilateral fingertips during rest and cooling-heating thermal stress conditions and estimate vasoreactivity based on the change in the blood amount per time under rest-thermal stress. The subjects were classified into the preserved and impaired groups based on their degrees of vasomotor reaction. Based on the modified Raynaud scanning, 37 (mean age = 69.1 ± 10.6) and 32 (mean age = 62.6 ± 11.8) subjects were allocated to the preserved and impaired groups, respectively. Binary logistic regression showed that the affected limb edema (odds ratio (OR) 6.15; confidence interval (CI) 1.40–26.97; p = 0.016) and anterior circulation (OR 3.68; CI 1.01–13.48; p = 0.049) were associated with impaired vasoreactivity. The modified Raynaud scans confirmed that central lesions in the anterior circulation with hemiparesis may influence the vasoreactivity of edematous peripheral arteries. These results may inform treatment and rehabilitation for stroke patients with hemiparesis.

The Therapeutic Efficacy of Botulinum Toxin in Treating Scleroderma-Associated Raynaud's Phenomenon: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial

OBJECTIVE

To assess the therapeutic efficacy of local injections of botulinum toxin type A (Btx-A) in improving blood flow to the hands of patients with Raynaud's phenomenon (RP) secondary to scleroderma.

METHODS

In this randomized, double-blind, placebo-controlled clinical trial, patients with scleroderma-associated RP received Btx-A (50 units in 2.5 ml sterile saline) in one randomly selected hand and sterile saline (2.5 ml) in the opposite hand. Follow-up at 1 and 4 months postinjection included laser Doppler imaging of hands, patient-reported outcomes, and physical examination. We compared outcomes using paired t-tests and population-average generalized models with generalized estimating equations.

RESULTS

Of 40 patients enrolled, 25 had limited scleroderma and 15 had diffuse scleroderma. From baseline to 1-month follow-up, there was a greater reduction in average blood flow in Btx-A-treated hands compared to placebo-treated hands. The model estimated that this difference was statistically significant (average difference -30.08 flux units [95% confidence interval -56.19, -3.98], P for interaction = 0.024). This difference was mainly influenced by patients with longstanding RP and diffuse scleroderma. Change in blood flow at 4-month follow-up was not significantly different between groups. Clinical measures (QuickDASH, McCabe Cold Sensitivity Score, pain on a visual analog scale, and Raynaud's Condition Score) improved slightly for Btx-A-treated hands.

CONCLUSION

Our laboratory-based laser Doppler imaging flow data do not support using Btx-A to treat RP in all scleroderma patients. The secondary clinical outcomes suggest some positive effect, but its clinical meaningfulness is questionable. The role of Btx-A in treating RP should be further studied with more homogeneous patient populations and in unique clinical situations such as acute digital ischemia.

Methods for the morphological and functional evaluation of microvascular damage in systemic sclerosis

Systemic sclerosis is a connective tissue disease characterized by alterations in microvascular structure and function. In these patients, numerous studies have demonstrated a relationship between capillary morphology and peripheral blood perfusion. Nailfold videocapillaroscopy reveals the peripheral microvascular morphology and thus allows classification and scoring of capillary abnormalities with respect to different microangiopathy patterns (early, active, and late). Laser Doppler flowmetry and laser speckle contrast analysis can be used to estimate cutaneous blood flow through microvessels and to assess and quantify blood perfusion at peripheral sites. These two methods are also used to identify changes in digital blood perfusion after the infusion of vasodilators.

Assessment of lower limb prosthesis through wearable sensors and thermography

This study aimed to explore the application of infrared thermography in combination with ambulatory wearable monitoring of temperature and relative humidity, to assess the residual limb-to-liner interface in lower-limb prosthesis users. Five male traumatic transtibial amputees were involved, who reported no problems or discomfort while wearing the prosthesis. A thermal imaging camera was used to measure superficial thermal distribution maps of the stump. A wearable system for recording the temperature and relative humidity in up to four anatomical points was developed, tested in vitro and integrated with the measurement set. The parallel application of an infrared camera and wearable sensors provided complementary information. Four main Regions of Interest were identified on the stump (inferior patella, lateral/medial epicondyles, tibial tuberosity), with good inter-subject repeatability. An average increase of 20% in hot areas (P < 0.05) is shown after walking compared to resting conditions. The sensors inside the cuff did not provoke any discomfort during recordings and provide an inside of the thermal exchanges while walking and recording the temperature increase (a regime value is ~+1.1 ± 0.7 °C) and a more significant one (~+4.1 ± 2.3%) in humidity because of the sweat produced. This study has also begun the development of a reference data set for optimal socket/liner-stump construction.

Infrared thermal imaging as a novel evaluation method for deep vein thrombosis in lower limbs

PURPOSE

Early detection of deep vein thrombosis (DVT) is critical to prevent clinical pulmonary thromboembolism. However, most conventional methods for diagnosing DVT are functionally limited and complicated. The aim of this study was to evaluate the value of infrared-thermal-imaging (IRTI), a novel imaging detection or screening technique, in diagnosis of DVT in animal models.

METHODS

DVT model of femoral veins was established in nine New Zealand rabbits. The right hind femoral vein was embolized and the contralateral one served as a nonembolized control. Measurements of IRTI, compression ultrasonography (CPUS), and angiography under ultrasonic observation (AGUO) were performed at three time points: T1 (baseline, 10 min prior to surgery), T2 (2 h after thrombin injection), and T3 (48 h postoperatively). Qualitative pseudocolor analysis and quantitative temperature analysis were performed based on mean area temperature (Tav) and mean curvilinear temperature (Tca) of the region of interest as shown in IRTI. Temperature differences (TD) in Tav (TD(Tav)) and Tca (TD(Tca)) between the DVT and control sides were computed. Comparative statistical analysis was carried out by paired t-test and repeated measure, while multiple comparisons were performed by using Greenhouse-Geisser and Bonferroni approach. Values of P < 0.05 and P < 0.01 were considered statistically significant and highly significant.

RESULTS

Modeling of DVT was successful in all rabbits, as confirmed by CPUS and AGUO and immediately detected by IRTI. IRTI qualitative analysis of pseudocolor revealed that the bilateral temperatures were apparently asymmetrical and that there were abnormally high temperature zones on the DVT side where thrombosis formed. The results of paired t-test of Tav and Tca between DVT side and control sides did not reveal statistical difference at T1 (Tav: P = 0.817; Tca: P = 0.983) yet showed statistical differences at both T2 (Tav: P = 0.023; Tca: P = 0.021) and T3 (Tav: P = 0.016; Tca: P = 0.028). Results of repeated measure and multiple comparisons of TD(Tav) and TD(Tca) were highly different and significant differences across the T2 (TD(Tav): P = 0.009; TD(Tav): P = 0.03) and T3 (TD(Tav): P = 0.015; TD(Tav): P = 0.021).

CONCLUSIONS

IRTI temperature quantitative analysis may help further detection of DVT. Additionally, IRTI could serve as a novel detection and screening tool for DVT due to its convenience, rapid response, and high sensitivity.

'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 application of infrared thermography in evaluation of patients at high risk for lower extremity peripheral arterial disease

OBJECTIVE

We investigated the usefulness of infrared thermography in evaluating patients at high risk for lower extremity peripheral arterial disease (PAD), including severity, functional capacity, and quality of life.

METHODS

A total of 51 patients (23 males; age 70 ± 9.8 years) were recruited. They completed three PAD-associated questionnaires, including walking impairment, vascular quality of life, and 7-day physical activity recall questionnaires before a 6-minute walking test (6MWT). Ankle-brachial index (ABI) and segmental pressure were analyzed for PAD diagnosis and stenotic level assessment. The cutaneous temperature at shin and sole were recorded by infrared thermography before and after the walk test. Detailed demographic information and medication list were obtained.

RESULTS

Twenty-eight subjects had abnormal ABI (ABI <1), while PAD was diagnosed in 20. No subjects had non-compressible artery (ABI >1.3). Demographic profiles and clinical parameters in PAD and non-PAD patients were similar, except for age, smoking history, and hyperlipidemia. PAD patients walked shorter distances (356 ± 102 m vs 218 ± 92 m; P < .001). Claudication occurred in 14 patients, while seven failed in completing the 6MWT. The rest temperatures were similar in PAD and non-PAD patients. However, the post-exercise temperature dropped in the lower extremities with arterial stenosis, but was maintained or elevated slightly in the extremities with patent arteries (temperature changes at sole in PAD vs non-PAD patients: -1.25 vs -0.15°C; P < .001). The exercise-induced temperature changes at the sole were not only positively correlated with the 6MWD (Spearman correlation coefficient = 0.31, P = .03), but was also correlated with ABI (Spearman correlation coefficient = 0.48, P < .001) and 7-day physical activity recall scores (Spearman correlation coefficient = 0.30, P = .033).

CONCLUSION

By detecting cutaneous temperature changes in the lower extremities, infrared thermography offers another non-invasive, contrast-free option in PAD evaluation and functional assessment.

Infrared thermal imaging for detection of peripheral vascular disorders

Body temperature is a very useful parameter for diagnosing diseases. There is a definite correlation between body temperature and diseases. We have used Infrared Thermography to study noninvasive diagnosis of peripheral vascular diseases. Temperature gradients are observed in the affected regions of patients with vascular disorders, which indicate abnormal blood flow in the affected region. Thermal imaging results are well correlated with the clinical findings. Certain areas on the affected limbs show increased temperature profiles, probably due to inflammation and underlying venous flow changes. In general the temperature contrast in the affected regions is about 0.7 to 1° C above the normal regions, due to sluggish blood circulation. The results suggest that the thermal imaging technique is an effective technique for detecting small temperature changes in the human body due to vascular disorders.

Investigation of peripheral vascular disorders using thermal imaging

Infrared thermal imaging has been used to study non-invasive diagnosis of peripheral vascular diseases. Temperature gradients indicating abnormal blood flow in the affected regions of patients with vascular disorders are well correlated with clinical findings. The temperature in the affected regions was about 0.7—1°C above the normal regions, due to slow blood circulation. Thermal imaging is an effective technique for detecting small temperature changes due to vascular disorders, it is non-invasive, portable, compact and safe.

[Acute mesenteric ischemia in a patient with relapsing polychondritis]

We report about a 43-year old woman with relapsing polychondritis, admitted with progressive malaise, fatigue, anorexia and profound weight loss. Two years ago a nasal chondritis with characteristic changes of the nasal profil, scleritis, laryngitis and unspecific general symptoms (fever, fatigue, signs of a systemic inflammation) developed and relapsing polychondritis was diagnosed. The patient was treated initially with azathioprine followed by methotrexate in combination with ciclosporine and glucocorticoids. During the hospitalization her condition slowly worsened, and crampy abdominal pain developed subsequently with massive tenderness, rebound and guarding. The clinically presumed diagnosis of ileus and peritonitis was radiomorphologically confirmed with signs of enteric perforation and a laparatomy was performed. A complete occlusion of the A. mesenterica superior and stenosis of the truncus coeliacus were diagnosed followed by a revascularization with an aorto-mesenteric bypass and subsequent resection of the necrotic ischemic ileum. An association with various autoimmune disorders including vasculitic syndromes is well known for relapsing polychondritis. The case demonstrated a progressive mesenteric ischemia with the acute exacerbation caused by a vasculitic mesenterial occlusion. The unusual presentation should be considered in the differential diagnosis of uncommon abdominal symptoms during the course of relapsing polychondritis.