Vascular Ultrasound Imaging Research Articles

Novel applications of contrast-enhanced ultrasound imaging in vascular medicine

The use of contrast-enhanced ultrasound (CEUS) for vascular imaging indications has increased dramatically during the last decade. Ultrasound contrast agents are gas-filled microbubbles that are injected into the bloodstream and serve as strict intravascular reflectors of ultrasound waves. Numerous studies have addressed the potential clinical use of CEUS in different vascular fields including the carotid arteries, the abdominal aorta, renal arteries and the kidneys. In this review article we discuss the clinical value of contrast agents in vascular ultrasound by enhancing the vascular lumen, and more important, their role as a tool to deliver high resolution, real-time images of microvascular perfusion. Specifically, CEUS imaging of the carotid artery provides a novel, non-invasive method not only to improve the delineation of the vessel wall, but also for the assessment of the vasa vasorum and the ectopic vascularization of the atherosclerotic plaque (intraplaque neovascularization); probably providing a "window" to risk stratify atherosclerotic lesions and individuals by identifying "vulnerable" plaques prone to rupture causing vascular events. CEUS imaging has also emerged as a novel diagnostic tool in various aortic pathologies and particularly for the detection of endoleaks following endovascular treatment of abdominal aortic aneurysms. It is also a valuable tool for the assessment of the tissue perfusion in native and transplanted kidneys providing information on perfusion deficits of the parenchyma. Furthermore, a real-time CEUS method has recently been developed to assess the skeletal muscle microcirculation which could be used to study patients with peripheral arterial occlusive disease or diabetic microangiopathy. In the future, the use of targeted microbubbles could further enhance and expand the diagnostic capabilities of current vascular ultrasound imaging by detecting specific molecular processes that play a role in the pathophysiology of vascular disease.

Transcutaneous very-high resolution ultrasound for the quantification of carotid arterial intima-media thickness in children – Feasibility and comparison with conventional high resolution vascular ultrasound imaging

ObjectiveTo study the accuracy and feasibility of very-high resolution ultrasound (VHRU, 25–55 MHz) and conventional high resolution ultrasound (HRU, 12 MHz) in the assessment of common carotid intima-media thickness (IMT) in healthy children between 0 and 18 years of life. MethodsIMT was measured with VHRU and HRU in 135 children. Seventeen similar sized porcine arterial specimens were imaged with VHRU and HRU, and the IMT measurements compared to histology. ResultsAdequate imaging was obtained and IMT quantified in all children with 25 and 35 MHz, but the far wall was rarely reached with 55 MHz, even in small children. HRU-IMT was significantly thicker compared with VHRU-IMT in young children (<12 years; HRU: 0.434 ± 0.040 vs. VHRU: 0.341 ± 0.054 mm, N = 66; p < 0.001). No differences between HRU-IMT and VHRU-IMT were found among older children. No differences were found between far and near wall VHRU-IMT. An increase in porcine arterial IMT with decreasing transducer frequency was observed in comparison to histology. HRU-IMT was significantly overestimated compared with VHRU-IMT and histology-IMT in porcine vessels with an IMT within the pediatric range (0.20–0.50 mm). ConclusionVHRU is feasible and more accurate than HRU in quantifying CIMT in young children (<12 years). We recommend using the highest ultrasound transducer frequency applicable to quantify CIMT in the pediatric population.

Nurr1 Haplotypes are Associated with Femoropopliteal Restenosis/Re-occlusion after Percutaneous Transluminal Angioplasty

Restenosis/re-occlusion remains a frequent complication in the first year after percutaneous transluminal angioplasty (PTA). In this study, association of nuclear receptor related 1 protein (Nurr1) haplotypes to the restenosis/re-occlusion rate after femoropopliteal PTA was investigated. Patients (n = 142) with disabling claudication or critical limb ischaemia, who had undergone technically successful femoropopliteal PTA, were prospectively followed up by vascular ultrasound imaging 12 months after the procedure. Nurr1 haplotypes 2 and 3 were associated significantly with the restenosis/re-occlusion rate (adjusted odds ratio 1.6, 95% confidence interval (CI) 1.1–2.3 and 2.0, 1.3–2.8, respectively) on univariate analysis.

Interactive image segmentation for ultrasound vascular imaging

Image segmentation for object to extract data from ultrasound acquired is an essential preprocessing step for the effective diagnosis. Various image segmentation methods have been studied. In this study, interactive image segmentation method by graph cut algorithm is proposed to develop a variety of applications of vascular ultrasound imaging and diagnostics. General imaging and vascular ultrasound imaging segmentation by entering constrain condition such as foreground and background. In the future it will be able to develop new ultrasound diagnostics.

Neurosonographic Monitoring of 105 Spontaneous Cervical Artery Dissections

Conclusions: Changes in the lumen of cervical arteries afflicted with spontaneous cervical artery dissection occur most frequently within the first few months after the dissection, but recanalization may occur up to 1 year later. Early recurrence is reasonably common but involves arteries previously unaffected by dissection. Recurrence of spontaneous cervical artery dissection is strongly associated with a family history of arterial dissection. Summary: It is generally acknowledged spontaneous cervical artery dissection (sCAD) is a highly dynamic process after the initial event. Information on recanalization and recurrence rates in patients with sCAD is limited, however. Although cervical artery mural hematomas are best detected by cervical magnetic resonance imaging (MRI) with T1 fat suppression, vascular ultrasound imaging is the test that is most frequently used to monitor patients with sCAD. In this study, the authors prospectively monitored consecutive patients with MRI-proven sCAD by duplex ultrasound imaging daily in the hospital, monthly for the first 6 months after discharge, and every 6 months thereafter. The authors studied 105 sCADs in 76 patients. The mean follow-up was 58 months (range, 28-96 months). Of the 105 dissections in this study, 61 (58.1%) involved the internal carotid artery and 44 (41.9%) involved the vertebral artery. Four patients had multiple sCADs. Follow-up was available for 74 (103 vessels) of the 76 patients (97.3%). Complete and hemodynamically significant (<50% stenosis) recanalization rates were 51.4% and 20.4%. All but one of the complete recanalizations occurred within the first 9 months after the initial event. Early recurrences (in-hospital recurrence) were common, with a second sCAD occurring in 20 previously unaffected arteries. There were only two late recurrences (2.7%) at a site of a previous sCAD. Six patients had a family history of arterial dissection and all had a sCAD recurrence. Recurrence rate in patients without a family history of arterial dissection was much less, with only 16 arteries (22.8%) affected (P < .001). Comment: There are several interesting points here. First, although recurrence of sCAD is reasonably uncommon, it generally occurs early after the initial event and in a different cervical artery. The authors' early recurrence of 25% is much higher than previously suspected and may relate to the rigorous follow-up protocol in the study. The fact that late sCAD recurrence can happen in previously affected artery suggests recurrence after sCAD in the early and late periods may have different pathologies. Perhaps, as the authors point out, early recurrences are correlated with a transient arterial disorder, such as a vasculitis, while late recurrences may be indicative of underlying persistent connective tissue weakness. The high early recurrence rate suggests that aggressive treatment of sCADs, including control of double product and lowering blood pressure within the constraints imposed by the neurologic pathology, should be implemented.

Assessment of vascular phenotype using a novel very-high-resolution ultrasound technique in adolescents after aortic coarctation repair and/or stent implantation: relationship to central haemodynamics and left ventricular mass

ObjectivesCoarctation of the aorta (CoA) has been associated with abnormal vascular function, increased blood pressure (BP) and premature cardiovascular disease even after a successful intervention. The objective was to determine...

Vascular ultrasound for atherosclerosis imaging.

Cardiovascular disease is a leading cause of death in the Western world. Therefore, detection and quantification of atherosclerotic disease is of paramount importance to monitor treatment and possible prevention of acute events. Vascular ultrasound is an excellent technique to assess the geometry of vessel walls and plaques. The high temporal as well as spatial resolution allows quantification of luminal area and plaque size and volume. While carotid arteries can be imaged non-invasively, scanning of coronary arteries requires invasive intravascular catheters. Both techniques have already demonstrated their clinical applicability. Using linear array technology, detection of disease as well as monitoring of pharmaceutical treatment in carotid arteries are feasible. Data acquired with intravascular ultrasound catheters have proved to be especially beneficial in understanding the development of atherosclerotic disease in coronary arteries. With the introduction of vascular elastography not only the geometry of plaques but also the risk for rupture of plaques might be identified. These so-called vulnerable plaques are frequently not flow-limiting and rupture of these plaques is responsible for the majority of cerebral and cardiac ischaemic events. Intravascular ultrasound elastography studies have demonstrated a high correlation between high strain and vulnerable plaque features, both ex vivo and in vivo. Additionally, pharmaceutical intervention could be monitored using this technique. Non-invasive vascular elastography has recently been developed for carotid applications by using compound scanning. Validation and initial clinical evaluation is currently being performed. Since abundance of vasa vasorum (VV) is correlated with vulnerable plaque development, quantification of VV might be a unique tool to even prevent this from happening. Using ultrasound contrast agents, it has been demonstrated that VV can be identified and quantified. Although far from routine clinical application, non-invasive and intravascular ultrasound VV imaging might pave the road to prevent atherosclerotic disease in an early phase. This paper reviews the conventional vascular ultrasound techniques as well as vascular ultrasound strain and vascular ultrasound VV imaging.

Association between endothelial dysfunction and hyperuricaemia

We used high-resolution peripheral vascular ultrasound imaging to assess endothelial function in hyperuricaemic patients. Hyperuricaemia was defined as a serum uric acid concentration of > 7.7 mg/dl in men or > 6.6 mg/dl in women. Measurements of endothelium-dependent flow-mediated vasodilation (FMD) and endothelium-independent nitroglycerin-mediated vasodilation were performed in 46 hyperuricaemic patients and an equal number of healthy age- and gender-matched normal controls by high-resolution two-dimensional ultrasonographic imaging of the brachial artery. The serum levels of glucose, creatinine, alanine aminotransferase (ALT), lipid profiles and high-sensitivity CRP were measured for both the study groups. The serum uric acid levels averaged 9.24 (1.16) and 6.18 (0.99) mg/dl in the hyperuricaemic and control groups, respectively. Body weight and BMI were significantly higher in the hyperuricaemic group than in the control group. The serum levels of creatinine, ALT, triglyceride and high-sensitivity CRP were significantly different between the two groups. The FMD values were significantly lower in the hyperuricaemic patients than in the controls [4.45% (3.13%) vs 7.10% (2.48%); P < 0.001]. The FMD values were negatively associated with serum uric acid levels (r = -0.273; P = 0.009). Multivariate regression analysis showed that the presence of hyperuricaemia (β = -0.384; P < 0.001) and body weight (β = 0.215; P = 0.017) were independent determinants of low FMD values. Hyperuricaemia is associated with endothelial dysfunction. Decreased nitric oxide bioavailability may be the main reason.

Intima-media thickness evolution after treatment with infliximab in patients with rheumatoid arthritis

Atherosclerosis is a well known progressive disease that recognizes risk factors such as diabetes, hypertension, smoking, dyslipidemia, and inflammation. Mechanisms underlying atherosclerotic processes during inflammation are not completely understood, but cytokines are also involved, in particular tumor necrosis factor-alpha (TNF-alpha). Chronic inflammatory diseases such as rheumatoid arthritis (RA) are commonly associated with atherosclerotic complication. Little is known about the role of treatment of chronic inflammatory disease on the evolution of atherosclerosis in this kind of disease. Usually, evolution of atherosclerosis is monitored by intima-media thickness and the presence of plaques on several arteries such as common carotid. The aim of the study was to monitor atherosclerosis evolution in seven RA patients on common treatment with infliximab (an anti-TNF-alpha drug) compared with seven RA patients during common treatment but not treated with infliximab. We selected 14 patients with RA according to the American College of Rheumatology classification criteria. Seven patients were selected before and after common treatment for RA based on nonsteroidal anti-inflammatory drugs (NSAIDs), methotrexate, and steroids (12 months), and seven patients before and after treatment based on infliximab associated with NSAIDs, methotrexate, and steroids (12 months). Ultrasound vascular imaging was performed to screen intima-media thickness and the presence of atherosclerotic plaques on common carotid artery and identify evolution of atherosclerosis. After 12 months, patients that were treated with infliximab showed significant worsening of atherosclerosis with an increase of intima-media thickness and the presence of further atherosclerotic plaques compared to patients that were treated traditionally and showed a nonsignificant increase of the same parameters. Treatment based on anti-TNF-alpha such as infliximab shows a worsening evolution of atherosclerosis based on our data. If these data are associated with a poor clinical outcome such as atherothrombosis of cerebral vessels and/or coronary vessels, this should be evaluated by further studies.

Vascular Ultrasound Imaging of Axillary Artery Thrombosis in a Neonate

This case report presents a 4-day-old neonate with axillary artery thrombosis born to a diabetic mother. After receiving an angiogram and blood workup, the neonate then received an ultrasound. The angiogram, as well as the ultrasound, revealed left axillary artery thrombus. The neonate received low molecular weight heparin treatment and was closely monitored over the course of the hospitalization. Because of the rarity of neonatal axillary arterial thrombosis, the condition is sporadically reported in literature. Causes of this condition have been attributed to sepsis, congestive heart failure, trauma, coagulation disorders, polycythemia, and dehydration. It is documented that a clot can form in the renal vein, inferior vena cava, ductus arteriosus, or umbilical vessels and travel to an upper extremity artery. Treatments include clinical observation, systemic anticoagulation, surgical thrombectomy, or intraoperative balloon angioplasty. This case demonstrates the ability of ultrasound to diagnose and follow upper extremity arterial thrombus in neonates.

Role of Ultrasound Vascular Imaging in the Acute Phase of Stroke

Role of Ultrasound Vascular Imaging in the Acute Phase of Stroke

Educational challenges in vascular surgery: An Australasian response

In Australia and New Zealand, training requirements in vascular surgery have substantially changed since 2002. Training in general surgery is no longer required. Trainees in vascular surgery need to be competent in open vascular surgery and in performing and interpreting vascular ultrasound imaging. They must also master a full range of endovascular procedures, including cannulation of arteries, and angioplasty and stenting procedures, and endoluminal repair of aneurysms with stent grafting. Applicants complete a rigorous selection process and are ranked nationally. Training is started in postgraduate year 3 or at any time beyond that. The 5-year program is the competency-based surgical education training (SET) program. The trainees sit an examination at the end of the SET 1 and also an exit examination in SET 5. Before the final examination, the trainees must have performed 400 major cases as primary operators and 150 peripheral percutaneous interventions. In addition they must satisfy the requirements of the on-line in-service examinations and show adequate ultrasound case volumes and completion of research projects.

Role of Ultrasound Vascular Imaging in the Acute Phase of Stroke

Role of Ultrasound Vascular Imaging in the Acute Phase of Stroke

Abstract 3157: Depletion of Circulating Endothelial Progenitor Cells and Endothelial Dysfunction in Subjects with Depressive Symptoms

Introduction: Although the mechanisms remain unclear, depression is associated with endothelial dysfunction and increases risk of cardiovascular disease (CVD). Recent studies suggest that circulating endothelial progenitor cells (EPC) play an important role in endothelial repair and correlate with endothelial function. Hypothesis: We assessed the hypothesis that the presence of depressive symptoms in subjects without significant CVD is associated with depletion of circulating EPC and impaired endothelial function. Methods: We studied the relationship between the level of circulating EPCs, endothelial function and depression status in 129 healthy normal individuals (54±10 yrs, 54 men) without prior CVD or diabetes. The numbers of circulating CD34/KDR + EPCs were determined by flow cytometry, and the depression status was estimated by Depression Anxiety Stress Scales. Brachial artery flow-mediated dilation (FMD) was measured by high-resolution vascular ultrasound imaging. Results: The median depression score of the study population was 4 (range 0 to 34), and 41 subjects (32 %) had high depression score (DS) ≥8 (defined by ≥ the 75th percentile of the depression score). There were no significant differences in baseline clinical characteristics between subjects with or without high DS (all P &gt; 0.05 ). However, subjects with high DS had significantly lower FMD (5.4±2.7 vs. 8.0±4.0 %, P &lt; 0.001 ) and CD34/KDR + EPC% (1.24±1.27 vs. 2.02±2.43 %, P = 0.037 ) than those with normal DS. Multivariate regression analysis revealed that a high DS (OR 1.08, 95%CI: 1.02–1.15, P = 0.009 ) and old age (OR 1.05, 95%CI: 1.01–1.09, P = 0.029 ) were independent predictors for decreased FMD. Conclusions: The results of this study demonstrated that in subjects without significant CVD, the presence of a high DS was associated with impaired brachial FMD and depletion of circulating EPC. Nevertheless, only depression score, but not the percentage of circulating EPC significantly correlated brachial FMD, and was an independent predictor for impaired brachial FMD.

Ultrasound imaging techniques for the evaluation of cardiovascular therapies

Cardiovascular disease remains a substantial cause of morbidity and mortality in the developed world, and is becoming an increasingly important cause of death in developing countries too. While current cardiovascular treatments can help to reduce this disease burden, a substantial number of patients still retain a high risk of experiencing a life-threatening cardiovascular event. Thus, the development of new therapies capable of reducing this residual risk remains an important healthcare objective. The time taken to bring new therapies to the patient in need is lengthened by the unavoidable requirement to demonstrate a statistically significant benefit in terms of clinical events beyond that achievable with current treatments. However, clinical trials utilizing surrogate endpoints-biomarkers of disease progression that manifest before potentially fatal cardiovascular events occur-have the potential to enhance the process of drug development by enabling a statistically sound assessment of the efficacy of new therapies several years in advance of the availability of data from clinical endpoint trials. Two vascular ultrasound imaging techniques, measurement of carotid intima-media thickness (CIMT) and intravascular ultrasound (IVUS) of the coronary arteries, are increasingly being used to assess novel cardiovascular therapies in surrogate endpoint trials forming integral components of larger trial programmes utilizing both surrogate and clinical endpoints. The rationale for the use of CIMT- and IVUS-based surrogates, with supporting evidence from historical and recent trials, is presented in this review article.

Usefulness of High-Frequency Vascular Ultrasound Imaging and Serum Inflammatory Markers to Predict Plaque Rupture in Patients With Stable and Unstable Angina Pectoris

It remains unclear what kind of morphologic and biochemical features best predict plaque rupture in patients with angina pectoris (AP). This study aimed to investigate whether combined high-frequency vascular ultrasound imaging and measurements of serum inflammatory biomarkers can predict coronary plaque ruptures in patients with AP. The study population consisted of 20 patients with stable AP and 40 patients with unstable AP. High-frequency vascular ultrasound imaging was performed in the 2 groups to measure intima-media thickness, the plaque acoustic density of the common carotid arteries, and the flow-mediated dilation of the brachial arteries. Serum lipid profile and inflammatory biomarkers were measured in all patients. Using intravascular ultrasound, a list of coronary imaging parameters was obtained. A multivariate logistic regression model was applied to calculate the odds ratio of each parameter to predict coronary plaque ruptures detected by intravascular ultrasound. Of 139 coronary artery plaques identified by intravascular ultrasound, 48 plaques (9 in stable AP and 39 in unstable AP) developed ruptures. Among measured parameters, the values of carotid intima-media thickness, coronary external elastic membrane area, plaque area, plaque burden, plaque eccentric index and remodeling index, serum high-sensitivity C-reactive protein, soluble intercellular adhesion molecule-1, and soluble vascular cell adhesion molecule-1 were significantly higher in unstable AP than in stable AP (p <0.05 to 0.01). Of these parameters, carotid intima-media thickness, serum high-sensitivity C-reactive protein, and the coronary remodeling index were found to be significant predictors of coronary plaque rupture, with odds ratios of 9.51 (95% confidence interval 1.29 to 21.81), 3.02 (95% confidence interval 1.01 to 7.65), and 0.01 (95% confidence interval 0.00 to 0.34), respectively. In conclusion, combined high-frequency ultrasound imaging of coronary and carotid arteries and measurements of serum inflammatory markers are able to predict coronary plaque ruptures in patients with AP.

A Modular Software System to Assist Interpretation of Medical Images—Application to Vascular Ultrasound Images

Improvements in medical imaging technology have greatly contributed to early disease detection and diagnosis. However, the accuracy of an examination depends on both the quality of the images and the ability of the physician to interpret those images. Use of output from computerized analysis of an image may facilitate the diagnostic tasks and, potentially improve the overall interpretation of images and the subsequent patient care. In this paper, Analysis, a modular software system designed to assist interpretation of medical images, is described in detail. Analysis allows texture and motion estimation of selected regions of interest (ROIs). Texture features can be estimated using first-order statistics, second-order statistics, Laws' texture energy, neighborhood gray-tone difference matrix, gray level difference statistics, and the fractal dimension. Motion can be estimated from temporal image sequences using block matching or optical flow. Image preprocessing, manual and automatic definition of ROIs, and dimensionality reduction and clustering using fuzzy c-means, are also possible within Analysis. An important feature of Analysis is the possibility for online telecollaboration between health care professionals under a secure framework. To demonstrate the applicability and usefulness of the system in clinical practice, Analysis was applied to B-mode ultrasound images of the carotid artery. Diagnostic tasks included automatic segmentation of the arterial wall in transverse sections, selection of wall and plaque ROIs in longitudinal sections, estimation of texture features in different image areas, motion analysis of tissue ROIs, and clustering of the extracted features. It is concluded that Analysis can provide a useful platform for computerized analysis of medical images and support of diagnosis

Vascular ultrasound imaging to study immediate postcatheterization vascular complications in children

Vascular occlusion is the major complication of percutaneous cardiac catheterization in children. This is a prospective study to evaluate post catheterization vascular complications in 120 consecutive children with the help of vascular ultrasound and Doppler imaging. Ultrasound imaging of both iliac and femoral veins and arteries was done one hour prior and 24 hours after cardiac catheterization. Patients with prior thrombus or occlusion of femoral/iliac vein or artery due to previous cardiac catheterization were excluded from the study. Age of the patients ranged from 22 days to 12 years with a mean of 56 months and weight ranged from 3 to 57 kg with a mean of 14.3 kg. Procedure time was less than 60 minutes in 74 patients (61.66%) and more than 60 minutes in 46 patients (38.33%). 4F sized arterial sheath was used in 108 patients. 5F or bigger sized arterial sheath was used in remaining 12 patients. Incidence of arterial occlusion was higher in patients weighing less than 10 kg (16%) as compared with patients weighing more than 10 kg (5.5%) {P = 0.031}. Arterial thrombosis was more in infants (16%) as compared with older children (7%) {P = 0.203} Prolonged procedure time or use of larger sized sheath did not have higher incidence of arterial occlusion. Venous thrombosis was found in 2 patients (1.66%) who had 5F venous sheath. One patient had arterio venous fistula. Our study shows vascular ultrasound imaging can provide anatomical details of femoral and iliac vessels and is a easier and accurate method of assessing post-catheterization vascular complications in children.

Guidelines for Noninvasive Vascular Laboratory Testing: A Report from the American Society of Echocardiography and the Society of Vascular Medicine and Biology

Accompanying the rapid growth of interest inpercutaneous vascular interventions, there hasbeen increasing interest among cardiologists inperforming noninvasive vascular testing using ul-trasound. In an attempt to provide recommenda-tions on the best practices in vascular laboratorytesting, this report has been prepared by a writinggroup from the American Society of Echocardiog-raphy (ASE) and the Society of Vascular Medicineand Biology. The document summarizes principlesintegral to vascular duplex ultrasound–includingcolor Doppler, spectral Doppler waveform analy-sis, power Doppler, and the use of contrast.Appropriate indications and interpretation of ca-rotid artery, renal artery, abdominal aorta, andperipheral artery ultrasound imaging are de-scribed. A dedicated section summarizes noninva-sive techniques for physiologic vascular testing ofthe lower extremity arteries–including measure-ment of segmental pressures and pulse volumeplethysmography. The use of exercise testing inthe evaluation of peripheral artery disease, ultra-sound evaluation of the lower extremities afterpercutaneous revascularization, and the diagnosisand management of iatrogenic pseudoaneurysm(PSA) is also discussed. A section on the importanttopic of vascular laboratory accreditation is in-cluded. Finally, additional details regarding propertechnique for performance of the various vasculartests and procedures are included in the Appen-dix.

Ultrasound-guided arterial cannulation in infants improves success rate

In small children, the placement of arterial catheters can be technically challenging for even the most experienced anaesthetist. We investigated whether ultrasound imaging would improve the success rate and reduce time demand and complications of radial artery cannulation. In this prospective randomized study, we performed radial artery cannulation in 30 small children (age 40 +/- 33 months) using two different techniques for localization of the vessel. In Group 1 (n = 15), the traditional palpation method was used, while in Group 2 (n = 15) cannulation was directed by vascular ultrasound imaging. In addition, we used ultrasound to determine the cross-sectional area of the radial artery with and without dorsiflexion. For statistical analysis, the non-parametric U-test for non-paired data and the Wilcoxon signed rank sum test for paired data were used. Differences were considered significant, when P < 0.05. Ultrasound-guided puncture was successful in all children of Group 2 compared to only 12 of 15 (80%) children in Group 1. Fewer attempts with the imaging technique were required than with the traditional technique (20 vs. 34, P < 0.05). Dorsiflexion significantly reduced the mean cross-sectional area of the artery by 19%. The current pilot study suggests that ultrasound guidance is appropriate for radial artery catheter insertion, sharing many of the benefits of ultrasound-guided central vein catheter insertion.