Velocity vector comparison between vector flow imaging and computational fluid dynamics in the carotid bifurcation.

It has been largely documented that local hemodynamic conditions, characterized by low and oscillating wall shear stresses, play a key role in the initiation and progression of vascular atherosclerotic lesions. Thus, investigation of the flow field in the carotid bifurcation can lead to early identification of vulnerable plaques. In this scenario, the development of novel non-invasive imaging tools that can be used in routine clinical practice to identify disturbed and recirculating blood flow becomes crucial. In this context, Vector Flow Imaging is becoming a relevant tool as it provides an angle independent assessment of blood flow velocity and multidimensional flow vector visualization. The purpose of the present study was to validate, in several locations of the carotid bifurcation, the high-frame rate vector flow imaging (HiFR-VFI) technique by comparing with computational fluid dynamic simulations (CFD). In all eight carotid bifurcations, HiFR-VFI accurately detected regions of laminar flow as well as recirculation and unsteady flow areas. An accurate and statistically significant agreement was observed between velocity vectors obtained by HiFR-VFI and those computed by CFD, both for vector magnitude (R = 0.85) and direction (R = 0.74). Our study demonstrated that HiFR-VFI is a valid technique for rapid and advanced visual representation of velocity field in large arteries. Thus, it has a great potential in research-based clinical practice for the identification of flow recirculation, low and oscillating velocity gradients near vessel wall. The use of HiFR-VFI may provide a great improvement in the investigation of the role of local hemodynamics in vascular pathologies, as well in the assessment of the effect of pharmacological treatments.

Reported and Unreported Potentially Important Incidental Findings in Urgent Nonenhanced Abdominal CT for Renal Colic.

OBJECTIVE: The aim of the study was to retrospectively evaluate the prevalence of reported and unreported potentially important incidental findings (PIFs) in consecutive nonenhanced abdominal CTs performed specifically for renal colic in the urgent setting. METHODS: One radiologist, blinded to the finalized report, retrospectively re-evaluated nonenhanced abdominal CTs performed from January to December 2017 on adult patients from the emergency department with the specific request of urgent evaluation for renal colic, searching for PIFs. RESULTS: The CTs of 312 patients were included in the study. Thirty-eight findings were reported in 38 different CTs, whereas the re-evaluation added 47 unreported findings in 47 different CTs, adding to total of 85 findings (27%). The difference in the proportion of reported and unreported PIFs between the original report and re-evaluation was significant (p < 0.001). No significant difference was found between the age of patients with and without reported findings. The proportion of potentially important findings did not vary significantly among the 3 shifts in the original report and in re-evaluation. The most frequent findings, both reported and unreported, were pleural effusion, lymphadenopathies, and liver nodules. CONCLUSIONS: Potentially important additional findings are frequently present in urgent nonenhanced abdominal CTs performed for renal colic, and many are not described in the finalized reports. Radiologists should take care not to underreport PIFs even in the urgent setting because of the possible consequences on the patient's health and in order to avoid legal issues, while at the same time satisfying the need for timely and efficient reporting.

Shear wave and strain sonoelastography for the evaluation of the Achilles tendon during isometric contractions.

OBJECTIVES: Changes in mechanical loading as well as pathology can modify the Achilles tendon mechanical properties and therefore detection of these changes is relevant for the diagnosis and management of Achilles tendinopathy. The aim of this study was to evaluate strain and shear wave sonoelastography for their ability to detect changes in the Achilles tendon mechanical properties during a series of isometric contractions. METHODS: Longitudinal sonoelastography images of the Achilles tendon were acquired from 20 healthy participants using four different ultrasound devices; two implementing strain sonoelastography technology (SE1, SE2) and two, shear wave elastography technology (SWE1, SWE2). RESULTS: SE1 measured a decreasing strain ratio (tendon become harder) during the different contraction levels from 1.51 (0.92) to 0.33 (0.16) whereas SE2 mesaured a decreasing strain ratio from 1.08 (0.76) to 0.50 (0.32). SWE1 measured decreasing tendon stiffness during contractions of increasing intensity from 33.40 (19.61) to 16.19 (2.68) whereas SWE2 revealed increasing tendon stiffness between the first two contraction levels from 428.65 (131.5) kPa to 487.9 (121.5) kPa followed by decreasing stiffness for the higher contraction levels from 459.35 (113.48) kPa to 293.5 (91.18) kPa. CONCLUSIONS: Strain elastography used with a reference material was able to detect elasticity changes between the different contraction levels whereas shear wave elastography was less able to detect changes in Achilles tendon stiffness when under load. Inconsistent results between the two technologies should be further investigated.

Multivessel endovascular therapy for undiagnosed vascular type Ehlers-Danlos syndrome. Successful percutaneous transcatheter coil embolization of hepatic artery pseudoaneurysm with stenting of right renal and iliac arteries in emergency setting.

Among Ehlers-Danlos syndromes, the vascular type is the most severe because of its vascular complications. Transcatheter embolization of medium-sized arteries has become the first-line therapy for life-threatening hemorrhage. Ongoing multiple lesions causing hemorrhagic or ischemic complications in the acute phase can challenge patient management. Multivessel endovascular treatment has never been reported. In this study, we report successful single-session treatment by coiling of a ruptured pseudoaneurysm of the hepatic artery with stenting of dissected right renal and iliac arteries in a 46-year-old female. Percutaneous transfemoral approach was gained and sealed with a plug-based closure device. Genetic disease was subsequently confirmed by molecular analysis.

Sonography before and after carpal tunnel release: video article.

Carpal tunnel release for compression of the median nerve at the wrist is a common procedure, often resulting in good clinical outcomes. There are, however, many anatomical variations in and around the carpal tunnel and it is important to be aware of these during carpal tunnel release. After surgery, recurrent carpal tunnel syndrome is uncommon, but difficult to diagnose and treat. Ultrasonography is often necessary for the evaluation of the anatomical variations before carpal tunnel release and to evaluate the most common complications after carpal tunnel release.

Effect of iodinated contrast medium on thyroid function: a study in children undergoing cardiac computed tomography.

BACKGROUND: Few studies, and with conflicting results, have evaluated the potential effects of iodinated contrast media on children's thyroid function. OBJECTIVE: To investigate the effects of iodinated contrast medium on thyroid function in neonates, infants and young children with congenital heart disease undergoing cardiac computed tomography (CT). MATERIALS AND METHODS: We retrospectively evaluated 10 neonates (group 1) and 23 infants and young children (group 2) without thyroid or renal disease for serum levels of thyroid-stimulating hormone, free triiodothyronine and free thyroxine before contrast-enhanced cardiac CT, 48 h after CT and at discharge from the hospital. Cardiac CT was performed with intravenous administration of 1.14±0.17 mL/kg of body weight of iopromide (containing 370 mg of iodine/mL). RESULTS: Group 1 had a reduction of thyroid-stimulating hormone from baseline to 48 h post injection (P=0.002). Group 2 had a reduction of thyroid-stimulating hormone median levels from baseline to 48 h post injection and an increase from 48 h to discharge (P=0.0005 and P=0.0001, respectively). CONCLUSION: Intravenous iodinated contrast medium in children with congenital heart disease caused transient thyroid-stimulating hormone decrease 48 h after CT, with thyroid-stimulating hormone returning to normal range at discharge.

Percutaneous Transanastomotic Stent Graft Deployment to Salvage Dysfunctional Native Forearm Radiocephalic Fistulae: Feasibility and Primary Patency at 12 Months.

PURPOSE: To evaluate feasibility and efficacy of transanastomotic self-expandable polytetrafluoroethylene stent graft placement for salvage of radiocephalic arteriovenous fistulae (RCAVFs). MATERIALS AND METHODS: From 2008 to 2016, 26 patients (21 male; age, 38-80 y) with dysfunctional RCAVFs for juxtaanastomotic lesions that were unresponsive to angioplasty underwent transanastomotic stent graft placement. Stenotic and thrombotic lesions were included. All were deemed unsuitable for surgical revision. Patency rates were calculated per Kaplan-Meier method. A Cox analysis was used to identify influencing factors. RESULTS: Thirty-two stent grafts (6 patients had 2 stents) were deployed. Anatomic and clinical success were achieved in all patients; no major complications occurred. Mechanical and/or pharmacologic thrombolysis was performed in 6 cases before stent graft deployment. During follow-up (median, 34.7 mo; range, 1.9-102.7 mo), 17 repeat interventions were required in 10 patients (43 procedures overall), for an endovascular intervention rate of 0.27 per year. At 3, 6, 12, and 24 months, primary patency (PP) rates were 96% ± 4 (95% CI, 75%-99%), 83% ± 7 (95% CI, 61%-93%), 78% ± 8 (95% CI, 55%-90%), and 69% ± 10 (95% CI, 46%-84%). The corresponding assisted PP rates were 96% ± 4 (95% CI, 76%-99%), 96% ± 4 (95% CI, 76%-99%), 92% ± 5 (95% CI, 71%-98%), and 82% ± 8 (95% CI, 60%-93%). Five AVFs were ultimately abandoned. Per Cox analysis, arterial diameter ≥ 4 mm was associated with better PP (P = .032). CONCLUSIONS: Transanastomotic stent graft placement for RCAVF salvage is feasible and safe, providing patency rates comparable with historical endovascular and surgical data. Its role should be evaluated in larger studies.

High-Frame Rate Vector Flow Imaging of the Carotid Bifurcation in Healthy Adults: Comparison With Color Doppler Imaging.

OBJECTIVES: To evaluate the carotid bifurcation in healthy adults using a commercial system equipped with high-frame rate vector flow imaging (VFI) based on the plane wave and to compare VFI with color Doppler imaging. METHODS: Carotid bifurcation diameters and flow characteristics of 60 vessels in 60 healthy volunteers were evaluated quantitatively and qualitatively to assess complex flow patterns and their extension and duration. RESULTS: Complex flow in the internal carotid artery (ICA) was associated with a statistically significant difference in the ΔICA sinus-to-common carotid artery (CCA) diameter ratio (the relative change in diameter between the CCA and ICA sinus.) Vector flow imaging and color Doppler imaging were in accordance when detecting complex flow in 96.7% of cases; in 3.3% of cases, only VFI identified small recirculation areas of short duration. Vector flow imaging highlighted a larger extension of the complex flow (mean ± SD, 47.7 ± 28.5 mm2 ; median, 45.5 mm2 ) compared with color Doppler imaging (mean, 29.2 ± 19.9 mm2 ; median, 29.5 mm2 ) and better depicted different complex flow patterns; a strong correlation (r = 0.84) was found between the ΔICA sinus-to-CCA diameter ratio and the complex flow extension. Vector flow imaging showed a longer duration of the flow disturbances (mean, 380 ± 218 milliseconds; median, 352.5 milliseconds) compared with color Doppler imaging (mean, 325 ± 206 milliseconds; median, 333 milliseconds), and there was a strong correlation (r = 0.92). CONCLUSIONS: Vector flow imaging is as effective as color Doppler imaging in the detection of flow disturbances, but it is more powerful in the assessment of complex flow patterns.

Under-dilated TIPS Associate With Efficacy and Reduced Encephalopathy in a Prospective, Non-randomized Study of Patients With Cirrhosis.

BACKGROUND & AIMS: Portosystemic encephalopathy (PSE) is a major complication of trans-jugular intrahepatic porto-systemic shunt (TIPS) placement. Most devices are self-expandable polytetrafluoroethylene-covered stent grafts (PTFE-SGs) that are dilated to their nominal diameter (8 or 10 mm). We investigated whether PTFE-SGs dilated to a smaller caliber (under-dilated TIPS) reduce PSE yet maintain clinical and hemodynamic efficacy. We also studied whether under-dilated TIPS self-expand to nominal diameter over time. METHODS: We performed a prospective, non-randomized study of 42 unselected patients with cirrhosis who received under-dilated TIPS (7 and 6 mm) and 53 patients who received PTFE-SGs of 8 mm or more (controls) at referral centers in Italy. After completion of this study, dilation to 6 mm became the standard and 47 patients were included in a validation study. All patients were followed for 6 months; Doppler ultrasonography was performed 2 weeks and 3 months after TIPS placement and every 6 months thereafter. Stability of PTFE-SG diameter was evaluated by computed tomography analysis of 226 patients with cirrhosis whose stent grafts increased to 6, 7, 8, 9, or 10 mm. The primary outcomes were incidence of at least 1 episode of PSE grade 2 or higher during follow up, incidence of recurrent variceal hemorrhage or ascites, incidence of shunt dysfunction requiring TIPS recanalization, and reduction in porto-caval pressure gradient. RESULTS: PSE developed in a significantly lower proportion of patients with under-dilated TIPS (27%) than controls (54%) during the first year after the procedure (P = .015), but the proportions of patients with recurrent variceal hemorrhage or ascites did not differ significantly between groups. No TIPS occlusions were observed. These results were confirmed in the validation cohort. In an analysis of self-expansion of stent grafts, during a mean follow-up period of 252 days after placement, none of the PTFE-SGs self-expanded to the nominal diameter in hemodynamically relevant sites (such as portal and hepatic vein vascular walls). CONCLUSIONS: In prospective, non-randomized study of patients with cirrhosis, we found under-dilation of PTFE-SGs during TIPS placement to be feasible, associated with lower rates of PSE, and effective.

Median nerve evaluation by shear wave elastosonography: impact of "bone-proximity" hardening artifacts and inter-observer agreement.

PURPOSE: Peripheral nerves frequently travel close to the bone surface and are, therefore, prone to elastosonographic "bone-proximity" hardening artifacts. The impact of these artifacts on quantitative measurements of median nerve stiffness performed by shear wave elastosonography has not been explored. Our aim was to assess normal median nerve stiffness values at various locations. MATERIALS AND METHODS: Thirty-six healthy volunteers (24 women and 12 men) aged between 25 and 40 years were evaluated. Two operators performed the evaluation: one expert (6 years of ultrasound experience) and one inexperienced operator (6 months' experience). The nerve was sampled in cross-section at three different locations: mid-forearm, immediately before the carpal tunnel and within the tunnel. The ultrasound scanner was equipped with a 14-MHz linear probe. The Shear Wave module was activated in one-shot mode. Measurements were performed using a ROI corresponding to the diameter of the nerve. RESULTS: The mean values of stiffness of the medial nerve were 32.26 kPa ± 18.60 within the carpal tunnel, 22.20 kPa ± 9.84 at the carpal tunnel inlet and 7.62 kPa ± 7.38 in the forearm. Inter-observer agreement assessed using the intraclass correlation coefficient (ICC) was "moderate" within the carpal tunnel (ICC = 0.44), "moderate" at the carpal tunnel inlet (ICC = 0.41) and "fair" in the forearm (ICC = 0.38). CONCLUSIONS: The stiffness of the median nerve progressively increases in its distal portions, where the nerve approaches the bone surface. Inter-observer agreement was generally good (from fair to moderate).

Vector flow imaging techniques: An innovative ultrasonographic technique for the study of blood flow.

Doppler ultrasonography is routinely used to identify abnormal blood flow. Nevertheless, conventional Doppler can be used to determine only the axial component of blood flow velocity and is angle dependent. A new method of multidimensional angle-independent estimation of flow velocity, called Vector Flow Imaging (VFI), has been proposed. It quantitatively evaluates the true velocity vector's amplitude and direction at any location into a vessel and displays a more intuitive depiction of the flow movements. High frame rate VFI, based on plane wave imaging, allows a detailed dynamic visualization of complex flow by showing even transient events, otherwise undetectable. © 2017 Wiley Periodicals, Inc. J Clin Ultrasound 45:582-588, 2017.

Influence of subjects' characteristics and technical variables on muscle stiffness measured by shear wave elastosonography.

PURPOSE: The aim of this study is to quantitatively assess lower limbs muscle elasticity in a court of healthy subjects and to evaluate the influence of technical variables (e.g., diameter of the ROI-region of interest) and examined subjects' characteristics (e.g., sex, levels of physical activity, side evaluated) on muscle stiffness. MATERIALS AND METHODS: 54 healthy subjects (48 men, 6 women) were evaluated for a total of 108 lower limbs. Shear wave elastography was performed with a multifrequency linear probe (15-4 MHz). Two radiologists performed the evaluation of lower limbs from left to right side (first calf and then thigh). The measures were taken on gastrocnemius and on femoral biceps muscle belly. We chose to place for this study two ROIs of 4 and 2 mm of diameter. RESULTS: The mean muscle stiffness was 1.98 ± 0.48 (range between 1.89 ± 0.36 and 2.15 ± 0.57 m/s). The difference in muscle stiffness between left and right side of the body and between different levels of physical activity never became statistically significant (p value between 0.314 and 0.915). Only in one test out of eight the difference of muscle stiffness between male and female resulted statistically significant (p value 0.020). When comparing the measurement obtained with a 2 and 4 mm diameter ROIs the values were statistically different only for the left thigh (p value 0.028). CONCLUSION: Our study, despite its limitations (low sample and low female population), seems to give some clear advice: physiological or technical factors do not determine statistically significant differences on passive muscle stiffness.

Ultrasound Vector Flow Imaging - could be a new tool in evaluation of arteriovenous fistulas for hemodialysis?

INTRODUCTION: We report the use of a new ultrasound technique to evaluate the axial and lateral components of a complex flow in the arteriovenous fistula (AVF). Vector Flow Imaging (VFI) allows to identify different components of the flow in every direction, even orthogonal to the flow streamline, represented by many single vectors. VFI could help to identify flow alterations in AVF, probably responsible for its malfunction. METHODS: From February to June 2016, 14 consecutive patients with upper-limb AVF were examined with a Resona 7 (Mindray, Shenzhen, China) ultrasound scanner equipped with VFI. An analysis of mean velocity, angular direction and mean number of vectors impacting the vessel wall was carried out. We also identified main flow patterns present in the arterial side, into the venous aneurysm and in correspondence of significant stenosis. RESULTS: A disturbed flow with the presence of vectors directed against the vessel walls was found in 9/14 patients (64.28%): in correspondence of the iuxta-anastomotic venous side (4/9; 44.4%), into the venous aneurysmal tracts (3/9; 33.3%) and in concomitance of stenosis (2/9; 22.2%). The mean velocity of the vectors was around 20-25 cm/s, except in presence of stenosis, where the velocities were much higher (45-50 cm/s). The vectors directed against the vessel walls presented high angle attack (from 45° to 90°, with a median angular deviation 65°). CONCLUSIONS: VFI was confirmed to be an innovative and intuitive imaging technology to study the flow complexity in the arteriovenous fistulas.

High-frame rate vector flow imaging of the carotid bifurcation.

Carotid artery atherosclerotic disease is still a significant cause of cerebrovascular morbidity and mortality. A new angle-independent technique, measuring and visualizing blood flow velocities in all directions, called vector flow imaging (VFI) is becoming available from several vendors. VFI can provide more intuitive and quantitative imaging of vortex formation, which is not clearly distinguishable in the color Doppler image. VFI, as quantitative method assessing disturbed flow patterns of the carotid bifurcation, has the potential to allow better understanding of the diagnostic value of complex flow and to enhance risk stratification. This pictorial review article will show which new information VFI adds for the knowledge of hemodynamics in comparison to the conventional ultrasound techniques. TEACHING POINTS: • VFI is an angle-independent technique measuring flow velocities in all directions. • This kind of VFI is based on a plane wave multidirectional excitation technique. • VFI allows quantitative assessment of carotid streamlines progression and visualizes vorticity. • VFI does not allow a precise comprehension of streamlines' 3D shape. • VFI allows a better understanding of carotid artery complex flows.

Stent Grafts Provided Superior Primary Patency for Central Venous Stenosis Treatment in Comparison with Angioplasty and Bare Metal Stent: A Retrospective Single Center Study on 70 Hemodialysis Patients.

PURPOSE: To compare patency in dialysis patients following different endovascular treatment of symptomatic central venous stenosis. MATERIALS AND METHODS: A 10-year retrospective evaluation in 70 patients (32 men) dialyzing through vascular access (33, 47%) and tunneled catheters (37, 53%) was made. Three cohorts were compared: angioplasty alone (22), bare metal stent (28), and stent graft (20). Patencies were described with Kaplan-Meier method, and Cox uni- and multivariate models were analyzed to find factors associated. RESULTS: All patients had a favorable anatomical and clinical outcome. Restenosis occurred in 22 (31%) of 70 patients requiring 41 additional interventions; 34 of 70 patients died (median follow-up 19.4 months). Primary patency at 3, 6, 12, and 24 months was 100%, 100%, 100%, and 84% for stent graft versus 90%, 79%, 58%, and 43% for angioplasty (P = .014) versus 84%, 80%, 75%, and 46% for bare-metal stent (P = .062). The overall comparison was more favorable for stent graft (P = .020) when the sites of lesions were matched. Patencies for angioplasty and bare-metal stents were equivalent (P = .141). A lower risk of restenosis (hazard rate [HR] 0.20, confidence interval [CI] 0.06-0.7) and fewer reinterventions (P < .01) were associated with stent graft, whereas age (HR 1.04, CI 1.001-1.08) and cardiovascular disease (HR 2.26, CI 1.06-4.84) influenced the overall survival. No difference in assisted primary patency was found. CONCLUSION: Stent graft seems to improve primary patency for central venous stenosis and requires fewer reinterventions in a dialysis population with a high prevalence of long-term catheters.

Dealing with stuck hemodialysis catheter: state of the art and tips for the nephrologist.

The term stuck catheter refers to the condition in which a catheter is not removable from a central vein using standard techniques. Although it is a rare complication, in the last few years it has been reported ever more frequently in hemodialysis due to the widespread use of tunneled catheters. Poor knowledge of the correct procedures and limited experience and training of the specialist in facing this problem are the main reasons for catheter internalization. Stuck catheter is often diagnosed by the nephrologist, who should be competent enough to manage this clinical complication. Among the many options for removing a stuck catheter from the fibrin sleeve, an interventional radiology approach, mainly with endoluminal balloon dilatation, probably provides the best solution. Vascular surgery should be reserved to selected cases in which percutaneous techniques have failed. Nephrologists must play a central role in organizing the treatment of this complication with other specialists in order to avoid making mistakes that may preclude future positive results.

Dialysis catheter-related superior vena cava syndrome with patent vena cava: long term efficacy of unilateral Viatorr stent-graft avoiding catheter manipulation.

Central venous catheters are the most frequent causes of benign central vein stenosis. We report the case of a 79-year-old woman on hemodialysis through a twin catheter in the right internal jugular vein, presenting with superior vena cava (SVC) syndrome with patent SVC. The clinically driven endovascular therapy was conducted to treat the venous syndrome with a unilateral left brachiocephalic stent-graft without manipulation of the well-functioning catheter. The follow-up was uneventful until death 94 months later.

A refinement of Hong's technique for the removal of stuck dialysis catheters: an easy solution to a complex problem.

AIM: A long-term tunneled hemodialysis catheter can be difficult or impossible to pull out if a fibrin sleeve has attached it to the venous wall. We report the outcome of a refinement of Hong's technique for removing incarcerated catheters aimed at improving its feasibility and safety. METHODS: We applied a modification of Hong's technique in four patients (two males, age ranging from 51 to 68 years) with jugular twin hemodialysis catheters (five of eight lines incarcerated). Hong pioneered the technique of endoballooning to expand a stuck central venous catheter, thus freeing it from adhesions. In our technical refinement, we cut the catheter close to its venous entry point in order to facilitate pullout and inserted a valved introducer as access for guide wires as well as for inflations of the catheter balloon. A stiff guide wire was placed in the inferior vena cava to avoid potential damage to heart cavities. Dilation was monitored under fluoroscopy with constrictions showing points where the catheter was incarcerated. If adhesions persisted through the same introducer, endoluminal dilations were repeated with a larger diameter balloon until the catheter was released. New catheters can be positioned using the stiff guide wire already in place. All removals were carried out under local anesthesia in an angiographic room by interventional radiologists. RESULTS: All catheters were successfully removed without complications. Average fluoroscopy time for removal was 12 minutes. In the case of a Tesio catheter removed after 12 years because of infection, a computed tomography scan 2 months later revealed persistence of a calcified fibrin sleeve in the vessel. CONCLUSIONS: Hong's technique was confirmed to be a simple, safe and highly effective way to remove incarcerated long-term central venous catheters. The refinements we adopted made the procedure more flexible and possibly less prone to complications. By properly using ordinary tools available anywhere, Hong's technique could be considered Columbus' egg in this previously risky field.