The Calculation and Evaluation of an Ultrasound-Estimated Fat Fraction in Non-Alcoholic Fatty Liver Disease and Metabolic-Associated Fatty Liver Disease

We aimed to develop a non-linear regression model that could predict the fat fraction of the liver (UEFF), similar to magnetic resonance imaging proton density fat fraction (MRI-PDFF), based on quantitative ultrasound (QUS) parameters. We measured and retrospectively collected the ultrasound attenuation coefficient (AC), backscatter-distribution coefficient (BSC-D), and liver stiffness (LS) using shear wave elastography (SWE) in 90 patients with clinically suspected non-alcoholic fatty liver disease (NAFLD), and 51 patients with clinically suspected metabolic-associated fatty liver disease (MAFLD). The MRI-PDFF was also measured in all patients within a month of the ultrasound scan. In the linear regression analysis, only AC and BSC-D showed a significant association with MRI-PDFF. Therefore, we developed prediction models using non-linear least squares analysis to estimate MRI-PDFF based on the AC and BSC-D parameters. We fitted the models on the NAFLD dataset and evaluated their performance in three-fold cross-validation repeated five times. We decided to use the model based on both parameters to calculate UEFF. The correlation between UEFF and MRI-PDFF was strong in NAFLD and very strong in MAFLD. According to a receiver operating characteristics (ROC) analysis, UEFF could differentiate between <5% vs. ≥5% and <10% vs. ≥10% MRI-PDFF steatosis with excellent, 0.97 and 0.91 area under the curve (AUC), accuracy in the NAFLD and with AUCs of 0.99 and 0.96 in the MAFLD groups. In conclusion, UEFF calculated from QUS parameters is an accurate method to quantify liver fat fraction and to diagnose ≥5% and ≥10% steatosis in both NAFLD and MAFLD. Therefore, UEFF can be an ideal non-invasive screening tool for patients with NAFLD and MAFLD risk factors.

Preliminary study on individual radiation dose received by medical staff for dose constraint determination

The staff of the Radiation Protection Service of a European clinical center measured the radiation dose by type-tested thermoluminescent dosemeter systems to which the medical staff was exposed, to assess the effectiveness of current procedures and equipment for optimalisation prompted by the requirements EU Basic Safety Standard 2013. There were three participating sites, the Site 1 was an external hospital, whereas Sites 2 and 3 are part of the same clinical center, who provided data regarding their personnel, from technologists, nurses and medical doctors. In this preliminary study, only a low number of cases were available and used to establish a new, more realistic yearly dose constraint, namely 6 (from two) mSv for whole-body effective dose, 15 (from two) mSv for eye lens dose and 300 (from 50) mSv for extremity dose. Furthermore, the state of safety culture and protection equipment was assessed. Collection of the sufficient amount of data for statistical evaluation is ongoing.

Artificial intelligence and neural networks in radiology – Basics that all radiology residents should know

The area of Artificial Intelligence is developing at a high rate. In the medical field, an extreme amount of data is created every day. As the images and the reports are quantifiable, the field of radiology aspires to deliver better, more efficient clinical care. Artificial intelligence (AI) means the simulation of human intelligence by a system or machine. It has been developed to enable machines to “think”, which means to be able to learn, reason, predict, categorize, and solve problems concerning high amounts of data and make decisions in a more effective manner than before. Different AI methods can help radiologists with pre-screening images and identifying features. In this review, we summarize the basic concepts which are needed to understand AI. As the AI methods are expected to exceed the threshold for clinical usefulness soon, in the near future it will be inevitable to use AI in medicine.

Splenic hamartoma in a patient with peripancreatic arterial arcades: A case report

Splenic hamartoma is a rare benign vascular lesion of the spleen. A splenic mass was incidentally detected in an asymptomatic 65-year-old male during an abdominal ultrasound scan. The workup of the splenic lesion included an abdominal CT angiography (CTA), contrast-enhanced ultrasound (CEUS), and microvascular flow imaging Doppler sonography. The CT scan confirmed that the splenic mass had benign characteristics, and its contrast enhancement was similar to the spleen. The CEUS was able to rule out the possibility of hemangioma. Meanwhile, chronic compression of the celiac trunk and the filling of the splenic artery from collaterals were also detected on CTA. The imaging studies suggested a splenic hamartoma, and the diagnosis was confirmed by the result of a fine needle aspiration biopsy.

Diagnosis of focal liver lesions with deep learning-based multi-channel analysis of hepatocyte-specific contrast-enhanced magnetic resonance imaging

BACKGROUND

The nature of input data is an essential factor when training neural networks. Research concerning magnetic resonance imaging (MRI)-based diagnosis of liver tumors using deep learning has been rapidly advancing. Still, evidence to support the utilization of multi-dimensional and multi-parametric image data is lacking. Due to higher information content, three-dimensional input should presumably result in higher classification precision. Also, the differentiation between focal liver lesions (FLLs) can only be plausible with simultaneous analysis of multi-sequence MRI images.

AIM

To compare diagnostic efficiency of two-dimensional (2D) and three-dimensional (3D)-densely connected convolutional neural networks (DenseNet) for FLLs on multi-sequence MRI.

METHODS

We retrospectively collected T2-weighted, gadoxetate disodium-enhanced arterial phase, portal venous phase, and hepatobiliary phase MRI scans from patients with focal nodular hyperplasia (FNH), hepatocellular carcinomas (HCC) or liver metastases (MET). Our search identified 71 FNH, 69 HCC and 76 MET. After volume registration, the same three most representative axial slices from all sequences were combined into four-channel images to train the 2D-DenseNet264 network. Identical bounding boxes were selected on all scans and stacked into 4D volumes to train the 3D-DenseNet264 model. The test set consisted of 10-10-10 tumors. The performance of the models was compared using area under the receiver operating characteristic curve (AUROC), specificity, sensitivity, positive predictive values (PPV), negative predictive values (NPV), and f1 scores.

RESULTS

The average AUC value of the 2D model (0.98) was slightly higher than that of the 3D model (0.94). Mean PPV, sensitivity, NPV, specificity and f1 scores (0.94, 0.93, 0.97, 0.97, and 0.93) of the 2D model were also superior to metrics of the 3D model (0.84, 0.83, 0.92, 0.92, and 0.83). The classification metrics of FNH were 0.91, 1.00, 1.00, 0.95, and 0.95 using the 2D and 0.90, 0.90, 0.95, 0.95, and 0.90 using the 3D models. The 2D and 3D networks' performance in the diagnosis of HCC were 1.00, 0.80, 0.91, 1.00, and 0.89 and 0.88, 0.70, 0.86, 0.95, and 0.78, respectively; while the evaluation of MET lesions resulted in 0.91, 1.00, 1.00, 0.95, and 0.95 and 0.75, 0.90, 0.94, 0.85, and 0.82 using the 2D and 3D networks, respectively.

CONCLUSION

Both 2D and 3D-DenseNets can differentiate FNH, HCC and MET with good accuracy when trained on hepatocyte-specific contrast-enhanced multi-sequence MRI volumes.

Incidence of and predisposing factors for pseudoaneurysm formation in a high-volume cardiovascular center

Purpose

To evaluate factors associated with pseudoaneurysm (PSA) development.

Methods

Between January 2016 and May 2020, 30,196 patients had invasive vascular radiological or cardiac endovascular procedures that required arterial puncture. All patients with PSA were identified. A matched (age, gender, and type of the procedure) control group of 134 patients was created to reveal predictors of PSA formation.

Results

Single PSAs were found in 134 patients. Fifty-three PSAs developed after radiological procedures (53/6555 [0.8%]), 31 after coronary artery procedures (31/18038 [0.2%]), 25 after non-coronary artery cardiac procedures (25/5603 [0.4%]), and 25 due to procedures in which the arterial puncture was unintended. Thirty-four PSAs (25.4%) were localized to the upper extremity arteries (vascular closure device [VCD], N = 0), while 100 (74.6%) arose from the lower extremity arteries (VCD, N = 37). The PSA prevalence was 0.05% (10/20478) in the radial artery, 0.1% (2/1818) in the ulnar artery, 1.2% (22/1897) in the brachial artery, and 0.4% (99/22202) in the femoral artery. Treatments for upper and lower limb PSAs were as follows: bandage replacement (32.4% and 14%, respectively), ultrasound-guided compression (11.8% and 1%, respectively), ultrasound-guided thrombin injection (38.2% and 78%, respectively), and open surgery (17.6% and 12%, respectively). Reintervention was necessary in 19 patients (14.2%). The prevalence of PSA for the punctured artery with and without VCD use was 37/3555 (1%) and 97/27204 (0.4%), respectively (OR, 2.94; 95% CI, 1.95–4.34; P<0.001). The effect of red blood cell (RBC) count (P<0.001), hematocrit value (P<0.001), hemoglobin value (P<0.001), international normalized ratio (INR; P<0.001), RBC count—INR interaction (P = 0.003), and RBC count—VCD use interaction (P = 0.036) on PSA formation was significant.

Conclusion

Patients in whom the puncture site is closed with a VCD require increased observation. Preprocedural laboratory findings are useful for the identification of patients at high risk of PSA formation.

CT texture analysis of abdominal lesions – Part II: Tumors of the Kidney and Pancreas

It has been proven in a few early studies that radiomic analysis offers a promising opportunity to detect or differentiate between organ lesions based on their unique texture parameters. Recently, the utilization of CT texture analysis (CTTA) has been receiving significant attention, especially for response evaluation and prognostication of different oncological diagnoses. In this review article, we discuss the unique ability of radiomics and its subfield CTTA to diagnose lesions in the pancreas and kidney. We review studies in which CTTA was used for the classification of histology grades in pancreas and kidney tumors. We also review the role of radiogenomics in the prediction of the molecular and genetic subtypes of pancreatic tumors. Furthermore, we provide a short report on recent advancements of radiomic analysis in predicting prognosis and survival of patients with pancreatic and renal cancers.

CT texture analysis of abdominal lesions – Part I.: Liver lesions

Artificial Intelligence and the use of radiomics analysis have been of great interest in the last decade in the field of imaging. CT texture analysis (CTTA) is a new and emerging field in radiomics, which seems promising in the assessment and diagnosis of both focal and diffuse liver lesions. The utilization of CTTA has only been receiving great attention recently, especially for response evaluation and prognostication of different oncological diagnoses. Radiomics, combined with machine learning techniques, offers a promising opportunity to accurately detect or differentiate between focal liver lesions based on their unique texture parameters. In this review article, we discuss the unique ability of radiomics in the diagnostics and prognostication of both focal and diffuse liver lesions. We also provide a brief review of radiogenomics and summarize its potential role of in the non-invasive diagnosis of malignant liver tumors.

Three-dimensional CT texture analysis of anatomic liver segments can differentiate between low-grade and high-grade fibrosis

Background

CT texture analysis (CTTA) has been successfully used to assess tissue heterogeneity in multiple diseases. The purpose of this work is to demonstrate the value of three-dimensional CTTA in the evaluation of diffuse liver disease. We aimed to develop CTTA based prediction models, which can be used for staging of fibrosis in different anatomic liver segments irrespective of variations in scanning parameters.

Methods

We retrospectively collected CT scans of thirty-two chronic hepatitis patients with liver fibrosis. The CT examinations were performed on either a 16- or a 64-slice scanner. Altogether 354 anatomic liver segments were manually highlighted on portal venous phase images, and 1117 three-dimensional texture parameters were calculated from each segment. The segments were divided between groups of low-grade and high-grade fibrosis using shear-wave elastography. The highly-correlated features (Pearson r > 0.95) were filtered out, and the remaining 453 features were normalized and used in a classification with k-means and hierarchical cluster analysis. The segments were split between the train and test sets in equal proportion (analysis I) or based on the scanner type (analysis II) into 64-slice train 16-slice validation cohorts for machine learning classification, and a subset of highly prognostic features was selected with recursive feature elimination.

Results

A classification with k-means and hierarchical cluster analysis divided segments into four main clusters. The average CT density was significantly higher in cluster-4 (110 HU ± SD = 10.1HU) compared to the other clusters (c1: 96.1 HU ± SD = 11.3HU; p < 0.0001; c2: 90.8 HU ± SD = 16.8HU; p < 0.0001; c3: 93.1 HU ± SD = 17.5HU; p < 0.0001); but there was no difference in liver stiffness or scanner type among the clusters. The optimized random forest classifier was able to distinguish between low-grade and high-grade fibrosis with excellent cross-validated accuracy in both the first and second analysis (AUC = 0.90, CI = 0.85–0.95 vs. AUC = 0.88, CI = 0.84–0.91). The final support vector machine model achieved an excellent prediction rate in the second analysis (AUC = 0.91, CI = 0.88–0.94) and an acceptable prediction rate in the first analysis (AUC = 0.76, CI = 0.67–0.84).

Conclusions

In conclusion, CTTA-based models can be successfully applied to differentiate high-grade from low-grade fibrosis irrespective of the imaging platform. Thus, CTTA may be useful in the non-invasive prognostication of patients with chronic liver disease.

Interobserver agreement and diagnostic accuracy of shearwave elastography for the staging of hepatitis C virus-associated liver fibrosis

PURPOSE

Our study aimed to evaluate the technical success rate, interobserver reproducibility, and accuracy of shearwave elastography (SWE) in the staging of hepatitis C virus (HCV)-associated liver fibrosis.

METHODS

A total of 10 healthy controls and 49 patients with chronic liver disease were enrolled prospectively. Two examiners performed point shearwave elastography (pSWE) and two-dimensional shearwave elastography (2D-SWE) measurements with an RS85A ultrasound scanner using the S-Shearwave application (Samsung Medison, Hongcheon, Korea). The performance of S-Shearwave in the staging (METAVIR F0-F4) of liver fibrosis was compared with prior transient elastography (TE) with receiver operating characteristic (ROC) curve analysis.

RESULTS

The interobserver reproducibility was excellent with pSWE (ICC = 0.92, 95% CI: 0.86-0.95, P < .001). A very good agreement was found between pSWE and TE measurements (ICC =0.85, 95% CI: 0.78-0.89, P < .001). The ROC analysis determined the optimal cut-off values of pSWE for the staging of chronic hepatitis C-associated fibrosis (F2, 1.46 m/s; F3, 1.63 m/s; F4, 1.95 m/s). Both observers achieved excellent diagnostic accuracy (AUROC: 94% vs 97%) in the detection of significant (≥F2) liver fibrosis.

CONCLUSION

The interobserver agreement is excellent with S-Shearwave pSWE, and observers can diagnose significant liver fibrosis with a comparable accuracy to TE.

Orthopaedic metallic artefact reduction algorithm facilitates CT evaluation of the urinary tract after hip prosthesis

AIM

To examine the improvement in the visualisation of bladder and ureteric pathologies next to a hip prosthesis with metallic artefact reduction for orthopaedic implants (O-MAR).

MATERIALS AND METHODS

Thirty-four patients who underwent pelvic computed tomography (CT) for non-prosthesis-related causes were enrolled retrospectively. Portal venous phase scans were reconstructed both with standard iterative reconstruction (ITR) and with O-MAR. The density of the ureters and the bladder was measured at both sides in the plane of the prosthesis. A semi-quantitative score was also used to assess visibility. The R (version 3.4.1) package was used for statistical analysis.

RESULTS

The average (μ) density of the 41 prosthesis side ureters was significantly lower on ITR images (μ=-94.76±150.48 [±SD] HU) than on O-MAR images (μ=-13.40±36.37 HU; p<0.0004). The difference between the ITR and O-MAR (μ=-138.62±182.64 versus -35.55±40.21 HU; p<0.0003) was also significant at the prosthesis side of the bladder. The visibility of the prosthesis side ureters was improved: 53.7% was obscured on ITR series compared to 4.9% on O-MAR. The visibility score was also better across all levels (p<0.001) with O-MAR. In four cases (13%), the O-MAR images significantly changed the diagnosis: in two cases ureteric stones, in one case each a bladder stone and a bladder tumour were discovered.

CONCLUSIONS

O-MAR reconstruction of CT images significantly improves the visibility of the urinary tract adjacent to metallic hip implants. Thus, O-MAR is essential for detecting ureteric and bladder pathologies in patients with a hip prosthesis.

A számítógépes mélytanulási technológia várható megjelenése a hazai mammográfiában

Abstract:

Introduction and aim: The technology, named ‘deep learning’ is the promising result of the last two decades of development in computer science. It poses an unavoidable challenge for medicine, how to understand, apply and adopt the – today not fully explored – possibilities that have become available by these new methods. Method: It is a gift and a mission, since the exponentially growing volume of raw data (from imaging, laboratory, therapy diagnostics or therapy interactions, etc.) did not solve until now our wished and aimed goal to treat patients according to their personal status and setting or specific to their tumor and disease. Results: Currently, as a responsible health care provider and financier, we face the problem of supporting suboptimal procedures and protocols either at individual or at community level. The problem roots in the overwhelming amount of data and, at the same time, the lack of targeted information for treatment. We expect from the deep learning technology an aid which helps to reinforce and extend the human–human cooperations in patient–doctor visits. We expect that computers take over the tedious work allowing to revive the core of healing medicine: the insightful meeting and discussion between patients and medical experts. Conclusion: We should learn the revelational possibilities of deep learning techniques that can help to overcome our recognized finite capacities in data processing and integration. If we, doctors and health care providers or decision makers, are able to abandon our fears and prejudices, then we can utilize this new tool not only in imaging diagnostics but also for daily therapies (e.g., immune therapy). The paper aims to make a great mind to do this. Orv Hetil. 2019; 160(4): 138–143.

Diffusion weighted magnetic resonance imaging demonstrates tumor response following palliative embolization of a recurrent shoulder plasmacytoma

We report the palliative embolization and functional imaging follow-up of a recurrent shoulder plasmacytoma. The multiple myeloma patient complained of severe pain and discomfort, while he could not tolerate further chemotherapy. The left shoulder lesion had earlier received a high dose of irradiation. Thus, the well-vascularized lesion was embolized via feeding arteries branching off from the left subclavian artery in two sessions. The patient’s symptoms rapidly improved post-embolization and the serum free light chain ratio stabilized at a lower level. The follow-up magnetic resonance image showed increased diffusivity in previously restricted tumor foci. This has negatively correlated with the decreased fludeoxyglucose uptake on PET, suggesting post-embolization necrosis.

Cerebral iodized lipid embolization via a pulmonary arteriovenous shunt: rare complication of transcatheter arterial embolization for hepatocellular carcinoma

We report the first European case of cerebral iodized lipid embolism post transcatheter arterial embolization for hepatocellular carcinoma. Lipiodol emboli and corresponding multifocal brain ischemia were documented with computed tomography (CT) and magnetic resonance (MR) in the acutely symptomatic patient. Transcranial Doppler sonography with contrast indicated a right-to-left shunt, while on a follow-up CT scan lipiodol embolization was detected in both lungs. Dilated pulmonary vessels and thick vascular channels were seen in the vicinity of the right diaphragm suggestive of pulmonary arteriovenous shunt. The patient symptoms regressed with supportive care alone, but he died 5 months later due to hepatic failure unrelated to the procedure.

Heritability of Venous Biomechanics

Objective—

Altered venous biomechanics may contribute to the pathogenesis of venous diseases, and their heritability is less known.

Methods and Results—

Seventy-eight monozygotic twin pairs (aged 42.4±16.8 years) and 24 same-sex dizygotic twin pairs (aged 50.5±16.1 years) were examined. Anteroposterior and mediolateral diameters of the common femoral vein were measured by ultrasonography. Measurements were made both in supine and in standing body positions, with or without controlled forced expiration (Valsalva test). High correlation of diameter, capacity, and distensibility values was found between twin pairs. The univariate heritability (A), shared (C), and unshared (E) environmental effects model has shown 39.3% genetic component of the variance of low pressure, 37.9% of high-pressure venous capacity, and 36.4% of maximal capacity changes, even after elimination of sex, age, and body weight effects. Bivariate Cholesky analysis revealed substantial covariance of inherited body weight and venous capacity components (57.0%–81.4%).

Conclusion—

Femoral vein capacity and elasticity depend ≈30% to 40% on genetic factors, and this value in the standing body position can reach 50%. A relatively high genetic covariance was found between weight and femoral vein capacity and elasticity. Our work might yield some new insights into the inheritance of venous diseases that are associated with altered venous biomechanics and help elucidate the involved genes.

[Characteristics of smoking and secondhand smoke exposure in monozygotic and dizygotic twins: results from an international twin study]

INTRODUCTION

Zygosity differences in smoking exposure are unclear in twins.

AIMS

To assess smoking and secondhand smoke exposure characteristics in twins.

METHODS

151 monozygotic and 62 dizygotic Hungarian and American adult twin pairs (age 43.8±16.5 years, mean±SD) participated in the study.

RESULTS

Monozygotic twins started smoking 1.8 years earlier compared to dizygotic twins (p = 0.08). Dizygotic twins smoked longer (p<0.01) and suffered more parental smoke exposure during childhood (p<0.05). Monozygotic twins reported stricter smoking restrictions at home and workplaces (p<0.005) and less smoke exposure in indoor public places (p<0.01). 85.7% of monozygotic twins were ex or active smokers, while only 69.5% of the dizygotics (p<0.01). Lesser difference was observed in the self-reported smoke exposure rate in monozygotic compared to dizygotic pairs concerning restaurants and cafés (p<0.05) which was not present regarding bars, pubs and transportation facilities.

CONCLUSIONS

Different psychological family orientation may be present across zygosity. Preventive parental care is warranted in twin families exposed to smoking.

[Percutaneous, endovascular treatment of innominate artery lesions is a safe and effective procedure]

Percutaneous endovascular treatment (transluminar balloon angioplasty with or without stent implantation) of innominate artery lesions has become the treatment of choice prior to surgery in the past decades. Authors present the diagnostics, treatment and follow-up of two patients as examples from their largest series in the literature. A 74-year-old male patient with a history of hyperlipidemia, hypertension, nicotine abuse and lower limb claudication was admitted because of acute upper limb claudication and dizziness. Physical examination revealed blood pressure difference of 30 mmHg between his arms, and poststenotic flow pattern in the common carotid artery with retrograde flow in the vertebral artery on carotid duplex scan. Diagnostic angiography showed 80% stenosis of the innominate artery, which was treated with percutaneous transluminar balloon angioplasty with stent implantation. Follow-up examination at 5 months showed no significant restenosis or neurological complication. The second patient was a 59-year-old smoker female patient with hypertension and type 2 diabetes mellitus, who was evaluated for her upper limb claudication. Initial finding was the absence of radial pulse in the right side. Color duplex scan revealed proximal subocclusion, which was confirmed by angiography. In one stage, balloon angioplasty was made, with immediate pain relief. After 15 months the patient was symptom-free. These two cases demonstrate an excellent outcome of endovascular treatment of innominate artery lesions, as authors already reported in two retrospective studies. Balloon angioplasty with, or without stent deployment appears to be a safe procedure with excellent primary success rate. Review of international studies also indicates that endovascular therapy of the innominate artery is safe and effective.

MR imaging FOLLOW UP after MR-guided Focused Ultrasound Surgery for uterine leiomyomas — Early and mid term results

Rationale and Objectives: MR-guided Focused Ultrasound Surgery (MRgFUS) is an evolving thermoablative technique for treatment of benign and malignant soft tissue tumors. The feasibility and effectiveness of this non-invasive method has been tested by several investigators by treating uterine fibroid. The aim of the present study was to evaluate early and mid-term efficacy of MRgFUS treatment using MR imaging follow-ups. Materials and Methods: 38 patients with uterine fibroids were enrolled and treated by MRgFUS in a single center. MRI follow-up exams were performed 3 and 6 months after the procedure. Total fibroid volumes (FV) and non-perfused volumes (NPV) were compared and evaluated over time. Results: There was a significant reduction of FV at 3- and 6-month follow-ups (10±19%, p=0.022 and 19±29%, p<0.001, respectively). In the subgroup of fibroids smaller than 5.4 cm in diameter a 35±18% volume reduction was found after 6 months. There was also a positive correlation found between the early NPV and the FV decrease at 3- and 6-months follow-ups. Conclusion: This study suggests that MRgFUS can effectively coagulate uterine fibroid tissue. Smaller UFs can be most effectively treated within reasonable time with the used equipment.

Post-traumatic pseudoaneurysm of the great saphenous vein: a case report

Venous (pseudo)aneurysms are rare entities. Herewith we report a case of the right lower extremity in a 42-year-old woman in whom a non-pulsatile mass was diagnosed only by physical examination as a hematoma and was treated conservatively. Six months later ultrasound and phlebography identified a pseudoaneurysm of the great saphenous vein. Post-traumatic venous pseudoaneurysm should be considered among the differential diagnostic options of a subcutaneous non-pulsatile mass in patients with a history of physical trauma. Surgery was offered which was rejected by the patient. Further one month follow-up showed no change.

High-resolution CT and angiographic evaluation of NexStent wall adaptation

Carotid stenting is a minimally invasive treatment for extracranial carotid artery stenosis. Stent design may affect technical success and complications in a certain subgroup of patients. We examined the wall adaptability of a new closed-cell carotid stent (NexStent), which has a unique rolled sheet design. Forty-one patients had 42 carotid arteries treated with angioplasty and stenting for internal carotid artery stenosis. The mean patient age was 65 +/- 10 years. All patients underwent high-resolution computed tomographic angiography after the stent implantation. Data analysis included pre- and postprocedural stenosis, procedure complications, plaque calcification, and stent apposition. We reviewed the angiographic and computed tomographic images for plaque coverage and stent expansion. All procedures were technically successful. Mean stenosis was reduced from 84 +/- 8% before the procedure to 15.7 +/- 7% after stenting. Two patients experienced transient ischemic attack; one patient had bradycardia and hypotension. Stent induced kinking was observed in one case. Good plaque coverage and proper overlapping of the rolled sheet was achieved in all cases. There was weak correlation between the residual stenosis and the amount of calcification. The stent provides adequate expansion and adaptation to the tapering anatomy of the bifurcation.

[New results in the research of the biomechanics of the venous system]

The upright posture of man had been a major evolutional challenge. The mechanisms responsible for orthostatic tolerance mostly affect the venous system. In this paper, we discuss new results regarding the biomechanics of the venous system highlighting a rather neglected field, the biomechanical properties of the vein wall. These properties change according to localization of veins, age, gender and body mass. The anti-gravitational adaptation of veins is a complex process involving all three layers of the venous wall. Local myogenic and humoral mechanisms as well as systemic hormonal and nervous influences control the adaptive processes in the veins. Long term adaptation involves structural and functional remodeling of the venous wall. Disorders of the veins mostly cause pathological remodeling. Hemodynamic factors (pressure and flow) together with inflammatory processes may lead to pathological alterations, changing the biomechanical properties of the vein wall, which further contribute to the reservation and progression of venous dysfunction. Appropriate testing of venous function can reveal biomechanical disorders even in clinically asymptomatic patients. Thus, biomechanical investigation of veins not only helps to understand the underlying pathomechanism but it also can contribute to early diagnosis and follow-up of venous disorders. When recognized in time, pathological remodeling can be prevented or treated. In this way, the incidence of venous disorder could be cut back reducing both human suffering and material loss.

Generalized alterations in the biomechanical properties of large veins in non-thrombotic thrombophilic young patients

AIM

In young, post-thrombotic patients, venous distensibility is decreased not only in the affected lower limb, but also in the contralateral limb and in the jugular vein when compared to age-matched control subjects. In the present study, we investigated venous wall mechanical properties in young, asymptomatic thrombophilic patients.

METHODS

Eleven young (24+/-0.4 years) control subjects and 9 age-matched patients (21.1+/-1.8 years) with proven thrombophilic molecular defects, but without any signs or history of previous deep vein thrombosis, were compared. Anterolateral and mediolateral diameters of the common femoral, axillary and internal jugular veins were measured by ultrasonography in situ. Pressure alterations were induced by altering body positions and by pressure-controlled Valsalva tests. Distensibility was calculated from diameter and pressure changes.

RESULTS

In thrombophilic patients, resting diameter of both the common femoral and of internal jugular veins at low transmural pressure was larger than those for the control subjects. Distensibility, however, was significantly less when high pressures were applied. Alterations in diameter of the axillary vein were minimal.

CONCLUSION

Our measurements suggest that there are generalized changes in venous mechanical properties in thrombophilic patients even before the appearance of thrombotic processes. These biomechanical alterations of the venous wall and/or surrounding connective tissue are similar to those found in connection with aging and in post-thrombotic patients. The pathological mechanisms behind these processes are unknown.

[Endovascular stents for carotid stenosis]

In this paper the indication, technical details and data from randomised controlled trials of carotid stenting (CAS) are reviewed. The audit data of carotis stenting from our centre of 703 CAS patients from the period between January 1, 2003 and July 31, 2006, including perioperative (24-48 hours) complications is also discussed. The success rate and complication rate from our centre is comparable with the internationally excepted levels. The results of ongoing international trials are awaited to get more detailed answers regarding the advantages and disadvantages of CAS compared to carotid endarterectomy.

Non-invasive assessment of human large vein diameter, capacity, distensibility and ellipticity in situ: dependence on anatomical location, age, body position and pressure

The objective was to compare in-situ diameter, capacity and distensibility changes as well as ellipticity of large human veins of different locations, reveal alterations with age, body position and increased intraluminal pressure. Ultrasonographic assessment of mediolateral and anteroposterior diameters was performed of femoral, axillary and inner jugular veins, in erect and reclined positions as well as before and during controlled Valsalva test. Groups of young (24.0+/-0.4 years, n=11) and elderly (72.6+/-1.5 years, n=11) subjects were studied. Capacity of the femoral vein (reclined patients) gradually increased when a graded Valsalva test was applied. Its in situ distensibility was found to be 0.048+/-0.011 mm Hg(-1) between 0-15 mm Hg (1 mm Hg=0.133 kPa) pressure loads in reclined young subjects, which decreased to 0.009+/-0.005 mm Hg(-1) at 45-60 mm Hg. The femoral vein was considerably more rigid in the erect than in the reclined body position while an opposite correlation was found for the inner jugular vein. Axillary vein distensibility was very low and independent of body position. Ellipticity of femoral and axillary veins was minimal (the ratio of the two perpendicular diameters <1.25). Inner jugular veins were more elliptic in the erect position and without Valsalva (2.94+/-0.99 in young patients). Old femoral veins had higher capacity in the reclined position without Valsalva, while distensibility at low pressures was much more prominent in young vessels. The in situ femoral vein is more distensible in supine than in erect position, opposite to the inner jugular vein. The axillary vein is rather rigid in both positions. Only the inner jugular vein shows significant elipticity in situ. Aging decreases the distensibility of the femoral vein in reclined position.

Generalized changes in venous distensibility in postthrombotic patients

INTRODUCTION

In situ biomechanical properties of peripheral large veins were compared between asymptomatic young patients who had previously unilateral femoro-popliteal deep venous thrombosis (DVT) and age-matched, healthy controls; the aim of this study was to assess local or generalized alterations of venous wall biomechanics in postthrombotic patients.

PATIENTS AND METHODS

Inner diameters of both common femoral veins, right axillary vein, and right internal jugular veins were measured in two directions by ultrasonography. Venous pressure was altered by posture changes (standing and lying) and by application of graded and controlled Valsalva. Ten postthrombotic young patients without any symptoms and 11 age-matched control subjects were included.

RESULTS

In postthrombotic patients, both the affected and unaffected common femoral vein diameters and capacities were larger at low transmural pressures than those for the control group, but they demonstrated significantly less distensibility when higher pressures were applied. Similarly, in the internal jugular vein, capacity without Valsalva was significantly higher in postthrombotic patients and distensibility was reduced (statistically significant in the erect position). Pressure-induced changes in axillary vein diameter were negligible.

CONCLUSIONS

In situ diameter and capacity changes, and in situ distensibility of the femoral veins on both sides (i.e., the side of previous thrombosis as well as the disease-free side) and of the jugular veins are reduced in the young DVT patients compared to veins of the age-matched, healthy controls. The pathophysiological mechanism of generalized venous wall changes in these young DVT patients remains unknown.

Long-term adaptation mechanisms in extremity veins supporting orthostatic tolerance

Several long-term antigravity defense mechanisms are activated in the lower extremity veins and microvessels when an organism is exposed to chronic orthostatic load. These mechanisms involve acute pressure-induced myogenic response, counterregulatory K+ channels, functional and structural remodeling of sympathetic innervation, and vascular network properties.

[Physiologic mechanisms in extremity veins supporting chronic orthostatic tolerance]

As a consequence of chronic orthostatic load of the organism several long-term antigravitation defense mechanism are activated in the lower extremity veins and microvessels. The following adaptive mechanisms are brought into focus: acute pressure-induced myogenic tone and its augmentation which promote the venous capacity autoregulation, potassium channels counterregulating the depolarization of the venous smooth muscle membrane, functional and structural remodeling of sympathetic innervation in the vascular wall, changes in venous network properties, decreased capillary supply in oxidative muscles of the extremities, and probably transendothelial homeostatic water transport in the wall of veins.

Early experience and midterm follow-up results with a new, rotational thrombectomy catheter

PURPOSE

To assess the efficacy and safety of the Rotarex rotational thrombectomy catheter in treating occlusions of the femoropopliteal arteries.

METHODS

The Rotarex catheter (Straub Medical, Switzerland) is a rotational thrombectomy device which is supposed to be able to remove fresh and partially organized clot material from an acutely or subacutely occluded vessel. Nineteen limbs of 18 patients (10 women, 8 men; mean age 72.9 +/- 7.3 years) with acute or subacute (23 +/- 16 days) occlusions of the middle or distal third of the superficial femoral artery or the popliteal artery were treated. The occlusions were 3-20 cm long.

RESULTS

Thrombectomy was technically successful in 15 of 19 vessels (79%). The primary procedural success including additional procedures such as angioplasty and/or stent-graft placement in 17 limbs was 94%. The mean ankle-brachial index improved from 0.36 +/- 0.26 (before thrombectomy) to 0.81 +/- 0.21 (2 days after the procedure) (p = 0.012). Clinical symptoms shifted to at least one Fontaine stage lower in 13 limbs. As complications we observed two perforations (arteries showing heavily calcified plaques), one arteriovenous fistula and three distal embolizations. One perforation, the fistula and one intimal tear after percutaneous transluminal angioplasty were treated with covered stents; the three distal embolizations were treated successfully with aspiration or Rotarex thrombectomy. In the other perforation the intervention was terminated. None of the complications needed surgical treatment. The complication rate was 31.5%. Follow-up studies showed three early (4-11 days) and six late (1-6 months) reocclusions. The cumulative primary patency rate was 68 +/- 12% at 3 months, and 39 +/- 13% at 6, 12 and 19 months; the secondary patency rate was 68 +/- 12% at 3 months and 53 +/- 13% at 6, 12 and 20 months.

CONCLUSION

The Rotarex thrombectomy catheter is effective and quick in treating acute and subacute occlusions of the superficial femoral and popliteal arteries. It should not be used in arteries with heavily calcified plaques because of the risk of perforation. Limited long-term patency is mainly due to the complexity of the underlying lesion. Our results suggest that the Rotarex mechanical thrombectomy catheter is effective and might serve as an alternative treatment modality to intra-arterial lysis.

Angioplasty of the innominate artery in 89 patients: experience over 19 years

PURPOSE

To assess retrospectively the success of percutaneous transluminal angioplasty (PTA) in treating innominate artery stenoses and occlusions in a large series of patients with long-term follow-up results.

METHODS

In symptomatic (upper limb claudication, transient ischemic attack, vertebrobasilar insufficiency) patients with high-degree (>60%) stenosis, innominate artery PTA was performed. Long-term follow-up was undertaken by blood pressure measurements on both arms as well as subclavian, right common carotid and right vertebral duplex scan.

RESULTS

Between 1981 and 1999, the primary success rate of 89 innominate artery PTA (84 stenoses, 5 occlusions) was 96.4%. Complications included one left occipital lobe infarction (2%), two puncture-site thromboses (3%) and four transient ischemic attacks (6%). Two patients with restenosis were successfully treated with re-PTA. Cumulative primary patency was 98 +/- 2% at 6 months, 93 +/- 4% at 16-117 months; secondary patency was 100% at 6 months, 98 +/- 2% at 12-117 months. Sixty-one percent of the patients became symptomless, 32% improved, 7% showed no improvement.

CONCLUSION

Angioplasty of the innominate artery has been proven to be safe and effective on a large series of patients. For innominate artery stenosis and short occlusion, PTA should be the treatment of choice.

[Percutaneous angioplasty of the innominate artery in 89 patients: experience of 19 years]

PURPOSE

To assess retrospectively the success of percutaneous transluminal angioplasty (PTA) in treating innominate artery stenoses and occlusion in a large series of patients with long-term follow-up results.

METHODS

In symptomatic patients with high degree (> 60%) stenosis, innominate artery PTA was performed. Long-term follow-up was undertaken by blood pressure measurements on both arms as well as subclavian, right common carotid and right vertebral duplex scan.

RESULTS

Between 1981 and 1999, primary success rate of 89 innominate artery PTA (84 stenoses, 5 occlusions) was 96.4%. Complications included 1 left occipital lobe infarction (1.5%), 2 puncture-site thrombosis (2.9%), and 4 TIA (5.8%). Two patients with restenosis were successfully treated with rePTA. Cumulative primary patency was 98 +/- 2% at 6 months, 93 +/- 4% at 16 to 117 months, secondary patency was 100% at 6 months, 98 +/- 2% at 12 to 117 months; 61% of the patients became symptomless, 32% improved, 7% showed no improvement.

CONCLUSION

Angioplasty of the innominate artery has been proven to be safe and effective on a large series of patients. For innominate artery stenosis and short occlusion, PTA should be the first treatment of choice.

Placement of Hemobahn stent-grafts in femoropopliteal arteries: early experience and midterm results in 18 patients

PURPOSE

To determine the outcome of a new polytetrafluoroethylene (PTFE)-covered stent-graft in the treatment of occlusive lesions of the femoropopliteal arteries.

MATERIALS AND METHODS

Eighteen patients with intermittent claudication (Fontaine stages IIb-IV; Rutherford classes I/2-III/5) and occlusive lesions of the superficial femoral and/or popliteal artery were treated with use of a new PTFE-covered stent-graft (Hemobahn). Indication for stent-graft insertion was an unsatisfactory result after balloon dilation.

RESULTS

Successful stent-graft placement was achieved in 17 patients (94%). In one patient, additional insertion of a Palmaz stent was necessary because of a stent-graft wrinkle. Mean ankle-brachial index increased from 0.72 +/- 0.15 preoperatively to 0.94 +/- 0.17 postoperatively (P =.028). Fifteen patients (83%) experienced an initial improvement of at least one clinical stage. Primary patency was 61% +/- 11% at 3 months and 49% +/- 12% at 6 months. Stent-graft occlusion was observed in 13 patients (72%). In four patients, the stent-graft was reopened percutaneously by balloon angioplasty (n = 2) and/or rotational thrombectomy (n = 2). Therefore, the secondary patency rate was 67% +/- 11% at 3 months and 61% +/- 11% at 6 months. Patency rates proved to be significantly lower for stent-grafts longer than 10 cm (P =.03). Intimal hyperplasia at the proximal or distal end of the stent-graft was observed in seven patients (39%). Complications such as access site hematoma (n = 3), distal thromboembolism (n = 2), and abscess formation around the stent-graft (n = 1) were observed.

CONCLUSION

Despite excellent initial angiographic results, the patency rate in lesions treated with the Hemobahn stent-graft in this small study was unsatisfactory. Use of stent-grafts longer than 10 cm and the occurrence of intimal hyperplasia proved to be major factors in the reduction of long-term patency rates.

Venous myogenic tone and its regulation through K+ channels depends on chronic intravascular pressure

In this study, we compared the level of myogenic tone and its negative-feedback control through specific K+ channels in two types of human veins (saphenous [SV] and cephalic [CV] veins), which experience different ranges of pressure in vivo. We also investigated whether an experimental model of increased venous pressure in rats exposed to head-up tilt for 2 weeks produced changes similar to those observed in the human veins. Cylindrical vein segments were cannulated, their diameters were measured, and the intraluminal pressure was set at different levels (2 to 30 mm Hg) in vitro. Acetylcholine test showed that during the regular harvesting process 76% of the human SVs exposed for coronary bypass grafts had no functional endothelium. We found significant myogenic tone in the human SV, where the in vivo pressure is high, but it was not present in the human CV, where the in vivo pressure is low. The nonspecific K+ channel antagonist, tetraethylammonium (TEA), decreased the diameter of the human SV but not the CV. Iberiotoxin and 4-aminopyridine, blockers of the Ca(2+)-sensitive (KCa) and voltage-gated K+ (KV) channels, also decreased the diameter of the human SV by 10.2 +/- 4.8% and 19.5 +/- 4.7%, respectively. In the rat SV, significant myogenic tone was found, but TEA had no effect, even after 2 weeks of in vivo pressure increase in the hindlimb by head-up tilt. We conclude that (1) an increased venous myogenic tone correlates with higher chronic intraluminal pressure loads, (2) KCa and KV channels counterregulate the myogenic tone in human, but not in rat, saphenous vein, (3) the counterregulatory effect is more effective at high than at low intraluminal in vitro pressure levels, and (4) its development is probably a long-term process.

Local control of veins: biomechanical, metabolic, and humoral aspects

The incidence of vein diseases (varicosity, thrombophlebitis, phlebosclerosis, orthostatic intolerance) is extremely high. In several countries it may exceed that of the arterial pathology by an order of magnitude. In the last decades, this recognition and the rapid accumulation of experimental data have resulted in a progressive reevaluation of the physiological significance of the venous system, which had been rather neglected earlier by scientists. The major aim of this review is to provide a critical survey of recent selected literature related to different physiological functions of the venous system as well as to biomechanical, metabolic, and humoral (ionic, hormonal) aspects of the local venous control. Local neural control mechanisms, including effects of catecholamines and other transmitters, are regarded to be beyond the scope of this work. At present, the synthesis of information available in the literature meets certain difficulties, because occasionally poorly defined methodological techniques and physiological parameters have been applied. On the other hand, a significant part of works dealing with venous physiology is excellent and inspirational. We have good reason to believe that the fast accumulation of reliable scientific data on this very important field will soon reach a new critical level, then an even more effective integration of knowledge will be possible.

Venous myogenic tone: studies in human and canine vessels

Active and passive mechanical properties of human saphenous and canine femoral and saphenous vein segments were measured in vitro to assess the degree of pressure-dependent venous myogenic tone (% change in diameter, physiological saline solution vs. Ca(2+)-free solution) in these vessels. Stepwise elevation of intraluminal pressure from 2 to 20 mmHg caused an active myogenic response, which was calcium dependent. Side branches of human saphenous veins (OD at 20 mmHg: 1.92 +/- 0.15 mm control; 2.41 +/- 0.18 mm relaxed) displayed a larger degree of myogenic tone (approximately 25%) compared with dog saphenous (OD: 2.84 +/- 0.16 mm control; 2.89 +/- 0.16 mm relaxed) and femoral (OD: 3.56 +/- 0.32 control; 3.66 +/- 0.31 mm relaxed) veins (2-3%). This alteration in myogenic tone results in over 120% change in lumen capacity for the human saphenous vein, whereas for the dog saphenous and femoral veins, the change in lumen capacity is less than 10%. The vessels showed a constriction to norepinephrine as well as a reversible dilation to Ca(2+)-free perfusion. These results support the hypothesis that an active myogenic response may play an important role in the regulation of vascular capacity in the human saphenous vein, which is subject to substantial pressure variations due to changing orthostatic loads.

Role of endothelium in the response of the vein wall to magnesium withdrawal

Complete absence of magnesium has a two-fold effect on the arterial tone: direct smooth muscle contraction and relaxation via endothelium-derived relaxing factor (EDRF) release. In the present study performed on a systemic vein we investigated (1) which of these effects dominates following reduction of magnesium concentration from 1.2 mM to 0.8 and 0.4 mM and (2) whether the vessel segments asymmetrically respond when the magnesium concentration is reduced on either the intra- or extraluminal side. The effects of reducing magnesium concentration on both the isometric tension of isolated ring preparations and the diameter of isolated, perfused and superfused feline femoral veins were investigated. In noradrenaline-precontracted rings, rapid decreases in the extracellular magnesium concentration from 1.2 mM to 0.8 and 0.4 mM caused relaxation, whereas total omission of magnesium returned the tone to the level of the initial tone induced by noradrenaline. Both in the presence of haemoglobin (5 x 10(-6) M), and in vessels without endothelium, lowering the magnesium concentration caused a dose-dependent elevation of the noradrenaline-induced tone. In perfused and superfused noradrenaline-contracted vein segments, each reduction of extraluminal magnesium concentration caused contraction of the vessels, regardless of whether the endothelium was intact or not. A decrease in intraluminal magnesium concentration did not alter the diameter of the vessel when the endothelium was intact, but caused contraction when the endothelium was disrupted. The results of the present study demonstrate that both the reduction of magnesium concentration or its complete absence cause an EDRF-mediated relaxation and a directly mediated smooth muscle contraction in the femoral vein of the cat.(ABSTRACT TRUNCATED AT 250 WORDS)

Lymphatic arteriopathy: damage to the wall of the canine femoral artery after lymphatic blockade

The effect of lymph stasis on the histological, biochemical, and elastic properties of the femoral artery were studied after regional lymphatic blockade in 36 dogs. Dogs were sacrificed 4-21 days after operation. Histologic changes of the femoral arterial wall (interstitial edema, degeneration in the muscle layer or media, thickened adventitia with dilated lymph vessels, and fibrosis) developed after regional lymphatic blockade. Characteristic metabolic alterations of the arterial wall (anaerobic catabolism of carbohydrate, increased lactate and glycosamine content) accompanied the morphological changes. Distensibility of the femoral artery decreased and greater elastic stiffness developed after regional lymphatic blockade. These results in conjunction with other experimental and clinical data support the concept that insufficient lymphatic transport within the blood vessel wall may contribute to the genesis and progression of arteriopathies.

Effect of two week lymphatic occlusion on the mechanical properties of dog femoral arteries

In order to study the long-term effect of impaired lymphatic drainage on the mechanical properties of the arterial wall, cylindrical femoral artery segments from 10 mongrel dogs after 2 weeks of hindlimb lymphatic occlusion were subjected to in vitro mechanical test and compared with the contralateral, sham-operated segments. Smooth muscle contraction was induced by norepinephrine (7.4 X 10(-6) M) and smooth muscle relaxation by papaverine (1.6 X 10(-4) M). As a result of 2 weeks of lymphatic occlusion, wall thickness increased from 243 +/- 18 to 343 +/- 35 microns (P less than 0.02), inner radius decreased from 1.69 +/- 0.11 to 1.42 +/- 0.12 mm (P less than 0.01) and elastic modulus decreased from 1.23 X 10(6) to 0.55 X 10(6) N/m2 (P less than 0.01), when determined at 100 mm Hg (13.3 kPa) intraluminal pressure and with relaxed smooth muscle. The contractile apparatus was able to produce active strain in the vessels with lymphostasis and at physiological pressures not significantly different from the controls (0.89 +/- 0.02 vs. 0.91 +/- 0.02), but at significantly lower levels of tangential stress. Active stress decreased significantly. This study shows that a reorganization of the vessel wall mechanical force-bearing elements occurs in lymphostasis, which, in some respects, resembles the mechanical alterations found in different forms of atherosclerosis.

Decreased vascular contraction and elastic stiffening after intramural lymphostasis

Lymphatic obstruction leads to leakage of protein into the vessel wall that is coupled with edema formation and smooth muscle degeneration. To clarify the mechanical effect of these changes, lymphatic trunks, draining the femoral artery, were stained with Evans blue and then ligated in dogs anesthetized with pentobarbital sodium (n = 11). Sham ligation was performed on these lymphatic trunks in the opposite hindlimb (n = 11). Three days later, 7- to 30-mm segments of both femoral arteries were studied in vitro. Intraluminal pressure was cycled between 5 and 250 mmHg at 5 mmHg/s, and external diameter was recorded in both relaxed and activated (norepinephrine, 3 x 10(-5) mol/l) state of smooth muscle. Mechanical parameters were computed for 10-mmHg pressure increments. After lymphatic obstruction, strain energy density and distensibility of the passive wall components as well as isobaric active tangential strain were decreased by a maximum of 27, 59, and 54%, respectively; active tangential stress and elastic modulus, as a function of tangential stretch, was decreased by a maximum of 62%, and increased by 61%, respectively. These results indicate that short-term intramural lymphostasis reduces smooth muscle reactivity and induces vascular stiffening.