Experimental multiparametric magnetic resonance imaging characterization of iliocaval venous thrombosis pathological changes

OBJECTIVE

Iliocaval thrombotic obstruction is a challenging condition, especially because thrombus age and corresponding pathological remodeling at presentation are unknown, which directly impacts management. Our aim was to assess the ability of magnetic resonance imaging (MRI) in determining age thresholds of experimentally created inferior vena cava (IVC) thrombosis in pigs.

METHODS

We used a previously described swine model of IVC thrombosis. The animals underwent MRI at baseline, immediately after thrombosis creation, and after a follow-up period extending from 2 to 28 days. Thirteen pigs were divided into three groups according to disease chronicity: acute group (AG; n = 5), subacute group (SAG; n = 4), and chronic group (CG; n = 4), with a mean thrombosis age of 6.4 ± 2.5 days, 15.7 ± 2.8 days, and 28 ± 5.7 days, respectively. A T1-weighted volumetric interpolated breath-hold examination sequence was used to anatomically delineate IVC thrombus as a region of interest. Three other MRI sequences were used to assess the thrombus signal.

RESULTS

The Kruskal-Wallis test showed a statistically significant difference in T1 relaxation times after contrast injection (P = .026) between the three groups of chronicity. The AG (360.2 ± 102.5 ms) was significantly different from the CG (336.7 ± 55.2 ms; P = .003), and the SAG (354.1 ± 89.7 ms) was significantly different from the AG (P = .027). There was a statistically significant difference in native T2 relaxation times (P = .038) between the three groups. The AG (160 ± 86.7 ms) was significantly different from the SAG (142.3 ± 55.4 ms; P = .027), and the SAG was significantly different from the CG (178.4 ± 11.7 ms; P = .004).

CONCLUSIONS

This study highlighted MRI characteristics in a swine model that might have the potential to significantly differentiate subacute and chronic stages from an acute stage of deep vein thrombosis in humans. Further clinical studies in humans are warranted.

CLINICAL RELEVANCE

In addition to providing a better understanding of venous thrombosis remodeling over time, magnetic resonance imaging has the potential to be a tool that could allow us to characterize the composition of venous thrombus over an interval, allowing for a refined analysis of the local evolution of venous thrombosis. We propose a noninvasive and innovative method to characterize different thresholds of chronicity with magnetic resonance imaging features of central deep vein thrombosis of the inferior vena cava experimentally obtained using a totally endovascular in vivo swine model, mimicking human pathophysiology. Being able to determine these features noninvasively is critical for vascular specialists when it comes to choosing between fibrinolytic therapy, percutaneous thrombectomy, or surgical management.

Ultrasound Elastography to Assess Age of Deep Vein Thrombosis: A Systematic Review

BACKGROUND AND AIMS

Deep-vein thrombosis (DVT) is a widely diffused condition, and its accurate staging has major clinical and therapeutic implications. Ultrasound elastography (UE) is a rapidly evolving imaging technique that allows quantification of elastic tissue properties and could play a crucial role in determining thrombus age. The aim of this review is to find clinical evidence regarding the application of UE in the evaluation of DVT and its usefulness in differentiating thrombosis age.

METHODS

A literature search of clinical studies was performed to identify the ability of UE of discriminate acute, subacute, and chronic DVT. Heterogeneity and publication bias were calculated. In accordance with the study protocol, a qualitative analysis of the evidence was planned. The results were summarized with a comprehensive summary table of study characteristics and baseline characteristics of participant patients.

RESULTS

Nine studies matched the predetermined eligibility requirements for this systematic review regarding the risk of bias; the greatest criticalities were found within the domains of patient selection and index test. Based on the quality assessment, two publications were excluded from the qualitative synthesis because of the presence of significant applicability concerns. Among the seven studies that were considered eligible for qualitative synthesis, four evaluated strain elastography and three evaluated shear-wave elastography. Despite significant differences concerning study design, thrombus age definitions, and patient characteristics, nearly all studies demonstrated an increase in thrombus stiffness according to DVT age.

CONCLUSIONS

UE could play a key role in routine ultrasound examination of DVT. The measurement of thrombus stiffness has a high biological plausibility and its use is supported by the finding of a correlation between the stiffness and the progression of the DVT age.

Radiomics model using preoperative computed tomography angiography images to differentiate new from old emboli of acute lower limb arterial embolism

Our purpose was to devise a radiomics model using preoperative computed tomography angiography (CTA) images to differentiate new from old emboli of acute lower limb arterial embolism. 57 patients (95 regions of interest; training set: n = 57; internal validation set: n = 38) with femoral popliteal acute lower limb arterial embolism confirmed by pathology and with preoperative CTA images were retrospectively analyzed. We selected the best prediction model according to the model performance tested by area under the curve (AUC) analysis across 1,000 iterations of prediction from three most common machine learning methods: support vector machine, feed-forward neural network (FNN), and random forest, through several steps of feature selection. Then, the selected best model was also validated in an external validation dataset (n = 24). The established radiomics signature had good predictive efficacy. FNN exhibited the best model performance on the training and validation groups: its AUC value was 0.960 (95% CI, 0.899-1). The accuracy of this model was 89.5%, and its sensitivity and specificity were 0.938 and 0.864, respectively. The AUC of external validation dataset was 0.793. Our radiomics model based on preoperative CTA images is valuable. The radiomics approach of preoperative CTA to differentiate new emboli from old is feasible.

Ultrasound Elastography to Differentiate the Thrombus and Plaque in Peripheral Arterial Diseases

Purpose

Arterial stiffness and steno-occlusion of the lower-extremity can result from many vascular lesions, including acute thromboembolisms, soft plaques, calcified plaques, or inflammatory disease. Ultrasound (US) elastography measures the tissue deformation response to compression and displays tissue stiffness. This study aimed to evaluate the characteristics of arterial lesions in the lower extremities using US elastography.

Materials and Methods

We retrospectively analyzed the data of 20 patients who visited our institute for arterial disease treatment between May 2016 and November 2017. An US examination with B-mode and strain elastography (SE) was performed of four different lesion types at 45 sites: acute and subacute thromboembolisms, soft plaques, calcified plaques, and thromboangiitis obliterans lesions (TAOs). During SE, stress was externally applied by the operator using the transducer. Strain ratio (SR) was calculated as the fraction of the average strain in the reference area divided by the average strain in the lesion. The SR was compared among different lesion types, with the accompanying vein as the reference region of interest.

Results

The strain was highest in the soft plaques (0.63%±0.23%), followed by the TAOs (0.45%±0.11%), calcified plaques (0.44%±0.13%), and acute thromboembolisms (0.34%±0.23%), which were statistically significant (P=0.026). However, the mean SR was highest for the calcified plaques (2.33%±0.80%), followed by the TAOs (1.63%±0.40%), acute thromboembolisms (1.60%±0.48%), and soft plaques (1.51±0.39), and which were statistically significant (P=0.013).

Conclusion

Despite several limitations, vascular elastography may be useful for differentiating between lesion types in peripheral arterial disease.

A Systematic Review and Meta-Analysis of 12-Month Patency After Intervention for Iliofemoral Obstruction Using Dedicated or Non-Dedicated Venous Stents

BACKGROUND

Endovascular stenting of the deep venous system has been proposed as a method to treat patients with symptomatic iliofemoral outflow obstruction. The purpose of this systematic review and meta-analysis was to compare the effectiveness of this treatment at 1-year following the development of dedicated venous stents.

METHOD AND RESULTS

We searched MEDLINE and EMBASE for studies evaluating the effectiveness of venous stent placement. Data were extracted by disease pathogenesis: non-thrombotic iliac vein lesions (NIVL), acute thrombotic (DVT), or post-thrombotic syndrome (PTS). Main outcomes included technical success, stent patency at 1 year and symptom relief. A total of 49 studies reporting outcomes in 5154 patients (NIVL, 1431; DVT, 950; PTS, 2773) were included in the meta-analysis. Technical success rates were comparable among groups (97%-100%). There were no periprocedural deaths. Minor bleeding was reported in up to 5% of patients and major bleeding in 0.5% upon intervention. Transient back pain was noted in 55% of PTS patients following intervention. There was significant heterogeneity between studies reporting outcomes in PTS patients. Primary and cumulative patency at 1 year was: NIVL-96% and 100%; DVT-91% and 97%; PTS (stents above the ligament)-77% and 94%, and; PTS (stents across the ligament)-78% and 94%. There were insufficient data to compare patency outcomes of dedicated and nondedicated venous stents in patients with acute DVT. In NIVL and PTS patients, stent patency was comparable at 1 year. There was inconsistency in the use of validated tools for the measurement of symptoms before and after intervention. When reported, venous claudication, improved in 83% of PTS patients and 90% of NIVL patients, and ulcer healing occurred in 80% of PTS patients and 32% of NIVL patients.

CONCLUSIONS

The first generation of dedicated venous stents perform comparably in terms of patency and clinical outcomes to non-dedicated technologies at 1 year for the treatment of patients with NIVL and PTS. However, significant heterogeneity exists between studies and standardized criteria are urgently needed to report outcomes in patients undergoing deep venous stenting.

Comparison Between the Diagnostic Performance of 1.5 T and 3.0 T field Strengths for Detecting Deep Vein Thrombosis Using Magnetic Resonance Black-Blood Thrombus Imaging

BACKGROUND

Magnetic resonance (MR) black-blood thrombus imaging (BTI) is an accurate diagnostic technique for detecting deep vein thrombosis (DVT) but to date there have been no studies comparing the diagnostic performance and consistency of this technique at different field strengths. In this study, we evaluated and compared the diagnostic performance of BTI for detecting DVT at 1.5 T and 3.0 T field strengths.

METHODS

A total of 40 patients with DVT were enrolled in this study from November 2015 up to October 2018. All patients underwent BTI, a contrast-free T1-weighted MR imaging technique for detecting DVT, and contrast-enhanced MR venography (CE-MRV) at 1.5 T or 3.0 T field strengths. The MR data analyses used 1160 segments from the venous lumen of the 40 patients. The signal-to-noise ratio and contrast-to-noise ratio between thrombus and muscle/lumen were calculated to compare BTI at 1.5 T or 3.0 T to determine the image performance for thrombus detection at 1.5 T or 3.0 T. Two physicians blinded to the study evaluated all BTI images and calculated the overall sensitivity (SE), specificity (SP), positive predictive value (PPV) and negative predictive value (NPV), accuracy, and diagnostic consistency at 1.5 T and 3.0 T. These images and values were compared to control CE-MRV images that had been obtained by 2 senior physicians and used as reference standards. In addition, the reliability and consistency of diagnoses between observers were also evaluated.

RESULTS

Two study-blind physicians reviewed all BTI images to diagnose thrombus and to determine SE, SP, PPV, NPV, and accuracy. There were no statistical differences in SE, SP, PPV, NPV, or accuracy between the 1.5 T and 3.0 T groups.

CONCLUSIONS

Black-blood thrombus imaging has high SE, SP, and accuracy for DVT diagnosis both at 1.5 T and 3.0 T field strengths. This noninvasive diagnostic technique, which does not require the use of contrast agents, can be widely used in the clinical screening of DVT and follow-up after treatment.

Non-contrast-enhanced magnetic resonance imaging: Objective figures in differentiation between acute and chronic deep venous thrombosis in the lower extremities

BACKGROUND

Deep vein thrombosis is a severe health problem. Treatment options may differ between acute and chronic deep vein thrombosis. Thus, distinguishing acute from chronic deep vein thrombosis is essential for patients with deep vein thrombosis.Triggered angiography non-contrast enhanced is an innovative magnetic resonance imaging protocol that may provide objective evidence in differentiating acute from chronic deep vein thrombosis.

METHOD

We prospectively collected information on consecutive patients who had been evaluated through triggered angiography non-contrast enhanced magnetic resonance imaging for venous pathology in their lower extremities at a vascular wound care center in a tertiary hospital between April 2017 and January 2020. Patients included were divided into two groups with the onset time cutoff point of 21 days. All were undergone non-contrast-enhanced magnetic resonance imaging evaluation. Non-contrast-enhanced magnetic resonance imaging images were evaluated by a radiologist, and lower extremity venous thrombosis, collateral-vein development, and subcutaneous honeycombing were emphasized. Cohen's kappa coefficient was used to measure interrater agreement between the development of collateral veins, subcutaneous honeycombing, and symptom onset over 21 days.

RESULTS

Interrater agreement analysis revealed that the development of collateral veins was substantially correlated with the onset of symptoms over 21 days (Table 1). Additionally, the development of subcutaneous honeycombing detected through triggered angiography non-contrast enhanced magnetic resonance imaging also substantially agreed with the onset of symptoms over 21 days (Table 2).

CONCLUSION

The diagnostic power of triggered angiography non-contrast enhanced magnetic resonance imaging in deep vein thrombosis is rival to current gold standard, color Doppler sonography. Triggered angiography non-contrast enhanced magnetic resonance imaging provides objective information on onset timing in patients with deep vein thrombosis that could differentiate acute from chronic deep vein thrombosis and provides guidance for treatment planning.

DANTE-SPACE: a new technical tool for DVT on 1.5T MRI

The aim of the study was to compare CE-MRV with DANTE-SPACE on a 1.5T MRI system for the diagnosis of DVT. The patients were diagnosed with deep venous thrombosis of the lower extremities based on swelling, pain, and superficial varicose veins of the lower extremities. MRI examination confirmed the diagnosis. DANTE-SPACE images were obtained before the conventional contrast-enhanced MRV, which uses gadolinium. The scanning field started from the end of the inferior vena cava to the end of the ankle, divided into five observation segments, namely, the common iliac vein, external iliac vein, femoral vein, popliteal vein, and calf vein. The DANTE-SPACE and CE-MRV results were used for a consistency analysis. For the DANTE-SPACE and CE-MRV images, the signal intensity ratios of the thrombus/cavity and thrombus/muscle were calculated, and the ratio difference was compared using the paired t test. Twenty-six patients completed the examination; one of the patients underwent a right lower limb amputation, yielding a total of 255 lower limb vascular segments. The analysis of the DANTE-SPACE images showed that there were 14 iliac vein thromboses, 18 external iliac vein thromboses, 23 femoral vein thrombi, 21 popliteal vein thromboses, and 18 calf vein thromboses; these findings were consistent with the diagnostic results of CE-MRV. The ratio of the thrombus/cavity signal intensity measured in the DANTE-SPACE and CE-MRV images were as follows: 20.51 ± 12.96 vs. 0.51 ± 0.46; P < 0.05, n = 51; the difference was statistically significant. The ratio of the thrombus/muscle signal intensity measured on the DANTE-SPACE and CE-MRV images were as follows: 1.74 ± 0.57 vs. 0.99 ± 0.53; P < 0.05, n = 51; the difference was statistically significant. Compared with CE-MRV, DANTE-SPACE showed no significant difference in the ability to detect deep venous thrombosis of the lower extremities. DANTE-SPACE did not use contrast-enhancing agents and showed no evidence of inflammatory enhancement, and the display effect of small diameter veins was slightly poor. However, deep venous thrombosis of the lower extremities presents different levels of high signal in the DANTE-SPACE images, making it easy to identify and diagnose. It can also indicate the different components and age of the thrombus and help with the selection of a more accurate clinical treatment plan. MRI DANTE-SPACE is the preferred imaging modality for patients with deep venous thrombosis who are unable or unwilling to use gadolinium contrast agents.

Factors Influencing Elastographically Determined Remodeling of Venous Thrombi

OBJECTIVES

To verify whether elastographically determined remodeling of venous obliterating material formed during sclerotherapy is influenced by patient-specific factors.

METHODS

The study included 60 patients who underwent sclerotherapy for venous insufficiency. Elastographic parameters of obliterating material, including relative vascular cross sections (percent) with the highest (red), intermediate (green), and lowest elasticity (blue), determined 7 ± 1, 14 ± 2, and 21 ± 2 days after sclerotherapy, were analyzed against the patients' ages, sexes, physical activity levels, and pain severities.

RESULTS

The patients included 45 women and 15 men with a mean age ± SD of 51.2 ± 14.7 years. A significant correlation was observed between the age of the patients and the relative area of the vessel highlighted in red during the third control visit (R = 0.289; P = .025). The proportion of men in whom the elastographic structure of venous obliterating material during the second visit was classified as mixed was higher than that of women (66.7% versus 28.9%; P = .032). During the third visit, the proportion of patients with low physical activity in whom the elastographic structure of venous obliterating material was classified as fibrous turned out to be lower than the respective percentages of patients with moderate and high activity levels (12.0% versus 35.0% versus 46.7%; P = .045). However, none of these effects was observed systematically throughout the whole follow-up period.

CONCLUSIONS

The time to complete organization of venous obliterating material may be longer in older patients, women, and patients with lower levels of physical activity, but these factors seem to influence the thrombus structure solely at specific time points in its evolution. Nevertheless, they should be considered during elastographic assessments of thrombus age.

Deep vein sclerosis following sclerotherapy: Ultrasonic and d-dimer criteria

Objectives

The aim of sclerotherapy is to induce fibrosclerosis of superficial veins. We postulated that inadvertent entry of sclerosants into deep veins can result in sclerotic occlusion, deep vein sclerosis, a non-thrombotic process distinct from spontaneous deep vein thrombosis. The aim of this study was to assess the role of d-dimer in differentiating between deep vein sclerosis and deep vein thrombosis.

Methods

Proximal trunks of great and small saphenous veins were treated with endovenous laser ablation. Venous tributaries and perforators were treated with foam ultrasound guided sclerotherapy. Ultrasound studies of lower limb deep veins were performed before and one week after the procedures, to detect deep vein occlusions (DVOs). d-dimer levels were measured for DVOs and long-term ultrasound studies monitored the recanalisation rates.

Results

In a six-year period, 9143 procedures were performed in 1325 patients for bilateral varicose veins. This included 1124 endovenous laser ablation and 8019 foam ultrasound guided sclerotherapy procedures. A total of 259 DVOs (2.83%) were identified on ultrasound which included 251 deep vein sclerosis (2.74%), seven deep vein thrombosis (0.07%) and one endovenous heat-induced thrombosis (EHIT, 0.08%). d-dimer values <0.5 µg/mL excluded deep vein thrombosis s, 0.5–1.0 µg/mL were more likely to be associated with deep vein sclerosis and >1.0 µg/mL were a more likely to be associated with deep vein thrombosis. Lower sclerosant concentrations and higher foam volumes were associated with increased risk of DVO ( p <  .0001). No significant relationship was found between DVO and gender or thrombophilia. Deep vein thrombosis and EHIT cases but not deep vein sclerosis patients were anticoagulated. None had thromboembolic complications. Patients were followed up for a median of 299 days (37–1994 days). Recanalisation rates were 71.1% for deep vein sclerosis (92.3% competent) and 71.4% for deep vein thrombosis (60.0% competent).

Conclusions

Deep vein sclerosis is a relatively benign clinical entity distinct from deep vein thrombosis and does not require anticoagulation. Majority of affected veins on long-term follow-up regain patency and competence. d-dimer can be used to assist in differentiating deep vein sclerosis from deep vein thrombosis.

Application of the probit method for elastographic evaluation of venous obliterating material after sclerotherapy procedure

Purpose

Status after sclerotherapy constitutes a good clinical model for venous thrombosis with known age. The aim of this study was to compare elastographic parameters of material obliterating the great saphenous vein at 7-21 days after polidocanol sclerotherapy.

Material and methods

The study included 60 patients subjected to sclerotherapy due to venous insufficiency (45 women and 15 men, mean age 51.2 ± 14.7 years, range 27-77 years). Elastographic parameters of obliterating material: total area of vessel cross-section (mm²), relative areas (%) covered by tissues with highest, intermediate, and lowest elasticity, were determined 7 ± 1, 14 ± 2, and 21 ± 2 days post-sclerotherapy, respectively. Mean time to partial and complete organisation of the obliterating material was estimated during probit regression analysis.

Results

The relative area of vessel cross-section covered by tissues with the lowest elasticity underwent a statistically significant enlargement, either between the first and the second (Z = 6.725, p < 0.001) or between the second and the third control visit (Z = 6.717, p < 0.001). This corresponded to a change in the structure of the obliterating material from elastic during the first visit (in all patients) to mixed (fibro-elastic) or fibrous during the third visit (71.7% and 28.3% of patients, respectively). Mean time after which the obliterating material reached mixed and fibrous structure on elastographic images was estimated at 14.3 days and > 21 days, respectively.

Conclusions

Ultrasound elastography may accurately reflect the age of venous thrombosis in polidocanol sclerotherapy model. Mixed, fibro-elastic structure of a 14-day-old obliterating material visualised by elastography probably corresponds with chronic thrombus.

Ultrasound elastography is useful to distinguish acute and chronic deep vein thrombosis

Essentials Ultrasound elastography uses tissue deformation to assess the relative quantification of its elasticity. Compression and duplex ultrasonography may be unable to correctly determine the thrombus age. Ultrasound elastography may be useful to distinguish between acute and chronic deep vein thrombosis. The exact determination of the thrombus age could have both therapeutic and prognostic implications. BACKGROUND: Background Ultrasound elastography (UE) imaging is a novel sonographic technique that is commonly employed for relative quantification of tissue elasticity. Its applicability to venous thromboembolic events has not yet been fully established; in particular, it is unclear whether this technique may be useful in determining the age of deep vein thrombosis (DVT). Thus, the aim of this study was to assess the role of UE in distinguishing acute from chronic DVT. Methods Consecutive patients with a first unprovoked acute and chronic (3 months old) DVT of the lower limbs were analyzed. Patients with recurrent DVT or with a suspected recurrence were excluded. The mean elasticity index (EI) values of acute and chronic popliteal and femoral vein thrombosis were compared. The accuracy of the EI in distinguishing acute from chronic DVT was also assessed by measuring the sensitivity, specificity, positive and negative predictive values, and likelihood ratios. Results One-hundred and forty-nine patients (mean age 63.9 years, standard deviation 13.6; 73 males) with acute and chronic DVT were included. The mean EI of acute femoral DVT was higher than that of chronic femoral DVT (5.09 versus 2.46), and the mean EI of acute popliteal DVT was higher than that of chronic popliteal DVT (4.96 versus 2.48). An EI value of > 4 resulted in a sensitivity of 98.9% (95% confidence interval [CI] 93.3-99.9), a specificity of 99.1% (95% CI 94.8-99.9), a positive predictive value of 91.1% (95% CI 77.9-97.1), a negative predictive value of 98.6% (95% CI 91.3-99.9), a positive likelihood ratio of 13.23 (95% CI 93-653) and a negative likelihood ratio of 0.001 (95% CI 0.008-0.05) for acute DVT. Conclusions UE appears to be a promising technique for distinguishing between acute and chronic DVT. Larger prospective studies are warranted to confirm our preliminary findings.

Vascular ultrasound, the potential of integration of multiparametric ultrasound into routine clinical practice

Introduction

Ultrasound has traditionally been regarded as the first-line imaging modality for screening, diagnostic evaluation and monitoring treatment and disease progression of vascular pathology, including both the arterial and the venous branch of the vascular system. Albeit of its well-tolerated nature, wide availability and low cost, ultrasound above all, has the advantage of providing the clinician with clinically significant information related to both intraluminal irregularities and extravascular disease. Ultrasound has the potential not only to anatomically describe tissues but also to assess physiology by evaluating blood flow characteristics in real time.

Discussion

The already fundamental role of ultrasound has been even more expanded with the introduction of newer techniques like contrast-enhanced ultrasound, tissue-elastography and 3D ultrasound and the incorporation of research advances into clinical practice. The purpose of this review is to present and discuss some of the latest advances in the field of vascular ultrasound in attempt to illustrate how the adoption of multiparametric ultrasound into everyday clinical practice could address the patient's needs. Pathology and applications discussed include carotid and aortic disease, portal and peripheral venous abnormalities.

Conclusion

Widespread availability of modern technology in ultrasound devices has made the application of contrast-enhanced ultrasound, tissue elastography and 3D ultrasound feasible options, ready to contribute to the diagnostic performance of the ultrasonographic technique.

Is real-time elastography helpful to differentiate acute from subacute deep venous thrombosis? A preliminary study

PURPOSE

To detect and characterize changes in stiffness of thrombus in patients with acute and subacute deep venous thrombosis (DVT) by using real-time elastography (RTE).

METHODS

Fifty-eight patients with acute or subacute DVT were prospectively evaluated by B-mode sonography (US), color Doppler US (CDUS), and RTE. Two radiologists evaluated the thrombus echogenicity, compressibility, and recanalization of the affected vein, and thrombus stiffness in consensus. The thrombi were classified into 3 groups as soft, intermediate, and hard on RTE images.

RESULTS

The final study group consisted of 30 patients with acute DVT, among whom 10 were women (33%), and 19 patients with subacute DVT, among whom 6 were women (32%). The presence of hypoechoic thrombus, incompressible vein, and absence of recanalization on US and CDUS were significantly associated with acute DVT (P < .001 for all variables). The differences in elasticity pattern of the thrombi between acute and subacute DVT were not significant (P = .202).

CONCLUSION

Venous thrombus hardens with age; however, elastography pattern on RTE, in its present form, may not be able to differentiate acute DVT from subacute DVT.

Diagnostic Value of Virtual Touch Tissue Imaging Quantification for Evaluating Median Nerve Stiffness in Carpal Tunnel Syndrome

OBJECTIVES

To measure the shear wave velocity (SWV) of the median nerve by Virtual Touch tissue imaging quantification (VTIQ; Siemens AG, Erlangen, Germany) through the beginning of the carpal tunnel and to determine whether VTIQ could be used to diagnose carpal tunnel syndrome.

METHODS

This study recruited 49 consecutive patients (72 wrists) with a definitive diagnosis of carpal tunnel syndrome and 23 healthy volunteers (46 wrists). We measured the median nerve diameter and cross-sectional area by 2-dimensional sonography and the SWV by VTIQ. The interobserver variability was analyzed, and diagnostic values were evaluated by drawing a receiver operating characteristic curve.

RESULTS

The median nerve SWV was significantly higher in the carpal tunnel syndrome group (3.857 m/s) than the control group (2.542 m/s; P < .05). A 3.0-m/s SWV cutoff value revealed sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 83.3%, 91.3%, 93.8%, 77.8%, and 86.4%, respectively. The interobserver agreement was excellent for the SWV measurements.

CONCLUSIONS

The median nerve SWV at the carpal tunnel inlet is significantly higher in patients with carpal tunnel syndrome, for whom VTIQ appears to be a highly reproducible diagnostic technique.

Effect of pathological heterogeneity on shear wave elasticity imaging in the staging of deep venous thrombosis

Background

We aimed to observe the relationship between the pathological components of a deep venous thrombus (DVT), which was divided into three parts, and the findings on quantitative ultrasonic shear wave elastography (SWE) to increase the accuracy of thrombus staging in a rabbit model.

Methods

A flow stenosis-induced vein thrombosis model was used, and the thrombus was divided into three parts (head, body and tail), which were associated with corresponding observation points. Elasticity was quantified in vivo using SWE over a 2-week period. A quantitative pathologic image analysis (QPIA) was performed to obtain the relative percentages of the components of the main clots.

Results

DVT maturity occurred at 2 weeks, and the elasticity of the whole thrombus and the three parts (head, body and tail) showed an increasing trend, with the Young's modulus values varying from 2.36 ± 0.41 kPa to 13.24 ± 1.71 kPa; 2.01 ± 0.28 kPa to 13.29 ± 1.48 kPa; 3.27 ± 0.57 kPa to 15.91 ± 2.05 kPa; and 1.79 ± 0.36 kPa to 10.51 ± 1.61 kPa, respectively. Significant increases occurred on different days for the different parts: the head showed significant increases on days 4 and 6; the body showed significant increases on days 4 and 7; and the tail showed significant increases on days 3 and 6. The QPIA showed that the thrombus composition changed dynamically as the thrombus matured, with the fibrin and calcium salt deposition gradually increasing and the red blood cells (RBCs) and platelet trabecula gradually decreasing. Significant changes were observed on days 4 and 7, which may represent the transition points for acute, sub-acute and chronic thrombi. Significant heterogeneity was observed between and within the thrombi.

Conclusions

Variations in the thrombus components were generally consistent between the SWE and QPIA. Days 4 and 7 after thrombus induction may represent the transition points for acute, sub-acute and chronic thrombi in rabbit models. A dynamic examination of the same part of the thrombus may be helpful for improving the sensitivity and reproducibility of SWE for DVT diagnosis and staging.

Black-blood thrombus imaging (BTI): a contrast-free cardiovascular magnetic resonance approach for the diagnosis of non-acute deep vein thrombosis

BACKGROUND

Deep vein thrombosis (DVT) is a common but elusive illness that can result in long-term disability or death. Accurate detection of thrombosis and assessment of its size and distribution are critical for treatment decision-making. In the present study, we sought to develop and evaluate a cardiovascular magnetic resonance (CMR) black-blood thrombus imaging (BTI) technique, based on delay alternating with nutation for tailored excitation black-blood preparation and variable flip angle turbo-spin-echo readout, for the diagnosis of non-acute DVT. METHODS: This prospective study was approved by institutional review board and informed consent obtained from all subjects. BTI was first conducted in 11 healthy subjects for parameter optimization and then conducted in 18 non-acute DVT patients to evaluate its diagnostic performance. Two clinically used CMR techniques, contrast-enhanced CMR venography (CE-MRV) and three dimensional magnetization prepared rapid acquisition gradient echo (MPRAGE), were also conducted in all patients for comparison. All images obtained from patients were analyzed on a per-segment basis. Using the consensus diagnosis of CE-MRV as the reference, the sensitivity (SE), specificity (SP), positive and negative predictive values (PPV and NPV), and accuracy (ACC) of BTI and MPRAGE as well as their diagnostic agreement with CE-MRV were calculated. Besides, diagnostic confidence and interreader diagnostic agreement were evaluated for all three techniques.

RESULTS

BTI with optimized parameters effectively nulled the venous blood flow signal and allowed directly visualizing the thrombus within the black-blood lumen. Higher SE (90.4% vs 67.6%), SP (99.0% vs. 97.4%), PPV (95.4% vs. 85.6%), NPV (97.8% vs 92.9%) and ACC (97.4% vs. 91.8%) were obtained by BTI in comparison with MPRAGE. Good diagnostic confidence and excellent diagnostic and interreader agreements were achieved by BTI, which were superior to MPRAGE on detecting the chronic thrombus.

CONCLUSION

BTI allows direct visualization of non-acute DVT within the dark venous lumen and has the potential to be a reliable diagnostic tool without the use of contrast medium.

Advanced imaging in acute and chronic deep vein thrombosis

Deep venous thrombosis (DVT) affecting the extremities is a common clinical problem. Prompt imaging aids in rapid diagnosis and adequate treatment. While ultrasound (US) remains the workhorse of detection of extremity venous thrombosis, CT and MRI are commonly used as the problem-solving tools either to visualize the thrombosis in central veins like superior or inferior vena cava (IVC) or to test for the presence of complications like pulmonary embolism (PE). The cross-sectional modalities also offer improved visualization of venous collaterals. The purpose of this article is to review the established modalities used for characterization and diagnosis of DVT, and further explore promising innovations and recent advances in this field.