Color Doppler Ultrasound with Superb Microvascular Imaging Compared to Contrast-enhanced Ultrasound and Computed Tomography Angiography to Identify and Classify Endoleaks in Patients Undergoing EVAR

Pararenal Aortic Thrombus in Patients Undergoing Aortic Aneurysm Repair With Chimney Technique

INTRODUCTION

Chimney technique (chimney graft in abdominal aortic aneurysm repair [ChEVAR]) can be used to treat patients with pararenal aortic aneurysm unfit for open surgery and not suitable for custom-made fenestrated endograft. Since almost 1 in 5 patients undergo a reintervention within 3 years, features associated with higher risk of complications need to be investigated to tailor the follow-up schedule to each patient. The aim of our study was to assess the impact of mural thrombus in the pararenal aorta on perioperative and follow-up complications after ChEVAR.

METHODS

All consecutive patients undergoing ChEVAR at our center from 2015 to 2022 were included in this retrospective study. Collected variables included number of target vessels, stent graft size, presence, and severity of mural thrombus in pararenal aorta, which was reported with a scoring system from 0 to 10 based on thrombus type, thickness area, and circumferenceAnalyzed outcomes included perioperative and follow-up complications.

RESULTS

Thirty-one patients underwent ChEVAR during the study period. In 4 patients the indication for ChEVAR was type 1A endoleak after a previous endovascular aneurysm repair (EVAR). The number of target vessels was 1 in 17 patients (55%), 2 in 12 (39%), 3 in 1 (3%), and 4 in 1 (%). The mean mural thrombus score was 5.9. Complications were the following: type 1A endoleak in 4 cases (13%), chimney stent complications in 7 cases (23%) (including partial or total thrombosis, intrastent stenosis, displacement), renal function worsening during follow-up in 8 cases (26%). Overall survival was 90% at 2 years. Patients with severe mural thrombus showed lower freedom from ChEVAR-related complications (28% vs 59% at 2 years, p=0.023).

CONCLUSIONS

The presence of severe pararenal aortic mural thrombus was associated with lower freedom from ChEVAR-related complications in patients undergoing ChEVAR for pararenal aortic aneurysm repair. Further research with a larger number of patients is required to confirm these results.

CLINICAL IMPACT

The analysis of severity of mural thrombus in pararenal aorta, which was reported with a scoring system from 0 to 10 based on thrombus type, thickness area and circumference, can be useful and can be represent an important predictor element for complications in patient submitted to Chimney tecnique; in fact the presence of severe pararenal aortic mural thrombus was associated with lower freedom from ChEVAR-related complications in patients undergoing ChEVAR for pararenal aortic aneurysm repair. Then, in patient with pararenal aortic aneurysm, a preoperative evaluation could be focused on severity of mural thrombus to minimize the complications in ChEVAR tecnique or to change the surgical strategy.

Assessment of renal congestion in a rat model with congestive heart failure using superb microvascular imaging

PURPOSE

Renal congestion is a therapeutic target in congestive heart failure. However, its detailed evaluation in a clinical setting is challenging. This study sought to assess renal congestion impairment using superb microvascular imaging (SMI), a simple and accessible method.

METHODS

Dahl salt-sensitive rats, used as a model for congestive heart failure, underwent central venous pressure (CVP) measurements. Renal congestion was evaluated through measurements of renal medullary pressure (RMP) and assessment of renal perfusion using contrast-enhanced ultrasonography at both the early (control group) and heart failure phases (HF group). All rats were assessed with SMI. The region of interest (ROI) was set in interlobular vessels, interlobar vessels, and a combination of these areas. The area ratio was calculated from the color pixel count in the ROI divided by the total pixel count in the ROI. Intrarenal perfusion index (IRPI) was defined as (maximum area ratio-minimum area ratio) / maximum area ratio.

RESULTS

There were no significant differences in renal function and left ventricular ejection fraction between the two groups. CVP, time-to-peak (TTP) in the medulla, and RMP were higher in the HF group than in the control group. In the HF group, IRPI, evaluated in the interlobular vessels, was significantly higher than in the control group. IRPI was positively correlated with TTP in the medulla (p = 0.028, R = 0.60) and RMP (p < 0.001, R = 0.84), indicating that IRPI reflected renal congestion.

CONCLUSIONS

IRPI is a useful tool for assessing renal congestion in rats with congestive heart failure.

New microvascular ultrasound techniques: abdominal applications

Microvascular ultrasound (MVUS) is a new ultrasound technique that allows the detection of slow-velocity flow, providing the visualization of the blood flow in small vessels without the need of intravenous contrast agent administration. This technology has been integrated in the most recent ultrasound equipment and applied for the assessment of vascularization. Compared to conventional color Doppler and power Doppler imaging, MVUS provides higher capability to detect intralesional flow. A growing number of studies explored the potential applications in hepatobiliary, genitourinary, and vascular pathologies. Different flow patterns can be observed in hepatic and renal focal lesions providing information on tumor vascularity and improving the differential diagnosis. This article aims to provide a detailed review on the current evidences and applications of MVUS in abdominal imaging.

Endoleak Detection after Endovascular Aortic Repair via Coded-Excitation Ultrasound-A Feasibility Study

Endoleaks are the most common complication after endovascular aortic repair (EVAR). Their correct identification is one of the main objectives of surveillance protocols after EVAR. So far, computed tomography angiography (CTA), contrast-enhanced (CEUS) and Duplex ultrasound (DUS), as well as magnetic resonance angiography, have been investigated for their ability to detect endoleaks. In general, all technologies have distinct benefits and disadvantages, with CTA and CEUS emerging as the reference standard for surveillance after EVAR. However, they are both contrast-enhancer-dependent, and CTA additionally exposes patients to ionizing radiation. In the present study, we investigated B-Flow, a type of coded-excitation ultrasound that was specifically designed to optimize the visualization of blood flow, for its ability to detect endoleaks, and compared its performance to CEUS, CTA, and DUS. In total, 34 patients were included in the analysis that accumulated in 43 distinct B-Flow investigations. They underwent a total of 132 imaging investigations. Agreement between B-Flow and other imaging modalities was high (>80.0%), while inter-method reliability can be interpreted as good. However, with B-Flow, six and one endoleaks would have been missed compared to CEUS and CTA, respectively. Regarding endoleak classification, all metrics were lower but retained an adequate level of comparison. In a subset of patients requiring intervention, B-Flow had 100% accuracy regarding both endoleak detection and classification. Ultrasonography enables endoleak detection and classification without the need for pharmaceutical contrast enhancement or radiation. Ultrasound coded-excitation imaging in the application of B-Flow could further simplify surveillance after EVAR by offering adequate accuracy without requiring intravenous contrast enhancement. Our findings may promote subsequent investigations of coded-excitation imaging for endoleak detection and classification in the surveillance after EVAR.

Microvascular Flow Imaging: A State-of-the-Art Review of Clinical Use and Promise

Vascular imaging with color and power Doppler is a useful tool in the assessment of various disease processes. Assessment of blood flow, from infarction and ischemia to hyperemia, in organs, neoplasms, and vessels, is used in nearly every US investigation. Recent developments in this area are sensitive to small-vessel low velocity flow without use of intravenous contrast agents, known as microvascular flow imaging (MVFI). MVFI is more sensitive in detection of small vessels than color, power, and spectral Doppler, reducing the need for follow-up contrast-enhanced US (CEUS), CT, and MRI, except when arterial and venous wash-in and washout characteristics would be helpful in diagnosis. Varying clinical applications of MVFI are reviewed in adult and pediatric populations, including its technical underpinnings. MVFI shows promise in assessment of several conditions including benign and malignant lesions in the liver and kidney, acute pathologic abnormalities in the gallbladder and testes, and superficial lymph nodes. Future potential of MVFI in different conditions (eg, endovascular repair) is discussed. Finally, clinical cases in which MVFI correlated and potentially obviated additional CEUS, CT, or MRI are shown.

Comparison of superb microvascular imaging (SMI) quantified with ImageJ to quantified contrast-enhanced ultrasound (qCEUS) in liver metastases-a pilot study

BACKGROUND

The aim of the study was to compare methods for the assessment of vascularisation of liver metastases (LM) between superb microvascular imaging (SMI), contrast-enhanced ultrasound, and microvascular density (MVD).

METHODS

SMI results were quantified as the vascularisation quotient (VQ), based on a grey-scale analysis with ImageJ image software. Those results were compared to contrast-enhanced ultrasonography (CEUS) values, calculated with VueBox^®. MVD was measured with an anti-CD34 antibody.

RESULTS

This study included 13 patients with LM. The VQ showed a strong correlation with the quantified parameters of contrast-enhanced ultrasound. The parameters of quantified contrast-enhanced ultrasound compared with quantified SMI showed the following statistical correlations: peak enhancement (PE), in arbitrary unit (a.u.) (r=0.72104, P=0.0054), PE in Decibel (dB) (r=0.65918, P=0.00141), Wash-in- Area Under the Curve (WiAUC) in a.u. (r=0.63604, P=0.00194), Wash-in Perfusion-Index (WiPI) in a.u. (r=0.73337, P=0.0043), Wash-in Perfusion-Index (WiPI) in dB (r=0.65642, P=0.0194), Wash-in-Rate (WiR) in a.u. (r=0.7304, P=0.0036) and Wash-in-Rate (WiR) in dB (r=0.82897, P=0.0005).

CONCLUSIONS

Comparison of the two methods, SMI and contrast-enhanced ultrasound (CEUS), for quantitative assessment of vascularisation of LM showed good correlation. The contrast-independent Doppler technique SMI can qualitatively assess the vascularisation of LM.

EVAR Follow-Up with Ultrasound Superb Microvascular Imaging (SMI) Compared to CEUS and CT Angiography for Detection of Type II Endoleak

The aim of this study was to evaluate the usefulness of superb microvascular imaging (SMI) versus contrast-enhanced ultrasound (CEUS) and compared to computed tomography angiography (CTA) as a reference standard, for detection of type II endoleak during follow-up of endovascular abdominal aortic aneurysm repair (EVAR). Between April 2017 and September 2020, 122 patients underwent post-EVAR follow-up with CTA at 3 months and with ultrasound SMI and CEUS at 4 months from the EVAR procedure. Aneurysmal sac diameter and graft patency were evaluated; endoleaks were assessed and classified. Sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy were calculated both for SMI and CEUS and compared to CTA. Furthermore, the percentage of agreement and Cohen’s Kappa coefficient were calculated. CTA revealed 54 type II endoleaks. Ultrasound SMI and CEUS presented the same sensitivity (91.5%), specificity (100%), positive (100%), and negative (92.8%) predictive and accuracy (95.9%) value for detecting type II endoleak. The same percentage of agreement of 94.9% was found between SMI/CEUS, and CTA with a Cohen’s Kappa coefficient of 0.89. The diagnostic accuracy of SMI is comparable with CEUS in the identification of type II endoleaks after EVAR. Since SMI is less invasive, less expensive, and less time-consuming, this method may be considered to be a potential tool for monitoring patients after EVAR implantation.

An Innovative Ultrasound Technique for Early Detection of Kidney Dysfunction: Superb Microvascular Imaging as a Reference Standard

Background: Superb microvascular imaging (SMI) is an innovative ultrasound image processing technique that provides greater detail and better visualization of small branching vessels. We assume that SMI will provide sufficient information regarding the severity of chronic kidney disease (CKD) and reflecting histological changes. Aims: The aims was to assess the capabilities of SMI imaging regarding the early detection of kidney dysfunction and renal fibrosis in comparison to the reference standard renal biopsy for the early diagnosis of kidney fibrosis. Methods: SMI was performed in patients (n = 52) with CKD stage 2–5, where some of them underwent biopsy proven CKD and fibrosis as part of the diagnosis. In addition, biochemical tests were performed, including kidney function tests, urine collection for proteinuria, and the estimation of GFR by MDRD or CKD-EPI eGFR in CKD patients and healthy controls (n = 17). All subjects underwent SMI, where vascularity is expressed as the SMI index (a low index reflects low vascularity/fibrosis and vice versa). Results: The SMI vascular index was significantly lower in CKD patients as compared with healthy controls (72.2 ± 12.9 vs. 49.9 ± 16.7%, p < 0.01). Notably, a moderate correlation between the SMI index and eGFR was found among the CKD patients (r = 0.56, p < 0.001). Similarly, a strong correlation was found between SCr and the SMI index of the diseased subjects (r = −0.54, p < 0.001). In patients who underwent renal biopsy, the SMI index corresponded with the histological alterations and CKD staging. Conclusions: This study demonstrated that SMI imaging may be utilized in CKD patients of various stages for the evaluation of chronic renal morphological changes and for differentiation between CKD grades.

Relationship Between Serum Lipid Profiles and Carotid Intraplaque Neovascularization in a High-Stroke-Risk Population: A Cross-Sectional Study in China

Background

Evidence of the association between serum lipid profiles and intraplaque neovascularization (IPN) is still limited. We aimed to study the value of a novel Doppler method, superb microvascular imaging, in correlating serum lipid profiles and evidence of IPN in a population with a high risk of stroke.

Methods and Results

A community‐based cross‐sectional study was conducted in Beijing, China. Residents (aged ≥40 years) underwent questionnaire interviews, physical examinations, and laboratory testing in 2018 and 2019. Subjects with a high risk of stroke were then selected. Standard carotid ultrasound and carotid plaque superb microvascular imaging examinations were then performed on the high–stroke‐risk participants. Logistic regression was used to evaluate the relationship between serum lipid profiles and carotid plaque IPN. Overall, a total of 250 individuals (mean age, 67.20±8.12 years; 66.4% men) met the study inclusion criteria. Superb microvascular imaging revealed carotid plaque IPN in 96 subjects (38.4%). Subjects with IPN were more likely to be current smokers (34.0% versus 46.9%, P=0.046), and their identified carotid plaques were much thicker (2.35±0.63 mm versus 2.75±0.80 mm, P=0.001). Serum lipids, including total cholesterol, non–high‐density lipoprotein cholesterol, and low‐density lipoprotein cholesterol were positively associated with the presence of IPN (4.33±1.00 mmol/L versus 4.79±1.12 mmol/L, P=0.001; 2.96±0.92 mmol/L versus 3.40±1.01 mmol/L, P=0.001; 2.18±0.76 mmol/L versus 2.46±0.80 mmol/L, P=0.005, respectively), and after adjustment for other confounders, the positive relationship remained significant. Furthermore, non–high‐density lipoprotein cholesterol (odds ratio, 2.62 [95% CI, 1.35–5.06]) was significantly associated with the presence of carotid plaque IPN even after adjusting for low‐density lipoprotein cholesterol.

Conclusions

Total cholesterol, non–high‐density lipoprotein cholesterol, and low‐density lipoprotein cholesterol were positively associated with the presence of carotid IPN in a Chinese high–stroke‐risk population. Further prospective studies should be conducted to better understand how much finding IPN adds to current stroke prediction tools.

Role of CEUS in Vascular Pathology

In recent years, the implementation of contrast-enhanced ultrasound (CEUS) in clinical practice has opened new horizons in the arterial pathologies research field, since this technique is able to supply new sets of data that can be crucial in patient management. The main applications of CEUS in the arterial system are the detection, characterization, and follow-up of carotid plaques and endoleaks after EVAR. Other situations in which CEUS was demonstrated to be a useful tool are large vessel vasculitis, dissections, and untreated aneurysms. In carotid atherosclerosis CEUS is not only able to acquire quantitative data about stenosis but also to perform a qualitative assessment of the plaque. The most important plaque features that CEUS is able to depict are ulceration, neovascularization, and the presence of inflammatory infiltrates. All of these factors contribute to plaque vulnerability. Thus, CEUS is crucial in order to allow better risk stratification and management of patients. In follow-up after EVAR, CEUS shows sensitivity and specificity values similar to CTA while ensuring several advantages, such as lower cost and the absence of ionizing radiation and nephrotoxic agents. Moreover, CEUS is able to offer real-time evaluation of endoleaks and thus is a useful tool in cases that are ambiguous on CTA. Most limitations are patient-related and are the same as in all other ultrasound techniques, such as high BMI and meteorism.

Diagnostic utility of superb microvascular imaging in depiction of corkscrew collaterals in Buerger's disease

PURPOSE

To evaluate the corkscrew collaterals in Buerger's disease by superb microvascular imaging (SMI) and power Doppler ultrasonography (PDU).

METHODS

We evaluated with SMI and PDU 14 patients with Buerger's disease in whom corkscrew collaterals had been identified on digital subtraction angiography (DSA). Corkscrew collaterals were classified on DSA and PDU based on their size and morphology.

RESULTS

A total of 17 vascular regions of collateral vessel formation were assessed. Based on DSA classification, there were three cases of type I collaterals (arterial diameter of >2 mm with large helical pattern), seven cases of type III collaterals (arterial diameter of 1-1.5 mm with small helical pattern), and seven cases of type IV collaterals (arterial diameter of <1 mm with tiny helical pattern). On PDU, all type I collaterals on DSA appeared as "large snake" images, all type III collaterals on DSA appeared as "small snake" images, and all type IV collaterals on DSA appeared as dots. SMI imaging, both in color and monochrome mode, provided superior demonstration of the continuity of the vessel of large or small "snake" images. In cases appearing as dot pattern on PDU, color SMI was able to show continuity of the flow signal as a helical pattern.

DISCUSSION

SMI is a promising new Doppler imaging technique that is superior to conventional power Doppler imaging in depiction and identification of corkscrew collaterals in Buerger's disease.

Cerebral superb microvascular imaging in preterm neonates: in vivo evaluation of thalamic, striatal, and extrastriatal angioarchitecture

PURPOSE

To explore the potential of superb microvascular imaging (SMI) in visualizing brain microvessels in preterm neonates of different gestational ages (GA).

METHODS

In this retrospective, observational pilot study, 15 preterm newborns were equally divided into GA groups: extremely (GA < 28 weeks), very (28-31 weeks), and moderate to late (32-37 weeks) preterm. All patients underwent conventional transcranial ultrasounds during the first day of life following the American Institute of Ultrasound in Medicine practice guidelines. SMI was then performed; based on their SMI morphology and location, brain microvessels were classified as extrastriatal (cortical and medullary), striatal, or thalamic. Two examiners independently classified vessels as visible or invisible. To assess the association between vessel visibility and GA, binomial logistic regression analysis (separate for each microvessel group) was performed, taking visibility as a dependent variable and both examiners and GA as predictor variables.

RESULTS

A statistically significant difference among GA groups was found in sex (P = 0.030), birth weight (P = 0.007), and Apgar score within 1 min after birth (P = 0.024). Microvascular visibility increased with GA for superficial vessels (P < 0.05 for both cortical and medullary), while striatal and thalamic vessels were visible in all neonates irrespective of their GA.

CONCLUSIONS

SMI technology shows promise to assess brain microvasculature in preterm neonates, even potentially providing data on early brain development.

Narrative review of multiparametric ultrasound in parotid gland evaluation

Disorders affecting parotid gland represent a heterogeneous group comprising congenital, inflammatory and neoplastic diseases which show a focal or diffuse pattern of appearance. The differentiation of neoplastic from non-neoplastic conditions of parotid glands is pivotal for the diagnostic imaging. Frequently there is evidence of overlapping between the clinical and the imaging appearance of the various pathologies. The parotid gland is also often object of study with the combination of different techniques [ultrasound-computed tomography-magnetic resonance imaging (US-CT-MRI), ex.]. Compared to other dominant methods of medical imaging, US has several advantages providing images in real-time at lower cost, and without harmful use of ionizing radiation and of contrast enhancement. B-mode US, and the microvascular pattern color Doppler are usually used as first step evaluation of parotid lesions. Elastography and contrast-enhanced US (CEUS) has opened further possible perspectives to improve the differentiation between benign and malignant parotid lesions. The characterization of the parotid tumors plays a crucial role for their treatment planning and for the prediction of possible surgical complications. We present, here an updated review of the most recurrent pathologies of parotid gland focusing on the diagnostic power of multiparametric US including CEUS and ultrasound elastography (USE); limitations, advantages and the main key-points will be presented.

Application of ultrasound in the diagnosis of gastrointestinal tumors

Gastrointestinal tumors are common tumors in the digestive system. Early diagnosis of gastrointestinal tumors is the key to improve prognosis and curative effect of patients with tumors. Compared with other methods of examination and diagnosis, ultrasound examination has the advantages of simple operation, non-invasive, economical, and repeatable operation. With the advancement of ultrasound technology and the development of ultrasound contrast agents, ultrasound examination is more and more applied to gastrointestinal examination. Ultrasound cannot only observe the gastrointestinal wall, but also evaluate the surrounding lesions and metastases, as well as preoperative analysis and postoperative follow-up of gastrointestinal tumors. We reviewed the diagnostic applications of ultrasound in gastrointestinal tumors.

Contrast-enhanced ultrasound (CEUS) in the diagnostic evaluation of popliteal artery aneurysms, a single-center study

BACKGROUND

Popliteal artery aneurysms (PAA) are the most common peripheral artery aneurysms. Most common cause is arteriosclerosis. Acute thromboembolic limb ischemia and rupture of the PAA depict severe complications. Diagnostic tools for identifying PAAs are (Doppler) ultrasound, CT/MR angiography and DSA.

PURPOSE

The aim of the present retrospective single-center study is to assess the application and safety of CEUS for assessing untreated and treated PAAs.

MATERIALS AND METHODS

13 patients were included in this study on whom CEUS was performed between 2007-2016. CEUS examinations were performed and interpreted by an experienced single radiologist (EFSUMB Level 3).

RESULTS

CEUS allowed for the detection of PAAs in all cases. CEUS allowed for detection of partial thrombosis of PAA in 7/8 of untreated patients, proper exclusion of PAA upon femoro-popliteal bypass in 3 patients, incomplete exclusion of PAA upon femoro-popliteal bypass in 1 patient and ruling out of in-stent stenosis in 1 patient.

CONCLUSION

CEUS is a useful and safe tool for in real-time evaluation of PAAs in the pre-/post-treatment status. In addition to conventional (Doppler) ultrasound and as an alternative tool to more elaborate imaging modalities, CEUS might be integrated in the future diagnostic work-up and follow-up of PAA patients.

Role of Superb Microvascular Imaging in Differentiating Between Malignant and Benign Solid Breast Masses

INTRODUCTION

The purpose of this study was to evaluate the diagnostic performance of superb microvascular imaging (SMI) in breast lesions.

MATERIALS AND METHODS

Eighty-five solid breast lesions were studied with color Doppler flow imaging (CDFI), power Doppler imaging (PDI), monochromatic SMI (mSMI), and contrast-enhanced ultrasonography (CEUS). The penetrating vessels (PVs) and microvascular morphologic and distribution features of the breast tumors were evaluated for each modality.

RESULTS

The diagnostic accuracies of CDFI, PDI, mSMI, and CEUS were calculated and compared. Surgical pathologic analysis showed 47 benign and 38 malignant lesions. Compared with CDFI and PDI, mSMI and CEUS detected more PVs in breast lesions. The microvascular architecture showed significant differences between benign and malignant lesions. Benign lesions mainly displayed avascular, line-like, and branch-like patterns, and malignant lesions tended to display root hair-like and crab claw-like patterns. mSMI and CEUS identified more root hair-like and crab claw-like patterns in malignant lesions than CDFI and PDI. The sensitivity, negative predictive value, and accuracy of mSMI findings in diagnosing malignancy based on PVs and vascular patterns were both higher than those of CDFI and PDI.

CONCLUSIONS

mSMI is equal to CEUS and superior to CDFI and PDI in identifying microvascular and discriminating malignant and benign breast masses.

Angio PLanewave UltraSensitive Imaging (Angio PL.U.S.) as an Innovative Doppler Ultrasound Technique with a Potential to follow up Endoleaks after Endovascular Aneurysm Repair (EVAR)

The aim of the study was to evaluate the effectiveness of Angio PLanewave UltraSensitive imaging (Angio PL.U.S.) as an alternative to contrast-enhanced ultrasound (CEUS) and computed tomography angiography (CTA) for endoleak detection and classification in patients after endovascular aneurysm repair. A total of 28 patients underwent a post-endovascular aneurysm repair follow-up with color Doppler ultrasound, power Doppler ultrasound, CEUS, Angio PL.U.S and CTA examinations. CTA revealed 17 endoleaks in 14 patients (50%): 3 type Ia, 13 type II and 1 type III. There were no differences between Angio PL.U.S. and CEUS in terms of sensitivity, specificity or accuracy (93%, 100% and 97%). We did not observe any statistically significant differences between CTA, CEUS and Angio PL.U.S. in terms of the endoleak identification ability. Angio PL.U.S. may be considered as a potential tool to follow-up patients after endovascular aneurysm repair implantation, especially in patients who cannot be examined with CTA or CEUS.

Innovations in Vascular Ultrasound

There are several vascular ultrasound technologies that are useful in challenging diagnostic situations. New vascular ultrasound applications include directional power Doppler ultrasound, contrast-enhanced ultrasound, B-flow imaging, microvascular imaging, 3-dimensional vascular ultrasound, intravascular ultrasound, photoacoustic imaging, and vascular elastography. All these techniques are complementary to Doppler ultrasound and provide greater ability to visualize small vessels, have higher sensitivity to detect slow flow, and better assess vascular wall and lumen while overcoming limitations color Doppler. The ultimate goal of these technologies is to make ultrasound competitive with computed tomography and magnetic resonance imaging for vascular imaging.

Comparison of three ultrasonographic examinations on the synovial membrane vascularity of RA patients

Rheumatoid arthritis (RA) is a systemic autoimmune disease involving multiple joints and often involves the small joints, and the lesions are symmetric, invasive, and disabling. Synovial blood flow in patients with RA was compared using color Doppler flow imaging (CDFI), power Doppler ultrasound (PDUS), and superb microvascular imaging (SMI) to determine the application value of SMI in synovial vasospasm of knee joints. The blood flow signals of the suprapatellar recess in the knee joints of 41 RA patients (49 knees) were measured prior to undergoing total knee arthroplasty (TKA), recorded, and graded by CDFI, PDUS, and SMI. The results of the three ultrasound examination methods were compared and analyzed. The SMI grading was compared with the pathologic grade of the synovial membrane. Forty-one patients underwent 49 TKAs. The display rate of the synovial blood flow signal was 93.9% in the CDFI model, 97.9% in the PDUS model, and 100% in the SMI model. There were statistically significant differences in the results between the three ultrasound examination methods (H_C = 11.84, P < 0.05). The consistency of the SMI and pathologic grades of synovial membranes was better than the other methods (kappa = 0.639, P < 0.05). Compared with CDFI and PDUS, the signal of synovia flow detected by SMI was significantly higher in RA patients. SMI classification had a better consistency with the pathologic grade, and SMI has application value in assessing the activity of RA.

Inferior epigastric artery pseudoaneurysm secondary to port placement during a robot-assisted laparoscopic radical cystectomy

Pseudoaneurysm occurs when the artery wall is damaged and the blood is contained by the surrounding tissues with the eventual formation of a fibrous sac communicating with the artery. We report a case of a 74-year-old man with inferior epigastric artery (IEA) pseudoaneurysm secondary to an 8-mm port placement during a robot-assisted laparoscopic radical cystectomy with ureteroileocutaneostomy. The pseudoaneurysm was initially diagnosed by contrast-enhanced ultrasound (CEUS); subsequently, a computed tomography (CT) scan and an angiography test were performed. The pseudoaneurysm was then treated successfully with embolization of the inferior epigastric artery. Awareness of this rare complication is of clinical importance to avoid excessive morbidity of affected individuals.

Insight into Dunbar syndrome: color-Doppler ultrasound findings and literature review

Dunbar syndrome, also known as median arcuate ligament syndrome, is a rare clinical condition due to the external compression of the celiac trunk by the median arcuate ligament causing abdominal angina. We report a case of Dunbar syndrome and its borderline imaging findings focused on the crucial diagnostic role of color-Doppler ultrasound. We also reviewed the current literature, delineating the clinical manifestations and the diagnostic workup of the Dunbar syndrome with the objective to increase the knowledge of this clinical entity as a cause of postprandial abdominal pain and to underline the pivotal role of color-Doppler ultrasound to avoid incorrect or delayed diagnosis.

Assessment of Carotid Intraplaque Neovascularization Using Superb Microvascular Imaging in High Risk of Stroke Individuals: Results From a Community-Based Study

Background: Improved stroke risk stratification may improve stroke prevention. We aimed to study the value of a novel Doppler method, superb microvascular imaging (SMI), in correlating plaque thickness and evidence of intra-plaque neovascularization with a history stroke and TIA involving any cerebrovascular territory among community residents considered at high stroke risk.

Methods: We selected residents aged at least 40 years from the Donghuashi community in China who had at least three stroke risk factors (including a history of stroke or TIA) and carotid plaque thickness of at least 1.5 mm (but without heavy calcification) and no history of carotid endarterectomy or stenting. In this cross-sectional study, each subject underwent carotid plaque examination with standard ultrasound and SMI. SMI evidence of plaque neovascularization was categorized as none or mild (Grade 1) or moderate or marked (Grade 2) and correlated with past history of stroke or TIA.

Results: A total of 131 individuals (mean age 69 ± 8 years, 63% male) met the study inclusion criteria. SMI revealed no or mild neovascularization in 74 subjects (56.5%) and moderate or marked neovascularization in 57 subjects (43.5%). Subjects with moderate or marked neovascularization were more likely to have a history of any territory stroke or TIA, 43.9 vs. 17.6% (P = 0.001). Multivariate logistic regression analyses showed a thicker plaque (odds ratio: 2.272, 95% CI: 1.351–3.822, P = 0.002) and a history of stroke or TIA (odds ratio: 4.017, 95% CI: 1.719–9.387, P = 0.001) significantly correlated with evidence of moderate to marked intra-plaque neovascularization.

Conclusions: Moderate to marked intraplaque neovascularization detected by SMI was more likely in subjects with a history of any territory stroke or TIA or thicker plaque. This indicates a potential new role of SMI in stratifying future risk of stroke or other arterial disease complications.

The utility of superb-microvascular imaging for evaluating the full length of carotid artery stents

Transoral carotid ultrasonography (TOCU) is a powerful tool for evaluating internal carotid artery (ICA) lesions located from the carotid bifurcation up to the level of the second cervical vertebra. Superb-microvascular imaging (SMI) is a new Doppler imaging technique whose algorithm analyze tissue movements to minimize motion artifacts by eliminating clutter signals. SMI significantly reduces motion artifacts and allows visualization of low-velocity blood flow even in minute vessels. TOCU with SMI produces clear intraluminal image of the distal extracranial ICA, which is not possible with conventional carotid artery ultrasonography (CUS). CUS with SMI and TOCU with SMI were performed in a patient with a history of carotid artery stenting for symptomatic left ICA stenosis, providing images of the full length of the stents with intimal hyperplasia.

A Narrative Review on Contrast-Enhanced Ultrasound in Aortic Endograft Endoleak Surveillance

Endovascular repair of abdominal aortic aneurysms have been performed successfully since 1991. However, 20% to 50% of these patients may develop an endoleak or continued aneurysmal sac expansion or perfusion despite stent graft coverage. Current recommendations suggest lifelong surveillance with computed tomographic angiography (CTA) at least 1 month after intervention and yearly after that. In select patients with a stable aneurysm sac on computed tomography performed 1 year after treatment, future screening could be performed with ultrasonography. However, color Doppler ultrasound can fail to detect as many as 31% of endoleaks. Contrast-enhanced ultrasound (CEUS) provides an alternative approach to excluded aneurysm sac follow-up imaging. The Society for Vascular Surgery notes a need for further research on the role of CEUS in endovascular aortic repair surveillance. The European Federation of Societies for Ultrasound in Medicine and Biology suggests that early results are promising. Meta-analyses report pooled sensitivities and specificities of CEUS compared with CTA for the detection of endoleak between 89% and 98% and 86% and 88%, respectively. Owing to the dynamic flow information it provides, CEUS may actually be more sensitive than CTA at detection and characterization in select circumstances. Challenges with adoption, patient selection, and operator dependency remain, but current and future research suggests a role for CEUS in endoleak surveillance.

Superb Microvascular Imaging Compared with Contrast-Enhanced Ultrasound for Assessing Laser Ablation Treatment of Benign Thyroid Nodules

Purpose

To compare superb microvascular imaging (SMI) with contrast-enhanced ultrasonography (CEUS) for evaluating the ablation of benign thyroid nodules.

Methods

225 Patients with 256 benign thyroid nodules underwent conventional ultrasound, color Doppler flow imaging (CDFI), CEUS, and SMI before and after laser ablation. They were routinely followed up at 1, 3, 6, and 12 months. The volume and volume reduction rate of the ablated nodules was calculated.

Results

On SMI, the complete ablated nodules had no microvascular perfusion, while the incompletely ablated nodules had microvascular perfusion at the edge of the nodule. The percentages of the detected incompletely ablated nodules of SMI (37/256, 14.45%) and CEUS (41/256, 16.02%) were comparable, and both were significantly higher than CDFI (P< 0.001). CEUS was used as the criterion to determine whether the nodules were completely ablated. The sensitivity, specificity, and accuracy of SMI for detecting incompletely ablated nodules were 90.2, 98.2, and 100%, respectively. The volume of ablated nodules, as measured on ultrasound, was greater than that on CEUS or SMI (both P< 0.001), while CEUS and SMI were similar. The average volume reduction rate of nodules at 1, 3, 6, and 12 months was 40.25, 54.98, 76.83, and 95.43%, respectively.

Conclusion

SMI sensitively detected the capillaries within residual thyroid nodules after laser ablation. The lesion size and detection rate of incompletely ablated nodules via SMI was consistent with that of CEUS. SMI may replace CEUS in certain cases for monitoring the curative effect of laser ablation for benign thyroid nodules.

Superb Micro-vascular Imaging (SMI): a Doppler ultrasound technique with potential to identify, classify, and follow up endoleaks in patients after Endovascular Aneurysm Repair (EVAR)

Purpose

The aim of the study was to assess the effectiveness of Superb Micro-vascular Imaging (SMI) as an alternative to Contrast-Enhanced Ultrasound (CEUS) and Computed Tomography Angiography (CTA) for endoleak detection and classification in patients followed up after endovascular abdominal aortic aneurysm repair (EVAR).

Materials and methods

From May 2015 to January 2017, 30 patients underwent post-EVAR follow-up with Color Doppler Ultrasound (CDUS), CEUS, SMI, and CTA examinations. Aneurysmal sac diameter and graft patency were evaluated; endoleaks were identified and classified. Sensitivity, specificity, and accuracy values were calculated for each of the four diagnostic methods of endoleak detection. A percentage of agreement and Cohen’s Kappa coefficient were calculated for comparison of methods in terms of endoleak identification.

Results

CTA revealed fifteen endoleaks (50%): three type Ia, nine type II, and three type III. The sensitivity of CDUS, CEUS, and SMI relative to CTA was 27%, 100%, and 100%, respectively. Specificity was 93%, 93%, and 93%, respectively. Accuracy was 60%, 97%, and 97%, respectively. There were no differences between SMI and CEUS in terms of sensitivity, specificity, or accuracy (100%, 93%, and 97%). We do not observe statistically significant differences between CTA, CEUS, and SMI concerning endoleak identification ability. The weakest method in endoleak identification was CDUS.

Conclusions

The analysis showed that SMI is effective, repeatable, and comparable with the CEUS modality in identification endoleaks after EVAR; it may be considered as a potential tool to monitor patients after EVAR implantation, especially those with renal insufficiency or with an allergy to any contrast media.

Microvessel ultrasound of neonatal brain parenchyma: feasibility, reproducibility, and normal imaging features by superb microvascular imaging (SMI)

Objectives

To evaluate the feasibility and reproducibility of superb microvascular imaging (SMI) of the neonatal brain and to describe normal imaging features.

Methods

We performed transcranial ultrasound with SMI in 19 healthy term-born neonates. SMI was done according to a structured examination protocol, using two linear 18 MHz and 14 MHz transducers. Superficial and deep scans were acquired in the coronal and sagittal planes, using the left and right superior frontal gyri as anatomical landmarks. All SMI views were imaged by monochrome and colour SMI and evaluated with respect to visibility of extrastriatal (i.e. cortical and medullary) and striatal microvessels.

Results

We have described normal morphologic features of intraparenchymal brain microvasculature as “short parallel” cortical vessels, “smoothly curved” medullary vessels, and deep striatal vessels. In general, SMI performance was better on coronal views than on sagittal views. On superficial coronal scans, cortical microvessels were identifiable in 90–100%, medullary microvessels in 95–100%. On deep scans, cortical and medullary microvessels were visible in all cases, while striatal microvessels were identifiable in 71% of cases.

Conclusions

Cerebral SMI ultrasound is feasible and well-reproducible and provides a novel non-invasive imaging tool for the assessment of intraparenchymal brain microvasculature (extrastriatal and striatal microvessels) in neonates without the use of contrast.

Key Points

• Superb microvascular imaging (SMI) of the neonatal brain is feasible and reproducible.

• SMI depicts extrastriatal and striatal microvessels.

• SMI detects two types of extrastriatal microvessels: cortical and medullary.

Electronic supplementary material

The online version of this article (10.1007/s00330-018-5743-1) contains supplementary material, which is available to authorized users.

Intraplaque Microvascular Flow Signal in Superb Microvascular Imaging and Magnetic Resonance Imaging Carotid Plaque Imaging in Patients with Atheromatous Carotid Artery Stenosis

Carotid artery atherosclerosis is one of the major risk factors for ischemic stroke. Intraplaque neovascularization (IPN) is one of the steps toward the development of vulnerable plaque. Superb microvascular imaging (SMI) is a new ultrasonographic technique for visualizing low-velocity and microvascular flow by clutter suppression to extract flow signals from large to small vessels and enables visualization of intraplaque microvascular flow (IMVF) without echo contrast media. We aimed to investigate the association between IMVF signal in SMI and MRI plaque imaging among patients with atherosclerotic carotid stenosis. We prospectively enrolled patients (>18 years old) with mild to severe carotid stenosis (more than 50% in cross-sectional area) diagnosed by carotid ultrasonography between August 2017 and April 2018, irrespective of sex and history of stroke. A total of 40 patients (31 men, 9 women; mean age, 75.1 ± 10.0 years) were enrolled. SMI revealed IPN findings in 21 patients. SMI clearly visualized the direction of pulsatile flow movement in microvessels and IPN was easily classified into the two types of Type V (n=2) and Type E (n=19). Multivariate logistic regression analysis presented that microvascular flow signal in carotid plaque on SMI was identified as a significant predictor of intraplaque hemorrhage as evaluated by MRI (OR, 8.46; 95%CI, 1.44-49.9; p=0.018). This study demonstrated a significant association between the presence of IMVF signal in SMI and intraplaque hemorrhage characterized by high-intensity lesions on MRI T1-FFE images.

The utility of superb microvascular imaging for the detection of deep vein thrombosis

Superb microvascular imaging (SMI) reduces motion artifacts significantly and allows visualization of low-velocity blood flow in vessels; thus, thrombi are clearly demonstrated compared to conventional B-mode and color Doppler imaging. Ultrasonographic images of the lower extremities of a 69-year-old woman with acute ischemic stroke complicated with deep vein thrombosis (DVT) are presented. Because SMI allows visualization of low-velocity blood flow, echo contrast between the thrombus and the surrounding flow makes it possible to clearly visualize the thrombus. SMI is a useful method to evaluate DVT, especially early after thrombus formation when it is difficult to delineate size and length because of echolucency.

Thyroid Imaging Reporting and Data System Score Combined with the New Italian Classification for Thyroid Cytology Improves the Clinical Management of Indeterminate Nodules

The new Italian cytological classification (2014) of thyroid nodules replaced the TIR3 category of the old classification (2007) with two subclasses, TIR3A and TIR3B, with the aim of reducing the rate of surgery for benign diseases. Moreover, thyroid imaging reporting and data system (TI-RADS) score appears to ameliorate the stratification of the malignancy risk. We evaluated whether the new Italian classification has improved diagnostic accuracy and whether its association with TI-RADS score could improve malignancy prediction. We retrospectively analyzed 70 nodules from 70 patients classified as TIR3 according to the old Italian classification who underwent surgery for histological diagnosis. Of these, 51 were available for cytological revision according to the new Italian cytological classification. Risk of malignancy was determined for TIR3A and TIR3B, TI-RADS score, and their combination. A different rate of malignancy (p = 0.0286) between TIR3A (13.04%) and TIR3B (44.44%) was observed. Also TI-RADS score is significantly (p = 0.003) associated with malignancy. By combining cytology and TI-RADS score, patients could be divided into three groups with low (8.3%), intermediate (21.4%), and high (80%) risk of malignancy. In conclusion, the new Italian cytological classification has an improved diagnostic accuracy. Interestingly, the combination of cytology and TI-RADS score offers a better stratification of the malignancy risk.