Initial Experience of Superb Microvascular Imaging for Key Cardiac Views in Foetal Assessment before 15 Weeks Gestation

Abstract

Background: In the first trimester, ultrasound confirmation of normal or abnormal cardiac anatomy is difficult. B-mode and colour flow Doppler (CFD) are used to assess the foetal heart. Superb microvascular imaging (SMI) can visualise blood flow within the heart and vessels in early gestation. Objective: We report an initial experience of SMI for visualisation of normal and abnormal cardiac anatomy in the first trimester. Methods: Transabdominal foetal echocardiography was performed between 11 + 6 and 14 + 3 weeks (Aplio 500 US system, Toshiba Medical Systems, Tokyo, Japan) from January 2017 to December 2017. All scans were performed at a tertiary foetal cardiology unit. To assess the potential utility of the technique for early gestation screening, normal scans were reviewed by foetal medicine trainees with respect to the B-mode, CFD and SMI. Three key views were selected to compare modalities: the 4-chamber view, outflow tracts and the 3-vessel and trachea view (VTV). Visualisation rates of key echocardiographic features of significant cardiac abnormalities by SMI were reviewed. Results: Fifty-five normal echocardiograms and 34 cardiac abnormalities were included. In the normal heart, when B-mode, CFD and SMI were assessed separately, SMI had the highest rate of visualisation of 4-chamber, outflow tracts and 3-VTV (93, 85 and 83%, respectively). Intra-observer reliability was moderate for SMI of the 3 standard views (kappa 1, 0.64 and 0.64); interobserver for 4-chamber and outflow tract views was moderate (kappa 0.64 and 0.77). In 29/34 abnormal cases, SMI showed key features, enhancing greyscale visualisation. Conclusion: SMI has potential to become a useful, complementary modality for early foetal echocardiography. Further prospective studies are warranted to establish the place of the technique in assessment of the first trimester foetal heart.

A case of ventricular noncompaction associated with heterotaxy and atrioventricular block diagnosed at 15 weeks of gestation using superb microvascular imaging

“…Jabak et al reported that intracardiac structures could be more clearly visualized by SMI at less than 15 weeks of gestation compared with conventional color Doppler and B-mode methods, resulting in "virtual" contrast imaging. 16 In our case, the irregular contours on the endocardial surface of the anatomical left ventricle, indicating prominent trabeculations of the left ventricle, were visible from 15 weeks of gestation onward. In the SMI image of normal cardiac structure at the same week of gestation, the left ventricular endocardial surface was smooth (Figure 2c).…”

“…This enables the description of blood flow mapping at high resolutions, which cannot be depicted using conventional Doppler modes. Jabak et al reported that intracardiac structures could be more clearly visualized by SMI at less than 15 weeks of gestation compared with conventional color Doppler and B‐mode methods, resulting in “virtual” contrast imaging 16 . In our case, the irregular contours on the endocardial surface of the anatomical left ventricle, indicating prominent trabeculations of the left ventricle, were visible from 15 weeks of gestation onward.…”

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

“…This could potentially identify vulnerable plaques and have important implications in stroke management 17 . Additional vascular studies of SMI focused on endo‐leaks after aortic grafting, visualization of hepatic artery after liver transplant, cardiac imaging in fetuses, and assessment of intracranial vasculature in neonatal transcranial ultrasonography 18‐21 . A single case report also demonstrated possible utility of SMI in characterization of wall inflammation in Takayasu arteritis 22 .…”

Function and Safety of SlowflowHD Ultrasound Doppler in Obstetrics

“…Similar advanced flow-detection imaging techniques are also currently marketed under various trademarks (Hasegawa et al 2019;Mack et al 2019;Hata et al 2020aHata et al , 2020bJabak et al 2020;Sainz et al 2020). These applications include Superb Microvascular Imaging (SMI) by Canon Medical Systems (formerly Toshiba Medical Imaging), Detective Flow Imaging (DFI) by Hitachi Medical Systems, microflow imaging (MFI) by Philips and MV-Flow by Samsung Health Care.…”