Additional value of superb microvascular imaging for assessing hepatic arterial blood flow after pediatric liver transplantation

Role of Superb Microvascular Imaging (SMI) vascularity index values and vascularity patterns in the differential diagnosis of malignant liver lesions

PURPOSE

To evaluate the Superb Microvascular Imaging (SMI) vascular patterns and vascularity index (VI) values of malignant focal liver lesions (FLLs), assess their role in differential diagnosis, and examine interobserver agreement.

MATERIALS AND METHODS

A total of 107 patients (52 males, 55 females; mean age 62 ± 12.8 years, range 25-87) referred to the interventional radiology clinic for FLL biopsy between April 2022 and April 2023 were analyzed. Two radiologists independently assessed the SMI vascular patterns and calculated VI values. Differences among three lesion groups - hepatocellular carcinoma (HCC, n = 16), non-HCC primary liver malignancies (n = 16), and metastases (n = 75) - were evaluated, and interobserver agreement was assessed.

RESULTS

Most metastases (88%) demonstrated hypovascular patterns, while HCCs predominantly exhibited hypervascular patterns (68.7-81.3%). Non-HCC primary malignancies showed no dominant vascular pattern. Significant differences in SMI patterns were observed among lesion types (p = 0.001-0.035). VI values for HCCs (7.53-7.73) were significantly higher than those for non-HCC malignancies (2.73-2.93) and metastases (1.35-1.36) (p = 0.0001). ROC analysis based on VI values yielded AUCs of 0.886-0.887, with a cutoff of 2.92 providing 81.3% sensitivity and 79.1-80.2% specificity for HCC diagnosis. The inter-reader agreement for SMI patterns had a kappa score of 0.634, while the intraclass correlation coefficient (ICC) for VI values was 0.959.

CONCLUSION

HCCs displayed more hypervascular SMI patterns and significantly higher VI values compared to other malignant FLLs, emphasizing the diagnostic potential of VI in distinguishing HCC from non-HCC tumors. Although metastases primarily exhibited hypovascular patterns and low VI values, no dominant vascular pattern was identified in non-HCC primary liver malignancies. Assessing VI values provided higher interobserver agreement compared to SMI patterns, enhancing objectivity and reproducibility.

European Society of Pediatric Radiology survey of perioperative imaging in pediatric liver transplantation: (3) postoperative imaging

BACKGROUND

Liver transplantation is the state-of-the-art curative treatment for end-stage liver disease. Imaging is a key element in the detection of postoperative complications. So far, limited data is available regarding the best radiologic approach to monitor children after liver transplantation.

OBJECTIVE

To harmonize the imaging of pediatric liver transplantation, the European Society of Pediatric Radiology Abdominal Taskforce initiated a survey addressing the current status of imaging including the pre-, intra-, and postoperative phases. This paper reports the responses related to postoperative imaging.

MATERIALS AND METHODS

An online survey, initiated in 2021, asked European centers performing pediatric liver transplantation 48 questions about their imaging approach. In total, 26 centers were contacted, and 22 institutions from 11 countries returned the survey.

RESULTS

All sites commence ultrasound (US) monitoring within 24 h after liver transplantation. Monitoring frequency varies across sites, ranging from every 8 h to 72 h in early, and from daily to sporadic use in late postoperative phases. Predefined US protocols are used by 73% of sites. This commonly includes gray scale, color Doppler, and quantitative flow assessment. Alternative flow imaging techniques, contrast-enhanced US, and elastography are applied at 31.8%, 18.2%, and 63.6% of sites, respectively. Computed tomography is performed at 86.4% of sites when clarification is needed. Magnetic resonance imaging is used for selected cases at 36.4% of sites, mainly for assessment of biliary abnormalities or when blood tests are abnormal.

CONCLUSION

Diagnostic imaging is extensively used for postoperative surveillance of children after liver transplantation. While US is generally prioritized, substantial differences were noted in US protocol, timing, and monitoring frequency. The study highlights potential areas for future optimization and standardization of imaging, essential for conducting multicenter studies.

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.

Superb Microvascular Imaging (SMI) Compared with Color Doppler Ultrasound for the Assessment of Hepatic Artery in Pediatric Liver Transplants: A Feasibility Study

(1) Background: Despite progression in surgical techniques and immunological treatments, hepatic artery (HA) thrombosis and stenosis still develop as an early or late liver transplant (LT) complication. We aimed to compare superb microvascular imaging (SMI) with conventional Doppler imaging (CDI) in the assessment of HA in a cohort of pediatric patients undergoing follow-up ultrasound (US) for LT. (2) Methods: This prospective, observational study included 73 pediatric LT recipients (median age, 7 years; IQR, 5.8 years; 35 females) who underwent US during LT follow-up from March to December 2019. For each examination, CDI and SMI were separately assessed in terms of HA visibility and spectral waveform morphology (SWM). The former was scored based on HA discrimination from the blooming signal of the surrounding vessels, as follows: 0, not visible; 1, majority course hardly distinguishable; and 2, majority course clearly distinguishable. The latter was scored on a two-point scale: 0, combined venous and arterial SWM, and 1, pure arterial SWM. The patient’s overall score was finally calculated by adding the two individual scores. (3) Results: Both the absolute scores and frequency of overall scores equal to 3 (maximum global score) were higher using SMI compared with CDI. The median overall score was 3 for SMI and 2 for CDI (p = 0.011; IQR = 1). An overall score equal to 3 was obtained in 74% and 49.3% of the study population using SMI and CDI, respectively (p = 0.002). This was attributable to a better score in HA visibility (p = 0.007). (4) Conclusions: SMI has shown promise for assessing HA in pediatric LT recipients, possibly serving as a complementary non-invasive tool of CDI in everyday practice.

Diagnostic accuracy of ultrasound superb microvascular imaging for parotid tumors: A protocol for systematic review and meta-analysis

BACKGROUND

As a novel ultrasound technique, superb microvascular imaging (SMI) can quickly, simply, and noninvasively study the microvascular distribution in the tumor and evaluate the microvascular perfusion. Studies suggested that SMI is helpful for the differentiation between benign and malignant parotid tumors. However, the results of these studies have been contradictory. Therefore, the present meta-analysis aimed at determining the accuracy of SMI in the differential diagnosis between benign and malignant parotid tumors.

METHODS

We will search PubMed, Web of Science, Cochrane Library, and Chinese biomedical databases from their inceptions to September 30, 2020, without language restrictions. Two authors will independently carry out searching literature records, scanning titles and abstracts, full texts, collecting data, and assessing risk of bias. Review Manager 5.2 and Stata14.0 software will be used for data analysis.

RESULTS

This systematic review will determine the accuracy of SMI in the differential diagnosis between benign and malignant parotid tumors.

CONCLUSION

Its findings will provide helpful evidence for the accuracy of SMI in the differential diagnosis between benign and malignant parotid tumors.

SYSTEMATIC REVIEW REGISTRATION

INPLASY2020100093.