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Development of a Non-Invasive Biomarker for Bleeding Risk Stratification of Gastroesophageal Varices

Subject Area Nuclear Medicine, Radiotherapy, Radiobiology
Term from 2020 to 2023
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 442418831
 
Final Report Year 2023

Final Report Abstract

Patients with end-stage liver disease (cirrhosis) can develop gastroesophageal varices. Gastroesophageal varices are pathologically enlarged veins in the esophagus that can rupture and cause life-threatening bleeding. The current standard for diagnosing gastroesophageal varices is esophagogastroduodenoscopy (EGD), a procedure in which a thin tube with a camera is inserted down the throat to visualize the enlarged veins in the esophagus. However, EGD is invasive, expensive, requires sedation, and can be uncomfortable for patients. First studies have shown promise that four-dimensional flow magnetic resonance imaging (4D Flow MRI) can non-invasively detect gastroesophageal varices at high risk for bleeding. 4D Flow MRI can measure the blood flow in the vessels supplying the liver and the varices. This study aimed to improve the quality and speed of 4D Flow MRI scans so that they can be used to develop noninvasive biomarkers for predicting the presence of gastroesophageal varices in patients with cirrhosis. We focused on two main areas: 1. Improving the quality of 4D Flow MRI scans in patients with obesity. Many patients with cirrhosis are obese, and 4D Flow MRI scans can be difficult to obtain in these patients. We found that a new MRI technique called “inner volume excitation improves image quality in obese patients. In this technique, only the central part of the” patient’s body is imaged to exclude artifacts arising from fatty tissue in the body wall and arms. 2. Shortening the acquisition time of 4D Flow MRI scans. 4D Flow MRI scans can be long, taking around 10 minutes to complete. We used time-averaged acquisitions to shorten the acquisition time to 3 minutes while retaining diagnostic image quality. This was possible because flow in the portal vein is constant and does not change relevantly during the cardiac cycle. We validated the proposed 4D flow MRI techniques in a group of 15 healthy subjects with obesity. Moreover, we developed a flow phantom that can be used to test 4D flow MRI sequences and postprocessing techniques. This phantom can be used to create a variety of flow conditions, including those that are found in patients with cirrhosis. To pave the way of potential use in clinical routine, we also established normal values for 4D flow MRI-derived flow, velocity, and vessel diameters in healthy subjects. The findings of this research lay the foundation for establishing 4D flow MRI of the liver in clinical routine. We developed a fast, robust, and reproducible sequence to measure blood flow in the portal vein. Future research will focus on improvement of reconstruction and postprocessing techniques of the 4D flow data. We can then apply the method in a large cohort of patients undergoing EGD for evaluation of gastroesophageal varices. This will help to determine diagnostic markers for non-invasive risk-assessment of gastroesophageal varices in patients with cirrhosis. Such a test could reduce the need for EGD and improve patient care.

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