The most common cause of chronic liver disease? Nonalcoholic fatty liver disease (NAFLD). With 25% of the world’s population diagnosed, NAFLD is the most common cause of chronic liver disease globally.1,2Of patients diagnosed with NAFLD, approximately 20-30 percent progress to more advanced NASH fibrosis.3
Fatty liver, or hepatic steatosis, occurs when fat molecules are not metabolized efficiently enough by the body and end up stored in the liver. While a normal liver contains a small amount of fat, the liver is considered “fatty” if the amount of fat within the hepatocytes exceeds 5 percent.4
The liver’s primary role is to filter blood and remove harmful substances. When the liver detects something harmful, it works to eliminate and clear that substance from the body. During this process and immune response, some inflammation occurs. Yet, the liver is a fascinating organ. Once that harmful substance is cleared, the liver inflammation resolves, and the liver is once again healthy.
The problem comes when there is a constant inflammatory response, which could stem from a variety of behaviors or causes. As inflammation continues, liver tissue becomes increasingly stiff, and fibrosis may develop. If left untreated, the liver tissue may be unable to repair itself. This causes permanent and irreversible liver damage called cirrhosis.
Early detection ofhepatic steatosisimproves the chances of managing or reversing the condition before changes that require expensive medical intervention or irreversible changes occur.2
The Real Cost and Availability of Fatty Liver Diagnosis Techniques
在美国，每年非酒精性脂肪肝的直接医疗费用估计约为1030亿美元。5
There are numerous imaging and non-imaging medical techniques that diagnose hepatic fat content. However, these techniques vary in effectiveness, cost, invasiveness, availability of equipment, and/or patient suitability.
目前，肝活检是肝脂肪变性诊断和分级的参考标准。然而，肝活检不适合用于筛查或频繁监测，因为它具有侵袭性，容易出现采样错误，观察员的可变性和并发症的风险。3
When it comes to characterizing fat content in the liver, MRI-PDFF is the most widely accepted noninvasive imaging modality. MRI-PDFF is a quantitative imaging biomarker that enables accurate, repeatable, and reproducible quantitative assessment of liver fat over the entire liver.3It provides a specific fat content number, between 1–100 percent. Yet, the cost, exam time, and ease of availability makes routine MRI-PDFF challenging. Due to these challenges, there is a need for technology that is less invasive, more cost-effective, and widely available. Here, the advantages of using ultrasound to help diagnose hepatic fat content become clear.
An Accurate AND Accessible Dagnosis Tool
“With the association between hepatic steatosis [fatty liver] and fibrosis progression, it is critical to have accurate, noninvasive tools to aid in not just assessing fibrosis but also hepatic steatosis,” saidRichard G. Barr, M.D., Ph.D., atSouthwood’s Imaging. “With theACUSON Sequoia ultrasound system, there are two new quantitative tools to meet this need:Auto Point Shear Wave Elastography[Auto pSWE] and an Ultrasound Derived Fat Fraction [UDFF] index. Auto pSWE enables up to 15 valid pSWE measurements literally in seconds; along with it comes a UDFF index that like the MRI Proton Density Fat Fraction (PDFF) classifies hepatic steatosis as an index value greater than 5 percent.”
A radiologist for more than 25 years, Barr is president of Radiology Consultants, Inc., and a diagnostic radiology specialist at Southwood’s Imaging, both in Youngstown, Ohio. He believes the ability to quantitatively detect hepatic steatosis in the early stages of chronic liver disease would be invaluable for referring physicians. “This could allow them to treat patients with hepatic steatosis earlier, monitor their progression, and work to minimize the incidence of advanced progression through early treatment and lifestyle changes,” he said.
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Expanding Ultrasound’s Role in Liver Assessment
与其他成像方式相比，超声具有许多明显的优势，如减少电离辐射、广泛的可用性和提高成本效益。但是超声在肝脏评估方面也有其他好处，因为它已经在肝脏疾病的诊断和管理中发挥了关键作用。In fact,ultrasoundis currently used to examine liver size, texture, vascularity, and liver tissue stiffness, as well as the identification and characterization of focal lesions.
A key quantitative tool to aid in the diagnosis and treatment of liver fibrosis isliver elastography, which measures shear waves in the liver that are proportional to liver tissue stiffness. The higher the shear velocity, the stiffer the tissue. As a result, liver elastography is a crucial tool in liver fibrosis diagnosis.
The current methods of assessing fatty liver using conventional ultrasound are qualitative. Radiologists will often grade the degree of fatty infiltration based on a variety of characteristics in the B-mode image, which can be subjective. There would be great clinical value in a quantitative ultrasound method to identify hepatic steatosis (fatty liver) with a unit of measure and cut off value consistent to that of MR-PDFF.
A Novel Approach
Auto Point Shear Wave Elastography (Auto pSWE)与超声衍生脂肪分数(UDFF)是创新的先进肝脏分析工具，可用于ACUSON Sequoia超声系统。
肝脏弹性成像通常与标准超声检查一起进行，并作为一种工具来帮助诊断和治疗慢性肝病患者。目前，肝脏弹性成像检查需要一种可重复的技术，因为目前的指南要求进行多次独立的采集(5-10次)，手工进行，通常在标准腹部超声检查的基础上增加5分钟。在这里，可以帮助降低肝脏弹性成像变异性的技术以及采集时间对临床医生和患者都是有益的。Auto pSWE是ACUSON Sequoia上的一种新的弹性成像技术，通过在一次不到5秒的时间内提供多达15次有效的pSWE测量，解决了较长的采集时间。自动pSWE比传统pSWE速度更快，与人工测量一样有效。
UDFF can quantify the amount of fat contained within a patient’s liver. Designed to provide a quantitative tool that can be widely accepted and understood, UDFF on the ACUSON Sequoia provides a fat fraction index in a percentage (%) and uses MRI-PDFF as the reference in detecting the presence of steatosis. Therefore, UDFF on the ACUSON Sequoia delivers a similar clinical utility to MRI-PDFF for determining hepatic steatosis. MRI-PDFF and UDFF methods classify hepatic steatosis as an index value greater than 5 percent.2With the use of this simple tool, clinicians now have a new, widely available, noninvasive measurement to aid in the management and overall assessment of hepatic steatosis. Not only can UDFF be performed in conjunction with a routine abdominal ultrasound, but UDFF can also quantify the amount of fat contained within a patient’s liver in just seconds.6
The Advanced Liver Analysis on the ACUSON Sequoia provides quantitative assessment of liver tissue stiffness and detection of hepatic steatosis in the same acquisition.
Conclusion
As precision medicine expands and the delivery of healthcare evolves, there is a need for quantitative imaging biomarkers that are noninvasive, cost effective, and widely available. The earlier clinicians can detect fatty liver disease—the leading cause of chronic liver disease worldwide—the better the chances of managing or reversing the condition before expensive medical intervention becomes necessary or irreversible changes occur.2The Advanced Quantitative Liver Analysis for use on the ACUSON Sequoia ultrasound system enables quantitative assessment of both liver stiffness and hepatic steatosis in seconds, addressing many of the current challenges on conventional ultrasound technology. “I find that on the ACUSON Sequoia, I have all of the tools I need for a comprehensive liver assessment, especially on the high BMI patient,” said Barr.
Case study supplied bySiemens Healthineers.
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- Based on 5 UDFF acquisitions when used as a stand-alone feature.
August 11, 2022
