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Non-invasive, high quality assessment of fatty liver disease

Best Practice
Dr. Pedrosa, Ivan, M.D. UT Southwestern • USA
Dr. Yokoo, Takeshi, M.D., Ph.D. UT Southwestern Med Ctr • USA

University of Texas Southwestern (UT Southwestern) Medical Center in Dallas, Texas, USA, recently collaborated with Philips to optimize and verify mDIXON Quant, a low flip angle, multi-echo, multi-peak method that enables robust and high quality quantification of fat deposition in the liver. UT Southwestern operates three Philips MR systems clinically; an Achieva 1.5T, Achieva 3.0T TX, and Ingenia 1.5T. Additionally, two Achieva 3.0T systems and a 7.0T system are housed in the Advanced Imaging Research Center.

  
 Ivan Pedrosa, MD <br><br> Takeshi Yokoo, MD, PhD <br>
Ivan Pedrosa, MD

Takeshi Yokoo, MD, PhD

Collaboration on a fast and robust, non-invasive method to measure fat in liver

A healthy liver has about 5%-6% fat content. When the amount of fat in the liver exceeds that amount, the result is fatty liver disease, which affects between 3% and 33% of people worldwide. [1]. While classically described in patients with excessive alcohol consumption, fatty liver not related to alcohol, called Non-Alcoholic Fatty Liver Disease (NAFLD), is now considered the most common type of fatty liver disease in the western world. [2] The risk of NAFLD is multifactorial, however it is most often associated with obesity. [3]

 

Patients with NAFLD are at high risk of steatohepatitis, which can lead to cirrhosis and possibly liver failure. In addition, the exact relationship between NAFLD and other health problems is not completely understood. “There are other entities that are associated with NAFLD, such as diabetes and hypertension, and we are trying to understand if they are a consequence or a cause of the disease,” says Ivan Pedrosa, MD, Chief of MRI and Associate Professor of Radiology at UT Southwestern Medical Center. “There is evidence indicating that patients with NAFLD have a higher risk for liver cancer and cardiovascular events.”

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Imaging aids diagnosis

Despite these severe consequences, NAFLD can also be asymptomatic. In those cases, it is often detected when imaging is ordered as a follow-up to an abnormal liver enzyme test that is conducted as part of a routine physical examination. Ultrasound is the most common method to screen for fatty liver disease. However, ultrasound has only 70% sensitivity in detecting abnormal amounts of fat in the liver, and the sensitivity is even lower in obese patients. [4]

 

“Liver biopsy, while accurate, is invasive and has a risk of complications that are rare but can be life-threatening. Because of that, patients and referring physicians may be reluctant to use liver biopsy for the initial diagnosis of NAFLD, and even more so for a follow-up,” says Takeshi Yokoo, MD, PhD, Assistant Professor of Radiology. “Patients can’t have a liver biopsy every few months to assess disease progression. In addition, biopsy only assesses a small fraction of the liver, so the sampling error can be significant in patients with heterogeneous fat deposition.”

 

“Spectroscopy can also quantify fat in the liver, but it requires expertise that is not available everywhere, and like biopsy, only measures a small sample of tissue,” he notes. “In contrast, mDIXON Quant enables quantification of fat in the liver in a way that is non-invasive, fast, robust and provides high quality results.”

 Severe case of fatty liver, 33% fat in red ROI.
Severe case of fatty liver, 33% fat in red ROI.

Fruitful collaboration

UT Southwestern has been involved in a collaboration with Philips on the development and evaluation of mDIXON Quant for clinical use.

 

“It is a perfect synergistic effect of combining expertise to work on a technique that is robust and provides the data that we need,” Dr. Pedrosa notes. “We were fortunate to have clinical research at UT Southwestern using spectroscopy to quantify fat in the liver, which provided us with the opportunity to assess mDIXON Quant in human subjects. Being able to correlate data from mDIXON Quant with the spectroscopy data in vivo and to work with Philips scientists to improve the acquisition and reconstruction method using these data allowed us to develop a robust method to quantify fat in the liver.”

 

“We found that mDIXON Quant provides high quality data for the quantification of fat concentration in the liver when compared to spectroscopy and thus opens the door to investigate many clinical questions,” he adds. “For example, if losing weight is a method to reduce fatty liver, how much weight does one have to lose? At what point does excess fat become a problem? How effective are various therapies? Having a quantitative measure of fat allows us to conduct studies that will provide answers to clinical questions.”

Standardization is key to clinical relevance

“While different MR system vendors measure fat content in the liver in different ways, it is the reproducibility of the results across all vendors and field strengths [5] that is the strength of MR fat quantification in the liver,” Dr. Yokoo says. “Fat quantification in the liver now has the potential to become like blood pressure or hemoglobin level. The measurement is reliable [6], so it can be used to make patient management decisions. Patients can go to different centers, or different MR systems at the same center, and the results can be compared with confidence.”

Important health factor

Both Dr. Pedrosa and Dr. Yokoo expect mDIXON Quant to become a standard part of liver protocols, given that in the United States alone, 20-30 million people have NAFLD.

 

“Many radiologists are not cognizant of reporting fatty liver as a significant finding, and I think that needs to change,” Dr. Yokoo says. “If we believe that hypertension and high cholesterol are important biomarkers to predict future development of coronary disease or poor outcome, liver fat is just as important. So if you think hypertension should be reported, then liver fat should be reported as well.”

References

1. Angulo P. 2007. GI Epidemiology: nonalcoholic fatty liver disease. Alimentary Pharmacology & Therepautics, 25(8), pp.883-889.

2. Ong, JP and Younossi, ZM. 2007. Epidemiology and natural history of NALFD and NASH. Clin Liver Dis, 11(1), pp.1-16.

3. Farrell, G, McCullough, AJ, and Day, CP (Eds.) 2013. Chapter I – What is non-alcoholic fatty liver disease (NAFLD) and why is it important? Non-Alcoholic Fatty Liver Disease: A Practical Guide. John Wiley & Sons.

4. Bohte, AE, et al. 2011. The diagnostic accuracy of US, CT, MRI and 1H-MRS for the evaluation of hepatic steatosis compared with liver biopsy: a meta-analysis. Eur Radiol, 21(1), pp.87-97.

5. Reeder, SB et al. 2011. Quantitative assessment of liver fat with magnetic resonance imaging and spectroscopy. J Magn Reson Imaging, 34(4), pp.729-49.

6. Mashhood, A et al.2013. Reproducibility of hepatic fat fraction measurement by magnetic resonance imaging. J Magn Reson Imaging, 37(6), pp. 1359-70.
 

Related reading

 
 

Ivan Pedrosa, MD, is Chief of MRI and Associate Professor of Radiology at University of Texas Southwestern (UT Southwestern) Medical Center in Dallas, Texas, USA.

Takeshi Yokoo, MD, PhD, is Assistant Professor of Radiology at University of Texas Southwestern (UT Southwestern) Medical Center in Dallas, Texas, USA.



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Best Practice
Achieva 3.0T TX
Body, fat fraction, liver, mDIXON Quant, NAFLD
 

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