Non-Invasive Quantitation of Muscular and Hepatic Fat Mass and Distribution for Treatment Monitoring

Principal Investigator: Alexander Lin

Authors: Daniel O’Connor, Sai Merugumala, Huijun Liao, Shehzad Basaria, Shalendar Bhasin, Alexander Lin
Lay Abstract

It is well known that being overweight is bad for your health, but your weight alone is not enough to find out why it is bad. This is especially true when you are trying to figure out the reason why different ways of losing weight are helpful. We use a special method of making pictures of fat using magnetic resonance imaging (MRI) so that we can see fat levels in different parts of the body such as your liver or your legs. The advantage of using MRI is that it is completely safe and provides high quality pictures.

We then use computers to study the images so that we can give exact measurements in different areas of the liver or leg. We can then use those numbers to see how good different treatments are. In this study, we looked at three uses of this method. The first was to figure out if a taking a pill improves your health and specifically if it lowers the amount of fat in the muscle. The second study looked at patients who are paralyzed to see if giving special exercise and medications could help to improve their health. The third study was in patients with prostate cancer who were given testosterone, a hormone, can also help to lower fat in the liver. We found that the fat images and measurements were important to see if these treatments were helpful.

Scientific Abstract

Introduction: Fat mass accumulation in the abdomen and extremities has been closely tied to cardiovascular mortality across various diseases. Magnetic resonance imaging (MRI) allows for the direct imaging of fat in the body using the Dixon method to determine fat volume and distribution for therapeutic monitoring.

Methods: 3T 2-point Dixon MRI measured “fat-only” and “water-only” axial images across the torso and lower extremities. Volumetric masks separating muscle, intramuscular fat, and subcutaneous fat in the thigh and water-fat in the liver were created using manual segmentation (3D Slicer). Tissue volumes were calculated (FSL) then compared at baseline and after treatment. Wilcoxon signed-rank tests were utilized to detect significant differences before and after treatment.

Results: These methods were used to study 13 subjects to determine the effect of nicotinamide mononucleotide nutrient in obese adults; 6 patients with spinal cord injury to determine if these testosterone and functional electrical stimulation interventions improved abdominal and muscular fat; and 48 patients with prostate cancer to determine the effects of androgen deprivation therapy. Significant differences in fat volume were found.

Conclusion: Dixon MRI is a non-invasive and quantitative method of assessing the effect of different therapies across a wide range of diseases.

Clinical Implications
We can use MRI to make images of fat in the body to quantify fat volume and distribution. These non- invasive measures can be used to measure the effects of different treatments.

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