The primary goal of this study is to assess the accuracy of conventional fat fraction proton MRI for the detection of Brown Adipose Tissue (BAT) in healthy subjects using [18F]-2-fluoro-2-deoxy-D-glucose (fluorodeoxyglucose) -PET as gold standard.

In this pilot study, MRI and PET imaging of BAT of healthy adult volunteers will be performed on a combined PET/MRI scanner under mild cold condition.

In the fight against obesity, brown adipose tissue (BAT) is considered to be the newest target. The hypothesis is that this tissue is partially responsible for the imbalance between energy intake and energy expenditure that keeps lean people lean and obese people obese.

The detection of this tissue in adult humans represents an unmet need. BAT is difficult to detect and measurements of tissue fat fraction performed by magnetic resonance imaging have been proposed as a mean to differentiate the highly hydrated brown fat from the less hydrated white adipose tissue and from muscle.

To this end, the objective of this study is to assess the accuracy of magnetic resonance fat fraction measurements for the detection of BAT volume in adult humans, while using PET with fluorodeoxyglucose as gold standard.

For this study subjects will undergo a combined MRI/PET scan. The scans will be done during stimulation of thermogenic activity by mild cold exposure.

Inclusion Criteria:

• Each subject must be fully informed and have signed consent.
• BMI < 34
• Normal neurological and psychological development / able to give consent
• Willingness to participate in this study

Exclusion Criteria:

• Subjects less than 18 years of age
• Severe claustrophobia
• Women who are pregnant, nursing an infant or planning to become pregnant in the next 30 days
• People who have a condition that makes MRI unsafe for them (for example, cardiac pacemaker, epicardial pacemaker leads, cochlear implants, metal aneurysm clip, iron filings in your eyes or metal halo devices)
• Have had radiation therapy or chemotherapy in the 2 months prior to PET scan
• Subjects are taking medications that may interfere with BAT detection

Healthy adult human with a BMI <28