The authors present data from a prospective study of 16 healthy volunteers who came for biopsy of supraclavicular fat on two separate occasions, and found that brown fat could be obtained using PET/MRI/US guidance in almost all cases, except in one instance for a very lean subject. The paper is of interest, because collection of brown fat would be helpful for a variety of research questions. So, developing a reliable protocol to collect adequate tissue would be useful. Overall, the paper is well written and I was convinced that the authors could collect brown fat. However, I had multiple questions that would limit my own ability to reproduce their data and/or generalize it to other populations: 1. It was unclear how the authors used the information from the PET/MRI to guide needle placement. In my own experience, without a specific target such as a lymph node or mass, it is difficult to correlate US imaging with cross sectional imaging with MRI or CT. More detail regarding how PET/MRI was used to guide the US-guided procedure would be helpful. 2. It was unclear whether PET/MRI was needed at all. The authors showed only one example of a patient. Was the distribution of brown fat significantly different between subjects? Or could an operator merely sample from any place in the supraclavicular fat? Showing more images from different patients could illustrate that brown fat deposits differ a lot between people, and with more images from the biopsy, perhaps the authors could demonstrate how they correlated PET/MRI with US imaging. 3. The volunteers were all healthy and very young (early 20s). It is unclear if this paper would generalize to older patient populations. This should be mentioned as a caveat. Finally, the rationale behind performing two separate biopsies on different occasions was not elaborated. I think it would have been more helpful to attempt the biopsy on the second occasion with US only, to see if the PET/MRI was really necessary.
To investigate transcutaneous core-needle biopsy of the supraclavicular fat as a minimally invasive and scar-free method of obtaining brown adipose tissue (BAT) samples.
Material and Methods
In a prospective clinical trial, 16 volunteers underwent biopsy on two separate occasions after FDG-PET had shown active BAT in the supraclavicular fossa with an FDG uptake (SUVmax) > 3 mg/dl. After identifying the ideal location for biopsy on FDG-PET/MRI, ultrasound-guided core-needle biopsy of supraclavicular fat with a 16G needle was performed under local anesthesia and aseptic conditions. Tissue samples were immediately shock-frozen in liquid nitrogen and processed for gene expression analysis of adipose tissue markers. Wounds were checked two weeks after the biopsy.
Tissue sampling was successful in 15 volunteers in both scans and in one very lean volunteer (BMI=19.9 kg/m2) in only one visit, without any reported adverse events. Therefore 31 tissue samples were available for further analysis. Gene expression could be analyzed with high success rate in 30 out of 31 tissue biopsies. The intervention was well tolerated with local anesthetics. None of the volunteers showed any scarring.
Ultrasound-guided core-needle biopsy of FDG-positive supraclavicular fat yields sufficient BAT samples for quantification of molecular markers. It may, however, be limited in extremely lean individuals with very little supraclavicular fat.
➤ Version 1 (2019-10-14)
Julian Müller, Anton Becker, Miroslav Balaz, Vissarion Efthymiou, Claudia Maushart, Gani Gashi, Edwin terVoert, Christian Wolfrum, Matthias Betz and Irene Burger (2019). Ultrasound-guided core biopsy of FDG-PET positive supraclavicular fat to investigate and quantify molecular markers of brown adipose tissue. Researchers.One, https://researchers.one/articles/ultrasound-guided-core-biopsy-of-fdg-pet-positive-supraclavicular-fat-to-investigate-and-quantify-molecular-markers-of-brown-adipose-tissue/5f52699c36a3e45f17ae7df6/v1.