¹⁸F-FDG PET/CT technology for the assessment of brown adipose tissue: an updated review

ABSTRACT

Introduction

This review provides an update of 18 F-fluorodeoxyglucose ([¹⁸F] FDG) for Brown adipose tissue (BAT) activity quantification, whose role is not completely understood.

Areas covered

We conducted an unstructured search of the literature for any studies employing the [¹⁸F] FDG PET in BAT assessment. We explored BAT quantification both in healthy individuals and in different pathologies, after cold exposure and as a metabolic biomarker. The assessment of possible BAT modulators by using [¹⁸F] FDG PET is shown. Further PET tracers and novel developments for BAT assessments are also described.

Expert opinion

Further PET tracers and imaging modalities are under investigation, but the [^18F] FDG PET is currently the method of choice for the evaluation of BAT and further multicentric trials are needed for a better understanding of the BAT physiopathology, also after cold stimuli. The modulation of BAT activity, assessed by [¹⁸F] FDG PET imaging, seems a promising tool for the management of conditions such as obesity and type 2 diabetes. Moreover, an interesting possible correlation of BAT activation with prognostic [¹⁸F] FDG PET indices in cancer patients should be assessed with further multicentric trials.

KEYWORDS:

• Brown adipose tissue
• positron emission tomography
• [¹⁸F] FDG-PET/CT
• BAT activity quantification
• BAT

Article highlights

• [18F] FDG-PET/CT analysis is the most used method to quantify human BAT volume and activity; the quantification of BAT volume and activity depends on the selection and combination of HU and SUV thresholds but optimal Interpretation criteria for [18F] FDG-PET/CT for BAT evaluation are still a matter of debate.

• BAT assessment by using [18F] FDG-PET imaging in healthy individuals provides novel insights into the physiology and the pathology of BAT.

• [18F] FDG-PET after cold exposure, in order to stimulate BAT activity, may assess BAT quantification after stimuli, thermogenesis, clarifying the doubts related to BAT activity in thermogenesis, especially in terms of differences due epidemiological and habits factors; also the cold-induced BAT activity seems to be modulated by different potential actors.

• Human BAT volume has consistently been claimed to be inversely associated with whole-body adiposity, and, therefore BAT quantification by using [18F] FDG-PET imaging may serve as a metabolic biomarker (playing a possible a role in the prevention or treatment of obesity and type 2 diabetes).

• [18F] FDG-PET imaging may provide novel insights in the physiological significance of BAT in relation to cachexia and related diseases, with a possible impact in cancer prognosis.

• [18F] FDG-PET imaging allows the validation of possible BAT modulators that may serve as novel therapeutic strategies in obesity, overweight and type 2 diabetes.

• Novel PET tracers, alone or in combination to [18F] FDG-PET imaging, may increase the physio-pathological knowledge background of BAT due to information obtainable by the specific biodistribution of each tracer.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial relationships or otherwise to disclose.

Additional information

Funding

This paper was not funded.