Abstract
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Introduction: This exhibit aims to provide an overview of renal PET radiotracers and specific probes for functional and molecular imaging of kidney disease. We discuss the individual clinical utility, advantages, and limitations of each functional and molecular imaging radiotracer. In doing so, we summarize the current knowledge of the pathophysiological interactions between kidney diseases and various radiotracers, describing the role of each tracer as a marker for diagnosis, prognosis, treatment monitoring, molecular imaging, and as potential targets for therapeutic strategies.
Computer tomography (CT), magnetic resonance imaging, and ultrasound have been the dominant non-invasive imaging modalities used for the initial assessment and staging of kidney diseases. However, these modalities are limited by their low sensitivity to small tumors and low specificity to renal diseases. When combined with CT, positron emission tomography (PET) imaging allows for the assessment of paramount biological processes related to renal pathophysiology. While PET/CT is important in the diagnosis and treatment of a variety of cancers, its application in functional and molecular imaging of kidneys continues to be investigated. Considering the recent developments in specialized radiotracers specifically designed for kidney diseases, there is potential for the increased utility of PET in renal disease.
Methods: A comprehensive literature review of PET radiotracers for functional and molecular imaging of kidneys was conducted using PubMed® and EMBASE® platforms for publications in 2012 or later. Functional imaging radiotracers for kidney PET were categorized into those that1) reflect glomerular filtration rate (GFR); 2) are secreted in the tubules employed for measurement of effective renal plasma flow (ERPF); 3) reflect renal blood flow; 4) are utilized for targeted evaluation of specific renal cellular processes and derangements.
Results: Functional imaging in the setting of renal physiology and pathology:
Radiotracers that reflect GFR are [68Ga]ethylenediaminetetraacetic acid ([68Ga]EDTA), [68Ga] diethylenetriamine-pentaacetic acid ([68Ga]DTPA), [68Ga] 1,4,7-triazacyclononane-1,4,7-triacetic acid ([68Ga] NOTA], [18F] FDS (2-deoxy-2-[18F]fluorosorbitol), Cobalt-55 EDTA.
Renal PET/CT radiotracers that may be utilized for ERPF assessment are [18F]Re(CO)3-N-(fluoroethyl)iminodiacetic acid (FEDA), p-[18F]fluorohippurate ([18F]PFH), Al[18F]NODA-butyric acid.
PET/CT radiotracers that reflect renal blood flow are O-15 water, rubidium-82 (Potassium-analog), Cu-PTSM, N-13-labeled ammonia.
PET/CT radiotracers that reflect a specific cellular cascade such as [68Ga]IRDye800-tilmanocept for mesangial cell uptake of tilmanocept used for glomerular imaging
Conclusions: With the advent of novel PET radiotracers for renal disorders, it is critical to understand their individual functionality, sensitivity, specificity, advantages, and limitations, as well as the current status of relevant clinical applications. Several of the radiotracers discussed in this exhibit have been investigated in animals or are undergoing preliminary human clinical trials. Therefore, knowledge of these radiotracers is crucial for future research and better understanding the clinical indication of these renal radiotracers which may soon be available more widely.