New! F-18-based PET/CT for sodium-iodine-symporter-targeted imaging!
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EDITORIAL
New! F-18-based PET/CT for sodium-iodine-symporter-targeted imaging! Frederik A. Verburg 1 & Luca Giovanella 2,3 & Martha Hoffmann 4 & Ioannis Iakovou 5 & Jasna Mihailovic 6,7 & Petra Petranovic Ovcaricek 8 & Alexis Vrachimis 9 & Markus Luster 1
# The Author(s) 2020
Dear Sir, Targeting of the sodium-iodine-symporter (NIS) with radionuclides stood at the birth of nuclear medicine [1]. Ever since, it has been a cornerstone of the work of nuclear medicine physicians throughout the world. The theragnostic principle was pioneered using the direct NIS substrate iodine: its various isotopes could be used for imaging (I-123, I-124 and to an extent I-131) and therapy (I-131) alike. In no way would the biological behaviour of the substances (or in this case: isotopes) used for imaging differ from the one used for radionuclide therapy, making it perfectly possible to select and direct radioiodine therapy based on radioiodine imaging. Somewhat later, a different NIS substrate was developed with more suitable properties for imaging in terms of a shorter halflife, lower radiation burden and a radiation spectrum more suited for use with gamma cameras: Tc-99m-pertechnetate. This made thyroid scintigraphy possible at low cost and comparably high resolution. For a long time, this spectrum sufficed for all thyroidological imaging needs. Even for positron emission tomography (PET)based imaging, iodine 124 could be used [2, 3]. However, just like I-131 poses problems for gamma camera imaging due to high energy radiation spectrum, I-124 does the same in PET.
Furthermore, again like I-131, the long half-life of I-124 limits the activity that can be administered compared with other F-18based PET tracers. To add insult to injury, I-124 is only available at high commercial prices or requires a powerful cyclotron to produce. Thus, nuclear thyroidology for a long time has been lacking the high sensitivity, high-resolution imaging possible which is available for so many other targets in physiology using F-18- or Ga-68-based tracers. Enter [18F]tetrafluoroborate ([18F]TFB). As early as the 1950s, [4] reported the radiolabeling of [18F]TFB by isotopic exchange using reactor-generated [18F]fluoride on nonradioactive TFB under acidic conditions. For reasons unknown to us, this agent was not identified as a tracer with particularly high thyroidal uptake [5]. However, in 2010, Jauregui-Osoro [6] in a preclinical model of normal thyroid tissue and thyroid cancer showed clearly that TFB is a firstclass NIS-targeted physiological imaging agent, showing excellent uptake both in normal rat thyroid cells and in a model of papillary thyroid cancer. The same group then in 2017 [7] published the first results of [18F]TFB evaluation in human subjects, showing a biodistribution similar to pertechnetate and a low effective dose of 0.0326 mSv/MBq in five patients with differentiated thyroid cancer (DTC), which is in line with
This article is part of the Topical Collection on Endocrinology * Frederik A. Verburg [email protected]
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