![]() ![]() ![]() Despite the absence of trapping after cellular internalization of this 18F-labelled compound, a visual image analysis revealed a significantly higher number of lesions (factor of 2.4) and an improved interobserver correlation for PET. evaluated a fluorine-18 labelled SSA, Gluc-Lys-FP-TOCA, in 25 patients with SSTR-positive tumours seen on 111In-DTPA-octreotide scan and performed a direct comparison in 16 of these patients. Similarly to PET imaging of prostate specific membrane antigen (PSMA) in prostate cancer, where 18F-labelled compounds, such as 18F-PSMA-1007, have been developed to accommodate for the high tracer demand in this field, also in PET imaging of SSTRs, development of 18F-labelled compounds has been successful. For these reasons, the possibilities of using other PET-radionuclides for SSTR imaging should be explored. Apart from logistic disadvantages, gallium-68 also has drawbacks based on its physical characteristics, being its relatively high positron energy ( E mean = 0.83 MeV) and thus relatively long positron range ( R mean = 3.5 mm), which may result in a suboptimal spatial resolution. In the future, some possibilities may be opened up in this field by advances in the cyclotron production of gallium-68. Despite these advances, the overall activity yield per production batch of 68Ga-labelled compound remains low (capacity of two to four patients per production) and the half-life of gallium-68 is relatively short (68 min), limiting the potential for centralized production and distribution. Furthermore, newer generation 68Ge/ 68Ga-generators have received regulatory approval and kit-based labelling approaches to produce 68Ga-DOTA-peptides, such as SomaKit TOC™ (Advanced Accelerator Applications S.A.) and NETSPOT® (Advanced Accelerator Applications USA), have become available upon approval by the European Medicines Agency and the Food and Drug Administration, respectively. While in the first years, 68Ge/ 68Ga-generators were mainly found in larger nuclear medicine departments with access to a dedicated radiopharmacy staff that was needed for tracer production, the introduction and very rapid clinical implementation of 68Ga-PSMA-11 ( 68Ga-HBED-CC) for imaging of patients with prostate cancer since 2014, has made 68Ge/ 68Ga-generators and production facilities more widely present. Gallium-68 has the theoretical advantage that it can be made available in nuclear medicine departments from a 68Ge/ 68Ga-generator, thus not requiring a cyclotron. Although PET-imaging of NETs with 68Ga-DOTA-peptides is a well-established and validated technique and offers the additional advantage of forming a theranostic twin with 177Lu-DOTATATE or 90Y-DOTATOC, which are currently the most frequently used radiopharmaceuticals for peptide receptor radionuclide therapy (PRRT) in these patients, the use of gallium-68 as a radionuclide also has several disadvantages, mainly of logistic nature. ![]()
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