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J Nucl Med. 2019 Sep 13. pii: jnumed.119.228627. doi: 10.2967/jnumed.119.228627. [Epub ahead of print]

PET-based dosimetry of [68Ga]Ga-NODAGA-exendin-4 in humans, a tracer for beta cell imaging.

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1
Radboud University Medical Center, Netherlands.

Abstract

[68Ga]Ga-NODAGA-exendin-4 is a promising tracer for beta cell imaging using PET/CT. Possible applications include pre-operative visualization of insulinomas as well as discrimination between focal and diffuse forms of congenital hyperinsulinism. There is also a significant role for this tracer in extending our knowledge of the role of beta cell mass in the pathophysiology of type 1 and type 2 diabetes by enabling non-invasive quantification of tracer uptake as a measure for beta cell mass. Calculating radiation doses from this tracer is important to assess its safety for use in patients (including young children) with benign diseases and healthy individuals. Methods: Six patients with hyperinsulinemic hypoglycemia were included. After intravenous injection of 100 MBq of the tracer, 4 successive PET/CT scans were obtained at 30, 60, 120 and 240 minutes post injection. Tracer activity in the pancreas, kidneys, duodenum and remainder of the body were determined and time-integrated activity coefficients for the measured organs were calculated. OLINDA/EXM version 1.1 software was used to calculate radiation doses using the reference adult male and female models and to estimate radiation doses to children. Results: The mean total effective dose for adults is very low (0.71 ± 0.07 mSv for a standard injected dose of 100 MBq). The organs with the highest absorbed dose are the kidneys (47.3 ± 10.2 mGy/ 100 MBq). The estimated effective dose is 2.32 ± 0.32 mSv for an injected dose of 20 MBq in newborns. This dose decreases to 0.77 ± 0.11 / 20 MBq for children of 1 year old and 0.59 ± 0.05 mSv for an injected dose of 30 MBq in 5-year old children. Conclusion: Our human PET/CT based dosimetric calculations show that the effective radiation doses from the novel tracer [68Ga]Ga-NODAGA-exendin-4 for adults as well as children are very low. The doses are lower than reported for other polypeptide-tracers such as somatostatin analogs (2.1-2.6 mSv/ 100 MBq) and are beneficial for its application as a research tool, especially in case of repeated examinations.

KEYWORDS:

Endocrine; PET/CT; Radiobiology/Dosimetry; beta cells; congenital hyperinsulinism; dosimetry; exendin-4; insulinoms

PMID:
31519801
DOI:
10.2967/jnumed.119.228627

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