PET-Based Human Dosimetry of 68 Ga-NODAGA-Exendin-4, a Tracer for β-Cell Imaging

J Nucl Med. 2020 Jan;61(1):112-116. doi: 10.2967/jnumed.119.228627. Epub 2019 Sep 13.

Abstract

68Ga-NODAGA-exendin-4 is a promising tracer for β-cell imaging using PET/CT. Possible applications include preoperative visualization of insulinomas and discrimination between focal and diffuse forms of congenital hyperinsulinism. There is also a significant role for this tracer in extending our knowledge on the role of β-cell mass in the pathophysiology of type 1 and type 2 diabetes by enabling noninvasive quantification of tracer uptake as a measure for β-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 min after 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 software, version 1.1, was applied 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 was very low (0.71 ± 0.07 mSv for a standard injected dose of 100 MBq). The organ with the highest absorbed dose was the kidney (47.3 ± 10.2 mGy/100 MBq). The estimated effective dose was 2.32 ± 0.32 mSv for an injected dose of 20 MBq in newborns. This dose decreased to 0.77 ± 0.11 mSv/20 MBq for 1-y-old children and 0.59 ± 0.05 mSv for an injected dose of 30 MBq in 5-y-old children. Conclusion: Our human PET/CT-based dosimetric calculations show that the effective radiation doses from the novel tracer 68Ga-NODAGA-exendin-4 are very low for adults and children. 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 application as a research tool, especially when repeated examinations are needed.

Keywords: congenital hyperinsulinism; dosimetry; exendin-4; insulinoma; β-cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetates / chemistry*
  • Adult
  • Aged
  • Child, Preschool
  • Diabetes Mellitus, Type 1 / diagnostic imaging*
  • Diabetes Mellitus, Type 2 / diagnostic imaging*
  • Disease Progression
  • Exenatide / chemistry*
  • Female
  • Gallium Radioisotopes / chemistry*
  • Heterocyclic Compounds, 1-Ring / chemistry*
  • Humans
  • Image Processing, Computer-Assisted
  • Infant
  • Infant, Newborn
  • Insulin-Secreting Cells / pathology*
  • Kidney / diagnostic imaging
  • Male
  • Middle Aged
  • Pancreas / diagnostic imaging
  • Peptides / chemistry
  • Positron Emission Tomography Computed Tomography
  • Radiation Dosage
  • Radiometry / methods*
  • Radiopharmaceuticals / chemistry
  • Somatostatin / analogs & derivatives
  • Young Adult

Substances

  • 1-(1,3-carboxypropyl)-4,7-carboxymethyl-1,4,7-triazacyclononane
  • Acetates
  • Gallium Radioisotopes
  • Heterocyclic Compounds, 1-Ring
  • Peptides
  • Radiopharmaceuticals
  • Somatostatin
  • Exenatide