Abstract
The aim of this study is to assess the radiation absorbed dose of 18F-Fluoro-L-DOPA derived from the Positron Emission Tomography (PET) images of infants age ranging from 2 weeks– 32 weeks and a median age of 4.84 weeks (Mean 10.0 ± 10.3 weeks) with congenital hyperinsulinism.MethodsAfter injecting 25.6 ± 8.8 MBq (0.7 ± 0.2 mCi) of 18F-Fluoro-L-DOPA intravenously, three static PET scans were acquired at 20, 30, and 40 min post injection in 3-D mode on 10 patients (6 male, 4 female) with congenital hyperinsulinism. Regions of interest (ROIs) were drawn over several organs visible in the reconstructed PET/CT images and time activity curves (TACs) were generated. Residence times were calculated using the TAC data. The radiation absorbed dose for the whole body was calculated by entering the residence times in the OLINDA/EXM 1.0 software.ResultsThe mean residence times for the 18F-Fluoro-L-DOPA in the liver, lungs, kidneys, muscles, and pancreas were 11.54 ± 2.84, 1.25 ± 0.38, 4.65 ± 0.97, 17.13 ± 2.62, and 0.89 ± 0.34 min, respectively. The mean effective dose equivalent for 18F-Fluoro-L-DOPA was 0.40 ± 0.04 mSv/MBq. The CT scan used for attenuation correction delivered an additional radiation dose of 5.7 mSv. The organs receiving the highest radiation absorbed dose from 18F-Fluoro-L-DOPA were the urinary bladder wall (2.76 ± 0.95 mGy/MBq), pancreas (0.87 ± 0.30 mGy/MBq), liver (0.34 ± 0.07 mGy/MBq), and kidneys (0.61 ± 0.11 mGy/MBq). The renal system was the primary route for the radioactivity clearance and excretion.ConclusionsThe estimated radiation dose burden from 18F-Fluoro-L-DOPA is relatively modest to newborns.
Highlights
18F-Fluoro-L-DOPA is a radiofluorinated analogue of the amino acid L-dihydroxyphenylalanine (L-DOPA)
The estimated radiation dose burden from 18F-Fluoro-L-DOPA is relatively modest to newborns
L-DOPA is a neutral amino acid analogue and in certain tissues it is converted to Ldopamine by the aromatic amino-acid decarboxylase (AADC) which enables its entry and accumulation in the catecholamine storage vesicles [5]
Summary
18F-Fluoro-L-DOPA is a radiofluorinated analogue of the amino acid L-dihydroxyphenylalanine (L-DOPA) This compound plays a significant role in the study of dopaminergic function in the human brain using PET [1,2] especially for the objective measure of disease severity [3,4]. L-DOPA accumulates in neuroendocrine cells and in pancreatic islet cells after conversion to L-dopamine through the action of AADC [6,7,8] For such reasons, 18F-Fluoro-L-DOPA PET has found its role in assessing the altered AADC activity in pancreatic β-cell from increased insulin synthesis and hypersecretion of insulin by these cells in patients with congenital hyperinsulinism (CHI) [8,9,10]. In addition to its accuracy in diagnosing focal form of CHI noninvasively, the 18F-Fluoro-L-DOPA PET has been more accurate in differentiating focal and diffuse disease than invasive procedures such as trans-hepatic portal venous insulin sampling (THPVS) and arterial calcium stimulation with hepatic vein insulin sampling (ASVS) [24]
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