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.
Introduction Congenital hyperinsulinism is characterized by abnormal regulation of insulin secretion from the pancreas causing profound hypoketotic hypoglycemia and is the leading cause of persistent hypoglycemia in infants and children. The main objective of this study is to highlight the different mechanisms to interpret the 18 F-DOPA PET scans and how this can influence outcomes. Materials and methods After 18 F-Fluoro-L-DOPA was injected intravenously into 50 subjects’ arm at a dose of 2.96–5.92 MBq/kg, three to four single-bed position PET scans were acquired at 20, 30, 40 and 50-minute post injection. The radiologist interpreted the scans for focal and diffuse hyperinsulinism using a visual interpretation method, as well as determining the Standard Uptake Value ratios with varying cut-offs. Results Visual interpretation had the combination of the best sensitivity and positive prediction values. Conclusions In patients with focal disease, SUV ratios are not as accurate in identifying the focal lesion as visual inspection, and cases of focal disease may be missed by those relying on SUV ratios, thereby denying the patients a chance of cure. We recommend treating patients with diazoxide-resistant hyperinsulinism in centers with dedicated multidisciplinary team comprising of at least a pediatric endocrinologist with a special interest in hyperinsulinism, a radiologist experienced in interpretation of 18 F-Fluoro-L-DOPA PET/CT scans, a histopathologist with experience in frozen section analysis of the pancreas and a pancreatic surgeon experienced in partial pancreatectomies in patients with hyperinsulinism.
Malignant peripheral nerve sheath tumor (MPNST) is an uncommon mesenchymal neoplasm of neural origin. MPNST arising in the uterus is extremely rare. Its histologic appearance on this anatomical location has been only rarely reported. A 62-yr-old woman with a previous history of partial hysterectomy presented with a large pelvic mass in the uterine stump. Fine-needle aspiration (FNA) and core biopsy were obtained under ultrasonographic guidance, and the diagnosis of MPNST was established. The cytologic and histologic findings were consistent with a spindle-cell neoplasm suggestive of MPNST. The tumor cells were focally positive for S-100 protein immunostain, thus providing further support for the neoplasm's nerve sheath differentiation. The patient had no history of von Recklinghausen's disease. Resection of the mass confirmed the diagnosis of MPNST. To our knowledge, the FNA cytology of MPNST in this unusual location has not been previously reported. FNA cytology, along with core biopsy and immunochemistry, is a reliable tool in the diagnosis of MPNST.
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