Visual interpretation, not SUV ratios, is the ideal method to interpret 18F-DOPA PET scans to aid in the cure of patients with focal congenital hyperinsulinism.

IntroductionCongenital 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 18F-DOPA PET scans and how this can influence outcomes.Materials and methodsAfter 18F-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.ResultsVisual interpretation had the combination of the best sensitivity and positive prediction values.ConclusionsIn 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 18F-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

Pancreatic uptake and radiation dosimetry of 6-[18F]fluoro-L-DOPA from PET imaging studies in infants with congenital hyperinsulinism.

After 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.The 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.The estimated radiation dose burden from 18F-Fluoro-L-DOPA is relatively modest to newborns

Mean values from time activity curves for organs easily delineable on ¹⁸F-Fluoro-L-DOPA PET scans from patients with hyperinsulinism (n = 10).

<p>While a slightly higher uptake of radioactivity is noted at all scan time points in male subjects, these differences were statistically insignificant (p>0.1). Radioactivity levels decreased marginally between 20 min and 40 min.</p

¹⁸F-fluoro-L-DOPA PET/CT scan showing the focal and diffuse uptake pattern in the pancreas axial (left) and coronal (right) view of ¹⁸F-Fluoro-L-DOPA scans from two representative subjects with hyperinsulinism.

<p>The top row shows a diffuse uptake of ¹⁸F-Fluoro-L-DOPA in the pancreas and the bottom row shows an intense focal accumulation of ¹⁸F-Fluoro-L-DOPA in the pancreas. Both the images were acquired at ~20 min post ¹⁸F-Fluoro-L-DOPA injection.</p

The uptake and distribution of ¹⁸F-fluoro-L-DOPA at 20, 30 and 40 min in a male and a female subject.

<p>Coronal views of representative PET images from a male (left) and a female subject (right). PET scans were acquired at ~20 min (top row), ~30 min (middle row), and ~40 min (bottom row) after injecting ¹⁸F-Fluoro-L-DOPA. For each row, the left image is an anterior view and the right image is the posterior view. Major organs such as kidneys, liver, pancreas and urinary bladder are clearly visible on early images (20 min). The uptake intensity in the organs decreases slightly with time, except for the urinary bladder.</p

The time activity curves generated by fitting an expontial function to the PET data for the pancreas, liver, and kidneys.

<p>The initial portion of the curve (prior to 20 min PET scan value) was modeled to fit to a peak uptake at 5 min. The time activity curve past the 40 min scan measured value was assumed to be depleted only by the physical decay of F-18 radionuclide.</p

Radiation dose estimates for ¹⁸F-Fluoro-L-DOPA in newborns (Mean ± SD).

<p>Radiation dose estimates for ¹⁸F-Fluoro-L-DOPA in newborns (Mean ± SD).</p

Residence times calculated from whole body¹⁸F-Fluoro-L-DOPA PET images acquired in newborns with hyperinsulinism.

<p>Residence times calculated from whole body¹⁸F-Fluoro-L-DOPA PET images acquired in newborns with hyperinsulinism.</p

Pancreatic uptake and radiation dosimetry of 6-[¹⁸F]fluoro-L-DOPA from PET imaging studies in infants with congenital hyperinsulinism

<div><p>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.</p><p>Methods</p><p>After 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.</p><p>Results</p><p>The 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.</p><p>Conclusions</p><p>The estimated radiation dose burden from ¹⁸F-Fluoro-L-DOPA is relatively modest to newborns.</p></div