18F-DOPA PET and enhanced CT imaging for congenital hyperinsulinism: initial UK experience from a technologist’s perspective

INTRODUCTIONCongenital hyperinsulinism (CHI) is the most common cause of persistent hypoglycaemia in infants and children. Histologically, there are two subgroups, diffuse and focal. The aim of this study was to evaluate the accuracy of F-fluoro-L-dihydroxyphenylalanine (F-DOPA) PET/computed tomography (CT) and contrast-enhanced CT in distinguishing between focal and diffuse lesions in infants with CHI who are unresponsive to medical therapy. In addition, this paper describes the detailed protocol used for imaging and analysis of F-DOPA PET/CT images in our clinical practice. MATERIALS AND METHODSTwenty-two F-DOPA PET/CT and contrast-enhanced CT imaging studies were carried out on 18 consecutive patients (nine boys and nine girls) with CHI (median age, 2 years and 1 month; range, 1–84 months) who had positive dominant ABCC8 mutation genetic results or negative ABCC8/t results but did not respond to first-line medical therapy with high-dose diazoxide. F-DOPA was produced by the cyclotron unit of Woolfson Molecular Imaging Centre, Manchester, and transported to our centre in central London after synthesis and implementation of quality control measures. F-DOPA was administered intravenously at a dose of 4 MBq/kg, and iodine contrast medium was injected intravenously at a dose of 1.5 ml/kg. Single bed position PET/CT images of the pancreas were acquired under light sedation with oral chloral hydrate. Four PET dynamic data acquisition scans were taken 20, 40, 50 and 60 min after injection for a duration of 10 min each. The results were assessed by visual interpretation and quantitative measurements of standardized uptake values (SUVs) in the head, body, and tail of the pancreas. RESULTSOf the 18 patients, 13 showed diffuse and five showed focal F-DOPA PET pancreatic uptake. Three regions of interest were drawn over the head, body and tail of the pancreas to calculate the SUVmax. Using the formula – highest SUVmax/next highest SUVmax – a ratio was calculated. Five patients had an accumulation of F-DOPA in the pancreas and an SUV ratio greater than 1.5, indicating focal disease with an SUVmax more than 50% higher than that of the unaffected areas of the pancreas. The remaining 13 patients had diffuse accumulation of F-DOPA in the pancreas (SUV ratio