Accuracy of PET/CT Scan in the diagnosis of the focal form of congenital hyperinsulinism

Purpose: The purpose of the study was to determine the sensitivity of the (18)fluoro-dihydroxyphenylalanine positron emission tomography/computed tomography scan (18F-PET/CT) in the diagnosis of focal congenital hyperinsulinism (HI).

Methods: A retrospective review of children with HI who underwent a preoperative 18F-PET/CT scan was performed.

Results: Between 1/2008 and 2/2012 we performed 105 consecutive 18F-PET/CT scans on infants with HI. Fifty-three patients had focal HI. Of those fifty-three patients, eight had a preoperative 18F-PET/CT scan read as "diffuse disease". The sensitivity of the study in the diagnosis of focal HI was 85%. The location of the eight missed focal lesions was: head (3), body (2), and tail (3). The 18F-PET/CT of the missed head lesions showed homogeneous tracer uptake (n =2) or heterogeneous uptake throughout the pancreas (n=1). The 18F-PET/CT of the 2 missed body lesions and 1 missed tail lesion showed heterogeneous uptake throughout the pancreas. The 18F-PET/CT of the other 2 missed tail lesions showed lesions adjacent to and obscured by the signal of the upper renal pole, identified retrospectively by closer observation. Fifty-two of the 105 patients had diffuse HI. Two of them had 18F-PET/CT studies read as "focal disease". Therefore, the specificity of the study was 96%. Of the forty-seven 18F-PET/CT studies read as "focal disease", forty-five had true focal HI. Therefore, the positive predictive value of the study in the diagnosis of focal HI was 96%.

Conclusion: The sensitivity and specificity of 18 F-PET/CT can be affected by certain anatomic features of the pancreas, by the location of the lesion, and by the reader's experience.