Influence of subcutaneous administration of rapid-acting insulin in the quality of (18)F-FDG PET/CT studies.

Objective: The aim of this study was to develop a protocol for normalizing blood glucose levels in diabetic patients by subcutaneously administering rapid-acting insulin before administering (18)F-fluorodeoxyglucose ((18)F-FDG) without hindering the quality of PET/computed tomography (CT) studies.

Materials And Methods: The study included 120 patients, who were divided into four groups: Group I: This group comprised 30 diabetic patients with blood glucose levels lower than 160 mg/dl at the time of arrival at our center; in these patients, (18)F-FDG was injected without prior administration of subcutaneous rapid-acting insulin. Group II: This group comprised 30 diabetic patients with blood glucose levels ranging from 168 to 260 mg/dl; in these patients, subcutaneous rapid-acting insulin was administered and then (18)F-FDG was injected when blood glucose levels dropped below 160 mg/dl (30-115 min). Group III: This group included 30 diabetic patients with blood glucose levels ranging from 192 to 324 mg/dl; in these patients, subcutaneous rapid-acting insulin was administered and then (18)F-FDG was injected 4 h later. Blood glucose levels dropped below 160 mg/dl (range, 58-159 mg/dl) in all patients.

Control Group: This group included 30 nondiabetic patients with normal blood glucose levels (72-104 mg/dl). We calculated the mean standardized uptake value (SUV) of muscle from the maximum SUV in five consecutive axial slices in the proximal middle third of the rectus femoris muscle of the right thigh.

Results: The quality of the PET-CT studies was considered suboptimal when muscle uptake was more than 2 SDs greater than the mean muscle uptake in the control group (1.15±0.2). The mean SUV of muscle was as follows: Group I, 1.09 (σ=0,26); group II, 1.98 (σ=0,32); group III, 1.98 (σ=1,13); and control group IV, 1.15 (σ=0,2). The quality of PET-CT studies was considered suboptimal in 18 patients in group II (60%) and in four patients (13%) in group I. The quality was optimal in all studies conducted in group III patients.

Conclusion: Subcutaneous administration of rapid-acting insulin normalizes blood glucose levels without compromising the quality of PET-CT studies when (18)F-FDG is administered not earlier than 4 h later.