Focus f 120

Myocardial rates of FDG uptake (Ki) were determined by dynamic 2‐[18F] fluoro‐2‐deoxy‐D‐glucose (18F‐FDG) PET imaging of SHR and WKY rats using the Siemens Focus F 120 microPET scanner as we described for mice.5, 6 Briefly, rats were fasted for 6 hours with free access to water before FDG imaging. They were then subjected to a 60‐minute dynamic PET scan under 2% isoflurane anesthesia. Data acquisition was initiated a few seconds before the slow (over 20 seconds) administration of 1 to 1.5 millicurie (mCi) FDG via a tail‐vein catheter. A Small Animal Gating Instrument (model 1025L for PET) was used to continuously monitor heart rate, respiration, and core body temperature. For attenuation correction a transmission scan using a Co57 point source was done before FDG administration. The list mode data was sorted into 23 time bins (frames×time in seconds (11×8, 1×12, 2×60, 1×180, 8×400 seconds) and the sinograms reconstructed with attenuation correction using filtered back projection algorithms (ramp filter cutoff at the Nyquist frequency).5, 6

After administration of radioactive tracers, the mice were scanned with a MicroPET scanner (Focus F‐120, Siemens) at 5, 15, 25, 35, 45, 55, 90, and 120 minutes under anesthesia with 1.5% to 3% isoflurane. MicroPET Manager (version 2.4.1.1, Siemens) was used to reconstruct MicroPET data using the OSEM3D/MAP algorithm (zoom factor, 2.164). The data processing software ASIProvm was used to draw the organs of each tissue as regions of interest, and the percentage of radioactive uptake concentration (μCi/mL) of each region of interest to the injection dose (100 μCi/mL) was the tissue or organ uptake ratio.

Glucose uptake into BAT was quantified by PET analysis of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake. Procurement of FDG was from PETNET Solutions, Inc. of Charlottesville, VA. The mice were fasted overnight before PET/CT studies. On the day of imaging, mice were given an intraperitoneal injection of CL316243 (1 mg/kg b. wt). Thirty minutes after injection of CL316243, ¹⁸F-FDG (100 μCi) was administered through tail vein injection under isoflurane anesthesia. Imaging was performed 90 min later under the same anesthesia while maintaining body temperature using a Focus F-120 small-animal microPET scanner (Siemens Medical Solutions, Inc.) following a previously published protocol [33 (link)]. Each PET acquisition was performed for 10 min. PET images were reconstructed from raw data with the OSEM3D/MAP algorithm (zoom factor, 2.164) using microPET Manager (version 2.4.1.1, Siemens). The reconstructed pixel size was 0.28 × 0.28 × 0.79 mm on a 128 × 128 × 95 image matrix. All PET images were normalized to decay correction but not for attenuation. Each image analysis was performed using ASIPRO software (Siemens) for presentation. The final PET images were used for quantitative estimates of the accumulation of ¹⁸F-FDG in the regions of interest (ROI) of BAT, and the maximum standardized uptake values (SUV) were calculated from the maximum pixel value in the image slice.