Abstract
3084
Objectives: To determine the best radiotracer bolus injection technique for total-body dynamic-imaging on the uEXPLORER PET/CT. This technique may prove beneficial for other molecular imaging studies currently using bolus injection techniques. uEXPLORER PET/CT is the world’s first total-body scanner capable of simultaneously capturing radiotracer bolus injection and distribution throughout the entire body in real-time.
Methods: Seven healthy subjects were scanned on the uEXPLORER PET/CT after giving informed consent. All subjects were positioned for a 60-minute dynamic scan with arms down. A small-bore 1.5cc extension tube was primed with saline and attached to an upper extremity IV. A 3-way Luer valve connected to a 10cc saline flush and approximately 0.5mCi F18-FDG radiotracer was attached to the extension tubing. Two different bolus methods were used on the 7 subjects. Method 1: Prior to imaging, pre-load the radiotracer into the extension tubing, ensuring the volume is less than 1.5cc. The radiotracer syringe is then backflushed and loaded with normal saline. With the 3-way Luer valve “off” to the saline flush, begin the PET acquisition and inject the backflushed radiotracer syringe to the patient. Immediately turn the 3-way Luer valve “off” to the radiotracer syringe and inject the remaining 10cc saline flush to the patient. Method 2: with the 3-way Luer valve turned so that all 3 connections are open, begin the PET acquisition and inject the radiotracer syringe to the patient. Immediately inject the remaining 10cc saline to the patient without adjusting the Luer valve. The SUVmax within the extension tubing/IV was collected using a 4-minute reconstruction from 1-5 minutes post injection for all 7 subjects. After collecting this patient data, both methods were tested using blue-tinged saline in place of the radiotracer to visually determine efficiency and concentration of the bolus within the tubing.
Results: Five subjects were injected using Method 1, with an SUVmax of 14.4, 7.99, 0.41, 13.15, and 1.76 respectively. Two subjects were injected using Method 2, with an SUVmax of 176 and 323 respectively. Both Method 1 and Method 2 were each tested twice using the blue-tinged saline. Both tests for Method 1 had a highly concentrated dose analog at the beginning of the bolus, with the extension tubing visually clear of dye after a 2-3cc flush of 100% normal saline. Both tests for Method 2 had a diluted concentration of the dose analog over the entire duration of the bolus, with visual dye still left in the extension tubing after 10cc normal saline flush. Blue dye (dose analog) was also observed contaminating the 100% normal saline flush syringe.
Conclusions: Subjects injected using Method 1 had an average SUVmax of 7.54, while Method 2 produced an average SUVmax of 249.5 (33 fold higher than Method 1). It is evident using a blue dye dose analog that Method 1 produces a more concentrated and efficient bolus with minimal residual within the extension tubing. Due to Method 2 allowing complete and open flow from radiotracer to the saline flush, this method has a high chance of diluting the radiotracer bolus and leaving residual radiotracer in the extension tubing and saline flush.
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