Inveon small animal pet scanner

PET scans were performed by using Inveon small-animal PET scanner (Siemens Preclinical Solution). About 7.4 MBq of [⁶⁸Ga]Ga-FAPI-RGD was given to Panc02 tumor xenografted mice through tail vein injection for the 10-min static PET imaging. At 0.5, 1, 2 and 4 h post-injection (p.i.), mice were anaesthetized and placed on imaging chamber of PET/CT scanner for image acquisition. For comparison, [⁶⁸Ga]Ga-FAPI-02 and [⁶⁸Ga]Ga-RGDfK were intravenously injected to Panc02 tumor mice and PET imaging was performed at 0.5, 1 and 2 h p.i. The blocking study was performed by injecting unlabeled c(RGDfK), FAPI-02, or RGDfK+FAPI-02, before administering [⁶⁸Ga]Ga-FAPI-RGD. PET images were reconstructed using three-dimensional ordered-subset expectation-maximization (3D OSEM) algorithm and with a Maximum a Posteriori (MAP) method and analyzed through drawing regions of interest (ROIs).

In vivo imaging studies were performed using a Siemens Inveon small-animal PET scanner. Mice were injected into the tail vein with app. 0.9–1 MBq of the respective ¹⁸F-labeled compound under isoflurane anesthesia. For competition experiments, 2-PMPA (1 μmol = 226 μg/mouse) was coinjected. Dynamic images were recorded for 1.5 h after on-bed injection. Reconstruction of the images was carried out using three-dimensional ordered-subsets expectation maximum algorithm without scanner and attenuation correction. Data analysis was carried out using Inveon Workplace software.

Firstly, we prepared DFO modified PEG-T^ECM-NS with crosslinked structure (DFO-PEG-T^ECM-NS). As a control, we also prepared N-PEG-T^ECM-NS without crosslinked structure DFO-N-PEG-T^ECM-NS. Zr⁸⁹-DFO-PEG-T^ECM-NS, and Zr⁸⁹-DFO-N-PEG-T^ECM-NS were intravenously injected into the 4T1 tumour-bearing mice. An Inveon small-animal PET scanner (Siemens, Erlangen, Germany) was used to acquire whole-body PET images at predetermined time points after injection.

PA imaging, SCNPs aqueous solution (3.00 mg mL⁻¹, 100 μL) was i.v. injected into the HeLa tumour-bearing mice. PA imaging of tumour was performed on an Endra Nexus 128 PA tomography system (Endra, Inc., Ann Arbor, MI). Photothermal imaging was detected by using a SC300 infrared camera when the tumours were irradiated with 671 nm laser (0.5 W cm⁻²) for 5 min.
SCNPs were labelled with radioactive copper (⁶⁴Cu) by mixing ⁶⁴CuCl₂ with SCNPs@DOTA at 37 °C for 1 h under constant stirring. As detected by thin-layer chromatography, the radiolabeling yield of SCNPs@DOTA was determined to be as high as 98%. For PET imaging, ⁶⁴Cu SCNPs@DOTA (150 μCi, 100 μL) was intravenously injected into the HeLa tumour-bearing mice. The mice were anaesthetised with isoflurane (1.0 ~ 2.0%) in oxygen delivered at a flow rate of 1.0 L min⁻¹. All PET imagings were carried out on Inveon small-animal PET scanner (Siemens, Erlangen, Germany) at different times post-injection. For each in vivo PET scan, 3D volumes of interest were drawn over the tumour and muscle on decay-corrected whole-body coronal images, which were analysed by Inveon Research Workplace. Standards were prepared and the tumour uptake was determined as percent of injected dose per gram of tissue.

The products of ⁶⁸Ga-DOTA-2P(FAPI)₂ and ⁶⁸Ga-FAPI-46 were diluted to a concentration of 74 MBq/mL, and 7.4 MBq (bout 0.1 mL) of ⁶⁸Ga-DOTA-2P(FAPI)₂ or ⁶⁸Ga-FAPI-46 were intravenously injected into HCC-PDXs (n = 3 for each group). All PET scans were conducted using an Inveon small-animal PET scanner (Siemens Preclinical Solution). Dynamic and static PET imaging procedures are provided in the supplemental materials.
In the biodistribution study, the products of ⁶⁸Ga-DOTA-2P(FAPI)₂ and ⁶⁸Ga-FAPI-46 were diluted to a concentration of 14.8 MBq/mL. HCC-PDX mice were injected with the same batch of 1.48-MBq ⁶⁸Ga-DOTA-2P(FAPI)₂ and killed at different times (1 and 4 h after injection; n = 3 for each time point). The main organs and tumors were isolated, weighed, and analyzed. The biodistribution in the ⁶⁸Ga-FAPI-46 group (1.48 MBq) and the blocking group (⁶⁸Ga-DOTA-2P(FAPI)₂ [1.48 MBq] with 30 nmol of unlabeled FAPI-46) was also evaluated for comparison. The radioactivity (counts per minute) was measured with a γ-counter.