Optiray

The shuttle-mode scans were acquired 5s after a 50mL nonionic contrast agent bolus (ioversol [Optiray], 320mg of iodine per milliliter; Mallinckrodt, Inc., St Louis, Mo) was administered using an automatic injector (MCT/MCT Plus; Medrad, Pittsburg, Pa) at a rate of 7mL/s. Ten phases of cine scans were acquired where each phase of the CT perfusion scan (120 kVp, 220 mA, 8.42 mGy) was 2.8s long with a 1.4s lag between table position scans as shown in the timeline of the acquisition in Figure 1. The figure also illustrates that the two table position scans were acquired from non-overlapping volumes, such that there was a 5mm z-axis distance between the most inferior table position 1 slice and the most superior table position 2 slice. The images were reconstructed to eight slices per table position with a 5 mm thickness resulting in a total coverage of 80 mm along the cranio-caudal (z) direction considering both table position scans. A 27s breath hold was imposed to minimize breathing motion during the scan.

PET and CT data of each animal was acquired within 24 h of the MR scans. The mice were anesthetized with 2 % isoflurane and positioned in a microPET Focus 220 (Siemens, Knoxville, TN). Dynamic PET data was acquired for 60 min following a retro-orbital administration of ~ 18 MBq/0.2 ml [¹⁸F]VUIIS1008. The dynamic data were binned into the following variable length frames: twelve 5-s frames, four 60-s frames, one 5-min frame, and five 10-min frames. The MAP algorithm was used to reconstruct the data into 128 × 128 × 95 slices with a voxel size of 0.095 × 0.095 × 0.08 cm³ at a beta value of 0.01. CT scans were next acquired to facilitate anatomic co-registration of the PET and MRI data. Mice were imaged in an Inveon CT (Siemens preclinical, Knoxville TN) following an IP injection of ~ 0.2 ml of the contrast agent Optiray (Mallinckrodt Inc., St. Louis, MO), which enables visualization of the bladder. Note that TSPO ligands are not cleared via the kidneys [13 (link)]. The CT data was collected using the following parameters: beam intensity = 180 mAs, tube voltage = 80 kVp, reconstructed image matrix = 512 × 512 × 512, and voxel size = 0.1 × 0.1 × 0.1 mm³.

The area covered by the chest CT examination extended from the apex to the base of the lung, including the chest wall and axillary fossa. The first dataset, which consisted of preoperative and postoperative CT scans of 122 nodules, was acquired using a 64-MDCT system (GE LightSpeed VCT or GE Discovery CT750 HD, GE Healthcare), with use of the following parameters: section width, 1.25 mm; reconstruction interval, 1.25 mm; pitch, 0.984; tube voltage, 120 kV; tube current, 250 mA; display FOV, 28 × 28 cm to 36 × 36 cm; matrix size, 512 × 512; and pixel size, 0.55–0.7 mm. All patients received a bolus of 80–100 mL of IV contrast medium (350 mg I/mL; Optiray, Mallinckrodt) administered at a rate of 3–4 mL/s with the use of a power injector via an 18- or 20-gauge cannula in an antecubital vein. The postoperative CT scan was acquired 60 seconds after the administration of contrast medium. Both standard and high-resolution reconstruction kernels were used for image reconstructions. The second dataset, which consisted only of unenhanced CT images of 126 nodules, was acquired using either a 16-MDCT system (Sensation 16, Siemens Healthcare) with use of a section width of 1 mm, a reconstruction interval of 1 mm, pitch of 1, tube voltage of 120 kV, and tube current of 150 mA or a 64-MDCT system (GE Discovery CT750 HD, GE Healthcare) with use of the same parameters used for preoperative CT.