Model 55 2222

Anesthesia was induced with Telazol (4.4 mg/kg), Ketamine (2.2 mg/kg), and Xylazine (2.2 mg/kg), and was maintained with 1.5–2.5% Isoflurane (Highland Medical Equipment, Temecula, CA and Baxter, Deerfield, IL). Sheaths were placed (AVANTI®, Cordis Corporation, Miami Lakes, FL) in both femoral veins for intravenous adenosine and contrast administration. In three of the animals, an extra sheath was placed in the right carotid artery to pass a Judkins Right (JR) catheter (Cordis Corporation, Miami Lakes, FL) into the left coronary ostium. A pressure wire (PrimeWire PRESTIGE® Pressure Guide Wire, Volcano Corp, Rancho Cordova, CA) was then advanced into the distal LAD. A balloon was passed over the wire into the mid LAD and was used to generate several levels of sub-occlusive stenosis with FFR (ComboMap, Volcano Corp., Rancho Cordova, CA) severities of 0.7–0.9 under maximal vasodilation (240 µg adenosine/kg/min, Model 55-2222, Harvard Apparatus, Holliston, MA). Beta blockers were not administered for heart rate control and nitroglycerin was not administered during CTA.

For each animal, one or two rest acquisitions were performed, followed by one to three stress acquisitions, all with the same CT settings. For each stress acquisition, adenosine was infused intravenously for 3 min prior to and throughout imaging (240 μg adenosine/kg/min, Model 55-2222, Harvard Apparatus, Holliston, MA, USA). For each rest and stress acquisition, 1 mL/kg of contrast material (Isovue 370, Bracco Diagnostics, Princeton, NJ, USA) was injected (5 mL/s, Empower CTA, Acist Medical Systems, Eden Prairie, MN, USA) followed by a saline chaser (0.5 mL/kg) at the same rate. ECG-gated volume scans were acquired dynamically with a 320-slice CT scanner (Aquilion One, Toshiba America Medical Systems, Tustin, CA, USA) over 20–30 s to capture base and peak of the aortic enhancement, as shown in Fig. 1a, b. All volume scans were acquired as full projection data at 100 kVp and 200 mA with a rotation time of 0.35 s, a collimation of 320 × 0.5 mm, and a cranio-caudal coverage of 16 cm. A minimum 10-min delay was employed between consecutive acquisitions to allow for adequate clearance of contrast material and, if used, adenosine. All volume scans were retrospectively reconstructed at 75% of the R-R interval using an adaptive iterative dose reduction three-dimensional reconstruction [24 (link)], an FC03 kernel, and a voxel size of 0.43 × 0.43 × 0.5 mm.