Micro-Bolus Iodine Contrast-Media Injection Method for 1000 fps High-Speed Angiography

The high temporal resolution of 1000 fps High-Speed Angiography (HSAngio) allows for detailed quantification of hemodynamics, as influenced by the cardiac cycle. To quantify hemodynamics from HSAngio images, we developed a novel method for injecting micro-boluses of contrast-media using a rotating valve during a narrow 300-500 ms imaging window. Such information can be used by physicians to assess vascular disease severity and treatment strategies. A programmable motor-controlled-valve (MCV) was connected between a MedRad contrast-injector and catheter. Contrast-media flow was broken-up with controlled valve rotations to generate distinct micro-boluses. To measure micro-bolus reproducibility, tubing mimicking the internal-carotid-artery (ICA) was connected to a flow loop filled with a 40/60 glycerol-water mixture cycled by a pump at 245 ml/min, as measured by a flowmeter. The MedRad injected contrast at 2 ml/s for one second. Two MCV speeds, 120 and 150 RPM, were used separately to generate 240 and 300 micro-boluses per minute, respectively. Sequences of 300 continuous 1-ms frames capturing micro-bolus flow through the ICA-tubing were acquired for each rotation speed using an Aries Photon-Counting Detector (Varex Imaging). From each sequence, time-density curves (TDCs) for three regions within the ICA-tubing were derived. The maximum standard deviation of area under the curves (AUCs) of the TDCs for four separate injections was 12.3%. For velocity calculated from the TDCs, it was 3.6%. Since the AUCs correlate to the contrast-media volume passing through each region, this low variation demonstrates good micro-bolus production reproducibility, allowing for consistent velocity analysis within individual cardiac cycle phases using HSAngio.