Purpose: It is well accepted that details of blood flow can influence the formation and progression of vessel pathologies such as aneurysms and stenoses. High Speed Angiography (HSA) at 1000 fps can provide detailed flow pattern images that were previously unavailable during neuro-interventional procedures. To derive such flow information, it is important to have the ability to control the rate and volume of contrast injection. In this work we present injection techniques performed by using a computer-controlled syringe injector and the resulting flow pattern.
Methods: A 3D-printed neuro-vascular model was connected in a flow loop with a 40% glycerol and 60% water solution used as the circulating fluid. An Aries single photon counting detector (Direct Conversion Inc.) with a pixel size of 100 μm and FOV of 7.5cmx5cm was used to acquire HSA or digital subtraction HSA sequences at 1000 fps. A KD Scientific Legato 110 syringe injector was used to inject 100% iodine-contrast agent in the flow loop. The flow patterns were evaluated for both pulsed injections (rate: 100 ml/min; injection duration: 80ms; time between injections: 120ms; total number of injections: 15; duration of image acquisition: 1.5s ) and continuous injections (rate 100 ml/min; total injection duration : 2s; duration of image acquisition: 1.5s).
Results: Pulsing the injections results in consistent formation of glob-like features when the contrast comes out of the catheter. These structures can be used by tracking algorithms to generate velocity profiles in the vasculature and subsequent wall-shear-stress determination. However, a continuous injection fills up the vessel and does not result in any trackable features that can be used for velocity determination.
Conclusion: A properly controlled contrast injection technique that creates trackable contrast media discontinuities (globs) is necessary to be able to visualize details in the flow patterns when performing HSA at 1000- fps speeds.