Dynamic 3D imaging of contrast medium flow on an interventional C-arm using a pulsed injection protocol

This study investigates a method of time resolved 3D (4D) x-ray imaging of contrast dynamics internal to a vascular structure (e.g. intracranial aneurysm) to enable evaluation of blood flow patterns during an interventional procedure. The proposed method employs repetitive-short-pulse injection of small contrast boluses, rotational x-ray imaging with a C-arm, and retrospectively-gated iterative image reconstruction. Under conditions where the passage of each contrast pulse through a vascular region is repeatable and the C-arm rotation is slow compared to the injection cycle, each flow state (spatial distribution of contrast agent at an instant) is imaged at multiple projection angles. After partitioning the projections by flow state, a sequence of 3D volumes corresponding to different states of contrast passage can be reconstructed. Feasibility was demonstrated in a patient-specific 3D-printed aneurysm phantom with 1 Hz simulated cardiac flow waveform. A custom-built power injector was programmed to produce repetitive 100ms injections of iodinated contrast agent upstream of the aneurysm, synchronized to the mid-diastolic phase of the simulated cardiac cycle (1 Hz, 0.4 mL/pulse, 20 pulses, 8 mL total). An interventional C-arm short-scan was performed with 11.3 s rotation time and 27fps frame rate. Modified PICCS reconstruction was used to generate the 4D images. The temporal evolution of contrast agent in the 4D x-ray images was visually similar to the flow patterns observed in MRI imaging and CFD simulation of the same phantom. 95% of the surface deviations between the 4D aneurysm volume and traditional 3D-DSA aneurysm volume were within -0.02 ± 0.24 mm