4D Computed Tomography Cardiovascular Flow Imaging

Tech ID: L-19-007

Background

Computed Tomography (CT) is routinely used for anatomical assessment in patients with vascular and valvular diseases. Since blood flow assessment is also critical for optimizing the management of these patients, CT is often used in conjunction with other imaging tests for further disease evaluation, but this approach leads to ineffective clinical workflow. A novel CT image analysis method is developed to facilitate a one-stop anatomical and functional diagnosis with CT. This method does not require computationally expensive simulation and allows quantitative blood flow measurement at a very high temporal resolution to unmask the underlying blood flow characteristics related to various vascular and valvular diseases.

Technology Overview

The two current non-simulation based CT methods for blood flow velocity measurement are either impractical for clinical use or suboptimal for the diagnosis of some cardiac diseases. One approach is based on the measurement of the time difference in peak contrast enhancement at two locations along the same blood vessel. However, the flow velocity in a larger artery (such as the aorta) is approximately 50 to 100 centimeters per second (cm/s) or higher, making this approach impractical for flow measurement in patients. The other approach estimates flow velocity based on the area under the dye concentration-time curve measured in a blood vessel, but the temporal resolution of this approach is limited by the duration of the concentration-time curve, which is usually 20 seconds or longer. Such temporal resolution is insufficient for resolving the pulsation in flow velocity within a cardiac cycle, which provides valuable information about the cardiac pumping function and the stiffness of a blood vessel. We have overcome this limitation by developing an advanced algorithm that allows absolute flow measurement at a very high temporal resolution with contrast-enhanced CT images, and this new technology has been validated in flow phantom, large animal and patient studies with promising results. Our preliminary results show that this new technology can resolve the difference in absolute aortic flow velocity (cm/s) within 100 milliseconds (0.1 seconds). In comparison, the temporal resolution of the area under the curve approach is usually limited to 20000 milliseconds (20 seconds).

Benefits/Applications

• Measurement of absolute blood flow velocity at a very high temporal resolution without the need of intensive computer simulation.
• Generation of pulsatile flow velocity profile of a blood vessel over a single cardiac cycle. This velocity profile may be useful for assessing cardiac pumping function and vascular stiffness, with these metrics closely related to aging and hypertension.
• Our preliminary results also suggest that the pulsatile flow velocity profile is useful in evaluating the severity of aortic stenosis without the need of Doppler echocardiography.

Keywords

Computed tomography (CT), dynamic imaging, quantitative blood flow measurement, high temporal resolution

Patent Status: PCT/CA2021/051189

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