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CT angiographic measurement of vascular blood flow velocity by using projection data.

PURPOSE
To determine whether flow velocity can be measured by using projection data from computed tomographic (CT) scans obtained during contrast material injection in a phantom model.


MATERIALS AND METHODS
The authors constructed a 12.7-mm-diameter single-channel flow phantom with constant water flow velocity settings of 25.3, 43.9, and 70.5 cm/sec. For each flow velocity, serial axial scans were obtained with 16-section multidetector CT while a 10-mL bolus of contrast material was injected upstream of the imaging plane. For each bolus injection, the CT projection data from the scan with the sharpest increase in magnitude of detected contrast material was used for flow velocity measurements. Flow velocity was calculated as the ratio of distance between CT detector rows and the corresponding time lag in the contrast enhancement curves and was correlated with the reference velocities. Five separate contrast material injections and CT measurements were made for each flow velocity setting.


RESULTS
The correlation coefficient between the CT measurements of flow velocity and the reference measurements was 0.98 (P < .05). The mean CT measurements of flow velocity were 34.2, 53.9, and 80.8 cm/sec for slow, moderate, and fast velocity settings, respectively, overestimating the corresponding actual flow velocities by 26%, 18%, and 13% and showing precision values (coefficients of variation) of 5.2%, 3.7%, and 6.6%.


CONCLUSION
Flow velocity can be measured from row-to-row multidetector CT projectional data obtained during a single gantry revolution as a bolus of contrast material flows through a vascular phantom. With further development, this novel technique could potentially provide physiologic information to complement the anatomic CT angiographic findings of vascular disease.