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Validation of Linear Velocity Independence of Rotating Fan Blade Method of Temporal MTF Estimation

M Russ1*, S Mann1, T Richards2, E Samei1,2, (1) Duke University Health System, Durham, NC, (2) Duke University (RAILabs), Durham, NC

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: temporal performance of cardiac catheterization fluoroscopic systems is critical to prevent blurring due to anatomical motion from degrading image quality. A method to evaluate system temporal modulation transfer function (TMTF) using a rotating fan-blade phantom has been previously presented. The goal of this study was to ensure the validity of the constant angular velocity approach, which, in contrast to the translating edge method, includes a range of linear velocities, creating differential blurring along the fan-blade phantom edge.


Methods: experiment was conducted using a Philips Alura FD10 system. Cine images of static and rotating fan-blades were acquired to determine the separable components of the spatio-temporal MTF. Previous calculations of the TMTF with this phantom have utilized a single broad circular ROI, encompassing a wide range of linear velocities. This study employed seven narrower ROIs, spanning the usable range of the phantom edge. Narrow ROIs limit the range of linear velocities included in each measurement. Results were examined for velocity-dependent deviations.


Results: measured TMTFs exhibited the expected sinc function shape, with bounce point consistent with the x-ray pulse width. TMTFs measured from all seven sub-ROIs demonstrated minimal deviation from each other, with average absolute percent deviation of 1.3% between the inner- and outer-most ROIs up to the Nyquist frequency. There was good agreement shown between the TMTFs determined from smaller ROIs and the large full-width ROI; the average percent deviation between each narrow ROI and the large ROI was less than 1%.


Conclusion: consistency of TMTFs derived from sub-sections of the phantom moving at differing linear velocities confirms the validity of using a constant angular velocity approach to estimating the TMTF. The temporal resolution information gained from this method makes it a valuable tool that fits into a suite of advanced metrics that can be employed for comprehensive fluoroscopic system comparisons.

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