1D and 2D MTF Measurement for a Dual-Detector Image Receptor Using the Noise Response (NR) Method Compared with Using the Standard Edge Method
A Jain1*, X Wu2, S Setlur Nagesh2, A Shields2, N Artz1, D Bednarek2, S Rudin2, (1) Children's Mercy Kansas City, Kansas City, MO, (2) Canon Stroke and Vascular Research Center (CSVRC), Buffalo, NY
Presentations
PO-GePV-I-26 (Sunday, 7/25/2021) [Eastern Time (GMT-4)]
Purpose: To compare the modulation transfer functions (MTF) of a new dual-detector image receptor measured using the Noise-Response (NR) method and the standard edge-response method.
Methods: The NR method was used to measure both 1D and 2D MTF’s for the two built-in detectors of the Canon Alphenix system (194-micron pixel FPD and 76-micron pixel HiDef). A cascaded-linear-systems analysis based relationship between the noise power spectrum (NPS) and the MTF of a generalized detector system was used. A two-dimensional NPS was calculated for each detector at 7 different exposures (4 to 100 uR) with the RQA5 x-ray spectrum. To obtain the 2D MTF, the 1D MTF at each angle was determined using the radial component of the NPS at the corresponding angle. Each 1D NPS was plotted versus the mean signal level for all spatial frequencies; a linear regression was fitted to this data to isolate the quantum‐noise component, the shape of which partly depends on the system resolution. The spatial‐frequency response of the resulting slopes was used to obtain the corresponding 1D MTF. The set of 1D MTF’s over all angles provides the 2D MTF. The NR 1D MTF’s along the rows for both detectors were compared to those obtained using the standard edge-response method.
Results: The 1D MTF’s obtained using the noise and edge methods for both detectors agree within experimental uncertainty and demonstrate the improved resolution of the HiDef detector over the standard FPD. The 2D MTF shows the magnitude of reduced resolution along the diagonals.
Conclusion: The noise-response method is a simple technique which can be used to accurately measure the 2D MTF of digital x‐ray imagers, without the need for precision edge or slit devices. The unique capability of the NR method to provide a two-dimensional MTF provides more detailed detector/system characterization, including any potential non-isotropy.
Funding Support, Disclosures, and Conflict of Interest: This work is partially supported by NIH Grant 1R01EB030092
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