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Methods: The FPM system uses a Raspberry Pi computer and 196-LED matrix light source. FPM images were reconstructed using in-house Python code. The MTF was determined from bar-patterns using a least-squares analysis to fit a square wave, including odd-harmonic terms, to image profiles through the bars. These were normalized to larger uniform regions of the pattern and combined to generate the MTF.
Results: Total component cost of the FPM was less than $200. The theoretical diffraction limit imposed by the pupil function of this system was 280 cycles/mm, slightly less than the measured MTF 10% frequency of 300 cycles/mm. The 10% frequency in FPM images was 550 cycles/mm.
Conclusions: The USAF test pattern provides a practical method for assessing FPM performance in terms of the achieved MTF of the $200 Raspberry Pi based Fourier ptychography microscope. The limiting frequency in FPM images, 550 cycles/mm, was slightly less than the Nyquist sampling cut-off frequency of 670 cycles/mm imposed by pixel spacing.
A linear systems description of multi-compartment pulmonary 129Xe magnetic resonance imaging methods
Frequency-dependent MTF and DQE of photon-counting x-ray imaging detectors (Conference Presentation)
Signal and noise analysis of flat-panel sandwich detectors for single-shot dual-energy x-ray imaging
Medical x-ray imaging systems must be designed to ensure that maximum image quality is obtained for a specified radiation dose to the patient, and quality assurance programs are used to ensure these standards are maintained. This course is designed for anyone who wants to extend their understanding of how image quality is related to detector design and what that implies: how to talk about it, how to think about it, how to measure it and how to compare it. Performance metrics including the MTF, NPS, NEQ and DQE in digital radiography and mammography will be discussed. A cascaded-systems analysis will be used to help interpret the DQE of some real systems. The DQE of photon-counting systems, and the impact of detector limitations, will be discussed. Both non-mathematical intuitive descriptions and more rigorous mathematical descriptions will be presented.
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