Program Information
Comparison of 50 μm and 75 μm Pixel Pitch Indirect CMOS Detectors for Use in Neuro-Endovascular Image Guided Interventions
M Russ*, A Shankar , D Bednarek , S Rudin , Toshiba Stroke and Vascular Research Center, Univ. at Buffalo (SUNY) School of Med., Buffalo, NY
Presentations
SU-E-702-7 (Sunday, July 30, 2017) 1:00 PM - 1:55 PM Room: 702
Purpose: Neuro-endovascular image-guided interventions (neuro-EIGIs) depend on x-ray guidance to safely treat vascular pathology, and sufficient resolution must be ensured for visualization of fine vascular device detail. The potential advantage of a high resolution fluoroscopic (HRF) CMOS indirect detector with 50μm pixel pitch compared to one with 75μm pixel pitch is examined.
Methods: Standard metrics analysis of the 75μm HRF-CMOS75 and a new 49.5μm pixel detector prototype, the HRF-CMOS₅₀, was performed. The HRF-CMOS₇₅ detector features 600μm CsI phosphor thickness and a minimum sensitivity of 9.87 DN/μR, while the HRF-CMOS₅₀ has a 300μm phosphor and 1.91 DN/μR sensitivity. The dissimilarity in detector characteristics does not make for a fair comparison focused on pixel size. To improve the similarity between the two detectors, the HRF-CMOS₅₀ was simulated to have a 500μm CsI phosphor for frequency-dependent metrics analysis, including modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) calculation.
Results: The MTF of the simulated 500μm HRF-CMOS₅₀ showed the high spatial frequency degradation expected from increased blurring in the phosphor compared to the 300μm HRF-CMOS₅₀. Both the measured and simulated HRF-CMOS₅₀ MTFs indicate better spatial resolution performance than the HRF-CMOS₇₅. For an exposure level of 40μR/frame, the simulated HRF-CMOS₅₀ showed improved noise performance over the measured HRF-CMOS₅₀, but both were outperformed by the HRF-CMOS₇₅. As consequence, the DQE of the HRF-CMOS₇₅ showed substantial advantage over both HRF-CMOS₅₀ detectors, including a 28% advantage of the HRF-CMOS₇₅ at its Nyquist frequency.
Conclusion: To draw conclusions regarding the advantage of a detector with 50μm pixels compared to 75μm pixels, other dissimilarities between the detectors must be minimized. Currently, the HRF-CMOS₅₀ does not have the sensitivity or noise performance that the HRF-CMOS₇₅ has, and its clear resolution advantage of having smaller pixels is lost at noise-limited lower exposure levels.
Funding Support, Disclosures, and Conflict of Interest: Partial support from NIH grant R01-EB002873, cooperation from Teledyne Dalsa Inc., and an equipment grant from Toshiba Medical Systems Corp.
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