Program Information
Performance Assessment of Clinical X-Ray Angiography Systems Using a Channelized Hotelling Observer Model
K Fetterly1*, (1) Mayo Clinic, Rochester, MN
Presentations
WE-AB-601-9 (Wednesday, August 2, 2017) 7:30 AM - 9:30 AM Room: 601
Purpose: The purpose of this work was to investigate the potential for a channelized Hotelling model observer (CHO) to assess performance of clinical x-ray angiography systems.
Methods: Detectability index (d’) of 19 clinical x-ray angiography systems representing 3 models was estimated using a CHO and 300 unprocessed images of 0.5 to 4.0 mm diameter iodinated disks embedded within a 25 cm thick PMMA phantom. X-ray control parameters included 91 kVp, a 0.3 mm Cu spectral filter, and detector target dose (DTD) 6, 18, and 120 nGy. The CHO included correction of bias from finite sampling and temporally variable electronic noise. Phantom entrance dose measurements acquired with a 6 cc ionization chamber were used to correct d’ variation due to x-ray output variation between systems. d’ was estimated with and without the anti-scatter grid, thereby permitting estimation of the SNR improvement factor (SNRIF) of the grid.
Results: For object diameter 4 mm and DTD 120 nGy, d’ of the systems ranged from 19.3 to 25.1. Compared to expectations of a quantum limited system, d’ for small objects was reduced due to focal spot penumbral and detector blur, and d’ for low DTD was reduced due to electronic noise. Compared to the other 17 systems, two systems with new technology detectors demonstrated 15% d’ improvement for DTD = 120 nGy and 47% improvement for DTD = 6 nGy. The average SNRIF of the anti-scatter grids was 4% (-3% to 7%).
Conclusion: The CHO is sensitive to physical determinants of image quality for angiography systems and is suitable for characterizing performance differences between systems. Changes in d’ due to variable DTD, system blur, detector electronic readout noise, and the anti-scatter grid were demonstrated. d’ estimates of systems with a new detector technology indicated superior performance for both high and very low DTD conditions.
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