Design considerations for a new high resolution Micro-Angiographic Fluoroscope based on a CMOS sensor (MAF-CMOS)

Abstract

The detectors that are used for endovascular image-guided interventions (EIGI), particularly for neurovascular interventions, do not provide clinicians with adequate visualization to ensure the best possible treatment outcomes. Developing an improved x-ray imaging detector requires the determination of estimated clinical x-ray entrance exposures to the detector. The range of exposures to the detector in clinical studies was found for the three modes of operation: fluoroscopic mode, high frame-rate digital angiographic mode (HD fluoroscopic mode), and DSA mode. Using these estimated detector exposure ranges and available CMOS detector technical specifications, design requirements were developed to pursue a quantum limited, high resolution, dynamic x-ray detector based on a CMOS sensor with 50 μm pixel size. For the proposed MAF-CMOS, the estimated charge collected within the full exposure range was found to be within the estimated full well capacity of the pixels. Expected instrumentation noise for the proposed detector was estimated to be 50–1,300 electrons. Adding a gain stage such as a light image intensifier would minimize the effect of the estimated instrumentation noise on total image noise but may not be necessary to ensure quantum limited detector operation at low exposure levels. A recursive temporal filter may decrease the effective total noise by 2 to 3 times, allowing for the improved signal to noise ratios at the lowest estimated exposures despite consequent loss in temporal resolution. This work can serve as a guide for further development of dynamic x-ray imaging prototypes or improvements for existing dynamic x-ray imaging systems.

Evaluation of the microangiographic fluoroscope (MAF) using generalized system performance metrics

“…[27][28][29][30] These developing CMOS detectors have lower noise and enable smaller pixel sizes than TFT-based FPDs and thus may well have performance characteristics competitive with the MAF. Furthermore, FPDs using avalanche-mode amorphous selenium (a-Se) are being investigated and may be able to provide high spatial resolution and low dose quantum noise limited response.…”

Quantitative comparison using generalized relative object detectability (G-ROD) metrics of an amorphous selenium detector with high resolution microangiographic fluoroscopes (MAF) and standard flat panel detectors (FPD)

“…The MAF-CCD and MAF-CMOS are high resolution indirect detectors that utilize a CsI(Tl) phosphor of 500 μ m and 600 μ m, respectively, for x-ray detection 13,14,15 . The MAF-CCD detector uses a CCD camera with 12 μ m pixel size coupled to a fiber optic taper with a 2.88:1 ratio, giving an effective pixel size of 35 μ m and effective circular field of view 3.6cm in diameter.…”

Detector system comparison using relative CNR for specific imaging tasks related to neuro-endovascular image-guided interventions (neuro-EIGIs)

“…Typically, the temporal filter weight ranges from ω =3 to ω = 5, corresponding to a reduction in image noise of 0.33 to 0.45 times the non-temporally filtered background noise [12] . Therefore, the CNR for a temporally filtered image taken with the MAF will increase 2.24 to 3 times depending on the temporal filter weight used in the image acquisition [13] . However, this temporal filter feature is disabled for images used for contrast and noise measurements.…”