New family of generalized metrics for comparative imaging system evaluation

Russ, Megan; Singh, Vivek Kumar; Loughran, B; Bednarek, Daniel R.; Rudin, Stephen

doi:10.1117/12.2082014

Cited by 3 publications

(3 citation statements)

References 5 publications

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“…To quantify the advantage of the smaller effective focal spot size, the Generalized Measured Relative Object Detectability (GM-ROD) metric 4 was employed. The GM-ROD metric, as shown in Eq.…”

Section: Methodsmentioning

confidence: 99%

Focal spot size reduction using asymmetric collimation to enable reduced anode angles with a conventional angiographic x-ray tube for use with high resolution detectors

Russ

Nagesh

Ionita

et al. 2017

Medical Imaging 2017: Physics of Medical Imaging

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The high-resolution requirements for neuro-endovascular image-guided interventions (EIGIs) necessitate the use of a small focal-spot size; however, the maximum tube output limits for such small focal-spot sizes may not enable sufficient x-ray fluence after attenuation through the human head to support the desired image quality. This may necessitate the use of a larger focal spot, thus contributing to the overall reduction in resolution. A method for creating a higher-output small effective focal spot based on the line-focus principle has been demonstrated and characterized. By tilting the C-arm gantry, the anode-side of the x-ray field-of-view is accessible using a detector placed off-axis. This tilted central axis diminishes the resultant focal spot size in the anode-cathode direction by the tangent of the effective anode angle, allowing a medium focal spot to be used in place of a small focal spot with minimal losses in resolution but with increased tube output. Images were acquired of two different objects at the central axis, and with the C-arm tilted away from the central axis at 1° increments from 0°–7°. With standard collimation settings, only 6° was accessible, but using asymmetric extended collimation a maximum of 7° was accessed for enhanced comparisons. All objects were positioned perpendicular to the anode-cathode direction and images were compared qualitatively. The increasing advantage of the off-axis focal spots was quantitatively evidenced at each subsequent angle using the Generalized Measured-Relative Object Detectability metric (GM-ROD). This anode-tilt method is a simple and robust way of increasing tube output for a small field-of-view detector without diminishing the overall apparent resolution for neuro-EIGIs.

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Section: Methodsmentioning

confidence: 99%

Focal spot size reduction using asymmetric collimation to enable reduced anode angles with a conventional angiographic x-ray tube for use with high resolution detectors

Russ

Nagesh

Ionita

et al. 2017

Medical Imaging 2017: Physics of Medical Imaging

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“…The previously presented ROD metric 4,5,6 that utilizes the ideal observer model is defined as the integral over spatial frequencies of the Fourier transform of an object function weighted by the detector DQE for one detector, then divided by the comparable integral for another detector, as shown in Equation 1.…”

Section: Methodsmentioning

confidence: 99%

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)

et al. 2016

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A novel amorphous selenium (a-Se) direct detector with CMOS readout has been designed, and relative detector performance investigated. The detector features include a 25μm pixel pitch, and 1000μm thick a-Se layer operating at 10V/μm bias field. A simulated detector DQE was determined, and used in comparative calculations of the Relative Object Detectability (ROD) family of prewhitening matched-filter (PWMF) observer and non-prewhitening matched filter (NPWMF) observer model metrics to gauge a-Se detector performance against existing high resolution micro-angiographic fluoroscopic (MAF) detectors and a standard flat panel detector (FPD). The PWMF-ROD or ROD metric compares two x-ray imaging detectors in their relative abilities in imaging a given object by taking the integral over spatial frequencies of the Fourier transform of the detector DQE weighted by an object function, divided by the comparable integral for a different detector. The generalized-ROD (G-ROD) metric incorporates clinically relevant parameters (focal-spot size, magnification, and scatter) to show the degradation in imaging performance for detectors that are part of an imaging chain. Preliminary ROD calculations using simulated spheres as the object predicted superior imaging performance by the a-Se detector as compared to existing detectors. New PWMF-G-ROD and NPWMF-G-ROD results still indicate better performance by the a-Se detector in an imaging chain over all sphere sizes for various focal spot sizes and magnifications, although a-Se performance advantages were degraded by focal spot blurring. Nevertheless, the a-Se technology has great potential to provide breakthrough abilities such as visualization of fine details including of neuro-vascular perforator vessels and of small vascular devices.

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“…The product of DQE and |OBJ (u, v)| 2 was integrated up to the Nyquist frequency of each detector. The ROD of the two detectors was calculated by the ratio of the two integrals for a given object [29][30][31].…”

Section: Jinst 11 P03022mentioning

confidence: 99%

Characterizing X-ray detectors for prototype digital breast tomosynthesis systems

Kim

Park

et al. 2016

J. Inst.

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The digital breast tomosynthesis (DBT) system is a newly developed 3-D imaging technique that overcomes the tissue superposition problems of conventional mammography. Therefore, it produces fewer false positives. In DBT system, several parameters are involved in image acquisition, including geometric components. A series of projections should be acquired at low exposure. This makes the system strongly dependent on the detector's characteristic performance.This study compares two types of x-ray detectors developed by the Korea Electrotechnology Research Institute (KERI). The first prototype DBT system has a CsI (Tl) scintillator/CMOS based flat panel digital detector (2923 MAM, Dexela Ltd.), with a pixel size of 0.0748 mm. The second uses a-Se based direct conversion full field detector (AXS 2430, analogic) with a pixel size of 0.085 mm. The geometry of both systems is same, with a focal spot 665.8 mm from the detector, and a center of rotation 33 mm above the detector surface. The systems were compared with regard to modulation transfer function (MTF), normalized noise power spectrum (NNPS), detective quantum efficiency (DQE) and a new metric, the relative object detectability (ROD). The ROD quantifies the relative performance of each detector at detecting specified objects.The system response function demonstrated excellent linearity (R 2 > 0.99). The CMOSbased detector had a high sensitivity, while the Anrad detector had a large dynamic range. The higher MTF and noise power spectrum (NPS) values were measured using an Anrad detector. The maximum DQE value of the Dexela detector was higher than that of the Anrad detector with a low exposure level, considering one projection exposure for tomosynthesis. Overall, the Dexela detector performed better than did the Anrad detector with regard to the simulated Al wires, spheres, test objects of ROD with low exposure level.In this study, we compared the newly developed prototype DBT system with two different types of x-ray detectors for commercial DBT systems. Our findings suggest that the Dexela detector can be applied to the DBT system with regard to its high imaging performance.

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New family of generalized metrics for comparative imaging system evaluation

Cited by 3 publications

References 5 publications

Focal spot size reduction using asymmetric collimation to enable reduced anode angles with a conventional angiographic x-ray tube for use with high resolution detectors

Focal spot size reduction using asymmetric collimation to enable reduced anode angles with a conventional angiographic x-ray tube for use with high resolution detectors

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)

Characterizing X-ray detectors for prototype digital breast tomosynthesis systems

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