Experimental characterization of a direct conversion amorphous selenium detector with thicker conversion layer for dual‐energy contrast‐enhanced breast imaging

Scaduto, David A.; Tousignant, O.; Zhao, Wei

doi:10.1002/mp.12358

Cited by 7 publications

(16 citation statements)

References 36 publications

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“…We show that the MTF is degraded by oblique incidence. This result is consistent with previous works on both direct‐ and indirect‐converting detectors . The MTF degradation is most pronounced along the ray incidence direction.…”

Section: Discussionsupporting

confidence: 92%

“…With this approach, we find that the NPS is white. Previous work has demonstrated that, at low energy, the NPS is effectively white . However, in high‐energy applications, it has been shown that the NPS exhibits more pronounced dependency on frequency .…”

Section: Discussionmentioning

confidence: 99%

“…This result is consistent with previous works on both direct-and indirect-converting detectors. [1][2][3][4][5]9,25,26 The MTF degradation is most pronounced along the ray incidence direction. There is no MTF degradation along the perpendicular direction.…”

Section: Discussionmentioning

confidence: 99%

“…The MTF was calculated with a digital breast tomosynthesis (DBT) system using a tungsten edge. 3,4 Previous works have also shown that increasing the thickness of selenium results in more substantial MTF degradation. 3,5 This arises because the incident ray traverses a broader path length through the x-ray converter, yielding more blurring.…”

Section: Introductionmentioning

confidence: 99%

“…X‐ray experiments in previous works have validated the MTF degradation due to oblique incidence. The MTF was calculated with a digital breast tomosynthesis (DBT) system using a tungsten edge . Previous works have also shown that increasing the thickness of selenium results in more substantial MTF degradation .…”

Section: Introductionmentioning

confidence: 99%

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Nonstationary model of oblique x‐ray incidence in amorphous selenium detectors: II. Transfer functions

Acciavatti

Maidment

2019

Medical Physics

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Purpose One limitation of experimental techniques for quantifying resolution and noise in detectors is that the measurement is made in a region‐of‐interest (ROI). With theoretical modeling, these properties can be measured at a point, allowing for quantification of spatial anisotropy. This paper calculates nonstationary transfer functions for amorphous selenium (a‐Se) detectors in breast imaging. We use this model to demonstrate the performance advantage of a “next‐generation” tomosynthesis (NGT) system, which is capable of x‐ray source motion with more degrees of freedom than a clinical tomosynthesis system. Methods Using Swank's formulation, the optical transfer function (OTF) and presampled noise power spectra (NPS) are determined based on the point spread function derived in Part 1. The modulation transfer function (MTF) is found from the normalized modulus of the OTF. To take into account the presence of digitization, the presampled NPS is convolved with a two‐dimensional comb function, for which the period along each direction is the reciprocal of the detector element size. The detective quantum efficiency (DQE) is then determined from combined knowledge of the OTF and NPS. Results First, the model is used to demonstrate the loss of image quality due to oblique x‐ray incidence. The MTF is calculated along various polar angles, corresponding to different orientations of the input frequency. The MTF is independent of the incidence angle if the polar angle is perpendicular to the ray incidence direction. However, along other polar angles, oblique incidence results in MTF degradation at high frequencies. The MTF degradation is most substantial along the ray incidence direction. Unlike the MTF, the normalized NPS (NNPS) is independent of the incidence angle. To measure the relative signal‐to‐noise, the DQE is also calculated. Oblique incidence yields high‐frequency DQE degradation, which is more pronounced than the MTF degradation. This arises because the DQE is proportionate with the square of the MTF. Ultimately, this model is used to evaluate how the image quality varies over the detector area. For various projection images, we calculate the variation in the incidence angle over this area. With the NGT system, the source can be positioned in such a way that this variation is minimized, and hence the DQE exhibits less anisotropy. To achieve this improvement in the image quality, the source needs to have a component of motion in the posteroanterior (PA) direction, which is perpendicular to the conventional direction of source motion in tomosynthesis. Conclusions In a‐Se detectors, the DQE at high frequencies is degraded due to oblique incidence. The DQE degradation is more pronounced than the MTF degradation. This model is used to quantify the spatial variation in DQE over the detector area. The use of PA source motion is a strategy for minimizing this variation and thus improving the image quality.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nonstationary model of oblique x‐ray incidence in amorphous selenium detectors: II. Transfer functions

Acciavatti

Maidment

2019

Medical Physics

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Printable Perovskite Diodes for Broad‐Spectrum Multienergy X‐Ray Detection

Shabbir

Warnakula

et al. 2023

Advanced Materials

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Multienergy X‐ray detection is critical to effectively differentiate materials in a variety of diagnostic radiology and nondestructive testing applications. Silicon and selenium X‐ray detectors are the most common for multienergy detection; however, these present poor energy discrimination across the broad X‐ray spectrum and exhibit limited spatial resolution due to the high thicknesses required for radiation attenuation. Here, an X‐ray detector based on solution‐processed thin‐film metal halide perovskite that overcomes these challenges is introduced. By harnessing an optimized n‐i‐p diode configuration, operation is achieved across a broad range of soft and hard X‐ray energies stemming from 0.1 to 10's of keV. Through detailed experimental and simulation work, it is shown that optimized Cs0.1FA0.9PbI3 perovskites effectively attenuate soft and hard X‐rays, while also possessing excellent electrical properties to result in X‐ray detectors with high sensitivity factors that exceed 5 × 103 µnormalC boldnormalGyVac−1 cm−2$\mu {\rm{C}}\;{{\bf Gy}}_{{\rm{Vac}}}^{ - 1}\;{\rm{c}}{{\rm{m}}^{ - 2}}$ and 6 × 104 µC Gy−1 cm−2 within soft and hard X‐ray regimes, respectively. Harnessing the solution‐processable nature of the perovskites, roll‐to‐roll printable X‐ray detectors on flexible substrates are also demonstrated.

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Investigation of spectral performance for single‐scan contrast‐enhanced breast CT using photon‐counting technology: A phantom study

Ruth

Kolditz²,

Steiding³

et al. 2020

Medical Physics

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Purpose: Contrast-enhanced imaging of the breast is frequently used in breast MRI and has recently become more common in mammography. The purpose of this study was to make single-scan contrast-enhanced imaging feasible for photon-counting breast CT (pcBCT) and to assess the spectral performance of a pcBCT scanner by evaluating iodine maps and virtual non-contrast (VNC) images. Methods: We optimized the settings of a pcBCT to maximize the signal-to-noise ratio between iodinated contrast agent and breast tissue. Therefore, an electronic energy threshold dividing the x-ray spectrum used into two energy bins was swept from 23.17 keV to 50.65 keV. Validation measurements were performed by placing syringes with contrast agent (2.5 mg/ml to 40 mg/ml) in phantoms with 7.5 cm and 12 cm in diameter. Images were acquired at different tube currents and reconstructed with 300 lm isotropic voxel size. Iodine maps and VNC images were generated using image-based material decomposition. Iodine concentrations and CT values were measured for each syringe and compared to the known concentrations and reference CT values. Results: Maximal signal-to-noise ratios were found at a threshold position of 32.59 keV. Accurate iodine quantification (average root mean square error of 0.56 mg/ml) was possible down to a concentration of 2.5 mg/ml for all tube currents investigated. The enhancement has been sufficiently removed in the VNC images, so they can be interpreted as unenhanced CT images. Only minor changes of CT values compared to a conventional CT scan were observed. Noise was increased by the decomposition by a factor of 2.62 and 4.87 (7.5 cm and 12 cm phantoms) but did not compromise the accuracy of the iodine quantification. Conclusions: Accurate iodine quantification and generation of VNC images can be achieved using contrast-enhanced pcBCT from a single CT scan in the absence of temporal or spatial misalignment. Using iodine maps and VNC images, pcBCT has the potential to reduce dose, shorten examination and reading time, and to increase cancer detection rates.

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Experimental characterization of a direct conversion amorphous selenium detector with thicker conversion layer for dual‐energy contrast‐enhanced breast imaging

Cited by 7 publications

References 36 publications

Nonstationary model of oblique x‐ray incidence in amorphous selenium detectors: II. Transfer functions

Nonstationary model of oblique x‐ray incidence in amorphous selenium detectors: II. Transfer functions

Printable Perovskite Diodes for Broad‐Spectrum Multienergy X‐Ray Detection

Investigation of spectral performance for single‐scan contrast‐enhanced breast CT using photon‐counting technology: A phantom study

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