congratulation’s to emma and her co-authors on publishing their paper titiled
“comparative analysis of multilayer lead oxide-based x-ray detector prototypes”. this was
published in a sensors special issue advanced materials and technologies for radiation
detectors.

abstract

lead oxide (pbo) photoconductors are proposed as x-ray-to-charge transducers for the next
generation of direct conversion digital x-ray detectors. optimized pbo-based detectors have
potential for utilization in high-energy and dynamic applications of medical x-ray imaging. two
polymorphs of pbo have been considered so far for imaging applications: polycrystalline lead
oxide (poly-pbo) and amorphous lead oxide (a-pbo). here, we provide the comparative analysis
of two pbo-based single-pixel x-ray detector prototypes: one prototype employs only a layer of
a-pbo as the photoconductor while the other has a combination of a-pbo and poly-pbo, forming
a photoconductive bilayer structure of the same overall thickness as in the first prototype. we
characterize the performance of these prototypes in terms of electron–hole creation energy (w±)
and signal lag—major properties that define a material’s suitability for low-dose real-time
imaging. the results demonstrate that both x-ray photoconductive structures have an adequate
temporal response suitable for real-time x-ray imaging, combined with high intrinsic sensitivity.
these results are discussed in the context of structural and morphological properties of pbo to
better understand the preparation–fabrication–property relationships of this material.

continue reading the article: https://doi.org/10.3390/s22165998

the post congratulations to emma pineau for publishing a paper in sensors appeared first on rezniklab and posted by pavlo karasyuk.

congratulations tristan and co-authors on your published paper in the sensors special
issue advanced materials and technologies for radiation detectors. tristian’s paper is titled
“dark current modeling for a polyimide—amorphous lead oxide-based direct conversion x-
ray detector”.

abstract

the reduction of the dark current (dc) to a tolerable level in amorphous selenium (a-se) x-ray
photoconductors was one of the key factors that led to the successful commercialization of a-se-
based direct conversion flat panel x-ray imagers (fpxis) and their widespread clinical use. here,
we discuss the origin of dc in another x-ray photoconductive structure that utilizes amorphous
lead oxide (a-pbo) as an x-ray-to-charge transducer and polyimide (pi) as a blocking layer. the
transient dc in a pi/a-pbo detector is measured at different applied electric fields (5–20 v/μm).
the experimental results are used to develop a theoretical model describing the electric field-
dependent transient behavior of dc. the results of the dc kinetics modeling show that the dc,
shortly after the bias application, is primarily controlled by the injection of holes from the
positively biased electrode and gradually decays with time to a steady-state value. dc decays by
the overarching mechanism of an electric field redistribution, caused by the accumulation of
trapped holes in deep localized states within the bulk of pi. thermal generation and subsequent
multiple-trapping (mt) controlled transport of holes within the a-pbo layer governs the steady-
state value at all the applied fields investigated here, except for the largest applied field of 20 v/μm.

this suggests that a thicker layer of pi would be more optimal to suppress dc in the pi/a-
pbo detector presented here. the model can be used to find an approximate optimal thickness of
pi for future iterations of pi/a-pbo detectors without the need for time and labor-intensive
experimental trial and error. in addition, we show that accounting for the field-induced charge
carrier release from traps, enhanced by charge hopping transitions between the traps, yields an
excellent fit between the experimental and simulated results, thus, clarifying the dynamic process
of reaching a steady-state occupancy level of the deep localized states in the pi. practically, the
electric field redistribution causes the internal field to increase in magnitude in the a-pbo layer,
thus improving charge collection efficiency and temporal performance over time, as confirmed
by experimental results. the electric field redistribution can be implemented as a warm-up time
for a-pbo-based detectors.

continue reading the article: https://doi.org/10.3390/s22155829

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congratulations to justin stiles and brandon baldassi as well as the other co-workers in
publishing their paper “evaluation of a high-sensitivity organ-targeted pet camera”. their
paper was published in the sensors special issue advanced materials and technologies for
radiation detectors.

abstract

the aim of this study is to evaluate the performance of the radialis organ-targeted positron
emission tomography (pet) camera with standardized tests and through assessment of clinical-
imaging results. sensitivity, count-rate performance, and spatial resolution were evaluated
according to the national electrical manufacturers association (nema) nu-4 standards, with
necessary modifications to accommodate the planar detector design. the detectability of small
objects was shown with micro hotspot phantom images. the clinical performance of the camera
was also demonstrated through breast cancer images acquired with varying injected doses of 2-
[fluorine-18]-fluoro-2-deoxy-d-glucose (18f-fdg) and qualitatively compared with sample
digital full-field mammography, magnetic resonance imaging (mri), and whole-body (wb) pet
images. micro hotspot phantom sources were visualized down to 1.35 mm-diameter rods. spatial
resolution was calculated to be 2.3 ± 0.1 mm for the in-plane resolution and 6.8 ± 0.1 mm for the
cross-plane resolution using maximum likelihood expectation maximization (mlem)
reconstruction. the system peak noise equivalent count rate was 17.8 kcps at a 18f-fdg
concentration of 10.5 kbq/ml. system scatter fraction was 24%. the overall efficiency at the
peak noise equivalent count rate was 5400 cps/mbq. the maximum axial sensitivity achieved

was 3.5%, with an average system sensitivity of 2.4%. selected results from clinical trials
demonstrate capability of imaging lesions at the chest wall and identifying false-negative x-ray
findings and false-positive mri findings, even at up to a 10-fold dose reduction in comparison
with standard 18f-fdg doses (i.e., at 37 mbq or 1 mci). the evaluation of the organ-targeted
radialis pet camera indicates that it is a promising technology for high-image-quality, low-
dose pet imaging. high-efficiency radiotracer detection also opens an opportunity to reduce
administered doses of radiopharmaceuticals and, therefore, patient exposure to radiation.

continue reading the article: https://doi.org/10.3390/s22134678

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oleksandr grynko with co-authors: tristen thibault, emma pineau, and alla reznik
published a paper titled “the x-ray sensitivity of an amorphous lead oxide photoconductor” in
special issue: sensors and x-ray detectors. congratulations on the published paper!

abstract

the photoconductor layer is an important component of direct conversion flat panel x-ray
imagers (fpxi); thus, it should be carefully selected to meet the requirements for the x-ray
imaging detector, and its properties should be clearly understood to develop the most optimal
detector design. currently, amorphous selenium (a-se) is the only photoconductor utilized in
commercial direct conversion fpxis for low-energy mammographic imaging, but it is not
practically feasible for higher-energy diagnostic imaging. amorphous lead oxide (a-pbo)
photoconductor is considered as a replacement to a-se in radiography, fluoroscopy, and
tomosynthesis applications. in this work, we investigated the x-ray sensitivity of a-pbo, one of
the most important parameters for x-ray photoconductors, and examined the underlying
mechanisms responsible for charge generation and recombination. the x-ray sensitivity in terms
of electron–hole pair creation energy, w±, was measured in a range of electric fields, x-ray
energies, and exposure levels. w± decreases with the electric field and x-ray energy, saturating
at 18–31 ev/ehp, depending on the energy of x-rays, but increases with the exposure rate. the
peculiar dependencies of w± on these parameters lead to a conclusion that, at electric fields
relevant to detector operation (~10 v/μm), the columnar recombination and the bulk
recombination mechanisms interplay in the a-pbo photoconductor.

continue reading the article: https://doi.org/10.3390/s21217321

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