Flat-panel X-ray Imaging Research Articles

Bottom-up construction of low-dimensional perovskite thick films for high-performance X-ray detection and imaging

Quasi-two-dimensional (Q-2D) perovskite exhibits exceptional photoelectric properties and demonstrates reduced ion migration compared to 3D perovskite, making it a promising material for the fabrication of highly sensitive and stable X-ray detectors. However, achieving high-quality perovskite films with sufficient thickness for efficient X-ray absorption remains challenging. Herein, we present a novel approach to regulate the growth of Q-2D perovskite crystals in a mixed atmosphere comprising methylamine (CH3NH2, MA) and ammonia (NH3), resulting in the successful fabrication of high-quality films with a thickness of hundreds of micrometers. Subsequently, we build a heterojunction X-ray detector by incorporating the perovskite layer with titanium dioxide (TiO2). The precise regulation of perovskite crystal growth and the meticulous design of the device structure synergistically enhance the resistivity and carrier transport properties of the X-ray detector, resulting in an ultrahigh sensitivity (29721.4 μC Gyair−1 cm−2) for low-dimensional perovskite X-ray detectors and a low detection limit of 20.9 nGyair s−1. We have further demonstrated a flat panel X-ray imager (FPXI) showing a high spatial resolution of 3.6 lp mm−1 and outstanding X-ray imaging capability under low X-ray doses. This work presents an effective methodology for achieving high-performance Q-2D perovskite FPXIs that holds great promise for various applications in imaging technology.

The fabrication and characterization of direct conversion flat panel X-ray imager with TlBr film

The novel direct conversion flat panel detectors (FPDs) utilizing thallium bromide (TlBr) films are developed and characterized in this study. Thin TlBr films, deposited using an evaporation technique, achieved thicknesses of 10 μm and 50 μm. A pixel sensor array, with a pixel size of 235 × 235 μm2 and a sensitive area of 29.61 × 39.48 mm2, was developed using low-temperature polysilicon thin-film transistor (LTPS TFT) technology as the initial study to explore performance characteristics of developed imaging system. The TlBr film was characterized based on the current-voltage (I–V) profile, showing a resistivity of 2.78 × 1010 Ω·cm. The LTPS TFT showed a leakage current of about 10−13 A, while the noise of TlBr FPD system was around 104 e− rms, primarily limited by the readout system. The detector system was characterized using radiation from an X-ray tube with a voltage in the range of 30 kV–100 kV and a current of 2 mA, involving an X-ray test chart as the object with the processing time of 18.15–18.30 ms per frame. Based on the contrast and contrast-to-noise ratio (CNR) values, the 10 μm and 50 μm TlBr FPD clearly captured the image in operation between 30 kV and 100 kV. The 50 μm TlBr FPD demonstrated improved sensitivity, showing pixel values with 10 times higher intensity and enhanced line pair detail at 30 kV X-ray operation. The 10 μm TlBr achieved spatial resolution of 267 μm full width at half maximum (FWHM), while the 50 μm TlBr achieved 250 μm FWHM. In the X-ray imaging demonstration, the shape and structure of anchovy was clearly distinguished. The TlBr film FPD presents promising potential for a room temperature X-ray imager.

Low‐Dose and Stable X‐Ray Imaging Enabled by Low‐Dimensional Dion‐Jacobson Perovskites

AbstractMetal halide perovskites have emerged as highly promising candidates for next‐generation X‐ray detectors due to their facile and low‐cost processability, high attenuation coefficient, and tunable optoelectrical properties. In this work, quasi‐2D Dion‐Jacobson (DJ) perovskites are introduced in a flat panel X‐ray imager (FPXI) for X‐ray imaging. This study demonstrates that the diammonium interlayers in DJ perovskites play a key role in enhancing structural stability, suppressing ion migration, and improving charge transport. As a result, DJ perovskite‐based X‐ray FPXIs achieve a sensitivity of 18000 µC Gyair−1 cm−2, a low detection limit of 5.7 nGyair s−1, representing performance comparable to that of state‐of‐the‐art 3D perovskite FPXIs. Thanks to the decrease in the signal crosstalk effect of the FPXIs, a high spatial resolution of 0.54 line‐pair‐per‐pixel is achieved, which is higher than that of 3D perovskite FPXIs. Remarkably, high‐quality X‐ray imaging is achieved at a total dose of 20 µGyair, which is only 1/5 of the dose typically used in commercial equipment. This work not only provides valuable insights and guidance for the fabrication of 2D DJ perovskite X‐ray detectors but also lays the groundwork for the adoption of high‐performance, stable DJ perovskite imagers as novel flat‐panel X‐ray detectors.

Organic and Inorganic Metal Halide Tandem Scintillator for Dual-Energy Flat-Panel X-ray Imaging.

Traditional indirect flat-panel X-ray imaging (FPXI) uses inorganic scintillators with high-Z elements, which lack spectral information about X-ray photons and reflect only integrated X-ray intensity. To address this issue, we developed a stacked scintillator structure that combines organic and inorganic materials. This structure allows X-ray energies to be distinguished in a single shot by using a color or multispectral visible camera. However, the resolution of the resulting dual-energy image is primarily limited by the top scintillator layer. We inserted a layer of anodized aluminum oxide (AAO) between the double scintillators. This layer limits the lateral propagation of scintillation light, improves imaging resolution, and acts as a filter for X-rays. Our research demonstrates the advantages of stacked organic-inorganic scintillator structures for dual-energy X-ray imaging and provides novel and practical applications for relatively low-Z organic scintillators with high internal X-ray-to-light conversion efficiency.

Multispectral Large-Panel X-ray Imaging Enabled by Stacked Metal Halide Scintillators.

Conventional energy-integration black-white X-ray imaging lacks the spectral information of X-ray photons. Although X-ray spectra (energy) can be distinguished by the photon-counting technique typically with CdZnTe detectors, it is very challenging to be applied to large-area flat-panel X-ray imaging (FPXI). Herein, multilayer stacked scintillators of different X-ray absorption capabilities and scintillation spectra are designed; in this scenario, the X-ray energy can be discriminated by detecting the emission spectra of each scintillator; therefore, multispectral X-ray imaging can be easily obtained by color or multispectral visible-light camera in a single shot of X-rays. To verify this idea, stacked multilayer scintillators based on several emerging metal halides are fabricated in a cost-effective and scalable solution process, and proof-of-concept multispectral (or multi-energy) FPXI are experimentally demonstrated. The dual-energy X-ray image of a "bone-muscle" model clearly shows the details that are invisible in conventional energy-integration FPXI. By stacking four layers of specifically designed multilayer scintillators with appropriate thicknesses, a prototype FPXI with four energy channels is realized, proving its extendibility to multispectral or even hyperspectral X-ray imaging. This study provides a facile and effective strategy to realize multispectral large-area flat-panel X-ray imaging.

Dark Current Modeling for a Polyimide-Amorphous Lead Oxide-Based Direct Conversion X-ray Detector.

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.

Compact and Large‐Area Perovskite Films Achieved via Soft‐Pressing and Multi‐Functional Polymerizable Binder for Flat‐Panel X‐Ray Imager

AbstractThanks to its strong X‐ray absorption and large carrier diffusion length, perovskites have demonstrated excellent performance for X‐ray detection. Combination of perovskite with thin‐film transistor (TFT) arrays to construct flat‐panel X‐ray imager (FPXI) is required for X‐ray imaging, yet this is rarely reported. Solution processing of perovskite thick film onto TFT can enable the electronic connection, however the amounts of pinholes inevitably form during the solvent evaporation and result in a porous film with deteriorated performance and stability. Here a novel strategy is raised to achieve high‐quality perovskite thick films for TFT integration via soft‐pressing and in situ polymerization of multi‐functional binder (TMTA). The combined process largely eliminates the pinholes, improves the surface smoothness, passivates grains boundaries, reduces ionic migration, and improves stability. Accordingly, a compact and smooth MAPbI3 thick film integrating with TFT arrays is prepared for flat‐panel X‐ray imaging. The largest film (28 × 28 cm2) is obtained with the state‐of‐the‐art performance (ratio of sensitivity to noise current: 1.41 × 1011 µC Gy−1 A−1) among polycrystalline films. It is hoped that the work provides guidance for fabricating compact perovskite thick films and push perovskite FPXI one step further for low‐dose X‐ray imaging.

The X-ray Sensitivity of an Amorphous Lead Oxide Photoconductor.

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.

Nanoparticles: Untying the Gordian Knot in Conventional Computed Tomography Imaging

X-ray computed tomography (CT) imaging plays an essential role in disease diagnosis due to its noninvasive, painless mode and superior penetration depth. However, the resolution of the soft tissue ...

X-Ray Scatter Estimation Using Deep Splines.

X-ray scatter compensation is a very desirable technique in flat-panel X-ray imaging and cone-beam computed tomography. State-of-the-art U-net based scatter removal approaches yielded promising results. However, as there are no physics' constraints applied to the output of the U-Net, it cannot be ruled out that it yields spurious results. Unfortunately, in the context of medical imaging, those may be misleading and could lead to wrong conclusions. To overcome this problem, we propose to embed B-splines as a known operator into neural networks. This inherently constrains their predictions to well-behaved and smooth functions. In a study using synthetic head and thorax data as well as real thorax phantom data, we found that our approach performed on par with U-net when comparing both algorithms based on quantitative performance metrics. However, our approach not only reduces runtime and parameter complexity, but we also found it much more robust to unseen noise levels. While the U-net responded with visible artifacts, the proposed approach preserved the X-ray signal's frequency characteristics.

Effects of High-Dose X-Ray Irradiation on the Hole Lifetime in Vacuum-Deposited Stabilized a-Se Photoconductive Films: Implications to the Quality Control of a-Se Used in X-Ray Detectors

Stabilized amorphous selenium (a-Se)-based digital flat-panel X-ray imaging detectors are widely used in modern mammography. The dependence of the hole lifetime, $\tau _{h}$ , in a-Se on high-dose X-ray irradiation under high electric fields is examined. The X-ray-induced effects on the samples were studied using conventional time-of-flight (TOF) and interrupted-field time-of-flight (IFTOF) techniques. The samples were placed under a high electric field (5–10 V/ $\mu \text{m}$ ) and exposed to X-ray irradiation, after which TOF and IFTOF measurements were taken to find the hole drift mobility and lifetime after X-ray exposure. There was no observed change in the hole drift mobility but there was a large drop in the hole lifetime. The reduction in the hole lifetime depended only on the total or accumulated dose and the applied field. There was no dependence on the dose rate, over a range of 0.12–2.5 Gy/s, or on the X-ray photon energy, over a range of 50–90 keVp (corresponding to a mean photon energy of 31.9–44.7 keV). The implications of these findings can be seen through the calculation of the charge collection efficiency (CCE). The results show that the effects of X-ray irradiation on a-Se X-ray detectors are considerable when the detector is under an applied field during exposure, but are minimized when the operating field is high (corresponding to a high CCE) and the a-Se is of high-quality electronic grade material.

Recent Developments of Amorphous Selenium-Based X-Ray Detectors: A Review

Amorphous selenium (a-Se) is a photoconductive material that has been intensively investigated from its early application in xerography to its present application in flat panel X-ray imagers. It can be deposited up to a few millimeters thick over a large area. Its high vapor pressure yields uniform coverage in novel device structures for low-cost and large-area applications. The evidence of avalanche multiplication in a-Se and application of a-Se in high-gain avalanche rushing photoconductor video-tubes goes back to the early 1980s. Over the past decade there has been increasing research interest in novel detector structures and integration of a-Se with new materials to leverage the avalanche properties. We summarize some of the shortcomings of a-Se such as low charge carrier mobility, low charge conversion efficiency, depth dependence, and high dark current at high electric fields. We then highlight recent developments in a-Se-based devices to address these shortcomings and enable picosecond timing performance and high detection efficiency.

Dark current–voltage characteristics of vacuum deposited multilayer amorphous selenium-alloy detectors and the effect of x-ray irradiation

Doped and stabilized amorphous selenium (a-Se) alloys in a multilayer form are currently used as a photoconductor in direct conversion flat panel x-ray imagers in mammography and tomosynthesis. While much progress has been made on the physics of such detectors, there are still unresolved questions on such issues as the principles of operation of the so-called p-i-n detector structure in extinguishing the dark current. The present paper examines dark current transients after the application of a voltage in seven types of a-Se alloy based devices: i-layer, i-n, n-i, i-p, p-i, p-i-n, and n-i-p structures. The substrate was ITO coated glass, the top (radiation receiving) electrode was chromium, and the films were fabricated by vacuum deposition. The nominal device thickness was 200 μm, similar to commercial mammographic detectors. It is shown that n-i, i-n, n-i-p, and p-i-n devices have dark currents less than 1 pA mm−2 at an applied field of 10 V/μm. The dark current in the p-i-n device is the lowest at approximately 0.01 pA mm−2 at an applied field of 10 V μm−1. Experiments have been carried out by subjecting the detector to a staircase voltage-time profile during the voltage application (turn-on) and a staircase voltage ramp-down during the turning-off of the bias voltage. Step-voltage ramp-up and step-voltage ramp-down current transient are typical of expected dark current transient behavior in a semiconductor with traps in which carriers are captured and released from various trap centers in the bandgap. The dark current transients are qualitatively similar to those expected from a capacitor in parallel with a large resistor and both in series with a much smaller resistor. Current transients during charging and discharging experiments were integrated to find how much of the injected charge is released during discharge experiments. It is shown that the majority of this trapped charge is stored in the n-type and p-type blocking layers, near the contacts. The trapped carriers in the i-layer represent a very small portion. The evolution of the dark current upon single and repeated x-ray exposure has also been examined in n-i and p-i-n devices. Right after the cessation of irradiation, there is an excess or residual dark current whose magnitude is roughly ∼20 times higher in p-i-n and about ∼2 times higher in the case of n-i under an exposure of 3.36 R and a mean photon energy of 34.2 keV. The absorbed dose is 1.53 Gy. The excess dark current has a fast decay component with a time constant ∼10 s and a slow component with a time constant ∼100 s. It is shown that the decay in the irradiation induced excess dark current is very similar to the initial dark current. There is no permanent change in the dark current, and within a few hundred seconds, the dark current reaches the same level as that in the unexposed detector. The experimental results in this work highlight the distinct advantages of p-i-n and n-i-type a-Se multilayer structures in x-ray detection applications.

Nanocrystalline bismuth oxyiodides thick films for X-ray detector

Materials such as PbI2, HgI2 and PbO are widely used to fabricate flat panel X-ray imaging detector because of high X-ray stopping power (attenuation coefficient). In general, the stopping power (Z4/E3) depends on high atomic number (Z) of the material and energy (E) of the X-ray radiation. In the present study, high atomic numbered bismuth oxyiodides such as BiOI and Bi5O7I nanocrystals were synthesized using a novel process and used in the device fabrication. Thick films of both the samples were coated on the top of patterned metal electrode and interfaced with a source meter to readout the electrical variation for 3.2 s illumination of X-ray using 70 kV real-time dental X-ray imaging machine. The observed result reveals that, the sensitivity increases with the increase of Z value. Also the possibility of utilizing both the nanocrystalline bismuth oxyiodides for the low-dose X-ray detector was explored.

High signal-to-noise ratio HgI2 X-ray detector assisted with ultraviolet radiation

Abstract A direct-conversion active matrix flat panel X-ray imaging detector was fabricated with an HgI2 photoconductor. The HgI2 photoconductive layer was coated on an amorphous Si thin film transistor panel with a particle-in-binder process. The micro-morphological properties of the HgI2 photoconductive layer were characterized by micro-computed tomography, X-ray diffraction, and scanning electron microscopy. The volume density of HgI2 in the layer was 40.9%. The effect of the bias voltage on the sensitivity of the HgI2 photoconductor was investigated with different photon irradiations such as ultraviolet and visible light as one of reset processes. The sensitivity of the HgI2 photoconductor was increased with the help of ultraviolet radiation before X-ray radiation, which released trapped carriers inside the photoconductor and increased the sensitivity of the HgI2 photoconductor. Moreover, ultraviolet irradiation with a DC bias stabilized the sensitivity variation. An X-ray imaging detector in conjunction with anHgI2 photoconductor shows a very high signal-to-noise ratio.

Zero-Dimensional Cs2TeI6 Perovskite: Solution-Processed Thick Films with High X-ray Sensitivity

We demonstrate a potential candidate, the 0D “all-inorganic” perovskite material Cs2TeI6, as a sensitive all-inorganic X-ray photoconductor for the development of the new generation of direct photon-to-current conversion flat-panel X-ray imagers. Cs2TeI6 consists of high atomic number elements, has high electrical resistance, and exhibits high air and moisture stability, making it suitable as a sensitive X-ray photoconductor. In addition, we identify that Cs2TeI6 film can be prepared under a low-temperature process using electrostatic-assisted spray technique under atmospheric conditions and achieved resistivity of 4.2 × 1010 Ω·cm. The resulting air- and water-stable Cs2TeI6 device exhibits a strong photoresponse to X-ray radiation. An electron drift length on the order of 200 μm is estimated under an applied electrical field strength of 400 V·cm–1. A high sensitivity for Cs2TeI6 thick film device is realized, with the value of 192 nC·R–1cm–2 under 40 kVp X-rays at an electrical field of 250 V·cm–1, which...

Pulsed 70 kV X-ray sensing behavior of Cu2HgI4 thick films

X-ray photoconductors are widely used in flat panel X-ray detectors in medical and dental imaging systems. In the present work, X-ray photoconductivity measurement of Cu2HgI4 thick film was performed using a real-time intraoral X-ray machine. To perform the sensing measurement, wet chemical derived Cu2HgI4 sample was coated as a thick film by slurry deposition route on top of the tin coated copper patterned electrode. Prior to the sensing measurement, Cu2HgI4 powder sample was characterized using powder X-ray diffraction, scanning electron microscope, energy dispersive x-ray analysis, Fourier transformed infrared spectroscopy and diffused reflectance spectroscopy. These analysis confirms the sample is in single phase with crystallites are in sub-spherical morphologies. The resistance of Cu2HgI4 thick film was measured under the presence and absence of pulsed 70 kV X-ray for various exposure durations from 0.06 to 3.2 s using a Keithley 2450 source meter. Appreciable sensitivity against intraoral pulsed 70 kV X-ray sensing behavior of Cu2HgI4 thick films explore the possibility of utilizing it as a photoconductor for flat panel X-ray imaging detectors.

A comparative study of scintillator combining methods for flat-panel X-ray image sensors

An X-ray transmission imaging based on scintillation detection method is the most widely used radiation technique particularly in the medical and industrial areas. As the name suggests, scintillation detection uses a scintillator as an intermediate material to convert incoming radiation into visible-light particles. Among different types of scintillators, CsI(Tl) in a columnar configuration is the most popular type used for applications that require an energy less than 150 keV due to its capability in obtaining a high spatial resolution with a reduced light spreading effect. In this study, different methods in combining a scintillator with a light-receiving unit are investigated and their relationships are given in terms of the image quality. Three different methods of combining a scintillator with a light-receiving unit are selected to investigate their performance in X-ray imaging: upward or downward oriented needles structure of CsI(Tl), coating layer deposition around CsI(Tl), and insertion of FOP. A charge-coupled device was chosen to serve as the light-receiving unit for the proposed system. From the result, the difference of needle directions in CsI(Tl) had no significant effects in the X-ray image. In contrast, deposition of the coating material around CsI(Tl) showed 17.3% reduction in the DQE. Insertion of the FOP increased the spatial resolution by 38%, however, it decreased the light yield in the acquired image by 56%. In order to have the maximum scintillation performance in X-ray imaging, not only the reflection material but also the bonding method must be considered when combining the scintillator with the light-receiving unit. In addition, the use of FOP should be carefully decided based on the purpose of X-ray imaging, e.g., image sharpness or SNR.

Dimension dependent immunity of X-ray irradiation on low-temperature polycrystalline-silicon TFTs

Typically, each element in a large-area flat-panel X-ray image sensor consists of a photodetector and amorphous silicon (a-Si) thin-film transistor (TFT) switches. In order to reduce noise, increase sensor dynamic range, and increase carrying capacity, the low-temperature polycrystalline-silicon (LTPS) TFTs have been proposed as a candidate to replace the a-Si TFTs. However, there are concerns regarding the impact of X-ray radiation in LTPS-TFTs, and several studies have been conducted to inquire into the same. In this paper, we show that LTPS TFTs with small channel length (<2 µm) are almost immune to X-ray radiation.

Investigation of time-resolved proton radiography using x-ray flat-panel imaging system

Proton beam therapy benefits from the Bragg peak and delivers highly conformal dose distributions. However, the location of the end-of-range is subject to uncertainties related to the accuracy of the relative proton stopping power estimates and thereby the water-equivalent path length (WEPL) along the beam. To remedy the range uncertainty, an in vivo measurement of the WEPL through the patient, i.e. a proton-range radiograph, is highly desirable. Towards that goal, we have explored a novel method of proton radiography based on the time-resolved dose measured by a flat panel imager (FPI).A 226 MeV pencil beam and a custom-designed range modulator wheel (MW) were used to create a time-varying broad beam. The proton imaging technique used exploits this time dependency by looking at the dose rate at the imager as a function of time. This dose rate function (DRF) has a unique time-varying dose pattern at each depth of penetration. A relatively slow rotation of the MW (0.2 revolutions per second) and a fast image acquisition (30 frames per second, ~33 ms sampling) provided a sufficient temporal resolution for each DRF. Along with the high output of the CsI:Tl scintillator, imaging with pixel binning (2 × 2) generated high signal-to-noise data at a very low radiation dose (~0.1 cGy).Proton radiographs of a head phantom and a Gammex CT calibration phantom were taken with various configurations. The results of the phantom measurements show that the FPI can generate low noise and high spatial resolution proton radiographs. The WEPL values of the CT tissue surrogate inserts show that the measured relative stopping powers are accurate to ~2%. The panel did not show any noticeable radiation damage after the accumulative dose of approximately 3831 cGy. In summary, we have successfully demonstrated a highly practical method of generating proton radiography using an x-ray flat panel imager.