Abstract
The aim of this study is to assess direct X-ray detectors based on organic thin films, fabricated onto flexible plastic substrates and operating at ultra-low bias (<1 V), for different medical applications. With this purpose, flexible fully organic pixelated X-ray detectors have been tested at the imaging beamline SYRMEP (SYnchrotron Radiation for MEdical Physics) at the Italian synchrotron Elettra, Trieste. The detectors’ performance has been assessed for potential employment both as reliable wearable personal dosimeters for patients and as flexible X-ray medical imaging systems. A spatial resolution of 1.4 lp mm-1 with a contrast of 0.37 has been evaluated. Finally, we validate the detector using X-ray doses and energies typically employed for actual medical radiography, and using X-ray beam pulses provided by a commercial dental radiography system, recording a sensitivity of 1.6×105 µC Gy-1 cm-3 with a linear response with increasing of the dose rates and a reliable signal to 100 ms X-rays pulses.
Highlights
Nowadays, the employment of ionizing radiation sources (X- and gamma-rays, protons, electrons) for medical diagnostic, monitoring, and therapy is widespread and is continuously expanding
We demonstrate the potentiality of such full-organic flexible detectors as medical diagnostic and dosimetry tools, giving the proof of principle for their application as X-ray imagers with a linear response at low dose rates and the ability to follow Xrays pulses of 100 ms
Gold has been employed as electrodes material since it forms ohmic contacts with TIPS-pentacene, i.e., ensuring an efficient injection/collection of charges to/from the organic semiconductor, being the work function of gold φAu = (5.31÷5.37) eV [37] generally considered matching to HOMO (Highest Occupied Molecular Orbital) level of TIPSpentacene [38]
Summary
The employment of ionizing radiation sources (X- and gamma-rays, protons, electrons) for medical diagnostic, monitoring, and therapy is widespread and is continuously expanding. Most of the solid-state detectors employed for dosimetry cannot be considered tissue-equivalent due to their composition with heavy elements and their consequent high X-ray absorbing power, causing limited reliable calibration issues. Concerning commercial imaging flat panels, typically based on a-Si, a-Se, or poly-CZT, they are heavy, bulky, difficult to grow in large pixelated matrices with limited costs and by means of easy and lowtemperature fabrication techniques and maintain the stiff mechanical properties of the materials employed in medical dosimetry. In this framework, organic semiconductors, i.e., organic small
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