High performance microstructured Lu_2O_3: Eu thin film scintillator for X-ray computed tomography

摘要

Large penetration depth and weak interaction of high energy X-rays in living organisms provide a non-destructive way to study entire volumes of organs without the need for sophisticated preparation (injection of contrast material, radiotracer labels etc.). X-ray computed tomography (CT) is a powerful diagnostic tool allowing 3D image reconstruction of the complete structure. Using hard X-rays in medical imaging leads to reduced dose received by the patient. At higher energies, however, the conventional scintillators quickly become the limiting factor. They must be thin in order to provide reasonable spatial resolution and preserve image quality. Nevertheless, insufficient thickness introduces the need for long acquisition times due to low stopping power. To address these issues, we synthesized a new structured scintillator to be integrated into CCD- or photodiode-based CT systems. Europium-doped Lu_2O_3 (Lu_2O_3:Eu) has the highest density among all known scintillators, very high absorption coefficient for X-rays and a bright red emission matching well to the quantum efficiency of the underlying CCD- and photodiode arrays. When coupled to a suitable detector, this microcolumnar scintillator significantly improves the overall detective quantum efficiency of the detector. For the first time ever, structured and scintillating film of Lu_2O_3:Eu was grown by electron-beam physical vapor deposition. A prototype sensor was produced and evaluated using both laboratory X-ray sources as well as synchrotron radiation. Comparative performance evaluations of the newly developed sensor versus commercial grade scintillators were conducted. Such synthesis of high density, micro-structured, scintillating coatings enables the development of high sensitivity X-ray detectors for CT applications.