Computer-aided maxillofacial radiographic diagnosis: impact of variations in scintillator and acquisition mode

Preparation and scintillating properties of Sol-Gel Eu(3+), TB(3+) co-doped Lu(2)O(3) nanopowders

Nanocrystalline Eu³⁺, Tb³⁺ co-doped Lu₂O₃ powders with a maximum size of 25.5 nm were prepared by the sol-gel process, using lutetium, europium and terbium nitrates as precursors, and ethanol as a solvent. Differential thermal analysis (DTA) and infrared spectroscopy (IR) were used to study the chemical changes during the xerogel annealing. After the sol evaporation at 100 °C, the formed gel was annealed from 300 to 900 °C for 30 min under a rich O₂ atmosphere, and the yielded product was analyzed by X-ray diffraction (XRD) to characterize the microstructural behavior and confirm the crystalline structure. The results showed that Lu₂O₃ nanopowders start to crystallize at 400 °C and that the crystallite size increases along with the annealing temperature. A transmission electron microscopy (TEM) study of samples annealed at 700 and 900 °C was carried out in order to analyze the microstructure, as well as the size, of crystallites. Finally, in regard to scintillating properties, Eu³⁺ dopant (5 mol%), Tb³⁺ codoped Lu₂O₃ exhibited a typical red emission at 611 nm (D_°→⁷F₂), furthermore, the effect of Tb³⁺ molar content (0.01, 0.015 and 0.02% mol) on the Eu³⁺ radioluminiscence was analyzed and it was found that the higher emission intensity corresponds to the lower Tb³⁺ content.

Effects of scintillator on the detective quantum efficiency (DQE) of a digital imaging system

OBJECTIVE

To compare the effects of scintillator on the detective quantum efficiency (DQE) of a charge-coupled device (CCD) digital intraoral radiographic system.

STUDY DESIGN

Three screens composed of 3 different scintillator materials, namely europium-doped lutetium oxide (Lu2(O3):Eu3+), transparent optical ceramic (TOC), thallium-doped cesium iodide (CsI:Tl; CsI), and terbium-doped gadolinium oxysulfide (Gd2(O2)S:Tb; GOS) were compared, in turn, in combination with a CCD detector having square pixels with height and width dimensions of 19.5 microm. DQE was investigated using the slanted-slit-derived MTF and surrogate signal-to-noise ratio (SNR) measurements derived from calculations of the mean and standard deviations from the mean pixel values of multiple random patches from various uniform exposures. An Irix x-ray generator operated at 70 kVp and 8 mA, with a nominal focal spot size of 0.7 mm and 2.5 mm Al equivalent filtration, was used in making all exposures.

RESULTS

Using TOC, the peak DQE was 62% at 5 cycles/mm. For CsI, the peak DQE was 22% at 2 cycles/mm. With GOS, the peak DQE was 10% at 1 cycle/mm.

CONCLUSION

Under identical experimental settings, TOC consistently resulted in higher DQE than CsI and commercially available GOS scintillators combined with the same high-resolution solid-state detector.