ABSTRACT
A series of Sr3 (PO4)2: Eu²âº blue phosphors were synthesized by high temperature solid state method under N2-H2 reducing atmosphere. The crystal structures, excitation and emission spectra were characterized by X-ray diffraction (XRD) and Photoluminescence (PL), respectively. The results show that the Sr3 (PO4)2: Eu²âº phosphor can be efficiently excited by the wavelengths ranging from 310 to 390 nm, and the excitation peak wavelength locates at 359 nm. A wide emission spectrum (~150 nm, originating from the 4ƒ 5d¹-->4ƒ of the Eu²âº) with a peaking wavelength of 438 nm was obtained. Through the Gaussian fitting, we found that the emission band formed by two luminescence centers(430 and 459 nm), which indicated that the Eu²âº occupied two different Sr²âº sites in the substrate of Sr3(PO4)2. As the Eu²âº doping concentration is 7%, the maximum luminous intensity was obtained. With the increasing of the doping concentration of the Eu²âº, the concentration quenching effect occurred, and the emission peak wavelength has a red shift. The PL intensity of the Sr3 (PO4)2: Eu²âº phosphor is about 1.3 times than that of the blue emitting phosphor BaMgAl10O17: Eu²âº (BAM) which means that it is a promising candidate for the blue phosphor material for white LED.
ABSTRACT
Exponential apparent diffusion coefficient (EADC) is an indicator of diffusion-weighted imaging (DWI) and reflects the pathological changes of tissues quantitatively. However, no study has been investigated in the space-occupying kidney disease using EADC values. This study aims to evaluate the diagnostic role of EADC values at a high magnetic field strength (3.0 T) in kidney neoplastic lesions, compared with that of the ADC values. Ninety patients with suspected renal tumors (including 101 suspected renal lesions) and 20 healthy volunteers were performed MRI scanning. Diffusion-weighted imaging was performed with a single-shot spin-echo echo-planar imaging (SE-EPI) sequence at a diffusion gradient of b = 500 s/mm2. We found renal cell carcinoma (RCC) can be distinguished from angiomyolipoma, and clear cell carcinoma can be distinguished from non-clear cell carcinoma by EADC value. There was significant difference in overall EADC values between renal cell carcinoma (0.150 ± 0.059) and angiomyolipoma (0.270 ± 0.108) when b value was 500 s/mm2. When receiver operating characteristic (ROC) was higher than 0.192, the sensitivity and specificity of EADC value of renal cell carcinoma were 84.6 and 81.1 %, respectively. In conclusion, EADC map shows the internal structure of the kidney tumor more intuitively than the ADC map dose, and is also in line with the observation habits of the clinicians. EADC can be used as an effective imaging method for tumor diagnosis.
