RESUMO
Objective: To explore the impacts of different reconstruction combinations on image quality of different sized lesions, so as to propose the optimal reconstruction scheme for smaller lesions on integrated PET/MR. Methods: SIGNA TOF PET/MR system was used for scanning of PET image quality (IQ) emission phantom designed taken standards of the International Electrotechnical Commission (IEC) recommendations. Then the list mode raw data of PET were reconstructed using time of flight(TOF)-ordered subsets expectation maximization(OSEM)under different conditions, including the maximum expected value of the ordered subset (the iterative subset: 28, the number of iterations: 1-9 times),the reconstruction matrix (128×128, 192×192, 256×256), Gaussian low-pass filter full width at half maximum (FWHM) (1-6 mm), time-of-flight (TOF) technology alone (TOF+NOTOF), separate point spread function (PSF) (PSF+NOPSF), both TOF and PSF (TOF+PSF), as well as neither TOF nor PSF (NOTOF+NOPSF). Imaging quality was assessed under different reconstruction conditions using parameters including contrast recovery (CR), background variability (BV) and signal-to-noise ratio (SNR). Results: Balls with 10 and 13 mm diameters simulating small lesions in the OSEM (3 iterations, 28 subsets), 192×192 matrix, 2 mm Gaussian low-pass filter full width at half maximum and TOF+PSF reconstruction combination achieved the highest SNR, which was 13.31% and 21.73%, 13.31% and 21.73%, 25.74% and 35.8% as well as 26.25% and 46.01%, respectively. Conclusion: Using reconstruction combination as 3 iterations, 28 subsets, 192×192 matrix and TOF+PSF, the best image quality of small lesions can be obtained under the above mentioned conditions.
RESUMO
This article introduces the progress about study of lipid mdeiating action of chitosan. It was found that chitosan could mediate blood lipids and modification of chitosan could improve its lipid mediating activity in animal and human.