一体化PET-MR设备中飞行时间技术和点扩展函数技术对PET图像质量的影响

The effects of TOF and PSF on image quality of PET in integrated PET-MR

目的:研究在一体化PET-MR图像重建中飞行时间(TOF)技术和点扩展函数(PSF)对PET图像质量的影响。方法:依据美国电气制造商协会(NEMA)NU2-2007标准,使用国际电工委员会(IEC)61675-1标准规定的PET图像质量体模,在通用电气公司GE SIGNA型PET-MR及配套AW4.6工作站上完成扫描和图像重建,采用联合使用(TOF+PSF)、单独使用PSF技术(non-TOF+PSF)、单独使用TOF技术(TOF+non-PSF)和两种技术均不使用(non-TOF+non-PSF)4种方法重建PET图像,分析图像的对比度(Q_H和Q_C)、背景变化率(N_j)和信噪比(SNR)。结果:以non-TOF+non-PSF重建结果为参照,单独使用PSF技术、单独使用TOF技术和联合使用TOF+PSF技术重建图像的平均热区对比度(Q_H)分别提高了7.61%、20.94%和40.17%;单独使用TOF技术的图像平均冷区对比度(Q_C)提高了11.29%,联合使用TOF+PSF技术的图像Q_C提高了12.32%;单独使用PSF技术、单独使用TOF技术和联合使用TOF+PSF技术重建图像的平均背景变化率(N_(mean))分别降低了2.28%、21.44%和30.03%;SNR则分别提高了11.52%、44.28%和92.70%。结论:TOF和PSF技术均可提高PET的图像质量,联合使用两种技术对提高重建图像质量效果更为明显。

Objective To research the effects of time of flight （TOF） technique and point spread function （PSF） algorithms on the image quality of PET in the image reconstruction of integrated PET-MR. Methods： The NU 2-2007 protocol of NEMA was followed. The image quality phantom following IEC Standard 61675-1 was adopted in the research. All scan and image reconstruction were performed on PET/MR and matched AW4.6 workstation of GE SIGNA. Different algorithms （TOF＋PSF, TOF＋non-PSF, non-TOF＋PSF, and non-TOF＋non-PSF） were applied in image reconstruction of PET. The obtained PET images were quantitatively evaluated and analyzed by following parameters： contrast recovery of hot and cold spheres （QH and QC）, background variability （Nj） and the signal-to-noise ratio （SNR） of hot spheres. Results： For quantitative image quality evaluation, results of （non-TOF＋non-PSF） were used as reference. The average QH of （non-TOF＋PSF）, （TOF＋non-PSF） and （TOF＋PSF） were increased 7.61%, 20.94% and 40.17%, respectively. The average QC of TOF alone and （TOF＋PSF） were increased 11.29% and 12.32%, respectively. The average Nmean of PSF alone, TOF alone and （TOF＋PSF） were decreased 2.28%, 21.44% and 30.03%, respectively. And the SNR of PSF alone, TOF alone and （TOF＋PSF） were increased 11.52%, 44.28% and 92.70%, respectively. Conclusion： Both TOF and PSF can improve the overall image quality of PET, and it is more obvious when they are used in combination.