Abstract:Objective To investigate the value of 64-slice and 256-slice spiral CT pulmonary angiography in the diagnosis of pulmonary embolism (PE)in elderly patients. Methods A total of 66 elderly PE patients who received diagnosis from January 2016 to June 2018 were selected and divided into observation group and control group randomly (n=33, each).The observation group was scanned with GE Revolution 256-slice CT, while the control group was scanned with GE-lightspeed 64-slice spiral CT.The dynamic CT values of the main pulmonary artery, the left pulmonary artery, the right pulmonary artery and the pectoralis major muscle were observed.The measured background noise (BN) was the noise value of the main artery.Signal to noise ratio (SNR) and contrast to noise ratio (CNR) were calculated according to the calculation formula.At the same time, the examination time and the dosage of contrast agent were compared. Results There were no significant differences between two groups in the CT value of the main pulmonary artery, the left pulmonary artery, the right pulmonary artery and the pectoralis major muscle, BN, SNR and CNR (n>0.05).Compared with control group, the examination time and contrast agent dosage were fewer in study group [(3.29±1.24)s vs (7.56±1.07)s, (4.77±1.38) mSv vs (5.86±0.94) mSv, P<0.01]. Conclusion Both 64-slice spiral CT and 256-slice spiral CT could diagnose PE well, but 256-slice spiral CT can shorten the examination time and reduce the dosage of contrast agent.