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目的 探讨高时间分辨率宽体探测器CT行冠脉CT血管造影(CCTA)时采用自由呼吸扫描对辐射剂量的影响.方法 前瞻性研究,将首都医科大学附属北京友谊医院104例行冠脉CTA扫描的患者随机分为两组,A组(n=51)行自由呼吸冠脉CTA,B组(n=53)行屏息的冠脉CTA,记录并对比两组患者的初始心率、测试心率以及扫描辐射剂量.结果 A组患者的初始心率(66.85±9.22 bpm)与测试心率(66.31±8.59 bpm)无显著差异(P>0.05),其中测试心率与初始心率之差>3 bpm的2例,占4％;B组患者的初始心率(65.47±7.76 bpm)与测试心率(64.41±8.63 bpm)存在显著差异(P3 bpm的22例,占B组人数的42％.两组患者辐射剂量(DLP)分别为A组123.44(107.5～190.04)mGyocm和B组107.80(80.32～189.12)mGyocm,A组剂量大于B组(P75 bpm的A组患者DLP为120.21(115.74～132.47)mGyocm,B组132.04(122.42～197.51)mGyocm,A组DLP小于B组(P<0.05);初始HR≤75 bpm的A组患者100.12(98.21～198.07)mGyocm,B组患者97.01(78.97～159.41)mGyocm,A组DLP大于B组(P 0. 05). In 2 cases (4％ in group A)the difference between initial and test HR was greater than 3 bpm. In group B,the difference between initial and test HR was significant (65. 47 ± 7. 76 bpm vs. 64. 41 ± 8. 63 bpm,P < 0. 05)and HR of 22 patients (41. 5％)varied greater than 3 bpm in breath - holding. The DLP of group A and B were 123. 44 (107. 5 ～ 190. 04)mGyocm and 132. 04(122. 42 ～ 197. 51)mGyocm respectively (P 75 bpm)had lower DLP in group A 120. 21 (115. 74 ～ 132. 47)mGyocm than in group B 132. 04 (122. 42 ～ 197. 51)mGyocm,P < 0. 05. Meanwhile,the patients with meandian and low initial HR (≤75 bpm)had higher DLP in group A 100. 12 (98. 21 ～ 198. 07)mGyocm than in group B 97. 01(78. 97 ～ 159. 41) mGyocm,P < 0. 05. Conclusion The radiation dose of free - breathing CCTA performed with high - temporal resolution wide detector CT may vary from traditional breath - holding CCTA. Patient with high heart rate may receive lower radiation dose in free - breathing CCTA while patient with medium or low heart rate may recieve higher radiation dose.