中文摘要：

目的 研究CT多次扫描对小鼠外周血淋巴细胞和骨髓细胞的影响,探索CT扫描对机体的损伤效应机制.方法 BALB/c小鼠60只,按随机数字表法,分为对照组、1、2、4、6和8次CT扫描组共6组,每组10只.对照组不扫描,扫描组用64排螺旋CT以骨盆模式对小鼠进行全身扫描,采用热释光技术检测小鼠局部吸收剂量.采用流式细胞术,在照后lh检测小鼠外周血淋巴细胞和骨髓细胞DNA损伤形成的γ-H2AX焦点,在照后24 h检测细胞凋亡、自噬、细胞周期和外周血CD4＋、CD8＋水平变化.结果 6组小鼠相应的辐射剂量分别约为0、63.09、124.14、174.48、232.99和504.72 mGy.扫描2次以上的小鼠外周血淋巴细胞和扫描4次以上的骨髓细胞中,y-H2AX均显著增加（P＜0.05）,4次以上扫描使外周血淋巴细胞凋亡增加（P＜0.05）,但使骨髓细胞凋亡降低（P＜0.05）,体现出淋巴细胞更为敏感而骨髓细胞成分复杂且具有不同的辐射敏感性及反应时相性.CT扫描对外周血淋巴细胞自噬水平无影响,但单次扫描使骨髓细胞自噬增加（F=81.104,P＜0.05）.扫描8次后骨髓细胞Go/G1期和G2/M百分率增加（x2 =11.29、28.57,P＜0.05）.外周血CD4＋、CD8＋细胞亚群百分率在CT扫描后下降（P＜0.05）,但CD4 ＋/CD8＋比值未见明显变化.结论 CT多次扫描对造血系统和免疫系统产生了损伤效应,机体进而启动凋亡、自噬和细胞周期阻滞来维持基因组稳定性,而机体的免疫平衡未受影响.

英文摘要：

Objective To investigate the effects of repeated computed tomography （CT） scan on hematological and immunological index in mice, and to explore the related mechanism. Methods A total of 60 BALB/e mice were randomly divided into six groups as control, once, twice, 4,6 and 8 times of CT scans, and administered with whole-body scan by 64-slice spiral CT with the pelvis scan mode. Thermoluminescencc dosimeter was used to detect the absorbed doses of CT scan, while DNA damage （＇y- H2AX） , apoptosis,autophagy,cell cycle and percentages of CD4/CD8 in peripheral lymphocytes and bone marrow cells were analyzed by flow eytometry. ~-H2AX was detected 1 h after the last CT scan, and the other indexes were detected 24 h after the last CT scan. Results ~-H2AX increased after more than twice CT scans in peripheral lymphoeytes and after than 4 times of CT scan in bone marrow cells （ P 〈 0. 05 ）. Apoptosis increased in peripheral blood lymphoeytes and decreased in bone marrow cells after more than 4 times of CT scan （ P 〈 0.05 ） , suggesting that lymphocytes were more sensitive while different cell subpopulation in bone marrow showed different sensitivity and response phase. No obvious changes of autophagy level were observed in peripheral blood lymphocytes,while autophagy increased in bone marrow cells after single CT scan （F = 81. 10, P 〈 0.05）. 8 times of CT scan significantly increased the percentages of cells at Go/Gt phase and G2/M phase（ X2 = 11.29, 28.57, P 〈 0. 05 ）. The percentage of CD4 ＋ T, CD8 ＋ T cells decreased after CT scan, but no effects on the ratio of CD4 ＋/CD8 ＋. Conclusions Repeated CT scans could induce injury effects on hematopoietic system and immune system, and then the apoptosis. Apoptosis, autophagy and cell cycle arrest might be initiated to maintain genome stability but there is no influence on immune balance.