摘要：
Objective To investigate the feasibility of blood oxygen level-dependent magnetic resonance imaging (MRI) in evaluating the response of metastatic lymph nodes of rabbit VX2 tumor to radiotherapy.Methods Twenty-eight healthy New Zealand white rabbits which were provided by the Laboratory Animal Center of Soochow University,male or female,2 to 3 months,weighing 2 to 3 kg,were used to establish the animal model of VX2 tumor popliteal fossa metastatic lymph node,and then were divided into either the radiotherapy group (n=16) or the control group (n=12).The radiotherapy group received a 20 Gy radiotherapy per rabbit,the control group received sham radiotherapy.All rabbits underwent MRI scan on four time points,including before (0 day),3rd,7th and 14th days after radiotherapy.The two parameters of size and R2* value (s-1) of lymph node were measured.At each time point,two rabbits in each group were sacrificed randomly to resect lymph nodes for pathological examination,and two parameters of microvessel density (MVD,strip / HP) and apoptosis index (AI,％) were analyzed.The parameters among the four time points in each group or between the two groups were compared.The correlation of lymph node size and R2* value with MVD or AI was analyzed,respectively.Results A significant size difference was neither between the two groups or among the each time points in each group (P＞0.05).The R2* of lymph node in the radiotherapy group was (29.6±1.7),(36.8±2.6),(44.8±5.8) and (57.7±6.2) s-1 at the time points of 0,3,7 and 14 days,respectively,showing a gradual increase trend;MVD was (52.3±2.5),(41.0±3.6),(34.0±3.6) and (22.7t2.5) strip/HP respectively,showing a decreasing trend;AI was 12.8％±0.5％,14.9％±0.6％,20.6％± 0.5％ and 27.5％±0.7％ respectively,showing a gradual increase trend (all P＜0.05).In the control group,both R2* value and AI among the four time points did not change statistically (all P＞0.05),but MVD showed a gradual increase trend,(50.0 ± 3.0),(53.0 ± 1.7),(60.3 ± 2.5) and (70.0± 2.0) strip/HP,respectively,P＜0.05.There were significant differences in R2* and MVD at 3,7 and 14 days,in AI at 7 and 14 days between the two groups (all P＜0.05).There was a linear correlation of R2* value,but not of size,with MVD and AI (r=-0.87 and 0.94,respectively).Conclusion Blood oxygen level-dependent MRI can indirectly reflect the hypoxic status of metastatic lymph nodes after radiotherapy,and has potential value in evaluating the response of metastatic lymph nodes to radiotherapy.%目的 探讨磁共振(MR)血氧水平依赖(BOLD)成像评估兔VX2瘤转移性淋巴结放疗后反应的可行性.方法 28只健康新西兰大白兔,苏州大学实验动物中心提供[(2018)科第020号],雌雄不限,2～3个月龄,体质量2 ～3 kg,建立VX2瘤胴窝转移性淋巴结模型,分为放疗组(n=16)和对照组(n=12).放疗组接受20 Gy放疗,对照组接受假放疗.所有实验兔于放疗前(0 d)及放疗后3、7、14d(4个时间点)行MRI扫描,测量参数:淋巴结的大小和R2*值(s-1).在各时间点,每组随机处死两只实验兔,取腘窝淋巴结行病理学检查,分析参数:微血管密度(MVD)和凋亡指数(AI).比较两组间,以及组内各时间点间参数的差异,分析淋巴结大小和R2*值分别与MVD及AI的相关性.结果 淋巴结的大小在两组间、组内4个时间点间差异均无统计学意义(均P＞0.05).放疗组淋巴结在0、3、7和14d的R2*值分别为(29.6±1.7)、(36.8±2.6)、(44.8±5.8)和(57.7±6.2)s-1,呈逐渐升高趋势;MVD分别为(52.3±2.5)、(41.0±3.6)、(34.0±3.6)和(22.7±2.5)条/高倍视野,呈逐渐减少趋势;AI分别为12.8％±0.5％、14.9％土0.6％、20.6％±0.5％和27.5％±0.7％,呈逐渐增加趋势(均P＜0.05).对照组淋巴结R2*值和AI在4个时间点间均无明显变化(均P＞0.05),但MVD呈逐渐增加趋势,分别为(50.0±3.0)、(53.0±1.7)、(60.3±2.5)和(70.0±2.0)条/高倍视野,P＜0.05.两组间淋巴结的R2*值和MVD在3、7、14d差异有统计学意义,而AI在7、14d差异均有统计学意义(均P＜0.05).淋巴结R2*值,而不是淋巴结的大小,分别与MVD及AI有显著相关性(r分别为-0.87和0.94).结论 MR血氧水平依赖成像间接反映放射性治疗后转移性淋巴结内部乏氧状态,具有潜在的评价放射性治疗反应的价值.
