经皮冷冻猪肺的影像学和病理学研究

Imaging and Pathological Features of Percutaneous Cryosurgery on Normal Lung Evaluated in a Porcine Model

背景与目的肺癌已成为最常见死因的恶性肿瘤之一,对不能手术切除的肺癌,冷冻是一种安全可选择的消融治疗手段,但肺为含气组织,与冷冻肝脏、胰腺等实体器官不同,在理论上冷冻范围很难超过肿瘤边缘。本研究旨在通过正常猪肺模型实验了解不同冷冻-复温循环对肺部组织坏死范围的影响并探讨经皮冷冻肺治疗的技术方案。方法采用6只平均体重为23kg的正常西藏小型猪作为模型,在CT引导下选择猪肺上叶1点和下叶2点作为靶点,使用直径为1.7mm的冷冻探针分别插入肺叶各靶点做经皮穿刺冷冻。左肺行冷冻10min、复温5min共2个周期的冷冻-复温循环;右肺先行冷冻5min、复温5min的2个冷冻-复温循环,然后行冷冻10min、复温5min的第3个冷冻-复温循环。左右肺的实验条件和实验方法均相同。实验中,观察CT影像下冰球的形态学变化。分别取冷冻后4h、3d和7d的猪肺标本,观察其大体形态及其在光镜下的组织学变化。结果猪肺冷冻过程中随着时间的延长和循环次数的增加,冰球逐渐增大;无论2个或3个冷冻-复温循环,所产生的冷冻范围("假定坏死区")在大体标本上均超过CT上冷冻过程中显示的冰球大小;冷冻后随着时间延长,组织学坏死区逐步增大,3天及以后,假定坏死区即为组织学坏死区。结论经皮冷冻肺可以达到有效破坏靶组织的目的;在技术上,肺冷冻以3个冷冻-复温循环为佳;冷冻范围不强求冷冻"1cm安全边缘"。上述研究结果对于简化冷冻治疗过程及减少并发症具有临床价值。

Background and objective Lung cancer is one of the most commonly occurring malignancies and fre-quent causes of death in the world. Cryoablation is a safe and alternative treatment for unresectable lung cancer. Due to the lung being gas-containing organ and different from solid organs such as liver and pancreas, it is difficult to achieve the freezing range of beyond the tumor edge 1 cm safety border. The aim of this study is to examine the effect of different numbers of freeze cycles on the effectiveness of cryoablation on normal lung tissue and to create an operation guideline that gives the best effect. Methods Six healthy Tibetan miniature pigs were given a CT scan and histological investigation after percutaneous cryosurgery. Cryoablation was performed as 2 cycles of 10 min of active freezing in the left lung; each freeze followed by a 5 min thaw. In the right lung, we performed the same 2 cycles of 5 min of freezing followed by 5 min of thawing. However, for the right lung, we included a third cycle of consisting of 10 min of freezing followed by 5 min of thawing. Three cryoprobes were inserted into the left lung and three cryoprobes in the right lung per animal, one in the upper and two in the lower lobe, so as to be well away from each other. Comparison under the same experimental condition was necessary. During the experiment, observations were made regard-ing the imaging change of ice-ball. The lungs were removed postoperatively at 3 intervals： 4 h, 3 d of postoperation and 7 d of postoperation, respectively, to view microscopic and pathological change. Results The ice-ball grew gradually in relation to the increase in time, and the increase in number of cycles. The size of the cryolesion （hypothesis necrotic area） in specimens, over time, became larger in size than the size of the ice-ball during operation, regardless of whether 2 or 3 freeze-thaw cycles were performed. The area of necrosis was gradually increased over the course of time. The hypothesis necrotic area was equal to necrosis area 3 d after cryosurgery. Conclusion Percutaneous cryoablation of the lung can achieve complete ablation of target tissue. The freezing technique may be different depending on the individual circumstances of each tumor. In technology, 3 freeze-thaw cycles are recommended, and the range of cryoablation’s effective diameter may be not necessarily beyond the tumor edge at least 1 cm safe border during cryosurgery.