兔肝VX2瘤不同生长时期的3.0T MR WB-DWI、PET/CT成像与病理的对照研究

Rabbit Liver VX2 Tumors in Different Growth Period on3. 0 T MR WB DWI and PET /CT: Comparison Study with Pathology

目的比较3.0 T MR全身扩散加权成像(WB-DWI)与正电子发射计算机断层显像(PET)/CT成像在兔肝VX2瘤的诊断及淋巴结转移、远处转移评估中的价值与限度,探寻一种更为经济、实用的肝癌影像诊断、鉴别诊断与临床分期的影像检查方法。方法采用开腹直视下瘤块接种法,将成功建模的16只实验兔随机分为3组(14天组6只、28天组6只、42天组4只)。在对应的时间内,采用Philips 3.0 T-Achieva/Intera双梯度超导高场强MR扫描仪及Philips 16 TOF PET/CT扫描仪行MR WB-DWI及PET/CT检查。检查结束后处死实验兔进行尸检,比较两种成像方法对肝内原发病灶及远处转移灶的检出情况。结果 14天组直径在5 mm左右的兔肝VX2瘤PET/CT不能检出,在WB-DWI上不易辨认,其诊断需结合DWI横断图像。28天组和42天组直径>1.0 cm的兔肝VX2瘤WB-DWI、PET/CT两种检查方法均能检出;在转移灶的检出方面,PET仅能发现直径>1.0 cm的转移灶,而WB-DWI则能检出PET不能发现的肝内、肺内直径<1.0 cm的小转移灶,对纵隔、腹腔、腹膜后淋巴结的检出率也明显高于PET。结论 PET/CT受其空间分辨率等因素的限制,对直径<1.0 cm的VX2瘤及转移灶检出率低,存在假阴性结果;3.0 T MR WB-DWI与PET/CT相比,具有无需注射对比剂、无电离辐射、价格低廉等优势,且对小转移灶及淋巴结的显示敏感性更高,具有极大的临床价值与广阔的应用前景,可作为肿瘤全身筛查方法的一种补充。

Objective To assess the value and limit of 3.0 T MR whole body diffusion weighted imaging （WB-DWI） and PET/CT imaging in diagnosis of rabbit liver VX2 tumors, lymph node metastasis and distant metastasis. Therefore to explore a more economic and practical imaging method for liver cancinoma diagnosis, differential diagnosis and clinical staging. Methods VX2 tumors were implanted into liver after laparotomy. Sixteen successful modeling rabbits were ran- domly divided into three groups （ six in fourteen days group, six in twenty-eight days group and four in forty-two days group）. In the corresponding period, use Philips 3.0 T-Achieva/intera dual gradient superconducting high field strength MR scanner and Philips 16 TOF PET/CT scanner for MR WB-DWI and PET/CT scanning. At the end of all examinations, the rabbits were killed for autopsy. The detection rates of primary liver lesion and distant metastasis were compared between two imaging methods. Results VX2 tumors in fourteen days group with diameter about 5mm, could not be detected by PET/ CT, neither by WB-DWI, the diagnosis must be combined with MR DWI cross-sectional images. VX2 tumors in twenty- eight days and forty-two days group with diameter greater than 1.0cm, could be detected by both WB-DWI and PET/CT. In the detection of metastases, PET could detect the metastases with diameter greater than 1.0cm in liver, WB-DWI could de- tect the metastases in liver and lung with diameter less than 1.0cm, the detection rates of mediastinum, abdominal, retro- peritoneal lymph nodes were significantly higher than PET. Conclusion The spatial resolution limits PET/CTto detect le- sions with diameter less than 1.0cm. Compared with PET/CT, 3.0T MR WB-DWI has the advantages of no contrast agentinjection, no ionizing radiation and lower cost, has higher sensitivity in small metastases and lymph nodes detecting, has great clinical value and broad application prospects, which can be used as a complement of tumor body screening method.