17例恶性肿瘤18氟脱氧葡萄糖PET显像假阴性的分析

目的 探讨恶性肿瘤^18氟脱氧葡萄糖（^18F—FDG）PET假阴性患者的FDG摄取特点、影响因素,分析PET／CT检查中CT对其的辅助诊断价值。方法 收集行PET／CT检查者中,^18F-FDGPET为阴性的17例恶性肿瘤患者,对其PET图像进行视觉观察和半定量分析,并与CT及病理检查结果进行对比分析。结果 6例肝癌患者病理证实为高分化型肝细胞肝癌,其中1例有两处病灶,一处病灶FDG摄取、平扫CT密度较周围正常肝组织低下,另一处病灶FDG摄取、平扫CT均为阴性;后行增强CT显示在动脉期两处病灶均明显强化。1例胃印戒细胞癌伴右侧附件转移患者,1例腹壁、大网膜转移性腺癌患者,3例肾透明细胞癌患者和1例前列腺癌患者（高分化型）的^18F—FDGPET诊断受消化道正常生理性FDG摄取或泌尿系统FDG滞留的影响。3例转移癌病变直径≤1cm,其中2例的原发病灶FDG摄取明显增高,1例原发病灶^18F—FDGPET及CT诊断为阴性。68．8％原发肿瘤、66．7％转移肿瘤在平扫CT上显示异常密度,并精确定位;而31．2％原发肿瘤、33．3％转移肿瘤病变^18 F—FDGPET及CT诊断均为阴性。结论恶性肿瘤^18F—FDGPET假阴性与病理学类型、分化程度及病灶大小有关;结合CT或重视PET显像方法可减少恶性肿瘤^18F—FDGPET假阴性。

Malignant tumor with false negative 18F-FDG PET image

Objective To investigate the FDG uptake characteristics, the factors affecting 18F-FDG uptake and the extra CT diagnostic value of 18F-FDG PET/CT scan in the malignant tumor with false negative 18F-FDG PET image. Methods The data of PET/CT image in 17 patients with various kinds of cancers were reviewed and analyzed by visual observation and semi-quantity analysis ( SUV). The results were compared with the CT and histopathological diagnosis, respectively. Results Of 6 well-differentiated HCC patients confirmed by histopathological diagnosis, one had two lesions in the right lobe of the liver. One of these two lesions showed low FDG uptake on 18F-FDG PET scan and low density on CT scan. The other one was not shown on either 18F-FDG PET or plain CT scan. But on enhanced CT scan, these two lesions were found to be inhomogeneous with high density at arterial phase. The false negative 18F-FDG PET images of one gastric signet ring cell carcinoma in the gastric fundus with right adnexa metastasis, 3 renal cell carcinoma, one greater omentum and peritoneal metastatic adenocarcinoma and one well-differentiated prostate cancer were caused by normal physical uptake in the digestive tract or FDG retention in the urinary system due to normal excretion. The size of three metastases was smaller than or equal to 1 cm in diameter, however, two primary lesions of these metastases showed high FDG uptake and only one was negative on either 18F-FDG PET or CT scan. In this series, 68. 8% of the primary tumors and 66. 7% of metastases were found to show abnormal density on CT scan, and 31. 2% of the primary tumors and 33. 3% of metastases were not detectable on either PET or CT images. Conclusion False negative 18F-FDG PET in malignant tumor may be correlated with the pathologic type, differentiation degree and the lesion size. Combining CT information with PET or paying attention to the scan methods during 18F-FDG PET examination may reduce the rate of false negative 18F-FDG PET diagnosis in various kinds of malignant tumors.