脑肿瘤的对比剂增强  

Contrast Enhancement of Brain Tumors

作　　者：张云亭[1] 张敬[2] 

机构地区：[1]天津医科大学总医院放射科,300052 [2]天津市影像医学研究所

出　　处：《中国医学计算机成像杂志》2000年第4期263-268,共6页Chinese Computed Medical Imaging

摘　　要：脑肿瘤CT、MRI强化的机制相同 ,均由肿瘤破坏了血脑屏障 ,使对比剂从血管内渗透到肿瘤组织的细胞外间隙引起 ,此外 ,肿瘤血管内的对比剂也会产生一定的强化。增强MRI在很多方面优于增强CT ,因此在脑肿瘤的检查中增强MRI已大量取代了增强CT检查。MRI对比剂的常规剂量为0.1mmol/kg,使用0.3mmol/kg的大剂量不但可以提高脑内转移瘤的检出率 ,还能更准确地显示胶质瘤的范围 ;对垂体微腺瘤来说0.05mmol/kg对比剂的强化效果等于甚至优于0.1mmol/kg。关于增强MRI的时间选择问题 ,各研究结果不尽相同 ,一般认为注射对比剂后2～5min各种肿瘤都会明显强化 ,随时间延长肿瘤强化程度轻度增加 ,强化持续20min左右。使用磁化转移技术可提高脑肿瘤与正常脑组织的影像对比 ,并可检出更多的转移瘤病灶 ,肿瘤强化效果类似于使用大剂量对比剂。超顺磁性微粒氧化铁和MRI靶特异性对比剂已用于脑肿瘤的增强MRI临床和动物试验研究 ,其应用前景很广阔。对比剂增强在评价脑肿瘤中的价值包括 :(1)增强可使肿瘤病灶更加清楚 ;(2)根据胶质瘤强化程度可以粗略估计其侵袭性 ;(3)增强检查有助于在影像引导下对肿瘤进行活检 ;(4)On both CT and MR imaging the mechanism of enhancement is same.The destruction of blood-brain barrier by brain tumors permits passege of contrast agent into extracellular spaces of tumors.In addition,contrast agent inside tumor vessles may also contribute to enhancement.The enhanced MRI is superior to enhanced CT in several aspect,and hence enhanced CT has been replaced by enhanced MRI in many studies. The accepted standard dose of MRI contrast agent is 0.1 mmol/kg.Use of so-called high dose(0.3mmol/kg)not only can improve the detection of brain metastases but also can accurately delineate the extent of gliomas.For pituitary adenomas,0.05mmol/kg contrast agent may have a fetter or equal result to the standard dose.There is no agreement about the question of time selection of enhanced MR scan.In general,it is accepted that scanning should not begin until 2～5 minutes after injection of contrast media.The degree of enhancement of brain tumors may increase slightly in delayed post-contrast imaging,and the enhancement may last about 20 minutes.Magnetization transfer(MT) technique can improve the imaging contrast of brain tumors to normal brain tissues,and also can increase the number of metastatic lesions showed.The improvement achieved by MT in imaging of brain tumors is analogous to the improvement gained with high-dose contrast enhancement.Superparamagnetic ultra-small-particulate iron oxide and MRI targeted contrast agent are both available in research of brain tumors.Although they have good prospect,at present they are still in the stage of animal and clinical trials.The benefits of contrast enhacement MRI to the diagnosis of brain tumor are.(1)to improve the visual conspicuity of brain tumors; (2)to provide a rough guide about the aggressiveness of gliomas;(3)to benefit image-guided biopsy;(4)to delineate the extent of the brain tumors more accurately.

关 键 词：脑肿瘤 CT MRI 脑肿瘤 对比剂 

分 类 号：R739.4[医药卫生—肿瘤]