【作者】 钱银锋；

【导师】 漆剑频；

【作者基本信息】 华中科技大学 ， 影像医学与核医学， 2008， 博士

【摘要】 目的:通过自旋回波序列T1WI(T1WSE)与翻转恢复序列T1WI(T1WIR)的比较研究,探讨中枢神经系统疾病MR T1WI成像时的序列选择。方法:取Gd-DTPA加入蒸馏水中,配制0.025mmol/L至5mmol/L的对比剂溶液,进行T1WIR和T1WSE扫描,计算对比剂溶液的增强率(CER)及其与白质、与灰质的对比度(CR)。将对比剂溶液从0.025mmol/L开始倍比稀释至0.000024mmol/L,与蒸馏水进行对照分析,确定T1WIR和T1WSE上可显示强化的最低对比剂浓度。行MRI头颅检查的患者196例分为4组:①原发性脑肿瘤组,92例;②脑转移瘤组,31例;③脑膜炎组,24例;④其它疾病,49例。所有患者均行轴位T1WIR和T1WSE检查,①～③组病例及第④组中24例行单倍剂量Gd-DTPA增强检查,轴位T1WIR和T1WSE依次作为增强后第一序列。测量每例T1WIR和T1WSE图像上灰、白质和脑脊液的信号强度,及背景噪声信号强度的标准差(SD),测量肿瘤增强前后的信号强度及肿瘤体积,计算增强前后病灶的信噪比(SNR)、灰质与白质的CR、灰质与白质的对比噪声比(CNR)、病灶的CER,并计算增强前后病灶与白质、病灶与灰质、病灶与脑脊液的CR和CNR。比较增强前后病灶在两序列图像上的显著性、病灶边界的显示及与瘤周水肿的区分、脑膜尾征的显示。计数并比较两序列上脑转移瘤的数目。结果:T1WIR上显示的最低强化浓度为0.0016mmol/L,而T1WSE显示强化的最低浓度为0.00078mmol/L。T1WIR上在2mmol/L时达峰值,而T1WSE则在3mmol/L时达峰值,当对比剂浓度在0.1～3mmol/L之间时,T1WIR上CER高于T1WSE,而此浓度范围之外则呈相反的表现;而对比剂与脑白质、对比剂与脑灰质的CR则均以T1WSE上为高。全部患者中,T1WIR上灰质与白质的CR和CNR均明显高于T1WSE。在第①组原发性脑肿瘤中,增强前后肿瘤在T1WIR的SNR分别为75.4±14.3和192.8±45.9,明显高于T1WSE上的48.7±8.9和133.4±41.5(P<0.01);肿瘤的CER在T1WIR上为164.2±63.4,低于T1WSE上的174.7±68.5(P<0.01);增强前T1WIR上肿瘤与白质、肿瘤与灰质及肿瘤与脑脊液的3种CR均高于T1WSE;增强后肿瘤与白质、肿瘤与灰质的CR则为T1WSE上高于T1WIR,而肿瘤与脑脊液的CR则在T1WIR上更高。增强前后肿瘤与白质、肿瘤与灰质及肿瘤与脑脊液的CNR均以T1WIR上更高。平扫时,67.4%(62/92例)原发性脑肿瘤在T1WIR上更显著,28.3%(26/92例)两序列上显著性相同,4.3%(4/92例)在T1WSE上更显著。增强后,93.5%(86/92例)肿瘤在两序列上显著性相似,6.5%(6/92例)肿瘤在增强T1WSE上更显著。在边界的显示中,增强前46.7%(43/92例)的肿瘤T1WIR优于T1WSE,51.1%(47/92例)在两序列相似,2.2%(2/92例)在T1WSE优于T1WIR;增强后17.4%(16/92例)在T1WSE优于T1WIR,81.5%(75/92例)在两序列相似,1.1%(1/92例)在T1WIR优于T1WSE。20例伴瘤周水肿者,肿瘤与瘤周水肿的区分,平扫时,65%(13/20例)在两序列上相同,35%(7/20例)在T1WIR优于T1WSE;增强后,75%(15/20例)在两序列上相同,25%(5/20例)在T1WIR上优于T1WSE。在脑膜尾征的显示中,60%(9/15例)在两序列增强图像上显示相似,40%(6/15例)在增强T1WSE上更明显。92例原发性脑肿瘤在增强T1WIR和增强T1WSE上的平均体积分别为26.3±23.6 cm3和26.3±23.4cm3,两者间无显著统计学差异(P=0.959)。在第②组31例患者中增强前后T1WIR分别发现94和236个转移灶,而增强前后T1WSE则明显多于前者,分别发现162和347个转移灶。T1WIR上增强前后转移瘤的SNR均高于T1WSE(P<0.001);两序列上转移瘤的CER无差异(P=0.273)。增强前T1WIR上3种CR和CNR均高于T1WSE;增强后,肿瘤与白质、肿瘤与灰质的CR及肿瘤与白质的CNR在T1WSE上为高,而肿瘤与脑脊液的CR和CNR及肿瘤与灰质的CNR在T1WIR上更高。T1WSE和T1WIR上肿瘤的体积平均为4.9±6.7cm3和4.8±6.7 cm3,两者间无显著差异(P=0.635)。在第③组24例脑膜炎中,增强T1WIR和增强T1WSE对结核性脑膜炎、化脓性脑膜炎和囊虫性脑膜炎中的阳性率均为100%,但在病毒性脑膜炎的阳性率则分别为35.3%(6/17例)和58.8%(10/17例)。在13例两增强序列均显示异常脑膜强化的脑膜炎中,30.8%(4/13例)在两序列上显著性相同,69.2%(9/13例)在增强T1WSE上更显著。在第④组49例病变中,平扫时,81.6%(40/49例)的病灶在T1WIR的显示优于T1WSE或与其相同,而T1WSE仅在8.2%(4/49例)的病灶显示上更具优势,10.2%(5/49例)的病灶在两序列上各具优势。按病灶在T1WSE上的信号分析:明显低信号的病灶在两序列平扫图像上的显著性相同;96.7%(29/30例)的低信号病灶在T1WIR上更显著或与T1WSE相同;高信号病灶则在T1WSE上更显著或与T1WIR相似;高低混杂信号的病灶中,75%(6/8例)高信号出血在T1WSE上显著,87.5%(7/8例)低信号灶在T1WIR上更显著。1例脑实质型脑囊虫的头节在T1WSE上更显著。两序列上显示强化的病例中,75%(15/20例)在两增强序列上显著性相同,3例烟雾病的“常春藤征”和1例脑囊虫在增强T1WSE上更显著,且增强T1WSE显示了更多的囊虫病灶,1例静脉畸形在增强T1WSE上可见畸形血管强化,而增强T1WIR则未显示强化。结论:T1WSE对低浓度对比剂更敏感,具有更高的对比剂溶液与脑灰、白质的CR;平扫T1WIR在原发性脑肿瘤的显示中优于T1WSE或与其相似,但增强后T1WSE则优于T1WIR或与其相似;在脑转移瘤的诊断中增强前后T1WSE均优于T1WIR;在脑膜炎,尤其是病毒性脑膜炎,T1WSE优于T1WIR;在其他病变的显示上,T1WIR更有利于低信号病灶的显示,而T1WSE则在显示高信号出血和异常小血管的强化上更具有价值。更多还原

【Abstract】 Objective:To determine the selection sequence of T1-weighted imaging in central nervous system disease by comparing results of spin echo (T1WSE) and inversion recovery (T1WIR).Methods:Gadopentetate dimeglumine (Gd-DTPA) was diluted with deionized water in glass tubes, the concentration of solution was ranged from 0.025 to 5 mmol/L. The solutions were imaged with T1WIR and T1WSE imaging, and signal intensities were measured with a region of interest (ROI) analysis of solutions, white matte (WM) and gray matter (GW) of patients. The solution-to-WM contrast ratio (CR) and solution-to-GW CR were calculated. A phantom in which Gd-DTPA was 1:1 diluted from 0.025 to 0.000024 mmol/L was developed to determine the lowest concentration at which the effects of Gd-DTPA were evident on T1WIR and T1WSE images in vitro. 196 patients referred for imaging of the brain were divided into four groups: A group contained 92 patients with primary brain tumors, B group contained 31 patients with brain metastases, C group contained 24 patients with meningitis, and D group contains 49 patients with various diseases which not contained in the others groups. All patients were underwent axial T1WSE and T1WIR imaging before Gd-DTPA injection. A to C groups and 24 patients in D group were performed for contrast enhancement with single dose Gd-DTPA, and T1WIR and T1WSE were used alternately as the first post-enhanced sequence. Signal intensities were measured with a region of interest (ROI) analysis of the tumor, WM, GM, cerebrospinal fluid (CSF) and tumor on two sequences images before and after contrast medium injection. The SD of noise was measured. The data were used to calculate WM-to-GW CR and contrast-to-noise ratio (CNR), contrast-to-enhancement ratio (CER) and signal-to-noise ratio (SNR) of tumors, CR and CNR of tumor-to-WM, tumor-to-GW and tumor-to-CSF. The tumor volumes were measured on two sequences post-contrast images. T1WSE and T1WIR images were compared for number of brain metastases, conspicuity and boundary of lesions, the definition of tumor from edema, and dural tail sign of meningioma.Results:The phantom test revealed that T1WIR showed a threshold contrast signal at 0.0016 mmol/L as compared with T1WSE at 0.00078 mmol/L. The signal of solution was at peak on T1WIR image with 2mmol/L, but on T1WSE with 3mmol/L. The CER of solution was higher on T1WIR images than on T1WSE images when concentration was ranged from 0.1 to 3 mmol/L. However, when concentration was out of that, the converse was correct. The solution-to-WM and solution-to-GW CR was higher on T1WSE images compared to T1WIR images when concentration ranged from 0.025 to 5 mmol/L. In all of patients, the CR and CNR of WM-to-GM were higher on T1WIR images than on T1WSE images.In A group, the SNR of tumors were 75.4±14.3 and 192.8±45.9 on pre- and post-enhanced T1WIR images,which were higher than 48.7±8.9 and 133.4±41.5 on pre- and post-enhanced T1WSE images (P<0.01), respectively. However, the CER of tumors was lower on T1WIR images than on T1WSE images (164.2±63.4 vs 174.7±68.5). Prior to enhancement, all of tumor-to-background CRs on T1WIR images were higher than on T1WSE images. Following contrast enhancement, CRs of tumor-to-WM and tumor-to-GM were higher on T1WSE images, while tumor-to-CSF CR was higher on T1WIR images. All of tumor-to-background CNRs were higher on T1WIR images before and after contrast medium injection. Pre-enhanced T1WIR images showed superior conspicuity in 62 primary brain tumors (67.4%), equal conspicuity in 26 cases (28.3%), and inferior conspicuity in 4 cases (4.3%). Post-enhanced T1WIR images showed equal conspicuity in 86 cases (93.5%), and inferior conspicuity in 6 cases (6.5%). In delineation of tumor boundaries, pre-enhanced T1WIR images were superior in 43 cases (46.7%), equal in 47 cases (51.1%) and inferior in 2 cases (2.2%); post-enhanced T1WIR images were superior in 1 case (1.1%), equal in 75 cases (81.5%) and inferior in 16 cases (17.4%). In 20 cases with edema, the definition of tumor from edema, pre-enhanced T1WIR images were superior in 7 cases (35%) and equal in 13 cases (65%), post-enhanced T1WIR images were superior in 5 cases (25%) and equal in 15 cases (75%). In manifestation of dural tail sign of meningioma, post-enhanced T1WIR images were equal in 9 cases (60%), and inferior in 6 cases (40%). The volume of primary brain tumor was 26.3 cm3±23.6 and 26.3 cm3±23.4 on post-enhanced T1WIR and T1WSE images, respectively. There had no difference between two sequences.In B group, pre-enhanced T1WIR and T1WSE images discovered 94 and 162 lesions, respectively; post-enhanced T1WIR and T1WSE images discovered 236 and 347 lesions, respectively. The SNR of tumors was higher on T1WIR than on T1WSE images before and after contrast medium injection, while the CER of lesions had no difference between two sequences. Before enhancement, all of CRs and CNRs of tumor-to-background were higher on T1WIR images. After enhancement, CRs of tumor-to-WM and tumor-to-GM, and CNR of tumor-to-WM were higher on T1WSE images, while CR of tumor-to-CSF, and CNRs of tumor-to-GM and tumor-to-CSF were higher on T1WIR images. The calculated mean tumor volume had no different between post-enhanced T1WIR and T1WSE images (4.9 cm±6.7 vs 4.8 cm3±6.7).In C group, both post-enhanced T1WIR and T1WSE images were positive in all of tuberculosis, purulent and cysticercal meningitis cases. In all of 17 cases with lymphocytic meningitis, post-enhanced T1WIR images were positive in 6 cases (35.3%), while post-enhanced T1WSE images were positive in 10 cases (58.8%). In 13 subjects who were positive on both sequences post-enhanced images, post-enhanced T1WIR images were equal in 4 cases (30.8%) and inferior in 9 cases (69.2%).In D group, pre-enhanced T1WIR were superior in 17 cases (34.7%), equal in 23 cases (46.9%), and inferior in 4 cases (8.2%); in 5 cases(10.2%), each sequence had partial superiority. According to lesions signal intensity on T1WSE images, both sequences showed equal conspicuity in obvious hypo-intensity signal lesions; T1WIR images showed superior or equal conspicuity in 29 hypo-intensity signal lesions (96.7%); T1WSE images showed superior or equal conspicuity in hyper-intensity lesions; in 8 mingle signal lesions, T1WIR images showed superior conspicuity in 7 hypo-intensity signal lesions and equal conspicuity in 1 hypo-intensity signal lesion, while T1WSE images showed superior conspicuity in 6 hyper-intensity signal hemorrhage lesions and equal conspicuity in 2 hyper-intensity signal hemorrhage lesions. T1WSE images showed superior conspicuity in scolex of 1 brain cysticercosis case. In 20 cases with enhancement on post-enhanced T1WIR and/or T1WSE images, post-enhanced T1WIR images showed equal conspicuity in 15 cases (75%); post-enhanced T1WIR images showed inferior conspicuity in“ivy sign”of 3 Moyamoya disease and 1 brain cysticercosis case; and 1 venous malformation was clearly displayed on post-enhanced T1WSE images, but not on post-enhanced T1WIR images.Conclusion: T1WSE images are more sensitive to lowere concentration Gd-DTPA than T1WSE images do, and have higher solution-to-WM and solution-to-GW CR. In the detection of primary brain tumors, pre-enhanced T1WIR imaging is superior or equal to pre-enhanced T1WSE imaging, while post-enhanced T1WSE imaging is superior or equal to post-enhanced T1WIR imaging. In the detection of brain metastases, T1WIR imaging is inferior to T1WSE imaging before and after contrast medium injection. In revealing meningitis, especially lymphocytic meningitis, post-enhanced T1WIR imaging is inferior to post-enhanced T1WSE imaging. In the detection of the others lesions, T1WIR imaging is superior in revealing hypo-intensity signal lesions, while T1WSE imaging is superior in revealing hyper-intensity signal hemorrhage and abnormal small vascular enhancement.更多还原