Nöth Ulrike, Hattingen Elke, Bähr Oliver, Tichy Julia, Deichmann Ralf
Brain Imaging Center, Goethe University Frankfurt, Frankfurt/Main, Germany.
Department of Neuroradiology, Goethe University Frankfurt, Frankfurt/Main, Germany.
NMR Biomed. 2015 Jul;28(7):818-30. doi: 10.1002/nbm.3324. Epub 2015 May 11.
Conventional MRI for brain tumor diagnosis employs T2 -weighted and contrast-enhanced T1 -weighted sequences. Non-enhanced T1 -weighted images provide improved anatomical details for precise tumor location, but reduced tumor-to-background contrast as elevated T1 and proton density (PD) values in tumor tissue affect the signal inversely. Radiofrequency (RF) coil inhomogeneities may further mask tumor and edema outlines. To overcome this problem, the aims of this work were to employ quantitative MRI techniques to create purely T1 -weighted synthetic anatomies which can be expected to yield improved tissue and tumor-to-background contrasts, to compare the quality of conventional and synthetic anatomies, and to investigate optical contrast and visibility of brain tumors and edema in synthetic anatomies. Conventional magnetization-prepared rapid acquisition of gradient echoes (MP-RAGE) anatomies and maps of T1 , PD and RF coil profiles were acquired in comparable and clinically feasible times. Three synthetic MP-RAGE anatomies (PD T1 weighting both with and without RF bias; pure T1 weighting) were calculated for healthy subjects and 32 patients with brain tumors. In healthy subjects, the PD T1 -weighted synthetic anatomies with RF bias precisely matched the conventional anatomies, yielding high signal-to-noise (SNR) and contrast-to-noise (CNR) ratios. Pure T1 weighting yielded lower SNR, but high CNR, because of increased optical contrasts. In patients with brain tumors, synthetic anatomies with pure T1 weighting yielded significant increases in optical contrast and improved visibility of tumor and edema in comparison with anatomies reflecting conventional T1 contrasts. In summary, the optimized purely T1 -weighted synthetic anatomy with an isotropic resolution of 1 mm, as proposed in this work, considerably enhances optical contrast and visibility of brain tumors and edema.
用于脑肿瘤诊断的传统磁共振成像（MRI）采用T2加权和对比增强T1加权序列。非增强T1加权图像能提供更清晰的解剖细节以精确定位肿瘤，但肿瘤与背景的对比度会降低，因为肿瘤组织中升高的T1和质子密度（PD）值会对信号产生反向影响。射频（RF）线圈的不均匀性可能会进一步掩盖肿瘤和水肿的轮廓。为克服这一问题，本研究的目的是采用定量MRI技术创建纯T1加权的合成解剖图像，预期其能提高组织以及肿瘤与背景的对比度，比较传统解剖图像和合成解剖图像的质量，并研究合成解剖图像中脑肿瘤和水肿的光学对比度及可视性。在可比且临床可行的时间内获取了传统的磁化准备快速梯度回波（MP-RAGE）解剖图像以及T1、PD和RF线圈剖面图。为健康受试者和32例脑肿瘤患者计算了三种合成MP-RAGE解剖图像（有和无RF偏差的PD T1加权；纯T1加权）。在健康受试者中，有RF偏差的PD T1加权合成解剖图像与传统解剖图像精确匹配，产生了高信噪比（SNR）和对比噪声比（CNR）。纯T1加权产生的SNR较低，但CNR较高，这是因为光学对比度增加。在脑肿瘤患者中，与反映传统T1对比度的解剖图像相比，纯T1加权的合成解剖图像在光学对比度上有显著提高，肿瘤和水肿的可视性也得到改善。总之，如本研究中所提出的，具有1毫米各向同性分辨率的优化纯T1加权合成解剖图像显著增强了脑肿瘤和水肿的光学对比度及可视性。
